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• Carbon isotope composition (δ13C) variation among J. curcas genotypes is discrete. • Drought-induced changes in δ13C is remarkable in J. curcas. • δ13C may be used as a tool for screening water-use efficient genotypes in J. curcas. Jatropha curcas L. is a non-food crop quoted as a promising natural feedstock for biodiesel production in tropical and subtropical regions. Although an efficient mechanism of drought avoidance through stomatal control of transpiration has been demonstrated in this species, low carbon assimilation and growth rates preclude any advantage of such strategy under water limitation. Two greenhouse experiments were conducted with the objective of investigating varietal differences in water use as the trade-off between carbon isotope composition (δ13C) in different tissues and water use efficiency, in young plants of J. curcas. The first experiment was a survey with seven provenances of J. curcas under non-limiting water availability. There were no significant differences among provenances for leaf gas exchange rates, growth and whole-plant transpiration (T). However, significant effects of provenance and tissue (stem bark or leaf) in δ13C were demonstrated. The provenances CNPAE183 and CNPAE222 were selected for the second experiment, as variations in water use traits and δ13C between the two provenances were observed. Soil water deficit, imposed for 18 days, led to significant physiological, biochemical, and morphological changes. An early and sharp response to water deficit in CNPAE183 as compared to CNPAE222 was observed, as indicated by a 44% higher rate of decrease of T in the former. In addition, water deficit led to increase of δ13C, which was more pronounced in CNPAE222 (13% in young leaves) when compared to CNPAE183 (11% in young leaves). In both provenances, δ13C was less negative in young as compared to mature tissues. Significant and direct correlations between stem bark and leaf δ13C and leaf-level intrinsic water use efficiency were observed. Contrasting results, particularly on T and δ13C, suggest the existence of genetic diversity for water relations and metabolic traits linked to drought tolerance in J. curcas. Using stem bark or leaf δ13C measurements as the basis for large-scale screening of water-use efficient genotypes should be considered. [ABSTRACT FROM AUTHOR]

In subalpine fir wave forests, strips of dead and weakened trees occur perpendicular to the slope next to strips of healthy trees. To reveal the transpiration by weakened Abies veitchii trees exposed to increased atmospheric evaporative demand, we investigated the ecophysiological traits closely related to the growth and transpiration, comparing them with those of the healthy trees and saplings in the fir wave of Mt. Shimagare in central Japan. The transpiration rate (E) was investigated using sap flux sensors to measure heat pulse velocity and compared with the surrogate for the needle water demand, which was computed using a multilayered gas and energy transfer model (modeled E, Emod). Weakened trees exhibited smaller diameter growth and narrower sapwood than healthy trees, as well as lower heat pulse velocity compared with healthy saplings. However, needle‐level traits did not differ significantly between weakened and healthy trees. Needle water potential at midday was as negative as the needle turgor loss point, and the measured heat pulse velocity increased linearly with Emod but leveled off above a certain Emod value in weakened trees and healthy saplings, suggesting that trees restricted E to balance the needle water budget. Heat pulse velocity of weakened trees leveled off at Emod lower than that of healthy saplings, probably due to lower capacity for water supply to the needles. Restriction of E would occur less frequently but be necessary for both weakened and healthy A. veitchii on Mt. Shimagare to avoid hydraulic failure, sacrificing photosynthetic carbon assimilation. [ABSTRACT FROM AUTHOR]

Tissue culture is used to multiply Al-Taif rose (Rosa damascena f. trigintipetala (Diek) R. Keller) plants in order to meet the demands of the fragrance, cosmetic, and floriculture industries. The use of arbuscular mycorrhizal fungus (AMF) could potentially improve plant growth and acclimatization performance to ex vitro conditions. Thus, in the current study, we investigated how AMF Rhizophagus fasciculatus influences the growth, establishment, and physiological performance of micropropagated Al-Taif rose plants during the acclimatization stage. The growth and physiological parameters of the AMF-treated plants were evaluated after a 12 week growth period in the growth chambers. The plants treated with AMF exhibited greater height (25.53 cm) and biomass growth values for both shoot fresh weight (0.93 g/plant) and dry weight (0.030 g/plant), more leaves (11.3/plant), more leaf area (66.15 cm2), longer main roots (15.05 cm/plant), total root length (172.16 cm/plant), total root area (64.36 cm2/plant), and biomass from both fresh weight (383 mg/plant) and dry weight (80.00 mg/plant) of the plants. The plants treated with AMF also exhibited increased rates of net CO2 assimilation, stomatal conductance, and transpiration compared to the control plants. The proline content in the leaves and roots was significantly lower in the AMF-treated plants than untreated plants. The Fv/Fm ratio, which serves as an indicator of the intrinsic or maximal efficacy of Photosystem II (PSII) demonstrated a notable decline in the untreated Al-Taif rose plants. These results elucidate the advantageous impact of AMF colonization on micropropagated Al-Taif rose plants, thereby enhancing their resilience against adverse ex vitro conditions. [ABSTRACT FROM AUTHOR]

Environmental contamination by iron mine tailings occurs worldwide; however, the growth of cultivated tree species in different stages of ecological succession in such areas is not well understood. Over 80 days, with data collected every 20 days, the morphophysiology of three tree species in different stages of ecological succession (Schinus terebinthifolius, pioneer; Cedrela fissilis, secondary; and Cariniana estrellensis, climax) was investigated in a growth room. These were subjected to iron mine tailings from the Fundão Dam (Mariana-MG, Brazil), with the addition of either soil or vermicompost (2%) as an amendment. S. terebinthifolius and C. fissilis had higher quantities of dry matter, exhibited more changes in shoot and root morphology, as well as less variations in chlorophyll a fluorescence, indicating tolerance to the mine tailings. However, C. estrellensis was highly susceptible to these tailings. The pioneer species were more tolerant to mine tailings, suggesting their potential use as an excellent tool for the recovery of contaminated areas. The secondary species were also tolerant to mine tailings, although to a lesser extent. The climax species were found to be more sensitive to the tailings, but field establishment can differ when succession is already in place. The vermicompost showed great potential as an amendment, thereby reducing the bioavailability of Fe and Mn and favoring the growth of S. terebinthifolius and C. fissilis. [ABSTRACT FROM AUTHOR]

The presence of weeds and changes in temperature and precipitation due to global climate change can negatively affect the growth, development, and adaptation of poplars to new places. Experiments were conducted at the Experimental Estate of the Institute of Lowland Forestry and Environment to test glyphosate's efficacy and phytotoxicity and to assess the impact of glyphosate on physiological parameters in different stages of poplar plantations. A test with glyphosate was set up by a random block system with four replications at three localities, each characterized by different physical soil properties. Glyphosate efficacy was evaluated after 15 and 30 days, while phytotoxicity was evaluated according to the EWRC scale. Net photosynthesis (A), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration (Ci) were measured, and water use efficiency (WUE) was computed. Annual and perennial broadleaf weeds, grasses, and woody shrubs and bushes were identified. The dominant weed species across all poplar plantations were Solidago gigantea L., Solidago speciosa L., and Poa pratensis L. Glyphosate was highly effective against the major weed species, with the total efficacy ranging from 94.29 to 97.67%. The results showed significant differences in all observed gas exchange parameters, except for transpiration rate (E), between the different-aged poplar plantations. The younger poplars showed lower gas exchange rates in the treatment under the environmental conditions of the studied sites. Weed suppression resulted in altered microhabitats for poplar development at various ages, causing variation in the physiological parameters compared to the control. [ABSTRACT FROM AUTHOR]

Polygonum minus Huds. has massive potential to be commercialized following many current discoveries of its medicinal properties. We investigated the growth and physiology changes of P. minus under different shading and treatment durations. The effects of four shading levels: 0% (T1), 30% (T2), 50% (T3) and 70% (T4) and two treatment durations of 10 weeks and 20 weeks were studied. Significant effects of shading levels and treatment durations were observed on the transpiration rate (E), leaf resistance, pigment content in leaves (Chl a, Chl b and Car), carbohydrate, ascorbic acid, total anthocyanin, phenolic and flavonoid contents. Enzyme activity of superoxide dismutase and ascorbate peroxidase were also significantly affected by shading levels and treatment durations. The highest antioxidant activities were recorded under T4 of both treatment durations along with the high content of Chl a, Chl b and Car. The leaf, stem and root extracts of P. minus were also subjected to HPLC analysis for quantification of selected flavonoid compounds. It was observed that longer treatment duration of 20 weeks reduced the amount of flavonoid. [ABSTRACT FROM AUTHOR]

