Adverse Effects Of Drought Stress Research Articles

Reduction of Adverse Effects of Drought Stress on Germination Indices and Antioxidant Enzymes of Licorice Seeds (Glycyrrhiza) Using Cold Plasma

Reduction of Adverse Effects of Drought Stress on Germination Indices and Antioxidant Enzymes of Licorice Seeds (Glycyrrhiza) Using Cold Plasma

Physiological Parameters and Transcriptomic Levels Reveal the Response Mechanism of Maize to Deep Sowing and the Mechanism of Exogenous MeJA to Alleviate Deep Sowing Stress

Deep sowing, as a method to mitigate drought and preserve soil moisture and seedlings, can effectively mitigate the adverse effects of drought stress on seedling growth. The elongation of the hypocotyl plays an important role in the emergence of maize seeds from deep-sowing stress. This study was designed to explore the function of exogenous methyl jasmonate (MeJA) in the growth of the maize mesocotyl and to examine its regulatory network. The results showed that the addition of a 1.5 μ mol L−1 MeJA treatment significantly increased the mesocotyl length (MES), mesocotyl and coleoptile length (MESCOL), and seedling length (SDL) of maize seedlings. Transcriptome analysis showed that exogenous MeJA can alleviate maize deep-sowing stress, and the differentially expressed genes (DEGs) mainly include ornithine decarboxylase, terpene synthase 7, ethylene responsive transcription factor 11, and so on. In addition, candidate genes that may regulate the length of maize hypocotyls were screened by Weighted Gene Co-expression Network Analysis (WGCNA). These genes may be involved in the growth of maize hypocotyls through transcriptional regulation, histones, ubiquitin protease, protein binding, and chlorophyll biosynthesis and play an important role in maize deep-sowing tolerance. Our research findings may provide a theoretical basis for determining the tolerance of maize to deep-sowing stress and the mechanism of exogenous hormone regulation of deep-sowing stress.

Enhancing growth and bioactive metabolites characteristics in Mentha pulegium L. via silicon nanoparticles during in vitro drought stress

The development and production of secondary metabolites from priceless medicinal plants are restricted by drought stress. Mentha pulegium L. belongs to the Lamiaceae family and is a significant plant grown in the Mediterranean region for its medicinal and aesthetic properties. This study investigated the effects of three polyethylene glycol (PEG) (0, 5, and 10%) as a drought stress inducer and four silicon nanoparticle (SiNP) (0, 25, 50, and 100 ppm) concentrations as an elicitor to overcome the adverse effect of drought stress, on the growth parameters and bioactive chemical composition of M. pulegium L. plants grown in vitro. The experiment was performed as a factorial experiment using a completely randomized design (CRD) consisting of 12 treatments with two factors (3 PEG × 4 SiNPs concentrations), 6 replicates were used for each treatment for a total of 72 experimental units.The percentage of shoot formation was inversely proportional to the PEG concentration; for the highest PEG concentration, the lowest percentage of shoot formation (70.26%) was achieved at 10% PEG. SiNPs at 50 ppm enhanced shoot formation, the number of shoots, shoot height, fresh and dry weight, rosmarinic acid, total phenols, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. The methanol extract from M. pulegium revealed the presence of significant secondary metabolites using gas chromatography‒mass spectrometry (GC–MS). The principal constituents of the extract were limonene (2.51, 2.99%), linalool (3.84, 4.64%), geraniol (6.49, 8.77%), menthol (59.73, 65.43%), pulegone (3.76, 2.76%) and hexadecanoic acid methyl ester or methyl palmitate (3.2, 4.71%) for the 0 ppm SiNPs, PEG 0% and 50 ppm SiNPs, and PEG 10%, respectively. Most of the chemical components identified by GC‒MS in the methanol extract were greater in the 50 ppm SiNP and 10% PEG treatment groups than in the control group. SiNP improves drought tolerance by regulating biosynthesis and accumulating some osmolytes and lessens the negative effects of polyethylene glycol-induced drought stress.Based on the results, the best treatment for most of the parameters was 50 ppm SiNPs combined with 10% PEG, the morphological and chemical characteristics were inversely proportional to the PEG concentration, as the highest PEG concentration (10%) had the lowest results. Most parameters decreased at the highest SiNP concentration (100 ppm), except for the DPPH scavenging percentage, as there was no significant difference between the 50 and 100 ppm SiNPs.

