Integrative study of subcellular distribution, chemical forms, and physiological responses for understanding cadmium tolerance in two garden shrubs

Integrative study of subcellular distribution, chemical forms, and physiological responses for understanding cadmium tolerance in two garden shrubs | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Integrative study of subcellular distribution, chemical forms, and physiological responses for understanding cadmium tolerance in two garden shrubs Shiyin Yu, Shan Wang, Min Tang, Shuzhen Pan, Meixian Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5311541/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background and aims Urban ornamental shrubs have significant potential for restoring cadmium (Cd)-contaminated soil. Simulated pot pollution was applied to Buxus sinica and Ligustrum × vicaryi to study their Cd enrichment characteristics and tolerance mechanisms. Methods Cd content and accumulation were analyzed in different plant organs, subcellular distribution and chemical forms of Cd in the roots, and the effects of Cd on the ultrastructure of root cells under various Cd concentrations (0, 25, 50, 100, and 200 mg·kg⁻¹). Results (1) With increasing Cd treatment levels, the total biomass of B. sinica gradually decreased, while L. × vicaryi exhibited a stimulation effect at low Cd concentrations and inhibition at high Cd concentrations. (2) The Cd content in different organs of both shrubs increased with rising Cd levels, with L. × vicaryi showing a significantly higher increase than B. sinica, indicating a stronger Cd accumulation capability in L. × vicaryi . (3) Cd in the root of both shrubs was primarily present in NaCl-extractable forms, and was majorly bound to the cell wall. (4) Excessive Cd caused damage to the cellular structure of B. sinica leaves, while the cells of L. × vicaryi leaves maintained normal morphology. (5) In both shrubs, Cd primarily binds to the cell wall through hydroxyl, amino functional groups, and soluble sugars. Conclusion Converting Cd to less active forms, immobilizing Cd in the cell wall, and providing binding sites through functional groups may be crucial resistance mechanisms for both shrubs in response to Cd stress. Cadium Buxus sinica Ligustrum × vicaryi Physiological changes Subcellular distribution Chemical form Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Industrial activities, transportation emissions, and substantial construction waste associated with urban development have significantly increased the heavy metal content of soils in urban areas, leading to environmental pollution (Capuana 2020 ). Cadmium (Cd) is one of the most widely distributed heavy metals and is known for its high toxicity and mobility (Ali et al. 2014 ; Kong et al. 2020 ). Research on heavy metal pollution in urban soils in China indicates that Cd contamination levels exceed the background values for urban soils, making it a heavy metal pollutant that requires focused management (He et al. 2023 ; Pan et al. 2018 ; Tong et al. 2020 ). Cd is a typical non-essential mineral element that can harm photosynthesis and metabolic activities in plants when it accumulates excessively. Furthermore, Cd can easily enter animals and humans through the food chain, posing a significant risk to human health (Guo et al. 2015 ; Zhao et al. 2019 ). Therefore, it is crucial to implement active remediation measures for Cd-contaminated soil to maintain a stable ecosystem. Physical and chemical methods for remediating heavy metal-contaminated soil have limitations, such as high costs and the potential for secondary pollution. Phytoremediation technology is a green, in-situ remediation approach that utilizes plants to extract or stabilize heavy metals in the soil, offering favorable economic and ecological benefits along with promising application prospects (Ali et al. 2013 ; Zeng et al. 2018 ). Currently, research on the phytoremediation of Cd primarily focuses on herbs such as Sedum alfredii (Li et al. 2015 ), Thlaspi caerulescens (Zhao et al. 2003 ), and Solanum nigrum (Wei et al. 2005 ). However, herbs face challenges for large-scale engineering applications due to low biomass production and prolonged remediation times. In contrast, woody plants possess larger biomass and well-developed root systems, enhancing the exchange of heavy metal ions between soil and roots, thereby effectively absorbing heavy metal pollutants. Consequently, woody plants have become a research hotspot in phytoremediation in recent years (Capuana 2011 ). Based on the distribution and accumulation characteristics of Cd in woody plants, these species serve different phytoremediation purposes. For example, Salix spp. (Yang et al. 2020 ), Morus alba (Zeng et al. 2020 ), Koelreuteria bipinnata (Luo et al. 2015 ), and Lonicera japonica (Liu et al. 2009 ) primarily assimilate Cd in their roots, making them ideal tree species for Cd phytostabilization. Populus spp. (He et al. 2013 ), Koelreuteria paniculata (Yang et al. 2018 ) and Eucalyptus spp. (Iori et al. 2017 ) exhibit strong adaptability to Cd stress, showcasing great potential for restoring Cd-contaminated soil. Existing studies primarily conduct pot or hydroponic experiments with saplings, while there is a lack of research focusing on commonly used urban ornamental shrubs that have high aesthetic value and broad applicability. B. sinica and L. × vicaryi are common shrubs found in urban green spaces, characterized by their strong stress resistance, wide adaptability, and ease of transplantation and survival. Studies have shown that both shrubs can accumulate Cd in urban environments and have potential for remediating Cd-contaminated soil (Chen et al. 2022 ; Zeng et al. 2018 ; Zhang et al. 2022 ). However, research on the mechanisms of Cd accumulation and tolerance in these two shrubs still needs to be conducted. Therefore, this experiment selected B. sinica and L. × vicaryi as subjects for pot pollution simulation experiments. It investigated their physiological indices, Cd content, and accumulation characteristics in different plant organs, as well as the subcellular distribution, chemical form, ultrastructure, and cell wall functional groups of Cd in the roots under various Cd treatments. The aim is to analyze the enrichment characteristics and tolerance mechanisms of both shrubs under Cd stress, providing a theoretical basis for their effective application in remediating Cd-contaminated soil. Materials and methods Plant material The 4-year-old saplings of B. sinica and L. × vicaryi used in the experiment were purchased from a nursery stock base in Shunyi District, Beijing, China. The experimental soil was a mixture of peat soil and perlite (v/v, 8:2), with its basic physicochemical properties and background values of heavy metals shown in Table 1 . Based on the Cd content of soil in Beijing (Jia et al. 2023 ) and the range of content adapted by plants in preliminary tests, this experiment established five levels of Cd contamination treatments: 0 (CK), 25 (T 1 ), 50 (T 2 ), 100 (T 3 ), and 200 mg·kg − 1 (T 4 ). Table 1 Basic physical and chemical properties and heavy metal background value of soil pH Organic matter/ g·kg − 1 Total N/ g·kg − 1 Alkali-hydrolyzable N/ g·kg − 1 Total P/ mg·kg − 1 Available P/ mg·kg − 1 Total K/ mg·kg − 1 Olsen-K/ mg·kg − 1 Cd mg·kg − 1 7.55 329.2 11.28 1.75 556 4.93 3274 57.32 0.21 Experimental design In early March, 5 kg of mixed soil was added to each 3-gallon plastic pot (24 cm in diameter, 26.5 cm deep), with trays placed underneath the pots to prevent heavy metal loss and environmental pollution. According to the predetermined gradients, analytical-grade CdCl 2 ·2.5H 2 O powder was weighed and dissolved in deionized water. Subsequently, an aerosol sprayer was used to ensure that the heavy metal solution uniformly penetrated the soil, guaranteeing an even mixture of the drug and soil. After that, the contaminated soil was placed in a cool location to equilibrate for one month, and three parallel groups were processed for each Cd concentration treatment. In early April, saplings with similar height, crown width, and root length were selected for transplantation into the pots, with one plant per pot. Deionized water was regularly sprayed in consistent amounts during subsequent growth to maintain the soil moisture content at 60–70% of field holding capacity. In early September, samples were collected using the complete harvest method. Measurement Methods The harvested plants were thoroughly rinsed with tap water three times. Subsequently, the plant roots were dipped in 20 mmol·L − 1 Na 2 -EDTA for 20 minutes to eliminate surface-absorbed cadmium (Cd). Afterward, the plants were rinsed three times with deionized water, dried, and then divided into leaf, stem, and root tissues, which were later used for the determination of various studied parameters. Some plant samples were dried in an oven at 105°C for 30 minutes, followed by further drying at 70°C until a constant dry weight was achieved, allowing for the determination of plant dry weight and Cd content. The final samples were stored after being finely ground using a pulverizer. Other plant samples were preserved in a − 80°C refrigerator (Meng et al. 2024 ). After grinding, 1 g of each root, branch, and leaf sample was digested using the HNO 3 -H 2 O 2 method. Following complete digestion, the samples were filtered and brought to a constant volume of 50 mL. The Cd content in the plant tissues was measured using inductively coupled plasma emission spectrometry (ICP-OES, Agilent 5110) (Konieczynski et al. 2020 ). Additionally, 0.5 g of fresh leaf samples was soaked in 10 mL of 96% ethanol in the dark for 24 hours to measure chlorophyll a, b, and carotenoid contents, as described by Chen et al. ( 2022 ) Cell membrane permeability was assessed using the electrical conductivity method, following Kaya et al. ( 2009 ). Different chemical forms of Cd in the plants were sequentially extracted using differential centrifugation and chemical reagents, according to the method of Zou et al. ( 2023 ). Differential centrifugation was employed to separate the subcellular distribution of Cd, as outlined by Wang et al. ( 2012 ). The ultrastructure of plant cells was observed using transmission electron microscopy, following the method of Jiang et al. ( 2007 ). The plant cell walls of the roots were extracted using the method described by Riaz et al. ( 2018 ), elucidating the information on chemical functional groups in the plant cell walls under Cd stress through Fourier transform infrared spectroscopy measurements. Statistical analysis All data obtained were statistically analyzed using Excel 2010 and presented as mean ± standard deviation (S.D.). One-way analysis of variance (ANOVA) was performed on the data using SPSS 26.0, followed by Duncan's test at p < 0.05. Graphical representations were created using Origin 2021. The bioconcentration factor (BCF) in the plant was calculated as BF = Cd content in plant tissues (mg·kg − 1 )/Cd content in the soil (mg·kg − 1 ). This factor reflects the ability of the plant to assimilate and transfer Cd from the soil to its tissues (Uddin et al. 2020 ). The translocation factor (TF) of Cd in the plant was calculated as TF = Cd content in shoots (mg·kg − 1 )/Cd content in roots (mg·kg − 1 ), which is used to evaluate the plant's capability to transport Cd from the roots to the shoots (Zakaria et al. 2021 ). Results Plant growth To study the effect of exogenously applied Cd on plant growth, the biomass of B. sinica and L. × vicaryi was analyzed. Results indicated that the total biomass of B. sinica gradually decreased as the Cd treatment gradient increased, while that of L. × vicaryi showed a pattern of promotion at low Cd concentrations and inhibition at high Cd concentrations. Under different Cd treatment gradients, the leaf biomass of B. sinica was not affected compared to the control. However, the biomass of the branches and roots of B. sinica decreased gradually with increasing Cd treatment gradients, with minimum values of 26.80 g and 29.46 g, respectively, representing reductions of 31.89% and 62.69% under T2 and T4 treatments compared with the control ( P < 0.05). Likewise, the biomass of leaves and branches in L. × vicaryi showed no notable change under Cd stress, whereas root biomass exhibited an initial increase followed by a decrease as Cd concentrations increased. As shown in Table 1, the reduction in root biomass was smallest (32.71 g) at T3 treatment, significantly reduced by 27.05% compared to the control ( P < 0.05; Table 1). Table 1 Biomass of two shrubs treated with different Cd treatments (g) Shrub Treatment Leaf Branch Root Total Buxus sinica CK 44.87±8.92a 39.35±7.01a 78.97±8.56a 163.19±21.48a T 1 49.50±4.67a 38.11±4.91a 68.07±12.23ab 155.67±16.32ab T 2 38.18±8.27a 26.80±5.43b 54.20±9.11b 119.18±19.75c T 3 38.65±2.55a 32.09±4.49ab 54.81±11.48b 125.54±16.58bc T 4 39.84±7.33a 28.04±2.72b 29.46±6.97c 102.09±19.00c Ligustrum × vicaryi CK 40.90±2.78a 42.51±4.36a 44.84±4.52ab 128.26±9.48ab T 1 42.11±4.73a 43.77±4.01a 46.63±4.38a 132.50±9.59a T 2 41.87±5.46a 42.92±4.13a 53.17±10.60a 137.96±11.76a T 3 39.35±3.84a 42.40±1.45a 32.71±1.32c 114.46±1.09b T 4 36.67±3.82a 41.48±2.24a 35.44±3.79bc 113.58±9.26b Note: Values are presented as mean ± S.D. Values with different letters within the same column indicate significant differences at the P < 0.05 level between concentrations according to Duncan test. Leaf pigment content With the increase of the Cd treatment gradient, the chlorophyll a and carotenoid contents in the leaves of B. sinica displayed a decreasing trend, peaking at T4 treatment (0.58 mg·g⁻¹) and reaching the lowest at T3 treatment (0.16 mg·g⁻¹), both of which were significantly different from the control ( P < 0.05). Additionally, the chlorophyll b content of B. sinica initially decreased and then increased with the increasing Cd treatment gradient, reaching its minimum at T1 treatment and maximum at T4 treatment, both noticeably lower compared to the control ( P < 0.05). The chlorophyll a content of L. × vicaryi showed a tendency to increase and then decrease with increasing Cd treatment gradients, reaching a maximum value of 0.78 mg·g⁻¹ at T2 treatment, but there was no significant difference compared with the control. Similarly, the chlorophyll b and carotenoid contents were unaffected by Cd exposure compared to the control ( P > 0.05; Fig. 1). Fig. 1 Changes in the leaf pigment content of two shrubs with different Cd treatments. Data points and error bars represent mean and S.D., respectively. Different letters within the same pattern indicate statistically significant differences at P < 0.05 according to Duncan test. Cell membrane permeability Low to medium concentrations of cadmium (Cd) had a beneficial effect on the cell membrane permeability of B. sinica branches, which gradually decreased as the Cd concentration increased to high levels. The membrane permeability of B. sinica branches was highest in the T4 treatment, being 1.33-fold greater than that of the control ( P <0.05). The root membrane permeability of B. sinica also gradually increased with rising Cd content, peaking in the T4 treatment, with significant differences compared to the control ( P <0.05). However, there was no significant difference in the membrane permeability of B. sinica leaves compared to the control under different Cd treatments. In contrast, the membrane permeability of the leaves did not significantly differ from the control across various treatment gradients. The membrane permeability of L. × vicaryi leaves increased with increasing Cd content. In the T1-T4 Cd treatments, it was 1.01- to 1.57-fold higher than that of the control. However, Cd treatment did not significantly impact the cell membrane permeability of L. × vicaryi branches and roots (Fig. 2). Fig. 2 Changes in cell membrane permeability of two shrubs at different Cd concentrations. Data points and error bars represent mean and S.D., respectively. Different letters within the same pattern indicate statistically significant differences at P < 0.05 according to Duncan test. Cd content in various tissues The Cd content in various tissues of B. sinica and L. × vicaryi significantly increased with the Cd treatment gradient, peaking at the T4 treatment with notable differences compared to the control ( P <0.05). Generally, the Cd content in the roots of B. sinica and L. × vicaryi was significantly higher than that in the leaves and branches within the same treatment gradient, being 117.68-fold and 38.30-fold higher than that of the leaves, and 133.90-fold and 32.73-fold higher than that of the branches, respectively. Moreover, exogenous Cd application could noticeably further increase the Cd content in various tissues of L. × vicaryi compared to B. sinica as the Cd content increased. As shown in Table 2, the Cd content in the leaves, branches, and roots of L. × vicaryi was 19.01 times, 9.42 times, and 2.01 times higher than that of B. sinica , respectively (Table 2). Table 2 Cd concentration in tissues of two shrubs at different Cd concentration treatments Shrub Treatment Leaf Branch Root Buxus sinica CK 0.14±0.04b 0.20±0.04d 0.57±0.13c T 1 0.25±0.09b 0.41±0.08cd 16.29±4.57c T 2 0.68±0.16a 0.66±0.06b 63.64±12.55b T 3 0.70±0.18a 0.50±0.17bc 66.95±12.81b T 4 0.82±0.16a 1.71±0.21a 96.50±7.87a Ligustrum×vicaryi CK 0.14±0.04d 0.12±0.03d 0.76±0.05e T 1 0.94±0.06d 1.10±0.13d 36.00±3.07d T 2 2.93±0.19c 5.24±0.76c 74.01±10.70c T 3 9.74±0.39b 9.32±0.21b 158.23±21.58b T 4 15.59±2.05a 16.11±2.69a 202.73±31.42a Note: Values are presented as mean ± S.D. Values with different letters within the same column indicate significant differences at P < 0.05 level between concentrations according to Duncan test. Cd bioconcentration factors and translocation factor Under Cd treatment, the bioconcentration factor (BCF) of the aerial parts of both shrubs was less than 1, with no significant differences among the various treatment gradients. After the application of exogenous Cd, the BCF values of the roots of both shrubs increased at low Cd levels, gradually decreasing as the Cd concentration rose to high levels, with the lowest BCF values observed in the T4 treatment. Furthermore, the BCF values of the roots of L. × vicaryi were consistently greater than 1, while those of B. sinica exceeded 1.0 only in the T2 treatment. By calculating the translocation factor (TF) of Cd, it was found that the TF values of B. sinica and L. × vicaryi were both significantly less than 1, ranging from 0.01 to 0.32 and 0.03 to 0.17, respectively. Additionally, after increasing exogenous Cd treatment, the TF of L. × vicaryi was higher than that of B. sinica under the same Cd treatment (Table 3). Table 3 Cd enrichment coefficients in tissues of two shrubs at different Cd concentrations Shrub Treatment BCF TF Leaf Branch Root Buxus sinica CK 0.67±0.19a 0.95±0.04a 2.70±0.60a 0.32±0.11a T 1 0.01±0.00b 0.02±0.27b 0.65±0.18c 0.02±0.04b T 2 0.01±0.00b 0.02±0.00b 1.27±0.25b 0.02±0.00b T 3 0.01±0.00b 0.01±0.00b 0.67±0.13c 0.01±0.00b T 4 0.00±0.00b 0.01±0.00b 0.48±0.04c 0.01±0.00b Ligustrum×vicaryi CK 0.68±0.17a 0.59±0.12a 3.63±0.23a 0.17±0.03a T 1 0.04±0.00b 0.04±0.01b 1.44±0.12b 0.03±0.00b T 2 0.06±0.00b 0.10±0.02b 1.48±0.21b 0.06±0.00b T 3 0.10±0.00b 0.09±0.00b 1.58±0.22b 0.06±0.01b T 4 0.08±0.01b 0.08±0.01b 1.01±0.16c 0.08±0.23b Note: Values are presented as mean ± S.D. Values with different letters within the same column indicate significant differences at the P < 0.05 level between concentrations according to Duncan test. Chemical forms According to our analyses, the chemical form of Cd extracted by NaCl was dominant in the roots of B. sinica (19.21% to 69.45%) and L. × vicaryi (21.02% to 69.87%). The distribution ratio of NaCl-extractable Cd in the roots of these two shrubs increased with exogenous Cd application and peaked at the T4 treatment ( P <0.05). In B. sinica roots, Cd extracted