Leaf Water Potential Research Articles

Biofilm producing plant growth promoting bacteria in combination with glycine betaine uplift drought stress tolerance of maize plant.

The escalating threat of drought poses a significant challenge to sustainable food production and human health, as water scarcity adversely impacts various aspects of plant physiology. Maize, a cornerstone in staple cereal crops, faces the formidable challenge of drought stress that triggers a series of transformative responses in the plant. The present study was carried out in two sets of experiments. In first experiment, drought stress was applied after maintaining growth for 45 days and then irrigation was skipped, and plant samples were collected at 1st, 3rd and 6th day of drought interval for evaluation of changes in plant growth, water relation (relative water content) and antioxidants activity by inoculating indigenously isolated drought tolerant biofilm producing rhizobacterial isolates (Bacillus subtilis SRJ4, Curtobacterium citreum MJ1). In the second experiment, glycine betaine was applied as osmoregulator in addition to drought tolerant PGPR to perceive modulation in photosynthetic pigments (Chlorophyll a and b) and plant growth under varying moisture stress levels (100, 75 and 50% FC). Results of the study revealed upsurge in root and shoot length, fresh and dry biomass of root and shoot besides increasing chlorophyll contents in water stressed inoculated plants compared to uninoculated plants. Glycine betaine application resulted in an additional boost to plant growth and photosynthetic pigments, when applied in combination with bacterial inoculants. However, both bacterial inoculants behaved differently under drought stress as evident from their biochemical and physiological attributes. Isolate SRJ4 proved to be superior for its potential to express antioxidant activity, leaf water potential and relative water contents and drought responsive gene expression while isolate MJ1 showed exclusive increase in root dry biomass and plant P contents. Though it is quite difficult to isolate the bacterial isolates having both plant growth promoting traits and drought tolerance together yet, such biological resources could be an exceptional option to be applied for improving crop productivity and sustainable agriculture under abiotic stresses. By exploring the combined application of PGPR and glycine betaine, the study seeks to provide insights into potential strategies for developing sustainable agricultural practices aimed at improving crop resilience under challenging environmental conditions.

Changes in Physiological Indices, Amino Acids, and Volatile Compounds in Vitis vinifera L. cv. Pinot Noir under UV-B Radiation and Water Deficit Conditions.

UV-B radiation and water deficit can challenge Pinot noir growth and fruit quality. The aim of this work is to determine the effects of UV-B and water deficit on the physiological indices, amino acids, and volatile compounds of Pinot noir vine and fruit. The results showed that both individual and combined treatments caused a decrease in the leaf SPAD, with the largest amplitude being observed in the combined treatment. Water deficit also decreased the leaf water potential and increased the juice δ13C‱ at harvest, which was the opposite of the latter under UV-B radiation. Interestingly, most of the physiological indices under combined stresses did not show significant changes compared with that under no UV-B and the well-watered control treatment. Moreover, the concentrations of amino acids and volatile compounds in the berries were determined at harvest. The amino acid contents were significantly increased by the combined treatment, particularly proline (Pro), aspartate (Arg), alanine (Ala), and threonine (Thr). There were slight increases in volatile compounds. This research substantially contributed to improve our scientific understanding of UV-B and water deficit responses in an important commercial species. In addition, it highlighted some future research to produce high-quality wines with the anticipated specific characteristics.

Effects of Different Water Stress Levels, Heterogeneity and Location on Berry Phytochemical Properties in an Organic and Conventional Vineyard (Vitis vinifera cv. Cabernet-Sauvignon)

The research was conducted in two vineyards, one certified as organic and the other following conventional practices. The experiment, designed with Split-Plot Experimental Design based on stress levels, was divided into two main plots, Organic and Conventional, and each of these plots was further divided into two subplots. The predawn leaf water potential results categorized the vines into two groups: those with values lower than -8 MPa and those greater than -8 MPa, which were labeled as Dryland-shallow soil and Baseland-deep soil, respectively, based on the location and soil type. During the harvest, grape clusters were collected and classified into three groups based on berry diameter (10mm-12mm, 12mm-14mm, 14mm-16mm). The results indicated that the 10mm-12mm berry size group generally exhibited the desired characteristics across all evaluated criteria. The total anthocyanin and total tannin content were found to be higher in the 10mm-12mm berries from vines experiencing moderate stress (Stress 1), regardless of their location. Additionally, the Dryland-shallow soil condition showed higher tannin content. On the other hand, grapes from high-stress vines displayed lower antioxidant values. The total polyphenol index content was higher in the organic vineyard. Based on the findings, it was suggested that to obtain high phytochemical compounds from Cabernet-Sauvignon grapes in the Tekirdağ region, cultivation should be carried out under Dryland-shallow soil conditions, where the predawn leaf water potential can drop as low as -0.8 MPa during the period between veraison and harvest. Moreover, using berries with size between 10mm-12mm might be suitable for this purpose.

