GENOTYPE DIFFERENCE IN RICE POSTGERMINATION GROWTH UNDER HYPOXIA

Rice (Oryza sativa L.) genotypes that can establish seedlings in flood ed anaerobic soil had longer coleoptile in postgermination growth than other genotypes (controls) in a gas flow of N-2 and air, or under var ious degrees of hypoxia created in closed flasks in the dark. The tole rant genotypes produced as much or more ethylene than the control geno types, although both had the same activity of ethylene-forming enzyme. Ethylene stimulated coleoptile elongation of both genotypes to the sa me degree. The coleoptile elongation of the tolerant genotypes remaine d greater than that of the controls even in the presence of Co2+ and L -alpha-(2-aminoethoxyvinyl)glycine. Thus, the longer coleoptile of the tolerant genotypes might be explained by a mechanism that is independ ent of ethylene and O-2. Mesocotyl and shoot elongation of the toleran t genotypes was more stimulated by ethylene than that of control genot ypes. These developmental characteristics of tolerant genotypes may ac celerate seedling establishment in flooded anaerobic soil.