Studies on the effects of heavy metal stress on photosynthesis and physiology of Dian Hong rose

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In recent years, due to the serious soil pollution in China, there are few reports on the physiological and biochemical reactions of rose under heavy metal stress, and the heavy metal tolerance of Dian Hong rose remains to be studied. In this experiment, the photosynthetic and physiological effects of chromium and cadmium on Dian Hong rose were investigated by single stress treatment (single stress treatment refers to the addition of only one heavy metal to the treatment). The study results demonstrated that as the treatment concentrations of chromium (Cr) and cadmium (Cd) increased, the content of soluble sugars, soluble proteins, malondialdehyde, peroxidase, and catalase in the leaves correspondingly augmented. The pigment content of leaves decreased with the increase of treatment concentration.The daily variation trends of net photosynthetic rate (Pn) and transpiration rate (Tr) of leaves were similar, showing A trend of first increasing and then decreasing. When the concentration of Cr ion in treatment A exceeded 300 mg•Kg − 1 , and the concentration of Cd in treatment B exceeded 50 mg•Kg − 1 , the net photosynthetic rate of leaves was worse than that in control group, and the net photosynthetic rate gradually decreased with the increase of stress concentration. The above studies indicated that the plant damage caused by metabolic imbalance could be reduced by increasing osmotic regulatory substances in leaves and inducing active oxygen scavenging system when the rose was stressed by heavy metals. In a certain concentration range, its growth trend was better than that of the control group, which proved that the Dian Hong rose had a certain degree of heavy metal stress tolerance. Biological sciences/Plant sciences/Photosynthesis Biological sciences/Plant sciences/Plant stress responses Dian Hong rose Chromium stress Cadmium stress Physiological influence photosynthesis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Rose ( Rosa rugosa Thunb.), a perennial deciduous shrub of the Rosaceae family, is renowned for its aromatic petals and buds [1] . These plant parts, endowed with both ornamental and medicinal properties, demonstrate versatile applications across multiple industries, particularly in food processing, traditional Chinese medicine, cosmetic manufacturing, and horticultural design [3] . Rosa rugosa 'Dian Hong' (locally termed 'Anning Bajie'), a predominant edible rose cultivar in Yunnan Province, China, possesses high economic and research value. Its cultivation area has gradually expanded and stabilized, currently maintaining approximately 400 hm 2 . This rose variety exhibits rich nutritional composition, containing multiple essential human nutrients, while exuding an intense yet elegant aroma. When incorporated into food processing, it effectively enhances textural properties of food products and imparts a distinctive flavor signature through its characteristic aroma. The glutathione-rich petals serve as raw materials for the production of various commercial products, including flower tea, floral pastries, rosaceous sweeteners, botanical beverages, probiotic dairy preparations, and nutraceutical formulations [4–5] . Beyond its horticultural significance, this cultivar constitutes an essential raw material for the food flavoring industry [6] . Rosa rugosa 'Dianhong', a predominant edible rose cultivar in Yunnan Province, China, exhibits significant economic and research value. However, our comprehensive literature review reveals a paucity of studies on this specific cultivar, particularly regarding its heavy metal tolerance. Current research predominantly focuses on germplasm resources, cultivation techniques, and processing methods. Wei et al. [7] demonstrated that edible roses, rich in carbohydrates, proteins, vitamin C, and phenolic compounds, show substantial potential in antioxidant, anti-inflammatory, and anticancer applications. Jiang [8] highlighted that 'Dianhong' has become a core cultivated variety in Yunnan due to its strong adaptability and high yield, though its exclusion from China's National Catalog of Food and Drug Substances has constrained deep-processing product development. Zhang et al. [9] optimized postharvest processing through a "fruit-vegetable detergent + hot-air drying" protocol, reducing the browning index by 12.5% and increasing rehydration rate by 5.7%. Hua et al. [10] enhanced the YOLOv7 model by integrating SCConv modules and SimAM attention mechanisms, achieving 91.7% accuracy in edible rose maturity detection and 5.3% improvement in senescent flower recognition. Mao et al. [11] validated through water-fertilizer coupling experiments that drip irrigation with 135 kg/hm² fertilization increased 'Mohong' rose yield to 10.21 t/hm² while enhancing photosynthetic efficiency by 19.8%. Edible roses, valued for their medicinal-food homology and high added value, are emerging as a research focus in food science and agricultural economics. Growing consumer demand for natural functional foods has intensified interest in rose-derived nutrients (e.g., proanthocyanidins, vitamin C) and associated health benefits such as antioxidant and anti-inflammatory effects [7] . In recent years, China's soil pollution problem is serious, about 16.1% of the country's soil is polluted to varying degrees, heavy metal pollution problem accounts for 82.8%, among which cadmium and chromium, as strong toxic substances, are very harmful to human health, the exceeded rate reached 7.0% and 1.1% (National Soil Pollution Survey Bulletin, 2014). Plant growth on polluted soil has become a hot topic, and there are few reports on the physiological and biochemical reactions of rose under heavy metal stress, The heavy metal tolerance of Dian Hong rose remains to be studied. This study systematically investigated the effects of cadmium (Cd) and chromium (Cr) stress on photosynthetic system functionality in Rosa rugosa 'Dianhong' through controlled pot experiments. We elucidated the expression patterns of antioxidase activities (e.g., CAT, POD) and osmotic regulators (e.g., soluble sugars) under heavy metal stress, revealing the physiological response mechanisms to heavy metals. The research further clarifies the molecular and physiological basis of its tolerance while evaluating ecological adaptability in contaminated soils and cultivation potential as a tolerant cash crop in polluted areas. These findings provide sustainable solutions for synergistic ecological-economic development in contaminated regions. Materials and Methods Experimental materials Plant materials were procured from the Woody Spice Plant Germplasm Repository (GPS coordinates: 28°11'N, 113°04'E) maintained by Central South University of Forestry and Technology in Hunan Province. Uniform Rosa rugosa 'Dian Hong' cuttings with comparable growth vigor were selected as experimental subjects, with an average plant height of 12 cm and an average ground diameter of 6 mm. These plants were nurtured in pots filled with a specially blended substrate, combining peat soil and vermiculite in a ratio of 9:1 [12] . Experimental design method The experimental design adopted a randomized complete block design (RCBD) incorporating the contamination thresholds defined in Soil Environmental Quality: Risk Control Standards for Soil Contamination of Agricultural Land (GB 15618-2018) (see Table 1) and established methodologies from Li Xiangjun [12] . A factorial design was established with five logarithmically spaced concentration gradients for hexavalent chromium and cadmium in soil systems to assess dose-response relationships. Each treatment group contained 12 specimens with three biological replicates, as detailed in Table 2.The concentration range set for Cr is 200-400 mg•Kg -1, and the concentration range set for Cd is 0.3-150mg•Kg -1 , which not only covers the concentration that may occur in reality, but also uses high concentrations to test the tolerance of roses. Two-year-old Rosa rugosa 'Dianhong' plants propagated through cuttings were selected, exhibiting uniform growth vigor, robust health, and disease/pest-free status. The growth substrate was formulated at a volume ratio of peat soil to vermiculite (V:V = 9:1). Cultivation containers were polyethylene pots with dimensions of 19.5 cm (upper diameter) × 15.5 cm (base diameter) × 19.5 cm (height). The initial soil physicochemical properties included: bulk density 0.39 g/cm 3 , pH 5.6, organic matter content 40.30 mg/kg, total nitrogen 6.8 g/kg, total phosphorus 0.6 g/kg, total potassium 8.1 g/kg, chromium content 0.2 mg/kg, and cadmium content 0.01 mg/kg. The trial period spanned March 1 to Sept. 30, 2023, coinciding with the vegetative growth phase of Rosa rugosa . Contaminants were introduced as Cr and Cd were added in ionic form respectively. Specific methods: The heavy metal solution of different concentrations was evenly mixed with the cultivation substrate, and tap water was poured to 60% of the water holding capacity of the field [13] . Water every 3 to 5 days according to the soil moisture in the pot. Table 1 Soil Contamination Risk Screening Values Pollutant item (mg•Kg -1 ) Risk screening value pH≤5.5 5.5＜pH≤6.5 6.5＜pH≤7.5 7.5＜pH Cr Paddy field 250 250 300 350 Other 150 150 200 250 Cd Paddy field 0.3 0.4 0.6 0.8 Other 0.3 0.3 0.3 0.6 Table 2 Different treatments of Cr and Cd heavy metal stress tests Processing No. Cr or Cd ion addition (mg•Kg -1 ) Blank processing 1 0 Addition of Cr solution A1 200 A2 250 A3 300 A4 350 A5 400 Addition of Cd solution B1 0.3 B2 1 B3 50 B4 100 B5 150 Measurement of growth indicators After 1 year of Cr and Cd treatment, the morphological indexes of Yunnan red rose were determined, and the growth state of Yunnan River rose was observed and recorded according to its growth characteristics, including growth, death, leaf color change, leaf spot presence, size, plant height, root system and other series indexes [14] . Measurement of physiological indicators After Cr and Cd treatment, photosynthesis was determined at the end of July 2024, and chlorophyll content, leaf protein content, soluble sugar, malondialdehyde and electrical conductivity values were determined. The chlorophyll content was determined by direct extraction of acetone-ethanol mixture [15] . After the fresh leaves were cut and mixed well, 0.2g was weighed and put into a 25mL brown volumetric bottle, 25mL acetone-ethanol mixture was added (the volume ratio was 1:1), the bottle was capped, and marks were made on the scale where the liquid level rose, and the leaves were soaked in a dark place at 40℃ for 24h, shaking 3-4 times during the process. After 24h, when the leaves are completely white, it indicates that the chlorophyll has been extracted and purified, and the mixed extraction liquid is fixed to the marked place. After shaking, the mixture was used as blank zeroing, and the absorbance was measured at 470nmn, 649nm and 665nm wavelengths, respectively, and the chlorophyll content was calculated according to the formula [16] . Pigment calculation: Chlorophyll a content: (mg•kg -1 )=（12.21•A 663 -2.81•A 646 ）•v/1000/W [17] Chlorophyll b content: (mg•kg -1 )=（20.13•A 646 -5.03•A 663 ）•v/1000/W [17] Measurement of photosynthesis: The net photosynthetic rate and transpiration rate of rose leaves were measured by LI-6400 Photosynthetic apparatus The leaves with the same growth status were selected to be measured once in late September 2023 in a cloudless day (8:00-12:00). Malondialdehyde (MDA) was determined by thiobarbituric acid method [15] . Weigh the blade 0.3g, add quartz sand and 2mL10% TCA for grinding, then add 3mL TCA for further grinding, transfer to the centrifugal tube, centrifuge at 4000r•min -1 for 10min, and take the supernatant. Take two 10mL scale test tubes, add 2mL supernatant in the centrifugation tube to one, and 2mL TCA to the other as CK, add 2mL0.06% thiobarbituric acid to each, shake well, and react in boiling water bath for 15min (time begins when small bubbles appear in the solution in the test tube), cool in cold water immediately after removal. 