Search

Summary: Elevated air temperature (Tair) and vapour pressure deficit (VPDair) significantly influence plant functioning, yet their relative impacts are difficult to disentangle.We examined the effects of elevated Tair (+6°C) and VPDair (+0.7 kPa) on the growth and physiology of six tropical tree species. Saplings were grown under well‐watered conditions in climate‐controlled glasshouses for 6 months under three treatments: (1) low Tair and low VPDair, (2) high Tair and low VPDair, and (3) high Tair and high VPDair. To assess acclimation, physiological parameters were measured at a set temperature.Warm‐grown plants grown under elevated VPDair had significantly reduced stomatal conductance and increased instantaneous water use efficiency compared to plants grown under low VPDair. Photosynthetic biochemistry and thermal tolerance (Tcrit) were unaffected by VPDair, but elevated Tair caused Jmax25 to decrease and Tcrit to increase. Sapling biomass accumulation for all species responded positively to an increase in Tair, but elevated VPDair limited growth.This study shows that stomatal limitation caused by even moderate increases in VPDair can decrease productivity and growth rates in tropical species independently from Tair and has important implications for modelling the impacts of climate change on tropical forests. [ABSTRACT FROM AUTHOR]

Summary: Climate change is simultaneously increasing carbon dioxide concentrations ([CO2]) and temperature. These factors could interact to influence plant physiology and performance. Alternatively, increased [CO2] may offset costs associated with elevated temperatures. Furthermore, the interaction between elevated temperature and [CO2] may differentially affect populations from along an elevational gradient and disrupt local adaptation.We conducted a multifactorial growth chamber experiment to examine the interactive effects of temperature and [CO2] on fitness and ecophysiology of diverse accessions of Boechera stricta (Brassicaceae) sourced from a broad elevational gradient in Colorado. We tested whether increased [CO2] would enhance photosynthesis across accessions, and whether warmer conditions would depress the fitness of high‐elevation accessions owing to steep reductions in temperature with increasing elevation in this system. Elevational clines in [CO2] are not as evident, making it challenging to predict how locally adapted ecotypes will respond to elevated [CO2].This experiment revealed that elevated [CO2] increased photosynthesis and intrinsic water use efficiency across all accessions. However, these instantaneous responses to treatments did not translate to changes in fitness. Instead, increased temperatures reduced the probability of reproduction for all accessions. Elevated [CO2] and increased temperatures interacted to shift the adaptive landscape, favoring lower elevation accessions for the probability of survival and fecundity.Our results suggest that elevated temperatures and [CO2] associated with climate change could have severe negative consequences, especially for high‐elevation populations. [ABSTRACT FROM AUTHOR]

Summary: Theoretically, the PEP‐CK C4 subtype has a higher quantum yield of CO2 assimilation (ΦCO2) than NADP‐ME or NAD‐ME subtypes because ATP required for operating the CO2‐concentrating mechanism is believed to mostly come from the mitochondrial electron transport chain (mETC). However, reported ΦCO2 is not higher in PEP‐CK than in the other subtypes. We hypothesise, more photorespiration, associated with higher leakiness and O2 evolution in bundle‐sheath (BS) cells, cancels out energetic advantages in PEP‐CK species.Nine species (two to four species per subtype) were evaluated by gas exchange, chlorophyll fluorescence, and two‐photon microscopy to estimate the BS conductance (gbs) and leakiness using a biochemical model.Average gbs estimates were 2.9, 4.8, and 5.0 mmol m−2 s−1 bar−1, and leakiness values were 0.129, 0.179, and 0.180, in NADP‐ME, NAD‐ME, and PEP‐CK species, respectively. The BS CO2 level was somewhat higher, O2 level was marginally lower, and thus, photorespiratory loss was slightly lower, in NADP‐ME than in NAD‐ME and PEP‐CK species. Differences in these parameters existed among species within a subtype, and gbs was co‐determined by biochemical decarboxylating sites and anatomical characteristics.Our hypothesis and results partially explain variations in observed ΦCO2, but suggest that PEP‐CK species probably use less ATP from mETC than classically defined PEP‐CK mechanisms. [ABSTRACT FROM AUTHOR]

Crown rot (CR; Fusarium pseudograminearum) is a serious disease in winter cereals. Soil type, temperature, nutrients, water availability and stubble‐borne inoculum levels play major roles in determining disease severity. This paper reports the impact of two different watering regimes on the disease severity and gas exchange of F. pseudograminearum infected bread wheat for the first time. Fusarium pseudograminearum inoculated and noninoculated genotypes with different susceptibility to CR were watered to either field capacity or a reduced watering regime in three controlled environment experiments. Rate of photosynthesis, stomatal conductance, internal CO2 concentration and transpiration rate were measured using a portable photosynthesis system, together with disease severity of leaf sheaths at 28 days after planting. Significant differences in disease severity were reported between watering treatments with reduction in CR symptoms in the partially resistant genotypes in the reduced water treatment. Photosynthesis, stomatal conductance and transpiration rate were significantly decreased across most genotypes when inoculated with F. pseudograminearum. Differences in gas exchange between inoculum treatments were more evident in plants watered to field capacity. Water availability has been reported to be one of the crucial factors for initiating F. pseudograminearum infection and subsequent development of CR disease. This research demonstrates significant variation in genotype‐related responses to the complex interactions of F. pseudograminearum infection and water treatment, with a negative impact of both limited soil water availability and CR disease severity on plant gas exchange in bread wheat. [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]

This article discusses the importance of phenotyping photosynthesis for crop improvement and breeding programs. The authors highlight the challenges of studying photosynthesis in natural conditions and the need for higher throughput tools to overcome these barriers. They discuss the use of controlled-environment systems and remote sensing methods, such as solar-induced fluorescence and laser/light-induced fluorescence transient, for phenotyping photosynthesis. The authors also mention the use of hand-held MultispeQ PAM fluorometers as affordable tools for field phenotyping. The article concludes by emphasizing the potential of photosynthetic phenotyping for driving yield improvement in crop breeding programs. [Extracted from the article]

Viscum schimperi is an evergreen hemiparasitic plant that can grow on stems and branches of several tree species. It penetrates the host tissues and forms a vascular bridge (haustorium) to withdraw the nutritive resources. Its relationships with hosts remain unknown. This study aimed to investigate the physiological and biochemical attributes of the host-hemiparasite association Acacia gerrardii-Viscum schimperi. The hemiparasite exhibited 2.4- and 3.0-fold lower photosynthetic activity and water use efficiency, and 1.2- and 4.1-fold higher transpiration rate and stomatal conductance. Equally, it displayed 4.9- and 2.6-fold greater water potential and osmotic potential, and in least 3.0 times more accumulated 39K, 85Rb and 51V, compared to the host. Nevertheless, it had no detrimental effect on photosynthetic activity, water status and multi-element accumulations in the host. Based on metabolome profiling, V. schimperi could use xanthurenic acid and propylparaben to acquire potassium from the host, and N-1-naphthylacetamide and N-Boc-hydroxylamine to weaken or kill the distal part of the infected branch and to receive the total xylem contents. In contrast, A. gerrardii could used N-acetylserotonin, arecoline, acetophenone and 6-methoxymellein to defend against V. schimperi infection. [ABSTRACT FROM AUTHOR]

Rising temperatures pose a threat to the stability of climate regulation by carbon metabolism in subtropical forests. Although the effects of temperature on leaf carbon metabolism traits in sun-exposed leaves are well understood, there is limited knowledge about its impacts on shade leaves and the implications for ecosystem–climate feedbacks. In this study, we measured temperature response curves of photosynthesis and respiration for 62 woody species in summer (including both evergreen and deciduous species) and 20 evergreen species in winter. The aim was to uncover the temperature dependence of carbon metabolism in both sun and shade leaves in subtropical forests. Our findings reveal that shade had no significant effects on the mean optimum photosynthetic temperatures (TOpt) or temperature range (T90). However, there were decreases observed in mean stomatal conductance, mean area-based photosynthetic rates at TOpt and 25 °C, as well as mean area-based dark respiration rates at 25 °C in both evergreen and deciduous species. Moreover, the respiration–temperature sensitivity (Q10) of sun leaves was higher than that of shade leaves in winter, with the reverse being true in summer. Leaf economics spectrum traits, such as leaf mass per area, and leaf concentration of nitrogen and phosphorus across species, proved to be good predictors of TOpt, T90, mass-based photosynthetic rate at TOpt, and mass-based photosynthetic and respiration rate at 25 °C. However, Q10 was poorly predicted by these leaf economics spectrum traits except for shade leaves in winter. Our results suggest that model estimates of carbon metabolism in multilayered subtropical forest canopies do not necessitate independent parameterization of T90 and TOpt temperature responses in sun and shade leaves. Nevertheless, a deeper understanding and quantification of canopy variations in Q10 responses to temperature are necessary to confirm the generality of temperature–carbon metabolism trait responses and enhance ecosystem model estimates of carbon dynamics under future climate warming. [ABSTRACT FROM AUTHOR]

