Adverse Effects Of Water Stress Research Articles

Effects of Salicylic Acid on Physiological Responses of Pepper Plants Pre-Subjected to Drought under Rehydration Conditions.

Capsicum annuum L. has worldwide distribution, but drought has limited its production. There is a lack of research to better understand how this species copes with drought stress, whether it is reversible, and the effects of mitigating agents such as salicylic acid (SA). Therefore, this study aimed to understand the mechanisms of action of SA and rehydration on the physiology of pepper plants grown under drought conditions. The factorial scheme adopted was 3 × 4, with three water regimes (irrigation, drought, and rehydration) and four SA concentrations, namely: 0 (control), 0.5, 1, and 1.5 mM. This study evaluated leaf water percentage, water potential of shoots, chlorophylls (a and b), carotenoids, stomatal conductance, chlorophyll a fluorescence, and hydrogen peroxide (H2O2) concentration at different times of day, water conditions (irrigation, drought, and rehydration), and SA applications (without the addition of a regulator (0) and with the addition of SA at concentrations equal to 0.5, 1, and 1.5 mM). In general, exogenous SA application increased stomatal conductance (gs) responses and modified the fluorescence parameters (ΦPSII, qP, ETR, NPQ, D, and E) of sweet pepper plants subjected to drought followed by rehydration. It was found that the use of SA, especially at concentrations of 1 mM in combination with rehydration, modulates gs, which is reflected in a higher electron transport rate. This, along with the production of photosynthetic pigments, suggests that H2O2 did not cause membrane damage, thereby mitigating the water deficit in pepper plants. Plants under drought conditions and rehydration with foliar SA application at concentrations of 1 mM demonstrated protection against damage resulting from water stress. Focusing on sustainable productivity, foliar SA application of 1 mM could be recommended as a technique to overcome the adverse effects of water stress on pepper plants cultivated in arid and semi-arid regions.

Phosphorus fertilisation differentially affects morpho-physiological traits and yield in soybean exposed to water stress

Abstract Background and aims Soybean plants frequently encounter challenges such as phosphorus (P) deficiency and water stress in many regions. However, the mechanisms governing low P and water stress tolerance in soybeans at different growth stages remain unclear. This study investigates the effect of P availability and water stress on soybean growth, morpho-physiological traits, and seed yield. Methods We conducted experiments using the soybean genotype (PI 561271) grown under two P levels (10 or 60 mg P kg−1 dry soil) with three watering conditions: well-watered (WW), early water stress (EWS) and terminal water stress (TWS). Plant assessments occurred at the vegetative, flowering, seed formation, and maturity stages. Results Water stress decreased leaf area, shoot and root dry weights, root length, photosynthetic rate, stomatal conductance, total carboxylates, water use, water use efficiency, shoot, root and seed P contents, seed nitrogen contents, and seed yield compared to WW at the corresponding P level and growth stage. P60 significantly increased all parameters except P use efficiency (PUE) under all water treatments. EWS plants supplemented with P60 exhibited the highest root dry weight, root length and total carboxylates. Notably, flowering and seed formation stages had the highest carboxylate proportions (oxalic, malic, malonic and citric acids) under WW and EWS at P60. P10 had significantly higher PUE than P60, irrespective of water treatments during flowering and seed formation, while the opposite trend occurred at the maturity stage. Seed protein content significantly varied between P treatments regardless of the water stress. Conclusions Our findings underscore the adverse impacts of combined low P and water stress on soybean growth, morpho-physiological traits, seed yield and protein content. Moreover, increased P availability alleviated the adverse effects of water stress, highlighting the importance of adequate P fertilisation for soybean resilience to water stress.

Impacts of cobalt and zinc on improving peanuts nutrient uptake, yield and irrigation water use efficiency under different irrigation levels

