Induced Drought Stress Research Articles

Impacts of alternate wetting and drying and delayed flood rice irrigation on growing season evapotranspiration

As rice production is water intensive, establishing an accurate field–scale water budget is paramount for sustainable use of local water resources. This study’s goal was to quantify and characterize half-hourly and seasonal evapotranspiration (ET) in two commercial, zero–grade rice fields in the U.S. Mid–South over three growing seasons. During each growing season, irrigation regimes for the studied fields differed between alternate wetting and drying (AWD) and delayed flooding (DF). The 2015 growing season enabled a direct comparison of the effects of AWD and DF on ET, while during the 2016 and 2017 seasons both fields were simultaneously under AWD and DF, respectively. The DF method is the region’s most common irrigation practice, and it prescribes a continuous flood to be maintained for the majority of the growing season after the plants have reached the 5-leaf growth stage (40–50 days after planting). In contrast, after holding this initial flooding for 3 weeks, AWD allows for field drying to promote the capture of seasonal rains to reduce irrigation water withdrawal and associated water pumping costs. In this study, ET was estimated using gap–filled eddy covariance observations and two variations of the Penman–Monteith equation. These methods determined growing season ET values between 560 mm and 636 mm. This study found that there were no significant differences in cumulative ET or yield when comparing AWD to DF practices. Furthermore, AWD elicited no change in ET during periods of drying when compared to DF. By this metric, AWD did not induce drought stress within the plants. We conclude that the main benefit of the AWD practice is to take advantage of seasonal rainfall to offset pumping costs and pressure on irrigation water requirements while maintaining yields comparable to conventional irrigation practices.

Melatonin Improves Drought Resistance in Maize Seedlings by Enhancing the Antioxidant System and Regulating Abscisic Acid Metabolism to Maintain Stomatal Opening Under PEG-Induced Drought

Maize (Zea mays L.) is highly sensitive to drought stress, resulting in large losses in yield; therefore, strategies aimed at enhancing drought tolerance are essential. Melatonin improves stress tolerance in plants; however, its mechanism in maize seedlings under drought stress remains unknown. Therefore, we investigated the effects of foliar-sprayed melatonin (100 umol L−1) on the antioxidant system, photosynthetic gas exchange parameters, stomatal behavior, endogenous melatonin and abscisic acid (ABA)-related gene expression in maize seedling leaves under 20% polyethylene glycol (PEG)-induced drought stress. PEG treatment resulted in oxidative stress and stomatal closure, resulting in chlorophyll degradation and inhibition of photosynthesis; thereby, reducing seedling biomass. Melatonin pretreatment significantly improved the relative water content, photosynthetic gas exchange parameters and stomatal behavior; thereby, maintaining chlorophyll contents and photosynthesis. Melatonin also stimulated the antioxidant system, enhancing the clearance of reactive-oxygen species, preventing severe damage under PEG-induced drought. Pre-treatment also increased endogenous melatonin and inhibited up-regulation of NCED1, an ABA synthesis-related gene, as well as selectively up-regulating ABA catabolic genes ABA8ox1 and ABA8ox3, reducing ABA accumulation and inducing stomatal reopening. Overall, these findings suggest that melatonin pre-treatment alleviated the inhibitory effects of drought stress on photosynthesis, enhancing tolerance in maize seedlings.

Drought-tolerant Bacillus megaterium isolated from semi-arid conditions induces systemic tolerance of wheat under drought conditions.