by HAc, which is less mobile and toxic, increased when Cd content was low and then decreased as the exogenous Cd treatment content increased. However, the distribution ratios of the more mobile and toxic Cd E and Cd W tended to decrease with enhanced Cd levels. In contrast, the proportions of CdE and Cd W in L. × vicaryi roots did not change significantly with increasing Cd treatment gradient, while the proportions of other chemical forms of Cd showed a decreasing trend. Overall, the dominant chemical form of Cd in the roots of both shrubs was moderately active (Fig. 3). Fig. 3 Distribution ratio of Zn chemical forms in roots of two shrubs. Cd E , nitrate, chloride based inorganic salts and amino acids, etc. Cd W , water soluble organic acid salts, heavy metal phosphates [M(H 2 PO 4 ) 2 ], etc.; Cd NaCl , pectinates, heavy metals in the bound or adsorbed state of proteins, etc.; Cd HAc , insoluble metallic phosphates; Cd HCl , oxalic acid salt etc.; Cd R , residual form. Subcellular distribution Under Cd treatment, the proportion of Cd in the roots of B. sinica and L. × vicaryi primarily accumulated in the cellular debris fractions, accounting for 54.95% to 72.95% and 30.50% to 60.70%, respectively. The proportion of Cd in the cellular debris fraction of B. sinica increased with the addition of Cd to the soil and peaked at the T4 treatment ( P <0.05). Nevertheless, the percentages of Cd in the organelle component and heat-sensitive protein fractions gradually decreased with increasing Cd concentration in the soil. As the Cd treatment gradient increased, the subcellular distribution of Cd in L. × vicaryi showed a remarkable increase in heat-stabilized proteins, while opposite trends were observed in metal-enriched particles and heat-sensitive protein fractions. Moreover, the proportion of Cd in L. × vicaryi 's cellular debris fractions increased when the Cd level was low and gradually reduced as the Cd concentration increased to higher levels (Fig. 4). Fig. 4 Proportion of Zn in subcellular distribution of roots of two shrubs. F1, Metal-enriched particles; F2, Cellular debris；F3, Organelle components; F4, Heat-sensitive protein; F5, Heat stabilized protein. Ultrastructure of root cells In this study, control (CK), low content (T2), and high content (T4) groups were selected to further observe the microscopic changes in root cell morphology and the distribution of Cd in the cells under Cd treatment using transmission electron microscopy (TEM). Fig. 5a,b showed that, under low concentration Cd treatment, there was an increase in the intercellular gap compared with CK in B. sinica , along with obvious black deposits in the cells. When Cd content was high, the cell arrangement in B. sinica was disrupted, cells were significantly deformed, and a large amount of black deposits accumulated on the cell walls and in the vacuoles. Similarly, for L. × vicaryi , there was a substantial aggregation of black deposits within the cells, predominantly near the cell walls, vacuoles, and cell plasmodesmata under low Cd treatment. At high levels of Cd, some Ligustrum vicaryi cells disintegrated, and cell walls ruptured, with black deposits accumulating near the cell walls and cell plasmodesmata. Fig. 5 Ultrastructure of root cells of two shrubs at different Cd concentration treatments. (a) Buxus sinica. (b) Ligustrum×vicaryi. co, cortex; pe, pericycle; ph, phloem; ca, cambium; xy, xylem; SG, starch grain; CW, Cell wall; CP, cell plasmodesmata; V, vacuole; M, mitochondria; BM, black matter. Fourier transform infrared spectroscopy of root cell wall The Fourier transform infrared spectroscopy (FTIR) spectra of B. sinica and L. × vicaryi were analyzed in the control (CK), low concentration (T2), and high concentration (T4) groups to determine the changes in functional groups of the cell wall in plant roots under Cd stress (Fig. 6a,b, Table 5). The ratio A/A 2927 represents the absorbance of the characteristic peak of methyl (-CH3) relative to that of the characteristic peak, which can be used for semi-quantitative analysis of the functional groups involved in heavy metal binding based on changes in the ratio. The study showed that the cell walls of B. sinica and L. × vicaryi roots contain abundant functional groups, especially oxygen-containing functional groups. Under Cd treatment, the absorption peaks with the largest shifts in the cell walls of Buxus roots were the stretching vibration peaks of hydroxyl/amino and cellulose carbohydrate rings, which shifted 12 cm to lower frequencies and 8 cm to higher frequencies under low Cd treatment, and 8 cm to lower frequencies and 6 cm to higher frequencies under high Cd treatment, respectively. In the cell walls of L. × vicaryi roots, significant shifts were observed in the stretching vibration peaks of hydroxyl/amino, carboxyl, and cellulose glycan carbohydrate rings under Cd treatment, resulting in shifts of 6, 5, and 4 cm to higher frequencies at T4 treatment, respectively. Additionally, the A/A 2927 values of the hydroxyl/amino and cellulose glycan stretching vibration absorption peaks in the cell walls of L. × vicaryi roots decreased with increasing Cd treatment, while the A/A 2927 values of the carboxyl characteristic peaks in the treatment groups were higher than those in the control. Fig. 6 Infrared spectrum characterization of root cell walls of two shrubs with different Cd concentration treatments. (a) Buxus sinica . (b) Ligustrum×vicaryi. Table 5 Analysis of infrared spectrum characteristic peaks in the root cell walls of two shrubs under different Cd concentration treatments Species Number Function group Wavenum-ber/cm -1 CK Cd-T 2 Cd-T 4 A/A 29-27 A/A 29-27 Offset/cm -1 cm -1 A/A 29--27 Offse-t/cm -1 cm -1 Buxus sinica 1 hydroxyl/amino (-OH/-NH) 3400 1.43 1.47 -12 1.37 -8 2 Methyl (-CH 3 ) 2927 1.00 1.00 0 1.00 0 3 Amide(I) (-C=O) 1644 1.13 1.20 1 1.14 2 4 Amide(Ⅱ) (-N-H) 1515 0.87 0.82 1 0.85 1 5 Carbon-Hydrogen(C-H)or Carbon-Oxygen (C-O) 1429 0.94 0.91 1 0.93 2 6 alcoholic hydroxyl C-O 1315 0.86 0.79 0 0.84 0 7 Sulfate ester (C-O-S) or carboxyl (C-O) or phosphoric acid (C-O-P) 1264 0.92 0.84 -1 0.88 -1 8 cellulose glycan bending (-C-H) or (-C-C, -C-O) 1042 1.27 1.28 8 1.26 6 Ligustrum × vicaryi Ligustrum × vicaryi Ligustrum×vicaryium×vicaryi 1 hydroxyl/amino (-OH/-NH) 3400 1.71 1.62 4 1.60 6 2 Methyl (-CH 3 ) 2927 1.00 1.00 0 1.00 0 3 Amide(I) (-C=O) 1644 1.11 1.15 -2 1.17 -1 4 Amide(Ⅱ) (-N-H) 1515 0.74 0.83 1 0.82 0 5 Carbon-Hydrogen (C-H) or Carbon-Oxygen (C-O) 1429 0.91 0.95 -1 0.94 -3 6 Carboxyl (-COOH) or Amide(Ⅲ) (-C-N) 1377 0.88 0.93 3 0.92 5 7 alcoholic hydroxyl (C-O) 1315 0.86 0.91 -2 0.90 0 8 Sulfate ester (C-O-S) or carboxyl (C-O) or phosphoric acid C-O-P 1264 0.93 0.98 0 0.95 -1 9 cellulose glycan bending (-C-H) or (-C-C, -C-O) 1042 1.60 1.47 2 1.42 4 Discussion Tolerance characteristics of two shrubs under Cd stress Plant growth characteristics and physiological metabolism are crucial evaluation indicators for assessing plant tolerance to heavy metal toxicity. Cd is a non-essential element for plant growth; however, excessive Cd can inhibit plant development, damage cellular structures, and impair functional activity, leading to irreversible effects on the plant (Wang et al. 2020 ). In this study, Cd exhibited a strong toxic effect on B. sinica . As the levels of Cd treatment increased, the biomass of B. sinica gradually decreased. Additionally, the results indicated that lower concentrations of Cd (25, 50 mg·kg⁻¹) promoted biomass accumulation in L. × vicaryi , while higher concentrations of Cd (100, 200 mg·kg⁻¹) inhibited plant growth to some extent. This suggests that L. × vicaryi has a stronger tolerance to Cd-contaminated soil compared to B. sinica . Similar responses were observed in other plants under Cd stress. The biomass accumulation of Sphagneticola calendulacea showed no significant effect at lower concentrations of 25 mg·kg⁻¹; however, higher Cd treatment (≥ 100 mg·kg⁻¹) notably inhibited plant growth (Lu et al. 2020 ). In L. × vicaryi ,, biomass production significantly increased when Cd concentrations were low (≤ 100 mg·kg⁻¹), but there was a sharp decline under higher Cd treatment (≥ 25 mg·kg − 1 ) (Jia et al. 2015 ). These studies suggest that different plants have varying adaptation ranges to Cd content, and appropriate levels of Cd can promote plant growth to a certain extent, potentially playing a positive role in Cd accumulation. Photosynthesis is a crucial process by which plants convert energy from their environment, and the levels of photosynthetic pigments reflect the efficiency of this process. Chlorophyll a, chlorophyll b, and carotenoids are the primary components of photosynthetic pigments. Studies have shown that Cd stress can reduce the activity of chlorophyll synthase and activate enzymes involved in chlorophyll degradation, leading to a decrease in the synthesis and content of photosynthetic pigments, manifesting as leaf yellowing (Zhang et al. 2020 ). Additionally, since Cd is a non-essential element for plants, it can bind with thiol groups in proteins, damaging the structure and functional activity of chloroplasts (Cherif et al. 2012 ). In this study, it was observed that the contents of chlorophyll a and carotenoids in B. sinica exhibited an overall declining trend with increasing Cd treatment levels, and similar trends were seen in chlorophyll a, chlorophyll b, and carotenoids of L. × vicaryi . Similarly, Dutta et al. ( 2024 )reported a reduction in chlorophyll a, chlorophyll b, and carotenoid contents in the leaves of Arachis hypogaea with higher exogenous Cd levels. Furthermore, this study revealed that low Cd content initially inhibited chlorophyll b content in B. sinica , but higher levels promoted it. The same trend was observed in Davidia involucrata , where chlorophyll b levels initially decreased under lower Cd treatment but increased with higher Cd concentrations (Yang et al. 2020 ). This phenomenon suggests that plants may enhance their tolerance to Cd by increasing their chlorophyll content (Dezhban et al. 2015 ). The cell membrane is a crucial structure that regulates and controls the transport and exchange of substances across cells. Under normal conditions, the cell membrane exhibits selective permeability. However, when plants are stressed by heavy metals, the permeability of the cell membrane increases, leading to the leakage of intracellular components and the entry of external substances, resulting in physiological dysfunction (Wei et al. 2014 ). Changes in plasma membrane permeability are assessed by the conductivity of plant cell extracts, which serves as an indicator of plant responses to heavy metal pollution. Under Cd stress, the relative conductivity during the tillering and ripening stages of rice significantly exceeded that of the control, indicating increased plasma membrane permeability and severe membrane damage (Huang et al. 2018 ). Similarly, in the present study, the relative conductivity of cell plasma membranes in various tissues of B. sinica and the leaves of L. × vicaryi increased with higher Cd content, suggesting that the permeability of cell plasma membranes in both shrubs progressively increased, leading to greater intracellular substance leakage. This phenomenon may be attributed to Cd stress causing alterations in the composition of plasma membrane lipid fatty acids and enhanced oxidative processes, which result in increased permeability and reduced membrane stability (Spiridonova et al. 2019 ). Analysis of tolerance characteristics of two shrubs under Cd stress Root retention or translocation to the aerial parts of plants plays a pivotal role in their tolerance to heavy metals in the soil (Shen et al. 2021 ). In this study, the Cd content in various tissues of B. sinica and L. × vicaryi significantly increased with higher Cd concentrations. Furthermore, most of the Cd absorbed was retained in the roots, suggesting that both shrubs can limit the translocation of Cd to the aerial parts, consistent with previous studies on species such as Impatiens walleriana (Lai 2015 ), Morus spp . (Huang et al. 2018 ), and Boehmeria nivea (Wang et al. 2008 ), which primarily accumulate Cd in their roots, with accumulation levels increasing alongside Cd concentration. Therefore, the accumulation of heavy metals in the roots is one of the key mechanisms for tolerating heavy metal stress. The excessive accumulation of Cd in the roots may be due to the role of inner cortex cells in the root tissue, which serve as lateral interceptors, limiting the transfer of Cd to the aerial parts and thereby mitigating Cd toxicity and its impacts on physiological metabolism in plants (Akhter et al. 2014 ). BCF and TF are two key parameters used to evaluate heavy metal accumulation efficiency in plants (Wu et al. 2011 ). In this study, the BCF values of the aerial tissues of B. sinica and L. × vicaryi were relatively low. However, the BCF values of the roots of L. × vicaryi were consistently higher than 1 when treated with different concentrations of Cd, while those of the roots of B. sinica exceeded 1 only under T2 treatment. Additionally, BCF values of the roots of both shrubs decreased with increasing Cd concentration. Furthermore, the TF values of both shrubs under Cd treatment were less than 1, which was significantly lower than those in the control group. This phenomenon suggests that Cd stress reduced the ability of the plants to absorb and translocate Cd to the aerial parts. Plants with BCFs and TFs greater than 1 are usually considered suitable for phytoextraction, whereas those with high BCF (> 1) and low TF (< 1) are considered suitable for phytostabilization (Hou et al. 2020 ). In the present study, the roots of both shrubs exhibited higher BCF and lower TF values, indicating their efficient ability to restrict Cd translocation to the aerial parts, thus positioning them as potential woody plants for stabilizing Cd-contaminated soil. This finding aligns with results from other studies, where the BCF values of Calendula calypso were greater than 1 under each Cd treatment, while TF values were less than 1, making it suitable for the stabilization of Cd-contaminated soil (Farooq et al. 2020 ). Similarly, the BCF values of the roots and stems of Euryops pectinatus exceeded 1 under Cd stress, while TF values remained lower than 1, reflecting its relatively higher Cd accumulation capacity, thereby protecting the aerial parts from Cd toxicity (Jia et al. 2023 ). Analysis of accumulation mechanisms of two shrubs under Cd stress Heavy metals absorbed and transported by plants in various chemical forms are present in different tissues (Liu et al. 2019 ). The toxicity and mobility of Cd are closely associated with its chemical forms. Consequently, research has focused on extracting different chemical forms of Cd using various extractants, revealing that the lower the polarity of the chemical forms, the stronger their migration ability and greater their toxicity. The migration ability of Cd in ethanol- and water-extractable fractions is higher than in other forms, and these forms exhibit greater toxicity to organisms (Zheng et al. 2023 ). In the roots of Landoltia punctata , the NaCl-extracted state, which has moderate toxicity and mobility, was the predominant form of Cd (30.15–88.66%). Additionally, the proportion and concentration of HCl- and HAc-extracted Cd increased with rising Cd concentration (Wang et al. 2021 ). A similar characteristic has been observed in the roots of oilseed rape (Ru et al. 2006 ) and Solanum nigrum (Li et al. 2020 ), where the proportion of NaCl-extractable Cd was the highest. The results of this study align with previous research, indicating that in the roots of B. sinica and L. × vicaryi , most of the Cd was primarily in the NaCl-extractable form, with the proportion of NaCl-extracted Cd notably increasing with higher Cd content. According to Wu et al. ( 2016 ), NaCl extraction mainly comprised pectate and protein-integrated Cd, which may form complexes with organic groups on the root cell wall, resulting in reduced toxicity. Furthermore, a larger proportion of Cd in the NaCl-extracted state may alleviate Cd toxicity, allowing it to occupy a relatively high proportion in plants. It was also found that as exogenous Cd content increased, the proportion of chemical forms with high mobility and toxicity decreased in the roots of these two shrubs. These findings are consistent with studies on Agrocybe aegerita , which converted Cd into undissolved pectate and protein-bound forms when subjected to Cd stress to reduce Cd toxicity (Li et al. 2019 ). Similarly, in the leaves of Salix matsudana , the proportion of HCl- and HAc-extracted Cd in the roots increased with rising Cd concentration ( Zou et al.(2023). Overall, these results suggest that plants may tolerate heavy metals by converting Cd into less toxic chemical forms, with the dominant forms and their proportions varying among different plant species. The mode of heavy metal subcellular distribution in plants is a crucial factor in determining the extent of metal toxicity and the plant tolerance mechanism. Previous research has shown that plants can regionalize heavy metals in relatively inactive areas, such as cell walls and soluble fractions, to reduce their toxicity (Ma et al. 2023 ). In this study, Cd in the roots of B. sinica and L. × vicaryi was primarily accumulated in the cell walls (54.95%-72.95% and 30.50%-60.70%, respectively). These findings are consistent with studies on Kandelia obovata (Weng et al. 2012 ), Salix matsudana (Wu et al. 2017 ), and Miscanthus sacchariflorus (Xin et al. 2018 ), which also reported a high proportion of Cd predominantly stored in the cell walls. The cell wall serves as the first barrier for cells to mitigate Cd damage, as its surface can fix heavy metal ions and limit their access to the plasma membrane and cytoplasm, thereby alleviating Cd toxicity (Loix et al. 2017 ; Yu et al. 2020 ). Additionally, increasing the thickness of the cell wall to fix heavy metals plays a critical role in Cd retention in woody plants (Li et al. 2023 ). Furthermore, in the current study, the proportion of heat-sensitive proteins in L. × vicaryi increased with higher Cd content, indicating that these components may also have a mitigating effect under Cd stress. Overall, the subcellular distribution results demonstrate that retaining Cd in the cell walls of roots may play a significant role in the Cd detoxification mechanism of these two shrubs. To understand the mechanisms of cadmium (Cd) detoxification, it is essential to explore the internal structural changes of cells through ultrastructural observation. In the current study, a significant accumulation of dark deposits was observed on the cell walls of the roots of both shrub species under Cd stress. This finding aligns with previous research, which reported visible Cd deposits in the cell walls of Dittrichia viscosa after 10 days of treatment with 15 mg·kg − 1 Cd, with a marked increase corresponding to higher Cd concentrations and prolonged exposure (Fernández et al. 2014 ). Furthermore, electron-dense precipitates were identified in vacuoles and on the cell walls of the roots of cotton and Juncus effusus at high Cd concentrations (1000 µM) (Daud et al. 2013 ; Najeeb et al. 2011 ). Cd stress can adversely affect plant cellular structures and impair physiological metabolic functions. For instance, the morphology of root cells in Sesuvium portulacastrum exhibited deformation with increasing Cd treatment concentrations, including cell wall breakdown, cell membrane protrusions, vacuole contraction, mitochondrial and nuclear disassembly, and an increase in the number of starch granules (Uddin et al. 2023 ). Similar ultrastructural alterations were observed in the root cells of two shrub species under high Cd stress (200 mg·kg − 1 ) in this study. The cell structure of B. sinica was severely altered under high Cd stress, with noticeable