The knowledge of proper fertigation across various irrigation levels is necessary for maximizing peanut yield and irrigation use efficiency in arid areas, and it also can effectively alleviate the risk of nutrient deficiency induced by water stress. This study evaluated the effectiveness of cobalt combined with two zinc application methods on peanut nutrient uptake, yield, and irrigation water use efficiency across varying irrigation levels. A split-split plot experiment was carried out in 2021 and 2022. Three peanut gross water requirement (GWR) levels (100%, 80%, and 60%) were designated for main plots. Subplots featured plants treated with either 0 or 7.5 mg L−1 of cobalt. The sub-sub plots assessed chelated zinc effects at rates of 0 and 2 g L−1 via foliar and soil applications. In comparison to the control (100% GWR), nutrient uptake decreased, with sodium being the exception, and there was an increase in soil pH at 60% GWR. The results showed also significant reductions in yield and water use by approximately 60.3% and 38.1%, respectively. At this irrigation level, applying zinc via soil, either alone or combined with cobalt, led to significant yield increases of 89.7% and 191.3% relative to the control. Also, it’s crucial to note that cobalt application negatively affected iron and copper at 60% GWR, but this impact was lessened with soil-applied zinc. Hence, under a similar circumstance, treating stressed peanut plants with additional foliar applications of iron + copper and applying zinc via soil, could enhance nutrient uptake and improve yield. On the other hand, at 80% GWR, a combination of foliar-applied zinc and cobalt, had a tremendous impact on the absorption of (nitrogen, phosphorus, magnesium, and zinc), resulting in enhanced agronomic traits and decreased water losses. Additionally, at this irrigation level, foliar zinc application alone yielded a 32.4% increase compared to the 80% GWR control. When combined with cobalt, there was a 70.0% surge in water use. Based on this knowledge, the study suggests using 80% GWR and treating peanut plants with a combination of foliar-applied zinc and cobalt. This strategy aids plants in countering the adverse effects of water stress, ultimately leading to enhanced yield and irrigation water use efficiency.

Water Deficit Diagnosis of Winter Wheat Based on Thermal Infrared Imaging

Field experiments were conducted to analyze the effectiveness of the crop stress index (CWSI) obtained by infrared thermal imaging to indicate crop water status, and to determine the appropriate CWSI threshold range for wheat at different growth stages. The results showed that the sensitivity of plant physiological parameters to soil water was different at different growth stages. The sensitivity of stomatal conductance (Gs) and transpiration rate (Tr) to soil water was higher than that of leaf relative water content (LRWC) and photosynthetic rate (Pn). The characteristics of plant physiology and biomass (yield) at each growth stage showed that the plant production would not suffer from drought stress as long as the soil water content (SWC) was maintained above 57.0% of the field water capacity (FWC) during the jointing stage, 63.0% of the FWC during the flowering stage and 60.0% of the FWC during the filling stage. Correlation analysis showed that the correlation of CWSI with Gs, Tr and Pn was lower than that with LRWC and SWC at the jointing stage. CWSI was extremely significantly negatively correlated with SWC and LRWC (p < 0.01), but significantly negatively correlated with Gs, Tr and Pn (p < 0.05). At the flowering stage, CWSI was extremely significantly negatively correlated with all physiological and soil parameters (p < 0.01). The regression analysis showed that the CWSI of winter wheat was correlated with biomass (grain yield) in a curvilinear relationship at each growth stage. When the CWSI increased to a certain extent, the biomass and yield showed a decreasing trend with the increase in CWSI. Comprehensive analysis of all indexes showed that CWSI can be used as a decision-making index to guide the water-saving irrigation of winter wheat, as long as the CWSI threshold of plants was maintained at 0.26–0.38 during the jointing stage, 0.27–0.32 during the flowering stage and 0.30–0.36 during the filling stage, which could not only avoid the adverse effects of water stress on crop production, but also achieve the purpose of water saving.

Adapting Almond Production to Climate Change through Deficit Irrigation and Foliar Kaolin Application in a Mediterranean Climate

