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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]

The microvasculature facilitates gas exchange, provides nutrients to cells, and regulates blood flow in response to stimuli. Vascular abnormalities are an indicator of pathology for various conditions, such as compromised vessel integrity in small vessel disease and angiogenesis in tumors. Traditional immunohistochemistry enables the visualization of tissue cross-sections containing exogenously labeled vasculature. Although this approach can be utilized to quantify vascular changes within small fields of view, it is not a practical way to study the vasculature on the scale of whole organs. Three-dimensional (3D) imaging presents a more appropriate method to visualize the vascular architecture in tissue. Here we describe the complete protocol that we use to characterize the vasculature of different organs in mice encompassing the methods to fluorescently label vessels, optically clear tissue, collect 3D vascular images, and quantify these vascular images with a semi-automated approach. To validate the automated segmentation of vascular images, one user manually segmented one hundred random regions of interest across different vascular images. The automated segmentation results had an average sensitivity of 83±11% and an average specificity of 91±6% when compared to manual segmentation. Applying this procedure of image analysis presents a method to reliably quantify and characterize vascular networks in a timely fashion. This procedure is also applicable to other methods of tissue clearing and vascular labels that generate 3D images of microvasculature. [ABSTRACT FROM AUTHOR]

Stomata are pores on plant aerial surfaces, each bordered by a pair of guard cells. They control gas exchange vital for plant survival. Understanding how guard cells respond to environmental signals such as atmospheric carbon dioxide (CO2) levels is not only insightful to fundamental biology but also relevant to real-world issues of crop productivity under global climate change. In the past decade, multiple important signaling elements for stomatal closure induced by elevated CO2 have been identified. Yet, there is no comprehensive understanding of high CO2-induced stomatal closure. In this work, we assemble a cellular signaling network underlying high CO2-induced stomatal closure by integrating evidence from a comprehensive literature analysis. We further construct a Boolean dynamic model of the network, which allows in silico simulation of the stomatal closure response to high CO2 in wild-type Arabidopsis thaliana plants and in cases of pharmacological or genetic manipulation of network nodes. Our model has a 91% accuracy in capturing known experimental observations. We perform network-based logical analysis and reveal a feedback core of the network, which dictates cellular decisions in closure response to high CO2. Based on these analyses, we predict and experimentally confirm that applying nitric oxide (NO) induces stomatal closure in ambient CO2 and causes hypersensitivity to elevated CO2. Moreover, we predict a negative regulatory relationship between NO and the protein phosphatase ABI2 and find experimentally that NO inhibits ABI2 phosphatase activity. The experimental validation of these model predictions demonstrates the effectiveness of network-based modeling and highlights the decision-making role of the feedback core of the network in signal transduction. We further explore the model's potential in predicting targets of signaling elements not yet connected to the CO2 network. Our combination of network science, in silico model simulation, and experimental assays demonstrates an effective interdisciplinary approach to understanding system-level biology. Stomata are pores on plant surfaces that can be opened or closed by pairs of guard cells in response to environmental signals. This study analyzes CO2-induced stomatal closure in Arabidopsis thaliana using network-based modelling and experimental validation, uncovering that feedback loops in a core signal transduction network regulate decision-making in guard cells. [ABSTRACT FROM AUTHOR]

The current investigation demonstrates that the application of MEL (0, 1, and 2 μmol L−1) mitigates the effects of Cr stress 0 (no Cr), 50 and 100 mg kg−1 on coriander (Coriandrum sativum L.) plants. Results from the present study showed that the increasing levels of Cr concentration in the soil induced a significant decrease in shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid contents, net photosynthesis, transpiration rate and stomatal conductance by 36%, 24%, 17%, 64%, 27%, 23%, 19%, 29%, 36%, 18%, 73%, 83%, and 43% respectively. Results findings also showed that the increasing Cr stress in the soil significantly (p< 0.05) decreases calcium, magnesium, iron, and phosphorus contents by 69%, 51%, 89%, and 109% respectively in the roots and decreased by 164%, 97%, 66%, and 124% respectively in the shoots. However, Cr toxicity boosted the production of reactive oxygen species (ROS) by increasing the contents of oxidative stress indicators. Although activities of various antioxidative enzymes and their specific gene expression and also the nonenzymatic antioxidants initially increased up to a Cr level of 50 μM but decreased gradually with the further increase in the Cr level of 100 μM in the medium, compared to those plants which were grown in the control treatment. Results also revealed that the soluble sugar, reducing sugar, and nonreducing sugar were decreased in plants grown under elevating Cr levels but increased the Cr accumulation in the roots and shoots of C. sativum. Although results also illustrated that the application of MEL also decreased Cr toxicity in C. sativum by increasing antioxidant capacity and their gene expression and thus improved the plant growth, photosynthetic pigments, and decrease oxidative stress in the roots and shoots of C. sativum. [ABSTRACT FROM AUTHOR]

Hops are grown mainly for the brewing market due to the rich chemical composition that gives beer aroma and bitterness. Brazil is one of the largest beer producers and consumers in the world and one of the largest hop importers. There is growing demand and interest in producing hops for domestic supply; however, as this crop originates from a temperate climate and the Northern Hemisphere, it is important to carry out research that describes the development of hops in a tropical climate to provide information on its cultivation in Brazil, as well as to determine its behavior in organic cultivation. A randomized block design was adopted, the treatments consisted of two cropping systems, conventional and organic, for Hallertau Mittelfrueh variety cultivation, with four blocks and three plants per plot. Gas exchange analyzes of plants under both cultivation systems were performed to obtain measurements of A, gs, Ci, E, WUE and A/Ci, morphometric and yield analyzes were also carried out. In comparison with the plants of the organic system, the plants of the conventional cultivation had greater photosynthetic efficiency; however, the practices adopted in the organic cultivation system provided the plants with greater productive capacity. [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]

Stomatal movement, initiated by specialized epidermal cells known as guard cells (GCs), plays a pivotal role in plant gas exchange and water use efficiency. Despite protocols existing for isolating GCs through proplasting for carrying out biochemical, physiological, and molecular studies, protocals for isolating GCs with their cell walls still intact have been lacking in the literature. In this paper, we introduce a method for the isolation of complete GCs from Vicia faba and show their membrane to remain impermeable through propidium iodide staining. This methodology enables further in-depth analyses into the cell wall composition of GCs, facilitating our understanding of structure-function relationship governing reversible actuation within cells. [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]