fracturing in cell arrangement. In contrast, the ultrastructural integrity of L. × vicaryi was less compromised, suggesting a stronger tolerance to Cd-contaminated soil. The binding and transformation of Cd in plants primarily occur within the cell walls, which are composed mainly of pectin, cellulose, hemicellulose, and proteins. Pectin and hemicellulose provide functional groups such as hydroxyl, carboxyl, amino, and aldehyde groups, which can adsorb and immobilize positively charged heavy metal ions, thereby limiting their entry into the plasma membrane (Lai 2015 ; Yu et al. 2021 ). Analysis of the changes in characteristic peaks in FTIR spectra revealed that the cell wall of B. sinica enhanced its adsorption capabilities for Cd ions by regulating the content of hydroxyl and amino functional groups, as well as soluble sugars. Additionally, in L. × vicaryi , the presence of hydroxyl, amino, and carboxyl functional groups, along with soluble sugars in the cell walls, played a pivotal role in mitigating Cd toxicity. This finding corroborates previous studies suggesting that hydroxyl, amino, cyano, and carboxyl functional groups in cell walls can bind to Cd, contributing to tolerance against Cd in castor seedlings (He et al. 2020 ). Hydroxyl, amino, and carboxyl functional groups have also been shown to be crucial for the tolerance and accumulation of Cd in the cell walls of Solanum nigrum (Jia et al. 2019 ; Wang et al. 2021 ). Furthermore, hydroxyl, carboxyl, and amide groups may serve as the primary binding sites for Cd in the cell walls of Conyza canadensis seedlings (Yu et al. 2020 ). Thus, the ability of B. sinica and L. × vicaryi to accumulate and tolerate Cd may be linked to the compartmentalization of plants, the adjustment of their chemical forms and subcellular distribution under stress, and the immobilization of Cd on the cell wall through functional groups. Conclusion From the current study, we concluded that Cd stress inhibited the growth of B. sinica , while it promoted growth at low Cd concentrations and inhibited it at high Cd concentrations in L. × vicaryi . However, neither of the plants died under various Cd treatments. Additionally, considerable dark deposits were observed in the vacuoles as well as attached to the cell walls of the roots of both shrubs following Cd treatment. The cell structure of B. sinica was severely altered under high Cd stress compared to that of L. × vicaryi . Observations of plant biomass and cellular microstructure indicated that L. × vicaryi exhibited stronger resistance to Cd-contaminated soil than B. sinica . The content of chlorophyll a and carotenoids in the leaves of B. sinica decreased with increasing Cd concentrations, while the content of chlorophyll b initially decreased and then increased as the Cd treatment gradient increased, showing significant differences compared to the control. In contrast, there were no remarkable differences in the chlorophyll a, chlorophyll b, and carotenoid content in the leaves of L. × vicaryi compared with the control. The plasma membrane permeability of various tissues in B. sinica increased with higher Cd treatment gradients, whereas that of L. × vicaryi noticeably increased compared to the control only in the leaves. These results indicated that the photosynthetic pigments and plasma membrane permeability of all tissues in B. sinica are more sensitive to Cd stress. The Cd content in various organs of both shrubs increased with rising Cd treatment concentrations, with the highest levels found in the roots. In the roots of both shrubs, the NaCl-extracted state, which has moderate toxicity and mobility, was the predominant form of Cd, and the proportion and concentration of less toxic chemical forms increased with rising Cd concentrations. Moreover, both shrubs primarily accumulated Cd in the cell debris fraction of their roots, suggesting that they convert Cd to a less active form and retain it in the cell walls to mitigate its toxicity. FTIR spectroscopy revealed that certain functional groups, such as hydroxyl and amino groups, were involved in binding with Cd in the cell walls of both shrubs. Additionally, the results suggested that the two shrubs can absorb Cd through various functional groups to alleviate Cd toxicity. Declarations Competing interest The authors have no relevant fnancial or non-fnancial interests to disclose. Acknowledgements This work was supported by the National Natural Science Foundation of China (31600574); Beijing Joint Construction Project; Beijing Forestry University to Build a World-Class Discipline and Guide the Development Special Fund (2019XKJS0322); Scientific Research and Postgraduate Training Joint Research Project of Beijing Education Commission (2019GJ-03). The authors thank all those who provided helpful suggestions and critical comments on this manuscript. Author Contributions Shiyin Yu, Shan Wang, Min Tang and Meixian Wang designed this research and revised the manuscript critically; Shan Wang, Shuzhen Pan, Min Tang and Meixian Wang conducted feld work and laboratory analysis; Shiyin Yu, Min Tang and Meixian Wang carried out the data analysis and drafted the manuscript. All authors read and approved the final manuscript. Data Availability The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. References Akhter MF, Omelon CR, Gordon RA, Moser D, Macfie SM (2014) Localization and chemical speciation of cadmium in the roots of barley and lettuce. Environ Exp Bot 100:10–19 Ali B, Qian P, Jin R, Ali S, Khan M, Aziz R, Tian T, Zhou W (2014) Physiological and ultra-structural changes in Brassica napus seedlings induced by cadmium stress. Biol Plant 581:131–138 Ali H, Khan E, Sajad MA (2013) Phytoremediation of heavy metals-Concepts and applications. Chemosphere 917:869–881 Capuana M (2011) Heavy metals and woody plants - biotechnologies for phytoremediation. iForest - Biogeosciences Forestry 41:7–15 Capuana M (2020) A review of the performance of woody and herbaceous ornamental plants for phytoremediation in urban areas. iForest - Biogeosciences Forestry 132:139–151 Chen H, Xia DS, Wang B, Liu H, Ma XY (2022) Pollution monitoring using the leaf-deposited particulates and magnetism of the leaves of 23 plant species in a semi-arid city, Northwest China. Environ Sci Pollut Res Int 2923:34898–34911 Chen XJ, Tao HF, Wu YZ, Xu XM (2022) Effects of cadmium on metabolism of photosynthetic pigment and photosynthetic system in Lactuca sativa L. revealed by physiological and proteomics analysis. Sci Hort 305:111371 Cherif J, Derbel N, Nakkach M, von Bergmann H, Jemal F, Ben Lakhdar Z (2012) Spectroscopic studies of photosynthetic responses of tomato plants to the interaction of zinc and cadmium toxicity. J Photochem Photobiology B: Biology 111:9–16 Daud MK, Ali S, Variath MT, Zhu SJ (2013) Differential physiological, ultramorphological and metabolic responses of cotton cultivars under cadmium stress. Chemosphere 9310:2593–2602 Dezhban A, Shirvany A, Attarod P, Delshad M, Matinizadeh M, Khoshnevis M (2015) Cadmium and lead effects on chlorophyll fluorescence, chlorophyll pigments and proline of Robinia pseudoacacia . J Forestry Res 262:323–329 Dutta D, Pal AK, Gunri SK (2024) A Physiological Approach to Study the Interaction of Cadmium and Zinc in Groundnut ( Arachis hypogaea L.) Seedlings. Legume Res 473:404–409 Farooq A, Nadeem M, Abbas G, Shabbir A, Khalid MS, Javeed HMR, Saeed MF, Akram A, Younis A, Akhtar G (2020) Cadmium partitioning, physiological and oxidative stress responses in marigold (Calendula calypso) grown on contaminated soil: implications for phytoremediation. Bull Environ Contam Toxicol 1052:270–276 Fernández R, Fernández-Fuego D, Bertrand A, González A (2014) Strategies for Cd accumulation in Dittrichia viscosa (L.) Greuter: Role of the cell wall, non-protein thiols and organic acids. Plant Physiol Biochem 78:63–70 Guo HB, Zhu N, Deyholos MK, Liu J, Zhang XR, Dong JE (2015) Calcium mobilization in salicylic acid-induced salvia miltiorrhiza cell cultures and its effect on the accumulation of rosmarinic acid. Appl Biochem Biotechnol 1755:2689–2702 He CQ, Zhao YP, Wang FF, Oh K, Zhao ZZ, Wu CL, Zhang XY, Chen XP, Liu XY (2020) Phytoremediation of soil heavy metals (Cd and Zn) by castor seedlings: Tolerance, accumulation and subcellular distribution. Chemosphere 252 He JL, Ma CF, Ma YL, Li H, Kang JQ, Liu TX, Polle A, Peng CH, Luo ZB (2013) Cadmium tolerance in six poplar species. Environ Sci Pollut Res 201:163–174 He Y, Peng C, Zhang Y, Guo Z, Xiao X, Kong L (2023) Comparison of heavy metals in urban soil and dust in cities of China: characteristics and health risks. Int J Environ Sci Technol 202:2247–2258 Hou XC, Teng WJ, Hu YX, Yang ZC, Li C, Scullion J, Guo Q, Zheng RL (2020) Potential phytoremediation of soil cadmium and zinc By diverse ornamental and energy grasses. BioResources 151:616–640 Huang F, Wen XH, Cai YX, Cai KZ (2018) Silicon-mediated enhancement of heavy metal tolerance in rice at different growth stages. Int J Environ Res Public Health 1510:2193–2193 Huang RZ, Jiang YB, Jia CH, Jiang SM, Yan XP (2018) Subcellular distribution and chemical forms of cadmium in Morus alba L. Int J Phytoremediation 205:448–453 Iori V, Pietrini F, Bianconi D, Mughini G, Massacci A, Zacchini M (2017) Analysis of biometric, physiological, and biochemical traits to evaluate the cadmium phytoremediation ability of eucalypt plants under hydroponics. iForest - Biogeosciences Forestry 101:416–421 Jia HL, Wang XH, Wei T, Zhou R, Muhammad H, Hua L, Ren XH, Guo J, Ding YZ (2019) Accumulation and fixation of Cd by tomato cell wall pectin under Cd stress. Environ Exp Bot 167:103829 Jia L, Liu ZL, Chen W, Ye Y, Yu S, He XY (2015) Hormesis effects induced by cadmium on growth and photosynthetic performance in a hyperaccumulator, Lonicera japonica Thunb. J Plant Growth Regul 341:13–21 Jia XY, Xia TX, Liang J, Li YD, Zhu XY, Zhang D, Wang JS (2023) Source apportionment of heavy metals based on multiple approaches for a proposed subway line in the southeast industrial district of Beijing, China. Int J Environ Res Public Health 201:683 Jia YX, Yue PX, Li KH, Xie YH, Li T, Pu YL, Xu XX, Wang GY, Zhang SR, Li Y, Luo X (2023) Mechanisms of cadmium tolerance and detoxification in two ornamental plants. Agronomy-Basel 138:2039 Jiang HM, Yang JC, Zhang JF (2007) Effects of external phosphorus on the cell ultrastructure and the chlorophyll content of maize under cadmium and zinc stress. Environ Pollut 1473:750–756 Kaya C, Tuna AL, Sonmez O, Ince F, Higgs D (2009) Mitigation effects of silicon on maize plants grown at high zinc. J Plant Nutr 3210:1788–1798 Kong XS, Zhao YX, Tian K, He XB, Jia YY, He ZH, Wang WW, Xiang CG, Tian XJ (2020) Insight into nitrogen and phosphorus enrichment on cadmium phytoextraction of hydroponically grown Salix matsudana Koidz cuttings. Environ Sci Pollut Res 278:8406–8417 Konieczynski P, Zarkov A, Viapiana A, Kaszuba M, Bielski L, Wesolowski M (2020) Investigations of metallic elements and phenolics in Chinese medicinal plants. Open Chem 181:1381–1390 Lai HY (2015) Subcellular distribution and chemical forms of cadmium in Impatiens walleriana in relation to its phytoextraction potential. Chemosphere 138:370–376 Li S, Lu S, Wang J, Chen ZC, Zhang Y, Duan J, Liu P, Wang XY, Guo JK (2023) Responses of Physiological, Morphological and Anatomical Traits to Abiotic Stress in Woody Plants. Forests 149:1784 Li TQ, Tao Q, Shohag MJI, Yang XE, Sparks DL, Liang YC (2015) Root cell wall polysaccharides are involved in cadmium hyperaccumulation in Sedum alfredii . Plant Soil 3891–2:387–399 Li XD, Ma H, Li LL, Gao YF, Li YZ, Xu H (2019) Subcellular distribution, chemical forms and physiological responses involved in cadmium tolerance and detoxification in Agrocybe Aegerita . Ecotoxicol Environ Saf 171:66–74 Li XX, Cui XW, Zhang X, Liu W, Cui ZJ (2020) Combined toxicity and detoxification of lead, cadmium and arsenic in Solanum nigrum L. J Hazard Mater 389121874 Liu SL, Ali S, Yang RJ, Tao JJ, Ren B (2019) A newly discovered Cd-hyperaccumulator Lantana camara L. J Hazard Mater 371:233–242 Liu ZL, He XY, Chen W, Yuan FH, Yan K, Tao DL (2009) Accumulation and tolerance characteristics of cadmium in a potential hyperaccumulator- Lonicera japonica Thunb. J Hazard Mater 1691–3:170–175 Loix C, Huybrechts M, Vangronsveld J, Gielen M, Keunen E, Cuypers A (2017) Reciprocal interactions between cadmium-induced cell wall responses and oxidative stress in plants. Front Plant Sci 8:1867–1867 Lu RR, Hu ZH, Zhang QL, Li YQ, Lin M, Wang XL, Wu XN, Yang JT, Zhang LQ, Jing YX, Peng CL (2020) The effect of Funneliformis mosseae on the plant growth, Cd translocation and accumulation in the new Cd-hyperaccumulator Sphagneticola calendulacea . Ecotoxicol Environ Saf 203:110988 Luo ZH, Tian DL, Ning C, Yan WD, Xiang WH, Peng CH (2015) Roles of Koelreuteria bipinnata as a suitable accumulator tree species in remediating Mn, Zn, Pb, and Cd pollution on Mn mining wastelands in southern China. Environ Earth Sci 745:4549–4559 Ma P, Zang J, Shao TY, Jiang QR, Li YQ, Zhang W, Liu MD (2023) Cadmium distribution and transformation in leaf cells involved in detoxification and tolerance in barley. Ecotoxicol Environ Saf 249:114391 Meng QH, Fan WH, Liu FW, Wang GL, Di XY (2024) Effect of Phosphorus Application on Subcellular Distribution and Chemical Morphology of Cadmium in Eggplant Seedlings under Cadmium Stress. Agronomy-Basel 145:932 Najeeb U, Jilani G, Ali S, Sarwar M, Xu L, Zhou WJ (2011) Insights into cadmium induced physiological and ultra-structural disorders in juncus effusus L. and its remediation through exogenous citric acid. J Hazard Mater 1861:565–574 Pan LB, Wang Y, Ma J, Hu Y, Su BY, Fang GL, Wang L, Xiang B (2018) A review of heavy metal pollution levels and health risk assessment of urban soils in Chinese cities. Environ Sci Pollut Res 252:1055–1069 Riaz M, Yan L, Wu XW, Hussain S, Aziz O, Wang YH, Imran M, Jiang CC (2018) Boron alleviates the aluminum toxicity in trifoliate orange by regulating antioxidant defense system and reducing root cell injury. J Environ Manage 208:149–158 Ru SH, Xing JP, Su DC (2006) Rhizosphere cadmium speciation and mechanisms of cadmium tolerance in different oilseed rape species. J Plant Nutr 295:921–932 Shen C, Fu HL, Liao Q, Huang BF, Huang YY, Xin JL (2021) Selection for low-cadmium cultivars and cadmium subcellular distribution comparison between two selected cultivars of eggplant ( Solanum melongena L). Environ Sci Pollut Res Int 2841:57739–57750 Spiridonova E, Ozolina N, Nesterkina I, Gurina V, Nurminsky V, Donskaya L, Tretyakova A (2019) Effect of cadmium on the roots of beetroot ( Beta vulgaris L). Int J Phytoremediation 2110:980–984 Tong SM, Li HR, Wang L, Tudi M, Yang LS (2020) Concentration, Spatial Distribution, Contamination Degree and Human Health Risk Assessment of Heavy Metals in Urban Soils across China between 2003 and 2019-A Systematic Review. Int J Environ Res Public Health 179:3099 Uddin MM, Chen ZF, Huang LF (2020) Cadmium accumulation, subcellular distribution and chemical fractionation in hydroponically grown Sesuvium portulacastrum [Aizoaceae]. PLoS ONE 1512:e0244085–e0244085 Uddin MM, Chen ZF, Xu FL, Huang LF (2023) Physiological and cellular ultrastructural responses of Sesuvium portulacastrum under Cd stress grown hydroponically. Plants-Basel 1219:3381 Wang CR, Rong H, Zhang XB, Shi WJ, Hong X, Liu WC, Cao T, Yu XX, Yu QF (2020) Effects and mechanisms of foliar application of silicon and selenium composite sols on diminishing cadmium and lead translocation and affiliated physiological and biochemical responses in hybrid rice ( Oryza sativa L.) exposed to cadmium and lead. Chemosphere 251:126347 Wang JC, Chen XF, Chu SH, Hayat K, Chi YW, Zhi YE, Zhang D, Zhou P (2021) Influence of Cd toxicity on subcellular distribution, chemical forms, and physiological responses of cell wall components towards short-term Cd stress in Solanum nigrum . Environ Sci Pollut Res 2811:13955–13969 Wang X, Liu YO, Zeng GM, Chai LY, Song XC, Min ZY, Xiao X (2008) Subcellular distribution and chemical forms of cadmium in Bechmeria nivea (L.) Gaud. Environ Exp Bot 623:389–395 Wang XL, Zhang BJ, Wu DS, Hu L, Huang T, Gao GQ, Huang S, Wu S (2021) Chemical forms governing Cd tolerance and detoxification in duckweed ( Landoltia punctata ). Ecotoxicol Environ Saf 207:111553 Wang YP, Huang J, Gao YZ (2012) Arbuscular mycorrhizal colonization alters subcellular distribution and chemical forms of cadmium in Medicago sativa L. and resists cadmium toxicity. PLoS ONE 711:e48669 Wei SH, Zeng XF, Wang SS, Zhu JG, Ji DD, Li YM, Jiao HJ (2014) Hyperaccumulative property of Solanum nigrum L. to Cd explored from cell membrane permeability, subcellular distribution, and chemical form. J Soils Sediments 143:558–566 Wei SH, Zhou QX, Wang X, Zhang KS, Guo GL, Ma QYL (2005) A newly-discovered Cd-hyperaccumulator Solanum nigrum L. Chin Sci Bull 501:33–38 Weng BS, Xie XY, Weiss DJ, Liu JC, Lu HL, Yan CL (2012) Kandelia obovata (S., L.) Yong tolerance mechanisms to cadmium: subcellular distribution, chemical forms and thiol pools. Marine Pollution Bulletin 6411: 2453–2460 Wu HF, Wang JY, Li BB, Ou YJ, Wang JR, Shi QY, Jiang WS, Liu DH, Zou JH (2016) Salix matsudana Koidz tolerance mechanisms to cadmium: uptake and accumulation, subcellular distribution, and chemical forms. Pol J Environ Stud 254:1739–1747 Wu HF, Wang JY, Ou YJ, Li BB, Jiang WS, Liu DH, Zou JH (2017) Characterisation of early responses to cadmium in roots of Salix matsudana Koidz. Toxicol Environ Chem 995–6:913–925 Wu QH, Wang SZ, Thangavel P, Li QF, Zheng H, Bai J, Qiu RL (2011) Phytostabilization potential of Jatropha Curcas L. in polymetallic acid mine tailings. Int J Phytoremediation 138:788–804 Xin JP, Zhang Y, Tian RN (2018) Tolerance mechanism of Triarrhena saccharifiora (Maxim.) Nakai. seedlings to lead and cadmium: Translocation, subcellular distribution, chemical forms and variations in leaf ultrastructure. Ecotoxicology and Environmental Safety 165: 611–621 Yang LP, Zhu J, Wang P, Zeng J, Tan R, Yang YZ, Liu ZM (2018) Effect of Cd on growth, physiological response, Cd subcellular distribution and chemical forms of Koelreuteria paniculata . Ecotoxicol Environ Saf 160:10–18 Yang WD, Wang YY, Liu D, Hussain B, Ding ZL, Zhao FL, Yang XO (2020) Interactions between cadmium and zinc in uptake, accumulation and bioavailability for Salix integra with respect to phytoremediation. Int J Phytoremediation 226:628–637 Yang Y, Zhang LQ, Huang X, Zhou YY, Quan QM, Li YX, Zhu XH (2020) Response of photosynthesis to different concentrations of heavy metals in Davidia involucrata . PLoS ONE 153:e0228563 Yu HY, Guo JY, Li Q, Zhang XZ, Huang HG, Huang F, Yang AQ, Li TX (2020) Characteristics of cadmium immobilization in the cell wall of root in a cadmium-safe rice line ( Oryza sativa L). Chemosphere 241:125095 Yu HY, Yang AQ, Wang KJ, Li Q, Ye DH, Huang HG, Zhang XZ, Wang YD, Zheng ZC, Li TX (2021) The role of polysaccharides functional groups in cadmium binding in root cell wall of a cadmium-safe rice line. Ecotoxicol Environ Saf 226112818 Yu SH, Sheng L, Mao HP, Huang XS, Luo LS, Li YY (2020) Physiological response of Conyza Canadensis to cadmium stress monitored by Fourier transform infrared spectroscopy and cadmium accumulation. Spectrochim Acta Part A Mol Biomol Spectrosc 229C:118007 Zakaria Z, Zulkafflee NS, Redzuan NAM, Selamat J, Ismail MR, Praveena SM, Tóth G, Razis AFA (2021) Understanding potential heavy metal contamination, absorption, translocation and accumulation in rice and human health risks. Plants-Basel 106:1070 Zeng P, Guo ZH, Cao X, Xiao XY, Liu YA, Shi L (2018) Phytostabilization potential of ornamental plants grown in soil contaminated with cadmium. Int J Phytoremediation 204:311–320 Zeng P, Guo ZH, Xiao XY, Cao X, Peng C (2018) Response to cadmium and phytostabilization potential of Platycladus orientalis in contaminated soil. Int J Phytoremediation 2013:1337–1345 Zeng P, Guo ZH, Xiao XY, Peng