Water, a necessary component of cell protoplasm, plays an essential role in supporting life on Earth; nevertheless, extreme changes in climatic conditions limit water availability, causing numerous issues, such as the current water-scarce regimes in many regions of the biome. This review aims to collect data from various published studies in the literature to understand and critically analyze plants’ morphological, growth, yield, and physio-biochemical responses to drought stress and their potential to modulate and nullify the damaging effects of drought stress via activating natural physiological and biochemical mechanisms. In addition, the review described current breakthroughs in understanding how plant hormones influence drought stress responses and phytohormonal interaction through signaling under water stress regimes. The information for this review was systematically gathered from different global search engines and the scientific literature databases Science Direct, including Google Scholar, Web of Science, related studies, published books, and articles. Drought stress is a significant obstacle to meeting food demand for the world’s constantly growing population. Plants cope with stress regimes through changes to cellular osmotic potential, water potential, and activation of natural defense systems in the form of antioxidant enzymes and accumulation of osmolytes including proteins, proline, glycine betaine, phenolic compounds, and soluble sugars. Phytohormones modulate developmental processes and signaling networks, which aid in acclimating plants to biotic and abiotic challenges and, consequently, their survival. Significant progress has been made for jasmonates, salicylic acid, and ethylene in identifying important components and understanding their roles in plant responses to abiotic stress. Other plant hormones, such as abscisic acid, auxin, gibberellic acid, brassinosteroids, and peptide hormones, have been linked to plant defense signaling pathways in various ways.

Water being a vital part of cell protoplasm plays a significant role in sustaining life on earth; however, drastic changes in climatic conditions lead to limiting the availability of water and causing other environmental adversities. α-tocopherol being a powerful antioxidant, protects lipid membranes from the drastic effects of oxidative stress by deactivating singlet oxygen, reducing superoxide radicals, and terminating lipid peroxidation by reducing fatty acyl peroxy radicals under drought stress conditions. A pot experiment was conducted and two groups of lentil cultivar (Punjab-2009) were exposed to 20 and 25 days of drought induced stress by restricting the availability of water after 60th day of germination. Both of the groups were sprinkled with α-tocopherol 100, 200 and 300 mg/L. Induced water deficit stress conditions caused a pronounced decline in growth parameters including absolute growth rate (AGR), leaf area index (LAI), leaf area ratio (LAR), root shoot ratio (RSR), relative growth rate (RGR), chlorophyll a, b, total chlorophyll content, carotenoids, and soluble protein content (SPC) which were significantly enhanced by exogenously applied α-tocopherol. Moreover, a significant increase was reported in total proline content (TPC), soluble sugar content (SSC), glycine betaine (GB) content, endogenous tocopherol levels, ascorbate peroxidase (APX), catalase (CAT) peroxidase (POD) and superoxide dismutase (SOD) activities. On the contrary, exogenously applied α-tocopherol significantly reduced the concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2). In conclusion, it was confirmed that exogenous application of α-tocopherol under drought induced stress regimes resulted in membrane protection by inhibiting lipid peroxidation, enhancing the activities of antioxidative enzymes (APX, CAT, POD, and SOD) and accumulation of osmolytes such as glycine betaine, proline and sugar. Consequently, modulating different growth, physiological and biochemical attributes.

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Water is the fundamental part of living systems and it plays a key role in supporting life on earth; however, fluctuations in climatic conditions lead to limitation of the ground water causing serious concerns. The present research study was aimed at assessing growth and physio-biochemical responses of barley to calcium chloride (CaCl2) solution (10 mM) applied through roots under induced drought stress for 5, 10, and 15 days. CaCl2 being an enhancer of osmolytes and antioxidant enzymes counteracts the damaging effects caused by abiotic stresses. A pot experiment was conducted by sowing barley under induced drought stress for 5, 10, and 15 days, respectively. Plants exposed to different levels of the induced drought stress condition were applied with 10 mM of CaCl2 solution via roots during the seedling stage. Results indicated that water-limited conditions negatively affected plant growth parameters including final emergence percentage, final germination percentage, and mean emergence time. Moreover, absolute growth rate, relative growth rate, and net assimilation rate were significantly improved under 5, 10, and 15 days of drought stress supplemented with CaCl2 solution. Under drought conditions, an increase was observed in hydrogen peroxide (H2O2), glycine betaine (GB), and proline (PRO) content, and in ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and lipid peroxide (LPO) activities. H2O2 and LPO showed a significant decline with CaCl2 application under induced drought stress regimes. On the contrary, GB, PRO, APX, CAT, POD, and SOD contents of root and leaf were significantly improved with CaCl2 application under induced drought stress. In conclusion, CaCl2 solution effectively curbed the damages caused by oxidative stress via accumulating osmolytes and scavenging reactive oxygen species by activating the antioxidant enzymatic defence system of barley.