Concerns are repeatedly raised about possible adverse respiratory effects of wearing filtering face pieces (FFP) during physical activity. This study compared the impact of FFP type 2 (NF95) on pulmonary function, blood gas values, metabolism and discomfort during light, moderate and vigorous physical activity. Healthy adults (n = 13; 6 females, 7 males; mean 31.3, SD 5.5 years) participated in this randomized two-armed (Ergometer cycling with a FFP type 2 vs. no mask) crossover trial. Baseline cardiopulmonary exercise testing and two interventions (masked and unmasked ergometer cycling 40%, 50% and 70% VO2max, 10 min each) were separated by 48 h washout periods. Spiroergometric data (End tidal carbon dioxide partial pressure PetCO2; breathing frequency; inspiration time), blood gas analysis outcomes (capillary carbon dioxide partial pressure, pCO2) and subjective response (Breathing effort and perceived exertion) were contrasted between conditions using ANOVAs. All participants completed the crossover trial, seven started with the FFP2 condition (No adverse events or side effects). FFP2 decreased breathing frequency, prolonged inspiration time, increased perceived breathing effort and PetCO2 (p <.05). Blood pCO2 in millimetres mercury increased during exercise with 50%VO2max (mean 36.67, SD 3.19 vs. mean 38.46, SD 2.57; p <.05) and 70%VO2max (35.04, 2.84 vs. 38.17, 3.43; p <.05) but not during exercise with 40%VO2max (36.55, 2.73 vs. 38.70). Perceived exertion was not affected (p > 0.05) by mask wearing. Conclusion: Mask-induced breathing resistance decreased respiratory performance and limited pulmonary gas exchange. While FFP2 affected subjective breathing effort per se, invasive diagnostics showed that statistically significant metabolic effects are induced from moderate intensity upwards. Trial registration: DRKS-ID: DRKS00030181, Date of registration: 05/09/2022 (German Register for Clinical Trials). [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the morpho-physiological responses of tomato and bell pepper plants when specific nutrients were restricted. The study was conducted in a greenhouse under controlled environmental conditions and used hydroponic solution as the growth medium, with the nutrient solution being replaced as needed. Treatments consisted of a control treatment that included all nutrients at optimal concentrations and the suppression of magnesium (Mg), boron (B), zinc (Zn), and iron (Fe) for both tomato and bell pepper. The experimental design followed a completely randomized design, with a 2 (crops) × 5 (treatments) factorial scheme replicated four times. The results of this study showed that suppression of Fe had the most pronounced negative effect on the morphology and physiology of tomatoes and bell peppers and caused a reduction in parameters associated with gas exchange, leading to the development of interveinal chlorosis in the leaves. The suppression of Mg had the second most notable negative effects, with similar deficiency symptoms observed in the plant leaves as observed for the absence of Fe. While the suppression of B and Zn were less prominent compared to Fe and Mg, they still resulted in tissue malformation in the shoot apices and reductions in gas exchange and negatively impacted the morphological parameters evaluated. Therefore, our study provided important insights on how Mg, B, Zn, and Fe depletion affects tomato and bell pepper physiology and its impacts on tomato and bell pepper morphology. [ABSTRACT FROM AUTHOR]

Whiteflies cause significant crop losses through direct sap feeding, inducing plant physiological disorders and promoting the growth of sooty mold. Moreover, whiteflies can indirectly harm plants by transmitting plant viruses, particularly begomoviruses and criniviruses, resulting in severe viral disease epidemics. This study aimed to evaluate the physiological characteristics of susceptible and resistant soybean cultivars to B. tabaci. The experiments were conducted in a greenhouse. Eleven soybean cultivars were selected and infested with 100 adults of B. tabaci at the V3 stage. The evaluation of photosynthetic parameters, such as photosynthetic rate, leaf transpiration, stomatal conductance, and internal CO2 concentration, revealed that B. tabaci infestation influenced gas exchange in soybean plants. The photosynthetic rate was higher in cultivars AS3810 and M8349 during the V6 stage. Infestations caused alterations in photosynthetic parameters, suggesting increased energy demand to maintain photosynthetic activity. However, the response to infestation varied among the different cultivars, indicating varying levels of resistance and tolerance to the whitefly's damage. Furthermore, the infestation had a more notable impact during the vegetative phenological stage. In summary, infestation by B. tabaci has a discernible impact on the physiology of soybean plants, resulting in alterations in gas exchange parameters and water use efficiency. The reaction to infestation exhibited variations among different soybean cultivars, indicating potential differences in resistance to the pest. This study underscores the significance of assessing the physiological consequences of whitefly infestations on soybean crops. [ABSTRACT FROM AUTHOR]

Background: Salinity stress affects crop yields worldwide. Mungbean, a popular grain legume with protein-rich seeds, is glycophytic and vulnerable to saline stress. Silicon has become a key ingredient that boosts plant enzymatic antioxidant activity and osmoprotectant synthesis, promoting stress tolerance. Methods: In chloride-dominated salinity conditions of 4 and 6 dSm-1, sodium meta-silicate administration strategies were examined in salt-affected mungbean (MH421). Two application strategies were used: foliar spraying at 50 mg/l and 100 mg/l at 30 and 45 DAS and soil addition at 50 mg/kg soil as a solution during planting. The effects of these treatments were examined at 33 and 48 DAS, three days following foliar sodium meta-silicate application. Result: Salinity stress reduced dry weight, nodule counts, gas exchange characteristics and plant water relation features, although Si treatment buffered the detrimental effect to a varied amount. Best effects were obtained with 100 ppm foliar application. Lipid peroxidation and electrolyte loss increased with salinity stress, while Si reduces these losses by scavenging free radicals. Silicon supplementation lowered Na+ and increased K+ absorption. Also, Si altered photosynthetic machinery, Na+/K+ homeostasis, osmolyte synthesis and oxidative stress in mungbean to reduce salinity stress and increase seed yield. [ABSTRACT FROM AUTHOR]

Summary: Stomata are epidermal pores that facilitate plant gas exchange. Grasses have fast stomatal movements, likely due to their dumbbell‐shaped guard cells and lateral subsidiary cells. Subsidiary cells reciprocally exchange water and ions with guard cells. However, the relative contribution of subsidiary cells during stomatal closure is unresolved.We compared stomatal gas exchange and stomatal aperture dynamics in wild‐type and pan1, pan2, and pan1;pan2 Zea mays (L.) (maize) mutants, which have varying percentages of aberrantly formed subsidiary cells. Stomata with 1 or 2 defective subsidiary cells cannot close properly, indicating that subsidiary cells are essential for stomatal function.Even though the percentage of aberrant stomata is similar in pan1 and pan2, pan2 showed a more severe defect in stomatal closure. In pan1, only stomata with abnormal subsidiary cells fail to close normally. In pan2, all stomata have stomatal closure defects, indicating that PAN2 has an additional role in stomatal closure.Maize Pan2 is orthologous to Arabidopsis GUARD CELL HYDROGEN PEROXIDE‐RESISANT1 (GHR1), which is also required for stomatal closure. PAN2 acts downstream of Ca2+ in maize to promote stomatal closure. This is in contrast to GHR1, which acts upstream of Ca2+, and suggests the pathways could be differently wired. [ABSTRACT FROM AUTHOR]

