Physiological response of primed rice seeds to submergence at seed germination and seedling growth

Submergence plays an important role in management of weeds in the early stage of the rice, but it hinders the crop establishment in Direct-Seeded Rice (DSR). Seed priming techniques are employed to achieve efficient crop establishment in DSR despite submergence. However, performance of primed rice seeds under submergence has not been well studied. Then, the influence of seed hydro-priming duration (0, 24, 36 and 48 hours) on seed germination, seedling growth of rice and related physiological factors under different submerged depth (0, 1 and 5 cm) was studied using the rice variety IR64. Seed germination and seedling vigor, growth and survival were assessed at 5, 7, 10, 14 and 21 Days After Sowing (DAS). Lipid peroxidation was assayed in dry seeds and amylase activity and soluble sugar concentration were assayed in germinating seeds at 4 DAS. Seed priming treatments improved the seed germination by 79%, seedling vigor and survival by more than two fold under submerged conditions. Overall, the 36-hours appeared to be the best hydro-priming duration for rice. Priming significantly reduced the Malondialdehyde (MDA) content of dry seeds and MDA content correlated negatively (r=-0.86) with seedling survival under submergence. Priming increased the total amylase activity by 18-fold and alpha amylase by 6-fold under submerged conditions at 4 DAS. Further, priming significantly improves the soluble sugar concentration of germinating seeds at 4 DAS under flooding. Seed priming improved the physiological traits associated with flooding during germination such as, germination, growth, vigor, survival and carbohydrates metabolism. Therefore, IR64 rice genotype with seed priming for 24, 36 and 48 hours could be used to improve the germination, seedling vigor, emergence and survival under flooding conditions.