A detailed study of the response of wheat plants, inoculated with drought-tolerant PGPR is studied which would be beneficial to achieve genetic improvement of wheat for drought tolerance. Drought stress, a major challenge under current climatic conditions, adversely affects wheat productivity. In the current study, we observed the response of wheat plants, inoculated with drought-tolerant plant growth-promoting rhizobacteria (PGPR) Bacillus megaterium (MU2) and Bacillus licheniformis (MU8) under induced drought stress. In vitro study of 90 rhizobacteria exhibited 38 isolates showed one or more plant growth-promoting properties, such as solubilization of phosphorus, potassium, and exopolysaccharide production. Four strains revealing the best activities were tested for their drought-tolerance ability by growing them on varying water potentials (-0.05 to -0.73MPa). Among them, two bacterial strains Bacillus megaterium and Bacillus licheniformis showed the best drought-tolerance potential, ACC deaminase activities, IAA production, and antagonistic activities against plant pathogens. Additionally, these strains when exposed to drought stress (-0.73MPa) revealed the induction of three new polypeptides (18kDa, 35kDa, 30kDa) in Bacillus megaterium. We determined that 106cells/mL of Bacillus megaterium and Bacillus licheniformis were enough to induce drought tolerance in wheat under drought stress. These drought-tolerant strains increased the germination index (11-46%), promptness index (16-50%), seedling vigor index (11-151%), fresh weight (35-192%), and dry weight (58-226%) of wheat under irrigated and drought stress. Moreover, these strains efficiently colonized the wheat roots and increased plant biomass, relative water content, photosynthetic pigments, and osmolytes. Upon exposure to drought stress, Bacillus megaterium inoculated wheat plants exhibited improved tolerance by enhancing 59% relative water content, 260, 174 and 70% chlorophyll a, b and carotenoid, 136% protein content, 117% proline content and 57% decline in MDA content. Further, activities of defense-related antioxidant enzymes were also upregulated. Our results revealed that drought tolerance was more evident in Bacillus megaterium as compared to Bacillus licheniformis. These strains could be effective bioenhancer and biofertilizer for wheat cultivation in arid and semi-arid regions. However, a detailed study at the molecular level to deduce the mechanism by which these strains alleviate drought stress in wheat plants needs to be explored.

Salicylic Acid Improves Rice Seed Germination under Induced Drought Stress

Salicylic Acid Improves Rice Seed Germination under Induced Drought Stress

Knockdown of <i>GmSOG1</i> Compromises Drought Tolerance in Transgenic Soybean Lines

Plants are regularly exposed to myriads of stress factors that cause tremendous damage to their genetic make-up. To ensure genome stability and survival over several generations under harsher environmental conditions, plants have evolved a unique mechanism for dealing with DNA damage known as the DNA damage response pathway (DDR). It has been proposed that there may exist a relationship between the DNA damage response pathway and abiotic stress response in plants. To further investigate this relationship, we knocked down the soybean suppressor of gamma response 1 gene (GmSOG1), a master regulatory gene of the DDR, in soybean plants and subjected the generated transgenic plants to drought stress analysis. Gene expression analysis of the GmSOG1 gene in drought stressed soybean tissues revealed high levels of expression in buds and young leaves. The root lengths and root fresh weights of transgenic soybean plants grown on Murashige and Skoog media supplemented with Gamborg B5 vitamins (MSB5 media) containing 200 mM mannitol for 10 days were significantly lesser than those of drought stressed wild-type plants. Polyethylene glycol (PEG) induced drought stress assay in vivo resulted in significant damage in transgenic plants compared with wild-type plants. Also, the relative expressions of known drought responsive transcription factors such as GmDREB1 and GmLEA as well as antioxidation related genes like GmAPX and GmCAT were downregulated in transgenic soybean lines relative to wild-type plants. Moreover, wild-type soybean plants accumulated more chlorophyll and less malondialdehyde (MDA) than transgenic lines. A confirmatory experiment in GmSOG1 overexpressing Arabidopsis plants also showed significantly higher survival rates and anti-oxidation enzyme accumulation in drought stressed GmSOG1 overexpressing Arabidopsis lines compared with wild-type plants. These results suggest that the SOG1 gene may play active roles in plant abiotic stress defense.

Phenotypic Plasticity of Drought Tolerance Traits in a Widespread Eucalypt (Eucalyptus obliqua)

Long-term studies of tree responses to drought stress help us to understand the capacity of species to adapt to their environment. In this study, we investigated how Eucalyptus obliqua adjusts physiological and morphological traits in response to seasonal and multi-year droughts. We monitored physiological and morphological traits over multiple years in undisturbed control and throughfall reduction plots in a eucalypt forest in south-eastern Australia. The throughfall reduction treatment did not induce significantly lower soil moisture in the throughfall reduction plots compared with the control plots. However, natural variability in precipitation and evaporative demand induced drought stress of varying intensity each summer in all plots. We observed a significant relationship between seasonal precipitation and leaf pre-dawn water potential (ΨPD), with less precipitation over summer, resulting in a decline in ΨPD and drought stress when ΨPD fell below −0.75 MPa. Eucalyptus obliqua responded to short-term summer drought through rapid leaf osmotic adjustment which lowered the leaf water potential at the turgor loss point beyond the minimum leaf water potential. Morphological adjustments, such as the reduction of leaf area to sapwood area (higher Huber Value) were moderate during the measurement period and only occurred under severe drought stress (pre-dawn water potential < −1.2 MPa). Overall, E. obliqua responded to short-term mild drought stress through physiological trait plasticity, while morphological adjustment only occurred under a more severe water deficit.