Penstemons are a diverse group of flowering plants valued for their ability to enhance the visual appearance of urban landscapes. Penstemon barbatus (Cav.) Roth 'Novapenblu' (rock candy blueVR penstemon) and Penstemon strictus Benth 'Rocky Mountain' (rocky mountain beardtongue) are widely used in landscapes, but their tolerance to soil salinity remains poorly understood. This study aimed to investigate the effects of salinity levels at electrical conductivities (ECs) of 1.0 (nutrient solution), 2.5, 5.0, 7.5, and 10.0 dS·m21 on two penstemons (P. barbatus and P. strictus). Penstemons were irrigated with nutrient or saline solution for 8 weeks and various growth and physiological data were recorded before harvest. Salinity stress degraded the visual quality of penstemon species and led to a reduction in the growth rate and biomass production. Leaf burn and necrosis were observed in penstemons because of salinity stress. The visual score of P. barbatus and P. strictus decreased with increasing EC levels in the saline solution. When irrigated with saline solution at an EC of 7.5 dS·m21, Penstemon barbatus and P. strictus had severe-to-moderate foliar salt damage with average visual scores of 1.7 and 2.5, respectively (0 5 dead plant; 5 5 excellent plant without any foliar damage). The two penstemon species had severe foliar salt damage or were dead when irrigated with saline solution at an EC of 10.0 dS·m21. There were 87% and 92% decreases in the leaf area of P. barbatus and P. strictus, respectively, when irrigated with saline solution at an EC of 10.0 dS·m21 compared with those in the control. Although not statistically significant, there were 7% to 18% decreases in shoot dry weight of P. barbatus when irrigated with saline solutions at ECs of 2.5 to 10.0 dS·m21 compared with control. However, P. strictus displayed declines of 13% to 31% in shoot dry weight as the salinity levels of the irrigation solution increased. As the salinity levels increased, the net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration (E) rates decreased. Furthermore, sodium (Na+) and chloride (Cl2) contents of P. barbatus and P. strictus increased with the increase in salinity levels of the treatment solution. Consequently, P. barbatus and P. strictus demonstrated sensitivity to salinity stress at ECs of 7.5 and 10.0 dS·m21. This study provides important insights for their effective utilization in landscaping practices within saline-prone areas. [ABSTRACT FROM AUTHOR]

To clarify the physiological mechanism of different groundwater depths affecting soybean evapotranspiration, photosynthetic characteristics and yield, a field experiment with four groundwater depth levels (1 m (D1), 2 m (D2), 3 m (D3) and 4 m (D4)) was conducted through the groundwater simulation system in 2021 and 2022. In this study, a quantitative analysis was conducted on the groundwater recharge and irrigation water demand and evapotranspiration (ET) of soybean fields with different treatments, and the effects of different treatments on soybean leaf area index (LAI), chlorophyll content index (SPAD), intercepted photosynthetic active radiation (IPAR), photosynthetic gas exchange parameters, dry matter accumulation (DMA) and yield were explored. The results showed the following: (1) Groundwater depth affected soybean ET and the source of ET. With the increase in groundwater depth, groundwater recharge and its contribution to ET gradually decreased, but the amount of irrigation required gradually increased, resulting in the ET as D1 > D4 > D2 > D3. (2) Soybean LAI, SPAD and IPAR were significantly affected by the different groundwater depths, of which the D1 treatment always maintained the maximum, followed by the D4 treatment, and the D3 treatment was the minimum. The photosynthetic gas exchange parameters under different treatments changed synergistically, showing significant differences in the flowering and podding stages, notably D1 > D4 > D2 > D3. Soybean DMA and yield first decreased and then increased with the increase in groundwater depth, and the average DMA and yield under the D1 treatment increased by 27.71%, 46.80% and 22.82% and 20.29%, 29.91% and 12.83% in the two years, respectively, compared to the D2, D3 and D4 treatments. (3) The structural equation model demonstrated that the groundwater depth indirectly affected the growth of soybean leaf area by affecting groundwater recharge, which in turn regulated soybean ET and photosynthetic capacity and ultimately affected DMA and yield. The above results showed that in the case of shallow groundwater depth (D1), the largest groundwater recharge promoted the growth of soybean leaf area and chlorophyll synthesis and increased the absorption and utilization of solar radiation. And it improved the leaf stomata conditions, accelerated the gas exchange between the plant and atmosphere, enhanced the photosynthetic production capacity and ET and achieved maximum DMA and yield. Soybean leaf growth and photosynthesis diminish with the increase in groundwater depth. In the case of deep groundwater depth (D4), the maximum irrigation improved the growth and photosynthetic performance of soybean leaves, which was favorable to ET, and ultimately led to increases in DMA and yield. [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]

Crops are constantly threatened by salinity. Nitric oxide (NO) is an attenuating agent for salt stress; however, the specific roles of NO in gas exchange and lettuce production are not well established. The objective of this study was to evaluate the application of different concentrations of sodium nitroprusside (SNP) as an agent to mitigate salt stress in lettuce plants. Lettuce seedlings in pots were subjected to irrigation without and with saline water (0.2 and 3.5 dS m−1) and applications of different concentrations (0, 50, 100, 150, and 200 µM) of SNP, a NO donor. Saline stress negatively affected lettuce development with a reduction of 29.5% in leaf area, 6.3% in relative water content in the leaf, 17.2% in stem diameter, and 10.7% in dry matter mass in the control, but the application of SNP mitigated the deleterious effects of salt stress. Concentrations between 100 and 150 µM of SNP improved the photosynthetic metabolism of lettuce under salinity, with an increase of 46.7% in CO2 assimilation and 42.3% in fresh matter mass. Pearson's correlation showed that fresh matter correlated positively with CO2 assimilation. Therefore, SNP can be used to mitigate salt stress in lettuce. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated dose-responses of the cannabis plant to supply of macronutrients. However, further development of precision nutrition requires a high-resolution understanding of temporal trends of plant requirements for nutrients throughout the developmental progression, which is currently not available. As plant function changes during development, temporal information on nutrient uptake should be considered in relation to gradients in developmental-related physiological activity. Therefore, the present study investigated tempo-developmental trends of nutritional demands in cannabis plants, and in relation to physiological performance. Three cultivars differing in phenotype and chemotype were analyzed to evaluate genotypic variability. The results demonstrate that nutrient acquisition and deposition rates change dramatically during plant development. Uptake of individual minerals generally increased with the progression of both vegetative and reproductive development and the increase in plant biomass, while the deposition rates into the plant demonstrated nutrient specificity. The average concentrations of N, P, and K in the shoots of the different cultivars were 2.33, 4.90, and 3.32 times higher, respectively, at the termination of the reproductive growth phase, compared to the termination of the vegetative growth phase. Surprisingly, the uptake of Ca was very limited during the second part of the reproductive growth phase for two cultivars, revealing a decrease in Ca demand at this late developmental stage. Root-to-shoot translocation of most nutrients, including P, K, Mg, Mn, and Zn, as well as Na, is higher during the reproductive than the vegetative growth phase, and Fe, Mn, Zn, Cu, and Na displayed very little root-to-shoot translocation. The physiological characteristics of the plants, including gas exchange parameters, membrane leakage, osmotic potential, and water use efficiency, changed over time between the vegetative and the reproductive phases and with plant maturation, demonstrating a plant-age effect. The revealed tempo-developmental changes in nutritional requirements of the cannabis plant are a powerful tool required for development of a nutritional protocol for an optimal ionome. [ABSTRACT FROM AUTHOR]