Selenium Nanoparticles Boost the Drought Stress Response of Soybean by Enhancing Pigment Accumulation, Oxidative Stress Management and Ultrastructural Integrity

Drought is a persistent and devastating obstacle to crop production, affecting both humanity and livestock. The application of selenium (Se) effectively mitigates various types of abiotic stresses and enhances crop yield under unfavorable conditions. However, our understanding of how nano-Se (nSe) alleviates drought stress (DS) in soybeans is still limited. To address this gap, our study focused on assessing the effectiveness of foliar nSe application during the reproductive stage of soybeans. Three concentrations of nSe were applied to plants grown in pots filled with clay loam soil, simulating DS conditions. Our findings reveal that nSe spraying significantly promoted the accumulation of above-ground dry biomass and enhanced relative water content (RWC) and photosynthetic pigment over alone-DS treatment. Furthermore, nSe application boosted the activity and contents of protective enzymes and osmolytes, resulting in a dose-dependent reduction in electrolyte leakage (EL), reactive oxygen species (ROS) accumulation, and malondialdehyde (MDA) content. Additionally, nSe improved stomatal characteristics and mesophyll cell ultrastructure, further mitigating the adverse effects of drought stress. These findings suggest the potential of nSe as an effective strategy to enhance soybean tolerance and potentially improve crop yields under drought conditions.

Silicon drip fertigation improved sugar beet root and canopy growth and alleviated water deficit stress in arid areas

Crop growth is highly susceptible to drought stress due to water scarcity in arid areas. Silicon (Si) fertilizer could improve the tolerance of crops to drought stress, but the effect of drip fertigation of Si fertilizer on the growth and yield of sugar beets under drought stress is still unclear. In this field experiment conducted in 2022 and 2023 in the arid northwest China, the effects of different Si fertilizer application rates (0 kg ha−1 (Si0), 15 kg ha−1 (Si1), 38 kg ha−1 (Si2), 75 kg ha−1 (Si3)) on the growth, yield, and resource use efficiency of sugar beets (cultivars Beta356 (BT) and Strube13092 (ST)) under deficit irrigation (60 % of crop evapotranspiration (ETc), W2) were explored. The results showed that deficit irrigation (W2Si0) reduced the taproot and fibrous root growth, leaf net photosynthetic rate (Pn), leaf relative water content (LRWC), and leaf area index (LAI) of cultivar BT compared with full irrigation (100 % of ETc, W1). Under deficit irrigation, Si application (W2Si1, W2Si2, and W2Si3) alleviated the drought stress by increasing the number of fibrous roots in 17.5–70.0 cm soil layer and promoted the growth of taproots. Besides, it also increased the leaf moisture and photoassimilate production by increasing plant Si uptake, LRWC, LAI, and Pn. This finally increased the taproot yield (TY), irrigation water use efficiency (IWUE), and partial factor productivity of nitrogen (PFPN) by 11.2 % - 22.9 %, 6.5 % - 19.3 %, and 6.3 % - 19.3 %, respectively in cultivar BT and by 8.8 % - 27.1 %, 13.4 % - 30.8 %, and 13.4 % - 30.8 %, respectively in cultivar ST, compared with W2Si0. Regression analysis showed that the Si fertilizer application rate 64 kg ha−1 could maximize the TY of cultivar BT, but the net revenue (NR) was significantly lower than that of the W1 treatment. The Si fertilizer application rate 71 kg ha−1 could increase the TY of cultivar ST and achieve a NR similar to that of the W1 treatment. Therefore, in arid regions, Si application could alleviate the adverse effects of drought stress on drip-irrigated sugar beet root and shoot growth and improve yield, but the Si application rate varied with sugar beet cultivars.

Silicon and Seaweed Extract Injection into Olive Tree (Olea europaea L.) Trunks Results in the Tree’s Drought Stress Resistance

ABSTRACT Trunk injection applies more nutrients in the correct volume and composition, delivering ideal results with fewer fertilizer treatments under drought-stress conditions. We used a completely randomized block design to examine the effects of trunk injection therapy on the development of drought stress tolerance in olive trees in arid climates. Treatments included seaweed extract (SWE), potassium amino acid chelate (PAC), calcium silicate (CS), and potassium silicate (PS) at five different concentrations: 0.25, 0.5, 1, 2, and 4% for each treatment. Each treatment consisted of four replications – four dry replications for each treatment and four irrigation controls – each receiving weekly irrigation. The findings showed that, in comparison to drought control, trunk injection of PAC at a concentration of 2% enhances the relative water content of leaf and proline and decreases electrolyte leakage (EL) and malondialdehyde (MDA) content. Chlorophyll a, carotenoids, and proline content are all significantly higher in the trunk after CS injection at a 4% concentration than in the control treatment. MDA and EL were also reduced. Injecting PS leads to an increase in proline and photosynthetic pigments. The SWE treatment improved the proline, relative leaf water content, and photosynthetic pigments. To sum up, trunk injection treatments under drought conditions improved plant photosynthetic pigments, increased proline content, prevented relative water content reduction, and prevented an increase in MDA and EL. In conclusion, among the several treatments, the use of 2% PS was the most effective at reducing the adverse effects of drought stress on olive plants.