Acanthosyris paulo-alvinii G.M. Barroso (cacao killer) is a woody and hemiparasitic species, endemic to Southern Bahia, Brazil, presents chemical properties of unknown nature that promote the death of Theobroma cacao L. plants as a result of the hemiparasitism of its roots by haustoria. The objective of the present study was to identify possible anatomical, physiological, biochemical, and molecular changes that could elucidate the death of the host when exposed to hemiparasitism. The two species were grown alone and together in plastic water boxes of 350 L containing soil. At 30 days after application of treatments (DAAT), the host began to show symptoms characteristic of hemiparasitism, such as chlorosis and leaf necrotic spots. Structural differences were observed in leaf mesophyll cells, root tissue, and the haustorium of the hemiparasite, both in the presence and absence of the T. cacao host. The hemiparasitism did not affect host leaf gas exchange but reduced the production of flavonoids in the leaves. Furthermore, 27% of the proteins were associated with energy metabolism and carbohydrate metabolism, indicating a probable response to stress and, consequently, positive feedback for its benefit since it tries to use metabolism for their nutrition, which may further increase their demand. Enzymatic and non-enzymatic antioxidative metabolism in the T. cacao hemiparasitized by cacao killer were not sufficient to eliminate the reactive oxygen species excess. Oxidative stress associated with greater energy consumption in the T. cacao hemiparasitized by cacao killer interfered in cell homeostasis, resulting in lipid peroxidation of cell membranes, followed by programmed cell death and, consequently, the death of the host plant at 40 DAAT. [ABSTRACT FROM AUTHOR]

Summary: Analyses of leaf gas exchange rely on an Ohmic analogy that arrays single stomatal, internal air space, and mesophyll conductances in series. Such models underlie inferences of mesophyll conductance and the relative humidity of leaf airspaces, reported to fall as low as 80%. An unresolved question is whether such series models are biased with respect to real leaves, whose internal air spaces are chambered at various scales by vasculature.To test whether unsaturation could emerge from modeling artifacts, we compared series model estimates with true parameter values for a chambered leaf with varying distributions and magnitudes of leaf surface conductance ('patchiness').Distributions of surface conductance can create large biases in gas exchange calculations. Both apparent unsaturation and internal CO2 gradient inversion can be produced by the evolution of broader distributions of stomatal apertures consistent with a decrease in surface conductance, as might occur under increasing vapor pressure deficit.In gas exchange experiments, the behaviors of derived quantities defined by simple series models are highly sensitive to the true partitioning of flux and stomatal apertures across leaf surfaces. New methods are needed to disentangle model artifacts from real biological responses. [ABSTRACT FROM AUTHOR]

Summary: The 'assimilates inhibition hypothesis' posits that accumulation of nonstructural carbohydrates (NSCs) in leaves reduces leaf net photosynthetic rate, thus internally regulating photosynthesis. Experimental work provides equivocal support mostly under controlled conditions without identifying a particular NSC as involved in the regulation.We combined 3‐yr in situ leaf gas exchange observations (natural dynamics) in the upper crown of mature Betula pendula simultaneously with measurements of concentrations of sucrose, hexoses (glucose and fructose), and starch, and similar measurements during several one‐day shoot girdling (perturbation dynamics). Leaf water potential and water and nitrogen content were measured to account for their possible contribution to photosynthesis regulation.Leaf photosynthetic capacity (A/Ci) was temporally negatively correlated with NSC accumulation under both natural and perturbation states. For developed leaves, leaf hexose concentration explained A/Ci variation better than environmental variables (temperature history and daylength); the opposite was observed for developing leaves.The weaker correlations between NSCs and A/Ci in developing leaves may reflect their strong internal sink strength for carbohydrates. By contrast, the strong decline in photosynthetic capacity with NSCs accumulation in mature leaves, observed most clearly with hexose, and even more tightly with its constituents, provides support for the role of assimilates in regulating photosynthesis under natural conditions. [ABSTRACT FROM AUTHOR]

Key Message: Atlantic Forest tree seedlings with contrasting ecological characteristics present specific growth and physiological responses to nitrogen and phosphorus addition in the soil. Nitrogen (N) and phosphorus (P) are commonly the most limiting nutrients for plant growth in tropical forests. Many of these ecosystems are exposed to increasing rates of anthropogenic nutrient deposition. This study aims to assess how five Atlantic Forest tree species respond to N and P addition to the soil. Five species with different levels of shade tolerance were subjected to nine weekly soil applications of (NH4)2SO4 (84 kg N ha−1 treatment N), NaH2PO4 (45 kg P ha−1 treatment P), both nutrients (treatment N + P), or water. Soil, foliar nutrient concentrations, and biometric and gas exchange analyses were performed. No changes in the soil pH or total N and P availability were observed in the soil after N addition, whereas P accumulated in the soil and leaves of three species after P addition. The pioneer species H. popayanensis presented increased total biomass with P and N+P treatments, while C. floribundus increased with P treatment and C. pachystachya increased with N + P treatment. N and P treatments reduced the photosynthesis of C. pachystachya and the stomatal conductance of C. pachystachya and C. floribundus. The growth rate and total biomass of C. estrellensis reduced with N and P treatments and increased with N+P treatment. Aspidosperma polyneuron presented reduced photosynthesis with N treatment, but increased total biomass with all treatments, especially N + P. The diversity of growth and physiological responses to N and P addition suggests that each species has specific nutrient requirements and uses strategies related to the niche occupied by each one. [ABSTRACT FROM AUTHOR]

Zinc enrichment of edible food products, through the soil and/or foliar application of fertilizers, is a strategy that can increase the contents of some nutrients, namely Zn. In this context, a workflow for agronomic enrichment with zinc was carried out on irrigated Vitis vinifera cv. Syrah, aiming to evaluate the mobilization of photoassimilates to the winegrapes and the consequences of this for winemaking. During three productive cycles, foliar applications were performed with ZnSO4 or ZnO, at concentrations ranging between 150 and 1350 g.ha−1. The normal vegetation index as well as some photosynthetic parameters indicated that the threshold of Zn toxicity was not reached; it is even worth noting that with ZnSO4, a significant increase in several cases was observed in net photosynthesis (Pn). At harvest, Zn biofortification reached a 1.2 to 2.3-fold increase with ZnSO4 and ZnO, respectively (being significant relative to the control, in two consecutive years, with ZnO at a concentration of 1350 g.ha−1). Total soluble sugars revealed higher values with grapes submitted to ZnSO4 and ZnO foliar applications, which can be advantageous for winemaking. It was concluded that foliar spraying was efficient with ZnO and ZnSO4, showing potential benefits for wine quality without evidencing negative impacts. [ABSTRACT FROM AUTHOR]

IntroductionActinidia is highly susceptible to water stress, both excess and shortage, and is therefore a model fruit crop for irrigation management, requiring precise water application. The present study was carried out in a mature kiwifruit orchard in southern Italy to investigate the physiology of a yellow-fleshed kiwifruit cultivar under non-limiting soil water conditions and in response to a progressive decrease in soil water content in a Mediterranean environment, with the aim of defining soil moisture thresholds to guide irrigation management.MethodsThe progressive lowering in soil moisture was monitored using multi-profile probes, taking into account a 60 cm layer. Plant water status and physiological parameters were measured throughout the experiment and were significantly correlated with soil water status, suggesting that the level of soil water deficit affects plant physiological performance.ResultsReference minimum values of stem water potential reached during the day under non-limiting soil water conditions ranged from -0.4 to -0.7 MPa, with a value of -0.8 MPa identifying the threshold below which stomatal conductance began to decrease significantly. Soil moisture thresholds were defined according to the spatio-temporal dynamics of available water (AW) reduction, which decreased by approx. 10% and 1% before the onset of water stress and 16% and 2% at the onset of water stress, considered in the 0-30 cm and 30-60 cm soil layers, respectively, compared to the AW content of the whole soil profile.DiscussionResults confirmed that root uptake was mainly concentrated in the first 30 cm of soil depth, which should be properly managed by irrigation, as reduced soil water availability could easily lead to plant water stress. An integrated approach, combining plant measurements and soil water content monitoring, together with an assessment of root water uptake dynamics, is essential to identify soil water thresholds and develop precision irrigation, especially for high water-demanding crops and environments.