Cavitron extraction of xylem water suggests cryogenic extraction biases vary across species but are independent of tree water stress

AbstractCryogenic vacuum distillation (CVD) is a widely used technique for extracting plant water from stems for isotopic analysis, but concerns about potential isotopic biases have emerged. Here, we leverage the Cavitron centrifugation technique to extract xylem water and compare its isotopic signature to that of CVD‐extracted bulk stem water as well as source water. Conducted under field conditions in tropical northern Australia, our study spans seven tree species naturally experiencing a range of water stress levels. Our findings reveal a significant deuterium bias in CVD‐extracted bulk stem water when compared to xylem water (median bias −14.9‰), whereas xylem water closely aligned with source water (median offset −1.9‰). We find substantial variations in deuterium bias among the seven tree species (bias ranging from −19.3‰ to −9.1‰), but intriguingly, CVD‐induced biases were unrelated to environmental factors such as relative stem water content and predawn leaf water potential. These results imply that inter‐specific differences may be driven by anatomical traits rather than tree hydraulic functioning. Additionally, our data highlight the potential to use a site‐specific deuterium offset, based on the isotopic signature of local source water, for correcting CVD‐induced biases.

Silicon via fertigation with and without potassium application, improve physiological aspects of common beans cultivated under three water regimes in field

Frequent droughts have led to an expansion of irrigated common bean (Phaseolus vulgaris L.) cultivation areas. An effective strategy to enhance water use efficiency and optimize crop growth is the application of silicon (Si) and potassium (K). However, the interaction between Si dosage, water regimes, and plant potassium status, as well as the underlying physiological mechanisms, remains unknown. This study aimed to assess the effects of Si doses applied via fertigation under various water regimes, in the presence and absence of potassium fertilization, on gas exchange, water use efficiency, and growth of Common beans in field conditions. Two experiments were conducted, one with and one without K supply, considering that the potassium content in the soil was 6.4 mmolc dm-3 in both experiments and a replacement dose of 50 kg ha was applied in the with K treatment, with the same treatments evaluated in both potassium conditions. The treatments comprised a 3 × 4 factorial design, encompassing three water regimes: 80% (no deficit), 60% (moderate water deficit), and 40% (severe water deficit) of soil water retention capacity, and four doses of Si supplied via fertigation: 0, 4, 8, and 12 kg ha−1. Where it was evaluated, content of photosynthetic pigments, fluorescence of photosynthesis, relative water content, leaf water potential and electrolyte extravasation, dry mass of leaves, stems and total. The optimal doses of Si for fertigation application, leading to increased Si absorption in plants, varied with decreasing soil water content. The respective values were 6.6, 7.0, and 7.1 kg ha−1 for the water regimes without deficit, with moderate water deficit, and with severe water deficit. Fertigation application of Si improved plant performance, particularly under severe water deficit, regardless of potassium status. This improvement was evident in relative water content, leaf water potential, and membrane resistance, directly impacting pigment content and gas exchange rates. The physiological effects resulted in enhanced photosynthesis in water-deficient plants, mitigating dry mass production losses. This research demonstrates, for the first time in common bean, the potential of Si to enhance irrigation efficiency in areas limited by low precipitation and water scarcity.

A trade-off between leaf hydraulic efficiency and safety across three xerophytic species in response to increased rock fragment content.

