AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com *Corresponding author’s e-mail: go87muthu@gmail.com 1 Tamil Nadu Open University, Chennai- 600 015, Tamil Nadu, India. Role of antioxidant in seed quality- A review M. Govindaraj, P. Masilamani*, V. Alex Albert and M. Bhaskaran 1 Agricultural Engineering College and Research Institute, Tamil Nadu Agriculture University., Kumulur-621 712, Tiruchirappalli, Tamil Nadu, India. Received: 05-01-2017 Accepted: 17-08-2017 DOI:10.18805/ag.v38i03.8977 ABSTRACT 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 (O 2- , superoxide radicals; OH-, hydroxyl radical; HO 2 -, perhydroxy radical and RO-, alkoxy radicals) and non-radical (molecular) forms (H 2 O 2 , hydrogen peroxide and 1 O 2 , 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. Key words: Antioxidant, Germination, Seed treatment, Seedling vigour An antioxidant is ‘any substance that, when present at low concentrations compared with that of an oxidizable substrate, significantly delays or inhibits oxidation of that substrate’. This definition includes compounds of a non- enzymatic as well as an enzymatic nature. Clearly, the diversity of antioxidants matches that of pro-oxidants (Halliwell and Gutteridge. 1989). Free radicals are atoms, molecules or ions with unpaired electrons, which are highly reactive to chemical reactions with other molecules. In the biology system, the free radicals are often derived from oxygen, nitrogen and sulphur molecules. These free radicals are parts of groups of molecules called reactive oxygen species (ROS), reactive nitrogen species (RNS) and reactive sulphur species (RSS) viz., superoxide anion (O 2 ), perhydroxyl radical (HO 2 ), hydroxyl radical (OH), nitric oxide and other species such as hydrogen peroxide (H 2 O 2 ), singlet oxygen (1 O 2 ), hypochlorous acid (HOCl) and peroxynitrite (ONOO) (Vajragupta et al., 2004). RNS are derived from nitric oxide through the reaction with O 2 to form ONOO. RSS are easily formed from thiols by reaction with ROS (Giles and Jacob, 2002). ROS are produced during cellular metabolism and functional activities and have important roles in cell signaling, apoptosis, gene expression and ion transportation. However, excessive amounts of ROS can have deleterious effects on many molecules including protein, lipid, RNA and DNA since they are very small and highly reactive. ROS can attack bases in nucleic acids, amino acid side chains in proteins and double bonds in unsaturated fatty acids, in which OH is the strongest oxidant. ROS attacking macromolecules is often termed as oxidative stress. Cells are normally able to defend themselves against ROS damage through the use of intracellular enzymes to keep the homeostasis of ROS at a low level. In this paper discussed antioxidants sources, classification, role its mechanism and its influence on seed quality. Role of antioxidants in preventing oxidative damage: Antioxidant protects and prevents oxidative deterioration of lipids and maintains structural and functional integrity of cells. Plants possess very efficient scavenging systems for reactive oxygen species that protect them from destructive oxidative senescence. Antioxidants are the substances that even when present in low concentration effectively protects the cell membrane against the oxidative damage induced by oxidants. The class of antioxidants and their role is presented in Table 1. Enzymatic antioxidants i. Superoxide dismutase (SOD): The first enzyme involved in the antioxidant defense is the superoxide dismutase, a metalloprotein found in both prokaryotic and eukaryotic cells Agricultural Reviews, 38(3) 2017 : 180-190 Print ISSN:0253-1496 / Online ISSN:0976-0539