Varied Responses and Tolerant Mechanisms towards Salinity Stress in Plants

Abstract

Among several abiotic stresses, which retard crop production on at least 1/5th of irrigated land worldwide, high saline conditions seems to be the most severe environmental stress. The plant can reveal the effects of salinity at any of its life cycle stage viz. germination, seedling, vegetative or maturity. However, the response can vary for different plants on a given salt concentration and consists of numerous morphological, physiological, biochemical and molecular changes which function in a well coordinated way to alleviate toxicity. The reduction in growth and yield of crop plant may be attributed to the production of Reactive Oxygen Species (ROS), nutrient ion and osmotic imbalance, ion toxicity which is due to the accumulation of Na+ and Cl- ions under continuous exposure of plant to saline conditions. Moreover, varied biochemical phenomenon viz. change in proteins, enzymes expression level, chlorophyll and amino acids content etc. can also be observed in these crops. However, the plants may evade themselves with three different mechanisms i.e. osmotic stress tolerance, Na+ or Cl- exclusion, and by means of tissue tolerance to sodium and chloride ions. Under high salinity stress, products of enhanced activities of multiple genes encode osmolytes, ion channels, receptors, components of calcium signaling, and some other regulatory signaling factors or enzymes which enable the plant then to tolerate high salinity stress.