Limited information is available on the variation of plant leaf hydraulic traits in relation to soil rock fragment content (RFC), particularly for xerophytes native to rocky mountain areas. In this study, we conducted a field experiment with four gradients of RFC (0, 25, 50 and 75% ν ν-1) on three different xerophytic species (Sophora davidii, Cotinus szechuanensis and Bauhinia brachycarpa). We measured predawn and midday leaf water potential (Ψleaf), leaf hydraulic conductance (Kleaf), Ψleaf induced 50% loss of Kleaf (P50), pressure-volume curve traits and leaf structure. A consistent response of hydraulic traits to increased RFC was observed in three species. Kleaf showed a decrease, whereas P50 and turgor loss point (Ψtlp) became increasingly negative with increasing RFC. Thus, a clear trade-off between hydraulic efficiency and safety was observed in the xerophytic species. In all three species, the reduction in Kleaf was associated with an increase in leaf mass per area. In S. davidii, alterations in Kleaf and P50 were driven by leaf vein density (VLA) and Ψtlp. In C. szechuanensis, Ψtlp and VLA drove the changes in Kleaf and P50, respectively. In B. brachycarpa, changes in P50 were driven by VLA, whereas changes in both Kleaf and P50 were simultaneously influenced by Ψtlp. Our findings suggest that adaptation to increased rockiness necessarily implies a trade-off between leaf hydraulic efficiency and safety in xerophytic species. Additionally, the trade-off between leaf hydraulic efficiency and safety among xerophytic species is likely to result from processes occurring in the xylem and the outside-xylem hydraulic pathways. These findings contribute to a better understanding of the survival strategies and mechanisms of xerophytes in rocky soils, and provide a theoretical basis for the persistence of xerophytic species in areas with stony substrates.

Influence of Leaf Water Potential and Defoliation Techniques on Leaf Area Characteristics in 'Merlot'/41B Grapevines

This study aimed to assess how variations in leaf water potential and different defoliation treatments influence leaf area characteristics. The research was carried out during two consecutive years (2019-2020) on 'Merlot'/41B combination grapevines cultivated in the Tekirdağ, Şarköy vineyards of Chateau Kalpak. Four distinct water stress levels (S0, S1, S2, and S3) were implemented based on measurements of leaf water potential. Additionally, defoliation treatments were applied, including Control (C), Full Window (FW), Right Window (RW), and Left Window (LW). Upon analyzing leaf characteristics, a clear trend emerged, wherein higher stress levels correlated with an increased area of primary, lateral, and total leaves per vine. Concerning leaf removal interventions, the application of FW led to a reduction in all criteria except for the total area of main leaves per vine. While FW causes a decrease in certain leaf parameters under controlled conditions, the stress-induced increase in total leaf area points to the mechanism of plasticity in grapevines and warrants further investigation under different environmental and production dynamics.

Investigating physiological effects due to artificial infections of grapevine with <i>Verticillium nonalfalfae</i>

Ailanthus altissima is among the most invasive woody species worldwide, outcompeting native trees. The fungus Verticillium nonalfalfae (VN) is promising for A. altissima biocontrol, and its effects on the host have been studied via visual assessment in a range of host species. However, little research was performed to address fungal effects on the physiological processes of non-target woody plants. We investigated the occurrence of visual and non-visually recognisable perturbations of VN infection on potted vines to evaluate the potential risks of the biocontrol pathogen on viticulture. Eighteen four-years-old Vitis vinifera (cultivar Grüner Veltliner grafted on Kober 5BB) potted plants were inoculated with VN conidial suspension of the fungus (F), while nine plants were treated with sterile water (C, control). Disease symptoms and physiological parameters were monitored throughout the experiment (seven evaluation dates), while leaf water potential, leaf mass per area (LMA) and biomass were measured at the end of the study when plant tissue was sampled for re-isolation of the fungus. In our trial, inoculations with VN induced characteristic wilting symptoms only in Ailanthus (used as side control of the inoculum), while vines remained asymptomatic, thus indicating a high degree of host specificity of VN. Limited or no impact was detected on the physiology of the non-target V. vinifera. Furthermore, the LMA and biomass measured in the two experimental groups were not different. Although fungal colonisation induced vascular discolouration in both species, the fungus could only be re-isolated from dying Ailanthus but not from vine tissue. Results suggest that V. vinifera cv Grüner Veltliner is resistant to the applied VN isolate. However, the susceptibility and physiology of additional grapevine cultivars, as well as other native woody species to VN, should be studied before promoting large-scale use of the biocontrol agent.

The Ecophysiological Response of Olive Trees under Different Fruit Loads.

