Reactive Oxygen Species: Generation, Damage, and Quenching in Plants During Stress

Abstract

Reactive oxygen species (ROS) are reactive molecules formed during the normal metabolism of plants such as superoxide radical, hydrogen peroxide, hydroxyl radicals and singlet oxygen. They function as important signalling molecules in the regulation of several plant processes like growth, development and physiology. Excessive formation of ROS in plants has been reported under various biotic and abiotic stresses causing lipid peroxidation, disturbance in various biotic process, alterations in genetic material and degradation of proteins. Higher generation of ROS causes oxidative stress depending upon quenching of the plants. For efficient scavenging of ROS, plants are well equipped with several enzymatic (superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, guaiacol peroxidase and glutathione‐S‐transferase etc.) and nonenzymatic (ascorbic acid, flavonoids, phenols, carotenoids, β‐carotene, proline and ά‐tocopherols etc.) antioxidants. In the present chapter, generation of ROS under various stresses, production sites of ROS in plants, damaging effects as well as their role as a signalling molecule and their scavenging in plants through various mechanisms will be discussed.