Antioxidant is any substance that delays, prevents or removes oxidative damage to a target molecule. This includes compounds of a non-enzymatic as well as an enzymatic nature. Antioxidant enzymes e.g., superoxide dismutase, glutathione peroxidase, and glutathione reductase, which catalyze free radical quenching reaction. Nutrient-derived antioxidants like ascorbic acid (vitamin C), tocopherols and tocotrienols (vitamin E), carotenoids and other low molecular weight compounds such as glutathione and lipoic acid are involved in neutralizing free radicals. Reactive oxygen species (ROS) occur in tissues and cells and can damage DNA, proteins, carbohydrates and lipids. The ROS comprises both free radical (O2-, superoxide radicals; OH-, hydroxyl radical; HO2-, perhydroxy radical and RO-, alkoxy radicals) and non-radical (molecular) forms (H2O2, hydrogen peroxide and 1O2, singlet oxygen). These deleterious reactions are controlled in part by antioxidants that eliminate ROS and scavenge free radicals. Various abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants which are highly reactive and toxic and cause damage to proteins, lipids, carbohydrates and DNA which ultimately results in oxidative stress. Seed priming methods have been used to increase germination characteristics under stress conditions. The beneficial effects of seed priming are associated with different physiological and biochemical changes.
