Antioxidant Defence System of Rice (Oryza sativa L.) Induced by Waterlogging Stress

Abstract

Waterlogging is an important abiotic stress that adversely affects plant growth, metabolism and productivity by restricting oxygen diffusion into the root zone. Rice (Oryza sativa L.) is comparatively tolerant to flooding; however, prolonged waterlogging can cause hypoxia or anoxia, impaired respiration, reduced photosynthesis, nutrient imbalance and excessive generation of reactive oxygen species (ROS). Enhanced ROS production results in oxidative stress and can damage lipids, proteins, nucleic acids and cellular membranes. Rice plants counteract this oxidative damage through a complex antioxidant defence system consisting of enzymatic and non-enzymatic components. Major antioxidant enzymes include superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR). Non-enzymatic antioxidants include ascorbate, glutathione, tocopherols, carotenoids, phenolic compounds and flavonoids. The present paper reviews the physiological and biochemical responses of rice to waterlogging, with particular emphasis on ROS generation and antioxidant defence mechanisms. Understanding these mechanisms is important for developing waterlogging-tolerant rice cultivars through conventional breeding, molecular approaches and biotechnological interventions.