Antioxidant-mediated defense in triggering resistance against biotic stress in plants

Abstract Reactive oxygen species (ROS) are the first line of defense incurred by any living organism against stress. Though plants do not possess specialized cells for immune responses against pathogens, ROS act as the messengers in activating the plant defense signaling. Deleterious effects of ROS are observed during plant stress, but the minimal levels of ROS are required for the plant survival, growth, and productivity. In this chapter, the aspects of plant immunity, regulation through different ROS and reactive nitrogen species (RNS), NO are reviewed. The cross talk between ROS and RNS during plant growth and development and the scavenging of redox radicals by antioxidants is also considered. The different enzymatic (SOD, APX, GPX, CAT, and MDHAR) and nonenzymatic (tocopherol and carotenoids) antioxidant roles in maintaining the homeostasis in plants, thereby triggering the defense, are also discussed.