Reactive Oxygen and Nitrogen Species: Oxidative Damage and Antioxidative Defense Mechanism in Plants under Abiotic Stress

Abstract

Plants are versatile in terms of tolerance and adaptive mechanisms toward severe abiotic stresses. The most deleterious effects of abiotic stresses are the production of highly toxic species known as reactive oxygen species (ROS) and reactive nitrogen species (RNS). These species are produced in different cellular compartments within the plant body as a by-product of metabolic processes in the form of radical and nonradical species; however, their production is amplified when plants encounter abiotic stresses. These ROS and RNS molecules at low concentration act as signaling molecules but at higher concentration enforce harsh oxidative stress damaging cell protein, lipids, and nucleic acid. Thus, homeostasis of ROS and RNS is required to maintain at optimal levels to prevent damage. Plants have antioxidant system that comprises two components, i.e., enzymatic and nonenzymatic antioxidant defense system, which maintains ROS and RNS homeostasis inside cells. Thus, there is a delicate equilibrium between ROS and RNS production, and their scavenging system inside the cell, which helps the 72plant to survive from the toxic effects of these species. In this chapter, we will be discussing ROS and RNS generation, sites of production, and their vital role in acting as messenger molecules as well as inducers of oxidative damage under various abiotic stresses. Further, this chapter will focus on the mechanism of ROS production, oxidative stress, and antioxidant defense mechanisms under several stressful environmental conditions.