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Susceptibility of plants to abiotic stresses, including extreme temperatures, salinity and drought, poses an increasing threat to crop productivity worldwide. Here the droughtinduced response of maize was modulated by applications of methyl jasmonate (MeJA) and salicylic acid (SA) to seeds prior to sowing and to leaves prior to stress treatment. Pot experiments were conducted to ascertain the effects of exogenous applications of these hormones on maize growth, physiology and biochemistry under drought stress and wellwatered (control) conditions. Maize plants were subjected to single as well as combined pre-treatments of MeJA and SA. Drought stress severely affected maize morphology and reduced relative water content, above and below-ground biomass, rates of photosynthesis, and protein content. The prolonged water deficit also led to increased relative membrane permeability and oxidative stress induced by the production of malondialdehyde (from lipid peroxidation), lipoxygenase activity (LOX) and the production of H 2 O 2 . The single applications of MeJA and SA were not found to be effective in maize for drought tolerance while the combined pre-treatments with exogenous MeJA+SA mitigated the adverse effects of drought-induced oxidative stress, as reflected in lower levels of lipid peroxidation, LOX activity and H 2 O 2 . The same pre-treatment also maintained adequate water status of the plants under drought stress by increasing osmolytes including proline, total carbohydrate content and total soluble sugars. Furthermore, exogenous applications of MeJA+SA approximately doubled the activities of the antioxidant enzymes catalase, peroxidase and superoxide dismutase. Pre-treatment with MeJA alone gave the highest increase in drought-induced production of endogenous abscisic acid (ABA). Pre-treatment with MeJA+SA partially prevented drought-induced oxidative stress by modulating levels of osmolytes and endogenous ABA, as well as the activities of antioxidant enzymes. Taken together, the results show that seed and foliar pre-treatments with exogenous MeJA and/or SA can have positive effects on the responses of maize seedlings to drought.

This research was designed to elucidate the role of exopolysaccharides (EPS) producing bacterial strains for the amelioration of drought stress in wheat. Bacterial strains were isolated from a farmer’s field in the arid region of Pakistan. Out of 24 isolated stains, two bacterial strains, Bacillus subtilis (Accession No. MT742976) and Azospirillum brasilense (Accession No. MT742977) were selected, based on their ability to produce EPS and withstand drought stress. Both bacterial strains produced a good amount of EPS and osmolytes and exhibited drought tolerance individually, however, a combination of these strains produced higher amounts of EPS (sugar 6976 µg/g, 731.5 µg/g protein, and 1.1 mg/g uronic acid) and osmolytes (proline 4.4 µg/mg and sugar 79 µg/mg) and significantly changed the level of stress-induced phytohormones (61%, 49% and 30% decrease in Indole Acetic Acid (IAA), Gibberellic Acid (GA), and Cytokinin (CK)) respectively under stress, but an increase of 27.3% in Abscisic acid (ABA) concentration was observed. When inoculated, the combination of these strains improved seed germination, seedling vigor index, and promptness index by 18.2%, 23.7%, and 61.5% respectively under osmotic stress (20% polyethylene glycol, PEG6000). They also promoted plant growth in a pot experiment with an increase of 42.9%, 29.8%, and 33.7% in shoot length, root length, and leaf area, respectively. Physiological attributes of plants were also improved by bacterial inoculation showing an increase of 39.8%, 61.5%, and 45% in chlorophyll a, chlorophyll b, and carotenoid content respectively, as compared to control. Inoculations of bacterial strains also increased the production of osmolytes such asproline, amino acid, sugar, and protein by 30%, 23%, 68%, and 21.7% respectively. Co-inoculation of these strains enhanced the production of antioxidant enzymes such as superoxide dismutase (SOD) by 35.1%, catalase (CAT) by 77.4%, and peroxidase (POD) by 40.7%. Findings of the present research demonstrated that EPS, osmolyte, stress hormones, and antioxidant enzyme-producing bacterial strains impart drought tolerance in wheat and improve its growth, morphological attributes, physiological parameters, osmolytes production, and increase antioxidant enzymes.

Drought is an important abiotic stress that limits the plant growth and productivity. Present investigation was aimed that plant growth-promoting rhizobacteria (PGPR) isolated from moisturestressed area impart drought tolerance in plants and tryptophan may improve their efficiency. Pseudomonas sp. (1), Bacillus cereus and Bacillus pumilus (B. pumilus) were isolated from maize rhizosphere grown in irrigated fields, semi-arid region and arid region, respectively. Proteus sp. and Pseudomonas sp. (2) were isolated from rice rhizosphere grown in irrigated fields and raised bed. B. pumilus produced 5× more abscisic acid (ABA) in culture media than Pseudomonas sp. (1) by the addition of L-tryptophan. These inoculants also modulated the phytohormone content of maize leaves in a pot experiment. Higher ABA was produced by the application of B. pumilus and Pseudomonas sp. (2), while indole 3-acetic acid and gibberellic acid were found higher in Pseudomonas sp. (1) and Proteus sp. treated plants. Addition of L-tryptophan increased the concentration of all phytohormones in soil and leaves of maize. Maximum increase in relative water content, osmotic potential, protein content and photosynthetic pigments was recorded in B. pumilus treated maize plants. Under irrigated condition, response of Pseudomonas sp. coinoculated with B. pumilus from arid field superseded while under drought stress the effect of later predominated. Bacillus pumilus can be used in the formulation of biofertilizer to alleviate drought stress in arid and semi-arid regions. ARTICLE HISTORY