Irrigation is the best strategy to reduce the adverse effects of water stress on almond trees [Prunus dulcis (Mill) D.A. Web] and improve their productivity. However, in the current context of climatic change, in which the amount of water available for irrigation is increasingly limited, deficit irrigation (DI) strategies have become essential in the almond orchards of southern Europe. Other practices, such as the foliar application of reflective compounds, are being implemented. A three-year experiment (2019–2021) was set in a factorial design in which the effect of regulated deficit irrigation and foliar kaolin spray was evaluated on physiological (predawn leaf water potential, relative water content, leaf area, leaf gas exchange, and chlorophyll fluorescence) and agronomic parameters (yield, yield components, and water use efficiency (WUE)). The treatments include full irrigation (FI), which received 100% of ETc (crop evapotranspiration) during all irrigation seasons; regulated deficit irrigation (RDI), which received 100% of ETc until the kernel-filling stage, reducing the application to 35% ETc during the kernel-filling stage until harvest; and both irrigation regimes combined with kaolin application and two cultivars, Constantí and Vairo. More negative water potential values were observed in the RDI treatments compared to the FI treatments. There were no significant differences in the stomatal conductance, photosynthetic rate, or transpiration rate between treatments with RDI and FI, demonstrating the almond tree’s good adaptation to irrigation reduction in the kernel-filling stage. The two cultivars had different responses in cumulative yield throughout the three years of the trial. The cv. Constantí did not present significant differences between the FI and RDI treatments, translating into improved WUE. In contrast, the cv. Vairo suffered a reduction in accumulated performance in the RDI treatments with respect to the FI. The foliar application of kaolin did not present differences in yield and very few in the physiological activity of the almond trees. With the results obtained, we can suggest that under the conditions of our experiment, the combination of RDI and the kaolin foliar application can help save irrigation water and produce almonds more sustainably.

Inoculating moldavian balm (Dracocephalum moldavica L.) with mycorrhizal fungi and bacteria may mitigate the adverse effects of water stress

Plant growth-promoting bacteria (PGPBs) play a crucial role in mitigating the oxidative damage caused by water stress in different plant species. The aim of this study was to determine the effects of PGPBs and mycorrhiza-like fungi (Piriformospora indica) on improving drought tolerance in moldavian balm (Dracocephalum moldavica L.), a medicinal and aromatic plant. For this purpose, a greenhouse study was conducted in a factorial experiment based on a randomized complete design with three replications. Results indicate that water stress reduces the membrane stability index (MSI), total chlorophyll content (Chlt), carotenoids, and maximum photochemical efficiency of photosystem II (Fv′/Fm′) in moldavian balm plants, while increasing superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) content compared to the control (no water stress). Inoculation with PGPBs and Piriformospora indica helped alleviate the negative effects of water stress. The highest MSI (48%) and Fv′/Fm′ value (0.82) were observed when inoculated with Enterobacter and Piriformospora, respectively, under non-water-stressed conditions. Inoculation with Agrobacterium, Piriformospora, and Enterobacter improved the Chlt and leaf proline contents, as well as the SOD activity under high water stress, compared to the non-inoculated control values. Furthermore, inoculation with Pseudomonas under high water deficit stress levels increased the MDA content (0.51 mmol g−1 FW) and H2O2 levels (0.40 mmol g−1 FW). The highest yield of flowering branches (2.414 g pot−1) in moldavian balm was obtained with Enterobacter. Based on the enhanced physiological and biochemical responses, as well as increased antioxidant enzyme activity that improve water tolerance in this plant, it is recommended to use PGPBs and Piriformospora indica fertilization.

The Effects of Seed Pretreatment with Endophytic Bacteria Bacillus subtilis on the Water Balance of Spring and Winter Wheat Seedlings under Short-Time Water Deficit.

We investigated the effect of pre-sowing seed treatment with endophytic Bacillus subtilis 10-4 (B. subtilis) on spring and winter wheat (Triticum aestivum L.; cultivars Ekada-70 (Ek) and Scepter (Sc), respectively) growth and tolerance under 1-24 h of drought stress, modulated by 12% polyethylene glycol 6000 (PEG). The results showed that drought decreased transpiration intensity (TI), root relative water content (RWC), osmotic potential (Ψπ) of cell sap, and induced proline accumulation and electrolyte leakage (EL) in both wheat cultivars. It was revealed that Sc was more responsive to PEG and B. subtilis treatments than Ek. Under drought, Ek did not significantly change root length, shoot height, or dry biomass. The pretreatment of wheat plants with B. subtilis performed significantly better under drought conditions through the enhanced TI, RWC, and Ψπ of the cell sap in comparison with the plants treated with 12% PEG alone. B. subtilis also reduced stress-caused EL, especially in the Sc cultivar. Under water deficit wheat seedlings, pretreated with B. subtilis, have a higher proline accumulation in comparison to untreated stressed plants. Taken together, our results demonstrate the crucial role of endophytic B. subtilis in ameliorating the adverse effects of water stress on the water balance of both winter and spring wheat cultivars.