Conventional breeding relies on genetic variability in crop germplasm and wild species. This study evaluated 137 barley Recombinant Chromosome Substitution Lines (RCSLs), originating from crossing a drought and salinity-tolerant wild Hordeum spontaneum with the high-quality malting H. vulgare cv. Harrington. The objectives of this work were to i) improve understanding of the genetic diversity and introgression levels in RCSLs using a comprehensive set of high-density single nucleotide polymorphism (SNP) markers; ii) investigate the phenotypic variability of physiological, agronomic, and malting quality traits in RCSLs under rainfed and fully irrigated conditions; iii) unravel the relationship between these traits and the resilience of crops in drought-prone regions; and iv) identify specific SNPs associated with both drought tolerance indices and malting quality traits. Variability in physiological, agronomic, and malting quality traits was examined under rainfed and irrigated conditions, aiming to identify specific SNPs associated with both drought tolerance indices and malting quality traits. Additionally, a subset of three recombinant lines and the parent cv. Harrington was tested in growth chambers under well-watered and water-limited conditions. Agronomic traits were influenced by genotype-by-environment interaction, with notable drought tolerance lines. The grain yield was significantly correlated with yield-related traits and carbon isotope discrimination in grains. Drought stress impacted agronomic and physiological traits, with a strong reduction in leaf gas exchange and chlorophyll and protein content. The H. spontaneum genome introgression into H. vulgare cv. Harrington varied across 137 RCSLs, averaging 13.0 %. Associations between traits and genetic markers were found, particularly for the stress tolerance index in chromosome 1H and for grain quality traits (alfa-amylase, wort color, and protein) in chromosomes 1H, 4H, and 5H. These findings uncovered valuable barley RCSLs that demonstrate drought tolerance, offering promising prospects for breeding programs targeted at improving stress resilience.

Trichomes are common in plants from dry environments, and despite their recognized role in protection and defense, little is known about their role as absorptive structures and in other aspects of leaf ecophysiology. We combine anatomical and ecophysiological data to evaluate how trichomes affect leaf gas exchange and water balance during drought. We studied two congeneric species with pubescent leaves which co‐occur in Brazilian Caatinga: Croton blanchetianus (dense trichomes) and Croton adenocalyx (sparse trichomes). We found a novel foliar water uptake (FWU) pathway in C. blanchetianus composed of stellate trichomes and underlying epidermal cells and sclereids that interconnect the trichomes from both leaf surfaces. The water absorbed by these trichomes is redistributed laterally by pectin protuberances on mesophyll cell walls. This mechanism enables C. blanchetianus leaves to absorb water more efficiently than C. adenocalyx. Consequently, the exposure of C. blanchetianus to dew during drought improved its leaf gas exchange and water status more than C. adenocalyx. C. blanchetianus trichomes also increase their leaf capacity to reflect light and maintain lower temperatures during drought. Our results emphasize the multiple roles that trichomes might have on plant functioning and the importance of FWU for the ecophysiology of Caatinga plants during drought. Summary statement: We describe a novel pathway of foliar water absorption that involves stellate trichomes, sclereids and pectin protuberances that redistribute water inside the leaf. The absorption of dew water through this pathway benefits the ecophysiological performance of Caatinga plants during drought. [ABSTRACT FROM AUTHOR]

Leaf gas exchange measurements are an important tool for inferring a plant's photosynthetic biochemistry. In most cases, the responses of photosynthetic CO2 assimilation to variable intercellular CO2 concentrations (A/Ci response curves) are used to model the maximum (potential) rate of carboxylation by ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco, Vcmax) and the rate of photosynthetic electron transport at a given incident photosynthetically active radiation flux density (PAR; JPAR). The standard Farquhar‐von Caemmerer‐Berry model is often used with default parameters of Rubisco kinetic values and mesophyll conductance to CO2 (gm) derived from tobacco that may be inapplicable across species. To study the significance of using such parameters for other species, here we measured the temperature responses of key in vitro Rubisco catalytic properties and gm in cotton (Gossypium hirsutum cv. Sicot 71) and derived Vcmax and J2000 (JPAR at 2000 µmol m−2 s−1 PAR) from cotton A/Ci curves incrementally measured at 15°C–40°C using cotton and other species‐specific sets of input parameters with our new automated fitting R package 'OptiFitACi'. Notably, parameterisation by a set of tobacco parameters produced unrealistic J2000:Vcmax ratio of <1 at 25°C, two‐ to three‐fold higher estimates of Vcmax above 15°C, up to 2.3‐fold higher estimates of J2000 and more variable estimates of Vcmax and J2000, for our cotton data compared to model parameterisation with cotton‐derived values. We determined that errors arise when using a gm,25 of 2.3 mol m−2 s−1 MPa−1 or less and Rubisco CO2‐affinities in 21% O2 (KC21%O2) at 25°C outside the range of 46–63 Pa to model A/Ci responses in cotton. We show how the A/Ci modelling capabilities of 'OptiFitACi' serves as a robust, user‐friendly, and flexible extension of 'plantecophys' by providing simplified temperature‐sensitivity and species‐specificity parameterisation capabilities to reduce variability when modelling Vcmax and J2000. Summary statement: This manuscript demonstrates the importance of species‐specific parameterisation of A/Ci response models for accurate modelling of key photosynthetic parameters in cotton (Gossypium hirsutum). [ABSTRACT FROM AUTHOR]

Virginia spiraea (Spiraea virginiana Britton, Rosaceae) is a putative shade-intolerant, disturbance-adapted, riparian shrub species native to the southern Appalachian Mountains. This species was listed as threatened in 1990, and a federal recovery plan was developed in 1992. Current reassessment of the recovery plan includes proposals for propagation and out-planting to supplement and restore wild populations. Genotypes with greater shade acclimation would likely have higher survival in natural populations, would require less frequent shade-reduction management, and could be integrated into populations that need restoration. In summer 2022, we examined steady-state (maximum light-saturated photosynthetic, dark respiration rates, quantum yield, light compensation point) and dynamic (photosynthetic induction and loss patterns) photosynthetic characteristics, pigment concentrations, and specific leaf mass of cloned propagules from five elements of occurrence along the South Fork of the New River in Ashe County, North Carolina, along an artificial light gradient (100%, 75%, 50%, and 20% of full sun) in a common garden. Data were compared among light treatments using ANOVA or non-parametric tests. Light treatment had significant effects on maximum photosynthesis, dark respiration, specific leaf mass, and light compensation, but not quantum yield, pigment concentrations, or induction and loss times. Some parameters had plasticity similar to that seen in other woody shrubs, while others were less plastic. A surprising finding was that plants performed better under 75% full sunlight suggesting an ability to tolerate, and maybe even a preference for, partial shade in this species. Future studies should examine photosynthetic characteristics of individuals from genetically contrasting source populations. [ABSTRACT FROM AUTHOR]

