Does low potassium availability modulate the physiological responses of Corymbia seedlings and Eucalyptus cuttings?

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Maria Leidiane Reis Barreto, Cassio Rafael Costa dos Santos, Adam da Cruz Rodrigues, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8846297/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Aims Eucalypt plantations in Brazil have expanded into regions with highly weathered soils and marked heat and water deficits, where potassium (K) availability becomes a major constraint due to its role in osmotic adjustment, stomatal regulation and water use efficiency. This study evaluated physiological responses to potassium fertilization of two Corymbia species ( Corymbia citriodora subsp . variegata – CCV and Corymbia henryi – CH) recently introduced into breeding programs, and two traditional Eucalyptus urophylla × E. grandis cuttings (I144 and H13). Methods The experiment followed a completely randomized 4 × 2 factorial design and was conducted in pots for six months under greenhouse conditions. Leaf water potential (Ψf), gas exchange, biomass allocation, leaf anatomy and plant nutrition were evaluated. Results During the most stressful period, Ψf was 21% more negative under potassium omission (− K). Gas exchange was not affected by fertilization but differed among genotypes. Clone I144 showed higher stomatal conductance and transpiration, resulting in 26% lower water use efficiency. Potassium omission reduced root biomass by 23%. Despite this, I144 accumulated 34% more K in total biomass than the other genotypes under − K. Under potassium fertilization (+ K), genotypes exhibited 23% higher K use efficiency. Conclusions The physiological assessments of Eucalyptus and Corymbia revealed that the response to potassium fertilization is highly dependent on the intrinsic characteristics of each genotype, independent of the genus, species or propagation method (ex. seed or cutting). Fertilization Water stress Leaf morphology Leaf anatomy Photosynthesis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction With the expansion of the planted forests into areas with greater soil and climate constraints, it is important to pursue Eucalyptus genotypes with greater adaptability to these challenging environments and with greater nutrient use efficiency (Gonçalves et al., 2013 ). In this sense, the selection and hybridization of forest species adapted to specific environments through genetic breeding programs is essential to ensure sustainability and productivity, since using these hybrids can help increase input efficiency and the resilience of plantations to adverse environmental conditions (Bush et al., 2014). The search for species that are more efficient in potassium (K) use is particularly important, both because of the high demand and responsiveness of many Eucalyptus species to K fertilization and because of its role in water regulation, photosynthesis, and other physiological functions, especially in sites with severe water scarcity, high evapotranspiration, and poorly distributed rainfall (Hasanuzzaman, et al., 2018 ). Thus, the application of potassium fertilizers is one of the main factors in increasing the growth rate of Eucalyptus trees in tropical conditions (Laclau et al., 2009 ), which is widely cultivated in soils with low nutrients availability, notably K (Melo et al., 2016 ). The K is the main cation in the plant’s cells vacuole, being responsible for maintaining turgor, as well as acting in cell expansion and stomatal control (Maathuis, 2009 ; Marschner, 2012 ). Adequate K nutrition can also increase CO 2 assimilation in well-irrigated plants (Zhao et al., 2001 ; Santos et al., 2017 ), improving CO 2 diffusion in chloroplasts (Mateus et al., 2019 ; Sasaki et al., 2019), due to morphological and anatomical leaf characteristics altered by the plant's K nutritional status (Battie-Laclau et al., 2013 ; Tränkner et al., 2018 ). The physiological and nutritional behavior of hybrids such as Eucalyptus urophylla x E. grandis , conventionally used in Brazilian forestry, regarding K fertilization is already well documented in the literature. However, little is known about such behavior in Corymbia species, especially Corymbia citriodora subsp. variegata (CCV) and Corymbia henryi (CH) (Silva et al., 2017 ; Tambarussi et al., 2018 ; Araujo et al., 2021 ). The CCV and CH are little-explored species but breeding programs with such species have shown their great potential for commercial plantations, mainly for charcoal production, as they have high wood density and low sulfur content (Massuque et al., 2023 ). The CCV is widely planted by Australian farmers in the states of Queensland and New South Wales. This species is known for providing high value timber wood and for tolerating different climate conditions, which makes it a desirable species in a context of climate change, which tends to be more extreme for most genetic materials already cultivated (Lee, 2007 ; Lee et al., 2009 ). Investigating the physiological behavior of forest species that are potential alternatives to conventional ones, especially during the seedling stage, is essential to ensure greater diversity, resilience, and sustainability of forest plantations, especially in underutilized regions by forestry (Reinhardt et al., 2011 ). The main objective of this study was to evaluate the physiological, growth, and nutritional responses of Corymbia seedlings and Eucalyptus urophylla x E. grandis clones (AEC I144 and H13) under low K availability. We tested the hypothesis that (i) low soil K availability modulates height growth, stem diameter, leaf morphology of CCV and CH in the same way as in clones of E. urophylla x E. grandis ; (ii) species from the subgenus Corymbia are less susceptible to physiological stresses when subjected to low soil K availability compared to Eucalyptus clones; and (iii) Nutrient use efficiency is not modulated by low potassium availability in the soil; eucalyptus clones may be more efficient in water use when compared to Corymbias . Material and Methods Experimental conditions The experiment was conducted between February and May 2024, in a greenhouse with plastic covering (150 microns) at the forest nursery of the Luiz de Queiroz College of Agriculture (ESALQ/USP) in Piracicaba, São Paulo, Brazil (22°42′30″S, 47°38′00″W), with an altitude of 546 meters above sea level. The internal temperature in the greenhouse ranged between 19.6°C and 37.0°C. The soil used in the experiment was classified as a deep red-yellow latosol (Rocha et al., 2016). The soil was extracted from the 20–40 cm layer in an area occupied by Cerrado strictu sensu (Brazilian savannah) at the Forest Science Experimental Station of the Universidade de Sao Paulo in Itatinga, São Paulo, Brazil (23°10′S, 48°40′W). The soil was then air-dried sieved at 2 mm (9 mesh). A composite sample of this soil was submitted to chemical analysis, following the methods described by Raij et al. (2001). The soil chemical attributes obtained were: pH (CaCl 2 ) = 4.1; OM = 13.7 g kg⁻¹; P resin = 3.6 mg dm⁻³; K = 0.6 mmolc dm⁻³; Ca = 0.9 mmolc dm⁻³; Mg = 1 mmolc dm⁻³; Al + 3 = 11.8 mmolc dm⁻³; S = 10 mg dm⁻³; B = 0.1 mmolc dm⁻³; Cu = 1.1 mmolc dm − 3 ; Fe = 105.7 mmolc dm 3 ; Mn = 0.9 mmolc dm − 3 ; Zn = 0.1 mmolc dm − 3 ; H + Al = 56.7 mmolc.dm⁻³; CTC = 59.2 mmolc.dm⁻³; V% = 4 and m% = 82. A sample of the water used for irrigation was also analyzed, following the methods described by Franson ( 1995 ). The attributes of the water used for irrigation were: pH = 7.0; N-NH 3 = 0.2 mg L − 1 ; N-NO 3 = 12 mg L − 1 ; P = 0.01 mg L − 1 ; K = 4 mg L − 1 ; Ca = 12 mg L − 1 ; Mg = 2 mg L − 1 ; S = 147 mg L − 1 ; Na = 41 mg L − 1 ; Cl = 107 mg L − 1 ; Cu = 0.2 mg L − 1 ; Fe = 0.05 mg L − 1 ; Mn = 0.03 mg L − 1 and Zn 0.05 mg L − 1 . Experimental design and treatments The experimental design was completely randomized (CRD) in a 2x4 factorial arrangement, resulting in 8 combinations (treatments), with six replicates. The factors consisted of two cultivation conditions, one with and one without potassium fertilization (+ K and -K) (Factor 1) and four species of plants, consisting of two pure species propagated from seeds ( Corymbia citriodora subsp. Variegata - CVV and Corymbia henryi - CH) and two for cuttings of E. urophylla x E. grandis (clones I144 and H13). Each experimental unit consisted of a single three-month-old seedling, transplanted into a pot with a capacity for 5 kg of soil. Nutrient fertilization and growth conditions The experiment was conducted in a suspended bed and irrigated manually. Based on soil attributes and fertilization recommendations proposed by Novais et al. ( 1991 ) for greenhouse experiments. Using pure reagents for analysis (P.A.), separate solutions were prepared for each reagent in the laboratory, and after preparation, they were applied to the respective treatments using a graduated pipette. The amount of nutrients were supplied as follows: 60 mg of N (ammonium sulfate, 17.1% N); 200 mg of P 2 O 5 and 128 mg of Ca (calcium phosphate, 39.9% Ca and 20% P 2 O 5 ), 19 mg of Mg (magnesium sulfate, 20.2% Mg), 1 mg of B (boric acid, 16.2% B), 2 mg of Cu (copper sulfate, 40.5% Cu), and 4 mg of Zn (zinc sulfate, 39.8% Zn). The 100 mg of K (potassium chloride, 52.4% K) was applied only in the CCV + K, CH + K, I144 + K, and H13 + K treatments. Leaf water potential The water potential of the leaf (Ψf) was measured 180 days after transplanting (DAT). The Ψf was measured in two periods, before dawn (3:00 a.m.) when the plants were under minimal stress and around the middle of the day (1:00 p.m.) when stress was at its maximum. The measurement was made using fresh leaves into a Scholander pressure chamber, model 600 (Soil Moisture Equipment Corp., Santa Barbara, California-USA) (Scholander et al., 1965 ). Gas exchange At 180 DAT the plants were submitted to the measuring of leaf gas exchange. For this, an infrared gas analyzer (IRGA), model LI-6400 XT (LI-COR Biosciences Inc., Lincoln, USA) was used. The sensor was placed at the midpoint of the leaf, located at the third pair, in the branch at the middle third of the plant crown, with four replicates per treatment. The measurements were made between 9:00 and 10:30 a.m. Constant radiation of 1200 µmol m⁻² s⁻¹, CO₂ concentration of 400 µmol mol⁻¹ and ambient air temperature and humidity were used as parameters for the equipment. The CO 2 assimilation rate (A), stomatal conductance (gs), and transpiration (E) were measured. Water use efficiency (WUE) was estimated using the ratio between the CO 2 assimilation rate and transpiration (A/E). Plant growth At 180 DAT, the plants were harvested and separated into roots and shoot (stem + branches and leaves). The roots were washed in running water over a set of overlapping sieves with mesh sizes ranging from 20 to 2 mm. The roots were then sequentially washed as follows: 1) water solution with detergent, to solubilize soil particles; 2) distilled water, to remove detergent adhering to the sample; 3) 0.5% EDTA solution to remove ions adsorbed to the root surface; 4) distilled water to remove EDTA in contact with the sample, two times. After the washing process, the roots were placed on absorbent paper to remove the water adhering to their surface. Subsequently, the plant samples were dried in an air-forced oven (65°C), until constant weight. The dried plants were weighted on a semi-analytical balance to determine the root and shoot dry matter. Morphological analyses The specific leaf area (SLA) was measured at the same time as the above-ground biomass assessments. Each plant had its branches defoliated, then, the leaves were cleaned with absorbent paper and scanned using an HP Scanjet G2710 scanner (with a resolution of 300 dpi). The digital images of the leaves were processed using ImageJ software, in which the length (mm), width (mm), and leaf blade area (LBA) (mm 2 ) of each leaf were quantified. Subsequently, these samples were dried in an air-forced oven at 60–65°C to calculate the specific leaf area according to Eq. 1. $$\:SLA=\frac{LA\:of\:sample\:}{MS\:of\:sample}\:\:\:\:\:\:\:(Eq.