Cultivating Pharmaceutical Potential: Optimising Triacontanol Application to Enhance Linseed’s Attributes under Drought Stress

Background: Triacontanol (TRIA) has been identified as a potent plant growth regulator, demonstrating significant benefits under various stress conditions. However, its specific impact on Linum usitatissimum L. (flax) under drought stress conditions remains underexplored. This study investigates the effects of TRIA on the growth, physiology, and biochemistry of two flax genotypes subjected to drought stress, aiming to enhance our understanding of its potential as a biostimulant for improving crop resilience and productivity. Objective: The primary objective of this study was to evaluate the effects of different concentrations of TRIA on the growth, physiological, and biochemical responses of two flax genotypes under drought stress conditions. We aimed to determine whether TRIA application could mitigate the adverse effects of drought and enhance plant performance. Methods: This study was conducted using two flax genotypes, G-20888 and G-22186. Plants were grown under controlled conditions and subjected to drought stress by maintaining soil moisture at 50% field capacity. TRIA was applied in three concentrations: 0 M (control), 10^-6 M, and 10^-7 M. A completely randomized design was used with three replications for each treatment. Plant growth parameters, including root length, shoot length, plant height, and shoot fresh weight, were measured. Physiological parameters such as chlorophyll content, relative water content (RWC), and electrolyte leakage were assessed. Biochemical analyses included the estimation of antioxidant enzyme activities (superoxide dismutase, catalase, and peroxidase). Data were statistically analyzed using SPSS version 25.0. Results: TRIA application significantly improved root length, shoot length, plant height, and shoot fresh weight in both flax genotypes under drought stress. For genotype G-20888, root length increased from 5.1 cm (control) to 6.8 cm (TRIA 10^-7 M). Shoot length showed a similar trend, with increases from 8.3 cm (control) to 10.1 cm (TRIA 10^-7 M). In G-22186, plant height increased from 70 cm (control) to 82 cm (TRIA 10^-7 M). Chlorophyll content increased by 15%, and RWC by 18% in TRIA-treated plants compared to controls. Antioxidant enzyme activities were also enhanced, with catalase activity increasing by 25% and peroxidase by 30%. Conclusion: TRIA application significantly mitigated the adverse effects of drought stress on flax genotypes by enhancing growth, physiological, and biochemical parameters. The findings suggest that TRIA could be an effective biostimulant for improving drought tolerance in flax, potentially leading to better crop resilience and productivity.

Mitigation of drought stress effects on alfalfa (Medicago sativa L.) callus through CaO nanoparticles and graphene oxide in tissue culture conditions

Drought stress poses a significant threat to fertile soils worldwide, triggering profound physiological, biochemical, and molecular changes in plants that adversely impact agricultural productivity. This study explores the potential of nanotechnology, specifically Calcium Oxide Nanoparticles (CaO NPs) and Graphene Oxide (GO), to ameliorate the negative effects of drought stress on two distinct alfalfa ecotypes. Seeds from Erzurum and Konya regions were regenerated in the Murashige and Skoog (MS) medium, and ensuing callus formation was induced through 1 mg L−1 2,4-D and 1 mg L−1 kinetin MS medium. The callus samples underwent a one-month treatment with varying concentrations of mannitol (50 and 100 mM), CaO NPs, and GO (0.5 and 1.5 ppm). Results revealed a decrease in dry/wet weight with increasing mannitol concentration, contrasting with an increase in weight under CaO NPs and GO treatment. Proline, DNSA, MDA, and H2O2 exhibited proportional increases under drought stress, while CaO NPs and GO treatments mitigated these effects. Physiological and biochemical analyses identified optimal conditions for Erzurum as 50 mM mannitol/2 CaO NPs/0.5 ppm GO, and for Konya as 50 mM mannitol/0.5 ppm GO. Gene expression analysis indicated up-regulation of mtr-miR159 and mtr-miR393 with heightened drought stress, with down-regulation observed in CaO NPs and GO treatments. Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) confirmed Ca2+ accumulation in alfalfa tissues. In conclusion, CaO NPs and GO treatments exhibited a significant reduction in the adverse effects of drought stress on alfalfa callus under tissue culture conditions. This research sheds light on the potential of nanotechnological interventions to alleviate the impact of environmental stressors on crop plants, opening avenues for sustainable agriculture in the face of changing climatic conditions. Further investigations are warranted to elucidate the underlying mechanisms and scalability of these findings for field applications.