ABA analogue produced by Bacillus marisflavi modulates the physiological response of Brassica juncea L. under drought stress

The present study aims to understand the molecular mechanism involved in beneficial rhizobacteria mediated alleviation of drought stress in the host plant. Bacillus marisflavi CRDT-EB-1 isolated from the rhizosphere soil was found effective in inducing resistance against drought stress in mustard seedlings. Among the different bacterial derivatives tested, the culture filtrate was found to contain bioactive molecules. Solvent extract of bacterial culture filtrate yielded seven distinct bands/fractions on thin layer chromatography (TLC). The fraction four (F4) with Rf value 0.35–0.40 was significant in reducing the adverse effect of drought stress in host plants. Application of F4 resulted in delayed drooping point and higher drought tolerance index (3.34), induced stomatal closure (9.648 μ), seed germination inhibition (12%), and reduced the GA3 induced α-amylase activity in germinating barley seeds. On TLC, F4 turned colorless to orange color upon the spray of 2,4-dinitrophenylhydrazine reagent indicated the presence of aldehyde group. Supporting to this, the peaks between 9.8 and 10.0 ppm in 1H NMR chromatogram confirmed the presence of the aldehyde group. Upon LC-MS/MS analysis of a crude extract of culture filtrate and F4 revealed the presence of compounds with the molecular mass 250.33 and 266.33. By analyzing these data, the identity of the bioactive compounds was predicted as xanthoxin and xanthoxic acid, which are a well-known precursor of Abscisic acid (ABA) in plants. The present study concludes the capability of ABA analogue (xanthoxin like compounds) production by B. marisflavi CRDT-EB-1 and its involvement in inducing drought stress tolerance in the host plant.

Effective Screening of Tropical Wheat Mutant Lines under Hydroponically Induced Drought Stress Using Multivariate Analysis Approach

Effective Screening of Tropical Wheat Mutant Lines under Hydroponically Induced Drought Stress Using Multivariate Analysis Approach

Effective Defense of Aleppo Pine Against the Giant Scale Marchalina hellenica Through Ecophysiological and Metabolic Changes.

Aleppo pine (Pinus halepensis) is widely distributed in the Mediterranean region and in other areas of the world, where it has been introduced due to its adaptive capacity to xerothermic conditions. The giant pine scale Marchalina hellenica often infests Aleppo pine, as well as other pines, in several southeastern European countries, causing pine declines. When combined with the expected intensified heat and drought events in eastern Mediterranean, the impact of this biotic parameter on the host pines may be exacerbated. The importance of understanding the defense mechanisms of Aleppo pine is emphasized by the recent invasion of the pine scale in new regions, like Australia, lacking the insect’s natural enemies, where more intense negative effects on pine species may occur. To date, Aleppo pine’s physiological responses to the infestation by M. hellenica are largely unknown. This study aimed at assessing the responses of Aleppo pine to the giant pine scale attack, both on an ecophysiological and a metabolic level. For this purpose, gas exchange, needle water status, and carbon and nitrogen content were measured during 1 year on healthy and infested adult trees. M etabolic profiling of Aleppo pine needles was also performed before, during, and after the high feeding activity of the insect. The maintenance of stable relative water content, δ13C signatures, and chlorophyll fluorescence in the needles of infested pines indicated that infestation did not induce drought stress to the host pines. At the peak of infestation, stomatal closure and a pronounced reduction in assimilation were observed and were associated with the accumulation of sugars in the needles, probably due to impaired phloem loading. At the end of the infestation period, tricarboxylic acids were induced and phenolic compounds were enhanced in the needles of infested pines. These metabolic responses, together with the recovery of photosynthesis after the end of M. hellenica intense feeding, indicate that in the studied region and under the current climate, Aleppo pine is resilient to the infestation by the giant pine scale. Future research should assess whether these promising defense mechanisms are also employed by other host pines, particularly in regions of the world recently invaded by the giant pine scale, as well as under more xerothermic regimes.