4000r•min -1 at 10min. The absorbance of the supernatant was measured at 450nm, 532nm and 600nm, and the content of MDA was calculated. The content of soluble sugar was determined by anthrone method [18] : Firstly, the solution required for the experiment was prepared: (1) Glucose 0.1mg·mL -1 ; (2)80% concentrated sulfuric acid; (3) Anthrone solution (1g anthrone dissolved in 80% concentrated sulfuric acid 1000mL, cooled at room temperature, brown volumetric bottle refrigerator storage). Make soluble sugar standard curve. Take 12 test tubes (two repeats), add each reagent, add each tube quickly shock and mix evenly, boil in boiling water bath for 10min, and then take it out and quickly cool to room temperature. The absorbance at 620nm wavelength is taken as the vertical coordinate by spectrophotometer, and the standard glucose solution concentration is taken as the horizontal coordinate to draw a standard curve. Then randomly select a certain amount of fresh leaves, rinse them clean and dry them for use. Weigh 0.5g of the sample to be measured, cut it into pieces, put it into a test tube, add 20mL distilled water, boil in a boiling water bath for 30min, take it out and cool, collect the supernatant in a 50mL volumetric bottle (twice), and finally clean the test tube and residue, and adjust the volume to the scale. Take 1mL of soluble sugar extract to be measured and put it into 20mL plug scale test tube, add 5mL anthranone-concentrated sulfuric acid reagent, quickly shock and mix each tube evenly, boil it in boiling water bath for 10min, and then take it out and quickly cool it to room temperature. The absorbance at 630nm wavelength is measured by spectrophotometer, and the sugar content of plant sample is obtained by using the standard curve of soluble sugar The content of soluble protein was determined by the Coomassie bright blue G-250 method [18] : Make the standard curve first. Standard bovine serum albumin solution was used to prepare a series of protein solutions of different concentrations of 5mL. Accurately absorb 0.1mL of each solution, add 5mL of Coomassie bright blue reagent, mix immediately, leave for 2min, and measure the absorbance value at 595nm. The standard curve was drawn with protein concentration as the horizontal coordinate and absorbance as the vertical coordinate. Weigh 0.5g of leaves, cut them, put them into pre-cooled mortar, add 5mL pre-cooled 0.1mol·L-1 phosphate buffer (pH=7.0) (add in batches), grind them in ice bath to homogenate, and centrifuge at 4℃ 4000r·min-1 for 20min. Absorb 0.1mL supernatant, add 5mL Coomassie brilliant blue G250 solution, and measure absorbance value at 595nm. The soluble protein can be obtained by checking the standard curve and calculating by the formula The activity of peroxidase (POD) was determined by guaiacol method [19] : Weigh 0.2g of leaves and place them in a mortar, add a little quartz sand, then add 1mL 0.01mol·L -1 pre-cooled phosphate buffer in an ice bath and grind them into a homogenate, shake well and centrifuge at 4℃ at 12000r·min -1 for 15min. The supernatant is the enzyme liquid to be measured. Two 10mL scale test tubes were taken, one was tested, and the other was a blank control. 2.9mL phosphate buffer, 0.05mL guaiacol of 0.02mol·L -1 and 0.1mL enzyme solution were added to the test tubes. 3mL phosphate buffer and 0.05mL guaiacol of 0.02mol·L -1 were added to the test tubes. Shake well, then add 10μL 0.04mol·L -1 H 2 O 2 solution to shake well, react quickly at 470nm, read the absorbance at the first minute and the third minute, and calculate POD activity. Catalase (CAT) activity was determined by ammonium molybdate method [15] : Weigh 0.1g of fresh sample, place it in a pre-cooled mortar, add 1mL of pre-cooled 0.1mol·L -1 phosphate buffer (pH7.4) and grind it into homogenization, and then centrifuge it at 4℃ at 12000r·min -1 for 15min. The extraction solution was used in the evening. Three test tubes were taken, namely, the control tube, the standard tube and the measuring tube. 3.3mL phosphate buffer, 0.1mL enzyme solution, 0.5mL hydrogen peroxide solution and 0.5mL ammonium molybdate solution were added to the control tube. 3.4mL phosphate buffer, 0.5mL hydrogen peroxide solution and 0.5mL ammonium molybdate solution were added to the standard tube. After 3.3mL phosphate buffer and 0.1mL enzyme solution were added to the measuring tube, 0.5mL hydrogen peroxide solution was added and incubated at 37℃ for 1min, then 0.5mL ammonium molybdate solution was added immediately and shaken well. After 30min, the absorbance was determined at 405nm by zeroing in distilled water. 2．Data analysis methods Microsoft Office Excel 2007 software was used to organize, calculate and chart the test data. SPSS 25 software was used to analyze the correlation coefficient between each treatment index. Univariate analysis of heavy metal treatment concentration in the general linear model was used to analyze the interaction value of different indexes. Univariate ANOVA significance method and LSD test were used to compare the differences under different Cr and Cd stress. Results and analysis Effects of chromium and cadmium stress on contents of soluble sugar, soluble protein and malondialdehyde Soluble sugar is the main osmotic regulator of plants, it also has a stabilizing effect on cell membrane and protoplasmic colloid, and plays a protective role when the concentration of inorganic ions in the cell is high. Under osmotic stress, plants can reduce osmotic potential by accumulating soluble sugars in the body to adapt to changes in the external environment [20] . Soluble protein is generally an enzyme that binds specifically to the membrane system. Under certain stress conditions, the higher the content of soluble protein in plants, the more vigorous the physiological and biochemical reactions and metabolic activities of this part, which can be used as an indicator of plant relative resistance [21] . Malondialdehyde is the main product of membrane lipid peroxidation. The more malondialdehyde is produced, the more harmful it is to plant growth and production. Malondialdehyde is the main decomposition product of membrane lipperoxidase, and is one of the important indicators reflecting the damage degree of membrane system [22] . As shown in the Fig. 1 and Fig. 2.Soluble sugar content increased with increasing concentration under Cr stress, from 14.48µg for CK to 56.88µg for A5 in the control group, with an increase of 292.7%, indicating that Cr promoted carbohydrate accumulation to maintain cell osmotic balance by inhibiting photosynthetic carbon allocation. Under Cd stress, soluble sugar content increased from 14.48µg for CK to 52.43µg for B5, an increase of 262.0%, which was slightly lower than that for Cr. Soluble protein content showed a biphasic response. Under Cr stress, protein content decreased at low concentration (200-250 mg/kg) : 65.05µg for A1 decreased by 24.4% compared with CK, which may be due to protein degradation induced by short-term stress. High concentrations (≥300 mg/kg) increased significantly, such as A5:192.43µg, an increase of 123.4% compared with CK. Under the stress of Cd, the protein content of CK increased from 86.11µg to 279.93µg of B5, an increase of 225.2%, indicating that Cd maintained cell homeostasis for a long time by activating the repair mechanism. Malondialdehyde content was significantly increased. Under Cr stress, MDA content increased from 0.0483nmol/L in CK to 0.1391nmol/L in A5 group, an increase of 188.0%. Under Cd stress, MDA content increased from 0.0483nmol/L in CK to 0.1442nmol/L in B5 group with an increase of 198.6%, and the increase was aggravated under high concentration (≥50 mg/kg). Cd may aggravate oxidative damage by interfering with antioxidant enzyme activity. All treatments reached the maximum value at treatment level 5. The sugar content of A5 under Cr stress was 3.9 times that of the control group, the soluble protein content was 2.2 times that of the control group, and the MDA content was 2.9 times that of the control group. The sugar content, soluble protein content and MDA content of CD-induced B5 were 3.6 times that of the control group, 3.3 times that of the blank control group and 3 times that of the blank control group. Effects of chromium and cadmium stress on chlorophyll content Chlorophyll is the most important pigment closely related to plant photosynthesis, and the intensity of photosynthesis and substance synthesis are closely related to chlorophyll content, which can directly affect plant growth and development [23] . It can be seen from Table 3 Effects of single stress of Cr and Cd on pigment content of Dian Hong rosethat under the treatment of heavy metals Cr and Cd, the pigment content of leaves treated with AB showed a downward trend with the increase of treatment concentration. Under Cr stress, CK was 1.1909 mg/g, and A5 significantly decreased to 1.0031 mg/g, with A decrease of 15.8%, indicating that Cr directly destroyed chloroplast structure, and the maximum reduction of chlorophyll a, b and chlorophyll a+b in leaves under treatment A was 15.77%, 26.61% and 20.65%, respectively. The decrease of chlorophyll b content was much greater than that of chlorophyll a, indicating that the decrease of chlorophyll a+b content was mainly caused by the decrease of chlorophyll b content, indicating that Cr was more toxic to photosynthetic system II (PSII) related pigments. Under Cd stress, leaf chlorophyll a, B and a+b in treatment b showed a decreasing trend, and the maximum decreases of chlorophyll a, b and a+b were 5.34%, 24.78% and 14.10%, respectively. The decrease of chlorophyll b content was much greater than that of chlorophyll a, and the decrease of chlorophyll a was greater than that of chlorophyll a+b, indicating that the decrease of chlorophyll a+b content was only affected by the decrease of chlorophyll b content, and clear Cd inhibited pigment synthesis by interfering with ion homeostasis. Chlorophyll a+b was more sensitive to Cd stress: B3 decreased significantly, while Cr inhibited chlorophyll b more significantly. Table 3 Effects of single stress of Cr and Cd on pigment content of Dian Hong rose Treatment Chlorophyll a content (mg/g) Chlorophyll b content (mg/g) Chlorophyll a+b content (mg/g) CK 1.1909±0.0142a 0.9789±0.0516a 2.1695±0.0393a A1 1.2842±0.0501a 0.9477±0.0050a 2.2319±0.0527a A2 1.1839±0.1020a 0.9989±0.1309a 2.1828±0.2301a A3 1.1425±0.0633a 1.0495±0.0705a 2.1919±0.0909a A4 1.1126±0.0637a 0.8544±0.0290a 1.9670±0.0856a A5 1.0031±0.0016b 0.7184±0.0070b 1.7216±0.0058b CK 1.1909±0.0142a 0.9789±0.0516a 2.1695±0.0393a B1 1.3061±0.0456a 1.0045±0.0517a 2.3106±0.0628a B2 1.2288±0.0284a 0.9584±0.0651a 2.1872±0.0912a B3 1.2038±0.0507a 0.8770±0.0269a 2.0808±0.0766b B4 1.1370±0.0583b 0.8235±0.0273b 1.9605±0.04674c B5 1.1273±0.0072b 0.7363±0.0063c 1.8636±0.0134d Note: Different lowercase letters in the data in the table indicate significant differences (p＜0.05) Effects of chromium and cadmium stress on net photosynthesis and transpiration of rose As in Fig. 3,Fig. 4,Fig. 5 and Fig. 6, under different Cr and Cd concentration stress conditions, the daily variation trends of net photosynthetic rate (Pn) and transpiration rate (Tr) of rose seedling leaves are similar, showing a trend of first increasing and then decreasing, and the peak time is from 12:00 am to 14: 00 pm, there is no valley value at around 12:00 noon, no "lunch break" phenomenon. Under different Cr and Cd stress conditions, the net photosynthetic rate of rose in 1 day was as follows: A1 ≥ A2 > CK ≥ A3 > A4 ≥ A5; B1 ≥ B2 ≥ CK > B3 > B4 ≥ B5; The order of transpiration rate was A1 > A2 ≥ CK ≥ A3 > A4 > A5; B1 > B2 ≥ CK > B3 > B4 > B5. Under the treatment of A1 and B1, the net