Climate change, characterized by rising atmospheric CO2 levels and temperatures, poses significant challenges to global crop production. Sweet sorghum, a prominent C4 cereal extensively grown in arid areas, emerges as a promising candidate for sustainable bioenergy production. This study investigated the responses of photosynthesis and leaf-scale water use efficiency (WUE) to varying light intensity (I) in sweet sorghum under different temperature and CO2 conditions. Comparative analyses were conducted between the An-I, gs-I, Tr-I, WUEi-I, and WUEinst-I models proposed by Ye et al. and the widely utilized the non-rectangular hyperbolic (NRH) model for fitting light response curves. The Ye's models effectively replicated the light response curves of sweet sorghum, accurately capturing the diminishing intrinsic WUE (WUEi) and instantaneous WUE (WUEinst) trends with increasing I. The fitted maximum values of An, gs, Tr, WUEi, and WUEinst and their saturation light intensities closely matched observations, unlike the NRH model. Despite the NRH model demonstrating high R2 values for An-I, gs-I, and Tr-I modelling, it returned the maximum values significantly deviating from observed values and failed to generate saturation light intensities. It also inadequately represented WUE responses to I, overestimating WUE. Across different leaf temperatures, An, gs, and Tr of sweet sorghum displayed comparable light response patterns. Elevated temperatures increased maximum An, gs, and Tr but consistently declined maximum WUEi and WUEinst. However, WUEinst declined more sharply due to the disproportionate transpiration increase over carbon assimilation. Critically, sweet sorghum An saturated at current atmospheric CO2 levels, with no significant gains under 550 mmol mol-1. Instead, stomatal closure enhanced WUE under elevated CO2 by coordinated gs and Tr reductions rather than improved carbon assimilation. Nonetheless, this response diminished under simultaneously high temperature, suggesting intricate interplay between CO2 and temperature in modulating plant responses. These findings provide valuable insights into photosynthetic dynamics of sweet sorghum, aiding predictions of yield and optimization of cultivation practices. Moreover, our methodology serves as a valuable reference for evaluating leaf photosynthesis and WUE dynamics in diverse plant species. [ABSTRACT FROM AUTHOR]

Gladiolus is a well-known bulbous plant producing impressive cut spikes. Hydrogen sulfide (H2S) and nitric oxide (NO) are vital signaling molecules required for the proper functioning of plant metabolism. Preharvest applications of these molecules to crops have gained attention in recent years due to their positive role in tackling abiotic stresses, although, their role in geophytes is comparatively less studied. We assessed the effects of preharvest H2S and NO treatments on development, flowering, harvest and postharvest performance of gladiolus inflorescences. NO and H2S + NO treatments increased preharvest performance of plants associated with corm production, inflorescences length and harvest time. Individual and combined treatments improved postharvest vase life (VL) up to 3.4 days. Total soluble proteins (TSP) were increased in response to H2S, NO and H2S + NO treatments by 39%, 43%, and 55%, respectively compared to the controls. Soluble sugars (SS) were increased after NO and H2S + NO treatments by up to 25% and 42%, respectively. Postharvest catalase (CAT) activity was higher by 65%, 68%, and 76% after H2S, NO and H2S + NO treatments, respectively. Malondialdehyde (MDA) was decreased by all preharvest treatments by up to 88%, although, only the combined H2S + NO treatment reduced H2O2 and superoxide dismutase (SOD) activity. The results confirm that preharvest treatments with H2S, NO and H2S + NO may positively affect growth, floral traits and postharvest performance of cut gladiolus inflorescences. [ABSTRACT FROM AUTHOR]

Summary: The strong covariation of temperature and vapour pressure deficit (VPD) in nature limits our understanding of the direct effects of temperature on leaf gas exchange. Stable isotopes in CO2 and H2O vapour provide mechanistic insight into physiological and biochemical processes during leaf gas exchange.We conducted combined leaf gas exchange and online isotope discrimination measurements on four common European tree species across a leaf temperature range of 5–40°C, while maintaining a constant leaf‐to‐air VPD (0.8 kPa) without soil water limitation.Above the optimum temperature for photosynthesis (30°C) under the controlled environmental conditions, stomatal conductance (gs) and net photosynthesis rate (An) decoupled across all tested species, with gs increasing but An decreasing. During this decoupling, mesophyll conductance (cell wall, plasma membrane and chloroplast membrane conductance) consistently and significantly decreased among species; however, this reduction did not lead to reductions in CO2 concentration at the chloroplast surface and stroma.We question the conventional understanding that diffusional limitations of CO2 contribute to the reduction in photosynthesis at high temperatures. We suggest that stomata and mesophyll membranes could work strategically to facilitate transpiration cooling and CO2 supply, thus alleviating heat stress on leaf photosynthetic function, albeit at the cost of reduced water‐use efficiency. [ABSTRACT FROM AUTHOR]

Leaf gas exchange plays a critical role in determining crop final yield, and there is a threshold response of leaf gas exchange to water stress. It is of great significance to quantify crop water stress severity by using the response characteristics of leaf gas exchange to drought. However, it is currently unclear whether leaf gas exchange serve as a reliable indicator for predicting crop final yield in response to drought, which affects the accuracy of monitoring agricultural drought using physiological indicators during the crop growing season. This study determined the response threshold of leaf gas exchange to drought for spring wheat through a serials of soil dry-down experiments and used the threshold characteristics to construct and parameterize a spring wheat growth model. Spring wheat were designed to be irrigated with five treatments (with supplementary irrigation at 230 mm, 165 mm, 115 mm, 50 mm and 0 mm). Crop model were used to simulate and analyze the threshold response characteristics of grain yield to drought and compare them to the thresholds of leaf gas exchange indices for spring wheat. The results showed that the response threshold of stomatal conductance of spring wheat to fraction of transpirable soil water was 0.5, which was greater than that of transpiration rate and net photosynthetic rate, 0.4. The parameterized spring wheat growth model with the response threshold of net photosynthetic rate to fraction of transpirable soil water accurately simulated the aboveground biomass and final yield of spring wheat. The response threshold of spring wheat final yield to fraction of transpirable soil water was significantly smaller than that of leaf gas exchange parameters to fraction of transpirable soil water (0.18 versus 0.4). This indicates that there are certain problems in using physiological indicator such as leaf gas exchange indices during crop growing season to determine the agricultural drought severity and reflect the reduction of final crop yields due to drought. [ABSTRACT FROM AUTHOR]

The mesic-origin species Robinia pseudoacacia L. (black locust) is widely planted in the semiarid and sub-humid areas of the Loess Plateau for the reforestation of vegetation-degraded land. Under the scenario of changing precipitation patterns, exploring the response of photosynthesis to drought allows us to assess the risk to sustainable development of these plantations. In this study, paired plots were established including the control and a treatment of 30% exclusion of throughfall (since 2018). The photosynthetic characteristics were investigated using a portable photosynthesis system for four periods in the full-leaf growing season of 2021–2022, the fourth and fifth years, on both treated and controlled sampling trees. Leaf gas exchange parameters derived from diurnal changing patterns, light response curves, and CO2 response curves showed significant differences except for period II (9–11 September 2021) between the two plots. The photosynthetic midday depression was observed in 2022 in the treated plot. Meanwhile, the decline of net photosynthetic rate in the treated plot was converted from stomatal limitation to non-stomatal limitation. Furthermore, we observed that black locust adapted to long-term water deficiency by reducing stomatal conductance, increasing water use efficiency and intrinsic water use efficiency. The results demonstrate that reduction in precipitation would cause photosynthesis decrease, weaken the response sensitivity to light and CO2, and potentially impair photosynthetic resilience of the plantations. They also provide insights into the changes in photosynthetic functions under global climate change and a reference for management of plantations. [ABSTRACT FROM AUTHOR]

Due to substantial topographic variations in the Himalaya, incident solar radiation in the forest canopy is highly unequal. This results in significant environmental differences at finer scales and may lead to considerable differences in photosynthetic productivity in montane forests. Therefore, local-scale ecophysiological investigations, may be more effective and instructive than landscape-level inventories and models. We investigated leaf ecophysiological differences and related adaptations between two Quercus semecarpifolia forests in aspect-mediated, significantly varying light regimes in the same mountain catchment. Seasonal and diurnal rates of photosynthesis (A) were significantly higher in south aspect (S) than the north (N). Although temperature was a key contributor to seasonal fluctuations in photosynthetic physiology, photoperiod significantly determined intraspecific variations in seasonal and diurnal plasticity of leaf ecophysiological traits between the two topography-mediated light environments. The regression model for A as a function of stomatal conductivity (gsw) explained the critical role of gsw in triggering photosynthetic plasticity as an adaptive function against varying environmental stresses due to seasonal solar differences. We also examined, modifications in chlorophyll content between the two light regimes across seasons to determine the chlorophyll adaptation strategy. The N aspect had higher leaf chl a, b, and chl a + b and a lower chl-allocation ratio (a/b) than S, which helped to optimize the required light reception in the photoreaction centers for improved photosynthetic performance. The leaf light response curves for A and gsw were observed against varying incident photosynthetic photon flux densities (0–2000 mol.m2 s−1 PPFD) for both aspects. We found that the same species developed significantly distinct light response strategies and photosynthetic capacities in S than in N for the given magnitudes of PPFD. Such acquired ecophysiological adaptations owing to varying light environments may provide significant clues for understanding the impact of future climate change on Himalayan tree species. [ABSTRACT FROM AUTHOR]

