Studies on the forcing of Aster savatieri Mak. var. hort. Mak. XI

Abstract

This study was carried out to clarify flower bud differentiation in Aster savatieri Mak. and the development as affected by temperature, photoperiod and some environmental factors in high land.1. To clarify the flower bud differentiation and the development of two different sizes of suckers, 100 plots which consisted of combinations such as five different temperatures (2°, 5°, 10°, 15° and 20°C), two different daylengths (8 and 24 hours with natural diffused light and artificial light), and five different treatment durations (1, 3, 4, 5 and 6 weeks) were made. And two different sizes of suckers (small size with 4 to 5 leaves and large size with 7 to 8 leaves) were used in this test.2. The flower bud were differentiated when the suckers had been grown at 10° and 15°C for three weeks, and 5°C for four weeks, however, the suckers grown at 2° and 20°C for 6 weeks showed no flower bud differentiation.The period for flower bud differentiation of the suckers treated with 10°C was shorter than that with 15°C.3. The large suckers were more effectively influenced by low temperatures than the small ones.The sensitivity of the plants for flower bud differentiation varies by sizes of the sucker, photoperiod and especialy, temperature.4. To clarify the effect of environmental factors in high land on flower bud differentiation and development, an experiment was made, by combining two different altitudes (about 750 and 1, 000 meters), three different planting dates (Aug. 3, 14 and 25, ′65) and three different light intensities (about 36, 60 and 100%).Flower bud differentiation and the development was accelerated when the suckers were grown at about 1, 000 meters above sea level. Moreover, the flower bud differentiation and the development of suckers planted in the nursery bed of high land on August 3 were more acceleratively influenced than those on Aug. 14 and 25. And the flower bud differentiation and the development were accelerated when the suckers received the light intensities of 36 to 60% of full sunlight, when they were grown at about 1, 000 meters above sea level, however they were not accelerated when grown at about 750 meters above sea level.5. The result seemed to show that the acceleration of flower bud differentiation and the development of suckers could be attained by using large size suckers with temperature of 10°C for more than 3 weeks from the middle of August to early in September, or by nursing the large size suckers at the altitude of 1, 000 meters or higher above sea level for more than 7 weeks from early August to late September.