Drought stress is a major limitation in enhancing agricultural productivity to fulfill the food demand for the world's population. Fertigation of plants with a variety of biochemicals is being used to create drought resistance in wheat; however, the previous work has been limited in addressing these issues in plants at different growth stages.Therefore, a greenhouse study was conducted to ameliorate the drought stress in two wheat varieties (Chakwal-50 and Faisalabad-2008) by foliar application of 24-epibrassinolide (EBL). It was evident that drought stress had a negative effect on the growth, photosynthesis, and yield of wheat plants. EBL significantly enhanced the plant growth both under optimal and drought conditions. EBL improved the plant height, spike length, and the dry weights of roots, shoots, and grains as compared to control. Furthermore, the foliar application of EBL positively enhanced the osmolyte accumulation, increased the amounts of photosynthetic pigments, and improved the gas exchange parameters. The EBL minimized the oxidative stress by reducing electrolyte leakage, malondialdehyde, and hydrogen peroxide contents whereas it enhanced the activities of antioxidant enzymes, such as catalase, superoxide dismutase, and peroxidase under drought stress. The EBL significantly improved the level of stress hormones, such as abscisic acid, indol acetic acid, and cytokinin under drought stress. The growth response of Chakwal-50 was higher than that of Faisalabad-2008 when exposed to EBL under drought stress. Overall, the EBL plays a major role in the enhancement of growth, biomass, yield, and decrease in oxidative damage in wheat under drought conditions, however; field investigations with different doses of EBL are needed before any further recommendation. | INTRODUCTIONFood security is a global issue for the development of sustainable agriculture. In the present scenario, the shortage of freshwater required for agriculture has created serious problems for the production of crops with better nutritional quality in near future (Ali et al., 2019a).

Salt stress is one of the devastating factors that hampers growth and productivity of soybean. Use of Pseudomonas pseudoalcaligenes to improve salt tolerance in soybean has not been thoroughly explored yet. Therefore, we observed the response of hydroponically grown soybean plants, inoculated with halotolerant P. pseudoalcaligenes (SRM-16) and Bacillus subtilis (SRM-3) under salt stress. In vitro testing of 44 bacterial isolates revealed that four isolates showed high salt tolerance. Among them, B. subtilis and P. pseudoalcaligenes showed ACC deaminase activity, siderophore and indole acetic acid (IAA) production and were selected for the current study. We determined that 10 6 cells/mL of B. subtilis and P. pseudoalcaligenes was sufficient to induce tolerance in soybean against salinity stress (100 mM NaCl) in hydroponics by enhancing plant biomass, relative water content and osmolytes. Upon exposure of salinity stress, P. pseudoalcaligenes inoculated soybean plants showed tolerance by the increased activities of defense related system such as ion transport, antioxidant enzymes, proline and MDA content in shoots and roots. The Na + concentration in the soybean plants was increased in the salt stress; while, bacterial priming significantly reduced the Na + concentration in the salt stressed soybean plants. However, the antagonistic results were observed for K + concentration. Additionally, soybean primed with P. pseudoalcaligenes and exposed to 100 mM NaCl showed a new protein band of 28 kDa suggesting that P. pseudoalcaligenes effectively reduced salt stress. Our results showed that salinity tolerance was more pronounced in P. pseudoalcaligenes as compared to B. subtilis. However, a detailed study at molecular level to interpret the mechanism by which P. pseudoalcaligenes alleviates salt stress in soybean plants need to be explored.

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Barley ( Hordeum vulgare L.) is a major cereal grain and is known as a halophyte (a halophyte is a salt-tolerant plant that grows in soil or waters of high salinity). We therefore conducted a pot experiment to explore plant growth and biomass, photosynthetic pigments, gas exchange attributes, stomatal properties, oxidative stress and antioxidant response and their associated gene expression and absorption of ions in H. Vulgare . The soil used for this analysis was artificially spiked at different salinity concentrations (0, 50, 100 and 150 mM) and different levels of ascorbic acid (AsA) were supplied to plants (0, 30 and 60 mM) shortly after germination of the seed. The results of the present study showed that plant growth and biomass, photosynthetic pigments, gas exchange parameters, stomatal properties and ion uptake were significantly ( p < 0.05) reduced by salinity stress, whereas oxidative stress was induced in plants by generating the concentration of reactive oxygen species (ROS) in plant cells/tissues compared to plants grown in the control treatment. Initially, the activity of antioxidant enzymes and relative gene expression increased to a saline level of 100 mM, and then decreased significantly ( P < 0.05) by increasing the saline level (150 mM) in the soil compared to plants grown at 0 mM of salinity. We also elucidated that negative impact of salt stress in H. vulgare plants can overcome by the exogenous application of AsA, which not only increased morpho-physiological traits but decreased oxidative stress in the plants by increasing activities of enzymatic antioxidants. We have also explained the negative effect of salt stress on H. vulgare can decrease by exogenous application of AsA, which not only improved morpho-physiological characteristics, ions accumulation in the roots and shoots of the plants, but decreased oxidative stress in plants by increasing antioxidant compounds (enzymatic and non-enzymatic). Taken together, recognizing AsA's role in nutrient uptake introduces new possibilities for agricultural use of this compound and provides a valuable basis for improving plant tolerance and adaptability to potential salinity stress adjustment.