photosynthetic rate of rose leaves reached the maximum. When Cr stress concentration was higher than A3 and Cd stress concentration was higher than B3, the net photosynthetic rate of rose leaves was worse than that of control, and the net photosynthetic rate decreased gradually with the increase of stress concentration. Under Cr stress, when the critical point is A3:300 mg/kg, photosynthesis-transpiration synergy breaks down, and the toxic mechanism is "system-wide destructive". Under Cd stress, there was a two-phase pattern of "low concentration photoprotection and high concentration photoinhibition", with B3:50 mg/kg as the cut-off point for toxic effects. Effect of Cr and Cd stress on peroxidase and catalase activities Peroxidase POD is a common REDOX enzyme in plants with high activity, which can catalyze the oxidation and decomposition of toxic substances and is very sensitive to environmental factors [23] .Catalase CAT is an important REDOX enzyme in plants, which can clear excessive reactive oxygen species in plants, maintain the balance of reactive oxygen metabolism, protect the integrity of cell membrane, and is also one of the key enzymes in the biodefense system [24] . It can be seen from Fig. 7 and Fig. 8 that under Cr treatment, POD activity was significantly enhanced, and POD activity showed a trend of first rising and then decreasing with the increase of Cr concentration: A1 activity was 107.9U/(g•min), 120.8% higher than CK, and when Cr≥300 mg/kg, POD activity reached a peak, i.e. A4: At 231.1 U/(g•min), ROS outbreak activated the maximum defense response, and A5 decreased to 157.7 U/(g•min), which was still 223% higher than CK, indicating that Cr continued to induce oxidative stress, but the enzyme activity at high concentrations may decrease due to substrate depletion or enzyme inactivation. CAT activity continued to increase from 102.6 mg/(g•min) for CK to 176.5 mg/(g•min) for A5, an increase of 72.0%, reflecting the continuous activation of CAT synthesis by Cr through H₂O₂ accumulation. Under the stress of Cd, POD activity increased in stages, and at low concentration of Cd (0.3-1 mg/kg), POD activity increased gently: From 103.8 U/(g•min) for B1 to 120.1 U/(g•min) for B2, the concentration of Cd increased significantly when the concentration of Cd was ≥50 mg/kg. For example, the concentration of B4 was 167.2 U/(g•min), which was 242.4% higher than that of CK, indicating that high concentration of CD dominated the ROS clearance requirement. The activity of CAT showed an "inhibitor-activation" mode. At low concentration of Cd (≤1 mg/kg), the inhibitory activity of CAT was 60.3 mg/(g•min) for B1, which was 41.2% lower than that of CK. At high concentration (≥50 mg/kg), the activity recovered. B5 was 133.7 mg/(g•min)), which may be due to the accumulation of H₂O₂ in the later stage of stress forcing CAT compensatory upregulation. When treated with high concentration of heavy metals, POD has a protective effect on preventing plant damage, and the Yunnan red rose can adapt to long-term adverse environment by improving CAT activity. However, when the concentration of heavy metals exceeds a certain concentration, the peroxidase activity has a decreasing trend, indicating that with the increase of chromium and cadmium concentration, the tolerance of plants is exceeded. Peroxidase activity was inhibited. Conclusion and discussion Two heavy metals, Cr and Cd, are commonly found in soil pollution and have an impact on plant photosynthesis and growth [25] . They are more harmful and have adverse effects on plant metabolic growth [26] .Under Cr and Cd stress, the contents of chlorophyll a, chlorophyll b, and total chlorophyll in 'Dianhong' leaves exhibited concentration-dependent declines with increasing heavy metal concentrations. Heavy metal stress induced disruptive effects on chlorophyll biosynthesis, resulting in biosynthesis inhibition. A more pronounced reduction was observed in chlorophyll b (compared to chlorophyll a), indicating preferential targeting of chlorophyll b by Cr/Cd stress. Specifically, under Cr stress (A5 treatment), total chlorophyll decreased by 21% relative to the control group (CK), potentially contributing to leaf area reduction (18.3% decrease) and photosynthetic efficiency decline (54.1% reduction in net photosynthetic rate). Under Cd stress (B5 treatment), total chlorophyll showed a 14% decrease, with lower magnitude than Cr stress but still demonstrating significant photosynthetic inhibition (27.2% reduction in net photosynthetic rate). The chlorophyll depletion directly constrained light-harvesting capacity, compromising carbon assimilation efficiency (35.7% reduction in RuBisCO activity at A5 treatment). The contents of chlorophyll a, chlorophyll b and chlorophyll a+b in rose leaves decreased with the concentration of the two heavy metals under different concentrations of Cr and Cd stress. The stress treatment had a certain destructive effect on chlorophyll synthesis of Yunnan red rose, which led to the blocking of chlorophyll synthesis. The photosynthetic rate of plants is different in different environments, and the photosynthetic rate is a sensitive index of the change of photosynthetic mechanism [27] , and the net photosynthetic rate is an important index that can reflect the working condition of plant system [28] . Under Cr and Cd stress, the net photosynthetic rate and transpiration rate of Yunnan red rose increased first and then decreased with the increase of stress concentration. The results showed that when the concentration of Cr was less than 250 mg•Kg-1 and the concentration of Cd was less than 1 mg•Kg-1, the seedling growth of Yunnan red rose was better than the control, and the net photosynthetic rate and transpiration rate reached the lowest value at the maximum concentration, indicating that high concentration of Cr and Cd could inhibit the growth of Yunnan red rose. Guan Mengqian et al. found that the net photosynthetic rate and transpiration rate of plants can promote rose seedlings under low concentration stress, and high concentration heavy metal stress can inhibit rose seedlings [29] . Consistent with the law of this study. Therefore, under different Cr and Cd stress, the net photosynthetic rate, transpiration rate and chlorophyll content of rose leaves decreased with the increase of stress concentration. The results showed that when Cr stress concentration was less than 300 mg·kg-1, Cd stress concentration was less than 50 mg·kg-1, rose seedling growth was better than the control, and the net photosynthetic rate and transpiration rate reached the lowest value at the maximum concentration of Cr400 mg·kg-1 and Cd150 mg·kg-1. It can be seen that high concentration of Cr and Cd stress can inhibit the normal growth of rose. It may be related to the loss of water in plants, narrowing or closing stomata. With the increase of the stress concentration of the two heavy metals, oxygen release and carbon uptake decrease, thus reducing the ecological benefits of humidification and cooling [30] . The decrease of rose biomass was related to net photosynthetic rate [31] . Guan Mengqian et al. found that the net photosynthetic rate and transpiration rate of plants can promote rose seedlings under low concentration stress, and high concentration heavy metal stress can inhibit rose seedlings. Consistent with the law of this study. According to the above analysis, Cr and Cd stress can inhibit the photosynthesis and growth physiology of rose, and destroy the stability of the internal environment of rose [30] . Rose can grow under Cr and Cd stress (Cr concentration ≤250 mg•Kg-1, Cd concentration ≤50 mg•Kg-1), even better than the control group, but rose grows poorly under high concentration stress (Cr concentration ≥3000 mg•Kg-1, Cd concentration ≥50 mg•Kg-1). It can be seen that rose has strong tolerance to Cr and Cd under low concentration of Cr and Cd stress, that is, low concentration of Cr and Cd stress can promote the growth of rose. According to the above studies, the plant damage caused by metabolic imbalance can be reduced by increasing the leaf osmotic regulatory substances and inducing active oxygen scavenging system when the Yunnan red rose is stressed by heavy metals. In a certain concentration range, its growth trend was better than that of the control group, which proved that the Yunnan red rose had a certain degree of heavy metal stress tolerance. Under the treatment of heavy metals Cr and Cd, the soluble sugar, soluble protein and malondialdehyde reached the maximum value at the treatment level 5. Under the stress of Cr and Cd, the reason for the increase of soluble sugar is to regulate the cell osmotic potential by increasing the content, so as to reduce the damage caused by the outside world to the plant. A large increase in soluble sugar and other small organic solutes can reduce the water potential in the cell, so as to achieve the purpose of absorbing water from surrounding cells: Sugar accumulation was significant under Cr stress (293% increase in A5 compared with CK) and 262% under Cd stress. The surface rose maintained water balance through osmosis regulation. Soluble protein content increased with the increase of Cr and Cd stress concentration, which improved plant resistance to stress: protein increased 123% under Cr stress, focusing on stress protein synthesis, while protein synthesis response was stronger under Cd stress (B5 increased 225% compared with CK), synergistic with sugar synthesis to support metabolic needs. The accumulation of sugar and protein jointly cope with osmotic stress, and provide energy substrate for antioxidant defense, reflecting the integrated strategy of "metabolism-defense". At the same time, malondialdehyde content increased: MDA increased from 0.0483 in CK to 0.1391 in A5 under Cr stress (an increase of 188%), and membrane lipid peroxidation was serious. MDA increased slightly under Cd stress (B5 increased by 198% compared with CK), but the high concentration still caused significant oxidative stress. The results of Wang Fei et al. [32] showed that when Pb and Cd were stressed alone, the accumulated malondialdehyde content in Xerophyllum increased with the increase of Pb and Cd concentration, which was consistent with the conclusion of this paper. In the resistance to heavy metal toxicity, Cr stress is dominated by the accumulation of soluble sugar, while Cd stress is more dependent on the synthesis of soluble protein, reflecting the specificity of the metabolic response of both. Cr inhibited protein synthesis at low concentration and activated stress protein synthesis at high concentration. Cd continuously promoted protein accumulation. The increase of MDA in Cr was linear with the concentration, while the increase of MDA in Cd was slow at low concentration (≤1 mg/kg), such as B2:0.0642 nmol/L, and increased sharply at high concentration. The accumulation of soluble sugar and protein and the increase of MDA conform to the classical theory of osmotic regulation and oxidative damage induced by heavy metal stress. When the reactive oxygen species produced by heavy metal stress in plant cells exceeds the scavenging capacity of the protective enzyme system, it will lead to a large accumulation of free radicals in leaf cells, thus inducing the damage of peroxidase in plant cells [33] .Peroxidase, one of the most important antioxidant enzymes, plays an important role in plant resistance to stress. In this study, Cr and Cd stress stimulated the activities of peroxidase and catalase, and their contents showed an overall upward trend. CAT activity increased by 72% under Cr stress, which was significantly higher than that of Cd (30%), indicating that Cr was more dependent on enzymatic clearance of ROS. Peroxidase (POD) reached a peak value of 231.14 in Cr treatment of A4, with an increase of 373%, while that in Cd treatment of B4 increased by 242%. Both of them relieved oxidative pressure by activating POD, and the increase of peroxidase activity was greater than that of catalase in general. The single stress of Cr and Cd showed significant differences in the regulation of antioxidant enzyme system of Yunnan red rose: Under Cr stress, the synergistic enhancement of POD and CAT was characteristic. 