High-nitrogen fertilizer alleviated adverse effects of drought stress on the growth and photosynthetic characteristics of Hosta ‘Guacamole’

BackgroundSeveral plants are facing drought stress due to climate change in recent years. In this study, we aimed to explore the effect of varying watering frequency on the growth and photosynthetic characteristics of Hosta ‘Guacamole’. Moreover, we investigated the effect of high-nitrogen and -potassium fertilizers on alleviating the impacts of drought stress on the morphology, photosynthetic characteristics, chlorophyll fluorescence, fast chlorophyll a fluorescence transient, JIP-test parameters, and enzymatic and non-enzymatic scavenging system for reactive oxygen species (ROS) in this species.ResultsLeaf senescence, decreased chlorophyll contents, limited leaf area, and reduced photosynthetic characteristics and oxygen-evolving complex (OEC) activity were observed in Hosta ‘Guacamole’ under drought stress. However, high-nitrogen fertilizer (30-10-10) could efficiently alleviate and prevent the adverse effects of drought stress. High-nitrogen fertilizer significantly increased chlorophyll contents, which was higher by 106% than drought stress. Additionally, high-nitrogen fertilizer significantly improved net photosynthetic rate and water use efficiency, which were higher by 467% and 2900% than those under drought stress. It attributes that high-nitrogen fertilizer could reduce transpiration rate of leaf cells and stomatal opening size in drought stress. On the other hand, high-nitrogen fertilizer enhanced actual photochemical efficiency of PS II and photochemical quenching coefficient, and actual photochemical efficiency of PS II significantly higher by 177% than that under drought stress. Furthermore, high-nitrogen fertilizer significantly activated OEC and ascorbate peroxidase activities, and enhanced the performance of photosystem II and photosynthetic capacity compared with high-potassium fertilizers (15-10-30).ConclusionsHigh-nitrogen fertilizer (30-10-10) could efficiently alleviate the adverse effects of drought stress in Hosta ‘Guacamole’ via enhancing OEC activity and photosynthetic performance and stimulating enzymatic ROS scavenging system.

Mitigating drought stress in wheat plants (Triticum Aestivum L.) through grain priming in aqueous extract of spirulina platensis

BackgroundThe study focuses on the global challenge of drought stress, which significantly impedes wheat production, a cornerstone of global food security. Drought stress disrupts cellular and physiological processes in wheat, leading to substantial yield losses, especially in arid and semi-arid regions. The research investigates the use of Spirulina platensis aqueous extract (SPAE) as a biostimulant to enhance the drought resistance of two Egyptian wheat cultivars, Sakha 95 (drought-tolerant) and Shandawel 1 (drought-sensitive). Each cultivar’s grains were divided into four treatments: Cont, DS, SPAE-Cont, and SPAE + DS. Cont and DS grains were presoaked in distilled water for 18 h while SPAE-Cont and SPAE + DS were presoaked in 10% SPAE, and then all treatments were cultivated for 96 days in a semi-field experiment. During the heading stage (45 days: 66 days), two drought treatments, DS and SPAE + DS, were not irrigated. In contrast, the Cont and SPAE-Cont treatments were irrigated during the entire experiment period. At the end of the heading stage, agronomy, pigment fractions, gas exchange, and carbohydrate content parameters of the flag leaf were assessed. Also, at the harvest stage, yield attributes and biochemical aspects of yielded grains (total carbohydrates and proteins) were evaluated.ResultsThe study demonstrated that SPAE treatments significantly enhanced the growth vigor, photosynthetic rate, and yield components of both wheat cultivars under standard and drought conditions. Specifically, SPAE treatments increased photosynthetic rate by up to 53.4%, number of spikes by 76.5%, and economic yield by 190% for the control and 153% for the drought-stressed cultivars pre-soaked in SPAE. Leaf agronomy, pigment fractions, gas exchange parameters, and carbohydrate content were positively influenced by SPAE treatments, suggesting their effectiveness in mitigating drought adverse effects, and improving wheat crop performance.ConclusionThe application of S. platensis aqueous extract appears to ameliorate the adverse effects of drought stress on wheat, enhancing the growth vigor, metabolism, and productivity of the cultivars studied. This indicates the potential of SPAE as an eco-friendly biostimulant for improving crop resilience, nutrition, and yield under various environmental challenges, thus contributing to global food security.

Effect of drought stress on the expression pattern of genes involved in ABA biosynthesis in Desi-type chickpea (Cicer arietinum L.).

