Studies on the plant growth substances causing the growth and enlargement of tubers in yams (Dioscorea alata L.)

点击翻译按钮获取中文摘要

A new bioassay method, using in vitro microtubers of yams, detecting the activity of the endogenous growth substances considered to induce the growth and enlargement of tubers was developed in this studies. The new method "microtuber test" developed is considered to be reliable enough to enable to detect the action of the endogenous growth substances.Using a microtuber test, tuber enlargement activity was found in acidic fraction of extract obtained from leaves in yams. The activity increased under short day length, whereas not incrrease under long day length. In seasonal change, tuber enlargement activity remained almost constant during summer, but after, the middle of September, activity increased gradually and then reached a maximum in early October.Jasmonic acid was isolated with the guidance of microtuber test and identified by gas chromatography.These results seem evidences for the occurrence of the tuber enlargement activity which is formed in leaves under the short day and transmitted to under ground part to induce growth and enlargement of tuber in yams.Yam plants were sprayd with gibberellin (GA) of five concentration levels for two to four months after planting. The application of GA did not promote the elongation of main stem, but instead sligtly inhibited. Highly concentrated GA strongly inhibited the development and elomagation of branches. In contrast, the GA application stimulated the growth and enlargement of tuber even under the long day. It was also observed that foliar spray with GA at the later growth stage significantly extended the period of a dormant state in tubers.These results indicates that yam plants might have a characteristic response to GA and that the application of GA elongates the dormant period of tubers in yams (D.alata).