Optimum bulb vernalization temperature of Asiatic hybrid lilies, Lilium x elegans Thunb.

摘要

Asiatic hybrid lily, Lilium x elegans Thunb., bulbs of 'Inferno', 'Red Carpet', 'Sunray', and 'Connecticut Lemonglow' grown were forced in the greenhouse to investigate the upper limit and optimum bulb vernalizing temperature. Bulbs stored at 15 degrees C or 20 degrees C did not emerge; suggesting that upper limit for bulb vernalization was near 15 degrees C. Therefore, storing bulbs at temperatures higher than 10 degrees C is not recommended. The number of flowers was increased following optimum bulb vernalizing temperatures at 2.5 degrees C-5 degrees C. Flowering acceleration when bulbs received 1 W/2.5 degrees C-1 W/10 degrees C-6 W/2.5 degrees C depended on cultivars, however, the total number of flowers was not increased as compared to 7 W/2.5 degrees C. Shoot apices of non-emerging bulbs 'Connecticut Lemonglow' and 'Sunray' were dead or flower buds aborted with shoot intact to basal plate in 'Inferno' This suggested that, in Asiatic hybrid lilies, flower bud initiation occurs very rapidly and required a different optimum temperature depending on cultivars. Upper limit for bulb vernalization was near 15 degrees C ('Red Carpet' - RC) and 12.5 degrees C ('Connecticut Lemonglow' - CLG and 'Sunray' - SR). Flowering of 'Inferno', 'Red Carpet', 'Connecticut Lemonglow', and 'Sunray' was accelerated responding linearly to temperatures. In all four cultivars, optimum temperature for shoot emergence and flowering could be near 4.5 degrees C and the number of flower buds was the highest, indicating that optimum bulb vernalizing temperature is near 4.5 degrees C (Expt. 3). Shoot emergence and flowering in all cultivars was delayed when 1, 2, or 3 weeks of 15 degrees C was given during 6 W/2.5 degrees C and the delaying effect of 15 degrees C was significant after 2 W/2.5 degrees C as compared to that given after 1 W or 4 W/2.5 degrees C. The number of flowers, except for the total number in 'Connecticut Lemonglow' were not affected by 2.5 degrees C or 15 degrees C treatment. Based on the flowering responses in all cultivars, it is suggested that flower bud initiation could be completed after 2 W/2.5 degrees C and development of initiated flower buds are affected in 'Inferno' as judged by the number of aborted buds and therefore, alternating temperature treatments in all four cultivars did not increase the total number of flowers. The temperature (15 degrees C) used in this study may have been too high to expect high flower bud numbers. Based on these experiments, it is concluded that bulb vernalization in 'Inferno' is not required for early flowering, although is necessary for obtaining high flower bud counts. In all four cultivars, optimum bulb vernalizing temperature is near 5 degrees C in all cultivars, and upper limit of vernalizing temperatures could be higher than 12.5 degrees C which depend on cultivars. The number of flowers was not increased by alternating bulb temperature treatment, which could result from the death of bulbs or of the shoot apices.