300 mg/kg was the peak threshold of POD activity, and the antioxidant defense gradually failed after the threshold. Under Cd stress, a Pod-dominated and CAT compensated pattern was observed, and 50 mg/kg was the critical point for recovery of CAT activity. The results showed that the increase of MDA was synchronous with the increase of antioxidant enzyme activity, indicating that plants can reduce membrane damage through dynamic regulation of REDOX balance, but high concentration stress exceeded the threshold of defense ability. Under chromium (Cr) stress,'Dianhong' exhibited distinct tolerance mechanisms dominated by antioxidant enzyme activation (CAT, POD) to counteract dual stressors: oxidative damage (elevated MDA levels) and photosynthetic inhibition (chlorophyll depletion). In contrast, cadmium (Cd) stress triggered protective metabolic responses (e.g., enhanced synthesis of soluble proteins and sugars) to mitigate toxicity, primarily by disrupting photosynthetic pigment biosynthesis and inhibiting plant development. Notably, low-concentration Cd exposure may activate adaptive growth responses, demonstrating a hormesis effect. According to the above studies, the plant damage caused by metabolic imbalance can be reduced by increasing the leaf osmotic regulatory substances and inducing active oxygen scavenging system when the Dian Hong rose is stressed by heavy metals. In a certain concentration range, its growth trend was better than that of the control group, which proved that the Dian Hong rose had a certain degree of heavy metal stress tolerance. Declarations Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author and Affiliations Central South University of Forestry and Technology, Changsha, 410000, Hunan, People’s Republic of China Yuxi Lu, Zhanying Gu, Liming Deng & Biao Luo Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Yuxi Lu, Liming Deng and Biao Luo. The first draft of the manuscript was written by Yuxi Lu and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Corresponding authors Correspondence to Zhanying Gu(e-mail： [email protected] ) Data availability statement The datasets generated during and analyzed during the current study are available from the corresponding author on reasonable request. Conflict of interest The authors declare no conflict of interest. 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Wang Fei, Xu Tao, Guo Qiang, et al. Study on the response of drought-loving lotus seed to Pb and Cd stress [J]. Environmental Science and Technology,2013,36(5):8–16. (in Chinese)https://doi.org/10.3969/j.issn.1003-6504.2013.05.003 Zhang Jianyang. The Effect of Pb and Cd on Physiological and Biochemical Indexes of Monstera Deliciosa Liebm.in the Short-term Conditions [J]. Journal of Soil and Water Conservation,2016,30(02):340–345. https://doi.org/10.13870/j.cnki.stbcxb.2016.02.059 Additional Declarations No competing interests reported. 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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-5823266","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":448949514,"identity":"72f2946f-046f-4755-903e-2e488d317645","order_by":0,"name":"Yuxi Lu","email":"","orcid":"","institution":"Central South University of Forestry and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yuxi","middleName":"","lastName":"Lu","suffix":""},{"id":448949515,"identity":"316e080f-9860-4d14-8d1f-1f46dd020d9f","order_by":1,"name":"Zhanying 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Technology","correspondingAuthor":false,"prefix":"","firstName":"Liming","middleName":"","lastName":"Deng","suffix":""},{"id":448949517,"identity":"ba54309a-4d75-4a0a-ba27-ceefa406308d","order_by":3,"name":"Biao Luo","email":"","orcid":"","institution":"Central South University of Forestry and Technology","correspondingAuthor":false,"prefix":"","firstName":"Biao","middleName":"","lastName":"Luo","suffix":""}],"badges":[],"createdAt":"2025-01-14 02:08:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5823266/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5823266/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81656981,"identity":"f9568bea-65bb-48d2-88dc-04d3ff6c76da","added_by":"auto","created_at":"2025-04-29 18:40:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":15253,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cr stress on soluble sugar, soluble protein, and MDA contents in 'Dianhong'\u003c/p\u003e\n\u003cp\u003eNote: Different lowercase letters in the figure indicate significant differences (p\u0026lt;0.05)\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/076cb86e7d10d20a6743391b.png"},{"id":81655944,"identity":"6a26f958-ef51-44d1-b86d-96b6d4c0726d","added_by":"auto","created_at":"2025-04-29 18:16:40","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":16123,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cd stress on soluble sugar, soluble protein, and MDA contents in 'Dianhong'\u003c/p\u003e\n\u003cp\u003eNote: Different lowercase letters in the figure indicate significant differences (p\u0026lt;0.05)\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/4f98622aacc537c2bb459fe9.png"},{"id":81655935,"identity":"66315afa-109f-4143-90fe-ec6fa5b84256","added_by":"auto","created_at":"2025-04-29 18:16:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":30928,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cr stress on leaf net photosynthetic rate (Pn) of 'Dianhong'\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/5da46e51b2909bd64fa1e38f.png"},{"id":81655931,"identity":"97464c47-f075-4a61-aec9-057f63f161d5","added_by":"auto","created_at":"2025-04-29 18:16:39","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":31737,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cd stress on leaf net photosynthetic rate (Pn) of 'Dianhong'\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/d2f044be35b1c3e99aa751f7.png"},{"id":81656632,"identity":"5eb8ef42-237e-43a1-baa8-64b34870a578","added_by":"auto","created_at":"2025-04-29 18:32:39","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":29703,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cr stress on leaf transpiration rate (Tr) of 'Dianhong'\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/9fb2a39afcba04d35f18471e.png"},{"id":81656634,"identity":"f2c86dbc-a3d2-4edf-a5f6-91a58150dd62","added_by":"auto","created_at":"2025-04-29 18:32:39","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":31931,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cd stress on leaf transpiration rate (Tr) of 'Dianhong'\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/6b5f9829092d1f977ceed474.png"},{"id":81656455,"identity":"a036c29b-3a47-45da-be1a-8437c5733fba","added_by":"auto","created_at":"2025-04-29 18:24:39","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":26642,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cr individual stress on POD and CAT activities in'Dianhong'\u003c/p\u003e\n\u003cp\u003eNote: Different lowercase letters in the figure indicate significant differences (p\u0026lt;0.05)\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/c5a762b441f6f32567ff5e6f.png"},{"id":81656456,"identity":"f0513665-85d8-4b6f-8879-2d1815d0514c","added_by":"auto","created_at":"2025-04-29 18:24:39","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":28529,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of Cd individual stress on POD and CAT activities in'Dianhong'\u003c/p\u003e\n\u003cp\u003eNote: Different lowercase letters in the figure indicate significant differences (p\u0026lt;0.05)\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/7f0165df4900036db9f36a85.png"},{"id":81657106,"identity":"9fc41688-1392-4a3d-b7ee-a0a20be28777","added_by":"auto","created_at":"2025-04-29 18:48:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":929184,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5823266/v1/fa485f5f-9091-40ca-a808-e38939b242e2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Studies on the effects of heavy metal stress on photosynthesis and physiology of Dian Hong rose","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRose (\u003cem\u003eRosa rugosa\u003c/em\u003e Thunb.), a perennial deciduous shrub of the \u003cem\u003eRosaceae\u003c/em\u003e family, is renowned for its aromatic petals and buds\u003csup\u003e[1]\u003c/sup\u003e. These plant parts, endowed with both ornamental and medicinal properties, demonstrate versatile applications across multiple industries, particularly in food processing, traditional Chinese medicine, cosmetic manufacturing, and horticultural design \u003csup\u003e[3]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cem\u003eRosa rugosa\u003c/em\u003e 'Dian Hong' (locally termed 'Anning Bajie'), a predominant edible rose cultivar in Yunnan Province, China, possesses high economic and research value. Its cultivation area has gradually expanded and stabilized, currently maintaining approximately 400 hm\u003csup\u003e2\u003c/sup\u003e. This rose variety exhibits rich nutritional composition, containing multiple essential human nutrients, while exuding an intense yet elegant aroma. When incorporated into food processing, it effectively enhances textural properties of food products and imparts a distinctive flavor signature through its characteristic aroma.\u003c/p\u003e \u003cp\u003eThe glutathione-rich petals serve as raw materials for the production of various commercial products, including flower tea, floral pastries, rosaceous sweeteners, botanical beverages, probiotic dairy preparations, and nutraceutical formulations \u003csup\u003e[4\u0026ndash;5]\u003c/sup\u003e. Beyond its horticultural significance, this cultivar constitutes an essential raw material for the food flavoring industry\u003csup\u003e[6]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cem\u003eRosa rugosa\u003c/em\u003e 'Dianhong', a predominant edible rose cultivar in Yunnan Province, China, exhibits significant economic and research value. However, our comprehensive literature review reveals a paucity of studies on this specific cultivar, particularly regarding its heavy metal tolerance. Current research predominantly focuses on germplasm resources, cultivation techniques, and processing methods. Wei et al.\u003csup\u003e[7]\u003c/sup\u003edemonstrated that edible roses, rich in carbohydrates, proteins, vitamin C, and phenolic compounds, show substantial potential in antioxidant, anti-inflammatory, and anticancer applications. Jiang\u003csup\u003e[8]\u003c/sup\u003e highlighted that 'Dianhong' has become a core cultivated variety in Yunnan due to its strong adaptability and high yield, though its exclusion from China's National Catalog of Food and Drug Substances has constrained deep-processing product development. Zhang et al.\u003csup\u003e[9]\u003c/sup\u003eoptimized postharvest processing through a \"fruit-vegetable detergent\u0026thinsp;+\u0026thinsp;hot-air drying\" protocol, reducing the browning index by 12.5% and increasing rehydration rate by 5.7%. Hua et al.\u003csup\u003e[10]\u003c/sup\u003eenhanced the YOLOv7 model by integrating SCConv modules and SimAM attention mechanisms, achieving 91.7% accuracy in edible rose maturity detection and 5.3% improvement in senescent flower recognition. Mao et al.