\:1)$$ Where SLA = Specific leaf area (m² kg⁻¹); LA = Leaf area of the fresh base sample (m²); DM = Dry mass of the leaf sample (kg). At the moment of plant harvesting, leaves from the plants were sampled to analyze the polar and equatorial diameters of the stomata (µm) and stomatal density (nº mm 2 ). An impression was obtained from the abaxial region of the leaf blade, specifically from the median portion of each leaf. To do so, a small drop of colorless adhesive (Super Bonder®) was placed on a glass slide, and then the selected leaf portion was pressed against the slide long enough for the adhesive to mold to the surface of the leaf blade (Segatto et al., 2004 ). Nutrient stock and use efficiency To quantify nutrients concentration in the plant compartments, the plant samples from each pot were ground in a Willey mill with a 1 mm sieve. The leaf, stem+branch, and root samples were sent to the laboratory for quantifying the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), according to the methodology established by Malavolta et al. ( 1997 ). Nutrient stock was obtained by multiplying the dry biomass of each plant component by the respective nutrient concentration. Nutrient use efficiency (NUE) was obtained by dividing the total dry biomass (leaf, stem + branches, and roots in g-1) by the total stock of each nutrient in mg − 1 (Barros et al., 1986 ), according to Eq. 2. $$\:NUE=\frac{Total\:dry\:biomass\:\left({g}^{-1}\right)}{Total\:nutrient\:stock\:\left(m{g}^{-1}\right)\:}\:\:\:\:\:(Eq.\:2)$$ Data analysis The results were submitted to the Shapiro-Wilk normality test and the Bartlett test for homoscedasticity analyses. When necessary, Box-Cox transformation was performed. After that, statistical analysis of variance (ANOVA) and comparison of means were performed using the Tukey test ( p < 0.05). Principal component analysis (PCA) was also performed using the biomass, gas exchange, and nutrient stock data. Data processing and analysis were performed using R software (R Core Team, 2024). Results Leaf water potential For Ψf, there was no significant interaction between potassium fertilization conditions and plants. Differences were only found when these factors were analyzed separately. The -K and + K conditions did not significantly influence Ψf at 3:00 a.m., but affected this variable at 1:00 p.m. For the period from 3:00 a.m. to 1:00 p.m., the overall average was − 0.1 MPa, for both K fertilizations conditions. The Ψf of CH and I144 was 14% higher than CCV and H13 (Fig. 1 a). The overall Ψf in -K condition was 21% more negative at 1:00 p.m. The H13 clone was 49% less negative than the Corymbia species and 28% less negative than I144 (Fig. 1 b). Gas exchange For gas exchange, there was also no interaction between potassium fertilization conditions and plants. Such attributes were only significantly influenced when analyzed separately. There were no significant differences between the -K and + K conditions for any of the gas exchange variables. For A, the overall average was 9 µmolCO2m −2 s − 1 for fertilization and for genotypes (Fig. 2 a). Except for A, there were differences at the plants level for all variables. The gs for clone I144 was 35% higher than CH and H13, not differing from CCV (Fig. 2 b). The I144 transpired 36% more than CH, however, did not differ from CCV and H13 (Fig. 2 c). The I144 showed lower water use efficiency, 26% compared to CH, however, did not differ from CH and I144 (Fig. 2 d). Plant growth No significant interaction between the assessed factors was observed for biomass variables. Regarding biomass production from leaves and stem+branches, significant differences were observed only between plants. The CH produced 43% less leaves and 40% stem and branches compared to CCV, I144, and H13, which did not differ to each other in none of these compartments (Fig. 3 a, 3 b). Unlike the other compartments, root biomass was influenced by both potassium fertilization and plants. Plants at -K condition produced 23% less root biomass compared to those submitted to + K. The H13 presented the highest root biomass production, being 15% higher than I144 and 150% higher than Corymbia species, which did not differ from each other (Fig. 3 c). Morphological and anatomical attributes of leaves Although potassium fertilization did not promote major changes in the assessed morphological attributes, relevant differences were observed between plants for the variables LBA, SLA, Length, and Width. The overall average for LBA in both -K and + K conditions was 2781 mm². The LBA of H13 was 38% lower than the other plants. The SLA of the plants was reduced by 18% when the plants did not receive K. The SLA for H13 was 23% higher than I144 and 39% higher than the Corymbia species. The leaf length for CCV and CH was 28% higher than for the Eucalyptus clones. However, I144 was 28% greater than the leaf width of H13 and 11% greater than CCV and CH. (Table 1 ). Table 1 Morphological attributes of Corymbia and Eucalyptus leaves grown in potassium-deficient soil. Species LBA SLA Length Width mm² m² kg⁻¹ mm mm CCV 3064 a 9 bc 125 a 39 b CH 3314 a 7 c 122 a 44 b I144 2835 a 10 b 95 b 47 a H13 1912 b 13 a 83 b 34 c Potassium fertilization -K 2776 A 9 B 106 A 41 A +K 2786 A 11 A 106 A 40 A Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare plants. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey's test (p > 0.05). LBA - leaf blade area, SLA - Specific leaf area. Unlike the other morphological attributes, LA showed interaction between potassium fertilization and plants. In the -K condition the CCV had its LA reduced by 13%, CH by 11%, I144 and H13 by 39%, in comparison to the +K condition. When LA was analyzed within each fertilization condition, in -K the H13 was 48% and 44% higher than Corymbia species and the I144, respectively. Same pattern was observed in the +K condition, where the H13 presented a LA 53% and 28% higher than the Corymbia species and I144, respectively (Table 2). Table 2 Leaf area of Corymbia and Eucalyptus . Species -K +K _______________________________ m 2 _______________________________ CCV 0.14b cB 0.16 bcA CH 0.11 cB 0.13 cA I144 0.14 bB 0.23 bA H13 0.25 aB 0.32 aA Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey's test ( p > 0.05). The anatomical attributes of plant leaves were statistically different only among species. The number of stomata in I144 was 25% higher than in CCV and CH. However, the polar diameter of CCV and CH was 25% greater than that of H13, and CH did not differ from I144. The difference was more pronounced in the apolar diameter, where the difference between the Corymbia species and Eucalyptus clones was 35% (Table 3). Table 3 Anatomical attributes of leaves from Corymbia and Eucalyptus grown in potassium-deficient soil. Species Stomatal density Polar diameter of stoma Nonpolar diameter of stoma Nº mm -2 mm mm CCV 354 bc 19 ab 16 a CH 329 c 21 a 18 a I144 493 a 16 bc 11 b H13 432 b 15 c 10 b Potassium fertilization -K 413 a 18 a 13 a +K 395a 19 a 14 a Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey's test ( p > 0.05). Nutrient stock Regarding nutrient stock, significant interaction was found only for N and K. The total N stock in CCV plants grown in -K was 25% lower than in those grown in +K. Nevertheless, there was no difference between species, which presented an average stock of 0.36 g plant -1 of N. Under the +K condition, CH accumulated 23% less than CCV, which was not different from I144 and H13 (Fig. 4a). For the other macronutrients stocks presented significant differences only between species. Regarding P stock, it was 13% and 15% higher in CH when compared to I144 and H13 (Fig. 4b). The CCV and H13, when submitted to the +K condition, presented a K stock 33% higher than CH and I144. Under -K condition, I144 stood out with a 34% higher stock than the other species (Fig. 4c). The Corymbia species accumulated 25% more Ca than H13, while no difference was observed between CH and I144 (Fig. 4d). The I144 accumulated 16% more Mg than H13, but did not differ from Corymbia species (Fig. 4e). The CH presented the lowest S stock, accumulating 50% less S than the other species (Fig. 4f). Nutrient use efficiency Significant interaction was observed only for K, Ca, and Mg use efficiency. For the other macronutrients use efficiency, only a significant difference between species was verified, with the exception of N. The CH was 31% less efficient in P use than CCV, I144, and H13. Corymbia genotypes showed 25% greater S use efficiency than eucalyptus trees (Table 4). Plants submitte to +K condition were 23% more efficient in K use. CCV was 42% less efficient in -K, while H13 was 34% more efficient when grown in +K. The efficiency of H13 in Ca use was 71% higher than Corymbias and 17% higher than I144, considering the two conditions of potassium fertilization. Regarding genotypes, Eucalyptus plants were 47% more efficient than Corymbia species in -K. H13 was 29% more efficient than CCV and CH, and 18% more effcient than I144 in +K. CCV was 12% less efficient in Mg use in -K. There was no difference between genotypes into +K condition, and the average efficiency of the species was 0.6 g mg⁻¹. CCV in -K was 36% less efficient in Mg use compared to +K, while the other species were not different (Table 5). Table 4 Efficiency of N, P, and S use in plants grown in potassium-deficient soil. Genotypes N P S ------------------------------ g mg -1 --------------------------- CCV 0.10 a 0.63 a 0.92 b CH 0.13 a 0.45 b 1.35 a I144 0.11 a 0.64 a 1.06 b H13 0.13 a 0.70 a 1.24 a Potassium fertilization -K 0.12 a 0.58 a 0.54 a +K 0.11 a 0.63 a 0.60 a Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey's test (p > 0.05). Table 5 Interaction between genotypes and potassium fertilization for Ca and Mg use efficiency in plants grown in potassium-deficient soil. Genotypes K Ca Mg -K +K -K +K -K +K ----------------------------------------------- g mg -1 ----------------------------------------------- CCV 0.12 cB 0.17 bA 0.09 bA 0.10 bA 0.44 cB 0.60 bA CH 0.13 bB 0.18 bA 0.10 bA 0.13 bA 0.47 cA 0.49 cA I144 0.18 aB 0.17 bA 0.15 aB 0.14 aB 0.57 bA 0.58 bA H13 0.15 bB 0.23 aA 0.19 aA 0.17 aA 0.70 aA 0.75 aA Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey's test (p > 0.05). Principal Component Analysis (PCA) Principal Component Analysis showed that nutrient storage and root biomass had a higher degree of positive association with each other and were more positively responsive to genotypes I144 and H13 under +K conditions. On the other hand, WUE was more positively influenced by CH under -K conditions, suggesting a conservative strategy for water use. The CCV showed intermediate performance, while I144 and H13, without potassium addition, positioned themselves close to each other, reflecting less influence on the variables analyzed. These results indicate that potassium supply significantly modulates the nutritional and morphophysiological attributes of the evaluated species, with more expressive responses in I144 and H13 (Fig. 5). The variables analyzed showed low sensitivity to potassium fertilization. The greatest variations observed were associated to the species, which was expected due to the intrinsic characteristics of each one of the species assessed. Discussion Impact of potassium availability on the growth, morphology, and anatomy of Corymbia and Eucalyptus The genotypes showed contrasting behaviors in relation to Ψf. Under more stressful conditions, Eucalyptus maintained less negative Ψf values compared to Corymbia , which, at first, could indicate greater tolerance to water stress for these clones. However, the lower root biomass production observed in Corymbia may have contributed to the maintenance of higher water potentials, suggesting that high Ψf values are more associated with mechanisms to escape dehydration than with a lack of effective drought tolerance (Reddy, 2019). Fertilization with + K improved the Ψf of plants compared to -K, because K concentration controls stomatal closure (an efficient strategy to retain water in plant tissues), highlighting the essential role of this macronutrient in tolerance mechanisms to water stress (Egilla et al., 2005; Battie-Laclau et al., 2014). Previous studies report higher A in Eucalyptus clones fertilized with K in comparison to a condition without K fertilization (Mateus et al., 2019 ). BattieLaclau et al. (2013) showed that potassium fertilization increased the A of eucalyptus plants grown in K-deficient soil. This was not observed in this study, as the CO 2 assimilation rate did not differ between fertilization conditions or between Eucalyptus clones