Salt stress, its impacts on plants and the strategies plants are employing against it: A review

Abstract

Salt stress is said as the most harmful environmental issue affecting the agricultural productivity of many crops, with deleterious effect on plant growth, physiological and biochemical characteristics, vigour, and crop yields. Salt stress induced oxidative stress in plants by generating reactive oxygen species (ROS) that results impairment of cellular membranes, proteins of cells and organelles, especially of mitochondria, chloroplast, and peroxisomes and affects overall integrity of the cell. The various types of ROS are1O2, H2O2, O2•−, and OH•. Salinity creates osmotic stress in plants that diminishes the root water absorption capacity and causes loss of water from the leaves that increases the accumulation of salts in salt stressed plants. However, plants show tolerance toward salt stress by involving large number of adaptations, for example, osmotic adjustment, ion homeostasis, hormonal regulation, antioxidant defense system, etc. Biosynthesis of plant growth hormones, such as cytokinins, abscisic acid, auxin, jasmonic acid, gibberellin, and ethylene play important role in amelioration of salt stress in plants by altering biochemical and physiological process plant tissues. Plants develop ion homeostasis in order to eliminate additional salt ions from cytosol by primary and secondary transport, maintains the balance of cytosolic concentration of Na+ and K+ ions, thus keeps the low concentration of Na+ ions in cytosol as they are very harmful to cell when present in higher level. Plants develop antioxidant system constituting enzymatic components catalase, glutathione peroxidase, superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, and glutathione reductase and non-enzymatic components, such as glutathione, cysteine, tocopherols, and ascorbate that eliminate or neutralize ROS to cope with the oxidative stress by the antioxidant defense system and protect themselves against detrimental effects of ROS. In this review, we discuss on salt stress lead production of ROS, their formation, effects, and scavenging.