Root pruning hinders the absorption and utilization of nutrients and water by seedlings in the short term. Arbuscular mycorrhizal fungi (AMF) are an important source of nutrient and water for seedlings except for the root system. However, the mechanism by which AMF affect the physiological growth of seedlings after root pruning has rarely been studied. In this study, a pot experiment was conducted through a three-compartment partition system to clarify the effects of Funneliformis mosseae (F. mosseae) strain BGC XJ07A on the physiological growth of root-pruned Robinia pseudoacacia seedlings. Five root pruning treatments (zero, one-fifth, one-fourth, one-third and one-half of the taproot length were removed) were applied to noninoculated seedlings and those inoculated with F. mosseae. The results showed that the presence of F. mosseae significantly increased the shoot and root biomasses, leaf photosynthetic rate, stomatal conductance and transpiration rate. The root projected area, root surface area, average root diameter, root density, root volume and number of root tips of the inoculated seedlings were higher than those without inoculation in all root pruning treatments. The root cytokinin, gibberellins and indole-3-acetic acid concentrations, but root abscisic acid concentration, were higher than those measured in the absence of inoculation in all root pruning treatments. Moreover, the changes in the root endogenous hormone concentrations of the seedlings were closely related to the root morphological development and seedling biomass. The AMF increased the soil available nitrogen, soil available phosphorus, soil available potassium and soil organic matter concentrations compared with the noninoculated treatment. These results indicate that AMF can alleviate the adverse effects of root pruning on the physiological growth of R. pseudoacacia and soil properties, and can provide a basis for AMF application to forest cultivation and the sustainable development of forest ecosystems. [ABSTRACT FROM AUTHOR]

Water stress can trigger acclimation responses and damage plants. The aim of this study was to evaluate the integrative responses of cotton hydraulic conductance, leaf photosynthesis, and carbon metabolism to short-term drought and subsequent rewatering. A water-controlled pot experiment was conducted in 2020, with soil water drying continuing for one day (D1), two days (D2), and three days (D3) after it reached 40% ± 5% of the soil water holding capacity at the blooming stage of cotton, and the soil was then rewatered to the soil water holding capacity. We investigated how the stem hydraulic conductance, gas exchange, and biochemical traits of cotton were affected by imposed drought stress and subsequent rewatering. The hydraulic characteristics of cotton in the D2 and D3 treatments evolved with damage, complete closure of stomatal conductance, and complete deterioration of photosynthesis, in addition to severe floating changes in the carbon metabolism affected by drought. The leaves' functional characteristics after rewatering cannot be completely recovered to full-irrigation levels, and the recovery extent was strongly linked to the duration. Consequently, it is considered desirable to maintain normal physiological activity during the cotton reproductive period, and the drought episode can be sustained for 1 day in a long-term perspective when the soil water content is depleted to 40% ± 5% of the soil water holding capacity. These results can provide in-depth ideas for better understanding the hydraulic and physiological responses of cotton to drought episodes and rewatering, and they can help drought-affected cotton to cope with future climate change. [ABSTRACT FROM AUTHOR]

Background: The leaf epidermis plays an important role in the transmission of light and the regulation of water and gas exchange, which influences the photosynthesis of mesophyll cells. Small papillae (SP) are one of the important structural elements of the leaf epidermis. The mechanism of the effect that small papillae have on rice leaf photosynthetic performance remains unclear. Results: In this study, a small papilla deficient 25 (spd25) mutant was isolated from japonica rice Longjin1. Small papillae were absent on the adaxial and abaxial leaf surfaces of the spd25 mutant and the silicon and cuticular wax content in the spd25 mutant leaves decreased. Map-based cloning and functional analysis revealed that SPD25, encoding a guanine nucleotide exchange factor for Rop, is a novel allele of OsRopGEF10. The spd25 mutant showed an increased water loss rate and reduced relative water content. The lower stomatal conductance in the spd25 mutant prevented water loss but decreased the intercellular CO2 concentration and net assimilation rate. The fluorescence parameters showed that the inhibited CO2 assimilation reaction feedback regulated the photochemical electron-transfer reaction, but the performance of Photosystem II was stable. Further analysis indicated that the excess light energy absorbed by the spd25 mutant was dissipated in the form of non-photochemical quenching to avoid photodamage through the optical properties of small papillae. Conclusions: SPD25 regulates the development of small papillae on the surface of rice leaves, which play an important role in balancing photosynthetic gas exchange and water loss. This study deepens our understanding of the physiological mechanisms by which small papillae affect photosynthetic performance. [ABSTRACT FROM AUTHOR]

Grape rain-shelter cultivation is a widely employed practice in China. At present, the most commonly used rain shelter film materials are polyvinyl chloride (PVC), polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), and polyolefin (PO). Coverlys TF150® is a woven fabric with an internal antifoggy PE coating that has not yet been popularized as a rain shelter film for grapes in China. To investigate the effects of Coverlys TF150® on grapes, we measured the microdomain environment, leaf development, and photosynthetic characteristics of 'Miguang' (Vitis vinifera × V. labrusca) under rain-shelter cultivation and performed transcriptome analysis. The results showed that Coverlys TF150® significantly reduced (p < 0.05) the light intensity, temperature, and humidity compared with PO film, increased the chlorophyll content and leaf thickness (particularly palisade tissue thickness), and increased stomatal density and stomatal opening from 10:00 to 14:00. Coverlys TF150® was observed to improve the maximum efficiency of photosystem II (Fv/Fm), photochemical quenching (qP), the electron transfer rate (ETR), and the actual photochemical efficiency (ΦPSII) from 10:00 to 14:00. Moreover, the net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), stomatal conductance (Gs), and transpiration rate (Tr) of grape leaves significantly increased (p < 0.05) from 10:00 to 14:00. RNA-Seq analysis of the grape leaves at 8:00, 10:00, and 12:00 revealed 1388, 1562, and 1436 differential genes at these points in time, respectively. KEGG enrichment analysis showed the occurrence of protein processing in the endoplasmic reticulum. Plant hormone signal transduction and plant-pathogen interaction were identified as the metabolic pathways with the highest differential gene expression enrichment. The psbA encoding D1 protein was significantly up-regulated in both CO10vsPO10 and CO12vsPO12, while the sHSPs family genes were significantly down-regulated in all time periods, and thus may play an important role in the maintenance of the photosystem II (PSII) activity in grape leaves under Coverlys TF150®. Compared with PO film, the PSI-related gene psaB was up-regulated, indicating the ability of Coverlys TF150® to better maintain PSI activity. Compared with PO film, the abolic acid receptacle-associated gene PYL1 was down-regulated at all time periods under the Coverlys TF150® treatment, while PP2C47 was significantly up-regulated in CO10vsPO10 and CO12vsPO12, inducing stomatal closure. The results reveal that Coverlys TF150® alleviates the stress of high temperature and strong light compared with PO film, improves the photosynthetic capacity of grape leaves, and reduces the midday depression of photosynthesis. [ABSTRACT FROM AUTHOR]

Gas exchange across the stomatal pores of leaves is a focal point in studies of plant‐environmental relations. Stomata regulate atmospheric exchange with the inner air spaces of the leaf. They open to allow CO2 entry for photosynthesis and close to minimize water loss. Models that focus on the phenomenology of stomatal conductance generally omit the mechanics of the guard cells that regulate the pore aperture. The OnGuard platform fills this gap and offers a truly mechanistic approach with which to analyse stomatal gas exchange, whole‐plant carbon assimilation and water‐use efficiency. Previously, OnGuard required specialist knowledge of membrane transport, signalling and metabolism. Here we introduce OnGuard3e, a software package accessible to ecophysiologists and membrane biologists alike. We provide a brief guide to its use and illustrate how the package can be applied to explore and analyse stomatal conductance, assimilation and water use efficiencies, addressing a range of experimental questions with truly predictive outputs. Summary statement: OnGuard3e offers a truly mechanistic approach with which to analyse stomatal gas exchange, whole‐plant carbon assimilation and water‐use efficiency. The software package seamlessly connects whole‐plant gas exchange and photosynthesis with the microscopic mechanics of stomata and is accessible to ecophysiologists and membrane biologists alike. We provide a brief guide to its use and illustrate how the package can be applied to explore and analyse stomatal conductance, assimilation and water use efficiencies, addressing a range of experimental questions with truly predictive outputs. [ABSTRACT FROM AUTHOR]

