Exogenously Applied Potassium Enhanced Morpho-Physiological Growth and Drought Tolerance of Wheat by Alleviating Osmotic Imbalance and Oxidative Damage

Water availability is the most important aspect of plant growth and development, which has an impact on crop yield and productivity. Plants respond to water shortages by altering their physiology, biochemistry, and osmotic balance. This study aimed to evaluate the role of K applications on wheat performance under water stress. The study was comprised of five levels of potassium applications, i) NK = control-no K applied, ii) WA = water applications at the heading stage (50 DAS), iii) K-50 = 50 mg L-1, iv) K-100 = 100 mg L-1, and v) K-150 = 150 mg L-1, and two levels of water status viz. i) WS0 = Control-no Water stress and ii) WS1 = Water stress (50 DAS). Results revealed that plant height, leaf area, and dry weights were decreased by 29.3, 20.8 and 23.3%, respectively, under water stress due to the reduction in the photosynthetic pigments in plants. Alternatively, cell membrane injuries were increased along with the overproduction of malondialdehyde and hydrogen peroxide. However, the production of metabolites (soluble proteins and phenolics), and antioxidant enzymes (superoxide dismutase, catalase, protease, and peroxidase) regulate plant defense. The K supplementation ameliorated the harmful effect of water stress as proved by improving plant growth attributes, leaf area and dry weight, and chlorophyll contents. In addition, the production of antioxidant enzymes and metabolites contents were increased under K applications which improved stomatal conductance and photosynthetic rate by 38.4 and 12.8%, respectively resulting in the grain yield increase of 25.3%. Among the different K levels, K applied at 150 mg L-1 was the most effective as compared to 50 mg L-1 and 100 mg L-1, which increased the seed yield by 29.5% as compared to the control. In crux, K applications have an important role to impart water stress tolerance in wheat plants based on the improvements in plant physicochemical activities.