Effects of Zeowine and compost on leaf functionality and berry composition in Sangiovese grapevines

AbstractMeteorological extremes such as heatwaves and water limitations during the ripening season could negatively impact vine ecophysiology and berry metabolism resulting in lower yield per vine. This project aimed to compare two different soil managements during two growing-production seasons (2021 and 2022) with respect to control without any treatment (control). The two managements were: Zeowine (30 t/ha; a soil conditioner made with clinoptilolite and compost proceeding of industrial wine-waste) and compost (20 t/ha). The trial was organized at Col d'Orcia Estate (Montalcino, Tuscan wine region, Italy). The purpose was twofold: (1) to evaluate the effects of Zeowine treatments on leaf gas exchanges, midday stem water potential, chlorophyll fluorescence and leaf temperature (ecophysiology); and (2) to determine any repercussions on the quality of the grapes (technological and phenolics analyses). The parameters plant yield, yeast assimilable nitrogen, fractionation of anthocyanins (cyanidin, delphinidin, malvidin, peonidin and petunidin), caffeic acid, coumaric acid, gallic acid, ferulic acid, kaempferol and quercetin were also analysed. Zeowine showed higher photosynthesis, less negative midday water potential and lower leaf temperature. Essentially, no significant difference was found between the compost and the control. Furthermore, Zeowine grapevines showed higher anthocyanin accumulation and less quercetin content. In general, compost applied together with zeolite could alleviate the adverse effects of water stress and improve plant growth, yield and quality. The control management strategy proved to be the least beneficial for the well-being of the plant and the final quality of the product, confirming the need for amendments in critical years.

Impact of Combined Glutathione and Zn Application for Seed Priming in Ameliorating the Adverse Effects of Water Stress on Maize Seed Germination Attributes, Metabolite Levels, and Seedling Vigor

Impact of Combined Glutathione and Zn Application for Seed Priming in Ameliorating the Adverse Effects of Water Stress on Maize Seed Germination Attributes, Metabolite Levels, and Seedling Vigor

Drought trigger thresholds for different levels of vegetation loss in China and their dynamics

Frequent meteorological droughts can negatively impact terrestrial ecosystems by controlling the opening and closing of vegetation stomatal and altering vegetation structure to limit the ability of vegetation to sequester carbon. Due to the lagging and accumulation effects of drought on vegetation growth, drought trigger thresholds for different levels of vegetation loss are still unclear, which is very important for accurately assessing the future impacts of drought on terrestrial ecosystem. Therefore, this study proposed a framework to investigate drought trigger thresholds under various vegetation losses based on copula theory and conditional probabilities, and assessed the dynamics of drought trigger thresholds and possible causes, based on the random forest model. In addition, we used multiple GPP and soil water datasets for the analysis to ensure the robustness of relevant findings. The results show that: (1) there is a generally positive correlation between GPP and SPEI in China, and the response time of vegetation to drought is mostly on a short time scale (less than or equal to 4 months); (2) drought trigger thresholds are also higher in eastern China, with lower vegetation resistance and significantly higher risk of vegetation productivity loss than in other regions; (3) the trigger thresholds in northeastern China show a decreasing trend, with vegetation resistance gradually increasing. CO2 fertilization enhances vegetation drought resistance, but the magnitude of resistance increase is reduced due to the adverse effects of water stress and VPD on vegetation. The findings of this study may advance our comprehension of terrestrial ecosystem vulnerability and response to drought, and further provide scientific guidance for watershed water allocation, drought preparedness and risk management.

Exogenous α-Tocopherol Regulates the Growth and Metabolism of Eggplant (Solanum melongena L.) under Drought Stress.

