Abstract
Three experiments on the effects of temperature on the development of winter buds of Japanese apricots (Prunus mume Sieb. et Zucc.) and subsequent shoot growth were conducted in growth chambers and under field conditions.
1. From mid-October to mid-February, one-year-old potted seedlings and excised shoots were transferred monthly from field to the growth chamber kept at 15 °C or 25 °C to determine the end of bud dormancy. Bud dormancy of seedlings and that of excised shoots were broken by mid-December.
2. The development of leaf and flower buds of 'Nanko' cuttings were compared in growth chambers kept at 0°, 5°, 10°, 15°, 20°, and 25 °C from early January to anthesis. Flowering occurred earlier than did sprouting of leaf buds in cuttings kept at 15 °C or above. No difference was observed between dates of anthesis and sprouting of leaf buds of shoots kept at 10 °C or 5 °C. At 0 °C, flower buds did not develop fully; leaf buds sprouted but the leaves did not expand.
3. One-year-old 'Nanko' trees grafted on seedling mume rootstocks were moved on 1 March to growth chambers kept at 10°-15°, 15°, 20°, and 25 °C and held until the end of shoot growth. After sprouting of leaf buds, trees were thinned to 10 shoots per tree. The most vigorous shoot growth was observed in the 10° - 15 °C treatment, in which trees were kept at 10 °C for two months and then transferred to 15 °C. At 20° and 25 °C, shoots ceased their growth earlier than did those in lower temperature regimens.
