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 intactand dehusked seeds of indica rice (cv. Assam IV), which hadbeen harvested 14, 21 and 28 d after anthesis, and of the japonicarice (cv. Sasanishiki), which had been harvested 30 and 60 dafter anthesis. The inhibition of germination caused by dehuskingjaponica rice was overcome by 0.5–5% ethanol, with maximumgermination (frequently 100%) achieved at 3–5% (30 d afteranthesis) or 1–4.5% (60 d after anthesis) ethanol. Furtherincreases in the ethanol concentration reduced germination.The germination of dehusked indica rice was slightly inhibitedat 0.5 and 1% ethanol, whilst the promotion of germination by2% ethanol increased as the seeds matured. At all harvests germinationwas greatest at 3% ethanol, and at 5–6% ethanol germinationfell to 0%. Inhibition, no effect, or minimal stimulation ofthe germination of intact seeds of both japonica and indicarice by ethanol was observed at the concentrations examined.The absence of oxygen stimulated germination of dehusked japonicarice, but this germination was inhibited by ethanol. In contrastethanol had little or no effect on the failure of dehusked indicaseeds to germinate in anaerobic conditions. Thus ethanol treatmentmay help break the strong dormancy of dehusked seeds of indicaand japonica rice. The possible role of ethanol in stimulatinggermination in rice is discussed. Rice; Oryza sativa L.; seed germination; dehusking treatment; ethanol; indica; japonica; oxygen; dormancy; germination inhibition; seed formation