The present investigation was designed to improve drought stress tolerance in eggplant (Solanum melongena L.) through the exogenous application of α-tocopherol (TOC). For exogenous application, two modes, i.e., foliar spray (FS) and pre-sowing seed treatment (PS), were used. Water deficiency treatment (50% field capacity (FC)) was applied on 32-day-old seedlings of two eggplant cultivars, i.e., Janak and Black Beauty. Five levels of TOC (0 mg/L, 50 mg/L PS, 100 mg/L PS, 50 mg/L FS, and 100 mg/L FS) were applied as PS and FS. Pre-sowing seed treatment was conducted before seed sowing, while FS treatment after 30 days of drought stress treatment. After 15 days of TOC as an FS application, it was observed that drought stress significantly reduced plant growth (5-15%) and chlorophyll contents (4-10%), while it increased proline (4-6%), glycine betaine (GB) (5-10%), malondialdehyde (MDA) (10.8%), hydrogen peroxide (15-16%), relative membrane permeability (RMP) (5-8%), and the activities of peroxidase (7-8%) and superoxide dismutase (12-15%) in both eggplant cultivars. The TOC application (FS and PS) exhibited a positive role in overcoming the adverse effect of water stress on eggplants. Plant growth increased (15-18%) as a result of the application of TOC, which could be linked with improved chlorophyll, ascorbic acid (AsA), GB, proline, total soluble proteins (TSP), and the activities of peroxidase (POD) and superoxide dismutase (SOD) activities. The reactive oxygen species H2O2 was also decreased by TOC application. Overall, TOC as a foliar spray was more effective in improving the accumulation of proline, GB, AsA, and activities of SOD and POD enzymes, while PS treatment was more effective in reducing RMP and improving the TSP of eggplant. Cv. Black Beauty was comparatively better in root dry weight, chlorophyll a and b, and MDA contents, while cv. Janak in RMP, AsA, TSP, and activity of the POD enzyme. It can be inferred that the application of TOC was useful in counteracting the harmful effects of drought stress on both cultivars of eggplants.

Mitigation of PEG-Induces Drought Stress in Wheat (Triticum durum) by Exogenous Application of Proline

Drought is considered one of the most important environmental stresses that has serious limitations on production of most crop plants, including wheat. Proline is an amino acid closely associated with plant responses to environmental constraints. This research aims to study the response of four varieties of durum wheat (Triticum durum) subjected to water stress stimulated by polyethylene glycol (20% PEG-6000) which is equivalent to osmotic potential of -1.2 Mpa. A total of 4 wheat genotypes were grown hydroponically and four treatments were imposed. Wheat plants exposed to drought stress showed reduced growth, which was correlated with reduced relative water content, chlorophyll content and stomatal conductance as evidenced by principle component analysis (PCA). It also revealed that electrolyte leakage and malondialdehyde (MDA) accumulations were closely related with the declined growth and wheat plants development under drought stress. Importantly, application of 6 mM of exogenous proline improved the growth responses of wheat plants to drought stress. Proline strengthened numerous physio-biochemical processes coupled with decreasing in MDA levels which indicates successful adaptation of wheat plants to drought stress. The results of PCA strongly supported that application of proline in stressful conditions ameliorated the responses of wheat mostly by enhancing physiological and biochemical activities. Eventually, it can be concluded that proline supplementation is one of the useful approaches to alleviate the adverse effects of water stress on wheat crop.

The influence of silica upon quantitative, qualitative, and biochemical traits of tomato under water stress

Water stress is by far the most serious limiting factor to tomato (Solanum lycopersicom) production, particularly in Iran where located in arid and semi-arid regions. Silicon (Si) is considered an effective element to mitigate the adverse effects of water stress by promoting plant growth and production. Therefore, the present study was designed to evaluate the effects of the foliar application of Si (0, 100, and 200 mg L–1) and three water regimes – no stress (100), mild stress (80%), and severe stress (60%) – on the growth parameters, the yield, and the fruit quality as well as antioxidant status of the tomato. The imposed water stress significantly increased the total soluble solids (TSS), the total acidity (TA), and the flavonoids as well as antioxidant defense parameters such as catalase (CAT) and peroxidase (POX), while the growth parameters (plant height and leaf number) and tomato yield were decreased. In contrast, the foliar application of Si (200 mg L–1) remarkably improved the total yield of tomatoes when exposed to water stress by improving the antioxidant enzyme activities and total flavonoid compounds. In addition, the application of Si could significantly improve the growth parameters (plant height and leaf number) and fruit quality (fruit firmness and size). As a result, the foliar application of Si could be suggested as an effective strategy for imparting water stress resistance in the tomato.