Ocena obiektów cebuli (Allium cepa L.) pod względem tolerancji na suszę w fazie kiełkowania i wzrostu siewek

Celem badań była ocena wpływu niedoboru wody na zdolność kiełkowania nasion i wzrost siewek cebuli oraz identyfikacja obiecujących obiektów do wykorzystania w przyszłych programach hodowli nowych odmian cebuli tolerancyjnych na stres suszy. Oceniono 150 linii/odmian cebuli pochodzących z polskich i zagranicznych firm hodowlano-nasiennych oraz z Banku Genów Instytutu Ogrodnictwa w Skierniewicach. Doświadczenia prowadzono w warunkach laboratoryjnych indukując stres suszy przez zastosowanie 18% poliglikolu etylenowego (PEG8000) w fazie kiełkowania nasion i 10% PEG w fazie siewek. Badane obiekty cebuli wykazały istotne zróżnicowanie pod względem tolerancji na stres suszy, potwierdzone wysokimi wartościami współczynnika zmienności (CV) dla ocenianych parametrów: maksymalny procent skiełkowanych nasion (35,3%), świeża masa siewek (38,5%), długość liścieni siewek (42,9%) i długość korzeni siewek (56,3%). Zanotowano, że niedobór wody najmniej ograniczył kiełkowanie nasion o 23%, następnie długość korzeni o 36%, a najbardziej świeżą masę siewek i długość liścieni, odpowiednio o 52% i 53,5%. Stwierdzono silną korelację (r = 0,81‒0,86) między cechami opisującymi wzrost siewek w warunkach suszy, wskazując, że deficyt wody redukuje wzrost całych siewek. Natomiast zależności pomiędzy nimi a kiełkowaniem w stresie suszy okazały się nieistotne (r = 0,19‒0,24). Spośród 150 obiektów cebuli, genotyp 171026 wykazał wysoki poziom tolerancji na suszę zarówno w fazie kiełkowania, jak i w fazie siewek.

Physiological and Differential Proteomic Analyses of Imitation Drought Stress Response in Sorghum bicolor Root at the Seedling Stage.

Drought is one of the most important constraints on the growth and productivity of many crops, including sorghum. However, as a primary sensing organ, the plant root response to drought has not been well documented at the proteomic level. In the present study, we compared physiological alteration and differential accumulation of proteins in the roots of sorghum (Sorghum bicolor) inbred line BT×623 response to Polyethylene Glycol (PEG)-induced drought stress at the seedling stage. Drought stress (up to 24 h after PEG treatment) resulted in increased accumulation of reactive oxygen species (ROS) and subsequent lipid peroxidation. The proline content was increased in drought-stressed plants. The physiological mechanism of sorghum root response to drought was attributed to the elimination of harmful free radicals and to the alleviation of oxidative stress via the synergistic action of antioxidant enzymes, such as superoxide dismutase, peroxidase, and polyphenol oxidase. The high-resolution proteome map demonstrated significant variations in about 65 protein spots detected on Coomassie Brilliant Blue-stained 2-DE gels. Of these, 52 protein spots were identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF-TOF MS) representing 49 unique proteins; the levels of 43 protein spots were increased, and 22 were decreased under drought condition. The proteins identified in this study are involved in a variety of cellular functions, including carbohydrate and energy metabolism, antioxidant and defense response, protein synthesis/processing/degradation, transcriptional regulation, amino acid biosynthesis, and nitrogen metabolism, which contribute jointly to the molecular mechanism of outstanding drought tolerance in sorghum plants. Analysis of protein expression patterns and physiological analysis revealed that proteins associated with changes in energy usage; osmotic adjustment; ROS scavenging; and protein synthesis, processing, and proteolysis play important roles in maintaining root growth under drought stress. This study provides new insight for better understanding of the molecular basis of drought stress responses, aiming to improve plant drought tolerance for enhanced yield.

Modulation of cell cycle progression and chromatin dynamic as tolerance mechanisms to salinity and drought stress in maize.