C, Liu LQ, Yan DM, He YL (2020) Physiological stress responses, mineral element uptake and phytoremediation potential of Morus alba L. in cadmium-contaminated soil. Ecotoxicol Environ Saf 189:109973 Zhang JH, Guan YJ, Lin Q, Wang YX, Wu BW, Liu X, Wang B, Xia DS (2022) Spatiotemporal differences and ecological risk assessment of heavy metal pollution of roadside plant leaves in Baoji city. China Sustain 1410:5809 Zhang W, Zhao YL, Xu ZG, Huang HM, Zhou JK, Yang GY (2020) Morphological and physiological changes of Broussonetia papyrifera seedlings in cadmium contaminated soil. Plants-Basel 912:1698–1698 Zhao FJ, Lombi E, McGrath SP (2003) Assessing the potential for zinc and cadmium phytoremediation with the hyperaccumulator Thlaspi caerulescens . Plant Soil 2491:37–43 Zhao HX, Wang LS, Zhao FJ, Wu LH, Liu AN, Xu WZ (2019) SpHMA1 is a chloroplast cadmium exporter protecting photochemical reactions in the Cd hyperaccumulator Sedum plumbizincicola . Plant Cell Environ 424:1112–1124 Zheng MM, Feng D, Liu HJ, Yang GL (2023) Subcellular distribution, chemical forms of cadmium and rhizosphere microbial community in the process of cadmium hyperaccumulation in duckweed. Sci Total Environ 8592:160389 Zou JH, Wang YR, Wang SY, Shang XS (2023) Ca alleviated Cd-induced toxicity in Salix matsudana by affecting Cd absorption, translocation, subcellular distribution, and chemical forms. J Plant Physiol 281:153926 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5311541","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":369825244,"identity":"b5eb5a75-ef6e-4528-b5ad-86a9e7aa92cd","order_by":0,"name":"Shiyin Yu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAsklEQVRIiWNgGAWjYJCCA0Asx8befoA0LcZ8PGcSSLMpcZ6EgwFxSg1upD88XNh2J71NgiGB4UfFNmK05Bgcntn2LLdNuvEAY8+Z20RpYTjM23Y4t03mQAIzYxtRWtIfgLSks0kkGBCrJcEApCWBeC2SZ94YHOY5d9iwDRjIB4nyC9/x9MefecoOy8u3tx988KOCCC0KB4AEIxuEc4CweiCQbwCRf4hSOwpGwSgYBSMVAAD1eEGP0cn+TgAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0009-0005-8845-1053","institution":"Beijing Forestry University","correspondingAuthor":true,"prefix":"","firstName":"Shiyin","middleName":"","lastName":"Yu","suffix":""},{"id":369825245,"identity":"e904b169-25cc-4c0c-8a55-a3a68c0130a3","order_by":1,"name":"Shan Wang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Shan","middleName":"","lastName":"Wang","suffix":""},{"id":369825246,"identity":"ed657c06-2432-4d0c-89ee-affb08190396","order_by":2,"name":"Min Tang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Min","middleName":"","lastName":"Tang","suffix":""},{"id":369825247,"identity":"9d49cdde-e9dc-46e0-b836-21ec89798ac5","order_by":3,"name":"Shuzhen Pan","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Shuzhen","middleName":"","lastName":"Pan","suffix":""},{"id":369825248,"identity":"9b8839ce-def1-405d-b800-f3a9fae9c236","order_by":4,"name":"Meixian Wang","email":"","orcid":"https://orcid.org/0000-0001-7737-2089","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Meixian","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2024-10-22 11:59:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5311541/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5311541/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":67472256,"identity":"06cace5b-38f1-40d0-9ab9-f98b93e59ac3","added_by":"auto","created_at":"2024-10-25 11:42:47","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":200494,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in the leaf pigment content of two shrubs with different Cd treatments. Data points and error bars represent mean and S.D., respectively. Different letters within the same pattern indicate statistically significant differences at \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05 according to Duncan test.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/1d49e483f6d41e806b3aad6b.jpeg"},{"id":67472257,"identity":"238f2a74-a61c-4df8-8d11-9eef764a9b35","added_by":"auto","created_at":"2024-10-25 11:42:47","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":204460,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in cell membrane permeability of two shrubs at different Cd concentrations. Data points and error bars represent mean and S.D., respectively. Different letters within the same pattern indicate statistically significant differences at \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05 according to Duncan test.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/91ce6d7543bb00225d0dbd86.jpeg"},{"id":67472258,"identity":"d0feb2bf-db76-489a-932d-d1833012e0ca","added_by":"auto","created_at":"2024-10-25 11:42:47","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":211027,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution ratio of Zn chemical forms in roots of two shrubs. Cd\u003csub\u003eE\u003c/sub\u003e, nitrate, chloride based inorganic salts and amino acids, etc. Cd\u003csub\u003eW\u003c/sub\u003e, water soluble organic acid salts, heavy metal phosphates [M(H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e], etc.; Cd\u003csub\u003eNaCl\u003c/sub\u003e, pectinates, heavy metals in the bound or adsorbed state of proteins, etc.; Cd\u003csub\u003eHAc\u003c/sub\u003e, insoluble metallic phosphates; Cd\u003csub\u003eHCl\u003c/sub\u003e, oxalic acid salt etc.; Cd\u003csub\u003eR\u003c/sub\u003e, residual form.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/6d656c821bf1ad684ca14c5c.jpeg"},{"id":67472261,"identity":"9351878c-48db-47da-be8e-9004cc3062c5","added_by":"auto","created_at":"2024-10-25 11:42:47","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":200816,"visible":true,"origin":"","legend":"\u003cp\u003eProportion of Zn in subcellular distribution of roots of two shrubs. F1, Metal-enriched particles; F2, Cellular debris；F3, Organelle components; F4, Heat-sensitive protein; F5, Heat stabilized protein.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/44266d2eab5c3e7c25ec421a.jpeg"},{"id":67472260,"identity":"2c81bf8d-cac5-4e30-8dfc-52f1fa469e3c","added_by":"auto","created_at":"2024-10-25 11:42:47","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":593716,"visible":true,"origin":"","legend":"\u003cp\u003eUltrastructure of root cells of two shrubs at different Cd concentration treatments. (a) \u003cem\u003eBuxus sinica.\u003c/em\u003e (b) \u003cem\u003eLigustrum×vicaryi. \u003c/em\u003eco, cortex; pe, pericycle; ph, phloem; ca, cambium; xy, xylem; SG, starch grain; CW, Cell wall; CP, cell plasmodesmata; V, vacuole; M, mitochondria; BM, black matter.\u003c/p\u003e","description":"","filename":"floatimage520.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/aa62755db2e305f1f26095aa.jpeg"},{"id":67472259,"identity":"ab7f37db-e44b-466f-b44e-2f87ae866b2e","added_by":"auto","created_at":"2024-10-25 11:42:47","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":144109,"visible":true,"origin":"","legend":"\u003cp\u003eInfrared spectrum characterization of root cell walls of two shrubs with different Cd concentration treatments. (a) \u003cem\u003eBuxus sinica\u003c/em\u003e. (b) \u003cem\u003eLigustrum×vicaryi.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage75.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/f33fa4bd9b8396c12aec3cf2.jpeg"},{"id":67576527,"identity":"f77df99f-ee6c-4611-8326-dd467cc83391","added_by":"auto","created_at":"2024-10-27 12:38:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2326709,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5311541/v1/7950c47f-aa22-4b83-9848-f6726a0c572f.pdf"}],"financialInterests":"","formattedTitle":"Integrative study of subcellular distribution, chemical forms, and physiological responses for understanding cadmium tolerance in two garden shrubs","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIndustrial activities, transportation emissions, and substantial construction waste associated with urban development have significantly increased the heavy metal content of soils in urban areas, leading to environmental pollution (Capuana \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Cadmium (Cd) is one of the most widely distributed heavy metals and is known for its high toxicity and mobility (Ali et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Kong et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Research on heavy metal pollution in urban soils in China indicates that Cd contamination levels exceed the background values for urban soils, making it a heavy metal pollutant that requires focused management (He et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Pan et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tong et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Cd is a typical non-essential mineral element that can harm photosynthesis and metabolic activities in plants when it accumulates excessively. Furthermore, Cd can easily enter animals and humans through the food chain, posing a significant risk to human health (Guo et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Zhao et al. \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, it is crucial to implement active remediation measures for Cd-contaminated soil to maintain a stable ecosystem.\u003c/p\u003e \u003cp\u003ePhysical and chemical methods for remediating heavy metal-contaminated soil have limitations, such as high costs and the potential for secondary pollution. Phytoremediation technology is a green, in-situ remediation approach that utilizes plants to extract or stabilize heavy metals in the soil, offering favorable economic and ecological benefits along with promising application prospects (Ali et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Zeng et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Currently, research on the phytoremediation of Cd primarily focuses on herbs such as \u003cem\u003eSedum alfredii\u003c/em\u003e (Li et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), \u003cem\u003eThlaspi caerulescens\u003c/em\u003e (Zhao et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), and \u003cem\u003eSolanum nigrum\u003c/em\u003e (Wei et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). However, herbs face challenges for large-scale engineering applications due to low biomass production and prolonged remediation times. In contrast, woody plants possess larger biomass and well-developed root systems, enhancing the exchange of heavy metal ions between soil and roots, thereby effectively absorbing heavy metal pollutants. Consequently, woody plants have become a research hotspot in phytoremediation in recent years (Capuana \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Based on the distribution and accumulation characteristics of Cd in woody plants, these species serve different phytoremediation purposes. For example, \u003cem\u003eSalix\u003c/em\u003e spp. (Yang et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), \u003cem\u003eMorus alba\u003c/em\u003e (Zeng et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), \u003cem\u003eKoelreuteria bipinnata\u003c/em\u003e (Luo et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), and \u003cem\u003eLonicera japonica\u003c/em\u003e (Liu et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) primarily assimilate Cd in their roots, making them ideal tree species for Cd phytostabilization. \u003cem\u003ePopulus\u003c/em\u003e spp. (He et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), \u003cem\u003eKoelreuteria paniculata\u003c/em\u003e (Yang et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and \u003cem\u003eEucalyptus\u003c/em\u003e spp. (Iori et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) exhibit strong adaptability to Cd stress, showcasing great potential for restoring Cd-contaminated soil. Existing studies primarily conduct pot or hydroponic experiments with saplings, while there is a lack of research focusing on commonly used urban ornamental shrubs that have high aesthetic value and broad applicability.\u003c/p\u003e \u003cp\u003e \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e are common shrubs found in urban green spaces, characterized by their strong stress resistance, wide adaptability, and ease of transplantation and survival. Studies have shown that both shrubs can accumulate Cd in urban environments and have potential for remediating Cd-contaminated soil (Chen et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Zeng et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Zhang et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, research on the mechanisms of Cd accumulation and tolerance in these two shrubs still needs to be conducted. Therefore, this experiment selected \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e as subjects for pot pollution simulation experiments. It investigated their physiological indices, Cd content, and accumulation characteristics in different plant organs, as well as the subcellular distribution, chemical form, ultrastructure, and cell wall functional groups of Cd in the roots under various Cd treatments. The aim is to analyze the enrichment characteristics and tolerance mechanisms of both shrubs under Cd stress, providing a theoretical basis for their effective application in remediating Cd-contaminated soil.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003ePlant material\u003c/p\u003e \u003cp\u003eThe 4-year-old saplings of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e used in the experiment were purchased from a nursery stock base in Shunyi District, Beijing, China. The experimental soil was a mixture of peat soil and perlite (v/v, 8:2), with its basic physicochemical properties and background values of heavy metals shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Based on the Cd content of soil in Beijing (Jia et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and the range of content adapted by plants in preliminary tests, this experiment established five levels of Cd contamination treatments: 0 (CK), 25 (T\u003csub\u003e1\u003c/sub\u003e), 50 (T\u003csub\u003e2\u003c/sub\u003e), 100 (T\u003csub\u003e3\u003c/sub\u003e), and 200 mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (T\u003csub\u003e4\u003c/sub\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBasic physical and chemical properties and heavy metal background value of soil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOrganic matter/\u003c/p\u003e \u003cp\u003eg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTotal N/\u003c/p\u003e \u003cp\u003eg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAlkali-hydrolyzable N/\u003c/p\u003e \u003cp\u003eg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTotal P/\u003c/p\u003e \u003cp\u003emg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAvailable P/\u003c/p\u003e \u003cp\u003emg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eTotal K/\u003c/p\u003e \u003cp\u003emg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eOlsen-K/\u003c/p\u003e \u003cp\u003emg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003cp\u003emg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e329.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e556\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3274\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e57.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eExperimental design\u003c/p\u003e \u003cp\u003eIn early March, 5 kg of mixed soil was added to each 3-gallon plastic pot (24 cm in diameter, 26.5 cm deep), with trays placed underneath the pots to prevent heavy metal loss and environmental pollution. According to the predetermined gradients, analytical-grade CdCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;2.5H\u003csub\u003e2\u003c/sub\u003eO powder was weighed and dissolved in deionized water. Subsequently, an aerosol sprayer was used to ensure that the heavy metal solution uniformly penetrated the soil, guaranteeing an even mixture of the drug and soil. After that, the contaminated soil was placed in a cool location to equilibrate for one month, and three parallel groups were processed for each Cd concentration treatment. In early April, saplings with similar height, crown width, and root length were selected for transplantation into the pots, with one plant per pot. Deionized water was regularly sprayed in consistent amounts during subsequent growth to maintain the soil moisture content at 60\u0026ndash;70% of field holding capacity. In early September, samples were collected using the complete harvest method.\u003c/p\u003e \u003cp\u003eMeasurement Methods\u003c/p\u003e \u003cp\u003eThe harvested plants were thoroughly rinsed with tap water three times. Subsequently, the plant roots were dipped in 20 mmol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e Na\u003csub\u003e2\u003c/sub\u003e-EDTA for 20 minutes to eliminate surface-absorbed cadmium (Cd). Afterward, the plants were rinsed three times with deionized water, dried, and then divided into leaf, stem, and root tissues, which were later used for the determination of various studied parameters. Some plant samples were dried in an oven at 105\u0026deg;C for 30 minutes, followed by further drying at 70\u0026deg;C until a constant dry weight was achieved, allowing for the determination of plant dry weight and Cd content. The final samples were stored after being finely ground using a pulverizer. Other plant samples were preserved in a \u0026minus;\u0026thinsp;80\u0026deg;C refrigerator (Meng et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAfter grinding, 1 g of each root, branch, and leaf sample was digested using the HNO\u003csub\u003e3\u003c/sub\u003e-H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e method. Following complete digestion, the samples were filtered and brought to a constant volume of 50 mL. The Cd content in the plant tissues was measured using inductively coupled plasma emission spectrometry (ICP-OES, Agilent 5110) (Konieczynski et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Additionally, 0.5 g of fresh leaf samples was soaked in 10 mL of 96% ethanol in the dark for 24 hours to measure chlorophyll a, b, and carotenoid contents, as described by Chen et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) Cell membrane permeability was assessed using the electrical conductivity method, following Kaya et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Different chemical forms of Cd in the plants were sequentially extracted using differential centrifugation and chemical reagents, according to the method of Zou et al. (\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Differential centrifugation was employed to separate the subcellular distribution of Cd, as outlined by Wang et al. (\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The ultrastructure of plant cells was observed using transmission electron microscopy, following the method of Jiang et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). The plant cell walls of the roots were extracted using the method described by Riaz et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), elucidating the information on chemical functional groups in the plant cell walls under Cd stress through Fourier transform infrared spectroscopy measurements.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll data obtained were statistically analyzed using Excel 2010 and presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (S.D.). One-way analysis of variance (ANOVA) was performed on the data using SPSS 26.0, followed by Duncan's test at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. Graphical representations were created using Origin 2021.