Background and Aims: Phosphorus (P) is a restricting nutrient for crop productivity worldwide. P deficiency can lead to stunted growth and development, eventually affecting crop yield. But less is documented about the impact of P fertility on industrial hemp (Cannabis sativa L.) production in the low-P soils of south-western Australia. We aimed to investigate the effect of P rates on growth, physiology, rhizosphere carboxylate exudation, nutrient uptake and P-use efficiency in hemp. Methods: The study was conducted in a randomised complete block design with four P rates (0, 40, 80 and 120 mg P kg–1 dry soil) and three hemp varieties (Morpeth, Han FNQ and Fedora 17). Plants were grown and raised in a controlled-environment phytotron until harvested 35 days after sowing at vegetative growth stage (3rd to nth leaf pair). Results: Our results revealed a strong influence of treatment (P rate) on hemp growth, physiology, biomass, nutrient uptake and P-use efficiency compared to variety and the variety × treatment interaction. Hemp roots predominantly released citrate in P-deficient conditions and gradually shifted to malate exudation with increasing P supply. The N:P ratio, leaf chlorophyll, and gas exchange data coupled with shoot and root length data suggest that Morpeth and Fedora 17 differ in morpho-physiological adaptations for optimum photosynthesis and growth, with high leaf chlorophyll and coarse root length achieved by Morpeth and high intercellular CO2 concentration and shoot length by Fedora 17. Conclusions: Morpeth and Fedora 17 had high shoot biomass, root length, root surface area and agronomic P-use and P-utilisation efficiencies in response to increasing soil P, while Han FNQ had moderate shoot yield, root growth, high citrate exudation, tissue P concentration and P-uptake efficiency. [ABSTRACT FROM AUTHOR]

• Chromium (Cr) at 20 mg kg−1 displayed encouraging effects on the physiology of Mentha arvensis. • Cr at 80 mg kg−1 showed deleterious effects on plants. • Excessive Cr accumulation destabilizes plant's growth, photosynthesis and physiological markers. • Cr at higher concentration diminishes the essential oil production including menthol content. Chromium (Cr) is the seventh most toxic heavy metal on the earth's crust. Crop growth, development, and yield are greatly hindered by the massive accumulation of Cr that discharges from various industries and mines in agricultural land. Chromium can mediate phytotoxicity either via direct interaction with multiple plant components and metabolic pathways or by promoting reactive oxygen species (ROS) generation. Thus, this investigation evaluated the effect of Cr on growth, physiological and oxidative stress, and other parameters, including essential oil (EO) constituents of Mentha arvensis L. plants. The soil was treated with various concentrations of Cr (10, 20, 40, 60, and 80 mg kg−1), except the control. In this study, 20 mg kg−1 of Cr concentration was beneficial in increasing plant growth via the enhancement of biomass, photosynthesis, biochemical markers and EO constituents in M. arvensis. The data demonstrated that the morphological and physiological parameters were negatively correlated with high Cr concentrations (above 20 mg kg−1). It has been hypothesized that Cr poisoning leads to oxidative damage, as evidenced by decreases in photosynthetic rate, chlorophyll, and stomatal characteristics, as well as increases in lipid peroxidation and ROS. The accumulation of Cr positively correlates with the enhancement of proline and antioxidant activities of M. arvensis. Thus, we concluded that excess Cr causes redox imbalance by uplifting the level of lipid peroxidation and ROS by destabilizing photosynthetic machinery and other physiological and morphological markers in plants. [ABSTRACT FROM AUTHOR]

This study aimed to provide insights on intraspecific variability of photosynthesis performance of 19 provenances of black pine planted in a common garden. The experiment was conducted in an experimental trial located at Souiniet (the southern limit of its range) Photosynthetic capacity characterized by lightsaturated net photosynthetic rates, associated light compensation points and apparent quantum yield was monitored by measuring the response of leaf gas exchange to light levels. Amax was the highest in provenances Puget Theniers (nigra ssp), Saint-Guilhem (salzmanni ssp), Marghese and les barres (laricio ssp). The lowest value was recorded in Olette of the subspecies salzmanni. Needles from two provenances Crimea (pallasiana ssp) and Les Barres (ssp laricio) revealed the highest apparent quantum yield (1), followed by Brougatlès Ales (salzmanni ssp), Trenta Coste (ssp laricio), Les barres and Puget Theniers (nigra ssp). The lowest apparent quantum Yield was recorded in Laricio subspecies (Cosenza; Les barres and Bois frerot). The highest value of dark respiration (Rd) was shown in provenance Les barres (laricio ssp), while Grancia and Tavola of the laricio subspecies reported the lowest one. Provenances Tavola (laricio ssp) and Puget Theniers (nigra ssp) exhibited the highest LCP. The provenance Crimée (pallasiana ssp) and Aspromonto (laricio ssp) recorded the lowest values. The maximum values of photosynthesis are positively correlated with the total chlorophyll contents and Leaf Mass area. Our study illustrates that Photosynthesis performance showed a difference between 19 provenances of black pine; it seems that black pine photosynthetic performance is eco-typical independent. [ABSTRACT FROM AUTHOR]

Contamination by heavy metals has severely hampered agricultural productivity across the world. Cadmium (Cd) is one of the most dangerous heavy metals to plants. Melatonin (ME), a stress-relief hormone, has been extensively utilized to reduce phytotoxicity caused by heavy metals. In this work, we examined how ME reduced Cd damage in strawberry seedlings. The results revealed that Cd stress dramatically reduced growth characteristics (fresh and dry weight, root and shoot length), leaf gas exchange elements, and pigments content (chlorophyll a and chlorophyll b) in strawberry seedlings. In contrast, ME application efficiently enhanced growth and biomass production, increased net photosynthetic rate, and improved pigments molecules in strawberry seedling under Cd toxicity. Cadmium treatment effectively improved the level of malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2), whereas ME strictly counterbalanced these oxidative stress markers. Furthermore, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), were dominantly increased by ME. Additionally, ME supplementation significantly improved secondary metabolites (phenols, anthocyanin, and flavonoids) content, and these metabolites potentially restricted excess H 2 O 2 accumulation. In conclusion, our results revealed that ME might help to reduce Cd-induced phytotoxicity in strawberry seedlings by increasing growth, photosynthesis, redox homeostasis, and secondary metabolites. [Display omitted] • Melatonin enhanced cadmium stress tolerance in strawberry plants. • Melatonin stimulates antioxidant defense system in strawberry seedling under cadmium toxicity. • Melatonin increased photosynthesis apparatus in cadmium-stressed strawberry plants. • Melatonin as a supplement regulates defense mechanism in strawberry under cadmium stress. [ABSTRACT FROM AUTHOR]

Clarifying the mechanisms underlying the recovery of gas exchange following drought is the key to providing insights into plant drought adaptation and habitat distribution. However, the mechanisms are still largely unknown. Targeting processes known to inhibit gas exchange during drought recovery, we measured leaf water potential, the leaf hydraulic conductance, stomatal reopening, abscisic acid (ABA) and the ethylene emission rate (EER) following moderate drought stress in seedlings of the globally pervasive woody tree Fraxinus chinensis. We found strong evidence that the slow stomatal reopening after rehydration is regulated by a slow decrease in EER, rather than changes in leaf hydraulics or foliar ABA levels. This was supported by evidence of rapid gas exchange recovery in plants after treatment with the ethylene antagonist 1-methylcyclopropene. These findings provide evidence to rigorously support ethylene as a key factor constraining stomatal reopening from moderate drought directly, thereby potentially opening new windows for understanding species drought adaptation. [ABSTRACT FROM AUTHOR]

Nonetheless, the content of photosynthetic pigments (chlorophylls and carotenoids) in I T. japonicum i roots was approximately half of that in the leaves, whereas the pigment content in I T. aphyllum i roots was similar to that in I T. japonicum i leaves (Fig. Keywords: 14CO2 labeling; carbon acquisition; chlorophyll fluorescence; crassulacean acid metabolism (CAM); Orchidaceae; radioisotope EN 14CO2 labeling carbon acquisition chlorophyll fluorescence crassulacean acid metabolism (CAM) Orchidaceae radioisotope 932 937 6 04/03/23 20230501 NES 230501 Orchidaceae is one of the most diverse families of flowering plants, with > 28 000 known species distributed among 763 genera (Christenhusz & Byng, [8]). Moreover, the high nocturnal C fixation by I T. aphyllum i roots comparable to that by I T. japonicum i leaves indicates sophisticated C fixation in I T. aphyllum i roots. [Extracted from the article]