Salinity and drought are the major abiotic stresses that disturb several aspects of maize plants growth at the cellular level, one of these aspects is cell cycle machinery. In our study, we dissected the molecular alterations and downstream effectors of salinity and drought stress on cell cycle regulation and chromatin remodeling. Effects of salinity and drought stress were determined on maize seedlings using 200 mM NaCl (induced salinity stress), and 250 mM mannitol (induced drought stress) treatments, then cell cycle progression and chromatin remodeling dynamics were investigated. Seedlings displayed severe growth defects, including inhibition of root growth. Interestingly, stress treatments induced cell cycle arrest in S-phase with extensive depletion of cyclins B1 and A1. Further investigation of gene expression profiles of cell cycle regulators showed the downregulation of the CDKA, CDKB, CYCA, and CYCB. These results reveal the direct link between salinity and drought stress and cell cycle deregulation leading to a low cell proliferation rate. Moreover, abiotic stress alters chromatin remodeling dynamic in a way that directs the cell cycle arrest. We observed low DNA methylation patterns accompanied by dynamic histone modifications that favor chromatin decondensation. Also, the high expression of DNA topoisomerase 2, 6 family was detected as consequence of DNA damage. In conclusion, in response to salinity and drought stress, maize seedlings exhibit modulation of cell cycle progression, resulting in the cell cycle arrest through chromatin remodeling.

Physiological and antioxidative responses associated with drought tolerance of Lasiurus sindicus Henr. endemic to Thar desert, India

Sewan (Lasiurus sindicus Henr.) is an endemic fodder grass of low rainfall sandy habitat of hot Indian Thar desert. To understand drought responses and tolerance mechanism in Lasiurus sindicus, seedling growth, root cell viability, changes in enzymatic antioxidants and oxidative injury were assayed at early stage of seedlings in polyethylene glycol (PEG) 6000 (5, 10 and 20%)-induced drought stress. The reduction of seed germination, seedling growth, relative water content and vigor index was found with high level of PEG (10–20%), while 5% PEG slightly increased the germination and the growth parameters. A decline in pigments (Chl a, Chl b, total Chl, carotenoids), chlorophyll stability index, membrane stability index and protein content was observed, which was correlated with increased level of malondialdehyde, an indicator of excess reactive oxygen species. Results showed that increasing level of PEG activated the antioxidative enzymes, superoxide dismutase, peroxidase and catalase. Non-enzymatic antioxidants (ascorbate, phenols) and accumulation of cytosolutes (proline and sugar) for regulation of growth, osmotic potential and reactive oxygen species in drought tolerance. Overall results showed that seeds have adaptive mechanisms for germination and growth under lower level of drought, while increasing drought stress reduced growth potential of L. sindicus. It exhibited drought tolerance features, enhancement in activity of antioxidative enzyme and cytosolutes accumulation which involved in regulation of oxidative damage and osmotic adjustment for survival of the seedlings. Furthermore, our results provide important information about the physiological and antioxidative responses of the seedlings and mechanism associated with drought tolerance of L. sindicus.

Quantifying seed germination responses of Echinops and Centaurea, to salinity and drought stresses

Seed germination may significantly interrupt by water stress due to drought and salinity condition. Salinity can cause osmotic pressure and induce drought stress. Water deficit stress affect normal seed germination and reduce seedling vigor. The objective of this investigation was to determine the effect of drought and salt stresses on germination characteristics of Echinops ritro and Centaurea virgata. Seeds were germinated with the concentrations of sodium chloride (0, 50, 100, 150 and 200 mmol) or in polyethylene glycol PEG6000 (0, -0.2, -0.4, -0.6, -0.8, -1 and -1.2 MPa). The highest values of germination parameters were obtained with no osmotic potential or salinity stress. At treatment by PEG, the germination was severely decreased at -0.6 MPa. While, no germination occurred at- 0.8 MPa by PEG. Results revealed that under 118 Mmol salinity, the seed germination of Centaurea virgata declined to 43% which was as close as half of its total seed germination. However, 50% reduction in seed germination of Echinops ritro was observed at 193 mmol salinity. Results indicated Echinops ritro and Centaurea virgata germination was sensitive to both the stresses. However, seedling growth was more sensitive to PEG than NaCl.

