The effects of ethanol on the germination of seeds of japonica and indica rice (Oryza sativa L) under anaerobic and aerobic conditions

An examination was made of the effects of ethanol at 0.2-6.0% (v/v) on the germination, under aerobic conditions, of intact and dehusked seeds of indica rice (cv. Assam IV), which had been harvested 14, 21 and 28 d after anthesis, and of the japonica rice (cv. Sasanishiki), which had been harvested 30 and 60 d after anthesis. The inhibition of germination caused by dehusking japonica rice was overcome by 0.5-5% ethanol, with maximum germination (frequently 100%) achieved al 3-5% (30 d after anthesis) or 1-4.5% (60 d after anthesis) ethanol. Further increases in the ethanol concentration reduced germination. The germination of dehusked indica rice was slightly inhibited at 0.5 and 1% ethanol, whilst the promotion of germination by 2% ethanol increased as the seeds matured. Al all harvests germination was greatest at 3% ethanol, and at 5-6% ethanol germination fell to 0%. Inhibition, no effect, or minimal stimulation of the germination of intact seeds of both japonica and indica rice by ethanol was observed at the concentrations examined. The absence of oxygen stimulated germination of dehusked japonica rice, but this germination was inhibited by ethanol. In contrast ethanol had little or no effect on the failure of dehusked indica seeds to germinate in anaerobic conditions. Thus ethanol treatment may help break the strong dormancy of dehusked seeds of indica and japonica rice. The possible role of ethanol in stimulating germination rice is discussed. (C) 1997 Annals of Botany Company.