Effect of nitrogen fertilizers on agronomic, essential and enzymatic properties of marigold (Calendula officinalis L.) under normal and drought conditions

To investigate the effect of mineral and organic nitrogen fertilizers on some of the quantitative and qualitative reactions of marigold under normal and drought stress, a study was conducted in a split-plot factorial and based on a completely randomized block design with three replications. The first factor included irrigation (normal and water deficit) in the main plot and sub-factor included foliar application of nitrogen fertilizer (control, nitrogen (N), nano-chelate nitrogen (NC) and nitrogen fertilizer+ nano-nitrogen fertilizer (N+NC)) and biofertilizer (control, Azotobacter and Azospirillum) as factorial was placed in sub-plots. Although water deficit stress reduced plant height, flower dry weight, number of seeds per head, 1000-grain weight, biological yield, grain yield and essential oil yield, N + NC foliar application could moderate the adverse effect of water stress on the grain yield, biological yield and essential oil yield. In addition, inoculation of seeds with Azospirillum under water stress conditions could increase the number of seeds per head, 1000-grain weight and essential oil yield compared to the control treatment. NC foliar application and Azotobacter inoculation showed a synergistic effect on the content of proline enzymes and antioxidant activity. Also, simultaneous application of nitrogen + nano-chelate nitrogen foliar application along with seed inoculation with Azospirillum could have a positive effect on increasing flower dry weight, the number of seeds per head, 1000-seed weight, biological yield, grain yield, essential oil yield and proline content.

Exogenous Nitric Oxide and Silicon Applications Alleviate Water Stress in Apricots.

Many plants confront several environmental stresses including heat, water stress, drought, salinity and high-metal concentrations that are crucial in defining plant productivity at different stages of their life cycle. Nitric oxide (NO) and Silicon (Si) are very effective molecules related in most of them and in varied biochemical events that have proven to be protective during cellular injury caused by some stress conditions like water stress. In the current work, we studied the effect of Si and NO alone and NO + Si interactive application on the response of plants exposed to water deficiency and well-watered plants for the Milord apricot variety. Water stress caused a reduce in chlorophyll content, dry and fresh weight, leaf area, stomatal conductivity, leaf relative water content and nutrient elements, while it caused an increase in leaf temperature, leaf proline, leaf malondialdehyde (MDA) content and membrane permeability. Si, NO and Si + NO combination treatments under water stress conditions significantly decreased the adverse effects of water stress on leaf temperature, leaf area, dry and fresh weight, stomata conductivity, relative water content, membrane permeability, L-proline and MDA content. The shoot dry weight, chlorophyll content, stomata conductivity and leaf relative water content in Si + NO treated apricot saplings increased by 59%, 55%, 12% and 8%, respectively. Combined treatment (Si + NO) was detected to be more effective than single applications (Si or NO) on some physiological, biochemical, morphological and nutritional properties of apricot under water stress conditions.

Do Proline and Glycine Betaine Mitigate the Adverse Effects of Water Stress in Spinach?

Do Proline and Glycine Betaine Mitigate the Adverse Effects of Water Stress in Spinach?

Melatonin alleviates the adverse effects of water stress in adult olive cultivars (Olea europea cv. Sevillana & Roughani) in field condition

Olive trees are considered among the most resilient crops in Mediterranean basin. However, prolonged water stress may adversely affect plant productivity and quality of fruits and oil. Therefore, it is essential to design new agronomic strategies to improve plant water stress tolerance and secure yield and product stability of this important agricultural crop. Under water deficit, plants cope with serious threats, and melatonin (MEL), as a versatile signaling biomolecule, can play a crucial role in morphological and physiological modifications of plants able to enhance drought stress tolerance. In this view, the current research aimed at elucidating the potential beneficial role of exogenous foliar application of MEL (0 and 100 µM) to Sevillana and Roughani olive cultivars under different water stress levels (100%, 75%, and 50% ET). In particular, the morphological, physiological and biochemical changes occurring in leaves treated with or without MEL and the quality of fruits and oil were discussed. A decrease of electrolyte leakage (EL) and malondialdehyde (MDA) content as well as an increase of relative water content (RWC) in MEL-sprayed leaves of drought stress trees were observed. The application of MEL was also associated with higher K+ to Na+ ratio, Ca2+ content, phenolic and soluble carbohydrates contents and a lower decline chlorophyll (Chl) levels. MEL-treated leaves also showed higher catalase (CAT) and peroxidase (POD) activities, responsible for scavenging reactive oxygen species (ROS) generated during drought stress in a severity-dependent manner. MEL-foliar application enhanced the oil content and yield in the olive fruits in both cultivars compared to the untreated ones. Since MEL was also able to exert a beneficial effect on both Sevillana and Roughani cultivar trees by improving their crop water productivity (WPc) under water deficit, it can be considered an effective eco-friendly candidate to minimize the detrimental consequences of water stress.