Abstract Background Many coastal areas of the world will be impacted by seawater intrusion inland exposing crops to increasing levels of soil salinity. Studies of salinity stress in horticultural crops, including papaya, invariably use NaCl as the salt source, which may not be indicative of seawater. Methods This study compared plant growth, physiological, and nutritional responses, including leaf gas exchange, maximal potential quantum efficiency of photosystem II (the ratio of variable to maximum chlorophyll fluorescence; Fv/Fm), the leaf chlorophyll index (LCI), electrolyte leakage (EL), leaf relative water content (RWC), leaf water potential (Ψw), leaf osmotic potential (Ψo), leaf and root N, P, K, Ca, Mg, Na and Cl contents, and growth of potted ‘Red Lady’ papaya plants, in a calcined clay substrate, irrigated with NaCl or artificial seawater (Instant Ocean®) at six soil electrical conductivity (EC) levels (0, 1, 2, 3, 4 or 6 dS m−1). Results There were slight significant reductions in Ψw, Ψo, net CO2 assimilation (A), stomatal conductance (g s ), and transpiration (Tr) with increasing EC regardless of the salt source. Leaf Ca, Mg, Na and Cl contents and root Mg, Na, and Cl increased significantly with increasing EC levels. For both salt sources, there was an indication of osmotic adjustment and tolerance of papaya up to an EC level of 6 dS m−1. A significant difference between the response to NaCl and artificial seawater was observed for plant height, leaf Mg and Cl contents, and root Mg and Na contents. Conclusion The use artificial seawater may be a better source than NaCl for studying papaya responses to increasing soil salinity.

Tissue culture is used to multiply Al-Taif rose (Rosa damascena f. trigintipetala (Diek) R. Keller) plants in order to meet the demands of the fragrance, cosmetic, and floriculture industries. The use of arbuscular mycorrhizal fungus (AMF) could potentially improve plant growth and acclimatization performance to ex vitro conditions. Thus, in the current study, we investigated how AMF Rhizophagus fasciculatus influences the growth, establishment, and physiological performance of micropropagated Al-Taif rose plants during the acclimatization stage. The growth and physiological parameters of the AMF-treated plants were evaluated after a 12 week growth period in the growth chambers. The plants treated with AMF exhibited greater height (25.53 cm) and biomass growth values for both shoot fresh weight (0.93 g/plant) and dry weight (0.030 g/plant), more leaves (11.3/plant), more leaf area (66.15 cm2), longer main roots (15.05 cm/plant), total root length (172.16 cm/plant), total root area (64.36 cm2/plant), and biomass from both fresh weight (383 mg/plant) and dry weight (80.00 mg/plant) of the plants. The plants treated with AMF also exhibited increased rates of net CO2 assimilation, stomatal conductance, and transpiration compared to the control plants. The proline content in the leaves and roots was significantly lower in the AMF-treated plants than untreated plants. The Fv/Fm ratio, which serves as an indicator of the intrinsic or maximal efficacy of Photosystem II (PSII) demonstrated a notable decline in the untreated Al-Taif rose plants. These results elucidate the advantageous impact of AMF colonization on micropropagated Al-Taif rose plants, thereby enhancing their resilience against adverse ex vitro conditions.

The presence of weeds and changes in temperature and precipitation due to global climate change can negatively affect the growth, development, and adaptation of poplars to new places. Experiments were conducted at the Experimental Estate of the Institute of Lowland Forestry and Environment to test glyphosate’s efficacy and phytotoxicity and to assess the impact of glyphosate on physiological parameters in different stages of poplar plantations. A test with glyphosate was set up by a random block system with four replications at three localities, each characterized by different physical soil properties. Glyphosate efficacy was evaluated after 15 and 30 days, while phytotoxicity was evaluated according to the EWRC scale. Net photosynthesis (A), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration (Ci) were measured, and water use efficiency (WUE) was computed. Annual and perennial broadleaf weeds, grasses, and woody shrubs and bushes were identified. The dominant weed species across all poplar plantations were Solidago gigantea L., Solidago speciosa L., and Poa pratensis L. Glyphosate was highly effective against the major weed species, with the total efficacy ranging from 94.29 to 97.67%. The results showed significant differences in all observed gas exchange parameters, except for transpiration rate (E), between the different-aged poplar plantations. The younger poplars showed lower gas exchange rates in the treatment under the environmental conditions of the studied sites. Weed suppression resulted in altered microhabitats for poplar development at various ages, causing variation in the physiological parameters compared to the control.

Many recent studies have highlighted the importance of plant growthpromoting (rhizo)bacteria (PGPR) in supporting plant's development, particularly under biotic and abiotic stress. Most focus on the plant growthpromoting traits of selected strains and the latter's effect on plant biomass, root architecture, leaf area, and specificmetabolite accumulation. Regarding energy balance, plant growth is the outcome of an input (photosynthesis) and several outputs (i.e., respiration, exudation, shedding, and herbivory), frequently neglected in classical studies on PGPR-plant interaction. Here, we discuss the primary evidence underlying the modifications triggered by PGPR and their metabolites on the plant ecophysiology. We propose to detect PGPR-induced variations in the photosynthetic activity using leaf gas exchange and recommend setting up the correct timing for monitoring plant responses according to the specific objectives of the experiment. This research identifies the challenges and tries to provide future directions to scientists working on PGPR-plant interactions to exploit the potential of microorganisms' application in improving plant value. [ABSTRACT FROM AUTHOR]

The yield traits and physiological responses of three wheat genotypes were studied when subjected to heat and combined heat and drought stress at anthesis under either aCO2 (400 ppm) or eCO2 (800 ppm) in a greenhouse. The heat treatment was 7‐days at day/night 35/28°C, and the combined heat and drought was withholding irrigation from the heat‐stressed plants until the photosynthetic rate reached <5 μmol m−2 s−1. The LM62 genotype had higher photosynthetic rate compared with LM19, though no significant difference in grain yield was found. eCO2 increased photosynthesis at 35°C and significantly lowered the electron transport rate at high intercellular CO2 concentrations. Maximum velocity of Rubisco carboxylation (Vcmax) and the maximum velocity of RuBP regeneration in leaves (Jmax) increased in 35°C compared with 25°C, though when normalized to 25°C both Vcmax and Jmax decreased in the heat‐stressed plants, indicating that an inhibition had occurred. The maximum photochemical efficiency of photosystem II (Fv/Fm) decreased under heat, which correlated with the yield loss caused by the stress. Fv/Fm also decreased under combined heat and drought, though it did not related to the declined yield. A small leaf area prolonged the drying period of Gladius, and it was the genotype with the lowest decrease in yield because of stress. It is concluded that the effects of heat and combined heat and drought stress on the gas exchange and photosynthetic capacity on leaf area basis are not directly linked to the yield performance among wheat genotypes, while the morphological characteristics of the plants are important determinants of grain yield in response to those abiotic stresses. [ABSTRACT FROM AUTHOR]

Trees' responses to mistletoes occur at multiple organization levels (e.g., leaf, individual, population), yet integrating these multi‐scale responses is still challenging. Here, we compared the traits of infected versus uninfected trees over multiple scales, from leaf anatomy and physiology to canopy allometries and individual growth rate and survivorship. We tested the hypotheses that mistletoes lead in the host (1) the production of leaves with a conservative resource‐use strategy, (2) more mechanically stable canopies and (3) reductions in growth and survival probability in the trees they infect. We addressed these hypotheses in the widespread savanna tree Vochysia thyrsoidea and xylem‐tapping mistletoe Psittacanthus robustus in the Brazilian Cerrado, a global biodiversity hotspot. We found that (1) mistletoe infection did not affect key traits associated with resource conservativeness, such as leaf mass per area (LMA) and carbon assimilation rates (A). Likewise, (2) hosts did not increase the mechanical safety of their trunks in response to mistletoe infection since infected and uninfected trees had a similar allometric scaling between height and crown volume against stem diameter. (3) At the population level, both the relative growth rate and survival probability decreased as the number of parasites increased. However, zero growth and a 50% chance of mortality were estimated to occur in a minority of heavily infected trees (>7 and 14 parasites, respectively). Our results challenge the idea that mistletoes have a ubiquitous negative impact on their hosts. We highlight, therefore, the need for clarifying the mechanisms that allow trees to maintain their functioning even in the face of mistletoe parasitism. [ABSTRACT FROM AUTHOR]