Olive trees have a unique reproductive pattern marked by biennial fruiting. This study examined the repercussions of alternate fruit bearing on the water relations of olive trees and the associated ecophysiological mechanisms. The experiment spanned two consecutive years: the "ON" year, characterized by a high crop load, and the "OFF" year, marked by minimal fruit production. Key ecophysiological parameters, including sap flow, stomatal conductance, and photosynthetic rate, were monitored in both years. Pre-dawn water potential was measured using continuous stem psychrometers and the pressure chamber technique. Biochemical analyses focused on non-structural carbohydrate concentrations (starch, sucrose, and mannitol) and olive leaves' carbon-stable isotope ratio (δ13C). Results revealed a higher leaf gas exchange rate during the "ON" year, leading to an average 29.3% increase in water consumption and a 40.78% rise in the photosynthetic rate. Higher water usage during the "ON" year resulted in significantly lower (43.22% on average) leaf water potential. Sucrose and starch concentrations were also increased in the "ON" year, while there were no significant differences in mannitol concentration. Regarding the carbon-stable isotope ratio, leaves from the "OFF" year exhibited significantly higher δ13C values, suggesting a higher resistance to the CO2 pathway from the atmosphere to carboxylation sites compared to the "ON" year plants.

Conservation tillage and residue management practices in rice improves stress tolerance of succeeding vegetable pea by regulating physiological traits in Eastern Himalayas

The majority areas of valley lands in the Himalayan foothills remains fallow after the rice harvest. Recycling of plant biomass with conservation tillage may help in enhancing soil water availability, crop physiological function and productivity under moisture stress hill environments of this region. The present study focused on three tillage practices viz., no-till (NT), minimum tillage (MT) and conventional tillage (CT) and five nutrient management (NM) practices viz., 100 % NPK, 50 % NPK, 50 % NPK + in-situ residue retention (ISRR), 50 % NPK + weed biomass (WB) and 50 % NPK + green leaf manure (GLM) in rice and their residual effect on physio-biochemical properties, yield attributes and produce quality traits of succeeding pea varieties (Arkel and Prakash). Results revealed that total leaf chlorophyll content in vegetable pea varieties Arkel and Prakash was 12.0 and 11.5 % higher under no-till (NT) followed by 11.9 and 10.6 %, respectively under minimum tillage (MT) as compared to conventional tillage (CT) in rice. Similarly, application of 50 % NPK+ green leaf manure (GLM) and 50 % NPK+ weed biomass (WB) enhanced total leaf chlorophyll content in pea by 6.50–8.17 % and 3.93–5.48 % for pea varieties Arkel and Prakash, respectively. Photosynthetic rate and leaf dry weight were found 40.4 and 80.2 % higher under MT in Arkel whereas transpiration rate (E) and shoot dry matter were 33.1 and 19.3 % higher in Prakash under MT. Leaf water potential and root-to-shoot ratio were found 22.6 and 16.5 % higher in Prakash under MT and NT compared to CT respectively. Leaf temperature and stomatal conductance were 8.67 % lower and 9.8 % higher under MT in Prakash respectively as compared to CT, whereas 4.8 and 13.0 % higher under 50 % NPK +GLM and 50 % NPK+WB as compared 100 % NPK. Leaf cell viability was 22.5 and 20.1 % higher under MT whereas leaf MDA content was 29.9 and 28.3 % higher under MT in Arkel and Prakash respectively. Leaf relative water content was significantly higher to the tune of 25.7 and 22.4 % under NT compared to CT whereas leaf cell membrane integrity was 41.3 and 40.4 % higher under NT for Arkel and Prakash. Higher pod protein was noticed under MT along with 50 % NPK+GLM (13.1 %), whereas total soluble sugar was recorded highest under NT with 50 % NPK+GLM (21.1 %) in Prakash and MT with 50 % NPK+GLM (18.3 %) in Arkel. However, in both varieties, lower TSS was recorded under CT and with 50 % NPK (14.2 and 11.2 %) and the reducing sugar was maximum under the application of 50 % NPK+WB as compared to 100 % NPK alone. For both varieties of pea, green pod yield was recorded highest under MT (4.76 & 5.89 t/ha) as compared to CT (4.76 & 6.17 t/ha) and NT (4.76 & 5.55 t/ha). While 50 % NPK+WB has recorded significantly highest green pod yield of Arkel, 50 % NPK+ GLM has caused the highest yield of Prakash. PCA executed on physiological traits explained the total variability to the tune of 85.50 %, thereby extracting three PC's viz., PC 1 (62.63 %), 12.58 %) and 10.28 %, respectively. Thus, the adoption of MT in rice followed by NT in winter pea with the application of 50 % NPK+WB or 50 % NPK+GLM is promising for better physiological traits and subsequently favoring the grain yield of pea under stressful hill environments of Eastern Himalaya.

