抄録
Two experiments were performed in order to find periodic effects of low and high temperature upon the developmental responses of tobacco seedlings with different ages. The flue-cured variety, Hicks I. -2 was used in both experiments. Seedlings with 8-12 leaves were cultivated for tests in the greenhouse (16-25°C, 14 hrs. photoperiod). In experiment I, they were exposed to low temperature (13°C) for 10, 15, 20 and 25 days under long-day condition. Then they were transferred to the greenhouse maintaind at 20±3°C. Relation between age of seedlings and their vernalization was examined. In experiment II, seedlings were subjected to low temperature (15°C) interrupted by high temperature (30°C) for 3.5 hrs. in daytime under long-day condition. Then devernalization by means of high temperature was investigated. The longer the period of low temperature, the earlier the floral initiation. Seedlings with more number of leaves responded rapidly to low temperature and the difference in the response among seedlings with different ages was remarkable when they were treated for shorter days. High temperature given for a short time prolonged the floral initiation of tobacco seedlings. Difference in the developmental responses among 9th to 12th leaf seedlings was remarkable in plants encountered with the treatment of high-temperature-interruption after a low-temperature-treatment for 15 days.
