Relative proportion of antioxidative enzyme activity in locally grown Indian rice cultivars (Oryza sativa L.) under submergence condition

Breeders are trying to develop true submergence-tolerant genotypes for lowland irrigated and/or rainfed areas, where rice is often affected by short-term submergence. This study was conducted to evaluate the submergence tolerance, response of antioxidative defense systems to hypoxic and re-aerated conditions, and growth and survival percentage among 19 rice genotypes. The rice seedlings submerged into concrete tanks for 10 days exhibited decreased activities of antioxidant enzymes. The antioxidant enzymes, superoxide dismutase, catalase, and ascorbate peroxidase increased, whereas polyphenol oxidase and glutathione reductase decreased in subsequent re-aerated situation in tolerant genotypes. On the other hand, the activities of enzymes decreased greatly in susceptible genotypes under hypoxic and re-aerated conditions. Complete submergence of the seedling increased the plant height of 12 genotypes. However, it decreased the dry matter production. Genotypes having better root and shoot growth maintained higher dry weight and exhibited better survival than did others. The results indicated that genotypes tolerant of flash flood maintained higher activities of antioxidant enzymes and dry matter accumulation to protect against postanoxic injury.