Arid and semi-arid regions are characterised by extreme conditions including drought stress and salinity. These factors profoundly affect the agricultural sector. The objective of this work is to study the effect of drought and re-watering on leaf gas exchange, chlorophyll fluorescence and mineral nutrition in Pistacia vera and Pistacia atlantica. Water stress was applied to individuals of P. vera and P. atlantica for 23 days, followed by rehydration for 7 days. The results showed a clear reduction in water relations, leaf gas exchange and chlorophyll content in P. vera. Compared to P. vera, P. atlantica maintained less affected water status, total chlorophyll content, leaf gas exchange and chlorophyll fluorescence, stable Zn and Fe proportion, and even elevated K and Cu. The changes in the chlorophyll fluorescence parameter were manifested particularly at the maximal fluorescence (Fm). In contrast, no change was recorded at the minimal fluorescence (F0). After re-hydration, although water status was fully recovered in both species, stomatal conductance (gs), net photosynthesis (A) and transpiration rate (E) remain with lower values than the wellwatered seedlings. P. atlantica was better adapted to drought stress than P. vera. [ABSTRACT FROM AUTHOR]

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Rootstocks are used in modern apple production to increase productivity, abiotic and biotic stress tolerance, and fruit quality. While dwarfing for apple rootstocks has been well characterized, the physiological mechanisms controlling dwarfing have not. Previous research has reported rootstock effects on scion water relations. Root architecture and variability in soil moisture across rooting depths can also contribute to these differences among rootstocks in the field. To exclude these effects on rootstock behavior, scions were grafted onto four different rootstocks with varying effects on scion vigor (B.9, M.9, G.41 and G.890). Non-grafted rootstocks were also grown to examine whether the effects of rootstock occurred independently from scion grafting. Plants were grown in a greenhouse under near steady-state hydroponic conditions. Carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotope composition were evaluated and relationships with carbon assimilation, water relations, and shoot growth were tested. Rootstocks affected scion shoot growth, aligning with known levels of vigor for these four rootstocks, and were consistent between the two scion cultivars. Furthermore, changes in water relations influenced by rootstock genotype significantly affected leaf, stem, and root δ13C, δ18O, and δ15N. Lower δ13C and δ18O were inconsistently associated with rootstock genotypes with higher vigor in leaves, stems, and roots. G.41 had lower δ15N in roots, stems, and leaves in both grafted and ungrafted trees. The effects of rootstock on aboveground water relations were also similar for leaves of ungrafted rootstocks. This study provides further evidence that dwarfing for apple rootstocks is linked with physiological limitations to water delivery to the developing scion. [ABSTRACT FROM AUTHOR]

Summary: Shrub encroachment is a common ecological state transition in global drylands and has myriad adverse effects on grasslands and the services they provide. This physiognomic shift is often ascribed to changes in climate (e.g. precipitation) and disturbance regimes (e.g. grazing and fire), but this remains debated. Aeolian processes are known to impact resource distribution in drylands, but their potential role in grassland‐to‐shrubland state changes has received little attention.We quantified the effects of 'sandblasting' (abrasive damage by wind‐blown soil) on the ecophysiology of dryland grass vs shrub functional types using a portable wind tunnel to test the hypothesis that grasses would be more susceptible to sandblasting than shrubs and, thus, reinforce transitions to shrub dominance in wind‐erodible grasslands when climate‐ or disturbance‐induced reductions in ground cover occur.Grasses and shrubs responded differently to sandblasting, wherein water‐use efficiency declined substantially in grasses, but only slightly in shrubs, owing to grasses having greater increases in day/nighttime leaf conductance and transpiration.The differential ecophysiological response to sandblasting exhibited by grass and shrub functional types could consequently alter the vegetation dynamics in dryland grasslands in favour of the xerophytic shrubs. Sandblasting could thus be an overlooked driver of shrub encroachment in wind‐erodible grasslands. [ABSTRACT FROM AUTHOR]

Despite multiple studies of the impact of climate change on temperate tree species, experiments on tropical and economically important tree crops, such as cacao (Theobroma cacao L.), are still limited. Here, we investigated the combined effects of increased temperature and atmospheric carbon dioxide concentration ([CO2]) on the growth, photosynthesis and development of juvenile plants of two contrasting cacao genotypes: SCA 6 and PA 107. The factorial growth chamber experiment combined two [CO2] treatments (410 and 700 p.p.m.) and three day/night temperature regimes (control: 31/22 °C, control + 2.5 °C: 33.5/24.5 °C and control + 5.0 °C: 36/27 °C) at a constant vapour pressure deficit (VPD) of 0.9 kPa. At elevated [CO2], the final dry weight and the total and individual leaf areas increased in both genotypes, while the duration for individual leaf expansion declined in PA 107. For both genotypes, elevated [CO2] also improved light-saturated net photosynthesis (P n) and intrinsic water-use efficiency (i WUE), whereas leaf transpiration (E) and stomatal conductance (g s) decreased. Under a constant low VPD, increasing temperatures above 31/22 °C enhanced the rates of P n, E and g s in both genotypes, suggesting that photosynthesis responds positively to higher temperatures than previously reported for cacao. However, dry weight and the total and individual leaf areas declined with increases in temperature, which was more evident in SCA 6 than PA 107, suggesting the latter genotype was more tolerant to elevated temperature. Our results suggest that the combined effect of elevated [CO2] and temperature is likely to improve the early growth of high temperature-tolerant genotypes, while elevated [CO2] appeared to ameliorate the negative effects of increased temperatures on growth parameters of more sensitive material. The evident genotypic variation observed in this study demonstrates the scope to select and breed cacao varieties capable of adapting to future climate change scenarios. [ABSTRACT FROM AUTHOR]

Grapevine leaves contain abundant CaOx crystals located either within the mesophyll in the form of raphides, or in the bundle sheaths as druses. CaOx crystals function as internal carbon pools providing CO2 for a baseline level of photosynthesis, named "alarm photosynthesis", despite closed stomata; thus, preventing the photoinhibition and the oxidative risk due to carbon starvation under adverse conditions. Structural and functional leaf traits of acclimated grapevine plants (Vitis vinifera L. cv. Assyrtiko) were investigated in response to water availability, in order to evaluate the dynamic functionality of CaOx. Leaf water potential, leaf area, leaf mass per area, stomatal properties, gas exchange parameters and performance index (PI) were decreased in leaves of vines acclimated to water deficit in comparison to the leaves of well-irrigated vines, although the chlorophyll fluorescence parameters showed that the operational efficiency of the photosystem II (PSII) photochemistry (Fv/Fm) did not change, indicating that the photosynthetic apparatus was not subjected to water stress. During the afternoon, more than half of the morning's existing druses disappeared in the drought-acclimated leaves. Also, the raphides' area of the drought-acclimated leaves was reduced more than that of the well-watered leaves. The substantial decomposition of druses under water deficit conditions compared to that of the raphides may have important implications for the maintenance of their different though overlapping roles. According to the results, it seems likely that, under water deficit conditions, a mechanism of "alarm photosynthesis" provides an additional tolerance trait in the leaves of Vitis vinifera cv. Assyrtiko; hence, leaf structure relates to function. [ABSTRACT FROM AUTHOR]

