Abstract
In the previous paper the author has reported the fact that the rice coleoptile elongates more rapidly and more extensively under anaerobic condition than in aerobic conditions. The reason, however, why the coleoptiles of rice plants are capable of growing even under anaerobic conditions is not definitely understood. The present experiment was undertaken to prove the effect of anaerobic conditions on the elongation of coleoptiles, and activities of enzymes in rice plants. Rice seed can be germinated and grown for 15 to 20 days competely submerged under water. If the water is aerated, shoot and root growth are stimulated. Elongation of coleoptile is inversely related to oxygen supply, and also the elongation is retarded by using a metabolic inhibitor (NaF). The activity of alcohol dehydrogenase can be inhibited by NaF, or oxygen supply. Aeration, therefore, redues alcohol dehydrogenase activity by decreased enzyme synthesis, not by inactivation of the enzyme by oxidation. Increased alcohol dehydrogenase activity resulting from ethanol addition to germinating rice seeds under anaerobic conditions suggests rice plant alcohol dehydrogenase is an adaptive enzyme. From the results of these experiments, it may certainly be stated, that the growth of rice coleoptile under anaerbic conditions has a close connection with the alcohol dehydrogenase in geminating seeds, but has not a direct connection with the amounts of alcohol in germinating rice seeds under anaerobic conditions.