ALLEVIATION OF WATER STRESS ON SOYBEAN (Glycine max) BY FOLIAR APPLICATION OF POTASSIUM

An experiment was performed in wiry greenhouse at Giza Experimental Research Station (30.0204508, 31.2067921), ARC, during two summer seasons of 2019 and 2020 to determine the optimum potassium requirement for mitigating the adverse effects of water stress and improving photosynthetic rate, oxidative substance, RWC, growth and seed quality of soybean. Soybean plants were exposed to water stress at different growth stages under water limited regimes,i.e100% (control), 88% (moist), 76% (medium) and 64% (dry) as well as Potassium at the concentrations of 1 and 2% K2O in addition to spraying with water (as control) were applied. Increasing water stress up to 64% significantly decreased chlorophyll fluorescence, RWC, LAI, CGR and yield component, in the contrary, proline, lipid peroxidation and total soluble protein content increased in response to water stress. In water stress treatments, plants treated with 2%K2O showed the highest values for chlorophyll fluorescence (Fv/Fm), RWC, LAI, CGR, protein, carbohydrate, oil, N, P, k seed content, germination measurements and yield component, while proline, lipid peroxidation, total soluble protein content and EC gave the lowest values. It seems that the application of potassium in 2%K2O concentration may improve plant functions in both normal and stress conditions.

Exogenous application of agmatine improves water stress and salinity stress tolerance in turnip (Brassica rapa L.)

This study was carried out to determine the consequence of foliar application of agmatine (0 and 0.5 mM), on growth, physiological and biochemical traits, and yield of turnip (Brassica rapa L.) plants grown under water stress or salt stress conditions. The effect of three irrigation regimes (100%, 80% and 40% of field capacity) and three salt concentrations (0, 100 and 200 mM NaCl) on turnip plants grown in pots under greenhouse conditions were studied. Water deficit developed at 40% Field capacity (FC) and salinity stress, especially at 200 mM, resulted in significant decreases in all growth parameters when compared to control plants (100% FC) including root length and diameter as well as shoot weights per plant. Water stress and high salt stress negatively affected most physiological and biochemical characteristics such as total chlorophyll, photosynthetic rate, stomatal conductance, and transpiration rate. Water use efficiency (WUE) increased under 80% FC or 100 mM NaCl. Antioxidant enzymes activity, catalase and peroxidase and glutathione reductase, increased with water stress and salt stress. Foliar application of agmatine seemed to alleviate the adverse effects of water stress and salt stress on turnip. Alleviating harmful effects of salt stress and enhancing water stress tolerance by agmatine was associated with improving leaf gas exchange, antioxidant enzymes and protein profile.

Antioxidant status and their enhancements strategies for water stress tolerance in chickpea.

Water stress executes severe influences on the plant growth and development through modifying physio-chemical properties. Therefore, a field experiment was designed to evaluate the antioxidant status and their enhancements strategies for water stress tolerance in chickpea on loam and clay loam soils under agro-ecological conditions of Arid Zone Research Institute, Bahawalpur (29.3871 °N, 71.653 °E) and Cholistan farm near Derawer (28.19°N, 71.80°E) of Southern Punjab, Pakistan during winter 2014-15. Experimental treatments comprised of two chickpea cultivars i.e. Bhakhar 2011 (drought tolerant) and DUSHT (drought sensitive), two water stress levels i.e. water stress at flowering stage and water stress at flowering + pod formation + grain filling stage including well watered (control) and two exogenous application of osmoprotectants i.e. glycine betaine (GB) 20 ppm and proline 10 uM including distilled water (control). Results indicated that water stress at various growth stages adversely affects the growth, yield and quality attributes of both chickpea cultivars. Exogenous application of GB and proline improved the growth, yield and quality parameters of both chickpea cultivars even under water stress conditions. However, superior results were obtained with exogenously applied GB on Bhakhar 2011 under well-watered conditions. Similarly, foliar spray of GB on chickpea cultivar Bhakhar 2011 under stress at flowering + pod formation + grain filling stage produced maximum superoxide dismutase, peroxidase and catalase contents. These results suggested that application of GB mitigates the adverse effects of water stress and enhanced tolerance in chickpea mainly due to higher antioxidant enzymes activity, demonstrating the protective measures of plant cells in stress condition. Hence, antioxidants status might be a suitable method for illustrating water stress tolerance in chickpea.