Simple Summary: Intrapartum mortality reaches high figures in piglets, and it has been seen that those born with low weight and those with low or failed vitality scores are the most prone. Caffeine is used to reduce cardiorespiratory problems in neonates, both humans and animals. For this reason, the decision was made to use different doses of caffeine in newborn piglets in this study, to define if its oral administration would help reduce this problem and what would be the optimal dose and time of administration. The following blood gas parameters were evaluated: pH, pO2, pCO2, HCO3, Ca++, glucose, and lactate, as well as superficial and rectal temperature at 1 h, 6 h, and 24 h after birth. It was concluded that the optimal dose of caffeine to improve the vitality score and reduce possible cardiorespiratory problems is 30 mg/kg orally. Intrapartum asphyxia, fetal hypoxia, and their consequences (e.g., acidosis, hypercapnia, hypoglycemia, and hypothermia) are the main factors related to physio-metabolic imbalances that increase neonatal mortality in piglets, particularly in piglets with low birthweight and low vitality scores. This study aimed to evaluate the effect of three different doses of caffeine (10, 20, and 30 mg/kg) administered orally to 480 newborn piglets with low birthweight and low vitality scores. Blood gas parameters (pH, pO2, pCO2, and HCO3−), physio-metabolic profile (Ca++, glucose, and lactate), and the thermal response assessed through infrared thermography in four thermal windows (ocular, auricular, snout, and hindlimb) and rectal temperature were evaluated during the first 24 h of life. Doses of 30 mg/kg resulted in significant differences at 24 h for all evaluated parameters, suggesting that caffeine administration improved the cardiorespiratory function and metabolic activity of piglets by reducing acidosis, restoring glycemia, and increasing surface and rectal temperature. In conclusion, caffeine at 30 mg/kg could be suggested as an appropriate dose to use in piglets with low birthweight and low vitality scores. Future research might need to study the presentation of adverse effects due to higher caffeine concentrations. [ABSTRACT FROM AUTHOR]

Numerous vital signs are reported in association with stress response assessment, but their application varies widely. This work provides an overview over methods for stress induction and strain assessment, and presents a multimodal experimental study to identify the most important vital signs for effective assessment of the response to acute mental stress. We induced acute mental stress in 65 healthy participants with the Mannheim Multicomponent Stress Test and acquired self-assessment measures (Likert scale, Self-Assessment Manikin), salivary α-amylase and cortisol concentrations as well as 60 vital signs from biosignals, such as heart rate variability parameters, QT variability parameters, skin conductance level, and breath rate. By means of statistical testing and a self-optimizing logistic regression, we identified the most important biosignal vital signs. Fifteen biosignal vital signs related to ventricular repolarization variability, blood pressure, skin conductance, and respiration showed significant results. The logistic regression converged with QT variability index, left ventricular work index, earlobe pulse arrival time, skin conductance level, rise time and number of skin conductance responses, breath rate, and breath rate variability (F1 = 0.82). Self-assessment measures indicated successful stress induction. α-amylase and cortisol showed effect sizes of -0.78 and 0.55, respectively. In summary, the hypothalamic-pituitary-adrenocortical axis and sympathetic nervous system were successfully activated. Our findings facilitate a coherent and integrative understanding of the assessment of the stress response and help to align applications and future research concerning acute mental stress. [ABSTRACT FROM AUTHOR]

Forest species have their growth and metabolism affected, when they are exposed to conditions of water stress and one of the factors that contribute to water scarcity is climate change that increases over time. The objective of this work was to evaluate changes in gas exchange, carbon metabolism and biomass of Clusia grandiflora subjected to water deficit and evaluation periods. The experiment was carried out in a completely randomized design, in a 2 × 5 factorial scheme, with five replications, each as specified: two water conditions (control and water deficit) and five evaluation periods (0, 7, 14, 21 and 28 days). The variables related to gas exchange, carbon metabolism and biomass were evaluated. The design of the experiment was completely randomized. The relative water content did not differ between the control plants and those submitted to water deficit. While stem diameter, adventitious root length, adventitious root diameter and stem dry mass decreased, when plants were exposed to water deficit. The number of leaves, stem height, leaf area and fallen leaves reduced from day 14, in plants submitted to water deficit. There was a reduction in the hydraulic conductivity and in the water potential of the xylem in the leaf from day 7 on in plants under water deficit. Among the biochemical variables, starch and sucrose concentrations increased in plants under water stress from day 14 onwards. Water deficit negatively affected gas exchange, carbon metabolism and Clusia grandiflora biomass. [ABSTRACT FROM AUTHOR]

In Arabidopsis thaliana, stomata are composed of two guard cells that control the aperture of a central pore to facilitate gas exchange between the plant and its environment, which is particularly important during photosynthesis. Although leaves are the primary photosynthetic organs of flowering plants, floral organs are also photosynthetically active. In the Brassicaceae, evidence suggests that silique photosynthesis is important for optimal seed oil content. A group of transcription factors containing MADS DNA binding domains is necessary and sufficient to confer floral organ identity. Elegant models, such as the ABCE model of flower development and the floral quartet model, have been instrumental in describing the molecular mechanisms by which these floral organ identity proteins govern flower development. However, we lack a complete understanding of how the floral organ identity genes interact with the underlying leaf development program. Here, we show that the MADS domain transcription factor AGAMOUS (AG) represses stomatal development on the gynoecial valves, so that maturation of stomatal complexes coincides with fertilization. We present evidence that this regulation by AG is mediated by direct transcriptional repression of a master regulator of the stomatal lineage, MUTE, and show data that suggests this interaction is conserved among several members of the Brassicaceae. This work extends our understanding of the mechanisms underlying floral organ formation and provides a framework to decipher the mechanisms that control floral organ photosynthesis. Author summary: Photosynthesis supports the growth and development of plants and is mainly associated with leaves. However, other organs, including floral organs, are photosynthetic and contribute to the energy requirements of the plant, which has attracted the interest of crop breeders. Despite its importance, very little is known about the establishment and molecular regulation of floral organ photosynthesis. Here, we describe the developmental progression and regulation of stomatal formation on the female reproductive organs of Arabidopsis thaliana before and after fertilization. Stomata control gas exchange between the plant and the environment, which facilitates photosynthesis and transpiration. We show that stomatal formation coincides with fertilization of the flower but does not depend upon it. Instead, the activity of a master regulator of stomatal development is directly controlled by a flower-specific factor. We present evidence that this regulation is conserved in several members of the mustard plant family (Brassicaceae) and suggest that the timing of stomatal formation on the female reproductive organs may be modified between species, which may have adaptive benefits. Given that floral organs are derived from leaves, this work also broadens and deepens our understanding of how the underlying leaf developmental program is rewired during flower development. [ABSTRACT FROM AUTHOR]

