球根アイリスの球根の状態と花芽分化 に及ぼす低温効果との関係

Abstract

An effect of low temperature on the flower bud formation in iris ‘Wedgwood’ is affected by the physiological condition of bulbs. In the present study, some factors influencing the response of bulbs to low temperature were examined.In order to examine the effect of low temperature on the flower bud formation, the bulbs were treated with low temperature of 10°C for 20, 35 and 50 days from August 12, 27, September 11, 26 and October 11 respectively. Earlier flower bud initiation was observed in the bulbs which treated in earlier time when the duration of treatment was the same, though the speed of the development of flower bud was accelerated with the treatment in later time. When the treatment started on August 12, flower bud development was most advanced in the bulbs which treated for 50 days, while it was most advanced in the bulbs which treated for 35 days when the treatment started on September 11. The number of leaves formed before the flower bud formation was reduced with increasing duration of the low temperature treatment. When the same duration of the low temperature was given, a similar number of leaves was formed before the flower bud formation independently of the time of treatment; however, the number of leaves formed after low temperature treatment, before the flower bud formation, decreased as the time of treatment advanced. The growth of the first leaves was accelerated but ceased early when the low temperature was started on late time or the duration of the treatment was long.In the bulbs which produced in warm, cool and cold regions in Japan and treated with low temperature at 10°C for 35 days, flower bud formation was advanced in those produced in warm region and was delayed in cold region. The rest period of those bulbs that not received the low temperature was differed by the difference of the regions where bulbs were produced, and the rest terminated early in the bulbs produced in warm region and late in those produced in cold region.It was found that the bulbs whose scales were removed prior to low temperature treatment at 13°C for 45 days did not form flower buds, while those whose scales were removed after the treatment formed flower buds.From the results above mentioned, it might be said that iris bulbs have become to form flower bud early with shorter treatment of low temperature as the age of bulbs advanced after the rest had terminated. On the flower bud formation, the difference in the response of bulbs, which produced in different regions in Japan, might be partly due to the difference in the rest periods of those bulbs. Scales might also have some influence on the flower bud initiation relating to the low temperature effect.