The behavior of Abscisic acid (ABA) as a stress phytohormone may be involved in mechanisms leading to tolerance and survival in adverse environmental conditions such as drought stress. Here, we evaluated ABA-mediated responses at physio-biochemical and molecular levels in drought-stressed seedlings of two different Desi-type chickpea genotypes (10 as a tolerant genotype and 247 as a sensitive one). Under drought stress, two chickpea genotypes showed a decrease in their relative water content (RWC), and the intense decrease was related to the sensitive genotype (73.9%) in severe stress. Hydrogen peroxide (H2O2) and malondialdehyde (MDA) concomitant with the severity of stress increased in genotypes and the higher increase was in the sensitive genotype (5.8-fold and 3.43-fold, respectively). In the tolerant genotype, the enhanced accumulation of total phenolic content (1.75-fold) and radical scavenging action, based on 1,1-diphenyl-2-picrylhydrazyl test (DPPH), (1.69-fold) were simultaneous with ABA accumulation (1.53-fold). In the tolerant genotype, transcriptional analysis presented upregulation of Zeaxanthin epoxidase (ZEP) (1.35-fold), 9-cis-epoxycarotenoid dioxygenase (NCED) (5.16-fold), and Abscisic aldehyde oxidase (AAO) (1.52-fold compared to control conditions) genes in severe stress in comparison with mild stress. The sensitive genotype had a declining trend in total chlorophyll (up to 70%) and carotenoid contents (36%). The main conclusion to be drawn from this investigation is that ABA with its regulatory effects can affect drought tolerance mechanisms to alleviate adverse effects of unsatisfactory environmental conditions. In this paper, we tried to indicate that drought stress induces overexpression of genes triggering ABA-mediated drought responses simultaneously in two genotypes while more increment expression was related to the tolerant genotype. At first thought, it seems that the tolerant genotype compared to the sensitive genotype has a genetically inherent ability to cope with and drop adverse effects of drought stress through over-accumulation of ABA as drought.

Unraveling the effects of melatonin on drought-stressed pear rootstocks: A comparative analysis of Dargazi and Pyrodwarf

Drought stress is known as one of the major challenges in most fruit-growing areas. This research aimed to investigate the amelioration effect of pre-drought exogenous melatonin application on the physiological and biochemical response of `Dargazi’ seedling and `Pyrodwarf’ clonal pear rootstocks, grown under water stress and controlled greenhouse conditions. Drought stress was applied by withholding irrigation water for 40 days on one-year-old un-grafted seedlings and clonal pear rootstocks. Gas exchange, chlorophyll content, relative water content, lipid peroxidation, and enzyme antioxidant activity were examined. Pre-drought treatment of melatonin significantly increased drought tolerance, successfully recovered the lost growth and considerably improved photosynthetic efficiency. The adverse effect of drought stress was ameliorated by melatonin through the possible osmotic adjustment such as the increase of proline (102 and 92 g/g FW for `Dargazi' and `Pyrodwarf' respectively) and soluble sugars as well as the improvement of the antioxidative defense system through the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX). The `Dargazi’ seedling rootstock showed better tolerance to drought stress with higher photosynthesis, leaf water content, chlorophyll content, antioxidant enzyme activity, lower lipid peroxidation, and H2O2 generation than the Pyrodwarf clonal rootstock. Also, melatonin ameliorated the negative effect of water stress on photosynthesis and growth parameters through the possible inducing osmotic adjustment and anti-oxidative system under the severe drought stress condition on pear rootstocks. SOD, APX, POD, and CAT activities in Dargazi rootstock were significantly higher than those in control plants by 76.1 %, 34.9 %, 20.93 %, and 124.42 % respectively. Similarly, SOD, APX, POD, and CAT in Pyrodwarf pear rootstock increased in enzyme activities by 56.92 %, 24.37 %, 35.53 %, and 259.52 %, respectively. It is concluded that melatonin application as a pre-drought treatment mitigates the negative effects of drought stress in both rootstocks and the Dargazi rootstock exhibits remarkable resilience to drought stress.