and Corymbia genotypes. Possible factors can be considered to explain the absence of response in A, such as the short period of seedlings exposure to K availability. Future studies with a longer period of exposure of genotypes to cultivation conditions will be relevant for better validation of these responses. In fact, Santos et al. ( 2020 ), investigating Eucalyptus clones submitted to K availability and deficiency over a period of more than 6 months, found that plant physiology was drastically altered in the absence of potassium fertilization. Another point worth noting is that the plants were not cultivated under water or light limitation. Therefore, the genetic materials probably had an optimized photosynthesis rate for the study conditions which may not have directly translated into a significant increase in the CO₂ assimilation rate, highlighting the species' efficiency in resources capturing (Yin and Struik, 2017 ). The non-application of K affected height growth. Plants that received potassium fertilization grew considerably more. This result reinforces the fundamental role of K in the plants biochemical and physiological processes (Taiz et al., 2017 ). This effect was also observed in root biomass production, since all plants were less efficient in producing this compartment when no potassium was applied. The availability of K influences fundamental physiological processes in plants, such as gas exchange, leaf water potential, growth, and nutrient uptake (Guo et al., 2019 ). In the present study, interesting interactions were observed between different species ( Eucalyptus and Corymbia ) and K availability, revealing how responses vary depending on genotype. The CH showed greater water use efficiency, followed by CCV and H13, suggesting that these genotypes have adaptations to optimize water use, which can be advantageous in water-restricted environments (Almeida et al., 2020 ; Câmara et al., 2020 ; Ullah et al., 2017 ). These differences indicate that potassium and water use efficiency varies with genetic material, highlighting the importance of choosing the appropriate genotype for each management condition and environment (Bush et al., 2015 ). Similarly, there were no major changes in morphological and anatomical aspects due to fertilization conditions, but again, contrasting differences were observed between genotypes. Although Corymbia has a larger leaf blade area compared to Eucalyptus clones, they presented lower LA and SLA. However, this is compensated by longer and wider leaves, resulting in a distinct canopy architecture that is possibly more efficient for intercepting diffuse light (Mattos et al., 2020 ). The literature shows that Eucalyptus plants with higher SLA can optimize light absorption, which is an indispensable aspect for plant growth (Battie-Laclau et al., 2013 ). Another interesting finding of this study is that both CCV and CH had significantly fewer stomata per mm² than clones I144 and H13. On the other hand, Corymbia stomata are larger, both in polar and apolar diameter, which may indicate a possible strategy for stomatal regulation and gas exchange in these genotypes (Bertolino et al., 2019 ). Plants with few large stomata tend to have lower photosynthetic rates compared to those with many small stomata, while higher stomatal density and size promote greater stomatal conductance and water loss (Franks et al., 2009 ; Drake et al., 2013 ; Yin et al., 2020 ). These aspects reinforce the relevance of the integrated study of leaf morphology and anatomy as indicators of physiological adaptation and productive potential in forest species. K availability modulates nutrition in Corymbia and Eucalyptus The differences in response to K availability observed among the species evaluated in this study highlight the preponderance of this factor in association with the application or non-application of this nutrient. Eucalyptus genotypes may respond differently to potassium availability and supply due to genetic characteristics that influence the capacity for absorption and utilization of this nutrient (Gonçalves et al., 2004 ), which may be intensified when comparing seed species with clonal species, as performed in the present study. Some species may be more tolerant to potassium deficiency, showing better efficiency in the use of this nutrient, as well as better adaptation to stress conditions, while other species may be more sensitive, showing significant decreases in photosynthesis rate and growth under conditions of low K availability (Mostofa et al., 2022 ). Although potassium fertilization conditions did not significantly influence most of the measured attributes, when analyzing the nutrient stock by plants, significant differences were identified between those treatments that received K fertilization and those treatments that did not. Corymbia stood out for presenting high K and Ca stocks in plant compartments compared to Eucalyptus clones. The high K stock in leaves and roots may be related to its important role in osmotic regulation, stomatal control, and transport of compounds in the plant (Taiz et al., 2017 ). Leaves, as plant components of intense transpiration and photosynthesis, require a high concentration of K to maintain osmotic balance and prevent excessive water loss (Wang et al., 2021 ). As leaves are areas of active growth and cell differentiation, there is a high demand for Ca to ensure the structural integrity of the membranes. Unlike K, Ca has low mobility within the plant after being absorbed by the roots; therefore, it tends to accumulate in the closest tissues, such as the roots themselves and young leaves in active growth (Zhang et al., 2025 ). This study observed a significant variation in absorption and accumulation capacity of plants regarding K and Ca. The high K and Ca stocks in the leaves and stems+branches of Corymbia can be explained by the greater efficiency of these species in absorbing these nutrients, reflecting the role of this nutrient in osmotic regulation and stomatal control, which are essential for maintaining osmotic balance, water stability, and compound transport (Arquero et al., 2006 ; Battie-Laclau et al., 2016 ). Additionally, the high concentration of K and Ca in the leaf tissues promoted higher stocks of these nutrients in this compartment of CCV and CH plants. In general, the stock of nutrients in the leaves was not affected by the absence or presence of K fertilization. Only the stocks of such nutrients were different between species. However, the same behavior was not observed in the roots, stems, and branches. The I144 and H13 were more efficient in the use of K and Ca. These clones require smaller amounts of nutrients to produce the same amount of biomass compared to less efficient species such as CCV and CH (Gazola et al., 2019). Principal component analysis integrated physiological, morphological, and nutritional variables, revealing patterns of genotype response to K availability that were not evident in univariate analyses. The I144 and H13 benefited from potassium fertilization, with greater nutrient storage and root development, while Corymbia showed a more conservative strategy, with greater water use efficiency. These results reinforce that different species adopt contrasting strategies to deal with limiting resources, highlighting the relevance of integrated responses in the selection of genetic materials in management and breeding programs (Cornut et al., 2023 ; Gazola et al., 2019). Conclusions The physiological assessments of Eucalyptus and Corymbia revealed that the response to potassium fertilization is highly dependent on the intrinsic characteristics of each genotype, independent of the genus, species or propagation method (ex. seed or cutting). On the other hand, clones of E. urophyla x E. grandis (e.g., I144 and H13) are more efficient in nutrient use when compared to Corymbia species (e.g., C. variegata and C. henry ). The I144 presented a high photosynthetic and gas exchange rate when compared to Corymbia species, which explains its high productivity. By prioritizing the conversion of CO2 into biomass, I144 may have low water use efficiency when compared to Corymbias . Declarations Funding This study was partially funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – under Finance Code 001. Additional financial support was provided by the Silviculture and Management Thematic Program at the Institute of Forest Research and Study (PTSM/IPEF). Competing interests The authors declare no conflict of interest. Acknowledgements We would like to thank the Coordination for the Improvement of Higher Education Personnel (CAPES/Brazil) (grant number Code 001). The authors also thank the Thematic Program on Forestry and Management of the Institute for Forest Research and Studies (PTSM/IPEF) for financial and technical support. We also thank the Department of Forest Sciences of the University of São Paulo, Luiz de Queiroz College of Agriculture (ESALQ-USP). Author contributions Maria Leidiane Reis Barreto: Methodology, Validation, Formal analysis, Research, Data curation, Writing - Original draft, Writing - Revision and editing, Visualization, Supervision, Project management. Cassio Rafael Costa dos Santos: Writing - Original draft, Writing - Revision and editing, Validation, Visualization. Adam da Cruz Rodrigues: Writing - Original Draft, Writing - Revision and Editing, Validation, Visualization. Felipe Tavares Lima: Writing - Original Draft, Writing - Revision and Editing, Validation, Visualization. Gleydson Vinicius dos Santos Silveira: Writing - Revision and Editing, Validation, Visualization. Huga Géssica Bento de Oliveira Sousa: Writing - Revision and Editing, Validation, Visualization. Antonio Leite Florentino: Writing - Original Draft, Writing - Revision and Editing, Validation, Visualization. José Leonardo de Moraes Gonçalves: Conceptualization, Methodology, Validation, Resources, Data Curation, Writing - Revision and Editing, Supervision, Project Management. Alexandre de Vicente Ferraz: Conceptualization, Methodology, Validation, Resources, Data Curation, Writing - Revision and Editing, Supervision, Project Management. 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Industrial Crops and Products 232:121226. https://doi.org/10.1016/j.indcrop.2025.121226 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 20 Feb, 2026 Reviewers invited by journal 20 Feb, 2026 Editor assigned by journal 19 Feb, 2026 First submitted to journal 18 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8846297","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":594231232,"identity":"46f5d7d1-d427-4f18-915f-1e7350951a87","order_by":0,"name":"Maria Leidiane Reis Barreto","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIiWNgGAWjYJCCAwwFDDwMh0HMChDBQ4wWA5iWM0RqYQBqAWlkYGBsI0KLbvvZhwd+GNjI8B1nfvbg47zD9uYMvMc+4NNidibd4GCPQRqP5GE2c8OZ2w4n7mzgS56BV8uBNIYDPAaHgYjBTJp32+EEgwM8xngdZnb+GcPBPwb/gVrYv0n/nXPYnrCWG2kMQCvAFplJMzYcZtxAWMszhsMyBslAv/CUSfYcS0/c2cyXTMBhacwf31TY2fOdP75N4keNtb05e+9hvFowgQEziRog0ToKRsEoGAWjABkAAKwhSOzXj+oLAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0001-7041-0572","institution":"Universidade de Sao Paulo","correspondingAuthor":true,"prefix":"","firstName":"Maria","middleName":"Leidiane Reis","lastName":"Barreto","suffix":""},{"id":594231233,"identity":"39761b45-0384-473c-b975-977e25519f71","order_by":1,"name":"Cassio Rafael Costa dos Santos","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Cassio","middleName":"Rafael Costa dos","lastName":"Santos","suffix":""},{"id":594231234,"identity":"bcf69ee1-a428-4512-953f-5e224e46bca6","order_by":2,"name":"Adam da Cruz Rodrigues","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Adam","middleName":"da Cruz","lastName":"Rodrigues","suffix":""},{"id":594231235,"identity":"c239a9b8-8485-4039-8a98-0b316b9b128f","order_by":3,"name":"Felipe Tavares Lima","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Felipe","middleName":"Tavares","lastName":"Lima","suffix":""},{"id":594231236,"identity":"8126bcc8-7892-42bf-ae81-a53fd5a5a456","order_by":4,"name":"Gleydson Vinicius dos Santos Silveira","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Gleydson","middleName":"Vinicius dos Santos","lastName":"Silveira","suffix":""},{"id":594231237,"identity":"a88ee1de-5ede-40f8-9315-d405b2513f5f","order_by":5,"name":"Huga Géssica Bento de Oliveira Sousa","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Huga","middleName":"Géssica Bento de Oliveira","lastName":"Sousa","suffix":""},{"id":594231238,"identity":"c693eacf-0151-4133-bc36-0424ab4b050c","order_by":6,"name":"Antonio Leite Florentino","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Antonio","middleName":"Leite","lastName":"Florentino","suffix":""},{"id":594231239,"identity":"bfc6f484-d103-425c-8208-21092a93e7d1","order_by":7,"name":"José Leonardo de Moraes Gonçalves","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"José","middleName":"Leonardo de Moraes","lastName":"Gonçalves","suffix":""},{"id":594231240,"identity":"27b007c8-4c04-4049-b36e-7488251946e2","order_by":8,"name":"Alexandre de Vicente Ferraz","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Alexandre","middleName":"de Vicente","lastName":"Ferraz","suffix":""}],"badges":[],"createdAt":"2026-02-11 02:37:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8846297/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8846297/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103351509,"identity":"9a4fd5ef-1274-4731-bb01-353fe7e49724","added_by":"auto","created_at":"2026-02-24 17:14:12","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":40983,"visible":true,"origin":"","legend":"\u003cp\u003eΨf at 3:00 a.m. (Fig. 1a) and Ψf at 1:00 p.m. (Fig. 1b) in plants grown in potassium-deficient soil. Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same capital or lowercase letters do not differ from each other according to Tukey's test (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8846297/v1/f8f9614b507ff77828131c18.png"},{"id":103351511,"identity":"5c701639-8a0b-46b0-affe-c9b37426ef50","added_by":"auto","created_at":"2026-02-24 17:14:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":103609,"visible":true,"origin":"","legend":"\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e assimilation rate - A (Fig. 2a), stomatal conductance - gs (Fig. 2b), transpiration - E (Fig. 2c), and water use efficiency - WUE (Fig. 2d) in plants grown in potassium-deficient soil. Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one same capital or lowercase letter do not differ from each other according to Tukey's test (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8846297/v1/069e1295dc065452ab8db335.png"},{"id":103507226,"identity":"80338533-0389-48ac-9780-611ab6e38679","added_by":"auto","created_at":"2026-02-26 13:40:44","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":62197,"visible":true,"origin":"","legend":"\u003cp\u003eBiomass of leaves (Fig. 3a), stems + branches (Fig. 3b), and roots (Fig. 3c) in plants grown in potassium-deficient soil. Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same capital or lowercase letters do not differ from each other according to Tukey's test (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8846297/v1/61a32c003629f6aa3cac7506.png"},{"id":103505949,"identity":"bb4fbf4d-5fef-4002-9e2f-d9e876c90c3f","added_by":"auto","created_at":"2026-02-26 13:33:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":101017,"visible":true,"origin":"","legend":"\u003cp\u003eStock of N (Fig. 4a), P (Fig. 4b), K (Fig. 4c), Ca (Fig. 4d), Mg (Fig. 4e), and S (Fig. 4f) in the leaf, stem + branch, and root of plants grown in potassium-deficient soil. Capital letters compare potassium fertilization (-K and +K). Lowercase letters compare genotypes and interaction between species and potassium fertilization. Means followed by at least one same capital or lowercase letter do not differ from each other according to Tukey's test (p \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8846297/v1/e225f49e587fff7387792212.png"},{"id":103351513,"identity":"8446fa60-684a-4813-aa1c-db9a386dc034","added_by":"auto","created_at":"2026-02-24 17:14:12","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":163609,"visible":true,"origin":"","legend":"\u003cp\u003ePrincipal component analysis (PCA) based on morphological, physiological, and nutritional characteristics of seedlings of four species grown in potassium-deficient soil. The ellipses represent 95% confidence intervals for each genotype × treatment combination. The arrows indicate the direction and contribution of each variable to the first two principal components (Dim1 = 48.7%; Dim2 = 22.9%).\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8846297/v1/e5373a5d42b3e700678c8a43.jpeg"},{"id":103515083,"identity":"02f4e8b6-eaf0-4eb1-bc11-8aaa885e8842","added_by":"auto","created_at":"2026-02-26 14:22:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1365677,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8846297/v1/546dd292-d4e8-46c9-bc3f-c7430d39f127.pdf"}],"financialInterests":"","formattedTitle":"Does low potassium availability modulate the physiological responses of Corymbia seedlings and Eucalyptus cuttings?","fulltext":[{"header":"Introduction","content":"\u003cp\u003eWith the expansion of the planted forests into areas with greater soil and climate constraints, it is important to pursue \u003cem\u003eEucalyptus\u003c/em\u003e genotypes with greater adaptability to these challenging environments and with greater nutrient use efficiency (Gon\u0026ccedil;alves et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). In this sense, the selection and hybridization of forest species adapted to specific environments through genetic breeding programs is essential to ensure sustainability and productivity, since using these hybrids can help increase input efficiency and the resilience of plantations to adverse environmental conditions (Bush et al., 2014). The search for species that are more efficient in potassium (K) use is particularly important, both because of the high demand and responsiveness of many \u003cem\u003eEucalyptus\u003c/em\u003e species to K fertilization and because of its role in water regulation, photosynthesis, and other physiological functions, especially in sites with severe water scarcity, high evapotranspiration, and poorly distributed rainfall (Hasanuzzaman, et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Thus, the application of potassium fertilizers is one of the main factors in increasing the growth rate of \u003cem\u003eEucalyptus\u003c/em\u003e trees in tropical conditions (Laclau et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), which is widely cultivated in soils with low nutrients availability, notably K (Melo et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe K is the main cation in the plant\u0026rsquo;s cells vacuole, being responsible for maintaining turgor, as well as acting in cell expansion and stomatal control (Maathuis, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Marschner, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Adequate K nutrition can also increase CO\u003csub\u003e2\u003c/sub\u003e assimilation in well-irrigated plants (Zhao et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Santos et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), improving CO\u003csub\u003e2\u003c/sub\u003e diffusion in chloroplasts (Mateus et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Sasaki et al., 2019), due to morphological and anatomical leaf characteristics altered by the plant's K nutritional status (Battie-Laclau et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Tr\u0026auml;nkner et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The physiological and nutritional behavior of hybrids such as \u003cem\u003eEucalyptus urophylla x E. grandis\u003c/em\u003e, conventionally used in Brazilian forestry, regarding K fertilization is already well documented in the literature. However, little is known about such behavior in \u003cem\u003eCorymbia\u003c/em\u003e species, especially \u003cem\u003eCorymbia citriodora\u003c/em\u003e subsp. \u003cem\u003evariegata\u003c/em\u003e (CCV) and \u003cem\u003eCorymbia henryi\u003c/em\u003e (CH) (Silva et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Tambarussi et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Araujo et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe CCV and CH are little-explored species but breeding programs with such species have shown their great potential for commercial plantations, mainly for charcoal production, as they have high wood density and low sulfur content (Massuque et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The CCV is widely planted by Australian farmers in the states of Queensland and New South Wales. This species is known for providing high value timber wood and for tolerating different climate conditions, which makes it a desirable species in a context of climate change, which tends to be more extreme for most genetic materials already cultivated (Lee, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Lee et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eInvestigating the physiological behavior of forest species that are potential alternatives to conventional ones, especially during the seedling stage, is essential to ensure greater diversity, resilience, and sustainability of forest plantations, especially in underutilized regions by forestry (Reinhardt et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The main objective of this study was to evaluate the physiological, growth, and nutritional responses of \u003cem\u003eCorymbia\u003c/em\u003e seedlings and \u003cem\u003eEucalyptus urophylla\u003c/em\u003e x \u003cem\u003eE. grandis\u003c/em\u003e clones (AEC I144 and H13) under low K availability. We tested the hypothesis that (i) low soil K availability modulates height growth, stem diameter, leaf morphology of CCV and CH in the same way as in clones of \u003cem\u003eE. urophylla x E. grandis\u003c/em\u003e; (ii) species from the subgenus \u003cem\u003eCorymbia\u003c/em\u003e are less susceptible to physiological stresses when subjected to low soil K availability compared to \u003cem\u003eEucalyptus\u003c/em\u003e clones; and (iii) Nutrient use efficiency is not modulated by low potassium availability in the soil; eucalyptus clones may be more efficient in water use when compared to \u003cem\u003eCorymbias\u003c/em\u003e.\u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eExperimental conditions\u003c/h2\u003e \u003cp\u003eThe experiment was conducted between February and May 2024, in a greenhouse with plastic covering (150 microns) at the forest nursery of the Luiz de Queiroz College of Agriculture (ESALQ/USP) in Piracicaba, S\u0026atilde;o Paulo, Brazil (22\u0026deg;42\u0026prime;30\u0026Prime;S, 47\u0026deg;38\u0026prime;00\u0026Prime;W), with an altitude of 546 meters above sea level. The internal temperature in the greenhouse ranged between 19.6\u0026deg;C and 37.0\u0026deg;C. The soil used in the experiment was classified as a deep red-yellow latosol (Rocha et al., 2016). The soil was extracted from the 20\u0026ndash;40 cm layer in an area occupied by Cerrado \u003cem\u003estrictu sensu\u003c/em\u003e (Brazilian savannah) at the Forest Science Experimental Station of the Universidade de Sao Paulo in Itatinga, S\u0026atilde;o Paulo, Brazil (23\u0026deg;10\u0026prime;S, 48\u0026deg;40\u0026prime;W). The soil was then air-dried sieved at 2 mm (9 mesh).