\u003c/p\u003e \u003cp\u003eThe bioconcentration factor (BCF) in the plant was calculated as BF\u0026thinsp;=\u0026thinsp;Cd content in plant tissues (mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)/Cd content in the soil (mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). This factor reflects the ability of the plant to assimilate and transfer Cd from the soil to its tissues (Uddin et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe translocation factor (TF) of Cd in the plant was calculated as TF\u0026thinsp;=\u0026thinsp;Cd content in shoots (mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)/Cd content in roots (mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), which is used to evaluate the plant's capability to transport Cd from the roots to the shoots (Zakaria et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003ePlant growth\u003c/p\u003e\n\u003cp\u003eTo study the effect of exogenously applied Cd on plant growth, the biomass of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e was analyzed. Results indicated that the total biomass of \u003cem\u003eB. sinica\u003c/em\u003e gradually decreased as the Cd treatment gradient increased, while that of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e showed a pattern of promotion at low Cd concentrations and inhibition at high Cd concentrations. Under different Cd treatment gradients, the leaf biomass of \u003cem\u003eB. sinica\u003c/em\u003e was not affected compared to the control. However, the biomass of the branches and roots of \u003cem\u003eB. sinica\u003c/em\u003e decreased gradually with increasing Cd treatment gradients, with minimum values of 26.80 g and 29.46 g, respectively, representing reductions of 31.89% and 62.69% under T2 and T4 treatments compared with the control (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Likewise, the biomass of leaves and branches in \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e showed no notable change under Cd stress, whereas root biomass exhibited an initial increase followed by a decrease as Cd concentrations increased. As shown in Table 1, the reduction in root biomass was smallest (32.71 g) at T3 treatment, significantly reduced by 27.05% compared to the control (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05; Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u0026nbsp;\u003c/strong\u003eBiomass of two shrubs treated with different Cd treatments (g)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 11%;\"\u003e\n \u003cp\u003eShrub\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eTreatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003eLeaf\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003eBranch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003eRoot\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 11%;\"\u003e\n \u003cp\u003e\u003cem\u003eBuxus sinica\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e44.87\u0026plusmn;8.92a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e39.35\u0026plusmn;7.01a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e78.97\u0026plusmn;8.56a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e163.19\u0026plusmn;21.48a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e49.50\u0026plusmn;4.67a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e38.11\u0026plusmn;4.91a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e68.07\u0026plusmn;12.23ab\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e155.67\u0026plusmn;16.32ab\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e38.18\u0026plusmn;8.27a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e26.80\u0026plusmn;5.43b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e54.20\u0026plusmn;9.11b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e119.18\u0026plusmn;19.75c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e38.65\u0026plusmn;2.55a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e32.09\u0026plusmn;4.49ab\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e54.81\u0026plusmn;11.48b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e125.54\u0026plusmn;16.58bc\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e39.84\u0026plusmn;7.33a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e28.04\u0026plusmn;2.72b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e29.46\u0026plusmn;6.97c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e102.09\u0026plusmn;19.00c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 11%;\"\u003e\n \u003cp\u003e\u003cem\u003eLigustrum\u003c/em\u003e\u0026times;\u003cem\u003evicaryi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e40.90\u0026plusmn;2.78a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e42.51\u0026plusmn;4.36a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e44.84\u0026plusmn;4.52ab\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e128.26\u0026plusmn;9.48ab\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e42.11\u0026plusmn;4.73a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e43.77\u0026plusmn;4.01a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e46.63\u0026plusmn;4.38a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e132.50\u0026plusmn;9.59a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e41.87\u0026plusmn;5.46a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e42.92\u0026plusmn;4.13a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e53.17\u0026plusmn;10.60a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e137.96\u0026plusmn;11.76a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e39.35\u0026plusmn;3.84a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e42.40\u0026plusmn;1.45a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e32.71\u0026plusmn;1.32c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e114.46\u0026plusmn;1.09b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003eT\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e36.67\u0026plusmn;3.82a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e41.48\u0026plusmn;2.24a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 19%;\"\u003e\n \u003cp\u003e35.44\u0026plusmn;3.79bc\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e113.58\u0026plusmn;9.26b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eNote: Values are presented as mean \u0026plusmn; S.D. Values with different letters within the same column indicate significant differences at the P \u0026lt; 0.05 level between concentrations according to Duncan test.\u003c/p\u003e\n\u003cp\u003eLeaf pigment content\u003c/p\u003e\n\u003cp\u003eWith the increase of the Cd treatment gradient, the chlorophyll a and carotenoid contents in the leaves of \u003cem\u003eB. sinica\u003c/em\u003e displayed a decreasing trend, peaking at T4 treatment (0.58 mg\u0026middot;g⁻\u0026sup1;) and reaching the lowest at T3 treatment (0.16 mg\u0026middot;g⁻\u0026sup1;), both of which were significantly different from the control (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Additionally, the chlorophyll b content of \u003cem\u003eB. sinica\u003c/em\u003e initially decreased and then increased with the increasing Cd treatment gradient, reaching its minimum at T1 treatment and maximum at T4 treatment, both noticeably lower compared to the control (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). The chlorophyll a content of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e showed a tendency to increase and then decrease with increasing Cd treatment gradients, reaching a maximum value of 0.78 mg\u0026middot;g⁻\u0026sup1; at T2 treatment, but there was no significant difference compared with the control. Similarly, the chlorophyll b and carotenoid contents were unaffected by Cd exposure compared to the control (\u003cem\u003eP\u003c/em\u003e \u0026gt; 0.05; Fig. 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 1\u0026nbsp;\u003c/strong\u003eChanges in the leaf pigment content of two shrubs with different Cd treatments. Data points and error bars represent mean and S.D., respectively. Different letters within the same pattern indicate statistically significant differences at \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05 according to Duncan test.\u003c/p\u003e\n\u003cp\u003eCell membrane permeability\u003c/p\u003e\n\u003cp\u003eLow to medium concentrations of cadmium (Cd) had a beneficial effect on the cell membrane permeability of \u003cem\u003eB. sinica\u003c/em\u003e branches, which gradually decreased as the Cd concentration increased to high levels. The membrane permeability of \u003cem\u003eB. sinica\u003c/em\u003e branches was highest in the T4 treatment, being 1.33-fold greater than that of the control (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). The root membrane permeability of \u003cem\u003eB. sinica\u003c/em\u003e also gradually increased with rising Cd content, peaking in the T4 treatment, with significant differences compared to the control (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). However, there was no significant difference in the membrane permeability of \u003cem\u003eB. sinica\u003c/em\u003e leaves compared to the control under different Cd treatments. In contrast, the membrane permeability of the leaves did not significantly differ from the control across various treatment gradients. The membrane permeability of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e leaves increased with increasing Cd content. In the T1-T4 Cd treatments, it was 1.01- to 1.57-fold higher than that of the control. However, Cd treatment did not significantly impact the cell membrane permeability of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e branches and roots (Fig. 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 2\u0026nbsp;\u003c/strong\u003eChanges in cell membrane permeability of two shrubs at different Cd concentrations. Data points and error bars represent mean and S.D., respectively. Different letters within the same pattern indicate statistically significant differences at \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05 according to Duncan test.\u003c/p\u003e\n\u003cp\u003eCd content in various tissues\u003c/p\u003e\n\u003cp\u003eThe Cd content in various tissues of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e significantly increased with the Cd treatment gradient, peaking at the T4 treatment with notable differences compared to the control (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). Generally, the Cd content in the roots of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e was significantly higher than that in the leaves and branches within the same treatment gradient, being 117.68-fold and 38.30-fold higher than that of the leaves, and 133.90-fold and 32.73-fold higher than that of the branches, respectively. Moreover, exogenous Cd application could noticeably further increase the Cd content in various tissues of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e compared to \u003cem\u003eB. sinica\u003c/em\u003e as the Cd content increased. As shown in Table 2, the Cd content in the leaves, branches, and roots of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e was 19.01 times, 9.42 times, and 2.01 times higher than that of \u003cem\u003eB. sinica\u003c/em\u003e, respectively (Table 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u0026nbsp;\u003c/strong\u003eCd concentration in tissues of two shrubs at different Cd concentration treatments\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"98%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003eShrub\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eTreatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003eLeaf\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003eBranch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003eRoot\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 18%;\"\u003e\n \u003cp\u003e\u003cem\u003eBuxus sinica\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.14\u0026plusmn;0.04b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.20\u0026plusmn;0.04d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.57\u0026plusmn;0.13c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.25\u0026plusmn;0.09b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.41\u0026plusmn;0.08cd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e16.29\u0026plusmn;4.57c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.68\u0026plusmn;0.16a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.66\u0026plusmn;0.06b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e63.64\u0026plusmn;12.55b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.70\u0026plusmn;0.18a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.50\u0026plusmn;0.17bc\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e66.95\u0026plusmn;12.81b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.82\u0026plusmn;0.16a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e1.71\u0026plusmn;0.21a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e96.50\u0026plusmn;7.87a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 18%;\"\u003e\n \u003cp\u003e\u003cem\u003eLigustrum\u0026times;vicaryi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.14\u0026plusmn;0.04d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.12\u0026plusmn;0.03d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e0.76\u0026plusmn;0.05e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.94\u0026plusmn;0.06d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e1.10\u0026plusmn;0.13d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e36.00\u0026plusmn;3.07d\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e2.93\u0026plusmn;0.19c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e5.24\u0026plusmn;0.76c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e74.01\u0026plusmn;10.70c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e9.74\u0026plusmn;0.39b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e9.32\u0026plusmn;0.21b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e158.23\u0026plusmn;21.58b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 15%;\"\u003e\n \u003cp\u003eT\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e15.59\u0026plusmn;2.05a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e16.11\u0026plusmn;2.69a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 22%;\"\u003e\n \u003cp\u003e202.73\u0026plusmn;31.42a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eNote: Values are presented as mean \u0026plusmn; S.D. Values with different letters within the same column indicate significant differences at \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05 level between concentrations according to Duncan test.\u003c/p\u003e\n\u003cp\u003eCd bioconcentration factors and translocation factor\u003c/p\u003e\n\u003cp\u003eUnder Cd treatment, the bioconcentration factor (BCF) of the aerial parts of both shrubs was less than 1, with no significant differences among the various treatment gradients. After the application of exogenous Cd, the BCF values of the roots of both shrubs increased at low Cd levels, gradually decreasing as the Cd concentration rose to high levels, with the lowest BCF values observed in the T4 treatment. Furthermore, the BCF values of the roots of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e were consistently greater than 1, while those of \u003cem\u003eB. sinica\u003c/em\u003e exceeded 1.0 only in the T2 treatment. By calculating the translocation factor (TF) of Cd, it was found that the TF values of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e were both significantly less than 1, ranging from 0.01 to 0.32 and 0.03 to 0.17, respectively. Additionally, after increasing exogenous Cd treatment, the TF of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e was higher than that of \u003cem\u003eB. sinica\u003c/em\u003e under the same Cd treatment (Table 3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u0026nbsp;\u003c/strong\u003eCd enrichment coefficients in tissues of two shrubs at different Cd concentrations\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 16%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eShrub\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 12%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eTreatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" style=\"width: 53%;\"\u003e\n \u003cp\u003eBCF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 17%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eTF\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003eLeaf\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003eBranch\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003eRoot\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 16%;\"\u003e\n \u003cp\u003e\u003cem\u003eBuxus sinica\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.67\u0026plusmn;0.19a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.95\u0026plusmn;0.04a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e2.70\u0026plusmn;0.60a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.32\u0026plusmn;0.11a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.02\u0026plusmn;0.27b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.65\u0026plusmn;0.18c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.02\u0026plusmn;0.04b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.02\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e1.27\u0026plusmn;0.25b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.02\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.67\u0026plusmn;0.13c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.00\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.48\u0026plusmn;0.04c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.01\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" style=\"width: 16%;\"\u003e\n \u003cp\u003e\u003cem\u003eLigustrum\u0026times;vicaryi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.68\u0026plusmn;0.17a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.59\u0026plusmn;0.12a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e3.63\u0026plusmn;0.23a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.17\u0026plusmn;0.03a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.04\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.04\u0026plusmn;0.01b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e1.44\u0026plusmn;0.12b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.03\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.06\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.10\u0026plusmn;0.02b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e1.48\u0026plusmn;0.21b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.06\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.10\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.09\u0026plusmn;0.00b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e1.58\u0026plusmn;0.22b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.06\u0026plusmn;0.01b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 12%;\"\u003e\n \u003cp\u003eT\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16%;\"\u003e\n \u003cp\u003e0.08\u0026plusmn;0.01b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e0.08\u0026plusmn;0.01b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 18%;\"\u003e\n \u003cp\u003e1.01\u0026plusmn;0.16c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17%;\"\u003e\n \u003cp\u003e0.08\u0026plusmn;0.23b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eNote: Values are presented as mean \u0026plusmn; S.D. Values with different letters within the same column indicate significant differences at the \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05 level between concentrations according to Duncan test.