Coupling of leaf economic and hydraulic traits of desert plants of different life forms in the Ebinur Lake Basin

The functional traits of leaves and their internal trade-offs have been the focus of ecologists as a powerful basis for revealing plant physiology and function, and ecological strategies. The consistency of the coupled relationship between leaf economic traits and hydraulic traits among trees, shrubs, and herbs in similar ecological environments has seldom been systematically explored. We explored coupling in desert plants of different life forms and their response to the soil environment in two tree species (Populus euphratica Oliv. and Haloxylon ammodendron (C. A. Mey.) Bunge)), the shrub species (Nitraria tangutorum Bobrov and Halimodendron halodendron (Pall.) Dum. Cours.), and herbaceous species (Alhagi sparsifolia Shap. and Apocynum venetum L.) in the transition zone of the desert in the Ebinur Lake Basin, Xinjiang, China. Leaf and soil samples were collected to determine plant leaf economic traits, hydraulic traits, and soil factors. Regarding leaf economic traits, trees had higher in leaf mass per area and leaf thickness (LT). The leaf nitrogen and phosphorus contents were higher in shurbs than those in trees and herbs. Regarding hydraulic traits, shrubs had higher palisade parenchyma thickness (PT) and vein density (VD), whereas herbs had higher stomatal length (SL), spongy parenchyma thickness (ST), and leaf water potential (Ψ). In herbs, SL, ST, and Ψ had advantages, whereas PT/ST was the lowest. This study revealed an association between leaf economic and hydraulic traits in plants of different life forms in a similar ecological environment and provides a scientific basis for plant conservation strategies and ecosystem services value assessment and use in arid zones.

Combining PSII photochemistry and hydraulics improves predictions of photosynthesis and water use from mild to lethal drought.

Rising temperatures and increases in drought negatively impact the efficiency and sustainability of both agricultural and forest ecosystems. Although hydraulic limitations on photosynthesis have been extensively studied, a solid understanding of the links between whole plant hydraulics and photosynthetic processes at the cellular level under changing environmental conditions is still missing, hampering our predictive power for plant mortality. Here, we examined plant hydraulic traits and CO2 assimilation rate under progressive water limitation by implementing Photosystem II (PSII) dynamics with a whole plant process model (TREES). The photosynthetic responses to plant water status were parameterized based on measurements of chlorophyll a fluorescence, gas exchangeand water potential for Brassica rapa (R500) grown in a greenhouse under fully watered to lethal drought conditions. The updated model significantly improved predictions of photosynthesis, stomatal conductanceand leaf water potential. TREES with PSII knowledge predicted a larger hydraulic safety margin and a decrease in percent loss of conductivity. TREES predicted a slower decrease in leaf water potential, which agreed with measurements. Our results highlight the pressing need for incorporating PSII drought photochemistry into current process models to capture cross-scale plant water dynamics from cell to whole plant level.

Optimization of Low-Tech Protected Structure and Irrigation Regime for Cucumber Production under Hot Arid Regions of India.