\u003c/p\u003e \u003cp\u003eA composite sample of this soil was submitted to chemical analysis, following the methods described by Raij et al. (2001). The soil chemical attributes obtained were: pH (CaCl\u003csub\u003e2\u003c/sub\u003e)\u0026thinsp;=\u0026thinsp;4.1; OM\u0026thinsp;=\u0026thinsp;13.7 g kg⁻\u0026sup1;; P\u003csub\u003eresin\u003c/sub\u003e = 3.6 mg dm⁻\u0026sup3;; K\u0026thinsp;=\u0026thinsp;0.6 mmolc dm⁻\u0026sup3;; Ca\u0026thinsp;=\u0026thinsp;0.9 mmolc dm⁻\u0026sup3;; Mg\u0026thinsp;=\u0026thinsp;1 mmolc dm⁻\u0026sup3;; Al\u0026thinsp;+\u0026thinsp;3\u0026thinsp;=\u0026thinsp;11.8 mmolc dm⁻\u0026sup3;; S\u0026thinsp;=\u0026thinsp;10 mg dm⁻\u0026sup3;; B\u0026thinsp;=\u0026thinsp;0.1 mmolc dm⁻\u0026sup3;; Cu\u0026thinsp;=\u0026thinsp;1.1 mmolc dm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e; Fe\u0026thinsp;=\u0026thinsp;105.7 mmolc dm\u003csup\u003e3\u003c/sup\u003e; Mn\u0026thinsp;=\u0026thinsp;0.9 mmolc dm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e; Zn\u0026thinsp;=\u0026thinsp;0.1 mmolc dm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e; H\u0026thinsp;+\u0026thinsp;Al\u0026thinsp;=\u0026thinsp;56.7 mmolc.dm⁻\u0026sup3;; CTC\u0026thinsp;=\u0026thinsp;59.2 mmolc.dm⁻\u0026sup3;; V% = 4 and m% = 82. A sample of the water used for irrigation was also analyzed, following the methods described by Franson (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). The attributes of the water used for irrigation were: pH\u0026thinsp;=\u0026thinsp;7.0; N-NH\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.2 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; N-NO\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;12 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; P\u0026thinsp;=\u0026thinsp;0.01 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; K\u0026thinsp;=\u0026thinsp;4 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Ca\u0026thinsp;=\u0026thinsp;12 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Mg\u0026thinsp;=\u0026thinsp;2 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; S\u0026thinsp;=\u0026thinsp;147 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Na\u0026thinsp;=\u0026thinsp;41 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Cl\u0026thinsp;=\u0026thinsp;107 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Cu\u0026thinsp;=\u0026thinsp;0.2 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Fe\u0026thinsp;=\u0026thinsp;0.05 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Mn\u0026thinsp;=\u0026thinsp;0.03 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Zn 0.05 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eExperimental design and treatments\u003c/h3\u003e\n\u003cp\u003eThe experimental design was completely randomized (CRD) in a 2x4 factorial arrangement, resulting in 8 combinations (treatments), with six replicates. The factors consisted of two cultivation conditions, one with and one without potassium fertilization (+\u0026thinsp;K and -K) (Factor 1) and four species of plants, consisting of two pure species propagated from seeds (\u003cem\u003eCorymbia citriodora\u003c/em\u003e subsp. \u003cem\u003eVariegata\u003c/em\u003e - CVV and \u003cem\u003eCorymbia henryi\u003c/em\u003e - CH) and two for cuttings of \u003cem\u003eE. urophylla\u003c/em\u003e x \u003cem\u003eE. grandis\u003c/em\u003e (clones I144 and H13). Each experimental unit consisted of a single three-month-old seedling, transplanted into a pot with a capacity for 5 kg of soil.\u003c/p\u003e\n\u003ch3\u003eNutrient fertilization and growth conditions\u003c/h3\u003e\n\u003cp\u003eThe experiment was conducted in a suspended bed and irrigated manually. Based on soil attributes and fertilization recommendations proposed by Novais et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1991\u003c/span\u003e) for greenhouse experiments. Using pure reagents for analysis (P.A.), separate solutions were prepared for each reagent in the laboratory, and after preparation, they were applied to the respective treatments using a graduated pipette. The amount of nutrients were supplied as follows: 60 mg of N (ammonium sulfate, 17.1% N); 200 mg of P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e and 128 mg of Ca (calcium phosphate, 39.9% Ca and 20% P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e), 19 mg of Mg (magnesium sulfate, 20.2% Mg), 1 mg of B (boric acid, 16.2% B), 2 mg of Cu (copper sulfate, 40.5% Cu), and 4 mg of Zn (zinc sulfate, 39.8% Zn). The 100 mg of K (potassium chloride, 52.4% K) was applied only in the CCV\u0026thinsp;+\u0026thinsp;K, CH\u0026thinsp;+\u0026thinsp;K, I144\u0026thinsp;+\u0026thinsp;K, and H13\u0026thinsp;+\u0026thinsp;K treatments.\u003c/p\u003e\n\u003ch3\u003eLeaf water potential\u003c/h3\u003e\n\u003cp\u003eThe water potential of the leaf (Ψf) was measured 180 days after transplanting (DAT). The Ψf was measured in two periods, before dawn (3:00 a.m.) when the plants were under minimal stress and around the middle of the day (1:00 p.m.) when stress was at its maximum. The measurement was made using fresh leaves into a Scholander pressure chamber, model 600 (Soil Moisture Equipment Corp., Santa Barbara, California-USA) (Scholander et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1965\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eGas exchange\u003c/h3\u003e\n\u003cp\u003eAt 180 DAT the plants were submitted to the measuring of leaf gas exchange. For this, an infrared gas analyzer (IRGA), model LI-6400 XT (LI-COR Biosciences Inc., Lincoln, USA) was used. The sensor was placed at the midpoint of the leaf, located at the third pair, in the branch at the middle third of the plant crown, with four replicates per treatment. The measurements were made between 9:00 and 10:30 a.m. Constant radiation of 1200 \u0026micro;mol m⁻\u0026sup2; s⁻\u0026sup1;, CO₂ concentration of 400 \u0026micro;mol mol⁻\u0026sup1; and ambient air temperature and humidity were used as parameters for the equipment. The CO\u003csub\u003e2\u003c/sub\u003e assimilation rate (A), stomatal conductance (gs), and transpiration (E) were measured. Water use efficiency (WUE) was estimated using the ratio between the CO\u003csub\u003e2\u003c/sub\u003e assimilation rate and transpiration (A/E).\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePlant growth\u003c/h2\u003e \u003cp\u003eAt 180 DAT, the plants were harvested and separated into roots and shoot (stem\u0026thinsp;+\u0026thinsp;branches and leaves). The roots were washed in running water over a set of overlapping sieves with mesh sizes ranging from 20 to 2 mm. The roots were then sequentially washed as follows: 1) water solution with detergent, to solubilize soil particles; 2) distilled water, to remove detergent adhering to the sample; 3) 0.5% EDTA solution to remove ions adsorbed to the root surface; 4) distilled water to remove EDTA in contact with the sample, two times. After the washing process, the roots were placed on absorbent paper to remove the water adhering to their surface. Subsequently, the plant samples were dried in an air-forced oven (65\u0026deg;C), until constant weight. The dried plants were weighted on a semi-analytical balance to determine the root and shoot dry matter.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMorphological analyses\u003c/h3\u003e\n\u003cp\u003eThe specific leaf area (SLA) was measured at the same time as the above-ground biomass assessments. Each plant had its branches defoliated, then, the leaves were cleaned with absorbent paper and scanned using an HP Scanjet G2710 scanner (with a resolution of 300 dpi). The digital images of the leaves were processed using ImageJ software, in which the length (mm), width (mm), and leaf blade area (LBA) (mm\u003csup\u003e2\u003c/sup\u003e) of each leaf were quantified. Subsequently, these samples were dried in an air-forced oven at 60\u0026ndash;65\u0026deg;C to calculate the specific leaf area according to Eq.\u0026nbsp;1.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:SLA=\\frac{LA\\:of\\:sample\\:}{MS\\:of\\:sample}\\:\\:\\:\\:\\:\\:\\:(Eq.\\:1)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere SLA\u0026thinsp;=\u0026thinsp;Specific leaf area (m\u0026sup2; kg⁻\u0026sup1;); LA\u0026thinsp;=\u0026thinsp;Leaf area of the fresh base sample (m\u0026sup2;); DM\u0026thinsp;=\u0026thinsp;Dry mass of the leaf sample (kg).\u003c/p\u003e \u003cp\u003eAt the moment of plant harvesting, leaves from the plants were sampled to analyze the polar and equatorial diameters of the stomata (\u0026micro;m) and stomatal density (n\u0026ordm; mm\u003csup\u003e2\u003c/sup\u003e). An impression was obtained from the abaxial region of the leaf blade, specifically from the median portion of each leaf. To do so, a small drop of colorless adhesive (Super Bonder\u0026reg;) was placed on a glass slide, and then the selected leaf portion was pressed against the slide long enough for the adhesive to mold to the surface of the leaf blade (Segatto et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eNutrient stock and use efficiency\u003c/h3\u003e\n\u003cp\u003eTo quantify nutrients concentration in the plant compartments, the plant samples from each pot were ground in a Willey mill with a 1 mm sieve. The leaf, stem+branch, and root samples were sent to the laboratory for quantifying the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), according to the methodology established by Malavolta et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). Nutrient stock was obtained by multiplying the dry biomass of each plant component by the respective nutrient concentration. Nutrient use efficiency (NUE) was obtained by dividing the total dry biomass (leaf, stem\u0026thinsp;+\u0026thinsp;branches, and roots in g-1) by the total stock of each nutrient in mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Barros et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1986\u003c/span\u003e), according to Eq.\u0026nbsp;2.\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:NUE=\\frac{Total\\:dry\\:biomass\\:\\left({g}^{-1}\\right)}{Total\\:nutrient\\:stock\\:\\left(m{g}^{-1}\\right)\\:}\\:\\:\\:\\:\\:(Eq.\\:2)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eData analysis\u003c/h2\u003e \u003cp\u003eThe results were submitted to the Shapiro-Wilk normality test and the Bartlett test for homoscedasticity analyses. When necessary, Box-Cox transformation was performed. After that, statistical analysis of variance (ANOVA) and comparison of means were performed using the Tukey test (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Principal component analysis (PCA) was also performed using the biomass, gas exchange, and nutrient stock data. Data processing and analysis were performed using R software (R Core Team, 2024).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eLeaf water potential\u003c/h2\u003e \u003cp\u003eFor Ψf, there was no significant interaction between potassium fertilization conditions and plants. Differences were only found when these factors were analyzed separately. The -K and +\u0026thinsp;K conditions did not significantly influence Ψf at 3:00 a.m., but affected this variable at 1:00 p.m. For the period from 3:00 a.m. to 1:00 p.m., the overall average was \u0026minus;\u0026thinsp;0.1 MPa, for both K fertilizations conditions. The Ψf of CH and I144 was 14% higher than CCV and H13 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). The overall Ψf in -K condition was 21% more negative at 1:00 p.m. The H13 clone was 49% less negative than the \u003cem\u003eCorymbia\u003c/em\u003e species and 28% less negative than I144 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eGas exchange\u003c/h2\u003e \u003cp\u003eFor gas exchange, there was also no interaction between potassium fertilization conditions and plants. Such attributes were only significantly influenced when analyzed separately. There were no significant differences between the -K and +\u0026thinsp;K conditions for any of the gas exchange variables. For A, the overall average was 9 \u0026micro;molCO2m\u003csup\u003e\u0026minus;2\u003c/sup\u003es\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for fertilization and for genotypes (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). Except for A, there were differences at the plants level for all variables. The gs for clone I144 was 35% higher than CH and H13, not differing from CCV (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). The I144 transpired 36% more than CH, however, did not differ from CCV and H13 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). The I144 showed lower water use efficiency, 26% compared to CH, however, did not differ from CH and I144 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003ePlant growth\u003c/h2\u003e \u003cp\u003eNo significant interaction between the assessed factors was observed for biomass variables. Regarding biomass production from leaves and stem+branches, significant differences were observed only between plants. The CH produced 43% less leaves and 40% stem and branches compared to CCV, I144, and H13, which did not differ to each other in none of these compartments (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). Unlike the other compartments, root biomass was influenced by both potassium fertilization and plants. Plants at -K condition produced 23% less root biomass compared to those submitted to +\u0026thinsp;K. The H13 presented the highest root biomass production, being 15% higher than I144 and 150% higher than \u003cem\u003eCorymbia\u003c/em\u003e species, which did not differ from each other (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eMorphological and anatomical attributes of leaves\u003c/h2\u003e \u003cp\u003eAlthough potassium fertilization did not promote major changes in the assessed morphological attributes, relevant differences were observed between plants for the variables LBA, SLA, Length, and Width. The overall average for LBA in both -K and +\u0026thinsp;K conditions was 2781 mm\u0026sup2;. The LBA of H13 was 38% lower than the other plants. The SLA of the plants was reduced by 18% when the plants did not receive K. The SLA for H13 was 23% higher than I144 and 39% higher than the \u003cem\u003eCorymbia\u003c/em\u003e species. The leaf length for CCV and CH was 28% higher than for the \u003cem\u003eEucalyptus\u003c/em\u003e clones. However, I144 was 28% greater than the leaf width of H13 and 11% greater than CCV and CH. (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e Morphological attributes of \u003cem\u003eCorymbia\u003c/em\u003e and \u003cem\u003eEucalyptus\u003c/em\u003e leaves grown in potassium-deficient soil. \u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"611\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 129px;\"\u003e\n \u003cp\u003eLBA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 135px;\"\u003e\n \u003cp\u003eSLA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 164px;\"\u003e\n \u003cp\u003eLength\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 100px;\"\u003e\n \u003cp\u003eWidth\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003emm\u0026sup2;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003em\u0026sup2; kg⁻\u0026sup1;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 164px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eCCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e3064 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e9 bc\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 164px;\"\u003e\n \u003cp\u003e125 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e39 b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eCH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e3314 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e7 c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 164px;\"\u003e\n \u003cp\u003e122 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e44 b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eI144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e2835 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e10 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 164px;\"\u003e\n \u003cp\u003e95 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e47 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eH13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e1912 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e13 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 164px;\"\u003e\n \u003cp\u003e83 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e34 c\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 511px;\"\u003e\n \u003cp\u003ePotassium fertilization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003e-K\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e2776 A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e9 B\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 164px;\"\u003e\n \u003cp\u003e106 A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e41 A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003e+K\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e2786 A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 135px;\"\u003e\n \u003cp\u003e11 A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 164px;\"\u003e\n \u003cp\u003e106 A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 100px;\"\u003e\n \u003cp\u003e40 A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 611px;\"\u003e\n \u003cp\u003eCapital letters compare potassium fertilization (-K and +K). Lowercase letters compare plants. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey\u0026apos;s test (p \u0026gt; 0.05). LBA - leaf blade area, SLA - Specific leaf area. \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eUnlike the other morphological attributes, LA showed interaction between potassium fertilization and plants. In the -K condition the CCV had its LA reduced by 13%, CH by 11%, I144 and H13 by 39%, in comparison to the +K condition. When LA was analyzed within each fertilization condition, in -K the H13 was 48% and 44% higher than \u003cem\u003eCorymbia\u0026nbsp;\u003c/em\u003especies and the I144, respectively. Same pattern was observed in the +K condition, where the H13 presented a LA 53% and 28% higher than the \u003cem\u003eCorymbia\u0026nbsp;\u003c/em\u003especies and I144, respectively (Table 2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Leaf area of \u003cem\u003eCorymbia\u003c/em\u003e and \u003cem\u003eEucalyptus\u003c/em\u003e.\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"627\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 149px;\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e-K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e+K\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 149px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 478px;\"\u003e\n \u003cp\u003e\u003csup\u003e_______________________________\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e \u003csup\u003e_______________________________\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 149px;\"\u003e\n \u003cp\u003eCCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.14b cB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.16 bcA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 149px;\"\u003e\n \u003cp\u003eCH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.11 cB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.13 cA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 149px;\"\u003e\n \u003cp\u003eI144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.14 bB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.23 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 149px;\"\u003e\n \u003cp\u003e\u0026nbsp;H13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.25 aB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 239px;\"\u003e\n \u003cp\u003e0.32 aA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\" style=\"width: 627px;\"\u003e\n \u003cp\u003eCapital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey\u0026apos;s test (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05). \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe anatomical attributes of plant leaves were statistically different only among species. The number of stomata in I144 was 25% higher than in CCV and CH. However, the polar diameter of CCV and CH was 25% greater than that of H13, and CH did not differ from I144. The difference was more pronounced in the apolar diameter, where the difference between the \u003cem\u003eCorymbia\u003c/em\u003e species and \u003cem\u003eEucalyptus\u003c/em\u003e clones was 35% (Table 3). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u003c/strong\u003e Anatomical attributes of leaves from \u003cem\u003eCorymbia\u003c/em\u003e and \u003cem\u003eEucalyptus\u003c/em\u003e grown in potassium-deficient soil.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"628\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003eStomatal density\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003ePolar diameter of stoma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003eNonpolar diameter of stoma\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003eN\u0026ordm; mm\u003csup\u003e-2\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003emm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eCCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003e354 bc\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003e19 ab\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003e16 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eCH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003e329 c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003e21 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003e18 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eI144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003e493 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003e16 bc\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003e11 b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eH13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003e432 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003e15 c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003e10 b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 628px;\"\u003e\n \u003cp\u003ePotassium fertilization\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e-K\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003e413 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003e18 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003e13 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003e+K\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 158px;\"\u003e\n \u003cp\u003e395a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 165px;\"\u003e\n \u003cp\u003e19 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 201px;\"\u003e\n \u003cp\u003e14 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 628px;\"\u003e\n \u003cp\u003eCapital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey\u0026apos;s test (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003eNutrient stock\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eRegarding nutrient stock, significant interaction was found only for N and K. The total N stock in CCV plants grown in -K was 25% lower than in those grown in +K. Nevertheless, there was no difference between species, which presented an average stock of 0.36 g plant\u003csup\u003e-1\u003c/sup\u003e of N. Under the +K condition, CH accumulated 23% less than CCV, which was not different from I144 and H13 (Fig. 4a). For the other macronutrients stocks presented significant differences only between species. Regarding P stock, it was 13% and 15% higher in CH when compared to I144 and H13 (Fig. 4b). The CCV and H13, when submitted to the +K condition, presented a K stock 33% higher than CH and I144. Under -K condition, I144 stood out with a 34% higher stock than the other species (Fig. 4c). The \u003cem\u003eCorymbia\u003c/em\u003e species accumulated 25% more Ca than H13, while no difference was observed between CH and I144 (Fig. 4d). The I144 accumulated 16% more Mg than H13, but did not differ from \u003cem\u003eCorymbia\u003c/em\u003e species (Fig. 4e). \u0026nbsp;The CH presented the lowest S stock, accumulating 50% less S than the other species (Fig. 4f). \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eNutrient use efficiency\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eSignificant interaction was observed only for K, Ca, and Mg use efficiency. For the other macronutrients use efficiency, only a significant difference between species was verified, with the exception of N. The CH was 31% less efficient in P use than CCV, I144, and H13. \u003cem\u003eCorymbia\u003c/em\u003e genotypes showed 25% greater S use efficiency than eucalyptus trees (Table 4). Plants submitte to +K condition were 23% more efficient in K use. CCV was 42% less efficient in -K, while H13 was 34% more efficient when grown in +K. The efficiency of H13 in Ca use was 71% higher than Corymbias and 17% higher than I144, considering the two conditions of potassium fertilization. Regarding genotypes, \u003cem\u003eEucalyptus\u003c/em\u003e plants were 47% more efficient than \u003cem\u003eCorymbia\u003c/em\u003e species in -K. H13 was 29% more efficient than CCV and CH, and 18% more effcient than I144 in +K. CCV was 12% less efficient in Mg use in -K. There was no difference between genotypes into +K condition, and the average efficiency of the species was 0.6 g mg⁻\u0026sup1;. CCV in -K was 36% less efficient in Mg use compared to +K, while the other species were not different (Table 5).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4\u003c/strong\u003e Efficiency of N, P, and S use in plants grown in potassium-deficient soil.