Differing precision irrigation thresholds for kale (Brassica oleracea L. var. acephala) induces changes in physiological performance, metabolites, and yield

Kale originates from the eastern Mediterranean and Asia Minor, being cultivated worldwide and is considered as global cash crop to high nutrients as well as cold tolerance in the fall, winter, and spring. Although kale production is gradually increasing, there is limited research on physiological and metabolism changes by different levels of irrigation. Here, we comprehensively investigated yield, metabolism, and physiological changes by different levels of precision irrigation based on soil moisture sensor. Kales were grown at three different levels of volumetric water content (VWC) which included 0.15, 0.25, or 0.35 m3 m3, corresponding to well-watered, intermediate drought, and drought stressed conditions. There was a 22.5% increase in fresh weight when comparing the 0.15 to 0.35 m3 m3 VWC treatments. Leaf transpiration (E), net CO2 assimilation rate (A), intercellular CO2 concentration (Ci), tand stomatal conductance (gs) to water vapor were significantly different between 0.15 and 0.35 m3 m3 VWC treatments. The carotenoids neoxanthin and antheraxanthin were significantly decreased when comparing the 0.15 to 0.35 m3 m3 VWC treatments. Additionally, aspartic acid and glutamate were highest concentration at 0.35 VWC, implying well-watered condition has a high assimilation capacity from nitrate and ammonium in the kale plant leaf tissue. Glycine, histidine, proline, fructose, and glucose were increased as VWC decreased, indicating that these metabolites are indicators of drought stress. Linoleic acid, and the glucosinolates glucoiberin, progoitrin, sinigrin, and total phenolic content were the highest concentration in the 0.25 m3 m3 VWC, indicating moderate drought stress may increase these specific metabolites. From the pathway analysis, drought stress significantly increased alanine, aspartate, and glutamate metabolism and glycine, serine, and threonine metabolism. Deficit irrigation that induce drought stress impacted kale plants by decreasing physiological (A, E, and gs) parameters and metabolite (carotenoids, chlorophylls) concentrations, while increase stress induced metabolites such as proline and glutamate. Thus, this study utilized a comprehensive research methodology that connects morphophysiological and biochemical metabolite information and demonstrates how kale plants may integrate growth in drought conditions.

Alleviation of drought stress and the physiological mechanisms in Citrus cultivar (Huangguogan) treated with methyl jasmonate.

The role of exogenous methyl jasmonate (MeJA) in alleviating drought stress was investigated on Huangguogan. Except for intercellular CO2 concentration, MeJA had little effect on net photosynthetic rate, stomatal conductance, and transpiration rate under drought stress. Compared with drought stress, MeJA significantly alleviated the decrease of chlorophyll content. However, chlorophyll a/b ratio was significantly increased. MeJA significantly increased proline and soluble sugar contents, significantly decreased the O2 -· and H2O2 levels, and increased SOD and POD activities. In addition, the MDA content of drought stress was the highest of all treatments. MeJA significantly reduced MDA content in drought-stressed Huangguogan leaves. Although the Ascorbic acid (AsA) contents of 500 and 1000 mg L-1 MeJA treatments were lower than that of 250 mg L-1 MeJA, but all concentration of MeJA treatments delayed the decline of AsA content. Therefore, MeJA could induce drought stress tolerance by increasing the osmotic adjustment substances and antioxidant activities.

Physiological and biochemical studies of black gram (Vigna mungo (L.) Hepper) under polyethylene glycol induced drought stress

Black gram (Vigna mungo L. Hepper) is an important nutritious legume plant, the loess plateau with strong drought tolerance and broad adaptability. To understand the adaptation mechanism of black gram under simulatedlevels of drought (5, 10 and 20% PEG) stress, and the growth characteristics, physiological parameters including levels of chlorophyll content, reactive oxygen species, and antioxidant enzymes were measured and the changes were compared with control. The result showed the root and shoot length, chlorophyll content, relative water content, stomatal activity, electrolyte leakage, antioxidant, and histochemical activity were carried out for treated and control plants. Experimentally, the drought-induced black gram seedlings of fresh weight, dry weight, and relative water contents found to be decreased with increasing concentrations of PEG. However, the electrolyte leakage and biochemical components (MDA content), antioxidant enzymes (SOD, CAT, POX), isozyme band patterns and histochemical detection of ROS accumulation (H2O2 and O2•–) level also enhanced under drought stress. The electrolyte leakage and MDA content were raised at 60% and 20% of severe PEG treatment. ROS accumulation was increased in the PEG treatment when compared to control. Overall, the rapid, accurate, and strong physiological observations from the electrolyte leakage and histochemical detection suggest that modification or enhancement of the biochemical and antioxidant contents would be determine the growth of black gram under PEG induced drought stress.