Comparative morpho-physiological and biochemical responses of Capsicum annuum L. plants to multi-walled carbon nanotubes, fullerene C60 and graphene nanoplatelets exposure under water deficit stress

Water deficit stress is one of the most significant environmental abiotic factors influencing plant growth and metabolism globally. Recently, encouraging outcomes for the use of nanomaterials in agriculture have been shown to reduce the adverse effects of drought stress on plants. The present study aimed to investigate the impact of various carbon nanomaterials (CNMs) on the physiological, morphological, and biochemical characteristics of bell pepper plants subjected to water deficit stress conditions. The study was carried out as a factorial experiment using a completely randomized design (CRD) in three replications with a combination of three factors. The first factor considered was irrigation intensity with three levels [(50%, 75%, and 100% (control) of the field capacity (FC)] moisture. The second factor was the use of carbon nanomaterials [(fullerene C60, multi-walled carbon nanotubes (MWNTs) and graphene nanoplatelets (GNPs)] at various concentrations [(control (0), 100, 200, and 1000 mg/L)]. The study confirmed the foliar uptake of CNMs using the Scanning Electron Microscopy (SEM) technique. The effects of the CNMs were observed in a dose-dependent manner, with both stimulatory and toxicity effects being observed. The results revealed that exposure to MWNTs (1000 mg/L) under well-watered irrigation, and GNPs treatment (1000 mg/L) under severe drought stress (50% FC) significantly (P < 0.01) improved fruit production and fruit dry weight by 76.2 and 73.2% as compared to the control, respectively. Also, a significant decrease (65.9%) in leaf relative water content was obtained in plants subjected to soil moisture of 50% FC over the control. Treatment with GNPs at 1000 mg/L under 50% FC increased electrolyte leakage index (83.6%) compared to control. Foliar applied MWNTs enhanced the leaf gas exchange, photosynthesis rate, and chlorophyll a and b concentrations, though decreased the oxidative shock in leaves which was demonstrated by the diminished electrolyte leakage index and upgrade in relative water content and antioxidant capacity compared to the control. Plants exposed to fullerene C60 at 100 and 1000 mg/L under soil moisture of 100 and 75% FC significantly increased total flavonoids and phenols content by 63.1 and 90.9%, respectively, as compared to the control. A significant increase (184.3%) in antioxidant activity (FRAP) was observed in plants exposed to 200 mg/L MWCNTs under irrigation of 75% FC relative to the control. The outcomes proposed that CNMs could differentially improve the plant and fruit characteristics of bell pepper under dry conditions, however, the levels of changes varied among CNMs concentrations. Therefore, both stimulatory and toxicity effects of employed CNMs were observed in a dose-dependent manner. The study concludes that the use of appropriate (type/dose) CNMs through foliar application is a practical tool for controlling the water shortage stress in bell pepper. These findings will provide the basis for more research on CNMs-plant interactions, and with help to ensure their safe and sustainable use within the agricultural chains.

Osmotolerant plant growth promoting bacteria mitigate adverse effects of drought stress on wheat growth.

Drought stress represents a major constraint with significant impacts on wheat crop globally. The use of plant growth-promoting bacteria (PGPB) has emerged as a promising strategy to alleviate the detrimental impacts of water stress and enhance plant development. We investigated 24 strains from diverse ecosystems, assessed for PGP traits and tolerance ability to abiotic stresses (drought, salinity, temperature, pH, heavy metals, pollutants, herbicides, and fungicides). The most effective bacterial strains Providencia vermicola ME1, Pantoea agglomerans Pa, Pseudomonas knackmussi MR6, and Bacillus sp D13 were chosen. Furthermore, these strains exhibited PGP activities under osmotic stress (0, 10, 20, and 30% PEG-6000). The impact of these osmotolerant PGPBs on wheat (Triticum durum L.) growth under drought stress was assessed at two plant growth stages. In an in vitro wheat seed germination experiment, bacterial inoculation significantly enhanced germination parameters. In pot experiments, the potential of these bacteria was evaluated in wheat plants under three treatments: Well-watered (100% field capacity), moderate stress (50% FC), and severe stress (25% FC). Results showed a significant decline in wheat growth parameters under increasing water stress for uninoculated seedlings. In contrast, bacterial inoculation mitigated these adverse effects, significantly improving morphological parameters and chlorophyll pigment contents under the stress conditions. While malondialdehyde (lipid peroxidation) and proline contents increased significantly with drought intensity, they decreased after bacterial inoculation. The antioxidant enzyme activities (GPX, CAT, and SOD) in plants decreased after bacterial inoculation. The increased root colonization capacity observed under water stress was attributed to their ability to favorable adaptations in a stressful environment. This study highlighted the potential of selected PGPB to alleviate water stress effects on wheat, promoting practical applications aimed at enhancing crop resilience under conditions of water shortage.