[Objectives] The purpose of this study was to investigate the regulation and mechanism of hydrogen-rich water (HRW)on the growth and photosynthesis of strawberry (Fragaria×ananassa Duch.). This would benefit agriculture by the application of HRW. [Methods]HRW was used to irrigate strawberries, and parameters such as leaf growth, photosynthetic gas exchange and photosynthetic efficiency were determined. Surface water irrigation was as the control. [Results]After the treatment, the leaf area of strawberries increased, the dry weight and fresh weight of leaves increased by 57.7% and 60.4%, respectively, and the relative growth rate and net assimilation rate increased by 50.0% and 59.9%, respectively, indicating that HRW had a significant effect in promoting strawberry growth. After HRW treatment, the chlorophyll a content increased by 14.4%, the chlorophyll b content did not change significantly, and the net photosynthetic rate of leaves increased by 22.3%, the contents of soluble sugar, glucose and sucrose in leaves significantly increased. After HRW treatment, the electron transport rate of PSⅡ increased but was not significant, while the significant decrease of quantum yield of photosystems Ⅱ nonregulatory energy dissipation Y(NO)indicated that the protection and regulation ability of the PSⅡ of strawberry leaves was improved. While the electron transport rate of PSⅠ and effective photochemical quantum yield Y(I) significantly increased, suggesting that the cyclic electron flow of PSⅠ was improved. Further analysis showed that the transmembrane proton gradient(ΔpH)was significantly higher than that of the control, accounting for the main part of proton motive force, and the ATP content increased by 43.9% compared with the control, confirming the cyclic electron flow results. [Conclusions]Hydrogen-rich water can promote growth and photosynthesis of strawberry leaf by enhancing cyclic photosynthesis electron flow. [ABSTRACT FROM AUTHOR]

Perennial ryegrass is considered an excellent cold-season turfgrass, and salinity is an important environmental factor that affects its growth. Many studies have shown that arbuscular mycorrhizal (AM) fungi can alleviate stress responses in plants, but there have been few reports on the promotion of turfgrass growth in saline-alkali land by AM fungi. We designed an experiment to investigate the effects of different saline conditions (0%, 0.05%, 0.1% salt, w/w) on the growth and physiological metabolism of perennial ryegrass. The results showed that under 0.05% salt stress, AM fungi increased the plant height by 25.9%, the aboveground and underground dry weight by 37.1% and 55.6%, respectively; and the content of chlorophyll a in the plants by 31.0%. Inoculation with AM fungi increased the net photosynthetic rate (A), transpiration rate (E), intercellular CO2 concentration (Ci), and stomatal conductance (Gs) of perennial ryegrass, and the increase in their levels negatively correlated with increasing salt concentrations. Under 0.1% salt stress, the A, Ci, Gs, and E of perennial ryegrass inoculated with AM fungi increased by 24.6%, 23.2%, 139.1%, and 40.7%, respectively. However, inoculation with AM fungi reduced Fv/Fm and had no significant impacts on the SOD activity, MDA, proline (Pro) content, soluble sugar content, and soluble protein content of perennial ryegrass. In conclusion, AM fungi can promote the growth of perennial ryegrass under salt stress, enhance its photosynthetic capacity, and improve the ability of perennial ryegrass to resist salt stress. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) regulate growth in many plants. Carbohydrates provide energy and carbon skeleton for cell growth. However, how CNTs influence plant carbohydrate metabolism remains largely unknown. For a comprehensive understanding the response of carbohydrate metabolism and accumulation in leaves of crabapple (Malus hupehensis Rehd) to single-walled carbon nanotubes (SWCNTs), the expression of key enzymes and genes involved in apple sugar metabolism was investigated. In this report, TEM showed that SWCNTs particles were absorbed in apple leaf. Foliar application of 10 and 20 mg/L SWCNTs promoted chlorophyll content, net photosynthetic rate, stomatal conductance and transpiration rate. SWCNTs up-regulate the activity of aldose-6-phosphate reductase (A6PR), accompanied by increased concentration of photosynthetic assimilate‒sorbitol. However, the activities of sucrose phosphate synthase (SPS) and the accumulation of sucrose did not change significantly in SWCNTs-sprayed apple leaves compared with the control. In addition, the activities of photoassimilate degradation enzyme (sorbitol dehydrogenase, SDH; sucrose synthase, SUSY; neutral invertase, NINV) and hexose degradation enzyme (fructokinase, FRK; hexokinase, HK) were higher in SWCNTs-treated apple leaves than that in the control leaves. Quantitative real-time polymerase chain reaction (qRT‒PCR) results indicated that the expression of genes associated with sugar metabolism changed significantly after SWCNTs application. Taken together, we propose that spraying apple leaves with 10 and 20 mg/L SWCNTs can improve photosynthetic activity and accelerate carbohydrate metabolism in apple leaves. Our results provide insight into understanding the biological effects of CNTs in plants and are valuable for continued use of SWCNTs in agri-nanotechnology. • Foliar spraying of SWCNTs increases chlorophyll content and photosynthetic rate. • Foliar spraying of SWCNTs promotes the synthesis of photosynthetic assimilate. • Foliar spraying of SWCNTs up-regulates the activities of sugar degradation enzymes. [ABSTRACT FROM AUTHOR]

Water stress is one of the most important yield constraints on crop productivity for many crops, and especially for maize, worldwide. In addition, climate change creates new challenges for crop adaptation as water stress appears even in areas where, until recently, there was an adequate water supply. The objective of the present study was to determine the effect of water availability on the morphological and physiological characteristics of maize, and also on the environmental cost under field conditions. The lowest water treatment (ET50) reduced leaf area index, plant height, chlorophyll content, assimilation rate and gas exchange parameters, photosynthetic efficiency, and silage yield. Furthermore, mild water stress (ΕΤ70) affected the characteristics that were studied but maintained a high crop yield. Moreover, the outputs/inputs ratio and energy efficiency showed similar trends, with the highest values under ΕΤ100 treatment and the lowest under ΕΤ50 treatment in two consecutive years. Therefore, the results of this study can be used by farmers in the Mediterranean area, who can maintain or improve their crop yield using a lower amount of water when the water supply is limited, thereby contributing to reducing the impact of global climate change and maintaining crop productivity. [ABSTRACT FROM AUTHOR]

Improving legumes crops' performance under dense stands shade environment (e.g., intercropped oats–clover) is needed to promote agroecological practices. Previous studies have revealed that ethylene produced by plants under dense standing conditions is among other factors that affect crops' growth performance and reduce legumes' ability to fix nitrogen (N). Here, we identified a Pseudomonas thivervalensis strain T124 as a high ACC deaminase-producing bacterium and evaluated its potential ability to alleviate the effects of reduced light (RL) and exogenous ethylene applied as ACC (ethylene precursor) on clover growth and development under controlled conditions and field conditions at dense stands of clover and oats intercrops. RL decreases clover root and shoots biomass, whereas the T124 strain counteracted RL effects, enhancing clover tolerance to shade. Exogenous ACC reduced clover growth and chlorophyll content while inducing overaccumulation of reactive oxygen species (H2O2 and O2•−). ACC-elicited cellular stress was suppressed by strain T124, suggesting the role of bacterial ACC deaminase activity. Combined with Rhizobium leguminosarum strain T618 (the strain identified as being able to fix N in symbiosis with clover), T124 prevents early nodule senescence by improving nodule leghemoglobin and reducing nodule nitric oxide levels. Co-inoculation with T124 + T618 increased shoot N content (+24%) more than T618 alone. Field experiments revealed that intercropping decreases Photosynthetic Active Radiation (PAR) at the top of clover due to oats, affecting clover photosynthesis assimilation. Interestingly, under T124 inoculation treatments, clover net photosynthetic rate (Anet) and stomatal conductance (Gs) were found to improve relative to the control and T618 inoculation treatments. Clover exhibits improved growth performance in terms of branching and nodulation after T124 inoculation. Most significant improvements occurred with the mixing of the two strains. Data suggest that co-inoculation with R. leguminosarum T618 and P. thivervalensis T124 potentially decreases the interspecific competition between clover and oats intercrops by reducing ACC (ethylene precursor) levels. Our study revealed that co-inoculation of legumes with competitive rhizobia and ACC deaminase-producing PGPRs is an eco-friendly approach to improving intercropping systems' performance. [ABSTRACT FROM AUTHOR]

Although carnivorous plants can obtain organic carbon from their animal prey, they rely on photosynthetic assimilation of carbon dioxide. All investigated carnivorous plant species assimilate carbon dioxide using the C3 pathway, with the rate of photosynthesis (AN) being lower in comparison to noncarnivorous species. The reasons for low AN in carnivorous plants are (i) low nitrogen and phosphorus content in the soil and leaves and (ii) the cost of carnivory in their modified leaves (called traps). The cost of carnivory includes several anatomical, ultrastructural, and biochemical adaptations of traps, which favor nutrient uptake from prey over photosynthetic assimilation. However, after digestion, nutrient uptake from the prey can increase AN, growth, and reproduction. In carnivorous plants with active trapping mechanisms, spatiotemporal changes in AN and respiration rate (RD) occur during prey capture and digestion, owing to the interplay of electrical and hormonal signaling. Approximately 7.5% of carnivorous plants are aquatic plants, with demands for survival being different from those of terrestrial plants. The alternative mode of nutrition in carnivorous plants is reflected in their plastid genomes, which resemble the reduced plastomes of parasitic and mycoheterotrophic plants. [ABSTRACT FROM AUTHOR]