Water scarcity and climate variability impede the realization of satisfactory vegetable yields in arid regions. It is imperative to delve into high-productivity and water-use-efficient protected cultivation systems for the sustained supply of vegetables in harsh arid climates. A strenuous effort was made to find suitable protected structures and levels of irrigation for greenhouse cucumber production in hot arid zones of India. In this endeavor, the effects of three low-tech passively ventilated protected structures, i.e., naturally ventilated polyhouse (NVP), insect-proof screenhouse (IPS) and shade screenhouse (SHS), as well as three levels of irrigation (100%, 80% and 60% of evapotranspiration, ET) were assessed for different morpho-physiological, yield and quality traits of the cucumber in a two-year study. Among the low-tech protected structures, NVP was found superior to IPS and SHS for cucumber performance, as evidenced by distinctly higher fruit yields (i.e., 31% and 121%, respectively) arising as a result of higher fruit number/plants and mean fruit weights under NVP. The fruit yield decreased in response to the degree of water shortage in deficit irrigation across all protected structures. However, the interaction effect of the protected structure and irrigation regime reveals that plants grown under moderate deficit (MD, 20% deficit) inside NVP could provide higher yields than those obtained under well-watered (WW, 100% of ET) conditions inside IPS or SHS. Plant growth indices such as vine length, node number/plant, and shoot dry mass were also measured higher under NVP. The greater performance of cucumber under NVP was attributed to a better plant physiological status (i.e., higher photosystem II efficiency, leaf relative water content and lower leaf water potential). The water deficit increased water productivity progressively with its severity; it remained higher in NVP, as reflected by 20% and 94% higher water productivity than those recorded in IPS and SHS, respectively, across different irrigation levels. With the exception of total soluble solids and fruit dry matter content (which were recorded higher), fruit quality parameters were reduced under water deficit conditions. The findings of this study emphasize the importance of considering suitable low-tech protected structures (i.e., NVP) and irrigation levels (i.e., normal rates for higher yields and moderate deficit (-20%) for satisfactory yields) for cucumber in hot arid regions. The results provide valuable insights for growers as well as researchers aiming to increase vegetable production under harsh climates and the water-limiting conditions of arid regions.

Effect of nitrogen reduction combined with biochar application on soda saline soil and soybean growth in black soil areas.

The combination of biochar and nitrogen (N) fertilization in agricultural salt-affected soils is an effective strategy for amending the soil and promoting production. To investigate the effect of nitrogen reduction combined with biochar application on a soda saline soil and soybean growth in black soil areas, a pot experiment was set up with two biochar application levels, 0 (B0) and 4.5 t/hm2 (B1); two biochar application depths, 0-20 cm (H1) and 0-40 cm (H2); and two nitrogen application levels, conventional nitrogen application (N0) and nitrogen reduction of 15% (N1). The results showed that the application of biochar improved the saline soil status and significantly increased soybean yield under lower nitrogen application. Moreover, increasing the depth of biochar application enhanced the effectiveness of biochar in reducing saline soil barriers to crop growth, which promoted soybean growth. Increasing the depth of biochar application increased the K+ and Ca2+ contents, soil nitrogen content, N fertilizer agronomic efficiency, leaf total nitrogen, N use efficiency, AN, Tr, gs, SPAD, leaf water potential, water content and soybean yield and its components. However, the Na+ content, SAR, ESP, Na+/K+, Ci and water use efficiency decreased with increasing biochar depth. Among the treatments with low nitrogen input and biochar, B1H1N1 resulted in the greatest soil improvement in the 0-20 cm soil layer compared with B0N0; for example, K+ content increased by 61.87%, Na+ content decreased by 44.80%, SAR decreased by 46.68%, and nitrate nitrogen increased by 26.61%. However, in the 20-40 cm soil layer, B1H2N1 had the greatest effect on improving the soil physicochemical properties, K+ content increased by 62.54%, Na+ content decreased by 29.76%, SAR decreased by 32.85%, and nitrate nitrogen content increased by 30.77%. In addition, compared with B0N0, total leaf nitrogen increased in B1H2N1 by 25.07%, N use efficiency increased by 6.7%, N fertilizer agronomic efficiency increased by 32.79%, partial factor productivity of nitrogen increased by 28.37%, gs increased by 22.10%, leaf water potential increased by 27.33% and water content increased by 6.44%. In conclusion, B1H2N1 had the greatest effect on improving the condition of saline soil; it not only effectively regulated the distribution of salt in soda saline soil and provided a low-salt environment for crop growth but also activated deep soil resources. Therefore, among all treatments investigated in this study, B1H2N1 was considered most suitable for improving the condition of soda saline soil in black soil areas and enhancing the growth of soybean plants.