Background: Si can be important for the growth, functioning, and stoichiometric regulation of nutrients for high-Si-accumulating bamboo. However, other trees do not actively take up dissolved silicic acid [Si(OH)4] from the soil, likely because they have fewer or no specific Si transporters in their roots. It is unclear what causes differential growth and C:N:P stoichiometry between bamboo and other trees across levels of Si supply. Results: Si supply increased the relative growth rate of height and basal diameter of bamboo saplings, likely by increasing its net photosynthetic rate and ratios of N:P. Moreover, a high concentration of Si supply decreased the ratio of C:Si in bamboo leaves due to a partial substitution of C with Si in organic compounds. We also found that there was a positive correlation between leaf Si concentration and its transpiration rate in tree saplings. Conclusions: We demonstrated that Si supply can decrease the ratio of C:Si in bamboo leaves and increase the ratio of N:P without altering nutrient status or the N:P ratio of tree saplings. Our findings provide experimental data to assess the different responses between bamboo and other trees in terms of growth, photosynthesis, and C:N:P stoichiometry. These results have implications for assessing the growth and competition between high-Si-accumulating bamboo and other plants when Si availability is altered in ecosystems during bamboo expansion. Highlights: (1) Silicon (Si) supply improved the relative growth rate of height and basal diameter of bamboo saplings, which was in contrast to our findings for other tree saplings. (2) Si supply altered the photosynthetic gas exchange properties of plants, which in turn altered Si absorption from soil via passively uptake controlled by leaf transpiration. (3) The ratio of C:Si for all tissues in bamboo was much lower than other tree saplings. Specifically, Si supply decreased the ratio of C:Si in bamboo leaves due to a partial substitution of organic C compounds by Si. [ABSTRACT FROM AUTHOR]

Drought timing determines the degree to which dry events impact ecosystems, with the ability of key processes to withstand change differing between drought periods. Findings indicate that drought timing effects vary across ecosystems, with few studies focusing on alpine grasslands. We conducted a mesocosm experiment using small grassland monoliths collected in September from the high Alps and left to overwinter at 0 °C until the experiment began in lowland Italy under late-winter outdoor conditions. Together with watered controls, we imposed three different drought treatments (zero precipitation): (1) one-month early-drought immediately after simulated snowmelt; (2) one-month mid-drought a month after melt-out; and (3) continuous two-month drought across the entire experimental period. Ecosystem responses were assessed by measuring CO2 fluxes, while vegetation responses were investigated by measuring aboveground net primary production (ANPP) of graminoids and forbs and post-harvest resprouting after one-month rehydration. We found that ecosystem respiration and gross ecosystem production (GEP) during the day were more negatively affected by mid-season drought compared to drought starting early in the season. By the end of treatments, GEP reduction under mid-season drought was similar to that of a continuous two-month drought. ANPP reduction was similar in early- and mid-drought treatments, showing a greater decrease under an enforced two-month period without precipitation. Plant resprouting, however, was only reduced in full- and mid-season drought pots, with forbs more negatively affected than graminoids. Seasonal soil moisture variation can account for these patterns: remaining winter moisture allowed almost full canopy development during the first month of the season, despite precipitation being withheld, while soil moisture depletion in the second month, resulting from higher temperatures and greater biomass, caused a collapse of gas exchange and diminished plant resprouting. Our data illustrates the importance of the timing of zero-precipitation periods for both plant and ecosystem responses in alpine grasslands. [ABSTRACT FROM AUTHOR]

Summary: Recently, we reported estimates of anaplerotic carbon flux through the oxidative pentose phosphate pathway (OPPP) in chloroplasts into the Calvin–Benson cycle. These estimates were based on intramolecular hydrogen isotope analysis of sunflower leaf starch. However, the isotope method is believed to underestimate the actual flux at low atmospheric CO2 concentration (Ca).Since the OPPP releases CO2 and reduces NADP+, it can be expected to affect leaf gas exchange under both rubisco‐ and RuBP‐regeneration‐limited conditions. Therefore, we expanded Farquhar‐von Caemmerer–Berry models to account for OPPP metabolism. Based on model parameterisation with values from the literature, we estimated OPPP‐related effects on leaf carbon and energy metabolism in the sunflowers analysed previously.We found that flux through the plastidial OPPP increases both above and below Ca ≈ 450 ppm (the condition the plants were acclimated to). This is qualitatively consistent with our previous isotope‐based estimates, yet gas‐exchange‐based estimates are larger at low Ca.We discuss our results in relation to regulatory properties of the plastidial and cytosolic OPPP, the proposed variability of CO2 mesophyll conductance, and the contribution of day respiration to the A/Ci curve drop at high Ca. Furthermore, we critically examine the models and parameterisation and derive recommendations for follow‐up studies. [ABSTRACT FROM AUTHOR]

Summary: Protein phosphorylation is a major molecular switch involved in the regulation of stomatal opening and closure. Previous research defined interaction between MAP kinase 12 and Raf‐like kinase HT1 as a required step for stomatal movements caused by changes in CO2 concentration. However, whether MPK12 kinase activity is required for regulation of CO2‐induced stomatal responses warrants in‐depth investigation.We apply genetic, biochemical, and structural modeling approaches to examining the noncatalytic role of MPK12 in guard cell CO2 signaling that relies on allosteric inhibition of HT1.We show that CO2/HCO3−‐enhanced MPK12 interaction with HT1 is independent of its kinase activity. By analyzing gas exchange of plant lines expressing various kinase‐dead and constitutively active versions of MPK12 in a plant line where MPK12 is deleted, we confirmed that CO2‐dependent stomatal responses rely on MPK12's ability to bind to HT1, but not its kinase activity. We also demonstrate that purified MPK12 and HT1 proteins form a heterodimer in the presence of CO2/HCO3− and present structural modeling that explains the MPK12:HT1 interaction interface.These data add to the model that MPK12 kinase‐activity‐independent interaction with HT1 functions as a molecular switch by which guard cells sense changes in atmospheric CO2 concentration. [ABSTRACT FROM AUTHOR]

Predictable trait variation across environments suggests shared adaptive responses via repeated genetic evolution, phenotypic plasticity or both. Matching of trait–environment associations at phylogenetic and individual scales implies consistency between these processes. Alternatively, mismatch implies that evolutionary divergence has changed the rules of trait–environment covariation. Here we tested whether species adaptation alters elevational variation in blood traits. We measured blood for 1217 Andean hummingbirds of 77 species across a 4600‐m elevational gradient. Unexpectedly, elevational variation in haemoglobin concentration ([Hb]) was scale independent, suggesting that physics of gas exchange, rather than species differences, determines responses to changing oxygen pressure. However, mechanisms of [Hb] adjustment did show signals of species adaptation: Species at either low or high elevations adjusted cell size, whereas species at mid‐elevations adjusted cell number. This elevational variation in red blood cell number versus size suggests that genetic adaptation to high altitude has changed how these traits respond to shifts in oxygen availability. [ABSTRACT FROM AUTHOR]