Poplar is an important fast-growing tree, and its photosynthetic capacity directly affects its vegetative growth. Stomatal density is closely related to photosynthetic capacity and growth characteristics in plants. Here, we isolated PagSTOMAGEN from the hybrid poplar (Populus alba × Populus glandulosa) clone 84K and investigated its biological function in vegetative growth. PagSTOMAGEN was expressed predominantly in young tissues and localized in the plasma membrane. Compared with wild-type 84K poplars, PagSTOMAGEN-overexpressing plants displayed an increased plant height, leaf area, internode number, basal diameter, biomass, IAA content, IPR content, and stomatal density. Higher stomatal density improved the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate in transgenic poplar. The differential expression of genes related to stomatal development showed a diverged influence of PagSTOMAGEN at different stages of stomatal development. Finally, transcriptomic analysis showed that PagSTOMAGEN affected vegetative growth by affecting the expression of photosynthesis and plant hormone-related genes (such as SAUR75, PQL2, PSBX, ERF1, GNC, GRF5, and ARF11). Taken together, our data indicate that PagSTOMAGEN could positively regulate stomatal density and increase the photosynthetic rate and plant hormone content, thereby promoting vegetative growth in poplar. Our study is of great significance for understanding the relationship between stoma, photosynthesis, and yield breeding in poplar. [ABSTRACT FROM AUTHOR]

Summary: Although stomata are typically found in greater numbers on the abaxial surface, wheat flag leaves have greater densities on the adaxial surface. We determine the impact of this less common stomatal patterning on gaseous fluxes using a novel chamber that simultaneously measures both leaf surfaces.Using a combination of differential illuminations and CO2 concentrations at each leaf surface, we found that mesophyll cells associated with the adaxial leaf surface have a higher photosynthetic capacity than those associated with the abaxial leaf surface, which is supported by an increased stomatal conductance (driven by differences in stomatal density).When vertical gas flux at the abaxial leaf surface was blocked, no compensation by adaxial stomata was observed, suggesting each surface operates independently. Similar stomatal kinetics suggested some co‐ordination between the two surfaces, but factors other than light intensity played a role in these responses.Higher photosynthetic capacity on the adaxial surface facilitates greater carbon assimilation, along with higher adaxial stomatal conductance, which would also support greater evaporative leaf cooling to maintain optimal leaf temperatures for photosynthesis. Furthermore, abaxial gas exchange contributed c. 50% to leaf photosynthesis and therefore represents an important contributor to overall leaf gas exchange. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate if electric arc furnace (EAF) slag generated during steel production could have an application as a soil enhancer in agriculture. For that purpose, a greenhouse experiment was conducted on common beans (Phaseolus vulgaris) cultivated in soil enriched with EAF slag (at 1% and 2% level), synthetic fertilizer (NPK), combined EAF slag and synthetic fertilizer, or in control (untreated) soil. The beans were exposed to test soils until maturity (for 8 weeks). Following that period, physico-chemical properties of the soils, as well as nutrient status, growth, photosynthetic and oxidative stress parameters of bean plants were determined. EAF slag improved the mineral status of the soil and significantly increased Fe, Mg, N, P and K in different bean plant organs. EAF slag and/or NPK increased plant height. EAF slag, especially at lower levels, positively affected dry weight of leaf and seed. Soil supplementation with a lower level of EAF slag, as well as with a combination of EAF slag and NPK, led to significant improvement in gas exchange parameters (net photosynthetic rate, intercellular CO2 concentration and stomatal conductance) and nitrate reductase activity, indicating a positive influence on bean plants. Potential phytotoxicity of EAF slag was not detected, as evidenced by the oxidative stress parameters. Thus, EAF slag applied at a low level shows promising potential as an efficient soil enhancer, and as a valuable source of nutrients essential to plants, with an equal or even better performance compared to synthetic fertilizer. [ABSTRACT FROM AUTHOR]

Background: Soil salinization leads to a significant decline in crop yield and quality, including licorice, an important medicinal cash crop. Studies have proofed that the application of exogenous silicon can significantly improve the ability of licorice to resist salt stress, however, few studies concentrated on the effects of foliar silicon application on the morphology, physiological characteristics, and anatomical structure of licorice leaves under salt stress. In this study, the effects of Si (K2SiO3) on the structural and physiological characteristics of Glycyrrhiza uralensis Fisch. and G. inflata Bat. leaves under different salt concentrations (medium- and high-salt) were studied. Results: Compared with the control (without salt), the plant height, total dry weight, leaf area, leaf number, relative water content, xylem area, phloem area, ratio of palisade to spongy tissue, gas exchange parameters, and photosynthetic pigment content of both licorice varieties were significantly reduced under high-salt (12S) conditions. However, the thickness of the leaf, palisade tissue, and spongy tissue increased significantly. Applying Si to the leaf surface increased the area of the vascular bundle, xylem, and parenchyma of the leaf's main vein, promoted water transportation, enhanced the relative leaf water content, and reduced the decomposition of photosynthetic pigments. These changes extended the area of photosynthesis and promoted the production and transportation of organic matter. G. uralensis had a better response to Si application than did G. inflata. Conclusions: In conclusion, foliar application of Si can improve water absorption, enhance photosynthesis, improve photosynthetic capacity and transpiration efficiency, promote growth and yield, and alleviate the adverse effects of salt stress on the leaf structure of the two kinds of licorice investigated. [ABSTRACT FROM AUTHOR]

Background: Soil salinization leads to a significant decline in crop yield and quality, including licorice, an important medicinal cash crop. Studies have proofed that the application of exogenous silicon can significantly improve the ability of licorice to resist salt stress, however, few studies concentrated on the effects of foliar silicon application on the morphology, physiological characteristics, and anatomical structure of licorice leaves under salt stress. In this study, the effects of Si (K2SiO3) on the structural and physiological characteristics of Glycyrrhiza uralensis Fisch. and G. inflata Bat. leaves under different salt concentrations (medium- and high-salt) were studied. Results: Compared with the control (without salt), the plant height, total dry weight, leaf area, leaf number, relative water content, xylem area, phloem area, ratio of palisade to spongy tissue, gas exchange parameters, and photosynthetic pigment content of both licorice varieties were significantly reduced under high-salt (12S) conditions. However, the thickness of the leaf, palisade tissue, and spongy tissue increased significantly. Applying Si to the leaf surface increased the area of the vascular bundle, xylem, and parenchyma of the leaf's main vein, promoted water transportation, enhanced the relative leaf water content, and reduced the decomposition of photosynthetic pigments. These changes extended the area of photosynthesis and promoted the production and transportation of organic matter. G. uralensis had a better response to Si application than did G. inflata. Conclusions: In conclusion, foliar application of Si can improve water absorption, enhance photosynthesis, improve photosynthetic capacity and transpiration efficiency, promote growth and yield, and alleviate the adverse effects of salt stress on the leaf structure of the two kinds of licorice investigated. [ABSTRACT FROM AUTHOR]

SUMMARY: As sessile organisms, plants must adapt their physiology and developmental processes to cope with challenging environmental circumstances, such as the ongoing elevation in atmospheric carbon dioxide (CO2) levels. Nicotinamide adenine dinucleotide (NAD+) is a cornerstone of plant metabolism and plays an essential role in redox homeostasis. Given that plants impaired in NAD metabolism and transport often display growth defects, low seed production and disturbed stomatal development/movement, we hypothesized that subcellular NAD distribution could be a candidate for plants to exploit the effects of CO2 fertilization. We report that an efficient subcellular NAD+ distribution is required for the fecundity‐promoting effects of elevated CO2 levels. Plants with reduced expression of either mitochondrial (NDT1 or NDT2) or peroxisomal (PXN) NAD+ transporter genes grown under elevated CO2 exhibited reduced total leaf area compared with the wild‐type while PXN mutants also displayed reduced leaf number. NDT2 and PXN lines grown under elevated CO2 conditions displayed reduced rosette dry weight and lower photosynthetic rates coupled with reduced stomatal conductance. Interestingly, high CO2 doubled seed production and seed weight in the wild‐type, whereas the mutants were less responsive to increases in CO2 levels during reproduction, producing far fewer seeds than the wild‐type under both CO2 conditions. These data highlight the importance of mitochondrial and peroxisomal NAD+ uptake mediated by distinct NAD transporter proteins to modulate photosynthesis and seed production under high CO2 levels. Significance Statement: The beneficial effect of elevated atmospheric CO2 on photosynthesis and seed yield requires correct intracellular NAD+ transport. [ABSTRACT FROM AUTHOR]

