Oxidative Stress and Antioxidant Defense System in Plants.

Abstract

Living organisms especially plants are exposed to different types of biotic and abiotic stresses. Plants actively produce reactive oxygen species (ROS) as signaling molecules to control processes such as programmed cell death, pathogen defense and abiotic stress response. Oxidative stress occurs when there is serious imbalance in any cell compartment between production of ROS and antioxidant defense. The reactive oxygen species influences on degeneration of nucleus DNA and break the DNA and cause mutation. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Plants, however, possess an impressive array of defense mechanisms against oxidative stress including the enzymatic and non-enzymatic antioxidant systems. The antioxidant enzymes include superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), while the non-enzymatic antioxidants include water soluble (ascorbate, glutathione, phenolic compounds and flavonoids) and lipid soluble (-tocopherol, -carotene, lycopene) metabolites.