DETERMINATION OF THE EFFECT OF DIFFERENT DOSES OF JASMONIC ACID APPLICATIONS ON ALLEVIATING SALT STRESS IN TOMATO PLANTS WITH PHYSIOLOGICAL PARAMETERS

Salt stress is one of the most important abiotic stress factors that limit productivity in crop production due to climate change, whose effects have been felt more clearly in the world in recent years, and incorrect applications in agricultural soils. Research in plant production in saline soils, based on alleviating the effects of stress through applications to plants or soil, has gained momentum in recent years. In our study, we aimed to demonstrate that foliar jasmonic acid application to tomato plants alleviates the effects of salt stress with physiological parameters. Two tomato genotypes, sensitive to salt stress (TOM 106) and tolerant (TOM 23), determined in previous studies on abiotic stress, were used as plant materials. These two genotype selections were chosen to determine how close jasmonic acid brings the sensitive genotype to the tolerant genotype in salt stress. Salt dose is 100 mM and Control (0mM), jasmonic acid doses are; It was applied as 0, 20, 30 and 40 μM. The experiment carried out in pots was carried out under controlled conditions. Plant growth parameters (plant fresh and dry weight, stem diameter and plant length) and physiological parameters (such as leaf water potential, leaf osmotic potential, photosynthetic rate, transpiration rate, internal CO2, stomatal conductivity, chlorophyll) were measured at regular intervals. Jasmonic acid applications created a statistically significant difference. As a result, it was determined that 20 and 30 μM jasmonic acid applications were more effective in reducing salt stress damage.

The degree of hydraulic vulnerability segmentation at the individual level is related to stomata sensitivity in seedlings of three oak species

AbstractIt is hypothesized that ‘hydraulic vulnerability segmentation’ (the vulnerability of expendable organs is higher compared to the vulnerability of nonexpendable organs) can enhance the drought‐tolerance of trees. However, prediction of positive segmentation (leaf minus branch) did not gain undisputed support in field observations. Further, the main organs of trees (leaf/trunk/root) are vital to test the hypothesis at the individual level. Unfortunately, most verifications of the hypothesis focus on the hydraulic vulnerabilities between leaves and terminal branches of mature trees. In this study, we grew three deciduous oak (Quercus mongolica, Q. variabilis and Q. aliena) seedlings (6 months old), and measured the hydraulic vulnerabilities of leaves (by rehydration method), main stems and main roots (by bench dehydration method). The sensitivity of stomata to water potential was obtained by monitoring the stomata conductance response to drought stress. The xylem anatomy of main stem and main root was also measured. It was found that the leaves of all three oak species exhibited greater vulnerability than the main stems and main roots. The leaf‐stem segmentation was more pronounced than the stem‐root one, and the stem‐root in Q. aliena even showed a reversed segmentation. Further, we found that higher stomatal sensitivity was associated with higher P50,leaf (water potential at 50% loss of leaf hydraulic conductivity), and narrower segmentation between leaf and the most embolism‐resistant organ. Collectively, our results support the ‘hydraulic vulnerability segmentation’ hypothesis at the individual level, and highlight the importance of stomatal regulation in hydraulic vulnerability segmentation.

ESTIMATING THE PHOTOSYSTEM’S EFFICIENCY, ANTIOXIDANTS ACTIVITY AND PLANT WATER RELATIONS OF TOMATO UNDER WATER DEFICIT CONDITIONS

Due to physiological repercussions, the tomato crop has decreased productivity caused by drought throughout its entire life cycle. The tomato harvest has exceeded expectations due to a worldwide water resource limitation. The objective of subjecting the tomato cultivars Flanto and Sahel, to a self-imposed drought was to investigate the interrelationships among biochemical, physiological, enzymatic, and water-related factors. Five varying levels of moisture strongly impacted all plant attributes: 100%, 80%, 60%, 40%, and 20% when subjected to drought stress. The lack of water resulted in notable improvements in some metrics. Some examples of these traits include linear electron flow (LEF), photosynthetic efficiency (PSE), inward light dissipation ratio (qP), catalase activity (CAT), ascorbate peroxidase activity (APX), and leaf water potential (LEWP). Consider, for example, the intriguing discoveries concerning photosystem II, non-photochemical quenching, chlorophyll levels, leaf osmotic potential, and leaf turgor potential.

