Rice coleoptiles rapidly elongate when seeds germinate under submergence, but not in the alcohol dehydrogenase 1 (ADH1)-deficient mutant, reduced adh activity (rad). Takahashi et al. find that cell division as well as elongation occur during coleoptile elongation under submergence, and that both are reduced in the mutant, probably as a result of reduced ATP generation caused by the ADN1 deficiency.