Physiological Insights of Melatonin Hormone for Alleviation of Drought Stress in Rice

Drought stress significantly hampers crop growth and yield by negatively impacting various biochemical and physiological plant processes. This study aimed to assess drought tolerance in traditional rice varieties using Poly Ethylene Glycol 6000 (PEG 6000) and focused on the effectiveness of melatonin applied through both seed treatment and foliar spray in mitigating the effects of drought stress. The optimal drought screening conditions were determined at a PEG concentration of -4 bars. As the PEG concentration increased, key factors such as germination percentage, vigor index, root length, and shoot length decreased. This indicates that PEG can be a useful tool for early selection of drought tolerant rice varieties. Melatonin (N-acetyl-5-methoxytryptamine), known for alleviating abiotic stress, showed positive effects on seed germination at 200 ppm concentration. The study observed that stomatal closure is a natural response to drought stress, but melatonin application induced partial stomatal opening. Notably, a foliar spray of 100 ppm melatonin demonstrated better recovery from drought stress compared to the 200 ppm concentration. In conclusion, the research suggests that seed treatment with 200 ppm melatonin and foliar spraying with 100 ppm melatonin are the most effective approaches for reducing the adverse effects of drought stress in rice plants.

Elevated CO2 concentration enhances drought resistance of soybean by regulating cell structure, cuticular wax synthesis, photosynthesis, and oxidative stress response

The atmospheric [CO2] and the frequency and intensity of extreme weather events such as drought are increased, leading to uncertainty to soybean production. Elevated [CO2] (eCO2) partially mitigates the adverse effects of drought stress on crop growth and photosynthetic performance, but the mitigative mechanism is not well understood. In this study, soybean seedlings under drought stress simulated by PEG-6000 were grown in climate chambers with different [CO2] (400 μmol mol−1 and 700 μmol mol−1). The changes in anatomical structure, wax content, photosynthesis, and antioxidant enzyme were investigated by the analysis of physiology and transcriptome sequencing (RNA-seq). The results showed that eCO2 increased the thickness of mesophyll cells and decreased the thickness of epidermal cells accompanied by reduced stomatal conductance, thus reducing water loss in soybean grown under drought stress. Meanwhile, eCO2 up-regulated genes related to wax anabolism, thus producing more epidermal wax. Under drought stress, eCO2 increased net photosynthetic rate (PN), ribulose-1,5-bisphosphate carboxylase/oxygenase activity, and alerted the gene expressions in photosynthesis. The increased sucrose synthesis and decreased sucrose decomposition contributed to the progressive increase in the soluble saccharide contents under drought stress with or without eCO2. In addition, eCO2 increased the expressions of genes associated with peroxidase (POD) and proline (Pro), thus enhancing POD activity and Pro content and improving the drought resistance in soybean. Taken together, these findings deepen our understanding of the effects of eCO2 on alleviating drought stress in soybean and provide potential target genes for the genetic improvement of drought tolerance in soybean.

Amelioration of water deficit by application of potassium and FYM in Lens culinaris (L.) Medikus and Brassica napus L. under intercropping system

Lens culinaris is an annual edible legume while Brassica napus is a common oil-production crop. One of the most frequent abiotic stresses endangering agricultural food crops is drought. Drought significantly impairs crop plants’ physiology and productivity which eventually results in plant death. The present research was done to ameliorate the adverse effects of drought stress on the growth, photosynthetic pigments and water status of Brassica napus L. (GSC-7 variety) and Lens culinaris (L.) Medikus (HM-1 variety) intercropping by combined application of potassium and farm yard manure (FYM). The treatments were given as control (2 irrigations), early irrigation (irrigation only during vegetative stage), late irrigation (irrigation only during flowering stage) and stress (0 irrigation) along with different concentrations of potassium and FYM i.e. K0(control) K1(10kg/acre) and K2(20kg/acre) K1M (10kg/acre+10tonne/hectare) and K2M (20kg/acre+10tonne/hectare. At the vegetative stage (45DAS), samples were taken and analyzed for different attributes. Drought stress significantly affected the morphology and physiology of both cultivars by reducing the photosynthetic pigments, water status (relative water content [RWC] and membrane stability index [MSI]) in both cultivars compared to the control. But potassium(K) and FYM supplementation improved both cultivars' RWC, MSI, photosynthetic pigments and growth parameters. In addition, after K and FYM application under drought stress, MDA levels and electrolyte leakage were decreased. These results authenticate that potassium in combination with FYM considerably reduces the effect of drought on both cultivars of intercropping by enhancing the plants' growth, photosynthetic activities and water status.

Improvement of biochemical and antioxidant responses of borage (Borago officinalis L.) under drought stress conditions with the use of vermicompost and zinc sulfate.

