Hypoxic Induction of Anoxia Tolerance in Rice Coleoptiles

Abstract

Rice (Oryza sativa L.) seedlings were subjected to a 24-h anoxic stress after hypoxic pretreatment (H-PT) for evaluation of the hypoxic acclimation to anoxia tolerance in their coleoptiles. The elongation of the coleoptiles of the seedlings subjected to H-PT was greater than that of non-pretreated (N-PT) seedlings. During pretreatment periods, alcohol dehydrogenase (EC 1.1.1.1) and pyruvate decarboxylase (EC 4.1.1.1) activities in the H-PT coleoptiles became 5.3- and 3.6-fold greater than those in the N-PT coleoptiles, respectively. The average production rate of ethanol during the initial 6 h after the onset of the anoxia stress was 3.7 and 1.3 ★mol g^-1 fresh weight h^-1 for the H-PT and N-PT coleoptiles, respectively. Coleoptiles of the seedlings lost ATP rapidly under the anoxic stress; however, the decrease in ATP was much slower in the H-PT coleoptiles than in the N-PT coleoptiles. These results are consistent with the results found in roots of several plants, suggesting that the mechanism in hypoxic acclimation to anoxia implicated in their roots may act in the rice coleoptiles.