Grown in different regions of Brazil, mango is of great importance at the national level. However, mango cultivation is directly related to physiological factors such as photosynthesis, stomatal conductance and chlorophyll. Physiological factors are related to the nutritional balance of the plant. Among the nutrients, potassium (K) can be highlighted, which, despite not being a structural element for the plant, stimulates, or is part of several physiological plant processes. Therefore, an experiment was carried out with the purpose of evaluating, in the vegetative period of 'Palmer' mango, the effect of different sources of K to accelerate the maturation stage of mango branches and verify their influence on physiological indexes and chlorophyll. Treatments consisted of three ripeners and a control, which were applied directly to the branches and leaves of "Palmer" mango trees. The variables analyzed were chlorophyll A, B and Total indexes; Internal concentration of CO2; Stomatal conductance; transpiration rate; Net photosynthesis; Instantaneous Carboxylation Efficiency and Water Use Efficiency. After collecting, and analyzing the data, it was concluded that the vegetative period of the "Palmer" mango tree, in relation to the different evaluation dates, was not influenced by potassium sources. The use of T4 treatment (SpeedFol® induction mango) can provide a greater increment of chlorophyll A, B and Total than KCl and K2SO4. [ABSTRACT FROM AUTHOR]

The individual application of pure and active compounds such as methionine may help to address water scarcity issues without compromising the yield of wheat. As organic plant growth stimulants, amino acids are popularly used to promote the productivity of crops. However, the influence of the exogenous application of methionine in wheat remains elusive. The present investigation was planned in order to understand the impact of methionine in wheat under drought stress. Two wheat genotypes were allowed to grow with 100% field capacity (FC) up to the three-leaf stage. Twenty-five-day-old seedlings of two wheat genotypes, Galaxy-13 and Johar-16, were subjected to 40% FC, denoted as water deficit-stress (D), along with 100% FC, called control (C), with and without L-methionine (Met; 4 mM) foliar treatment. Water deficit significantly reduced shoot length, shoot fresh and dry weights, seed yield, photosynthetic, gas exchange attributes except for transpiration rate (E), and shoot mineral ions (potassium, calcium, and phosphorus) in both genotypes. A significant increase was recorded in superoxide dismutase (SOD), catalase (CAT), hydrogen peroxide (H2O2), malondialdehyde (MDA), and sodium ions (Na+) due to water deficiency. However, foliar application of Met substantially improved the studied growth, photosynthetic, and gas exchange attributes with water deficit conditions in both genotypes. The activities of SOD, POD, and CAT were further enhanced under stress with Met application. Met improved potassium (K), calcium (Ca2+), and phosphorus (P) content. In a nutshell, the foliar application of Met effectively amended water deficit stress tolerance by reducing MDA and H2O2 content under water deficit conditions in wheat plants. Thus, we are able to deduce a positive association between Met-induced improved growth attributes and drought tolerance. [ABSTRACT FROM AUTHOR]

This work aimed to evaluate the effects of lower water levels on leaf intercellular spaces and to assess their relations with the gas exchange, anatomy, and growth of Sorghum bicolor. Experiments were conducted in a greenhouse, in which plants were subjected to three water conditions (ten replicates, n = 30): well-irrigated, decreased irrigation, and limited irrigation. Lower water levels had no significant effect on the growth of S. bicolor but increased the biomass of the roots. Moreover, the number of leaves, leaf area, and leaf size as well as the chlorophyll content were not affected by lower water levels, and no significant changes were detected for whole plant photosynthesis, transpiration, or stomatal conductance. The water content of the plants and the water potential remained unchanged. However, compared with other treatments, the decreased irrigation decreased water loss and increased the water retention. Lower water levels increased the intercellular CO2 percentage, mesophyll area, and proportion of stomatal cavities and promoted minor changes in leaf tissue and stomatal traits. The increased stomatal cavities provided higher CO2 uptake and prevented excessive water loss. Thus, modifications to the intercellular spaces promoted conditions to avoid excessive water loss while concurrently improving CO2 uptake, which are important traits for drought-tolerant plants. [ABSTRACT FROM AUTHOR]

Auxins are known to regulate xylem development in plants, but their effects on water transport efficiency are poorly known. Here we used tomato plants with the diageotropica mutation (dgt), which has impaired function of a cyclophilin 1 cis – trans isomerase involved in auxin signaling, and the corresponding wild type (WT) to explore the mutation's effects on plant hydraulics and leaf gas exchange. The xylem of the dgt mutant showed a reduced hydraulically weighted vessel diameter (D h) (24–43%) and conduit number (25–58%) in petioles and stems, resulting in lower theoretical hydraulic conductivities (K t); on the other hand, no changes in root D h and K t were observed. The measured stem and leaf hydraulic conductances of the dgt mutant were lower (up to 81%), in agreement with the K t values; however, despite dgt and WT plants showing similar root D h and K t, the measured root hydraulic conductance of the dgt mutant was 75% lower. The dgt mutation increased the vein and stomatal density, which could potentially increase photosynthesis. Nevertheless, even though it had the same photosynthetic capacity as WT plants, the dgt mutant showed a photosynthetic rate c. 25% lower, coupled with a stomatal conductance reduction of 52%. These results clearly demonstrate that increases in minor vein and stomatal density only result in higher leaf gas exchange when accompanied by higher hydraulic efficiency. [ABSTRACT FROM AUTHOR]

The odd-pinnately compound leaves of short pod-branch surrounding the fruit growth of Roxburgh rose (Rosa roxburghii Tratt.) are the source organ of photosynthesis, and the photosynthetic capacity of leaves is an important factor determining the yield. To analyze the relationship between the distribution of palisade cells in different leaf positions and photosynthesis in the flowering and fruiting stage, the microstructure, photosynthetic physiology, and gas exchange parameters of each leaf position were measured. The leaves located in the middle of short pod-branches were rich in columnar cells and showed higher chlorophyll content and, thus, higher light absorption by the leaves than other leaf positions, which conducted to enhanced photosynthesis and outstanding photosynthetic capacity under sufficient light environment. Yet, the first leaf was immature, and the differentiation of mesophyll cells was not completed, which resulted in a weakening of photosynthesis per unit leaf area under adiquate light environment. The lower leaves of short pod-branches showed smaller leaf area and looser spongy mesophyll in an environment with light blocking, which resulted in insufficient photosynthetic capacity. Our findings indicate that the photosynthetic conversion ability of the middle leaf of short pod branch is the most prominent. Therefore, regulating leaf mesophyll cells distribution according to leaf position is essential for effective leaf photosynthesis at the flowering and fruit stage in Roxburgh rose. [ABSTRACT FROM AUTHOR]

Diffuse light has been shown to alter plant leaf photosynthesis, transpiration and water‐use efficiency. Despite this, the angular distribution of light for the artificial light sources used with common gas exchange systems is unknown. Here, we quantify the angular distribution of light from common gas exchange systems and demonstrate the use of an integrating sphere for manipulating those light distributions. Among three different systems, light from a 90° angle perpendicular to the leaf surface (±5.75°) was <25% of the total light reaching the leaf surface. The integrating sphere resulted in a greater range of possible distributions from predominantly direct light (i.e., >40% of light from a 90 ± 5.75° angle perpendicular to the leaf surface) to almost entirely diffuse (i.e., light from an even distribution drawn from a nearly 0° horizontal angle to a perpendicular 90° angle). The integrating sphere can thus create light environments that more closely mimic the variation in sunlight under both clear and cloudy conditions. In turn, different proportions of diffuse light increased, decreased or did not change photosynthetic rates depending on the plant species observed. This new tool should allow the scientific community to explore new and creative questions about plant function within the context of global climate change. [ABSTRACT FROM AUTHOR]

Simple Summary: The gas exchange system presented herein integrates open-flow/force ventilation, LED technology, and micropropagation to determine the impact of environmental factors (e.g., [CO2], sucrose, light intensity) on the photosynthetic capacity of cultured plantlets. This system was developed and tested on Cannabis sativa L., an emerging crop of high economic value, for which micropropagation has become an important aspect of production. Since conventional micropropagation avenues can minimize photosynthetic performance, this system offers fresh opportunities to examine the role of light signaling and photosynthesis in micropropagation to investigate and overcome in-vitro-associated morphophysiological disorders. By maintaining [CO2] at controlled levels (400 and 1200 ppm) with calibrated light intensities, photosynthetic light response curves were prepared based on net carbon exchange rates (NCERs) to paint a picture of the dynamic, combinational influences of irradiance, [CO2], and additional factors on photosynthetic performance. Additionally, NCERs were continuously monitored during a 24 h light/dark period under standard conditions to provide estimates of relative growth rates (daily C-gain). Thus, a system is presented with the ability to answer questions about the nature of in vitro plant physiology related to carbon dynamics, that would otherwise be difficult to assess. Supplemental sugar additives for plant tissue culture cause mixotrophic growth, complicating carbohydrate metabolism and photosynthetic relationships. A unique platform to test and model the photosynthetic proficiency and biomass accumulation of micropropagated plantlets was introduced and applied to Cannabis sativa L. (cannabis), an emerging crop with high economic interest. Conventional in vitro systems can hinder the photoautotrophic ability of plantlets due to low light intensity, low vapor pressure deficit, and limited CO2 availability. Though exogenous sucrose is routinely added to improve in vitro growth despite reduced photosynthetic capacity, reliance on sugar as a carbon source can also trigger negative responses that are species-dependent. By increasing photosynthetic activity in vitro, these negative consequences can likely be mitigated, facilitating the production of superior specimens with enhanced survivability. The presented methods use an open-flow/force-ventilated gas exchange system and infrared gas analysis to measure the impact of [CO2], light, and additional factors on in vitro photosynthesis. This system can be used to answer previously overlooked questions regarding the nature of in vitro plant physiology to enhance plant tissue culture and the overall understanding of in vitro processes, facilitating new research methods and idealized protocols for commercial tissue culture. [ABSTRACT FROM AUTHOR]