Organic hydromulches (liquid spray-on mulches) have been used traditionally in land rehabilitation, mainly to mitigate post-fire runoff and erosion. However, in recent years, a new application of these materials as an eco-friendly alternative to the widely used polyethylene mulch, both in vegetable and woody crops, has been studyied. This work analyzes the effects of six hydromulches, based on organic by-products, on different soil parameters (water content, temperature, and CO2 flux), plant–water relations (stem water potential, leaf gas exchange, and leaf temperature), and the growth (trunk diameter) of young olive trees planted in large pots in the open field over a 2-year trial. The hydromulches tested were: rice husk (RH), rice husk with linen oil (RHL), mushroom substrate (MS), wheat straw (WS), pistachio (PW), and vineyard (VW) pruning wood chips, mixed with different additives (gypsum, recycled paper paste, and Kraft fiber). A non-mulched manual weeding control (NM) was included. The results indicated that hydromulches, in comparison with NM, resulted in increased volumetric soil water content (on average, 22.9% in hydromulches and 19.5% in NM), reduced soil temperature fluctuations (4.97 °C in hydromulches and 6.13 °C in NM), and increased soil CO2 fluxes (0.80 and 0.49 g CO2 m−2 h−1, respectively). Although the differences in the soil water content did not have an obvious effect on the plant–water status, crop growth was reduced in NM (≈23% lower than PW, MS, RHL, and WS), suggesting that vegetative growth, especially in young olive trees, is extremely sensitive to water deficit. The overall study leads to considering hydromulches as a good alternative to mulching in large pots, especially PW, which would be useful for nursery crops before their final establishment in the field. [ABSTRACT FROM AUTHOR]

Climate change, characterized by rising atmospheric CO2 levels and temperatures, poses significant challenges to global crop production. Sweet sorghum, a prominent C4 cereal extensively grown in arid areas, emerges as a promising candidate for sustainable bioenergy production. This study investigated the responses of photosynthesis and leaf-scale water use efficiency (WUE) to varying light intensity (I) in sweet sorghum under different temperature and CO2 conditions. Comparative analyses were conducted between the An-I, gs-I, Tr-I, WUEi-I, and WUEinst-I models proposed by Ye et al. and the widely utilized the non-rectangular hyperbolic (NRH) model for fitting light response curves. The Ye's models effectively replicated the light response curves of sweet sorghum, accurately capturing the diminishing intrinsic WUE (WUEi) and instantaneous WUE (WUEinst) trends with increasing I. The fitted maximum values of An, gs, Tr, WUEi, and WUEinst and their saturation light intensities closely matched observations, unlike the NRH model. Despite the NRH model demonstrating high R2 values for An-I, gs-I, and Tr-I modelling, it returned the maximum values significantly deviating from observed values and failed to generate saturation light intensities. It also inadequately represented WUE responses to I, overestimating WUE. Across different leaf temperatures, An, gs, and Tr of sweet sorghum displayed comparable light response patterns. Elevated temperatures increased maximum An, gs, and Tr but consistently declined maximum WUEi and WUEinst. However, WUEinst declined more sharply due to the disproportionate transpiration increase over carbon assimilation. Critically, sweet sorghum An saturated at current atmospheric CO2 levels, with no significant gains under 550 μmol mol−1. Instead, stomatal closure enhanced WUE under elevated CO2 by coordinated gs and Tr reductions rather than improved carbon assimilation. Nonetheless, this response diminished under simultaneously high temperature, suggesting intricate interplay between CO2 and temperature in modulating plant responses. These findings provide valuable insights into photosynthetic dynamics of sweet sorghum, aiding predictions of yield and optimization of cultivation practices. Moreover, our methodology serves as a valuable reference for evaluating leaf photosynthesis and WUE dynamics in diverse plant species.

As grapevine production is converting into irrigated systems worldwide, understanding rootstock-scion interactions at different stages of moderate drought can help to better manage water resources and the choice of rootstock. This study compared the physio-morphological drought response and recovery of a drought-sensitive (Riparia Gloire (Vitis riparia)) and a drought-tolerant rootstock (Ramsey (Vitis champinii)) grafted with Cabernet Sauvignon (Vitis vinifera), and the self-grafted control in a pot study. Ramsey had lower root-to-shoot ratio but higher performance of the root system under drought, explained by the lower root tissue density and tip suberization and higher VviPIP2;1 aquaporin expression, and faster recovery of root hydraulic conductivity and stomatal conductance after re-watering than Riparia. Riparia maintained better water status under moderate drought by early root suberization, but it was less able to restore water uptake capacity and support scion growth and leaf gas exchange after re-watering. This study shows a suite of rootstock traits that improve scion growth in response to moderate drought. Thus, these results identify traits for breeding programs and the selection of rootstocks for sustainable management of water resources under irrigated production.

Alfalfa is an important leguminous plant, yield and quality depend on the growing environment, while effects of drought and heat stress on alfalfa leaves are unknown. This study was conducted to evaluate the effect of exogenous ascorbic acid (AsA) on photosynthesis, chlorophyll fluorescence, and xanthophyll cycle in alfalfa leaves subject to under drought and heat stress. The results suggest that drought and heat stress caused decreases in the net photosynthetic rate (Pn) in alfalfa leaves, but stomatal conductance (gs), transpiration rate (Tr), and intercellular CO2 concentration (ci) were increased. The application of AsA could alleviate these changes to some extent. Besides, the decreased photosystem II (PSII) maximum photochemical efficiency (Fv/Fm) and violaxanthin (V) contents and significantly increased non-photochemical quenching (NPQ) levels. The increased NPQ corresponds to the de-epoxidation state (DPS) of xanthophyll pigments. In the AsA-pretreated alfalfa plants, the Fv/Fm and the NPQ were elevated, indicating that AsA could alleviate the adverse effects on photosynthesis induced by this stress. The violaxanthin de-epoxidase (VDE) enzyme activity was inhibited by drought and heat stress, and AsA significantly increased VDE enzymatic activity on the 2nd and 8th days. In summary, photoinhibition of PSII occurred in alfalfa leaves under drought and heat stress, resulting in decreased photosynthetic activity. Exogenous AsA can enhance the photosynthetic capacity of the plant, and enhance the drought and heat resistance of alfalfa.

Rising air temperatures have the capacity to impact rice yields in future climates. Studies in large temperature-controlled field chambers were established to examine the responses of four contrasting rice genotypes to elevated daytime temperatures (ET) during reproductive development under paddy conditions. Field chambers were effective in raising mean above-canopy maximum daytime temperatures from 29.9 to 41.1°C during 12 d of ET treatment (68–80 d after emergence, DAE), while increased transpiration under ET resulted in lowering of mean lower-canopy maximum temperature to 33.2°C. Nevertheless, the earliest genotype Vandana encountered a hot spell of 37.0°C at 68–74 DAE in the lower canopy at its late reproductive stage, which exceeded the spikelet sterility threshold of 33.7°C, so its spikelet fertility, grain number and grain yield were reduced under ET. Genotypes differed in the extent of canopy cooling, with less reduction in Vandana and IR64 than in N22 and Takanari. For canopy cooling to be effective, stratification of air layers must occur within the canopy, which was more effective under the shorter and denser canopy of N22 and Takanari (plant height of 70–80 ​cm) than under IR64 (90–110 ​cm) and Vandana (115–130 ​cm). Genotypes with appropriate canopy structures should be chosen for high vapour pressure deficit (VPD) conditions. Both maximum canopy temperature and VPD need to be specified to define the critical threshold for heat tolerance. Takanari was notable for greater leaf area retention and greater leaf photosynthetic capacity due to the maintenance of a higher internal leaf CO2 concentration, which led to higher spikelet and grain numbers and higher yield potential under ET conditions.

Zinc enrichment of edible food products, through the soil and/or foliar application of fertilizers, is a strategy that can increase the contents of some nutrients, namely Zn. In this context, a workflow for agronomic enrichment with zinc was carried out on irrigated Vitis vinifera cv. Syrah, aiming to evaluate the mobilization of photoassimilates to the winegrapes and the consequences of this for winemaking. During three productive cycles, foliar applications were performed with ZnSO4 or ZnO, at concentrations ranging between 150 and 1350 g.ha−1. The normal vegetation index as well as some photosynthetic parameters indicated that the threshold of Zn toxicity was not reached; it is even worth noting that with ZnSO4, a significant increase in several cases was observed in net photosynthesis (Pn). At harvest, Zn biofortification reached a 1.2 to 2.3-fold increase with ZnSO4 and ZnO, respectively (being significant relative to the control, in two consecutive years, with ZnO at a concentration of 1350 g.ha−1). Total soluble sugars revealed higher values with grapes submitted to ZnSO4 and ZnO foliar applications, which can be advantageous for winemaking. It was concluded that foliar spraying was efficient with ZnO and ZnSO4, showing potential benefits for wine quality without evidencing negative impacts.

