Role of salicylic acid in the regulation of physiological and molecular aspects of plants under abiotic stress

Salicylic acid (SA) is a natural endogenous phenolic signaling molecule involved in the physiological and biochemical processes of plants. It is produced from amino acid (chorismite or phenylalanine) which stimulates the defense-associated pathways under stressed conditions. SA plays an essential role in alleviating abiotic stresses in plants by regulating SA-mediated defensive genes, accumulation of metabolites, redox homeostasis, and enhancing photosynthetic yield. Molecular studies reported the regulation of osmolytes, genes, antioxidative defense enzymes, heat shock proteins, pathogenesis-related proteins, and other metabolites in SA-supplemented plants under abiotic stress. Both exogenous and endogenous applications of SA enhanced the tolerance in plants against temperature, drought, salt, and metal stress by reducing the production of reactive oxygen species. This chapter documents the direct or indirect role of SA in reducing the concentration of toxic metals and other abiotic stresses via activation of the defense system.