Drought poses a significant threat to crop production systems. Therefore, this study aimed to investigate the impact of vermicompost and foliar application of zinc sulfate under conditions of reduced irrigation on the physiological properties of Borage. A two-year experiment was conducted following a split factorial design within a randomized complete block design with three replications at Yasouj University Research Station in 2017 and 2018. The primary factor involved three levels of irrigation cut-off (I1: full irrigation, I2: irrigation cut-off at the flowering stage, and I3: irrigation cut-off during the seed-filling stage). The sub-factor included vermicompost fertilizer at three different levels (N0: control, N1: 5tonha-1, and N2: 10tonha-1), and foliar application of zinc sulfate at three levels (Z0: control, Z1: 2 and Z2: 4mgl-1). During the flowering stage stress, foliar application of 4mgl-1 of zinc sulfate resulted in an increased chlorophyll a + b content in plants (2.91mgg-1FW), while the control showed the lowest amount (2.56mgg-1FW). Vermicompost supplementation improved chlorophyll a + b content during the seed-filling stage under conditions of irrigation cut-off. The results indicated that an increase in vermicompost fertilizer application led to an elevation in relative water content (RWC), with the highest RWC (79.2%) achieved when 10tonha-1 of vermicompost was applied. Irrigation cut-off during the seed-filling stage resulted in increased electrolyte leakage and higher fertilizer usage, thus reducing cell damage. Furthermore, the findings revealed that applying 2 and 4mgl-1 zinc sulfate reduced malondialdehyde content by 5% and 9%, respectively. The catalase, peroxidase, and superoxide dismutase activities demonstrated an increased response to stress mitigation treatments. However, their activities decreased as vermicompost and zinc sulfate levels increased. The study demonstrated that the highest biomass was obtained when 10tonha-1 of vermicompost and 2mgl-1 of zinc sulfate were applied. The flowering stage of the plant exhibited the most significant negative impact under stress conditions. Nonetheless, using vermicompost and zinc sulfate, particularly during the seed-filling phase, alleviated the adverse effects of drought stress. In conclusion, our findings indicate that, although drought stress resulted in increased electrolyte leakage due to elevated free radical production, vermicompost, and zinc sulfate played a role in reducing stress.

The Role of Silver Nanoparticles in Response of In Vitro Boysenberry Plants to Drought Stress

Drought is one of the leading abiotic factors limiting morphological and physiological activities in blackberry cultivation. In this study, the effects of silver nanoparticles (AgNPs) on some morphological and biochemical processes in boysenberry (Rubus ursinus Chamisso and Schlenhtendal) under drought stress were investigated. The experiment was performed with three drought stress levels simulated with Polyethylene Glycol (PEG) (0, 4, 8%) and three AgNP treatments (0, 0.1, 0.2 mg L−1) in vitro conditions. Drought stress reduced root and shoot development of boysenberry plants grown in vitro. The addition of AgNPs significantly alleviated the adverse effect of drought stress and increased the plant growth parameters. Antioxidant activity of superoxide dismutase (SOD) and catalase (CAT) enzymes increased in boysenberry leaves when treated with AgNPs under drought conditions, while the amount of malondialdehyde (MDA) decreased. As a result of the study, 0.1 mg L−1 AgNPs is recommended as the most effective dose to promote the growth and development of in vitro boysenberry plants under drought stress.

Photosynthesis Response and Transcriptional Analysis: Dissecting the Role of SlHB8 in Regulating Drought Resistance in Tomato Plants.

Deciphering drought resistance in crops is crucial for enhancing water productivity. Previous studies have highlighted the significant role of the transcription factor SlHB8 in regulating developmental processes in tomato plants but its involvement in drought resistance remains unclear. Here, gene overexpression (SlHB8-OE) and gene knockout (slhb8) tomato plants were utilized to study the role of SlHB8 in regulating drought resistance. Our findings showed that slhb8 plants exhibited a robust resistant phenotype under drought stress conditions. The stomata of slhb8 tomato leaves displayed significant closure, effectively mitigating the adverse effects of drought stress on photosynthetic efficiency. The slhb8 plants exhibited a decrease in oxidative damage and a substantial increase in antioxidant enzyme activity. Moreover, slhb8 effectively alleviated the degree of photoinhibition and chloroplast damage caused by drought stress. SlHB8 regulates the expression of numerous genes related to photosynthesis (such as SlPSAN, SlPSAL, SlPSBP, and SlTIC62) and stress signal transduction (such as SlCIPK25, SlABA4, and SlJA2) in response to drought stress. Additionally, slhb8 plants exhibited enhanced water absorption capacity and upregulated expression of several aquaporin genes including SlPIP1;3, SlPIP2;6, SlTIP3;1, SlNIP1;2, and SlXIP1;1. Collectively, our findings suggest that SlHB8 plays a negative regulatory role in the drought resistance of tomato plants.