General Characteristics of Bud Dormancy in the Vine

1. Changes in the intensity of bud dormancy was investigated using cuttings taken from a vineyard or potted vine at certain intervals during autumn and winter. Bud dormancy was deep at the beginning of autumn, but the intensity gradually decreased during a period from late autumn through early winter. 2. The state of such a dormancy was classified into three phases, i. e. conditional, spontaneous, and enforced dormancy, as proposed by Kondo. Spontaneous dormancy was the phase in which cuttings would not burst within 20 days at a favorable temperature, and the dormancy was deepest, the cuttings did not burst in about 70 days at such a temperature. Enforced dormancy was the phase following spontaneous dormancy, and the buds would not still burst in fields, while readily burst if exposed to a warm temperature. 3. The process of the onset of dormancy differed greatly among the positions of apical buds on the shoot. The intensity of dormancy was low in the buds of shoot compared to the basal ones. The onset of breaking period coincided with the beiginning of defoliation. 4. The starch content increased from 60 to 150 mg/g.fw in shoot and from 80 to 100 mg/g.fw in bud as the dormancy became deeper, while it decreased to 90 mg/g.fw in shoot and 60 mg/g.fw in bud during the breaking period. On the contrary, the sugar content in both tissues was kept at a constant level (20 mg/g• fw) during the period of deep dormancy, and increased up to 40 mg/gfw during the breaking period. 5. The endogenous inhibitors present in the shoots carrying dormant buds appeared in Rf 0.6-0.9 (Q-inhibitor zone) when the extract from acid ethyl acetate fraction was spotted on a paper chromatogram and developed in a solvent system, isopropanol : ammonia : water=l0 : 1 : 1(v/v). These substances inhibited the growth of avena coleoptile, germination of Raphanus seed, the growth of rice seedling, namylase activity in Avena endosperm, and germination of vine buds. 6. This inhibitory activity was correlated to the onset or breaking of bud dormancy. When further analysed using thin-layer chromatography in four solvent systems and gas-liquid chromatography, it was clarified that ABA was contained in these inhibiting substances.