Differentiated responses of plant water use regulation to drought in Robinia pseudoacacia plantations on the Chinese Loess Plateau

Robinia pseudoacacia plantations play an important role in improving the ecological environment of the Chinese Loess Plateau (CLP). However, drought stress is emerging as the major threat of sustainable growth in R. pseudoacacia plantations under the background of global warming and increasing water scarcity. Investigating the responses of plant water use to drought and the associated regulating mechanism in R. pseudoacacia is helpful for improving understanding of plant survival strategies and developing sustainable forest management practices under climate change. In this study, we monitored the canopy transpiration (Tr) dynamics with synchronous observations of soil water content and leaf water potentials in R. pseudoacacia plantations during two different hydrological years (2021 and 2022) at two sites featuring semihumid (Changwu) and semiarid (Mizhi) climate conditions. Results showed that normalized Tr exhibited stronger relationships with meteorological variables at the Changwu site than Mizhi site, as well as under non-drought condition compared to drought condition. The canopy stomatal conductance (Gc) decreased significantly with increasing vapor pressure deficit (VPD) and soil drought at both sites. The sensitivity of Gc to VPD revealed more strict stomatal regulation of transpiration in response to drought at the Changwu site, and less strict stomatal regulation at the Mizhi site. Relationship between midday and predawn water potentials indicated a partial isohydric strategy in response to drought, and reflected stomatal closure tends to occur more rapidly than hydraulic conductivity loss in R. pseudoacacia. These results suggest that the Tr and Gc values of R. pseudoacacia and their sensitivity to climate weakened as soil drought progresses and varied with different climatic conditions, and R. pseudoacacia exhibited flexible stomatal regulation of transpiration and water use strategies in response to drought.

Assessment of leaf water potential and stomatal conductance as early signs of stress in young hazelnut tree in Willamette valley

Corylus avellana L. is a species highly susceptible to water stresses caused by vapor pressure deficit and high temperature. Under such conditions, transpiration is strongly constrained even with good soil water availability. This is due to ineffective drought resistance mechanisms and indicates the need to identify early indicators of plant stress that are easy to measure, effective and efficient. This research explored the possibility of using stomatal conductance and leaf water potentials as early indicators of stress. For this purpose, an experiment was set up in a commercial 5-year-old Corylus avellana L. var. 'McDonald' orchard located in Willamette valley. The experimental designed featured irrigated and rainfed trees, and potential stress indicators were monitored at different times of the day in canopy sections aligned to cardinal directions.Results show that hazelnut trees rapidly reduced leaf stomatal conductance when the vapor pressure deficit increased to 2 and 2.5 kPa during the diurnal cycle in both irrigated and rainfed trees, even with good water availability. This suggests leaf stomatal conductance can be an efficient and effective early indicator of stress. In addition, results suggest that stomatal conductance should be measured on leaves on the west and north aspects of the canopy, where they showed lowest and highest values respectively. Leaf and stem water potential values increased during the measurement period and show a strong correlation, but their mean values do not show statistically significant differences between treatments. In Willamette valley conditions, stomatal conductance provided earlier indication of stress than water potential. The results obtained are of methodological importance for the future design of experimental plans.

Hydraulic properties and drought response of a tropical bamboo (Cephalostachyum pergracile)

Bamboo plants are an essential component of tropical ecosystems, yet their vulnerability to climate extremes, such as drought, is poorly understood due to limited knowledge of their hydraulic properties. Cephalostachyum pergracile, a commonly used tropical bamboo species, exhibited a substantially higher mortality rate than other co-occurring bamboos during a severe drought event in 2019, but the underlying mechanisms remain unclear. This study investigated the leaf and stem hydraulic traits related to drought responses, including leaf-stem embolism resistance (P50leaf; P50stem) estimated using optical and X-ray microtomography methods, leaf pressure–volume and water-releasing curves. Additionally, we investigated the seasonal water potentials, native embolism level (PLC) and xylem water source using stable isotope. We found that C. pergracile exhibited strong resistance to embolism, showing low P50leaf, P50stem, and turgor loss point, despite its rapid leaf water loss. Interestingly, its leaves displayed greater resistance to embolism than its stem, suggesting a lack of effective hydraulic vulnerability segmentation (HVS) to protect the stem from excessive xylem tension. During the dry season, approximately 49% of the water was absorbed from the upper 20-cm-deep soil layer. Consequently, significant diurnal variation in leaf water potentials and an increase in midday PLC from 5.87 ± 2.33% in the wet season to 12.87 ± 4.09% in the dry season were observed. In summary, this study demonstrated that the rapid leaf water loss, high reliance on surface water, and a lack of effective HVS in C. pergracile accelerated water depletion and increased xylem embolism even in the typical dry season, which may explain its high mortality rate during extreme drought events in 2019.