Salinity stress is a serious abiotic stress that negatively affect the crop growth and development. Mineral nutrient supplementation is considered as an effective strategy to mitigate the adverse effects of salinity. Nitrogen (N) is an important nutrient needed for plants and its application also an effective strategy to mitigate adverse impacts of salinity. Salinity stress disturbs plant physiological, and biochemical functions, antioxidant activities, cellular membranes, antioxidant activities and nutrient uptake thereby cause significant reduction in plant growth and development. The application of N maintains membrane stability, plant water relations, leaf gas exchange characteristics, and protect the plants from oxidative damages which induce the salt tolerance in plants. Besides, this N also improves nutrient uptake and it also induce cellular signaling that mitigate the adverse impacts of salinity. Therefore, it is interesting to understand the role of N in inducing salt tolerance in plants. In present review the mechanisms of N uptake and assimilation in plants under saline conditions are discussed. The present review provides information on how N mitigates ionic toxicity, and oxidative damages and maintains nutrient balance to counter the toxic effects of salinity stress in plants. This review will help the readers to learning more about the role of N in inducing salt tolerance 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]

Bamboo is nutritionally significant across the world because the shoots are high in calories and nutritional fiber but low in cholesterol. However, recent research has shown that bamboo shoots also contain a substantial quantity of heavy metals, including arsenic (As). Therefore, we explored whether the co-application of iron oxide nanoparticles (IONPs) and selenium nanoparticles (Se-NPs) would attenuate As toxicity in bamboo plants (Pleioblastus pygmaeus). A greenhouse experiment was performed to investigate plant responses to arsenic toxicity. Bamboo plants exposed to four levels of As (0, 10, 20, and 40 mg L−1) were foliar-sprayed with 60 mg L−1 of Se-NPs and 60 mg L−1 of IONPs alone and in combination. The data indicated that different As concentrations (10, 20, and 40 mg L−1) caused membrane damage and reactive oxide species (ROS) production in bamboo cells, characterized by H2O2, O2•−, MDA, and EL increasing by up to 47%, 54%, 57%, and 65%, respectively, in comparison with a control. The co-application of 60 mg L−1 of Se-NPs + IONP markedly improved the antioxidant enzyme activities (by 75% in SOD, 27% in POD, 52% in CAT, 37% in GR, and 38% in PAL), total flavonoid content (42%), phenolic content (36%), proline (44%), nitric oxide (59%), putrescine (Put) (85%), spermidine (Spd) (53%), relative water content (RWC) (36%), photosynthetic characteristics (27%) in net photosynthesis (Pn) (24% in the intercellular CO2 concentration (Ci), 39% in stomatal conductance (Gs), and 31% in chlorophyll pigments), and ultimately biomass indices and growth. The co-application of Se-NPs + IONPs with 10 and 20 mg L−1 of As raised the TI by 14% and 9% in the shoot and by 18% and 14% in the root, respectively. IONPs and Se-NPs reduced ROS, cell membrane lipoperoxidation, and electrolyte leakage, all contributing to the decrease in oxidative stress by limiting As uptake and translocation. In sum, Se-NPs and IONPs improved bamboo endurance, yet the most effective approach for increasing bamboo's ability to recover from As toxicity was the concurrent use of 60 mg L−1 of Se-NPs and 60 mg L−1 of IONPs. Our IONP and Se-NP data from single and combined applications offer novel knowledge in improving the tolerance mechanism against As exposure in Pleioblastus pygmaeus. [ABSTRACT FROM AUTHOR]

Stomata are pores found in the epidermis of stems or leaves that modulate both plant gas exchange and water/nutrient uptake. The development and function of plant stomata are regulated by a diverse range of environmental cues. However, how carbohydrate status in preexisting leaves might determine systemic stomatal formation within newly developing leaves has remained obscure. The glucose (Glc) sensor HEXOKINASE1 (HXK1) has been reported to decrease the stability of an ethylene/Glc signaling transcriptional regulator, EIN3 (ETHYLENE INSENSITIVE3). EIN3 in turn directly represses the expression of SUC2 (sucrose transporter 2), encoding a master transporter of sucrose (Suc). Further, KIN10, a nuclear regulator involved in energy homeostasis, has been reported to repress the transcription factor SPCH (SPEECHLESS), a master regulator of stomatal development. Here, we demonstrate that the Glc status of preexisting leaves determines systemic stomatal development within newly developing leaves by the HXK1--¦EIN3--¦SUC2 module. Further, increasing Glc levels in preexisting leaves results in a HXK1-dependent decrease of EIN3 and increase of SUC2, triggering the perception, amplification and relay of HXK1-dependent Glc signaling and thereby triggering Suc transport from mature to newly developing leaves. The HXK1--¦EIN3--¦SUC2 molecular module thereby drives systemic Suc transport from preexisting leaves to newly developing leaves. Subsequently, increasing Suc levels within newly developing leaves promotes stomatal formation through the established KIN10→SPCH module. Our findings thus show how a carbohydrate signal in preexisting leaves is sensed, amplified and relayed to determine the extent of systemic stomatal development within newly developing leaves. [ABSTRACT FROM AUTHOR]

As organs of photosynthesis, leaves are of vital importance for plants and a source of inspiration for biomimetic developments. Leaves are composed of interconnected functional elements that evolved in concert under high selective pressure, directed toward strategies for improving productivity with limited resources. In this paper, selected basic components of the leaf are described together with biomimetic examples derived from them. The epidermis (the "skin" of leaves) protects the leaf from uncontrolled desiccation and carries functional surface structures such as wax crystals and hairs. The epidermis is pierced by micropore apparatuses, stomata, which allow for regulated gas exchange. Photosynthesis takes place in the internal leaf tissue, while the venation system supplies the leaf with water and nutrients and exports the products of photosynthesis. Identifying the selective forces as well as functional limitations of the single components requires understanding the leaf as an integrated system that was shaped by evolution to maximize carbon gain from limited resource availability. These economic aspects of leaf function manifest themselves as trade-off solutions. Biomimetics is expected to benefit from a more holistic perspective on adaptive strategies and functional contexts of leaf structures. [ABSTRACT FROM AUTHOR]

Competitive interactions drive critical ecological processes in plant communities. Yet, how competitive interactions are influenced by polyploidy that has a widespread incidence in plants remains largely unknown.To evaluate the hypothesis of competitive asymmetry between polyploids and diploids, we competed tetraploid and diploid plants of perennial herbaceous Chrysanthemum indicum L. (Asteraceae) at different relative frequencies under contrasting soil water contents. We quantified the interaction intensity between competing plants of the same (intraploidy) and different ploidy levels (interploidy), and measured functional traits related to gas exchange and plant water use to understand the underlying mechanisms.The stronger competitive effect of tetraploids on diploids than that of diploids on tetraploids provided evidence for the competitive asymmetry. As a stronger competitor, tetraploids were limited more by individuals of their own than by diploids. Such competitive asymmetry was not only maintained under reduced soil water content, but also translated into higher above‐ground biomass of tetraploids. Tetraploids showed more resource‐acquisitive traits than diploids under high soil water content and more resource‐conservative traits under reduced soil water content. As such, the higher trait plasticity in tetraploids than diploids likely explained the competitive asymmetry.Synthesis. These results elucidate the nature and magnitude of species interactions between polyploid and diploid plants under changing environments and the underlying mechanisms, and provide important insights into the prevalence and persistence of polyploid plants under a changing climate. [ABSTRACT FROM AUTHOR]