In order to understand the dynamic variations of photosynthetic capacity of Rhododendron to adapt to environmental factors in different seasons. Rhododendron delavayi, widely introduced and cultivated, was planted in a 2-gallon plastic basin in the open field. The dynamic variations of photosynthetic characteristics and influencing factors in different growth phases were investigated by the technique of gas exchange and chlorophyll fluorescence. The results were as follows: The growth cycle of R. delavayi were almost overlaps with photosynthetic variation at Kunming area. The variations of photosynthetic characteristics reflected the variations of growth cycle. In the net early growth period from May to July, the photosynthetic rate(Pn)increased rapidly, the stomatal conductance(Gs)was the decisive factor affecting (Pn). The relative humidity of air(RH)had a significant indirect effect on (Pn) by affecting Gs and transpiration rate(Tr). The (Pn) and growth could be stimulated by increasing RH at this phase. In the peak growth period from July to October, the RH, (Pn) and Gs of R. delavayi were high and stable. However, lower air temperature(AT)in this phase was a unique climate character in Kunming area. Low AT became an important factor affecting photosynthetic capacity at this phase, and increasing AT could improve (Pn) and promote the growth of R. delavayi. In the late growth phase after October, AT and RH decreased rapidly, stomata closed gradually, the maximum quantum efficiency of photosynthetic system Ⅱ(Fv/Fm)and (Pn) were declined. Gs and Fv/Fm were the main factors affecting photosynthesis at this stage. Our results can provide important references for the scientific cultivation and popularization of R. delavayi. [ABSTRACT FROM AUTHOR]

Salt stress is abiotic stress that directly affects the gas exchange and redox metabolism of the plants. However, some studies claim that the combination of potassium-phosphorus fertilization may increase salt tolerance in plants. In this context, the objective of this study was to evaluate gas exchange and the antioxidant enzyme activity responses to combined potassium-phosphorus fertilization in the tissues of West Indian cherry during the fructification phase, 240 days after application of treatments (DAT) in the second year of brackish water irrigation production. The treatments were distributed in randomized blocks, in a 5 × 4 factorial scheme, with five levels of irrigation water electrical conductivity – (ECw equal to 0.6 – control, 1.4; 2.2; 3.0 or 3.8 dS m−1) and four potassium-phosphorus fertilization combinations, 200/120; 170/102; 120/72 or 90/54 g K2O/P2O5 plant−1 per year, with three replicates. Irrigation water salinity impaired the gas exchange, showing a reduction of 47.94, 47.21, and 43.92% in the stomatal conductance, transpiration, and CO2 assimilation, respectively. In contrast, it increased the antioxidant metabolism, mainly the catalase enzyme activity (+ 67.7%). The average weight of fruits was increased by 85% in the combination of 90/54 under 1.4 dS m−1. Although the average number of fruits, in same combination (90/54) was 37% lower compared to high salinities. The threshold water salinity (1.12 dS m−1) indicates that West Indian cherry is a salt sensitive crop. [ABSTRACT FROM AUTHOR]

To study the light intensity suitable for Bletilla ochracea Schltr., morphology, photosynthetic parameters, and polysaccharide content of seedlings were evaluated under different light intensities. All shade treatments promoted plant growth and net photosynthetic rate while having no significant effect on transpiration rate. The maximum photochemical efficiency and potential photochemical efficiency reached the lowest values under full sunlight. The electron transport rate and photochemical quenching under shade were significantly higher than those under full light, while nonphotochemical quenching was the highest under full light. This indicated that the shade alleviated photoinhibition in summer and improved the utilization of light. B. ochracea could adapt to different light intensities, enhancing photosynthetic efficiency under low light by improving the electron transport and the degree of opened PS? reaction centers, and adapting to high light by increasing heat dissipation. Plant growth, photosynthesis, and polysaccharide accumulation of B. ochracea greatly increased under 76.4% shade. [ABSTRACT FROM AUTHOR]

Barnyard grass is one of the vicious weeds in rice field, which affects seriously the growth and development of rice and reduces the yield of rice. In order to clarify the effect of barnyard grass on rice growth and development and yield formation under the condition of elevated atmospheric carbon dioxide (CO2) concentration, the experiment was conducted with the Free-Air CO2 Enrichment system (FACE system), taking rice Jijing 88 as material. The experiment included 4 treatments: atmospheric CO2 concentration (400μmol·mol-1) without barnyard grass, rice planting and barnyard grass together with atmospheric CO2 concentration, elevated CO2 concentration (550μmol·mol-1) without barnyard grass, rice planting and barnyard grass together with elevated CO2 concentration. Physiological indicators were measured and analyzed at the tillering stage, jointing stage, heading stage, and mature stage of rice. The results showed that elevated CO2 concentration increased significantly the number of rice ears per hole and the seed setting rate, and eventually increased the rice yield. Barnyard grass significantly reduced the rice seed setting rate, and reduced rice yield ultimately. Interaction of elevated CO2 concentration and barnyard grass increased significantly thousand-grain weight of rice, yet, the interaction did not affected rice yield significantly. Elevated CO2 concentration increased significantly the dry matter of rice, and barnyard grass reduced significantly the dry matter of rice. However, the interaction of elevated CO2 concentration and the barnyard grass had no significant difference. Elevated CO2 concentration increased significantly the net photosynthetic rate of the flag leaf of rice, the concentration of intercellular CO2 of the flag leaf, and the Soil and Plant Analyzer Developrnent (SPAD) value of rice flag leaf. Barnyard grass treatment reduced significantly the net photosynthetic rate of the flag leaf of rice, the concentration of intercellular CO2 in the flag leaf, the stomatal conductance, the transpiration rate, the instantaneous water use efficiency, and the SPAD value. The interaction of elevated CO2 concentration and barnyard grass reduced the net photosynthetic rate of rice flag leaves at early stage, and increased it at later stage. In conclusion, Elevated CO2 concentration after heading stage had a greater impact on rice photosynthesis than barnyard grass on rice photosynthesis. [ABSTRACT FROM AUTHOR]

Although open-central canopy (OCC) is popular in apple (Malus ×domestica) orchards in Loess Plateau of China, its relevant photosynthetic mechanisms have not been elucidated. In this study, changes in photosynthetically active radiation (PAR), gas exchange, chlorophyll fluorescence quenching and fruit quality in apple trees were measured in OCC and compared with those in the conventional condensed round and large canopy (RLC). Results showed that light intercepted at different orientations was 44% higher by OCC than that by RLC. The improved light environment within OCC remarkably increased leaf maximum net photosynthetic rate (P nmax) and significantly decreased stomatal limitation. Under high light, the ratio of photorespiratory rate to gross photosynthetic rate (P r / P g) in OCC was higher than that in RLC. Moreover, reversible component in non-photochemical quenching (r(q E)) was increased, while irreversible component (r(q I)) was decreased in OCC than in RLC. As a result, the fruit quality in OCC was greatly boosted as evidenced by the significantly increased single fruit weight, fruit flesh firmness and fruit soluble solid contents and the sharply decreased fruit titratable acid contents. PAR intercepted by the canopy and the fruit soluble solid contents, leaf P nmax or single fruit weight were positively correlated, while PAR or P nmax was negatively correlated with the fruit titratable acid contents. Accordingly, the improved crown light environment and the enhanced leaf photosynthetic performance and photoprotective capacity in OCC led to the boosted fruit quality. [ABSTRACT FROM AUTHOR]