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"618\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003eGenotypes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003eN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003eP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003eS\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 618px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;------------------------------ g mg\u003csup\u003e-1\u003c/sup\u003e---------------------------\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003eCCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0.10 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0.63 a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.92 b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003eCH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0.13 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0.45 b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e1.35 a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003eI144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0.11 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0.64 a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u0026nbsp;1.06 b\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003eH13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0.13 a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0.70 a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u0026nbsp;1.24 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 618px;\"\u003e\n \u003cp\u003ePotassium fertilization\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003e-K\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0.12\u0026nbsp;a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0.58 a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.54 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 219px;\"\u003e\n \u003cp\u003e+K\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 141px;\"\u003e\n \u003cp\u003e0.11\u0026nbsp;a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 143px;\"\u003e\n \u003cp\u003e0.63 a\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 115px;\"\u003e\n \u003cp\u003e\u0026nbsp;0.60 a\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\" style=\"width: 618px;\"\u003e\n \u003cp\u003eCapital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey\u0026apos;s test (p \u0026gt; 0.05).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5\u003c/strong\u003e Interaction between genotypes and potassium fertilization for Ca and Mg use efficiency in plants grown in potassium-deficient soil.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"629\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 101px;\"\u003e\n \u003cp\u003eGenotypes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 176px;\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 176px;\"\u003e\n \u003cp\u003eCa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 176px;\"\u003e\n \u003cp\u003eMg\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 82px;\"\u003e\n \u003cp\u003e-K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e+K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e-K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e+K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e-K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 88px;\"\u003e\n \u003cp\u003e+K\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\" style=\"width: 629px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; ----------------------------------------------- g mg\u003csup\u003e-1\u003c/sup\u003e-----------------------------------------------\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 101px;\"\u003e\n \u003cp\u003eCCV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 82px;\"\u003e\n \u003cp\u003e0.12 cB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e0.17 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.09 bA\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.10 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.44 cB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.60 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 101px;\"\u003e\n \u003cp\u003eCH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 82px;\"\u003e\n \u003cp\u003e0.13 bB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e0.18 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.10 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.13 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.47 cA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.49 cA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 101px;\"\u003e\n \u003cp\u003eI144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 82px;\"\u003e\n \u003cp\u003e0.18 aB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e0.17 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.15 aB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.14 aB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.57 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.58 bA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp;H13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 82px;\"\u003e\n \u003cp\u003e0.15 bB\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 93px;\"\u003e\n \u003cp\u003e0.23 aA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.19 aA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.17 aA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.70 aA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 88px;\"\u003e\n \u003cp\u003e0.75 aA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\" style=\"width: 629px;\"\u003e\n \u003cp\u003eCapital letters compare potassium fertilization (-K and +K). Lowercase letters compare species. Means followed by at least one of the same uppercase or lowercase letters do not differ from each other according to Tukey\u0026apos;s test (p \u0026gt; 0.05).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003ePrincipal Component Analysis (PCA)\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePrincipal Component Analysis showed that nutrient storage and root biomass had a higher degree of positive association with each other and were more positively responsive to genotypes I144 and H13 under +K conditions. On the other hand, WUE was more positively influenced by CH under -K conditions, suggesting a conservative strategy for water use. The CCV showed intermediate performance, while I144 and H13, without potassium addition, positioned themselves close to each other, reflecting less influence on the variables analyzed. These results indicate that potassium supply significantly modulates the nutritional and morphophysiological attributes of the evaluated species, with more expressive responses in I144 and H13 (Fig. 5). The variables analyzed showed low sensitivity to potassium fertilization. The greatest variations observed were associated to the species, which was expected due to the intrinsic characteristics of each one of the species assessed.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eImpact of potassium availability on the growth, morphology, and anatomy of Corymbia and Eucalyptus\u003c/h2\u003e \u003cp\u003eThe genotypes showed contrasting behaviors in relation to Ψf. Under more stressful conditions, \u003cem\u003eEucalyptus\u003c/em\u003e maintained less negative Ψf values compared to \u003cem\u003eCorymbia\u003c/em\u003e, which, at first, could indicate greater tolerance to water stress for these clones. However, the lower root biomass production observed in \u003cem\u003eCorymbia\u003c/em\u003e may have contributed to the maintenance of higher water potentials, suggesting that high Ψf values are more associated with mechanisms to escape dehydration than with a lack of effective drought tolerance (Reddy, 2019). Fertilization with +\u0026thinsp;K improved the Ψf of plants compared to -K, because K concentration controls stomatal closure (an efficient strategy to retain water in plant tissues), highlighting the essential role of this macronutrient in tolerance mechanisms to water stress (Egilla et al., 2005; Battie-Laclau et al., 2014).\u003c/p\u003e \u003cp\u003ePrevious studies report higher A in \u003cem\u003eEucalyptus\u003c/em\u003e clones fertilized with K in comparison to a condition without K fertilization (Mateus et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). BattieLaclau et al. (2013) showed that potassium fertilization increased the A of eucalyptus plants grown in K-deficient soil. This was not observed in this study, as the CO\u003csub\u003e2\u003c/sub\u003e assimilation rate did not differ between fertilization conditions or between \u003cem\u003eEucalyptus\u003c/em\u003e clones and \u003cem\u003eCorymbia\u003c/em\u003e genotypes. Possible factors can be considered to explain the absence of response in A, such as the short period of seedlings exposure to K availability. Future studies with a longer period of exposure of genotypes to cultivation conditions will be relevant for better validation of these responses.\u003c/p\u003e \u003cp\u003eIn fact, Santos et al. (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), investigating \u003cem\u003eEucalyptus\u003c/em\u003e clones submitted to K availability and deficiency over a period of more than 6 months, found that plant physiology was drastically altered in the absence of potassium fertilization. Another point worth noting is that the plants were not cultivated under water or light limitation. Therefore, the genetic materials probably had an optimized photosynthesis rate for the study conditions which may not have directly translated into a significant increase in the CO₂ assimilation rate, highlighting the species' efficiency in resources capturing (Yin and Struik, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe non-application of K affected height growth. Plants that received potassium fertilization grew considerably more. This result reinforces the fundamental role of K in the plants biochemical and physiological processes (Taiz et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). This effect was also observed in root biomass production, since all plants were less efficient in producing this compartment when no potassium was applied. The availability of K influences fundamental physiological processes in plants, such as gas exchange, leaf water potential, growth, and nutrient uptake (Guo et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the present study, interesting interactions were observed between different species (\u003cem\u003eEucalyptus\u003c/em\u003e and \u003cem\u003eCorymbia\u003c/em\u003e) and K availability, revealing how responses vary depending on genotype. The CH showed greater water use efficiency, followed by CCV and H13, suggesting that these genotypes have adaptations to optimize water use, which can be advantageous in water-restricted environments (Almeida et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; C\u0026acirc;mara et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Ullah et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). These differences indicate that potassium and water use efficiency varies with genetic material, highlighting the importance of choosing the appropriate genotype for each management condition and environment (Bush et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSimilarly, there were no major changes in morphological and anatomical aspects due to fertilization conditions, but again, contrasting differences were observed between genotypes. Although \u003cem\u003eCorymbia\u003c/em\u003e has a larger leaf blade area compared to \u003cem\u003eEucalyptus\u003c/em\u003e clones, they presented lower LA and SLA. However, this is compensated by longer and wider leaves, resulting in a distinct canopy architecture that is possibly more efficient for intercepting diffuse light (Mattos et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The literature shows that \u003cem\u003eEucalyptus\u003c/em\u003e plants with higher SLA can optimize light absorption, which is an indispensable aspect for plant growth (Battie-Laclau et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAnother interesting finding of this study is that both CCV and CH had significantly fewer stomata per mm\u0026sup2; than clones I144 and H13. On the other hand, \u003cem\u003eCorymbia\u003c/em\u003e stomata are larger, both in polar and apolar diameter, which may indicate a possible strategy for stomatal regulation and gas exchange in these genotypes (Bertolino et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Plants with few large stomata tend to have lower photosynthetic rates compared to those with many small stomata, while higher stomatal density and size promote greater stomatal conductance and water loss (Franks et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Drake et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Yin et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These aspects reinforce the relevance of the integrated study of leaf morphology and anatomy as indicators of physiological adaptation and productive potential in forest species.