Application of Salicylic Acid Increases Contents of Nutrients and Antioxidative Metabolism in Mungbean and Alleviates Adverse Effects of Salinity Stress

Salicylic acid (SA), a naturally occurring plant hormone, is an important signal molecule known to have diverse effects on biotic and abiotic stress tolerance. Its growth-promoting effect on various plants has been shown, but the information on the response of mungbean, an important leguminous plant, to SA application under salt stress is limited. Mungbean (Vigna radiata L.) cultivar Pusa Vishal plants grown with 50 mM NaCl were sprayed with 0.1, 0.5, or 1.0 mM SA and basic physiological processes were studied to substantiate our understanding of their role in tolerance to salinity-induced oxidative stress and how much such processes are induced by SA application. Treatment of plants with 0.5 mM SA resulted in a maximum decrease in the content of Na⁺, Cl⁻, H₂O₂, and thiobarbituric acid reactive substances (TBARS), and electrolyte leakage under saline conditions compared to the control. In contrast, this treatment increased N, P, K, and Ca content, activity of antioxidant enzymes, glutathione content, photosynthesis, and yield maximally under nonsaline and saline conditions. The application of higher concentration of SA (1.0 mM) either proved inhibitory or was of no additional benefit. It was concluded that 0.5 mM SA alleviates salinity-inhibited photosynthesis and yield through a decrease in Na⁺, Cl⁻, H₂O₂, and TBARS content, and electrolyte leakage, and an increase in N, P, K, and Ca content, activity of antioxidant enzymes, and glutathione content.