In some forest systems, stomata have also been observed to reopen rapidly on recovery from drought, with delays in gas exchange recovery only observed once embolism-induced declines in hydraulic conductance occur ([29]). (B) When relief from a drought occurs after embolism has formed in the xylem then gas exchange recovery can take many months in species that must construct new xylem and organs to regain pre-drought gas exchange capacity ([3], [1]). [2] report that on rewatering from a drought severe enough to close stomata, the complete recovery of leaf gas exchange took >7 days, yet water potentials recovered within 12 h of rewatering. [Extracted from the article]

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]

Native plants are of great value in landscape maintenance. Despite their importance in the landscape, the salt tolerance of most native plants has received little attention. The present research was designed to assess morphological, physiological, and biochemical responses of four Utah-native plants [Arctostaphylos uva-ursi (kinnikinnick), Cercocarpus ledifolius (curl-leaf mountain mahogany), Cercocarpus montanus 'Coy' (alder-leaf mountain mahogany), and Shepherdia ×utahensis 'Torrey' (hybrid buffaloberry)] at different salinity levels. Each species was irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m21 (control) or saline solutions at ECs of 5.0 or 10.0 dS·m21 for 8 weeks. The experiment was a randomized complete block design with 10 replications. At 8 weeks after the initiation of the experiment, A. uva-ursi and C. montanus 'Coy' had slight foliar salt damage with an average visual score of 3.7 (0 5 dead, 5 5 excellent with no sign of foliar salt damage) when irrigated with saline solution at an EC of 5.0 dS·m21 and were dead at an EC of 10.0 dS·m21. Similarly, C. ledifolius had an average visual score of 3.2 when irrigated with saline solution at an EC of 10.0 dS·m21. However, almost no foliar salt damage was observed on S. ×utahensis 'Torrey' during the experimental period. In addition, the shoot dry weight of all species was reduced with elevated salinity levels in the irrigation water. Salinity stress also reduced gas exchange rates of plants and affected their mineral content. Proline accumulated in the leaves of native plants but was species-dependent. In conclusion, S. ×utahensis 'Torrey' was tolerant to salinity stress followed by C. ledifolius; A. uva-ursi and C. montanus 'Coy' were sensitive to salinity stress. [ABSTRACT FROM AUTHOR]

Plant susceptibility to salt depends on several factors from its genetic makeup to modifiable physiological and biochemical status. We used lemongrass (Cymbopogon flexuosus) plants as a relevant medicinal and aromatic cash crop to assess the potential benefits of chitosan oligomers (COS) on plant growth and essential oil productivity during salinity stress (160 and 240 mM NaCl). Five foliar sprays of 120 mg L−1 of COS were applied weekly. Several aspects of photosynthesis, gas exchange, cellular defence, and essential oil productivity of lemongrass were traced. The obtained data indicated that 120 mg L−1 COS alleviated photosynthetic constraints and raised the enzymatic antioxidant defence including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities that minimised salt-induced oxidative damage. Further, stomatal conductance (gs) and photosynthetic CO2 assimilation (A) were improved to support overall plant development. The same treatment increased geraniol dehydrogenase (GeDH) activity and lemongrass essential oil production. COS-induced salt resilience suggests that COS could become a useful biotechnological tool in reclaiming saline soil for improved crop productivity, especially when such soil is unfit for leading food crops. Considering its additional economic value in the essential oil industry, we propose COS-treated lemongrass as an excellent alternative crop for saline lands. [ABSTRACT FROM AUTHOR]

Senescence vividly marks the onset of the final stages of the life of a leaf, yet the triggers and drivers of this process are still not fully understood. The hormone abscisic acid (ABA) is an important regulator of leaf senescence in model herbs, but the function of this hormone has not been widely tested in deciduous trees. Here we investigate the importance of ABA as a driver of leaf senescence in winter deciduous trees. In four diverse species we tracked leaf gas exchange, water potential, chlorophyll content, and leaf ABA levels from the end of summer until leaves were abscised or died. We found that no change in ABA levels occurred at the onset of chlorophyll decline or throughout the duration of leaf senescence. To test whether ABA could enhance leaf senescence, we girdled branches to disrupt ABA export in the phloem. Girdling increased leaf ABA levels in two of the species, and this increase triggered an accelerated rate of chlorophyll decline in these species. We conclude that an increase in ABA level may augment leaf senescence in winter deciduous species but that it is not essential for this annual process. [ABSTRACT FROM AUTHOR]

Summary: We present a robust estimation of the CO2 concentration at the surface of photosynthetic mesophyll cells (cw), applicable under reasonable assumptions of assimilation distribution within the leaf. We used Capsicum annuum, Helianthus annuus and Gossypium hirsutumas model plants for our experiments.We introduce calculations to estimate cw using independent adaxial and abaxial gas exchange measurements, and accounting for the mesophyll airspace resistances.The cw was lower than adaxial and abaxial estimated intercellular CO2 concentrations (ci). Differences between cw and the ci of each surface were usually larger than 10 μmol mol−1. Differences between adaxial and abaxial ci ranged from a few μmol mol−1 to almost 50 μmol mol−1, where the largest differences were found at high air saturation deficits (ASD). Differences between adaxial and abaxial ci and the ci estimated by mixing both fluxes ranged from −30 to +20 μmol mol−1, where the largest differences were found under high ASD or high ambient CO2 concentrations.Accounting for cw improves the information that can be extracted from gas exchange experiments, allowing a more detailed description of the CO2 and water vapor gradients within the leaf. [ABSTRACT FROM AUTHOR]

To explore the effects of ultraviolet light supplementation on the photosynthetic characteristics and content of secondary metabolites in the leaves of Eucommia ulmoides Oliver (E. ulmoides), the effects of supplementary UV-B (sUV-B) radiation on the medicinally active components of E. ulmoides were comprehensively evaluated. In our study, we selected leaves of five-year-old E. ulmoides seedlings as experimental materials and studied the effect of supplemental ultraviolet-B (sUV-B) radiation on growth, photosynthetic parameters, photosynthetic pigments, fluorescence parameters, and secondary metabolites of E. ulmoides using multivariate analysis. The results showed that the leaf area and the number of branches increased after sUV-B radiation, which indicated that sUV-B radiation was beneficial to the growth of E. ulmoides. The contents of chlorophyll a and chlorophyll b increased by 2.25% and 4.25%, respectively; the net photosynthetic rate increased by 5.17%; the transpiration rate decreased by 35.32%; the actual photosynthetic efficiency increased by 10.64%; the content of the secondary metabolite genipin increased by 12.9%; and the content of chlorogenic acid increased by 75.03%. To identify the genes that may be related to the effects of sUV-B radiation on the growth and development of E. ulmoides leaves and important secondary metabolites, six cDNA libraries were prepared from natural sunlight radiation and sUV-B radiation in E. ulmoides leaves. Comparative analysis of both transcriptome databases revealed a total of 3698 differential expression genes (DEGs), including 1826 up-regulated and 1872 down-regulated genes. According to the KOG database, the up-regulated unigenes were mainly involved in signal transduction mechanisms [T] and cell wall/membrane biogenesis [M]. It is also involved in plant hormone signal transduction and phenylpropanoid biosynthesis metabolic pathways by the KEGG pathway, which might further affect the physiological indices and the content of chlorogenic acid, a secondary metabolite of E. ulmoides. Furthermore, 10 candidate unigenes were randomly selected to examine gene expression using qRT-PCR, and the six libraries exhibited differential expression and were identical to those obtained by sequencing. Thus, the data in this study were helpful in clarifying the reasons for leaf growth after sUV-B radiation. And it was beneficial to improve the active components and utilization rate of E. ulmoides after sUV-B radiation. [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]