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003eK availability modulates nutrition in Corymbia and Eucalyptus\u003c/h2\u003e \u003cp\u003eThe differences in response to K availability observed among the species evaluated in this study highlight the preponderance of this factor in association with the application or non-application of this nutrient. \u003cem\u003eEucalyptus\u003c/em\u003e genotypes may respond differently to potassium availability and supply due to genetic characteristics that influence the capacity for absorption and utilization of this nutrient (Gon\u0026ccedil;alves et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), which may be intensified when comparing seed species with clonal species, as performed in the present study. Some species may be more tolerant to potassium deficiency, showing better efficiency in the use of this nutrient, as well as better adaptation to stress conditions, while other species may be more sensitive, showing significant decreases in photosynthesis rate and growth under conditions of low K availability (Mostofa et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAlthough potassium fertilization conditions did not significantly influence most of the measured attributes, when analyzing the nutrient stock by plants, significant differences were identified between those treatments that received K fertilization and those treatments that did not. \u003cem\u003eCorymbia\u003c/em\u003e stood out for presenting high K and Ca stocks in plant compartments compared to \u003cem\u003eEucalyptus\u003c/em\u003e clones. The high K stock in leaves and roots may be related to its important role in osmotic regulation, stomatal control, and transport of compounds in the plant (Taiz et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Leaves, as plant components of intense transpiration and photosynthesis, require a high concentration of K to maintain osmotic balance and prevent excessive water loss (Wang et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). As leaves are areas of active growth and cell differentiation, there is a high demand for Ca to ensure the structural integrity of the membranes. Unlike K, Ca has low mobility within the plant after being absorbed by the roots; therefore, it tends to accumulate in the closest tissues, such as the roots themselves and young leaves in active growth (Zhang et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis study observed a significant variation in absorption and accumulation capacity of plants regarding K and Ca. The high K and Ca stocks in the leaves and stems+branches of \u003cem\u003eCorymbia\u003c/em\u003e can be explained by the greater efficiency of these species in absorbing these nutrients, reflecting the role of this nutrient in osmotic regulation and stomatal control, which are essential for maintaining osmotic balance, water stability, and compound transport (Arquero et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Battie-Laclau et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Additionally, the high concentration of K and Ca in the leaf tissues promoted higher stocks of these nutrients in this compartment of CCV and CH plants. In general, the stock of nutrients in the leaves was not affected by the absence or presence of K fertilization. Only the stocks of such nutrients were different between species. However, the same behavior was not observed in the roots, stems, and branches. The I144 and H13 were more efficient in the use of K and Ca. These clones require smaller amounts of nutrients to produce the same amount of biomass compared to less efficient species such as CCV and CH (Gazola et al., 2019).\u003c/p\u003e \u003cp\u003ePrincipal component analysis integrated physiological, morphological, and nutritional variables, revealing patterns of genotype response to K availability that were not evident in univariate analyses. The I144 and H13 benefited from potassium fertilization, with greater nutrient storage and root development, while \u003cem\u003eCorymbia\u003c/em\u003e showed a more conservative strategy, with greater water use efficiency. These results reinforce that different species adopt contrasting strategies to deal with limiting resources, highlighting the relevance of integrated responses in the selection of genetic materials in management and breeding programs (Cornut et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Gazola et al., 2019).\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe physiological assessments of Eucalyptus and Corymbia revealed that the response to potassium fertilization is highly dependent on the intrinsic characteristics of each genotype, independent of the genus, species or propagation method (ex. seed or cutting). On the other hand, clones of \u003cem\u003eE. urophyla\u003c/em\u003e x \u003cem\u003eE. grandis\u003c/em\u003e (e.g., I144 and H13) are more efficient in nutrient use when compared to \u003cem\u003eCorymbia\u003c/em\u003e species (e.g., \u003cem\u003eC. variegata\u003c/em\u003e and \u003cem\u003eC. henry\u003c/em\u003e). The I144 presented a high photosynthetic and gas exchange rate when compared to \u003cem\u003eCorymbia\u003c/em\u003e species, which explains its high productivity. By prioritizing the conversion of CO2 into biomass, I144 may have low water use efficiency when compared to \u003cem\u003eCorymbias\u003c/em\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was partially funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – under Finance Code 001. Additional financial support was provided by the Silviculture and Management Thematic Program at the Institute of Forest Research and Study (PTSM/IPEF).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the Coordination for the Improvement of Higher Education Personnel (CAPES/Brazil) (grant number Code 001). The authors also thank the Thematic Program on Forestry and Management of the Institute for Forest Research and Studies (PTSM/IPEF) for financial and technical support. We also thank the Department of Forest Sciences of the University of São Paulo, Luiz de Queiroz College of Agriculture (ESALQ-USP).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMaria Leidiane Reis Barreto: Methodology, Validation, Formal analysis, Research, Data curation, Writing - Original draft, Writing - Revision and editing, Visualization, Supervision, Project management. Cassio Rafael Costa dos Santos: Writing - Original draft, Writing - Revision and editing, Validation, Visualization. Adam da Cruz Rodrigues: Writing - Original Draft, Writing - Revision and Editing, Validation, Visualization. Felipe Tavares Lima: Writing - Original Draft, Writing - Revision and Editing, Validation, Visualization. Gleydson Vinicius dos Santos Silveira: Writing - Revision and Editing, Validation, Visualization. Huga Géssica Bento de Oliveira Sousa: Writing - Revision and Editing, Validation, Visualization. Antonio Leite Florentino: Writing - Original Draft, Writing - Revision and Editing, Validation, Visualization. José Leonardo de Moraes Gonçalves: Conceptualization, Methodology, Validation, Resources, Data Curation, Writing - Revision and Editing, Supervision, Project Management. Alexandre de Vicente Ferraz: Conceptualization, Methodology, Validation, Resources, Data Curation, Writing - Revision and Editing, Supervision, Project Management.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlmeida MNF, Vidaurre GB, Pezzopane JEM, Lousada JLPC, Silva MECM, C\u0026acirc;mara AP, Rocha SFG, Oliveira JCL, Campoe OC, Carneiro RL, Alvares CA, Tomazello Filho M, Figueiredo FM, Oliveira RF (2020) Heartwood variation of Eucalyptus urophylla is influenced by climatic conditions. 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Industrial Crops and Products 232:121226. https://doi.org/10.1016/j.indcrop.2025.121226\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"plant-and-soil","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"plso","sideBox":"Learn more about [Plant and Soil](https://www.springer.com/journal/11104)","snPcode":"11104","submissionUrl":"https://submission.nature.com/new-submission/11104/3","title":"Plant and Soil","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Fertilization, Water stress, Leaf morphology, Leaf anatomy, Photosynthesis","lastPublishedDoi":"10.21203/rs.3.rs-8846297/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8846297/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eAims\u003c/h2\u003e \u003cp\u003eEucalypt plantations in Brazil have expanded into regions with highly weathered soils and marked heat and water deficits, where potassium (K) availability becomes a major constraint due to its role in osmotic adjustment, stomatal regulation and water use efficiency. This study evaluated physiological responses to potassium fertilization of two Corymbia species (\u003cem\u003eCorymbia citriodora subsp\u003c/em\u003e. \u003cem\u003evariegata\u003c/em\u003e \u0026ndash; CCV and \u003cem\u003eCorymbia henryi\u003c/em\u003e \u0026ndash; CH) recently introduced into breeding programs, and two traditional Eucalyptus urophylla \u0026times; E. grandis cuttings (I144 and H13).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThe experiment followed a completely randomized 4 \u0026times; 2 factorial design and was conducted in pots for six months under greenhouse conditions. Leaf water potential (Ψf), gas exchange, biomass allocation, leaf anatomy and plant nutrition were evaluated.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eDuring the most stressful period, Ψf was 21% more negative under potassium omission (\u0026minus;\u0026thinsp;K). Gas exchange was not affected by fertilization but differed among genotypes. Clone I144 showed higher stomatal conductance and transpiration, resulting in 26% lower water use efficiency. Potassium omission reduced root biomass by 23%. Despite this, I144 accumulated 34% more K in total biomass than the other genotypes under \u0026minus;\u0026thinsp;K. Under potassium fertilization (+\u0026thinsp;K), genotypes exhibited 23% higher K use efficiency.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe physiological assessments of Eucalyptus and \u003cem\u003eCorymbia\u003c/em\u003e revealed that the response to potassium fertilization is highly dependent on the intrinsic characteristics of each genotype, independent of the genus, species or propagation method (ex. seed or cutting).\u003c/p\u003e","manuscriptTitle":"Does low potassium availability modulate the physiological responses of Corymbia seedlings and Eucalyptus cuttings?","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-24 17:14:07","doi":"10.21203/rs.3.rs-8846297/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-02-20T05:50:44+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-20T05:00:34+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-20T00:10:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"Plant and Soil","date":"2026-02-18T10:59:27+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"plant-and-soil","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"plso","sideBox":"Learn more about [Plant and Soil](https://www.springer.com/journal/11104)","snPcode":"11104","submissionUrl":"https://submission.nature.com/new-submission/11104/3","title":"Plant and Soil","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"52ef7ff6-d405-4a8a-9b2a-95985224bdcb","owner":[],"postedDate":"February 24th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-24T17:14:07+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-24 17:14:07","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8846297","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8846297","identity":"rs-8846297","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}