\u003c/p\u003e\n\u003cp\u003eChemical forms\u003c/p\u003e\n\u003cp\u003eAccording to our analyses, the chemical form of Cd extracted by NaCl was dominant in the roots of \u003cem\u003eB. sinica\u003c/em\u003e (19.21% to 69.45%) and \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e (21.02% to 69.87%). The distribution ratio of NaCl-extractable Cd in the roots of these two shrubs increased with exogenous Cd application and peaked at the T4 treatment (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). In B. sinica roots, Cd extracted by HAc, which is less mobile and toxic, increased when Cd content was low and then decreased as the exogenous Cd treatment content increased. However, the distribution ratios of the more mobile and toxic Cd\u003csub\u003eE\u003c/sub\u003e and Cd\u003csub\u003eW\u003c/sub\u003e tended to decrease with enhanced Cd levels. In contrast, the proportions of CdE and Cd\u003csub\u003eW\u003c/sub\u003e in \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e roots did not change significantly with increasing Cd treatment gradient, while the proportions of other chemical forms of Cd showed a decreasing trend. Overall, the dominant chemical form of Cd in the roots of both shrubs was moderately active (Fig. 3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 3\u0026nbsp;\u003c/strong\u003eDistribution ratio of Zn chemical forms in roots of\u0026nbsp;two shrubs.\u0026nbsp;Cd\u003csub\u003eE\u003c/sub\u003e, nitrate, chloride based inorganic salts and amino acids, etc. Cd\u003csub\u003eW\u003c/sub\u003e, water soluble organic acid salts, heavy metal phosphates [M(H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e], etc.; Cd\u003csub\u003eNaCl\u003c/sub\u003e, pectinates, heavy metals in the bound or adsorbed state of proteins, etc.; Cd\u003csub\u003eHAc\u003c/sub\u003e, insoluble metallic phosphates; Cd\u003csub\u003eHCl\u003c/sub\u003e, oxalic acid salt etc.; Cd\u003csub\u003eR\u003c/sub\u003e, residual form.\u003c/p\u003e\n\u003cp\u003eSubcellular distribution\u003c/p\u003e\n\u003cp\u003eUnder Cd treatment, the proportion of Cd in the roots of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e primarily accumulated in the cellular debris fractions, accounting for 54.95% to 72.95% and 30.50% to 60.70%, respectively. The proportion of Cd in the cellular debris fraction of B. sinica increased with the addition of Cd to the soil and peaked at the T4 treatment (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). Nevertheless, the percentages of Cd in the organelle component and heat-sensitive protein fractions gradually decreased with increasing Cd concentration in the soil. As the Cd treatment gradient increased, the subcellular distribution of Cd in L. \u0026times; vicaryi showed a remarkable increase in heat-stabilized proteins, while opposite trends were observed in metal-enriched particles and heat-sensitive protein fractions. Moreover, the proportion of Cd in \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e\u0026apos;s cellular debris fractions increased when the Cd level was low and gradually reduced as the Cd concentration increased to higher levels (Fig. 4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 4\u0026nbsp;\u003c/strong\u003eProportion of Zn in subcellular distribution of roots of two shrubs. F1, Metal-enriched particles; F2, Cellular debris；F3, Organelle components; F4, Heat-sensitive protein; F5, Heat stabilized protein.\u003c/p\u003e\n\u003cp\u003eUltrastructure of root cells\u003c/p\u003e\n\u003cp\u003eIn this study, control (CK), low content (T2), and high content (T4) groups were selected to further observe the microscopic changes in root cell morphology and the distribution of Cd in the cells under Cd treatment using transmission electron microscopy (TEM). Fig. 5a,b showed that, under low concentration Cd treatment, there was an increase in the intercellular gap compared with CK in \u003cem\u003eB. sinica\u003c/em\u003e, along with obvious black deposits in the cells. When Cd content was high, the cell arrangement in B. sinica was disrupted, cells were significantly deformed, and a large amount of black deposits accumulated on the cell walls and in the vacuoles. Similarly, for \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e, there was a substantial aggregation of black deposits within the cells, predominantly near the cell walls, vacuoles, and cell plasmodesmata under low Cd treatment. At high levels of Cd, some \u003cem\u003eLigustrum vicaryi\u003c/em\u003e cells disintegrated, and cell walls ruptured, with black deposits accumulating near the cell walls and cell plasmodesmata.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 5\u0026nbsp;\u003c/strong\u003eUltrastructure of root cells of two shrubs at different Cd concentration treatments. (a) \u003cem\u003eBuxus sinica.\u003c/em\u003e (b) \u003cem\u003eLigustrum\u0026times;vicaryi.\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003eco, cortex; pe, pericycle; ph, phloem; ca, cambium; xy, xylem; SG, starch grain; CW, Cell wall; CP, cell plasmodesmata; V, vacuole; M, mitochondria; BM, black matter.\u003c/p\u003e\n\u003cp\u003eFourier transform infrared spectroscopy of root cell wall\u003c/p\u003e\n\u003cp\u003eThe Fourier transform infrared spectroscopy (FTIR) spectra of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e were analyzed in the control (CK), low concentration (T2), and high concentration (T4) groups to determine the changes in functional groups of the cell wall in plant roots under Cd stress (Fig. 6a,b, Table 5). The ratio A/A\u003csub\u003e2927\u003c/sub\u003e represents the absorbance of the characteristic peak of methyl (-CH3) relative to that of the characteristic peak, which can be used for semi-quantitative analysis of the functional groups involved in heavy metal binding based on changes in the ratio. The study showed that the cell walls of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e roots contain abundant functional groups, especially oxygen-containing functional groups. Under Cd treatment, the absorption peaks with the largest shifts in the cell walls of \u003cem\u003eBuxus\u003c/em\u003e roots were the stretching vibration peaks of hydroxyl/amino and cellulose carbohydrate rings, which shifted 12 cm to lower frequencies and 8 cm to higher frequencies under low Cd treatment, and 8 cm to lower frequencies and 6 cm to higher frequencies under high Cd treatment, respectively. In the cell walls of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e roots, significant shifts were observed in the stretching vibration peaks of hydroxyl/amino, carboxyl, and cellulose glycan carbohydrate rings under Cd treatment, resulting in shifts of 6, 5, and 4 cm to higher frequencies at T4 treatment, respectively. Additionally, the A/A\u003csub\u003e2927\u003c/sub\u003e values of the hydroxyl/amino and cellulose glycan stretching vibration absorption peaks in the cell walls of \u003cem\u003eL.\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026times;\u0026nbsp;vicaryi\u003c/em\u003e roots decreased with increasing Cd treatment, while the A/A\u003csub\u003e2927\u003c/sub\u003e values of the carboxyl characteristic peaks in the treatment groups were higher than those in the control.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig. 6\u003c/strong\u003e Infrared spectrum characterization of root cell walls of two shrubs with different Cd concentration treatments. (a) \u003cem\u003eBuxus sinica\u003c/em\u003e. (b) \u003cem\u003eLigustrum\u0026times;vicaryi.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5\u0026nbsp;\u003c/strong\u003eAnalysis of infrared spectrum characteristic peaks in the root cell walls of\u0026nbsp;two shrubs\u0026nbsp;under different Cd concentration treatments\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"99%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 9%;\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 10%;\"\u003e\n \u003cp\u003eNumber\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 23%;\"\u003e\n \u003cp\u003eFunction group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 13%;\"\u003e\n \u003cp\u003eWavenum-ber/cm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 16%;\"\u003e\n \u003cp\u003eCd-T\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 16%;\"\u003e\n \u003cp\u003eCd-T\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003eA/A\u003csub\u003e29-27\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003eA/A\u003csub\u003e29-27\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003eOffset/cm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003ecm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003eA/A\u003csub\u003e29--27\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003eOffse-t/cm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e\n \u003cp\u003ecm\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"8\" style=\"width: 9%;\"\u003e\n \u003cp\u003e\u003cem\u003eBuxus sinica\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003ehydroxyl/amino (-OH/-NH)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e3400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eMethyl (-CH\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e2927\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eAmide(I)\u0026nbsp;(-C=O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1644\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eAmide(Ⅱ)\u0026nbsp;(-N-H)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1515\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eCarbon-Hydrogen(C-H)or Carbon-Oxygen (C-O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1429\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003ealcoholic hydroxyl C-O\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1315\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eSulfate ester (C-O-S) or carboxyl (C-O) or phosphoric acid (C-O-P)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1264\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003ecellulose glycan bending (-C-H) or (-C-C, -C-O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1042\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"9\" style=\"width: 9%;\"\u003e\n \u003cp\u003e\u003cem\u003eLigustrum\u003c/em\u003e\u0026times;\u003cem\u003evicaryi\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eLigustrum\u003c/em\u003e\u0026times;\u003cem\u003evicaryi\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eLigustrum\u0026times;vicaryium\u0026times;vicaryi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003ehydroxyl/amino (-OH/-NH)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e3400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eMethyl (-CH\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e2927\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eAmide(I)\u0026nbsp;(-C=O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1644\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eAmide(Ⅱ) (-N-H)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1515\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eCarbon-Hydrogen (C-H) or Carbon-Oxygen (C-O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1429\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eCarboxyl (-COOH) or Amide(Ⅲ) (-C-N)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1377\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003ealcoholic hydroxyl (C-O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1315\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003eSulfate ester (C-O-S) or carboxyl (C-O) or phosphoric acid C-O-P\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1264\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 10%;\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 23%;\"\u003e\n \u003cp\u003ecellulose glycan bending (-C-H) or (-C-C, -C-O)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 13%;\"\u003e\n \u003cp\u003e1042\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e1.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 8%;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Discussion","content":"\u003cp\u003eTolerance characteristics of two shrubs under Cd stress\u003c/p\u003e \u003cp\u003ePlant growth characteristics and physiological metabolism are crucial evaluation indicators for assessing plant tolerance to heavy metal toxicity. Cd is a non-essential element for plant growth; however, excessive Cd can inhibit plant development, damage cellular structures, and impair functional activity, leading to irreversible effects on the plant (Wang et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In this study, Cd exhibited a strong toxic effect on \u003cem\u003eB. sinica\u003c/em\u003e. As the levels of Cd treatment increased, the biomass of \u003cem\u003eB. sinica\u003c/em\u003e gradually decreased. Additionally, the results indicated that lower concentrations of Cd (25, 50 mg\u0026middot;kg⁻\u0026sup1;) promoted biomass accumulation in \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e, while higher concentrations of Cd (100, 200 mg\u0026middot;kg⁻\u0026sup1;) inhibited plant growth to some extent. This suggests that \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e has a stronger tolerance to Cd-contaminated soil compared to \u003cem\u003eB. sinica\u003c/em\u003e. Similar responses were observed in other plants under Cd stress. The biomass accumulation of Sphagneticola calendulacea showed no significant effect at lower concentrations of 25 mg\u0026middot;kg⁻\u0026sup1;; however, higher Cd treatment (\u0026ge;\u0026thinsp;100 mg\u0026middot;kg⁻\u0026sup1;) notably inhibited plant growth (Lu et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In \u003cem\u003eL.\u003c/em\u003e \u0026times; \u003cem\u003evicaryi\u003c/em\u003e,, biomass production significantly increased when Cd concentrations were low (\u0026le;\u0026thinsp;100 mg\u0026middot;kg⁻\u0026sup1;), but there was a sharp decline under higher Cd treatment (\u0026ge;\u0026thinsp;25 mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (Jia et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). These studies suggest that different plants have varying adaptation ranges to Cd content, and appropriate levels of Cd can promote plant growth to a certain extent, potentially playing a positive role in Cd accumulation.\u003c/p\u003e \u003cp\u003ePhotosynthesis is a crucial process by which plants convert energy from their environment, and the levels of photosynthetic pigments reflect the efficiency of this process. Chlorophyll a, chlorophyll b, and carotenoids are the primary components of photosynthetic pigments. Studies have shown that Cd stress can reduce the activity of chlorophyll synthase and activate enzymes involved in chlorophyll degradation, leading to a decrease in the synthesis and content of photosynthetic pigments, manifesting as leaf yellowing (Zhang et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Additionally, since Cd is a non-essential element for plants, it can bind with thiol groups in proteins, damaging the structure and functional activity of chloroplasts (Cherif et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). In this study, it was observed that the contents of chlorophyll a and carotenoids in \u003cem\u003eB. sinica\u003c/em\u003e exhibited an overall declining trend with increasing Cd treatment levels, and similar trends were seen in chlorophyll a, chlorophyll b, and carotenoids of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e. Similarly, Dutta et al. (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)reported a reduction in chlorophyll a, chlorophyll b, and carotenoid contents in the leaves of \u003cem\u003eArachis hypogaea\u003c/em\u003e with higher exogenous Cd levels. Furthermore, this study revealed that low Cd content initially inhibited chlorophyll b content in \u003cem\u003eB. sinica\u003c/em\u003e, but higher levels promoted it. The same trend was observed in \u003cem\u003eDavidia involucrata\u003c/em\u003e, where chlorophyll b levels initially decreased under lower Cd treatment but increased with higher Cd concentrations (Yang et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). This phenomenon suggests that plants may enhance their tolerance to Cd by increasing their chlorophyll content (Dezhban et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe cell membrane is a crucial structure that regulates and controls the transport and exchange of substances across cells. Under normal conditions, the cell membrane exhibits selective permeability. However, when plants are stressed by heavy metals, the permeability of the cell membrane increases, leading to the leakage of intracellular components and the entry of external substances, resulting in physiological dysfunction (Wei et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Changes in plasma membrane permeability are assessed by the conductivity of plant cell extracts, which serves as an indicator of plant responses to heavy metal pollution. Under Cd stress, the relative conductivity during the tillering and ripening stages of rice significantly exceeded that of the control, indicating increased plasma membrane permeability and severe membrane damage (Huang et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Similarly, in the present study, the relative conductivity of cell plasma membranes in various tissues of \u003cem\u003eB. sinica\u003c/em\u003e and the leaves of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e increased with higher Cd content, suggesting that the permeability of cell plasma membranes in both shrubs progressively increased, leading to greater intracellular substance leakage. This phenomenon may be attributed to Cd stress causing alterations in the composition of plasma membrane lipid fatty acids and enhanced oxidative processes, which result in increased permeability and reduced membrane stability (Spiridonova et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAnalysis of tolerance characteristics of two shrubs under Cd stress\u003c/p\u003e \u003cp\u003eRoot retention or translocation to the aerial parts of plants plays a pivotal role in their tolerance to heavy metals in the soil (Shen et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In this study, the Cd content in various tissues of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e significantly increased with higher Cd concentrations. Furthermore, most of the Cd absorbed was retained in the roots, suggesting that both shrubs can limit the translocation of Cd to the aerial parts, consistent with previous studies on species such as \u003cem\u003eImpatiens walleriana\u003c/em\u003e (Lai \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), \u003cem\u003eMorus spp\u003c/em\u003e. (Huang et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), and \u003cem\u003eBoehmeria nivea\u003c/em\u003e (Wang et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), which primarily accumulate Cd in their roots, with accumulation levels increasing alongside Cd concentration. Therefore, the accumulation of heavy metals in the roots is one of the key mechanisms for tolerating heavy metal stress. The excessive accumulation of Cd in the roots may be due to the role of inner cortex cells in the root tissue, which serve as lateral interceptors, limiting the transfer of Cd to the aerial parts and thereby mitigating Cd toxicity and its impacts on physiological metabolism in plants (Akhter et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBCF and TF are two key parameters used to evaluate heavy metal accumulation efficiency in plants (Wu et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). In this study, the BCF values of the aerial tissues of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e were relatively low. However, the BCF values of the roots of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e were consistently higher than 1 when treated with different concentrations of Cd, while those of the roots of \u003cem\u003eB. sinica\u003c/em\u003e exceeded 1 only under T2 treatment. Additionally, BCF values of the roots of both shrubs decreased with increasing Cd concentration. Furthermore, the TF values of both shrubs under Cd treatment were less than 1, which was significantly lower than those in the control group. This phenomenon suggests that Cd stress reduced the ability of the plants to absorb and translocate Cd to the aerial parts. Plants with BCFs and