Submergence tolerance and ethanolic fermentation in rice coleoptiles

The relationship between coleoptile elongation and ethanolic fermentation was investigated in Five cultivars of germinating rice (Oryza saliva L.) seeds submerged for 48 h under anoxia. The coleoptile elongation of all cultivars was suppressed by the submergence stress, but their elongation relative to that of respective non-stressed control was the greatest in cv. Yukihikari followed in order by Nipponbare, Kinuhikari, Koshihikari and Sasanishiki. During the stress, alcohol dehydrogenase activity and ethanol concentration in the coleoptiles of all cultivars were increased. The increased activity and concentration were the greatest in Yukihikari followed by the other cultivars in the same order as above. The ethanol concentration in the stressed coleoptiles of Five cultivars closely correlated with their coleoptile elongation. These results confirm that the ability to increase ethanolic fermentation may play an important role in the coleoptile elongation under the submergence stress condition.