Knowledge of the physiological mechanisms in saline environment may boost sugarcane breeding programmes targeting abiotic stresses. Our hypothesis is that the physiology of Saccharum genotypes responds differently under salt stress. Thus, the objective of the study was to evaluate the physiological performance of Saccharum complex genotypes grown under presence and absence of saline stress. The experimental design used was randomized blocks arranged in a 32 × 2 factorial scheme (32 genotypes × 2 salinity levels). The presence of salinity provided higher mean values for photosynthetic rate in genotypes G4, G18, G22, G25 and G29 compared with the environment without salinity, with mean values (17.26, 21.49, 24.22 and 26.19 µmol CO2m−2s−1), respectively, for internal CO2 concentration in G2, G6, G9, G14, G17, G19, G23 and G29, with mean values (323.45, 399.64, 386.88, 412.14, 366.31, 250.48, 379.10 and 380.75 µmol CO2 mol air−1), respectively, for transpiration in G18, G24, G25 and G29, with mean values (5.05, 3.30, 4.39 and 4.01 mmol H2O m−2s−1), respectively, and for chlorophyll content in G3, G5, G6, G8, G10, G13, G20, G22, G23, G25, G31 and G32, with mean values (34.18, 43.01, 38.08, 32.38, 37.09, 37.18, 32.47, 38.38, 38.04, 36.95 and 33.32 SPAD units) respectively. Genotypes that under salt stress increase their physiological performance demonstrate superiority over others and should be considered in breeding programmes. Photosynthesis and transpiration is the most adequate combination for screening, but the spad index is the most viable tool because of its ease of determination and cost. [ABSTRACT FROM AUTHOR]

Cotton is often exposed to high temperatures during the reproductive stage, which can negatively affect its productivity. The objectives were to: i) test whether heat stress impacts during the reproductive stage on photosynthesis are due to instant temperature effects or to acclimation produced during the heat stress period, ii) evaluate the role of stomatal and mesophyll conductance on net photosynthetic rate and iii) identify possible interactions between heat stress and different source/sink ratios during the reproductive period. Two field experiments were carried out in 2016 (Exp. 1) and 2017 (Exp. 2). Two heating treatment periods were imposed as follows: pre‐flowering between 15 days before flower bud and flowering (H1) and post‐flowering between flowering and 15 days later (H2). Each treatment had a control group (C1 and C2, respectively). In Exp. 1, two genotypes with contrasting crop cycles were compared. In Exp. 2, 50% defoliated plants (D‐) were compared with intact plants (D+) under the same temperature treatments using one genotype. Average daily maximum temperature of heated treatments for both experiments was 37.9 ± 0.79ºC, 5.8ºC higher than the controls. Independently of the period, thermal stress had a negative impact on photosynthesis in both genotypes through an acclimation response, reducing it up to 35% compared with controls when heath‐stressed and control plants were measured at the same temperature. Instant responses to temperature were not observed. This decrease was mainly determined by mesophyll conductance, and no recovery was observed 15 days after the end of treatments. Photosynthesis depletion was conditioned by the source/sink ratio, showing a complete recovery only in defoliated plants. It is concluded that thermal stress had a negative acclimation impact on photosynthesis, without responses to changes in instant temperature, and this acclimation is modulated mainly by mesophyll conductance. [ABSTRACT FROM AUTHOR]

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is one of the most devastating diseases affecting maize yield worldwide. A foliar spray of nickel (Ni) to potentiate maize resistance against NCLB was investigated by examining alterations in the photosynthetic apparatus (leaf gas exchange and chlorophyll [Chl] a fluorescence parameters), production of ethylene and reactive oxygen species as well as activities of defence and antioxidant enzymes. Mycelial growth of E. turcicum was inhibited by Ni in vitro. Inoculated plants sprayed with Ni exhibited higher foliar Ni concentration, reduced NCLB symptoms, and lower concentrations of malondialdehyde and hydrogen peroxide. In inoculated leaves of plants not sprayed with Ni, concentrations of Chl a, Chl b, and carotenoids were lower and the photosynthetic apparatus was impaired at the biochemical level due to high NCLB severity. The activities of antioxidant enzymes were not affected by Ni, except an increase in glutathione reductase activity for noninoculated plants sprayed with Ni. High lipoxygenase and polyphenoloxidase activities, lower ethylene production, as well as elevated production of phenolics and lignin helped decrease NCLB severity in the leaves of Ni‐sprayed plants. [ABSTRACT FROM AUTHOR]

The coordination between phytohormones regulation, stomatal behaviour (stomatal index and opening/closing) and gas exchange are potent determinants of plant survival under drought stress. However, we found a knowledge gap in the mechanism regulating the fine-tuning of these features during drought. In order to address this we evaluated gas exchange, stomatal behaviour and endogenous phytohormones content in two cotton varieties (LRA-5166 and NBRI-67) differing in drought sensitivity during water deficit conditions. Variety specific differences were recorded in net photosynthesis rate (A), transpiration rate (E) and stomatal conductance (gs) with significantly less decrease in drought tolerant LRA-5166 than drought sensitive NBRI-67. The abscisic acid (ABA) accumulation was significantly increased in LRA-5166 while reduced in NBRI-67 under water deficit, which was accompanied by relatively less reduced 6-benzylaminopurine (6-BAP) level in LRA-5166 than NBRI-67. Thus, improved ABA/6-BAP ratio was observed in both the varieties of cotton. Critically, LRA-5166 has reduced stomatal index, aperture size and significantly higher A and intrinsic water use efficiency (WUEi), thus higher drought tolerance than NBRI-67. Furthermore, we found that endogenous ABA predominantly maintains the stomatal behaviour and regulates its physiology either by antagonizing 6-BAP or alone to coordinate with water deficit signals. Overall, our findings describe a new insight as to how drought modulates endogenous ABA and 6-BAP homeostasis in cotton leaf and the mechanism of stomatal regulation by ABA and 6-BAP in cotton. [ABSTRACT FROM AUTHOR]

This study investigated the effect of light intensity and signaling on the regulation of far-red (FR)-induced alteration in photosynthesis. The low (LL: 440 μmol m−2 s−1) and high (HL: 1135 μmol m−2 s−1) intensity of white light with or without FR (LLFR: 545 μmol m−2 s−1 including 115 μmol m−2 s−1; HLFR: 1254 μmol m−2 s−1 + 140 μmol m−2 s−1) was applied on the tomato cultivar (Solanum Lycopersicon cv. Moneymaker) and mutants of phytochrome A (phyA) and phytochrome B (phyB1 , and phyB2). Both light intensity and FR affected plant morphological traits, leaf biomass, and flowering time. Irrespective of genotype, flowering was delayed by LLFR and accelerated by HLFR compared to the corresponding light intensity without FR. In LLFR, a reduced energy flux through the electron transfer chain along with a reduced energy dissipation per reaction center improved the maximum quantum yield of PSII, irrespective of genotype. HLFR increased net photosynthesis and gas exchange properties in a genotype-dependent manner. FR-dependent regulation of hormones was affected by light signaling. It appeared that PHYB affected the levels of abscisic acid and salicylic acid while PHYA took part in the regulation of CK in FR-exposed plants. Overall, light intensity and signaling of FR influenced plants' photosynthesis and growth by altering electron transport, gas exchange, and changes in the level of endogenous hormones. • Both preferable absorbance of far-red by PSI and its signaling through phytochromes regulate photosynthesis process. • Regulation of hormonal homeostasis by photoreceptors signaling affect gas exchange and net photosynthesis rate. • The physiological effects of far-red on plants are dependent on the background light intensity. [ABSTRACT FROM AUTHOR]

To explore the protective mechanisms of brassinosteroids in the chill-induced photoinhibition in tomato (Solanum lycopersicum), we studied the effect of foliar sprayed 24-epibrassinolide (EBR, 0.1µM) on the gas exchange, chlorophyll fluorescence characteristics, and chlorophyll a fluorescence transient in tomato seedlings under chilling stress (a temperature of 8 °C and an irradiance of 200 µmol m-2 s-1) for 4 d. Results showed that chilling significantly inhibited CO2 assimilation and induced photoinhibition of photosystem II (PS II). However, photosystem I (PS I) was relatively tolerant to chilling stress, which was due to the downregulation of PS II activity and increase of cyclic electron transport around PS I (CEF). Chilling led to the inactivation of PS II reaction centers (RCs) and blocked the electron transport at the PS II acceptor side, but did not affect the oxygen-evolving complex (OEC) on the donor side of PS II. Exogenous EBR could alleviate chill-induced PS II photoinhibition mainly by the increase of CO2 assimilation and thermal dissipation of excitation energy in the PS II antennae, while the protective effect of CEF was relatively smaller. This study demonstrated that EBR maintained the stability of the electron transport chain and the function of PS II in chilled tomatoes. EBR promoted the absorption (ABS/CS), trapping (TRo/CS), and electron transport (ETo/CS) per leaf area in tomatoes under chilling stress, which was due to increasing the density of active reaction centers (RC/CS), rather than the activity of active RCs. [ABSTRACT FROM AUTHOR]