Anaerobic Germination Potential in Rice (Oryza sativa L.): Role of Amylases, Alcohol deydrogenase and Ethylene

Rice is cultivated either through wet and dry direct seeding or transplanting. Under direct seeding seeds are sown in the field whereas under transplanting seedlings are planted. Though direct seeding is economical and environment friendly, it is riskier than transplanting due to soil flooding and other menaces. Anaerobic germination (AG) potential or tolerance to germination stage oxygen deficiency (GSOD) is a feature that enables rice to grow under soil flooding. In the present investigation, twenty-two rice genotypes were characterized for their AG potential / GSOD tolerance regarding different growth parameters as well as amylolytic and fermentative activities under different days of soil flooding. Significant genotypic variations were noticed for these parameters at different days of soil flooding. Differences between control and treatment were highly significant. The activities of these enzymes also varied significantly under different days of soil flooding. A-amylase and total-amylase activities showed significant positive association with seedling establishment under flooding. Alcohol dehydrogenase activity though increased under flooding, yet did not show any significant association with seedling establishment under flooding. Ethylene releasing capacity increased under flooding mainly in genotypes with greater AG potential as compared to susceptible genotypes. The correlation between ethylene releasing capacity and seedling establishment under flooding was significant. Grouping of genotypes based on seedling establishment, growth parameters, enzyme activities and stability of enzymes under flooding revealed that the genotypes with greater degrees of AG potential make a major group, which were distantly placed from highly susceptible and medium tolerant group. The data showed that to impart greater anaerobic germination potential, amylolytic activities and ethylene releasing capacity played greater role.