Among-species variation in sap pH affects the xylem CO2 transport potential in trees Keywords: carbon cycling; forest carbon budget; Henry's law; pH; sap extraction; xylem CO2 transport EN carbon cycling forest carbon budget Henry's law pH sap extraction xylem CO2 transport 926 931 6 04/03/23 20230501 NES 230501 Introduction To understand the responses of forest carbon (C) cycling to environmental change, it is important to attribute the observed C release to the correct respiratory sources. Seasonal patterns of xylem sap pH, xylem abscisic acid concentration, leaf water potential and stomatal conductance of six evergreen and deciduous Australian savanna tree species. Thus, the previous observations suggest that xylem pH varies over a broad enough range to matter for the CO SB 2 sb transport rates but do not directly address the question of whether different tree species operate at different xylem pH when exposed to similar conditions. [Extracted from the article]

Increased soil salinization is among the main factors that limits safe rice production. Arbuscular mycorrhizal fungi (AMF) have been shown to alleviate the toxic effects of salt stress in plants. However, more studies on AMF combined with other functional microorganisms are needed to further improve salt tolerance in rice. Therefore, the compound inoculum Funneliformis mosseae (Fm) together with two functional microorganisms, Piriformospora indica (Pi) and Agrobacterium rhizogenes (Ar) was evaluated for their effect on the rice growth, photosynthetic gas exchange parameters, ion homeostasis, and the expression of salt tolerance-related genes under 0, 80, 120 and 160 mM salt stress conditions. The results showed that: (1) the rice seedling biomass of the AMF compound inoculant treatment group was significantly higher than that of the non-inoculation treatment group (P < 0.05); (2) under NaCl stress, inoculation with AMF compound inoculants can activate the rice antioxidant enzyme system and improve osmoregulation ability; (3) AMF compound inoculants can increase the concentration of K+ in the plant and inhibit the transfer of Na+ to rice leaves, maintaining a high K+/Na+; and (4) AMF compound inoculants could induce and regulate the overexpression of genes related to salt tolerance, photosynthesis and ion homeostasis in rice, and improve the tolerance of rice under salt stress. Our study showed that AMF compound inoculants could improve the adaptability of rice under NaCl stress and promote plant growth by regulating the photosynthetic gas exchange parameter, reactive oxygen species (ROS) scavenging ability, and ion homeostasis of plants. These results suggest that AMF compound inoculants may play an important role in improving rice productivity in salinized soil. [ABSTRACT FROM AUTHOR]

Salinity is a major challenge for agricultural productivity, adversely affecting crop growth and yield. In recent years, various techniques have been developed to increase crop tolerance to salinity, including seed priming. This study was carried out to assess the effects of salicylic acid (SA) priming (0-, 10- and 20-mM) in comparison with hydropriming on growth, physio-biochemical activities, and yield of two wheat varieties (AARI-11 and Ujala-15) under 0- and 170-mM sodium chloride (NaCl) toxicity. The exposure of wheat plants to NaCl led to a significant reduction in various growth factors, including fresh weight (40%), total chlorophyll (39%), stomatal conductance (42%), shoot Ca2+ (39%), and 1000-grain weight (34%). In contrast, salt stress triggered the activities of POD, SOD, CAT, glycine-betaine, phenolics, and proline. The application of 20 mM SA through seed priming was found to greatly improve the fresh root weight, chlorophyll b, POD activities, shoot Ca2+, and overall yield (up to 71, 66, 35, 57, and 44%, respectively) under salt stress. While hydropriming also enhanced wheat tolerance to salinity. [ABSTRACT FROM AUTHOR]

Climate change is a major concern to people all over the world. Most studies have considered singular or dual effects of climate change implications on plant growth and development; however, the combination of multiple factors has received little attention. We therefore studied the single and combined effects of two environmental stress factors (high temperature and water stresses) and abscisic acid on tomato seedlings (Solanum lycoperscum L.). Plants were grown in controlled environment growth chambers under two temperatures (22/18 °C or 28/24 °C; 16 h light/8 h dark), two watering regimes (well-watered or water-stressed), and two abscisic acid treatments (0 and 100 µL of 1mM abscisic acid solution, every other day). Plants were placed under experimental conditions for a total of 33 days, including a 13-day period of initial growth and hardening. Morphological, biochemical, and physiological parameters were measured to assess the growth and development of plants in response to the three factors. ANOVA and Scheffé's multiple-comparison procedures were used to establish significant differences among treatments and among the three factors being manipulated. All three factors decreased plant height and growth rate. Dry mass accumulation was negatively affected by high temperatures. Transpiration, stomatal conductance, and gas exchange parameters were negatively affected by all three factors; additionally, net carbon dioxide assimilation was reduced by water stress and abscisic acid application. Non-photochemical quenching was decreased in plants grown under higher temperature and in abscisic acid-treated plants. Though it was not significant, abscisic acid appears to mitigate the negative effect of higher temperature and water stress on the nitrogen balance index and total chlorophyll content. [ABSTRACT FROM AUTHOR]

Soil salinity is one of the basic factors causing physiological, biochemical and epigenetic changes in plants. The negative effects of salt in the soil environment can be reduced by foliar application of silicon (Si). The study showed some positive effects of Si on maize plants (Zea mays L.) grown in various salinity conditions. At high soil salinity (300 and 400 mM NaCl), higher CCI content was demonstrated following the application of 0.2 and 0.3% Si. Chlorophyll fluorescence parameters (PI, FV/F0, Fv/Fm and RC/ABS) were higher after spraying at 0.3 and 0.4% Si, and plant gas exchange (Ci, PN, gs, E) was higher after spraying from 0.1 to 0.4% Si. Soil salinity determined by the level of chlorophyll a and b, and carotenoid pigments caused the accumulation of free proline in plant leaves. To detect changes in DNA methylation under salt stress and in combination with Si treatment of maize plants, the methylation-sensitive amplified polymorphism (MSAP) technique was used. The overall DNA methylation level within the 3′CCGG 5′ sequence varied among groups of plants differentially treated. Results obtained indicated alterations of DNA methylation in plants as a response to salt stress, and the effects of NaCl + Si were dose-dependent. These changes may suggest mechanisms for plant adaptation under salt stress. [ABSTRACT FROM AUTHOR]