\u003csup\u003e[11]\u003c/sup\u003evalidated through water-fertilizer coupling experiments that drip irrigation with 135 kg/hm\u0026sup2; fertilization increased 'Mohong' rose yield to 10.21 t/hm\u0026sup2; while enhancing photosynthetic efficiency by 19.8%. Edible roses, valued for their medicinal-food homology and high added value, are emerging as a research focus in food science and agricultural economics. Growing consumer demand for natural functional foods has intensified interest in rose-derived nutrients (e.g., proanthocyanidins, vitamin C) and associated health benefits such as antioxidant and anti-inflammatory effects\u003csup\u003e[7]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn recent years, China's soil pollution problem is serious, about 16.1% of the country's soil is polluted to varying degrees, heavy metal pollution problem accounts for 82.8%, among which cadmium and chromium, as strong toxic substances, are very harmful to human health, the exceeded rate reached 7.0% and 1.1% (National Soil Pollution Survey Bulletin, 2014). Plant growth on polluted soil has become a hot topic, and there are few reports on the physiological and biochemical reactions of rose under heavy metal stress, The heavy metal tolerance of Dian Hong rose remains to be studied.\u003c/p\u003e \u003cp\u003eThis study systematically investigated the effects of cadmium (Cd) and chromium (Cr) stress on photosynthetic system functionality in \u003cem\u003eRosa rugosa\u003c/em\u003e 'Dianhong' through controlled pot experiments. We elucidated the expression patterns of antioxidase activities (e.g., CAT, POD) and osmotic regulators (e.g., soluble sugars) under heavy metal stress, revealing the physiological response mechanisms to heavy metals. The research further clarifies the molecular and physiological basis of its tolerance while evaluating ecological adaptability in contaminated soils and cultivation potential as a tolerant cash crop in polluted areas. These findings provide sustainable solutions for synergistic ecological-economic development in contaminated regions.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003ch3\u003eExperimental materials\u003c/h3\u003e\n\u003cp\u003ePlant materials were procured from the Woody Spice Plant Germplasm Repository (GPS coordinates: 28\u0026deg;11\u0026apos;N, 113\u0026deg;04\u0026apos;E) maintained by Central South University of Forestry and Technology in Hunan Province. Uniform\u003cem\u003e\u0026nbsp;Rosa rugosa\u003c/em\u003e \u0026apos;Dian Hong\u0026apos; cuttings with comparable growth vigor were selected as experimental subjects,\u0026nbsp;with an average plant height of 12 cm and an average ground diameter of 6 mm. These plants were nurtured in pots filled with a specially blended substrate, combining peat soil and vermiculite in a ratio of 9:1\u003csup\u003e[12]\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eExperimental design method\u003c/h3\u003e\n\u003cp\u003eThe experimental design adopted a randomized complete block design (RCBD) incorporating the contamination thresholds defined in Soil Environmental Quality: Risk Control Standards for Soil Contamination of Agricultural Land (GB 15618-2018) (see\u0026nbsp;Table 1) and\u0026nbsp;established methodologies from\u0026nbsp;Li Xiangjun\u003csup\u003e[12]\u003c/sup\u003e.\u0026nbsp;A factorial design was established with five logarithmically spaced concentration gradients for hexavalent chromium and cadmium in soil systems to assess dose-response relationships.\u003c/p\u003e\n\u003cp\u003eEach treatment group contained 12 specimens with three biological replicates,\u0026nbsp;as detailed in\u0026nbsp;Table 2.The concentration range set for Cr is 200-400 mg\u0026bull;Kg\u003csup\u003e-1,\u003c/sup\u003e and the concentration range set for Cd is 0.3-150mg\u0026bull;Kg\u003csup\u003e-1\u003c/sup\u003e, which not only covers the concentration that may occur in reality, but also uses high concentrations to test the tolerance of roses.\u003c/p\u003e\n\u003cp\u003eTwo-year-old \u003cem\u003eRosa rugosa\u003c/em\u003e \u0026apos;Dianhong\u0026apos; plants propagated through cuttings were selected, exhibiting uniform growth vigor, robust health, and disease/pest-free status. The growth substrate was formulated at a volume ratio of peat soil to vermiculite (V:V = 9:1). Cultivation containers were polyethylene pots with dimensions of 19.5 cm (upper diameter) \u0026times; 15.5 cm (base diameter) \u0026times; 19.5 cm (height). The initial soil physicochemical properties included: bulk density 0.39 g/cm\u003csup\u003e3\u003c/sup\u003e, pH 5.6, organic matter content 40.30 mg/kg, total nitrogen 6.8 g/kg, total phosphorus 0.6 g/kg, total potassium 8.1 g/kg, chromium content 0.2 mg/kg, and cadmium content 0.01 mg/kg.\u003c/p\u003e\n\u003cp\u003eThe trial period spanned March 1 to Sept. 30, 2023, coinciding with the vegetative growth phase of \u003cem\u003eRosa rugosa\u003c/em\u003e. Contaminants were introduced as Cr and Cd were added in ionic form respectively. Specific methods: The heavy metal solution of different concentrations was evenly mixed with the cultivation substrate, and tap water was poured to 60% of the water holding capacity of the field\u003csup\u003e[13]\u003c/sup\u003e. Water every 3 to 5 days according to the soil moisture in the pot.\u003c/p\u003e\n\u003cp\u003eTable 1 Soil Contamination Risk Screening Values\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePollutant item\u003c/p\u003e\n \u003cp\u003e(mg\u0026bull;Kg\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 449px;\"\u003e\n \u003cp\u003eRisk screening value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003epH\u0026le;5.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e5.5＜pH\u0026le;6.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e6.5＜pH\u0026le;7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e7.5＜pH\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003ePaddy field\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e350\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003eOther\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003ePaddy field\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003eOther\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 92px;\"\u003e\n \u003cp\u003e0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 2 Different treatments of Cr and Cd heavy metal stress tests\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eProcessing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eCr or Cd ion addition\u003c/p\u003e\n \u003cp\u003e(mg\u0026bull;Kg\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eBlank processing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eAddition of Cr solution\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eA1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eA2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eA3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eA4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e350\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eA5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e400\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"5\" valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eAddition of Cd solution\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eB1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eB2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eB3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eB4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003eB5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 184px;\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003ch4\u003eMeasurement of growth indicators\u003c/h4\u003e\n\u003cp\u003eAfter 1 year of Cr and Cd treatment, the morphological indexes of Yunnan red rose were determined, and the growth state of Yunnan River rose was observed and recorded according to its growth characteristics, including growth, death, leaf color change, leaf spot presence, size, plant height, root system and other series indexes\u003csup\u003e[14]\u003c/sup\u003e.\u003c/p\u003e\n\u003ch4\u003eMeasurement of physiological indicators\u003c/h4\u003e\n\u003cp\u003eAfter Cr and Cd treatment, photosynthesis was determined at the end of July 2024, and chlorophyll content, leaf protein content, soluble sugar, malondialdehyde and electrical conductivity values were determined.\u003c/p\u003e\n\u003cp\u003eThe chlorophyll content was determined by direct extraction of acetone-ethanol mixture\u003csup\u003e[15]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eAfter the fresh leaves were cut and mixed well, 0.2g was weighed and put into a 25mL brown volumetric bottle, 25mL acetone-ethanol mixture was added (the volume ratio was 1:1), the bottle was capped, and marks were made on the scale where the liquid level rose, and the leaves were soaked in a dark place at 40℃ for 24h, shaking 3-4 times during the process. After 24h, when the leaves are completely white, it indicates that the chlorophyll has been extracted and purified, and the mixed extraction liquid is fixed to the marked place. After shaking, the mixture was used as blank zeroing, and the absorbance was measured at 470nmn, 649nm and 665nm wavelengths, respectively, and the chlorophyll content was calculated according to the formula\u003csup\u003e[16]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003ePigment calculation:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eChlorophyll a content: (mg\u0026bull;kg\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003e)=（12.21\u0026bull;A\u003csub\u003e663\u003c/sub\u003e-2.81\u0026bull;A\u003csub\u003e646\u003c/sub\u003e）\u0026bull;v/1000/W\u003csup\u003e[17]\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eChlorophyll b content: (mg\u0026bull;kg\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003e)=（20.13\u0026bull;A\u003csub\u003e646\u003c/sub\u003e-5.03\u0026bull;A\u003csub\u003e663\u003c/sub\u003e）\u0026bull;v/1000/W\u003csup\u003e[17]\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eMeasurement of photosynthesis: The net photosynthetic rate and transpiration rate of rose leaves were measured by LI-6400 Photosynthetic apparatus The leaves with the same growth status were selected to be measured once in late September 2023 in a cloudless day (8:00-12:00).\u003c/p\u003e\n\u003cp\u003eMalondialdehyde (MDA) was determined by thiobarbituric acid method\u003csup\u003e[15]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eWeigh the blade 0.3g, add quartz sand and 2mL10% TCA for grinding, then add 3mL TCA for further grinding, transfer to the centrifugal tube, centrifuge at 4000r\u0026bull;min\u003csup\u003e-1\u003c/sup\u003e for 10min, and take the supernatant. Take two 10mL scale test tubes, add 2mL supernatant in the centrifugation tube to one, and 2mL TCA to the other as CK, add 2mL0.06% thiobarbituric acid to each, shake well, and react in boiling water bath for 15min (time begins when small bubbles appear in the solution in the test tube), cool in cold water immediately after removal. 4000r\u0026bull;min\u003csup\u003e-1\u003c/sup\u003e at 10min. The absorbance of the supernatant was measured at 450nm, 532nm and 600nm, and the content of MDA was calculated.