TFs greater than 1 are usually considered suitable for phytoextraction, whereas those with high BCF (\u0026gt;\u0026thinsp;1) and low TF (\u0026lt;\u0026thinsp;1) are considered suitable for phytostabilization (Hou et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In the present study, the roots of both shrubs exhibited higher BCF and lower TF values, indicating their efficient ability to restrict Cd translocation to the aerial parts, thus positioning them as potential woody plants for stabilizing Cd-contaminated soil. This finding aligns with results from other studies, where the BCF values of \u003cem\u003eCalendula calypso\u003c/em\u003e were greater than 1 under each Cd treatment, while TF values were less than 1, making it suitable for the stabilization of Cd-contaminated soil (Farooq et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Similarly, the BCF values of the roots and stems of \u003cem\u003eEuryops pectinatus\u003c/em\u003e exceeded 1 under Cd stress, while TF values remained lower than 1, reflecting its relatively higher Cd accumulation capacity, thereby protecting the aerial parts from Cd toxicity (Jia et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAnalysis of accumulation mechanisms of two shrubs under Cd stress\u003c/p\u003e \u003cp\u003eHeavy metals absorbed and transported by plants in various chemical forms are present in different tissues (Liu et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The toxicity and mobility of Cd are closely associated with its chemical forms. Consequently, research has focused on extracting different chemical forms of Cd using various extractants, revealing that the lower the polarity of the chemical forms, the stronger their migration ability and greater their toxicity. The migration ability of Cd in ethanol- and water-extractable fractions is higher than in other forms, and these forms exhibit greater toxicity to organisms (Zheng et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In the roots of \u003cem\u003eLandoltia punctata\u003c/em\u003e, the NaCl-extracted state, which has moderate toxicity and mobility, was the predominant form of Cd (30.15\u0026ndash;88.66%). Additionally, the proportion and concentration of HCl- and HAc-extracted Cd increased with rising Cd concentration (Wang et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). A similar characteristic has been observed in the roots of oilseed rape (Ru et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) and \u003cem\u003eSolanum nigrum\u003c/em\u003e (Li et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), where the proportion of NaCl-extractable Cd was the highest. The results of this study align with previous research, indicating that in the roots of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e, most of the Cd was primarily in the NaCl-extractable form, with the proportion of NaCl-extracted Cd notably increasing with higher Cd content. According to Wu et al. (\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), NaCl extraction mainly comprised pectate and protein-integrated Cd, which may form complexes with organic groups on the root cell wall, resulting in reduced toxicity. Furthermore, a larger proportion of Cd in the NaCl-extracted state may alleviate Cd toxicity, allowing it to occupy a relatively high proportion in plants. It was also found that as exogenous Cd content increased, the proportion of chemical forms with high mobility and toxicity decreased in the roots of these two shrubs. These findings are consistent with studies on \u003cem\u003eAgrocybe aegerita\u003c/em\u003e, which converted Cd into undissolved pectate and protein-bound forms when subjected to Cd stress to reduce Cd toxicity (Li et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Similarly, in the leaves of \u003cem\u003eSalix matsudana\u003c/em\u003e, the proportion of HCl- and HAc-extracted Cd in the roots increased with rising Cd concentration ( Zou et al.(2023). Overall, these results suggest that plants may tolerate heavy metals by converting Cd into less toxic chemical forms, with the dominant forms and their proportions varying among different plant species.\u003c/p\u003e \u003cp\u003eThe mode of heavy metal subcellular distribution in plants is a crucial factor in determining the extent of metal toxicity and the plant tolerance mechanism. Previous research has shown that plants can regionalize heavy metals in relatively inactive areas, such as cell walls and soluble fractions, to reduce their toxicity (Ma et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In this study, Cd in the roots of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e was primarily accumulated in the cell walls (54.95%-72.95% and 30.50%-60.70%, respectively). These findings are consistent with studies on \u003cem\u003eKandelia obovata\u003c/em\u003e (Weng et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), \u003cem\u003eSalix matsudana\u003c/em\u003e (Wu et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and \u003cem\u003eMiscanthus sacchariflorus\u003c/em\u003e (Xin et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), which also reported a high proportion of Cd predominantly stored in the cell walls. The cell wall serves as the first barrier for cells to mitigate Cd damage, as its surface can fix heavy metal ions and limit their access to the plasma membrane and cytoplasm, thereby alleviating Cd toxicity (Loix et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Yu et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Additionally, increasing the thickness of the cell wall to fix heavy metals plays a critical role in Cd retention in woody plants (Li et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Furthermore, in the current study, the proportion of heat-sensitive proteins in \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e increased with higher Cd content, indicating that these components may also have a mitigating effect under Cd stress. Overall, the subcellular distribution results demonstrate that retaining Cd in the cell walls of roots may play a significant role in the Cd detoxification mechanism of these two shrubs.\u003c/p\u003e \u003cp\u003eTo understand the mechanisms of cadmium (Cd) detoxification, it is essential to explore the internal structural changes of cells through ultrastructural observation. In the current study, a significant accumulation of dark deposits was observed on the cell walls of the roots of both shrub species under Cd stress. This finding aligns with previous research, which reported visible Cd deposits in the cell walls of \u003cem\u003eDittrichia viscosa\u003c/em\u003e after 10 days of treatment with 15 mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e Cd, with a marked increase corresponding to higher Cd concentrations and prolonged exposure (Fern\u0026aacute;ndez et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Furthermore, electron-dense precipitates were identified in vacuoles and on the cell walls of the roots of cotton and \u003cem\u003eJuncus effusus\u003c/em\u003e at high Cd concentrations (1000 \u0026micro;M) (Daud et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Najeeb et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Cd stress can adversely affect plant cellular structures and impair physiological metabolic functions. For instance, the morphology of root cells in \u003cem\u003eSesuvium portulacastrum\u003c/em\u003e exhibited deformation with increasing Cd treatment concentrations, including cell wall breakdown, cell membrane protrusions, vacuole contraction, mitochondrial and nuclear disassembly, and an increase in the number of starch granules (Uddin et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Similar ultrastructural alterations were observed in the root cells of two shrub species under high Cd stress (200 mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in this study. The cell structure of \u003cem\u003eB. sinica\u003c/em\u003e was severely altered under high Cd stress, with noticeable fracturing in cell arrangement. In contrast, the ultrastructural integrity of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e was less compromised, suggesting a stronger tolerance to Cd-contaminated soil.\u003c/p\u003e \u003cp\u003eThe binding and transformation of Cd in plants primarily occur within the cell walls, which are composed mainly of pectin, cellulose, hemicellulose, and proteins. Pectin and hemicellulose provide functional groups such as hydroxyl, carboxyl, amino, and aldehyde groups, which can adsorb and immobilize positively charged heavy metal ions, thereby limiting their entry into the plasma membrane (Lai \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Yu et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Analysis of the changes in characteristic peaks in FTIR spectra revealed that the cell wall of \u003cem\u003eB. sinica\u003c/em\u003e enhanced its adsorption capabilities for Cd ions by regulating the content of hydroxyl and amino functional groups, as well as soluble sugars. Additionally, in \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e, the presence of hydroxyl, amino, and carboxyl functional groups, along with soluble sugars in the cell walls, played a pivotal role in mitigating Cd toxicity. This finding corroborates previous studies suggesting that hydroxyl, amino, cyano, and carboxyl functional groups in cell walls can bind to Cd, contributing to tolerance against Cd in castor seedlings (He et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Hydroxyl, amino, and carboxyl functional groups have also been shown to be crucial for the tolerance and accumulation of Cd in the cell walls of \u003cem\u003eSolanum nigrum\u003c/em\u003e (Jia et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Wang et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Furthermore, hydroxyl, carboxyl, and amide groups may serve as the primary binding sites for Cd in the cell walls of \u003cem\u003eConyza canadensis\u003c/em\u003e seedlings (Yu et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Thus, the ability of \u003cem\u003eB. sinica\u003c/em\u003e and \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e to accumulate and tolerate Cd may be linked to the compartmentalization of plants, the adjustment of their chemical forms and subcellular distribution under stress, and the immobilization of Cd on the cell wall through functional groups.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eFrom the current study, we concluded that Cd stress inhibited the growth of \u003cem\u003eB. sinica\u003c/em\u003e, while it promoted growth at low Cd concentrations and inhibited it at high Cd concentrations in \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e. However, neither of the plants died under various Cd treatments. Additionally, considerable dark deposits were observed in the vacuoles as well as attached to the cell walls of the roots of both shrubs following Cd treatment. The cell structure of \u003cem\u003eB. sinica\u003c/em\u003e was severely altered under high Cd stress compared to that of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e. Observations of plant biomass and cellular microstructure indicated that \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e exhibited stronger resistance to Cd-contaminated soil than \u003cem\u003eB. sinica\u003c/em\u003e.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe content of chlorophyll a and carotenoids in the leaves of \u003cem\u003eB. sinica\u003c/em\u003e decreased with increasing Cd concentrations, while the content of chlorophyll b initially decreased and then increased as the Cd treatment gradient increased, showing significant differences compared to the control. In contrast, there were no remarkable differences in the chlorophyll a, chlorophyll b, and carotenoid content in the leaves of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e compared with the control. The plasma membrane permeability of various tissues in \u003cem\u003eB. sinica\u003c/em\u003e increased with higher Cd treatment gradients, whereas that of \u003cem\u003eL. \u0026times; vicaryi\u003c/em\u003e noticeably increased compared to the control only in the leaves. These results indicated that the photosynthetic pigments and plasma membrane permeability of all tissues in \u003cem\u003eB. sinica\u003c/em\u003e are more sensitive to Cd stress.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe Cd content in various organs of both shrubs increased with rising Cd treatment concentrations, with the highest levels found in the roots. In the roots of both shrubs, the NaCl-extracted state, which has moderate toxicity and mobility, was the predominant form of Cd, and the proportion and concentration of less toxic chemical forms increased with rising Cd concentrations. Moreover, both shrubs primarily accumulated Cd in the cell debris fraction of their roots, suggesting that they convert Cd to a less active form and retain it in the cell walls to mitigate its toxicity.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eFTIR spectroscopy revealed that certain functional groups, such as hydroxyl and amino groups, were involved in binding with Cd in the cell walls of both shrubs. Additionally, the results suggested that the two shrubs can absorb Cd through various functional groups to alleviate Cd toxicity.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":" \u003ch2\u003eCompeting interest\u003c/h2\u003e \u003cp\u003eThe authors have no relevant fnancial or non-fnancial interests to disclose.\u003c/p\u003e \u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis work was supported by the National Natural Science Foundation of China (31600574); Beijing Joint Construction Project; Beijing Forestry University to Build a World-Class Discipline and Guide the Development Special Fund (2019XKJS0322); Scientific Research and Postgraduate Training Joint Research Project of Beijing Education Commission (2019GJ-03). The authors thank all those who provided helpful suggestions and critical comments on this manuscript.\u003c/p\u003e \u003cp\u003e \u003cb\u003eAuthor Contributions\u003c/b\u003e Shiyin Yu, Shan Wang, Min Tang and Meixian Wang designed this research and revised the manuscript critically; Shan Wang, Shuzhen Pan, Min Tang and Meixian Wang conducted feld work and laboratory analysis; Shiyin Yu, Min Tang and Meixian Wang carried out the data analysis and drafted the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e \u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAkhter MF, Omelon CR, Gordon RA, Moser D, Macfie SM (2014) Localization and chemical speciation of cadmium in the roots of barley and lettuce. Environ Exp Bot 100:10\u0026ndash;19\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAli B, Qian P, Jin R, Ali S, Khan M, Aziz R, Tian T, Zhou W (2014) Physiological and ultra-structural changes in \u003cem\u003eBrassica napus\u003c/em\u003e seedlings induced by cadmium stress. Biol Plant 581:131\u0026ndash;138\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAli H, Khan E, Sajad MA (2013) Phytoremediation of heavy metals-Concepts and applications. Chemosphere 917:869\u0026ndash;881\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCapuana M (2011) Heavy metals and woody plants - biotechnologies for phytoremediation. iForest - Biogeosciences Forestry 41:7\u0026ndash;15\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCapuana M (2020) A review of the performance of woody and herbaceous ornamental plants for phytoremediation in urban areas. iForest - Biogeosciences Forestry 132:139\u0026ndash;151\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen H, Xia DS, Wang B, Liu H, Ma XY (2022) Pollution monitoring using the leaf-deposited particulates and magnetism of the leaves of 23 plant species in a semi-arid city, Northwest China. Environ Sci Pollut Res Int 2923:34898\u0026ndash;34911\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen XJ, Tao HF, Wu YZ, Xu XM (2022) Effects of cadmium on metabolism of photosynthetic pigment and photosynthetic system in \u003cem\u003eLactuca sativa\u003c/em\u003e L. revealed by physiological and proteomics analysis. Sci Hort 305:111371\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCherif J, Derbel N, Nakkach M, von Bergmann H, Jemal F, Ben Lakhdar Z (2012) Spectroscopic studies of photosynthetic responses of tomato plants to the interaction of zinc and cadmium toxicity. J Photochem Photobiology B: Biology 111:9\u0026ndash;16\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDaud MK, Ali S, Variath MT, Zhu SJ (2013) Differential physiological, ultramorphological and metabolic responses of cotton cultivars under cadmium stress. Chemosphere 9310:2593\u0026ndash;2602\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDezhban A, Shirvany A, Attarod P, Delshad M, Matinizadeh M, Khoshnevis M (2015) Cadmium and lead effects on chlorophyll fluorescence, chlorophyll pigments and proline of \u003cem\u003eRobinia pseudoacacia\u003c/em\u003e. J Forestry Res 262:323\u0026ndash;329\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDutta D, Pal AK, Gunri SK (2024) A Physiological Approach to Study the Interaction of Cadmium and Zinc in Groundnut (\u003cem\u003eArachis hypogaea\u003c/em\u003e L.) Seedlings. Legume Res 473:404\u0026ndash;409\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarooq A, Nadeem M, Abbas G, Shabbir A, Khalid MS, Javeed HMR, Saeed MF, Akram A, Younis A, Akhtar G (2020) Cadmium partitioning, physiological and oxidative stress responses in marigold (Calendula calypso) grown on contaminated soil: implications for phytoremediation. Bull Environ Contam Toxicol 1052:270\u0026ndash;276\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFern\u0026aacute;ndez R, Fern\u0026aacute;ndez-Fuego D, Bertrand A, Gonz\u0026aacute;lez A (2014) Strategies for Cd accumulation in \u003cem\u003eDittrichia viscosa\u003c/em\u003e (L.) Greuter: Role of the cell wall, non-protein thiols and organic acids. Plant Physiol Biochem 78:63\u0026ndash;70\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuo HB, Zhu N, Deyholos MK, Liu J, Zhang XR, Dong JE (2015) Calcium mobilization in salicylic acid-induced \u003cem\u003esalvia miltiorrhiza\u003c/em\u003e cell cultures and its effect on the accumulation of rosmarinic acid. Appl Biochem Biotechnol 1755:2689\u0026ndash;2702\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe CQ, Zhao YP, Wang FF, Oh K, Zhao ZZ, Wu CL, Zhang XY, Chen XP, Liu XY (2020) Phytoremediation of soil heavy metals (Cd and Zn) by castor seedlings: Tolerance, accumulation and subcellular distribution. Chemosphere 252\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe JL, Ma CF, Ma YL, Li H, Kang JQ, Liu TX, Polle A, Peng CH, Luo ZB (2013) Cadmium tolerance in six poplar species. Environ Sci Pollut Res 201:163\u0026ndash;174\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHe Y, Peng C, Zhang Y, Guo Z, Xiao X, Kong L (2023) Comparison of heavy metals in urban soil and dust in cities of China: characteristics and health risks. Int J Environ Sci Technol 202:2247\u0026ndash;2258\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHou XC, Teng WJ, Hu YX, Yang ZC, Li C, Scullion J, Guo Q, Zheng RL (2020) Potential phytoremediation of soil cadmium and zinc By diverse ornamental and energy grasses. BioResources 151:616\u0026ndash;640\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang F, Wen XH, Cai YX, Cai KZ (2018) Silicon-mediated enhancement of heavy metal tolerance in rice at different growth stages. Int J Environ Res Public Health 1510:2193\u0026ndash;2193\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang RZ, Jiang YB, Jia CH, Jiang SM, Yan XP (2018) Subcellular distribution and chemical forms of cadmium in \u003cem\u003eMorus alba\u003c/em\u003e L. Int J Phytoremediation 205:448\u0026ndash;453\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIori V, Pietrini F, Bianconi