The Relationship between Flower Induction and Seed Tuber Size in Chinese Yam

To make clear factors of flowering in Chinese yam (Dioscarea opposita Thunb.), effects of seed tuber size and seed tuber removal on flowering were determined. Growth patterns of plants with or without flowering were analyzed.1. Plants of D. opposita Thunb. 'Ichoimo' planted in late May, 1994, initiated flower bud from late June to early July.2. Minimum fresh seed tuber weights for flowering were 40 g in 'Ichoimo' and 75 g for 'Nagaimo' in 1993; their dry weights were 10.8 and 9.8 g, respectively. Flowering occurred on plants started from seed tubers which weighed 10 g or more in dry weight.3. When seed tubers were excised early from the mother plants, the number of flowering plants decreased significantly. Conversely, when the seed tubers were removed later, an increased frequency of flowering plants was observed.4. Although there were no differences in the lengths of the main stem, dry weights of roots and new tuber between plants with and without flowers, total length of lateral branches on flowering plants was longer than that of plants without flowers.