THE RELATIONSHIP BETWEEN FLOWER INDUCTION AND SEED TUBER SIZE IN CHINESE YAM

To make clear factors of flowering in Chinese yam (Dioscorea opposita Thunb.), effects of seed tuber size and seed tuber removal on flowerin g were determined. Growth patterns of plants with or without flowering were analyzed. 1. Plants of D. opposita Thunb. 'Ichoimo' planted in l ate May, 1994, initiated flower bud from late June to early July. 2. M inimum fresh seed tuber weights for flowering were 40 g in 'Ichoimo' a nd 75 g for 'Nagaimo' in 1993; their dry weights were 10.8 and 9.8 g, respectively. Flowering occur red on plants started from seed tubers w hich weighed 10 g or more in dry weight. 3. When seed tubers were exci sed early from the mother plants, the number of flowering plants decre ased significantly. Conversely, when the seed tubers were removed late r, an increased frequency of flowering plants was observed. 4. Althoug h there were no differences in the lengths of the main stem, dry weigh ts of roots and new tuber between plants with and without flowers, tot al length of lateral branches on flowering plants was longer than that of plants without flowers.