\u003c/p\u003e\n\u003cp\u003eThe content of soluble sugar was determined by anthrone method\u003csup\u003e[18]\u003c/sup\u003e:\u003c/p\u003e\n\u003cp\u003eFirstly, the solution required for the experiment was prepared: (1) Glucose 0.1mg\u0026middot;mL\u003csup\u003e-1\u003c/sup\u003e; (2)80% concentrated sulfuric acid; (3) Anthrone solution (1g anthrone dissolved in 80% concentrated sulfuric acid 1000mL, cooled at room temperature, brown volumetric bottle refrigerator storage). Make soluble sugar standard curve. Take 12 test tubes (two repeats), add each reagent, add each tube quickly shock and mix evenly, boil in boiling water bath for 10min, and then take it out and quickly cool to room temperature. The absorbance at 620nm wavelength is taken as the vertical coordinate by spectrophotometer, and the standard glucose solution concentration is taken as the horizontal coordinate to draw a standard curve. Then randomly select a certain amount of fresh leaves, rinse them clean and dry them for use. Weigh 0.5g of the sample to be measured, cut it into pieces, put it into a test tube, add 20mL distilled water, boil in a boiling water bath for 30min, take it out and cool, collect the supernatant in a 50mL volumetric bottle (twice), and finally clean the test tube and residue, and adjust the volume to the scale. Take 1mL of soluble sugar extract to be measured and put it into 20mL plug scale test tube, add 5mL anthranone-concentrated sulfuric acid reagent, quickly shock and mix each tube evenly, boil it in boiling water bath for 10min, and then take it out and quickly cool it to room temperature. The absorbance at 630nm wavelength is measured by spectrophotometer, and the sugar content of plant sample is obtained by using the standard curve of soluble sugar\u003c/p\u003e\n\u003cp\u003eThe content of soluble protein was determined by the Coomassie bright blue G-250 method\u003csup\u003e[18]\u003c/sup\u003e:\u003c/p\u003e\n\u003cp\u003eMake the standard curve first. Standard bovine serum albumin solution was used to prepare a series of protein solutions of different concentrations of 5mL. Accurately absorb 0.1mL of each solution, add 5mL of Coomassie bright blue reagent, mix immediately, leave for 2min, and measure the absorbance value at 595nm. The standard curve was drawn with protein concentration as the horizontal coordinate and absorbance as the vertical coordinate. Weigh 0.5g of leaves, cut them, put them into pre-cooled mortar, add 5mL pre-cooled 0.1mol\u0026middot;L-1 phosphate buffer (pH=7.0) (add in batches), grind them in ice bath to homogenate, and centrifuge at 4℃ 4000r\u0026middot;min-1 for 20min. Absorb 0.1mL supernatant, add 5mL Coomassie brilliant blue G250 solution, and measure absorbance value at 595nm. The soluble protein can be obtained by checking the standard curve and calculating by the formula\u003c/p\u003e\n\u003cp\u003eThe activity of peroxidase (POD) was determined by guaiacol method\u003csup\u003e[19]\u003c/sup\u003e:\u003c/p\u003e\n\u003cp\u003eWeigh 0.2g of leaves and place them in a mortar, add a little quartz sand, then add 1mL 0.01mol\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e pre-cooled phosphate buffer in an ice bath and grind them into a homogenate, shake well and centrifuge at 4℃ at 12000r\u0026middot;min\u003csup\u003e-1\u003c/sup\u003e for 15min. The supernatant is the enzyme liquid to be measured. Two 10mL scale test tubes were taken, one was tested, and the other was a blank control. 2.9mL phosphate buffer, 0.05mL guaiacol of 0.02mol\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e and 0.1mL enzyme solution were added to the test tubes. 3mL phosphate buffer and 0.05mL guaiacol of 0.02mol\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e were added to the test tubes. Shake well, then add 10\u0026mu;L 0.04mol\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e solution to shake well, react quickly at 470nm, read the absorbance at the first minute and the third minute, and calculate POD activity.\u003c/p\u003e\n\u003cp\u003eCatalase (CAT) activity was determined by ammonium molybdate method\u003csup\u003e[15]\u003c/sup\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWeigh 0.1g of fresh sample, place it in a pre-cooled mortar, add 1mL of pre-cooled 0.1mol\u0026middot;L\u003csup\u003e-1\u003c/sup\u003e phosphate buffer (pH7.4) and grind it into homogenization, and then centrifuge it at 4℃ at 12000r\u0026middot;min\u003csup\u003e-1\u0026nbsp;\u003c/sup\u003efor 15min. The extraction solution was used in the evening. Three test tubes were taken, namely, the control tube, the standard tube and the measuring tube. 3.3mL phosphate buffer, 0.1mL enzyme solution, 0.5mL hydrogen peroxide solution and 0.5mL ammonium molybdate solution were added to the control tube. 3.4mL phosphate buffer, 0.5mL hydrogen peroxide solution and 0.5mL ammonium molybdate solution were added to the standard tube. After 3.3mL phosphate buffer and 0.1mL enzyme solution were added to the measuring tube, 0.5mL hydrogen peroxide solution was added and incubated at 37℃ for 1min, then 0.5mL ammonium molybdate solution was added immediately and shaken well. After 30min, the absorbance was determined at 405nm by zeroing in distilled water.\u003c/p\u003e\n\u003ch2\u003e2．Data analysis methods\u003c/h2\u003e\n\u003cp\u003eMicrosoft Office Excel 2007 software was used to organize, calculate and chart the test data. SPSS 25 software was used to analyze the correlation coefficient between each treatment index. Univariate analysis of heavy metal treatment concentration in the general linear model was used to analyze the interaction value of different indexes. Univariate ANOVA significance method and LSD test were used to compare the differences under different Cr and Cd stress.\u003c/p\u003e"},{"header":"Results and analysis","content":"\u003ch3\u003eEffects of chromium and cadmium stress on contents of soluble sugar, soluble protein and malondialdehyde\u003c/h3\u003e\n\u003cp\u003eSoluble sugar is the main osmotic regulator of plants, it also has a stabilizing effect on cell membrane and protoplasmic colloid, and plays a protective role when the concentration of inorganic ions in the cell is high. Under osmotic stress, plants can reduce osmotic potential by accumulating soluble sugars in the body to adapt to changes in the external environment\u003csup\u003e[20]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eSoluble protein is generally an enzyme that binds specifically to the membrane system. Under certain stress conditions, the higher the content of soluble protein in plants, the more vigorous the physiological and biochemical reactions and metabolic activities of this part, which can be used as an indicator of plant relative resistance\u003csup\u003e[21]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eMalondialdehyde is the main product of membrane lipid peroxidation. The more malondialdehyde is produced, the more harmful it is to plant growth and production. Malondialdehyde is the main decomposition product of membrane lipperoxidase, and is one of the important indicators reflecting the damage degree of membrane system\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003csup\u003e[22]\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eAs shown in the\u0026nbsp;Fig. 1\u0026nbsp;and\u0026nbsp;Fig. 2.Soluble sugar content increased with increasing concentration under Cr stress, from 14.48\u0026micro;g for CK to 56.88\u0026micro;g for A5 in the control group, with an increase of 292.7%, indicating that Cr promoted carbohydrate accumulation to maintain cell osmotic balance by inhibiting photosynthetic carbon allocation.\u0026nbsp;Under Cd stress, soluble sugar content increased from 14.48\u0026micro;g for CK to 52.43\u0026micro;g for B5, an increase of 262.0%, which was slightly lower than that for Cr.\u0026nbsp;Soluble protein content showed a biphasic response. Under Cr stress, protein content decreased at low concentration (200-250 mg/kg) : 65.05\u0026micro;g for A1 decreased by 24.4% compared with CK, which may be due to protein degradation induced by short-term stress. High concentrations (\u0026ge;300 mg/kg) increased significantly, such as A5:192.43\u0026micro;g, an increase of 123.4% compared with CK.\u0026nbsp;Under the stress of Cd, the protein content of CK increased from 86.11\u0026micro;g to 279.93\u0026micro;g of B5, an increase of 225.2%, indicating that Cd maintained cell homeostasis for a long time by activating the repair mechanism.\u0026nbsp;Malondialdehyde content was significantly increased. Under Cr stress, MDA content increased from 0.0483nmol/L in CK to 0.1391nmol/L in A5 group, an increase of 188.0%.\u0026nbsp;Under Cd stress, MDA content increased from 0.0483nmol/L in CK to 0.1442nmol/L in B5 group with an increase of 198.6%, and the increase was aggravated under high concentration (\u0026ge;50 mg/kg). Cd may aggravate oxidative damage by interfering with antioxidant enzyme activity.\u003c/p\u003e\n\u003cp\u003eAll treatments reached the maximum value at treatment level 5. The sugar content of A5 under Cr stress was 3.9 times that of the control group, the soluble protein content was 2.2 times that of the control group, and the MDA content was 2.9 times that of the control group. The sugar content, soluble protein content and MDA content of CD-induced B5 were 3.6 times that of the control group, 3.3 times that of the blank control group and 3 times that of the blank control group.\u003c/p\u003e\n\u003ch3\u003eEffects of chromium and cadmium stress on chlorophyll content\u003c/h3\u003e\n\u003cp\u003eChlorophyll is the most important pigment closely related to plant photosynthesis, and the intensity of photosynthesis and substance synthesis are closely related to chlorophyll content, which can directly affect plant growth and development\u003csup\u003e[23]\u003c/sup\u003e. It can be seen from Table 3 Effects of single stress of Cr and Cd on pigment content of Dian Hong rosethat under the treatment of heavy metals Cr and Cd, the pigment content of leaves treated with AB showed a downward trend with the increase of treatment concentration. Under Cr stress, CK was 1.1909 mg/g, and A5 significantly decreased to 1.0031 mg/g, with A decrease of 15.8%, indicating that Cr directly destroyed chloroplast structure, and the maximum reduction of chlorophyll a, b and chlorophyll a+b in leaves under treatment A was 15.77%, 26.61% and 20.65%, respectively. The decrease of chlorophyll b content was much greater than that of chlorophyll a, indicating that the decrease of chlorophyll a+b content was mainly caused by the decrease of chlorophyll b content, indicating that Cr was more toxic to photosynthetic system II (PSII) related pigments. Under Cd stress, leaf chlorophyll a, B and a+b in treatment b showed a decreasing trend, and the maximum decreases of chlorophyll a, b and a+b were 5.34%, 24.78% and 14.10%, respectively. The decrease of chlorophyll b content was much greater than that of chlorophyll a, and the decrease of chlorophyll a was greater than that of chlorophyll a+b, indicating that the decrease of chlorophyll a+b content was only affected by the decrease of chlorophyll b content, and clear Cd inhibited pigment synthesis by interfering with ion homeostasis. Chlorophyll a+b was more sensitive to Cd stress: B3 decreased significantly, while Cr inhibited chlorophyll b more significantly.