ストックの作付体系に関する研究 (第6報)

Abstract

Effects of low temperatures on flower bud initiation and blooming of common stock plants were studied. Low temperature treatments were conducted at early stages of plant growth. The results obtained are summarized as follows.1. When common stock plants were grown within low temperature regimes with a daily minimum temperature of 0°C during the period from the 5th day after seed planting to blooming, the number of nodes to inflorescence was fewer in early flowering cultivars than in late flowering cultivars of branching stocks. In nonbranching common stocks, however, there was only a little difference in number of nodes to inflorescence among extremely early, early, and medium flowering cultivars, thus the node number of a late flowering cultivar‘Awanoharu’was the largest among the cultivars examined. Concerning the cultivars examined, it can be concluded that the fewer the number of nodes to inflorescence, the smaller the number of days from seed planting to the flower-budding.2. Common stock plants, which had previously been grown at temperatures higher than 18°C from seed planting to each of the cotyledon-, 2-, 4-, 6-, 8-, and 10-unfolded-leaf stages, were transferred to low temperature regimes with either a daily minimum temperature of 1°C or 4°C. In most cultivars of the branching and non-branching common stocks, except the extremely early cultivar, it was observed that the earlier the beginning of low temperature treatment, the fewer the number of nodes to inflorescence.3. Common stock plants, which had previously been grown at temperatures higher than 18°C from seed planting to the 10-unfolded leaf stage, were transferred to low temperature regimes with a daily minimum temperature of 4°C for 0, 10, 20, 30, and 40 days, and then transferred further to high temparature regimes with a daily minimum temperature of 18°C. The shortest duration of low temperatures necessary for 100% blooming was 10 days in medium flowering cultivars of branching stocks and in early and medium flowering cultivars of non-branching stocks, 20 days in late flowering cultivars of branching stocks, and 40 days in late flowering cultivars of non-branching stocks.In every cultivar, high percentages of blooming occurred only in cases where flower buds thoroughly differentiated before the end of the low temperature treatment.