D, Mughini G, Massacci A, Zacchini M (2017) Analysis of biometric, physiological, and biochemical traits to evaluate the cadmium phytoremediation ability of eucalypt plants under hydroponics. iForest - Biogeosciences Forestry 101:416\u0026ndash;421\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJia HL, Wang XH, Wei T, Zhou R, Muhammad H, Hua L, Ren XH, Guo J, Ding YZ (2019) Accumulation and fixation of Cd by tomato cell wall pectin under Cd stress. Environ Exp Bot 167:103829\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJia L, Liu ZL, Chen W, Ye Y, Yu S, He XY (2015) Hormesis effects induced by cadmium on growth and photosynthetic performance in a hyperaccumulator, \u003cem\u003eLonicera japonica\u003c/em\u003e Thunb. J Plant Growth Regul 341:13\u0026ndash;21\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJia XY, Xia TX, Liang J, Li YD, Zhu XY, Zhang D, Wang JS (2023) Source apportionment of heavy metals based on multiple approaches for a proposed subway line in the southeast industrial district of Beijing, China. Int J Environ Res Public Health 201:683\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJia YX, Yue PX, Li KH, Xie YH, Li T, Pu YL, Xu XX, Wang GY, Zhang SR, Li Y, Luo X (2023) Mechanisms of cadmium tolerance and detoxification in two ornamental plants. Agronomy-Basel 138:2039\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJiang HM, Yang JC, Zhang JF (2007) Effects of external phosphorus on the cell ultrastructure and the chlorophyll content of maize under cadmium and zinc stress. Environ Pollut 1473:750\u0026ndash;756\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKaya C, Tuna AL, Sonmez O, Ince F, Higgs D (2009) Mitigation effects of silicon on maize plants grown at high zinc. J Plant Nutr 3210:1788\u0026ndash;1798\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKong XS, Zhao YX, Tian K, He XB, Jia YY, He ZH, Wang WW, Xiang CG, Tian XJ (2020) Insight into nitrogen and phosphorus enrichment on cadmium phytoextraction of hydroponically grown \u003cem\u003eSalix matsudana\u003c/em\u003e Koidz cuttings. Environ Sci Pollut Res 278:8406\u0026ndash;8417\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKonieczynski P, Zarkov A, Viapiana A, Kaszuba M, Bielski L, Wesolowski M (2020) Investigations of metallic elements and phenolics in Chinese medicinal plants. Open Chem 181:1381\u0026ndash;1390\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLai HY (2015) Subcellular distribution and chemical forms of cadmium in \u003cem\u003eImpatiens walleriana\u003c/em\u003e in relation to its phytoextraction potential. Chemosphere 138:370\u0026ndash;376\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi S, Lu S, Wang J, Chen ZC, Zhang Y, Duan J, Liu P, Wang XY, Guo JK (2023) Responses of Physiological, Morphological and Anatomical Traits to Abiotic Stress in Woody Plants. Forests 149:1784\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi TQ, Tao Q, Shohag MJI, Yang XE, Sparks DL, Liang YC (2015) Root cell wall polysaccharides are involved in cadmium hyperaccumulation in \u003cem\u003eSedum alfredii\u003c/em\u003e. Plant Soil 3891\u0026ndash;2:387\u0026ndash;399\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi XD, Ma H, Li LL, Gao YF, Li YZ, Xu H (2019) Subcellular distribution, chemical forms and physiological responses involved in cadmium tolerance and detoxification in \u003cem\u003eAgrocybe Aegerita\u003c/em\u003e. Ecotoxicol Environ Saf 171:66\u0026ndash;74\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi XX, Cui XW, Zhang X, Liu W, Cui ZJ (2020) Combined toxicity and detoxification of lead, cadmium and arsenic in \u003cem\u003eSolanum nigrum\u003c/em\u003e L. J Hazard Mater 389121874\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu SL, Ali S, Yang RJ, Tao JJ, Ren B (2019) A newly discovered Cd-hyperaccumulator \u003cem\u003eLantana camara\u003c/em\u003e L. J Hazard Mater 371:233\u0026ndash;242\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu ZL, He XY, Chen W, Yuan FH, Yan K, Tao DL (2009) Accumulation and tolerance characteristics of cadmium in a potential hyperaccumulator-\u003cem\u003eLonicera japonica\u003c/em\u003e Thunb. J Hazard Mater 1691\u0026ndash;3:170\u0026ndash;175\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLoix C, Huybrechts M, Vangronsveld J, Gielen M, Keunen E, Cuypers A (2017) Reciprocal interactions between cadmium-induced cell wall responses and oxidative stress in plants. Front Plant Sci 8:1867\u0026ndash;1867\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLu RR, Hu ZH, Zhang QL, Li YQ, Lin M, Wang XL, Wu XN, Yang JT, Zhang LQ, Jing YX, Peng CL (2020) The effect of \u003cem\u003eFunneliformis mosseae\u003c/em\u003e on the plant growth, Cd translocation and accumulation in the new Cd-hyperaccumulator \u003cem\u003eSphagneticola calendulacea\u003c/em\u003e. Ecotoxicol Environ Saf 203:110988\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLuo ZH, Tian DL, Ning C, Yan WD, Xiang WH, Peng CH (2015) Roles of \u003cem\u003eKoelreuteria bipinnata\u003c/em\u003e as a suitable accumulator tree species in remediating Mn, Zn, Pb, and Cd pollution on Mn mining wastelands in southern China. Environ Earth Sci 745:4549\u0026ndash;4559\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMa P, Zang J, Shao TY, Jiang QR, Li YQ, Zhang W, Liu MD (2023) Cadmium distribution and transformation in leaf cells involved in detoxification and tolerance in barley. Ecotoxicol Environ Saf 249:114391\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeng QH, Fan WH, Liu FW, Wang GL, Di XY (2024) Effect of Phosphorus Application on Subcellular Distribution and Chemical Morphology of Cadmium in Eggplant Seedlings under Cadmium Stress. Agronomy-Basel 145:932\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNajeeb U, Jilani G, Ali S, Sarwar M, Xu L, Zhou WJ (2011) Insights into cadmium induced physiological and ultra-structural disorders in \u003cem\u003ejuncus effusus\u003c/em\u003e L. and its remediation through exogenous citric acid. J Hazard Mater 1861:565\u0026ndash;574\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePan LB, Wang Y, Ma J, Hu Y, Su BY, Fang GL, Wang L, Xiang B (2018) A review of heavy metal pollution levels and health risk assessment of urban soils in Chinese cities. Environ Sci Pollut Res 252:1055\u0026ndash;1069\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRiaz M, Yan L, Wu XW, Hussain S, Aziz O, Wang YH, Imran M, Jiang CC (2018) Boron alleviates the aluminum toxicity in trifoliate orange by regulating antioxidant defense system and reducing root cell injury. J Environ Manage 208:149\u0026ndash;158\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRu SH, Xing JP, Su DC (2006) Rhizosphere cadmium speciation and mechanisms of cadmium tolerance in different oilseed rape species. J Plant Nutr 295:921\u0026ndash;932\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShen C, Fu HL, Liao Q, Huang BF, Huang YY, Xin JL (2021) Selection for low-cadmium cultivars and cadmium subcellular distribution comparison between two selected cultivars of eggplant (\u003cem\u003eSolanum melongena\u003c/em\u003e L). Environ Sci Pollut Res Int 2841:57739\u0026ndash;57750\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSpiridonova E, Ozolina N, Nesterkina I, Gurina V, Nurminsky V, Donskaya L, Tretyakova A (2019) Effect of cadmium on the roots of beetroot (\u003cem\u003eBeta vulgaris\u003c/em\u003e L). Int J Phytoremediation 2110:980\u0026ndash;984\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTong SM, Li HR, Wang L, Tudi M, Yang LS (2020) Concentration, Spatial Distribution, Contamination Degree and Human Health Risk Assessment of Heavy Metals in Urban Soils across China between 2003 and 2019-A Systematic Review. Int J Environ Res Public Health 179:3099\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUddin MM, Chen ZF, Huang LF (2020) Cadmium accumulation, subcellular distribution and chemical fractionation in hydroponically grown \u003cem\u003eSesuvium portulacastrum\u003c/em\u003e [Aizoaceae]. PLoS ONE 1512:e0244085\u0026ndash;e0244085\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUddin MM, Chen ZF, Xu FL, Huang LF (2023) Physiological and cellular ultrastructural responses of \u003cem\u003eSesuvium portulacastrum\u003c/em\u003e under Cd stress grown hydroponically. Plants-Basel 1219:3381\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang CR, Rong H, Zhang XB, Shi WJ, Hong X, Liu WC, Cao T, Yu XX, Yu QF (2020) Effects and mechanisms of foliar application of silicon and selenium composite sols on diminishing cadmium and lead translocation and affiliated physiological and biochemical responses in hybrid rice (\u003cem\u003eOryza sativa\u003c/em\u003e L.) exposed to cadmium and lead. Chemosphere 251:126347\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang JC, Chen XF, Chu SH, Hayat K, Chi YW, Zhi YE, Zhang D, Zhou P (2021) Influence of Cd toxicity on subcellular distribution, chemical forms, and physiological responses of cell wall components towards short-term Cd stress in \u003cem\u003eSolanum nigrum\u003c/em\u003e. Environ Sci Pollut Res 2811:13955\u0026ndash;13969\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang X, Liu YO, Zeng GM, Chai LY, Song XC, Min ZY, Xiao X (2008) Subcellular distribution and chemical forms of cadmium in \u003cem\u003eBechmeria nivea\u003c/em\u003e (L.) Gaud. Environ Exp Bot 623:389\u0026ndash;395\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang XL, Zhang BJ, Wu DS, Hu L, Huang T, Gao GQ, Huang S, Wu S (2021) Chemical forms governing Cd tolerance and detoxification in duckweed (\u003cem\u003eLandoltia punctata\u003c/em\u003e). Ecotoxicol Environ Saf 207:111553\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang YP, Huang J, Gao YZ (2012) Arbuscular mycorrhizal colonization alters subcellular distribution and chemical forms of cadmium in \u003cem\u003eMedicago sativa\u003c/em\u003e L. and resists cadmium toxicity. PLoS ONE 711:e48669\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWei SH, Zeng XF, Wang SS, Zhu JG, Ji DD, Li YM, Jiao HJ (2014) Hyperaccumulative property of \u003cem\u003eSolanum nigrum\u003c/em\u003e L. to Cd explored from cell membrane permeability, subcellular distribution, and chemical form. J Soils Sediments 143:558\u0026ndash;566\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWei SH, Zhou QX, Wang X, Zhang KS, Guo GL, Ma QYL (2005) A newly-discovered Cd-hyperaccumulator \u003cem\u003eSolanum nigrum\u003c/em\u003e L. Chin Sci Bull 501:33\u0026ndash;38\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeng BS, Xie XY, Weiss DJ, Liu JC, Lu HL, Yan CL (2012) \u003cem\u003eKandelia obovata\u003c/em\u003e (S., L.) Yong tolerance mechanisms to cadmium: subcellular distribution, chemical forms and thiol pools. Marine Pollution Bulletin 6411: 2453\u0026ndash;2460\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu HF, Wang JY, Li BB, Ou YJ, Wang JR, Shi QY, Jiang WS, Liu DH, Zou JH (2016) \u003cem\u003eSalix matsudana\u003c/em\u003e Koidz tolerance mechanisms to cadmium: uptake and accumulation, subcellular distribution, and chemical forms. Pol J Environ Stud 254:1739\u0026ndash;1747\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu HF, Wang JY, Ou YJ, Li BB, Jiang WS, Liu DH, Zou JH (2017) Characterisation of early responses to cadmium in roots of \u003cem\u003eSalix matsudana\u003c/em\u003e Koidz. Toxicol Environ Chem 995\u0026ndash;6:913\u0026ndash;925\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu QH, Wang SZ, Thangavel P, Li QF, Zheng H, Bai J, Qiu RL (2011) Phytostabilization potential of \u003cem\u003eJatropha Curcas\u003c/em\u003e L. in polymetallic acid mine tailings. Int J Phytoremediation 138:788\u0026ndash;804\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXin JP, Zhang Y, Tian RN (2018) Tolerance mechanism of \u003cem\u003eTriarrhena saccharifiora\u003c/em\u003e (Maxim.) Nakai. seedlings to lead and cadmium: Translocation, subcellular distribution, chemical forms and variations in leaf ultrastructure. Ecotoxicology and Environmental Safety 165: 611\u0026ndash;621\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang LP, Zhu J, Wang P, Zeng J, Tan R, Yang YZ, Liu ZM (2018) Effect of Cd on growth, physiological response, Cd subcellular distribution and chemical forms of \u003cem\u003eKoelreuteria paniculata\u003c/em\u003e. Ecotoxicol Environ Saf 160:10\u0026ndash;18\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang WD, Wang YY, Liu D, Hussain B, Ding ZL, Zhao FL, Yang XO (2020) Interactions between cadmium and zinc in uptake, accumulation and bioavailability for \u003cem\u003eSalix integra\u003c/em\u003e with respect to phytoremediation. Int J Phytoremediation 226:628\u0026ndash;637\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang Y, Zhang LQ, Huang X, Zhou YY, Quan QM, Li YX, Zhu XH (2020) Response of photosynthesis to different concentrations of heavy metals in \u003cem\u003eDavidia involucrata\u003c/em\u003e. PLoS ONE 153:e0228563\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYu HY, Guo JY, Li Q, Zhang XZ, Huang HG, Huang F, Yang AQ, Li TX (2020) Characteristics of cadmium immobilization in the cell wall of root in a cadmium-safe rice line (\u003cem\u003eOryza sativa\u003c/em\u003e L). Chemosphere 241:125095\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYu HY, Yang AQ, Wang KJ, Li Q, Ye DH, Huang HG, Zhang XZ, Wang YD, Zheng ZC, Li TX (2021) The role of polysaccharides functional groups in cadmium binding in root cell wall of a cadmium-safe rice line. Ecotoxicol Environ Saf 226112818\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYu SH, Sheng L, Mao HP, Huang XS, Luo LS, Li YY (2020) Physiological response of \u003cem\u003eConyza Canadensis\u003c/em\u003e to cadmium stress monitored by Fourier transform infrared spectroscopy and cadmium accumulation. Spectrochim Acta Part A Mol Biomol Spectrosc 229C:118007\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZakaria Z, Zulkafflee NS, Redzuan NAM, Selamat J, Ismail MR, Praveena SM, T\u0026oacute;th G, Razis AFA (2021) Understanding potential heavy metal contamination, absorption, translocation and accumulation in rice and human health risks. Plants-Basel 106:1070\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng P, Guo ZH, Cao X, Xiao XY, Liu YA, Shi L (2018) Phytostabilization potential of ornamental plants grown in soil contaminated with cadmium. Int J Phytoremediation 204:311\u0026ndash;320\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng P, Guo ZH, Xiao XY, Cao X, Peng C (2018) Response to cadmium and phytostabilization potential of \u003cem\u003ePlatycladus orientalis\u003c/em\u003e in contaminated soil. Int J Phytoremediation 2013:1337\u0026ndash;1345\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng P, Guo ZH, Xiao XY, Peng C, Liu LQ, Yan DM, He YL (2020) Physiological stress responses, mineral element uptake and phytoremediation potential of \u003cem\u003eMorus alba\u003c/em\u003e L. in cadmium-contaminated soil. Ecotoxicol Environ Saf 189:109973\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang JH, Guan YJ, Lin Q, Wang YX, Wu BW, Liu X, Wang B, Xia DS (2022) Spatiotemporal differences and ecological risk assessment of heavy metal pollution of roadside plant leaves in Baoji city. China Sustain 1410:5809\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang W, Zhao YL, Xu ZG, Huang HM, Zhou JK, Yang GY (2020) Morphological and physiological changes of \u003cem\u003eBroussonetia papyrifera\u003c/em\u003e seedlings in cadmium contaminated soil. Plants-Basel 912:1698\u0026ndash;1698\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao FJ, Lombi E, McGrath SP (2003) Assessing the potential for zinc and cadmium phytoremediation with the hyperaccumulator \u003cem\u003eThlaspi caerulescens\u003c/em\u003e. Plant Soil 2491:37\u0026ndash;43\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao HX, Wang LS, Zhao FJ, Wu LH, Liu AN, Xu WZ (2019) \u003cem\u003eSpHMA1\u003c/em\u003e is a chloroplast cadmium exporter protecting photochemical reactions in the Cd hyperaccumulator \u003cem\u003eSedum plumbizincicola\u003c/em\u003e. Plant Cell Environ 424:1112\u0026ndash;1124\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZheng MM, Feng D, Liu HJ, Yang GL (2023) Subcellular distribution, chemical forms of cadmium and rhizosphere microbial community in the process of cadmium hyperaccumulation in duckweed. Sci Total Environ 8592:160389\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZou JH, Wang YR, Wang SY, Shang XS (2023) Ca alleviated Cd-induced toxicity in \u003cem\u003eSalix matsudana\u003c/em\u003e by affecting Cd absorption, translocation, subcellular distribution, and chemical forms. J Plant Physiol 281:153926\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Cadium, Buxus sinica, Ligustrum × vicaryi, Physiological changes, Subcellular distribution, Chemical form","lastPublishedDoi":"10.21203/rs.3.rs-5311541/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5311541/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eBackground and aims \u003c/em\u003eUrban ornamental shrubs have significant potential for restoring cadmium (Cd)-contaminated soil. Simulated pot pollution was applied to\u003cem\u003e Buxus sinica \u003c/em\u003eand \u003cem\u003eLigustrum \u003c/em\u003e×\u003cem\u003e vicaryi\u003c/em\u003e to study their Cd enrichment characteristics and tolerance mechanisms.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMethods\u003c/em\u003e Cd content and accumulation were analyzed in different plant organs, subcellular distribution and chemical forms of Cd in the roots, and the effects of Cd on the ultrastructure of root cells under various Cd concentrations (0, 25, 50, 100, and 200 mg·kg⁻¹).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eResults \u003c/em\u003e(1) With increasing Cd treatment levels, the total biomass of \u003cem\u003eB. sinica\u003c/em\u003e gradually decreased, while\u003cem\u003e L. \u003c/em\u003e×\u003cem\u003evicaryi\u003c/em\u003e exhibited a stimulation effect at low Cd concentrations and inhibition at high Cd concentrations. (2) The Cd content in different organs of both shrubs increased with rising Cd levels, with \u003cem\u003eL.\u003c/em\u003e × \u003cem\u003evicaryi\u003c/em\u003e showing a significantly higher increase than \u003cem\u003eB. sinica, \u003c/em\u003eindicating a stronger Cd accumulation capability in \u003cem\u003eL.\u003c/em\u003e × \u003cem\u003evicaryi\u003c/em\u003e. (3) Cd in the root of both shrubs was primarily present in NaCl-extractable forms, and was majorly bound to the cell wall. (4) Excessive Cd caused damage to the cellular structure of \u003cem\u003eB. sinica\u003c/em\u003e leaves, while the cells of \u003cem\u003eL. \u003c/em\u003e× \u003cem\u003evicaryi\u003c/em\u003eleaves maintained normal morphology. (5) In both shrubs, Cd primarily binds to the cell wall through hydroxyl, amino functional groups, and soluble sugars.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConclusion\u003c/em\u003e Converting Cd to less active forms, immobilizing Cd in the cell wall, and providing binding sites through functional groups may be crucial resistance mechanisms for both shrubs in response to Cd stress.\u003c/p\u003e","manuscriptTitle":"Integrative study of subcellular distribution, chemical forms, and physiological responses for understanding cadmium tolerance in two garden shrubs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-25 11:42:42","doi":"10.21203/rs.3.rs-5311541/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2face92b-1e16-4fab-809d-28ec9c036a4b","owner":[],"postedDate":"October 25th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-10-27T12:30:05+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-25 11:42:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5311541","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5311541","identity":"rs-5311541","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}