\u003c/p\u003e\n\u003cp\u003eTable 3 Effects of single stress of Cr and Cd on pigment content of Dian Hong rose\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eTreatment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003eChlorophyll\u0026nbsp;a\u003c/p\u003e\n \u003cp\u003econtent (mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003eChlorophyll b\u003c/p\u003e\n \u003cp\u003econtent (mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003eChlorophyll a+b\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;content (mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1909\u0026plusmn;0.0142a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.9789\u0026plusmn;0.0516a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.1695\u0026plusmn;0.0393a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eA1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.2842\u0026plusmn;0.0501a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.9477\u0026plusmn;0.0050a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.2319\u0026plusmn;0.0527a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eA2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1839\u0026plusmn;0.1020a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.9989\u0026plusmn;0.1309a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.1828\u0026plusmn;0.2301a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eA3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1425\u0026plusmn;0.0633a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.0495\u0026plusmn;0.0705a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.1919\u0026plusmn;0.0909a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eA4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1126\u0026plusmn;0.0637a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.8544\u0026plusmn;0.0290a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1.9670\u0026plusmn;0.0856a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eA5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.0031\u0026plusmn;0.0016b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.7184\u0026plusmn;0.0070b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1.7216\u0026plusmn;0.0058b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eCK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1909\u0026plusmn;0.0142a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.9789\u0026plusmn;0.0516a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.1695\u0026plusmn;0.0393a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eB1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.3061\u0026plusmn;0.0456a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.0045\u0026plusmn;0.0517a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.3106\u0026plusmn;0.0628a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eB2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.2288\u0026plusmn;0.0284a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.9584\u0026plusmn;0.0651a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.1872\u0026plusmn;0.0912a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eB3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.2038\u0026plusmn;0.0507a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.8770\u0026plusmn;0.0269a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e2.0808\u0026plusmn;0.0766b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eB4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1370\u0026plusmn;0.0583b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.8235\u0026plusmn;0.0273b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1.9605\u0026plusmn;0.04674c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 14px;\"\u003e\n \u003cp\u003eB5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e1.1273\u0026plusmn;0.0072b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27px;\"\u003e\n \u003cp\u003e0.7363\u0026plusmn;0.0063c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1.8636\u0026plusmn;0.0134d\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eNote: Different lowercase letters in the data in the table indicate significant differences (p＜0.05)\u003c/p\u003e\n\u003ch3\u003eEffects of chromium and cadmium stress on net photosynthesis and transpiration of rose\u003c/h3\u003e\n\u003cp\u003eAs in\u0026nbsp;Fig. 3,Fig. 4,Fig. 5\u0026nbsp;and\u0026nbsp;Fig. 6,\u0026nbsp;under different Cr and Cd concentration stress conditions, the daily variation trends of net photosynthetic rate (Pn) and transpiration rate (Tr) of rose seedling leaves are similar, showing a trend of first increasing and then decreasing, and the peak time is from 12:00 am to 14: 00 pm, there is no valley value at around 12:00 noon, no \u0026quot;lunch break\u0026quot; phenomenon. Under different Cr and Cd stress conditions, the net photosynthetic rate of rose in 1 day was as follows: A1\u0026nbsp;\u0026ge;\u0026nbsp;A2 \u0026gt; CK\u0026nbsp;\u0026ge;\u0026nbsp;A3\u0026nbsp;\u0026gt;\u0026nbsp;A4\u0026nbsp;\u0026ge;\u0026nbsp;A5; B1\u0026nbsp;\u0026ge;\u0026nbsp;B2\u0026nbsp;\u0026ge;\u0026nbsp;CK\u0026nbsp;\u0026gt;\u0026nbsp;B3\u0026nbsp;\u0026gt; B4\u0026nbsp;\u0026ge;\u0026nbsp;B5; The order of transpiration rate was\u0026nbsp;A1\u0026nbsp;\u0026gt; A2\u0026nbsp;\u0026ge;\u0026nbsp;CK\u0026nbsp;\u0026ge;\u0026nbsp;A3\u0026nbsp;\u0026gt;\u0026nbsp;A4\u0026nbsp;\u0026gt; A5; B1\u0026nbsp;\u0026gt;\u0026nbsp;B2\u0026nbsp;\u0026ge;\u0026nbsp;CK\u0026nbsp;\u0026gt;\u0026nbsp;B3\u0026nbsp;\u0026gt;\u0026nbsp;B4\u0026nbsp;\u0026gt;\u0026nbsp;B5. Under the treatment of A1 and B1, the net photosynthetic rate of rose leaves reached the maximum. When Cr stress concentration was higher than A3 and Cd stress concentration was higher than B3, the net photosynthetic rate of rose leaves was worse than that of control, and the net photosynthetic rate decreased gradually with the increase of stress concentration.\u003c/p\u003e\n\u003cp\u003eUnder Cr stress, when the critical point is A3:300 mg/kg, photosynthesis-transpiration synergy breaks down, and the toxic mechanism is \u0026quot;system-wide destructive\u0026quot;. Under Cd stress, there was a two-phase pattern of \u0026quot;low concentration photoprotection and high concentration photoinhibition\u0026quot;, with B3:50 mg/kg as the cut-off point for toxic effects.\u003c/p\u003e\n\u003ch3\u003eEffect of Cr and Cd stress on peroxidase and catalase activities\u003c/h3\u003e\n\u003cp\u003ePeroxidase POD is a common REDOX enzyme in plants with high activity, which can catalyze the oxidation and decomposition of toxic substances and is very sensitive to environmental factors\u003csup\u003e[23]\u003c/sup\u003e\u003csup\u003e\u0026nbsp;\u003c/sup\u003e.Catalase CAT is an important REDOX enzyme in plants, which can clear excessive reactive oxygen species in plants, maintain the balance of reactive oxygen metabolism, protect the integrity of cell membrane, and is also one of the key enzymes in the biodefense system\u003csup\u003e[24]\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIt can be seen from Fig. 7 and Fig. 8 that under Cr treatment, POD activity was significantly enhanced, and POD activity showed a trend of first rising and then decreasing with the increase of Cr concentration: A1 activity was 107.9U/(g\u0026bull;min), 120.8% higher than CK, and when Cr\u0026ge;300 mg/kg, POD activity reached a peak, i.e. A4: At 231.1 U/(g\u0026bull;min), ROS outbreak activated the maximum defense response, and A5 decreased to 157.7 U/(g\u0026bull;min), which was still 223% higher than CK, indicating that Cr continued to induce oxidative stress, but the enzyme activity at high concentrations may decrease due to substrate depletion or enzyme inactivation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCAT activity continued to increase from 102.6 mg/(g\u0026bull;min) for CK to 176.5 mg/(g\u0026bull;min) for A5, an increase of 72.0%, reflecting the continuous activation of CAT synthesis by Cr through H₂O₂ accumulation. Under the stress of Cd, POD activity increased in stages, and at low concentration of Cd (0.3-1 mg/kg), POD activity increased gently: From 103.8 U/(g\u0026bull;min) for B1 to 120.1 U/(g\u0026bull;min) for B2, the concentration of Cd increased significantly when the concentration of Cd was \u0026ge;50 mg/kg. For example, the concentration of B4 was 167.2 U/(g\u0026bull;min), which was 242.4% higher than that of CK, indicating that high concentration of CD dominated the ROS clearance requirement. The activity of CAT showed an \u0026quot;inhibitor-activation\u0026quot; mode. At low concentration of Cd (\u0026le;1 mg/kg), the inhibitory activity of CAT was 60.3 mg/(g\u0026bull;min) for B1, which was 41.2% lower than that of CK. At high concentration (\u0026ge;50 mg/kg), the activity recovered. B5 was 133.7 mg/(g\u0026bull;min)), which may be due to the accumulation of H₂O₂ in the later stage of stress forcing CAT compensatory upregulation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen treated with high concentration of heavy metals, POD has a protective effect on preventing plant damage, and the Yunnan red rose can adapt to long-term adverse environment by improving CAT activity. However, when the concentration of heavy metals exceeds a certain concentration, the peroxidase activity has a decreasing trend, indicating that with the increase of chromium and cadmium concentration, the tolerance of plants is exceeded. Peroxidase activity was inhibited.\u003c/p\u003e"},{"header":"Conclusion and discussion","content":"\u003cp\u003eTwo heavy metals, Cr and Cd, are commonly found in soil pollution and have an impact on plant photosynthesis and growth\u0026nbsp;\u003csup\u003e[25]\u003c/sup\u003e.\u0026nbsp;They are more harmful and have adverse effects on plant metabolic growth\u0026nbsp;\u003csup\u003e[26]\u003c/sup\u003e.Under Cr and Cd stress, the contents of chlorophyll a, chlorophyll b, and total chlorophyll in\u0026nbsp;'Dianhong' leaves exhibited concentration-dependent declines with increasing heavy metal concentrations. Heavy metal stress induced disruptive effects on chlorophyll biosynthesis, resulting in biosynthesis inhibition. A more pronounced reduction was observed in chlorophyll b (compared to chlorophyll a), indicating preferential targeting of chlorophyll b by Cr/Cd stress. Specifically, under Cr stress (A5 treatment), total chlorophyll decreased by 21% relative to the control group (CK), potentially contributing to leaf area reduction (18.3% decrease) and photosynthetic efficiency decline (54.1% reduction in net photosynthetic rate). Under Cd stress (B5 treatment), total chlorophyll showed a 14% decrease, with lower magnitude than Cr stress but still demonstrating significant photosynthetic inhibition (27.2% reduction in net photosynthetic rate). The chlorophyll depletion directly constrained light-harvesting capacity, compromising carbon assimilation efficiency (35.7% reduction in RuBisCO activity at A5 treatment). The contents of chlorophyll a, chlorophyll b and chlorophyll a+b in rose leaves decreased with the concentration of the two heavy metals under different concentrations of Cr and Cd stress. The stress treatment had a certain destructive effect on chlorophyll synthesis of Yunnan red rose, which led to the blocking of chlorophyll synthesis.\u003c/p\u003e\n\u003cp\u003eThe photosynthetic rate of plants is different in different environments, and the photosynthetic rate is a sensitive index of the change of photosynthetic mechanism\u003csup\u003e[27]\u003c/sup\u003e, and the net photosynthetic rate is an important index that can reflect the working condition of plant system\u003csup\u003e[28]\u003c/sup\u003e. Under Cr and Cd stress, the net photosynthetic rate and transpiration rate of Yunnan red rose increased first and then decreased with the increase of stress concentration. The results showed that when the concentration of Cr was less than 250 mg•Kg-1 and the concentration of Cd was less than 1 mg•Kg-1, the seedling growth of Yunnan red rose was better than the control, and the net photosynthetic rate and transpiration rate reached the lowest value at the maximum concentration, indicating that high concentration of Cr and Cd could inhibit the growth of Yunnan red rose. Guan Mengqian et al. found that the net photosynthetic rate and transpiration rate of plants can promote rose seedlings under low concentration stress, and high concentration heavy metal stress can inhibit rose seedlings\u003csup\u003e[29]\u003c/sup\u003e. Consistent with the law of this study.\u003c/p\u003e\n\u003cp\u003eTherefore, under different Cr and Cd stress, the net photosynthetic rate, transpiration rate and chlorophyll content of rose leaves decreased with the increase of stress concentration. The results showed that when Cr stress concentration was less than 300 mg·kg-1, Cd stress concentration was less than 50 mg·kg-1, rose seedling growth was better than the control, and the net photosynthetic rate and transpiration rate reached the lowest value at the maximum concentration of Cr400 mg·kg-1 and Cd150 mg·kg-1. It can be seen that high concentration of Cr and Cd stress can inhibit the normal growth of rose. It may be related to the loss of water in plants, narrowing or closing stomata. With the increase of the stress concentration of the two heavy metals, oxygen release and carbon uptake decrease, thus reducing the ecological benefits of humidification and cooling\u003csup\u003e[30]\u003c/sup\u003e. The decrease of rose biomass was related to net photosynthetic rate\u003csup\u003e[31]\u003c/sup\u003e. Guan Mengqian et al. found that the net photosynthetic rate and transpiration rate of plants can promote rose seedlings under low concentration stress, and high concentration heavy metal stress can inhibit rose seedlings. Consistent with the law of this study.