Impact of PEG Induced Drought Stress on Growth and Physiology of Fenugreek (Trigonella foenum graecum L.)

Impact of PEG Induced Drought Stress on Growth and Physiology of Fenugreek (Trigonella foenum graecum L.)

Exogenous Glutathione-Mediated Drought Stress Tolerance in Rice (Oryza sativa L.) is Associated with Lower Oxidative Damage and Favorable Ionic Homeostasis

Drought stress is a major concern for current agriculture as it limits plant growth and yield. An experiment was conducted with a drought susceptible rice (Oryza sativa L. cv. BRRI dhan29) to explore the potential functions and possible mechanisms of exogenous glutathione (GSH)-induced drought stress tolerance. Fifteen-day-old seedlings, GSH-pretreated or non-pretreated (0.2 mM GSH for 72 h), were subjected to PEG-induced (15% polyethylene glycol 6000) drought stress for 4 days. Rice plants exposed to drought stress displayed reduced growth, which was correlated with reduced chlorophyll content, water balance, antioxidant enzymes activities and mineral contents (K+, Ca2+ and Mg2+), as evidenced by principle component analysis (PCA) and heatmap clustering. The PCA also revealed that hydrogen peroxide (H2O2) and malondialdehyde (MDA) accumulations were strongly linked with the declined growth and development of rice plants under drought stress. Importantly, pretreatment with GSH improved the growth responses of rice plants to drought stress. GSH strengthened numerous physio-biochemical processes which were coupled with increased uptake of K+, Ca2+ and Mg2+, enhanced accumulation of soluble sugars, higher activities of enzymatic and non-enzymatic antioxidants. Moreover, GSH-pretreated seedlings under drought stress conditions had lower levels of O2·− , H2O2 and MDA which indicates successful adaptation of rice seedlings to drought stress. The results of PCA strongly supported that GSH conferred drought tolerance mostly by enhancing antioxidant activities and mineral homeostasis. Collectively, our findings provide an important prospect for use of GSH in modulating drought tolerance in rice plants. Breeding strategies should therefore be undertaken to increase the GSH content of rice plants as a means to increase drought tolerance.

Evaluation of sodium nitroprusside and putrescine on polyethylene glycol induced drought stress in Stevia rebaudiana Bertoni under in vitro condition

The present work aimed to regenerate Stevia rebaudiana Bertoni under in vitro drought condition induced by different concentrations (0%, 5%, 10 % and 15 %) of polyethylene glycol (PEG) 6000, and to investigate the mitigating effect of sodium nitroprusside (SNP; nitric oxide donor) and putrescine in relation to efficient multiplication. Varying concentrations of SNP (50, 100, 250 and 500 μM) and putrescine (0.05, 0.1, 0.3 and 0.5 mM), used singly or in combination in the MS medium, along with best selected concentration of plant growth regulator (kinetin 0.2 mg l−1) under in vitro drought imposed by 10 % PEG were taken for studies at 20, 40 and 60 days after inoculation (DAI). The best response with maximum values on the basis of morphological parameters was recorded; number of shoot and number of leaves were observed in half strength MS media supplemented with combination of both SNP and putrescine treatment i.e. SNP 100 μM + putrescine 0.05 mM followed by other treatments as compared to remaining treatments as well as control (10 % PEG only). On the basis of present investigation, it is concluded that in vitro drought stress significantly reduced the number of shoot, length of shoot (cm), number of leaves, number of roots, length of root (cm) and survival percentage. However, treatment with SNP and putrescine, alone or in combination, alleviated the negative impacts of drought stress up to a great extent. The production of more number of stevia leaves even under drought condition as a result of ameliorative treatment with SNP and putrescine has implication in R&D industries to target for production of maximum content of stevioside and rebaudioside, key principles in treating diabetes, if there is an increase in their content.