Many recent studies have highlighted the importance of plant growth-promoting (rhizo)bacteria (PGPR) in supporting plant’s development, particularly under biotic and abiotic stress. Most focus on the plant growth-promoting traits of selected strains and the latter’s effect on plant biomass, root architecture, leaf area, and specific metabolite accumulation. Regarding energy balance, plant growth is the outcome of an input (photosynthesis) and several outputs (i.e., respiration, exudation, shedding, and herbivory), frequently neglected in classical studies on PGPR-plant interaction. Here, we discuss the primary evidence underlying the modifications triggered by PGPR and their metabolites on the plant ecophysiology. We propose to detect PGPR-induced variations in the photosynthetic activity using leaf gas exchange and recommend setting up the correct timing for monitoring plant responses according to the specific objectives of the experiment. This research identifies the challenges and tries to provide future directions to scientists working on PGPR-plant interactions to exploit the potential of microorganisms’ application in improving plant value.

Rootstocks are used in modern apple production to increase productivity, abiotic and biotic stress tolerance, and fruit quality. While dwarfing for apple rootstocks has been well characterized, the physiological mechanisms controlling dwarfing have not. Previous research has reported rootstock effects on scion water relations. Root architecture and variability in soil moisture across rooting depths can also contribute to these differences among rootstocks in the field. To exclude these effects on rootstock behavior, scions were grafted onto four different rootstocks with varying effects on scion vigor (B.9, M.9, G.41 and G.890). Non-grafted rootstocks were also grown to examine whether the effects of rootstock occurred independently from scion grafting. Plants were grown in a greenhouse under near steady-state hydroponic conditions. Carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotope composition were evaluated and relationships with carbon assimilation, water relations, and shoot growth were tested. Rootstocks affected scion shoot growth, aligning with known levels of vigor for these four rootstocks, and were consistent between the two scion cultivars. Furthermore, changes in water relations influenced by rootstock genotype significantly affected leaf, stem, and root δ13C, δ18O, and δ15N. Lower δ13C and δ18O were inconsistently associated with rootstock genotypes with higher vigor in leaves, stems, and roots. G.41 had lower δ15N in roots, stems, and leaves in both grafted and ungrafted trees. The effects of rootstock on aboveground water relations were also similar for leaves of ungrafted rootstocks. This study provides further evidence that dwarfing for apple rootstocks is linked with physiological limitations to water delivery to the developing scion.

Manganese (Mn) is one of the essential mineral micronutrients most demanded by cacao. Cadmium (Cd) is highly toxic to plants and other living beings. There are indications that Mn can interact with Cd and mitigate its toxicity. The objective of this study was to evaluate the action of Mn on the toxic effect of Cd in young plants of the CCN 51 cacao genotype, subjected to different doses of Mn, Cd, and Mn+Cd in soil, through physiological, biochemical, molecular, and micromorphological and ultrastructural changes. High soil Mn doses favored the maintenance and performance of adequate photosynthetic processes in cacao. However, high doses of Cd and Mn+Cd in soil promoted damage to photosynthesis, alterations in oxidative metabolism, and the uptake, transport, and accumulation of Cd in roots and leaves. In addition, high Cd concentrations in roots and leaf tissues caused irreversible damage to the cell ultrastructure, compromising cell function and leading to programmed cell death. However, there was a mitigation of Cd toxicity when cacao was grown in soils with low Cd doses and in the presence of Mn. Thus, damage to the root and leaf tissues of cacao caused by Cd uptake from contaminated soils can be attenuated or mitigated by the presence of high Mn doses in soil. [ABSTRACT FROM AUTHOR]

• Microplastics and Cd toxicity exert adverse effects on belowground traits. • Crop performance is adversely affected by microplastics and Cd pollution. • Microplastic contamination was less detrimental than Cd toxicity. • Exposure to both treatments severely affected the antioxidants enzymes activity. Cadmium toxicity in the soil severely threatens many native ecosystems, including plant communities. Microplastic (MP) accumulation in agricultural ecosystems constitutes a problem due to the fact that it stresses crops as well as lowers their production. On the other hand, it has yet to be apparent how MP pollution and Cd toxicity affect crops. In this instance, wheat plants subjected to polyethylene MP contamination, Cd toxicity, and a combined treatment were used in a greenhouse setting to assess above- and below-ground crop features related to stress responses utilizing root scan and leaf gas exchange studies. Changes in root characteristics, a decrease in leaf gas exchange, and phenological indices were among the consequences that were noticed. Regarding below- and above-ground features, MP pollution was the treatment that had the fewest negative effects, whereas cadmium toxicity along with soil MP contamination had the worst effects. Additionally, Cd toxicity and interaction treatment lowered root area and width, while MP pollution enhanced all belowground variables. Combined treatment with MPs and Cd toxicity reduced phenological indices, leaf gas exchange, and belowground root traits compared to control. These insights raise concerns regarding potential yield, economic losses, and consequences of a possible transport into the food web. [ABSTRACT FROM AUTHOR]

Reduction of yield in tropical greenhouses is an issue with Cucumis melo L. var. cantaloupensis. A natural occurring hormone, 24-epibrassinolide (EBR), regulates cellular activities and physiological processes of plants and signaling. To determine effects of EBR application, cantaloupe cvs. Himalai-99 and Glamour (factor 1) were treated with 0.1 mg∙L−1 EBR applied over four frequencies (factor 2) as; F1: no EBR (control), F2: at 15 DAT (days after transplant), F3: at 15 + 30 DAT, and F4: at 15 + 30 + 45 DAT at 47 ± 3°C (5°C higher than the ambient greenhouse) in a factorial Randomized Complete Block Design (RCBD) with four replicates. Postharvest fruit quality was monitored at room temperature (26°C) in a completely randomized design with four replicates. Data were analyzed using Analysis of Variance, mean separation with least significant difference and associations between parameters with Pearson correlation. Application of EBR at 15 + 30 DAT (F3) increased plant dry weight, leaf area, specific leaf area, root length, root surface area, photosynthesis rate, stomatal conductance, transpiration rate and chlorophyll content. It increased the quantum efficiency of photosystem II, peroxidase and catalase activities by 50%, stomatal length and width by 75% and decreased malondialdehyde and proline content by 56%. Pre-harvest foliar application of EBR at 15 + 30 DAT reduced postharvest weight loss and ethylene emission rate by two fold and reduced ascorbic acid and antioxidant depletion rates during storage. The EBR application at 15 + 30 DAT produced the best plant and fruit quality performances, while the application of EBR at fruit development stage (45 DAT) caused reduced fruit quality. [ABSTRACT FROM AUTHOR]

Salinity stress is severely affecting modern horticulture and puts food security under threat for current and future generations. The aim of the present study was to evaluate the effect of saline conditions (three salinity levels: 2.0, 5.0 and 10.0 dS m−1) on the growth, physiological processes and quality of two wild edible species (Urospermum picroides and Reichardia picroides) grown under three different cropping systems (pots indoors (GP) and outdoors (FP); and floating hydroponics (FH)). Our results indicate that high salinity affected growth parameters in all the studied cropping systems in the case of U. picroides, whereas R. picroides was not affected only when grown in pots outdoors. Moreover, total soluble solids content and titratable acidity in both species were not affected by high salinity for any of the cropping systems, except for in the case of FP system. Similarly, carotenoids content decreased under high salinity when both species were grown in the FP system. A varied effect was recorded for total phenolic compounds content in response to salinity levels, although the FP system resulted in considerably higher phenolics accumulation in both species, while proline content increased when plants were subjected to high salinity, regardless of the cropping system. The antioxidant activity also varied among the studied treatments for both assays (TEAC and FRAP), although cultivation outdoors in pots resulted in considerably higher values compared to the other systems. Finally, nitrate content showed decreasing trends with increasing salinity in plants grown in the GP (both species) and FP system (only U. picroides), whereas no significant differences in physiological parameters in comparison to the control treatment were recorded, except for the stomatal conductance (FP and GP system) and transpiration rate (FP) of R. picroides plants. In conclusion, it seems that the tested plant species responded differently to the salinity treatments but they both displayed a lack of severe stress even at high salinity. [ABSTRACT FROM AUTHOR]