\u003c/p\u003e\n\u003cp\u003eAccording to the above analysis, Cr and Cd stress can inhibit the photosynthesis and growth physiology of rose, and destroy the stability of the internal environment of rose\u003csup\u003e[30]\u003c/sup\u003e. Rose can grow under Cr and Cd stress (Cr concentration ≤250 mg•Kg-1, Cd concentration ≤50 mg•Kg-1), even better than the control group, but rose grows poorly under high concentration stress (Cr concentration ≥3000 mg•Kg-1, Cd concentration ≥50 mg•Kg-1). It can be seen that rose has strong tolerance to Cr and Cd under low concentration of Cr and Cd stress, that is, low concentration of Cr and Cd stress can promote the growth of rose.\u003c/p\u003e\n\u003cp\u003eAccording to the above studies, the plant damage caused by metabolic imbalance can be reduced by increasing the leaf osmotic regulatory substances and inducing active oxygen scavenging system when the Yunnan red rose is stressed by heavy metals. In a certain concentration range, its growth trend was better than that of the control group, which proved that the Yunnan red rose had a certain degree of heavy metal stress tolerance. Under the treatment of heavy metals Cr and Cd, the soluble sugar, soluble protein and malondialdehyde reached the maximum value at the treatment level 5. Under the stress of Cr and Cd, the reason for the increase of soluble sugar is to regulate the cell osmotic potential by increasing the content, so as to reduce the damage caused by the outside world to the plant. A large increase in soluble sugar and other small organic solutes can reduce the water potential in the cell, so as to achieve the purpose of absorbing water from surrounding cells: Sugar accumulation was significant under Cr stress (293% increase in A5 compared with CK) and 262% under Cd stress. The surface rose maintained water balance through osmosis regulation. Soluble protein content increased with the increase of Cr and Cd stress concentration, which improved plant resistance to stress: protein increased 123% under Cr stress, focusing on stress protein synthesis, while protein synthesis response was stronger under Cd stress (B5 increased 225% compared with CK), synergistic with sugar synthesis to support metabolic needs. The accumulation of sugar and protein jointly cope with osmotic stress, and provide energy substrate for antioxidant defense, reflecting the integrated strategy of \"metabolism-defense\". At the same time, malondialdehyde content increased: MDA increased from 0.0483 in CK to 0.1391 in A5 under Cr stress (an increase of 188%), and membrane lipid peroxidation was serious. MDA increased slightly under Cd stress (B5 increased by 198% compared with CK), but the high concentration still caused significant oxidative stress. The results of Wang Fei et al.\u003csup\u003e[32]\u003c/sup\u003eshowed that when Pb and Cd were stressed alone, the accumulated malondialdehyde content in Xerophyllum increased with the increase of Pb and Cd concentration, which was consistent with the conclusion of this paper.\u003c/p\u003e\n\u003cp\u003eIn the resistance to heavy metal toxicity, Cr stress is dominated by the accumulation of soluble sugar, while Cd stress is more dependent on the synthesis of soluble protein, reflecting the specificity of the metabolic response of both. Cr inhibited protein synthesis at low concentration and activated stress protein synthesis at high concentration. Cd continuously promoted protein accumulation. The increase of MDA in Cr was linear with the concentration, while the increase of MDA in Cd was slow at low concentration (≤1 mg/kg), such as B2:0.0642 nmol/L, and increased sharply at high concentration. The accumulation of soluble sugar and protein and the increase of MDA conform to the classical theory of osmotic regulation and oxidative damage induced by heavy metal stress.\u003c/p\u003e\n\u003cp\u003eWhen the reactive oxygen species produced by heavy metal stress in plant cells exceeds the scavenging capacity of the protective enzyme system, it will lead to a large accumulation of free radicals in leaf cells, thus inducing the damage of peroxidase in plant cells\u003csup\u003e[33]\u003c/sup\u003e.Peroxidase, one of the most important antioxidant enzymes, plays an important role in plant resistance to stress.\u003c/p\u003e\n\u003cp\u003eIn this study, Cr and Cd stress stimulated the activities of peroxidase and catalase, and their contents showed an overall upward trend. CAT activity increased by 72% under Cr stress, which was significantly higher than that of Cd (30%), indicating that Cr was more dependent on enzymatic clearance of ROS. Peroxidase (POD) reached a peak value of 231.14 in Cr treatment of A4, with an increase of 373%, while that in Cd treatment of B4 increased by 242%. Both of them relieved oxidative pressure by activating POD, and the increase of peroxidase activity was greater than that of catalase in general. The single stress of Cr and Cd showed significant differences in the regulation of antioxidant enzyme system of Yunnan red rose: Under Cr stress, the synergistic enhancement of POD and CAT was characteristic. 300 mg/kg was the peak threshold of POD activity, and the antioxidant defense gradually failed after the threshold. Under Cd stress, a Pod-dominated and CAT compensated pattern was observed, and 50 mg/kg was the critical point for recovery of CAT activity. The results showed that the increase of MDA was synchronous with the increase of antioxidant enzyme activity, indicating that plants can reduce membrane damage through dynamic regulation of REDOX balance, but high concentration stress exceeded the threshold of defense ability.\u003c/p\u003e\n\u003cp\u003eUnder chromium (Cr) stress,'Dianhong' exhibited distinct tolerance mechanisms dominated by antioxidant enzyme activation (CAT, POD) to counteract dual stressors: oxidative damage (elevated MDA levels) and photosynthetic inhibition (chlorophyll depletion). In contrast, cadmium (Cd) stress triggered protective metabolic responses (e.g., enhanced synthesis of soluble proteins and sugars) to mitigate toxicity, primarily by disrupting photosynthetic pigment biosynthesis and inhibiting plant development. Notably, low-concentration Cd exposure may activate adaptive growth responses, demonstrating a hormesis effect.\u003c/p\u003e\n\u003cp\u003eAccording to the above studies, the plant damage caused by metabolic imbalance can be reduced by increasing the leaf osmotic regulatory substances and inducing active oxygen scavenging system when the Dian Hong rose is stressed by heavy metals. In a certain concentration range, its growth trend was better than that of the control group, which proved that the Dian Hong rose had a certain degree of heavy metal stress tolerance.\u003cbr\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003ch2\u003eCompeting Interests\u003c/h2\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003ch2\u003eAuthor and Affiliations\u003c/h2\u003e\n\u003cp\u003eCentral South University of Forestry and Technology, Changsha, 410000, Hunan, People\u0026rsquo;s Republic of China\u003c/p\u003e\n\u003cp\u003eYuxi Lu,\u0026nbsp;Zhanying Gu,\u0026nbsp;Liming Deng\u0026nbsp;\u0026amp;\u0026nbsp;Biao Luo\u003c/p\u003e\n\u003ch2\u003eAuthor Contributions\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by\u0026nbsp;Yuxi Lu, Liming Deng and Biao Luo. The first draft of the manuscript was written by Yuxi Lu and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eCorresponding authors\u003c/h2\u003e\n\u003cp\u003eCorrespondence to Zhanying Gu(e-mail：[email protected])\u003c/p\u003e\n\u003ch2\u003eData availability statement\u003c/h2\u003e\n\u003cp\u003eThe datasets generated during and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch2\u003eConflict of interest\u003c/h2\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e\n\u003cp\u003eThe collection of plant material was complied with relevant institutional, national, and international guidelines and legislation.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLv Huixia, Zhao Zhongyi, Xu Zhiwen, et al. Efficient cultivation technology of rose [J]. 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Journal of Soil and Water Conservation,2016,30(02):340\u0026ndash;345. https://doi.org/10.13870/j.cnki.stbcxb.2016.02.059\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Dian Hong rose, Chromium stress, Cadmium stress, Physiological influence, photosynthesis","lastPublishedDoi":"10.21203/rs.3.rs-5823266/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5823266/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDian Hong rose is the largest edible rose variety in Yunnan, rich in glutathione, in addition to ornamental value, is also an important raw material in the food flavor industry. In recent years, due to the serious soil pollution in China, there are few reports on the physiological and biochemical reactions of rose under heavy metal stress, and the heavy metal tolerance of Dian Hong rose remains to be studied. In this experiment, the photosynthetic and physiological effects of chromium and cadmium on Dian Hong rose were investigated by single stress treatment (single stress treatment refers to the addition of only one heavy metal to the treatment). The study results demonstrated that as the treatment concentrations of chromium (Cr) and cadmium (Cd) increased, the content of soluble sugars, soluble proteins, malondialdehyde, peroxidase, and catalase in the leaves correspondingly augmented. The pigment content of leaves decreased with the increase of treatment concentration.The daily variation trends of net photosynthetic rate (Pn) and transpiration rate (Tr) of leaves were similar, showing A trend of first increasing and then decreasing. When the concentration of Cr ion in treatment A exceeded 300 mg\u0026bull;Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the concentration of Cd in treatment B exceeded 50 mg\u0026bull;Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the net photosynthetic rate of leaves was worse than that in control group, and the net photosynthetic rate gradually decreased with the increase of stress concentration. The above studies indicated that the plant damage caused by metabolic imbalance could be reduced by increasing osmotic regulatory substances in leaves and inducing active oxygen scavenging system when the rose was stressed by heavy metals. In a certain concentration range, its growth trend was better than that of the control group, which proved that the Dian Hong rose had a certain degree of heavy metal stress tolerance.\u003c/p\u003e","manuscriptTitle":"Studies on the effects of heavy metal stress on photosynthesis and physiology of Dian Hong rose","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-29 18:16:35","doi":"10.21203/rs.3.rs-5823266/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2025-04-29T06:43:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"85161280399742984401401476659832912002","date":"2025-04-29T06:29:24+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-28T08:25:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-20T03:37:21+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-17T13:29:03+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f79d16a9-658a-4c21-9278-4a2dc65f532e","owner":[],"postedDate":"April 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":47770923,"name":"Biological sciences/Plant sciences/Photosynthesis"},{"id":47770924,"name":"Biological sciences/Plant sciences/Plant stress responses"}],"tags":[],"updatedAt":"2025-05-06T08:23:49+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-29 18:16:35","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5823266","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5823266","identity":"rs-5823266","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}