Effects of Temperature on Aerial and Seed Tuber Sprouting and Plumule and Radicle Elongation of Japanese Yam (Dioscorea japonica Thunb.) ‘Inabu-2 gou’

Abstract

We investigated the effects of temperature on aerial and seed tuber sprouting and plumule and radicle elongation of Japanese yam (Dioscorea japonica Thunb.) ‘Inabu-2 gou’. Sprouting of aerial tubers cultured at 30°C was the earliest within 3 days after the start of culture. At this temperature, the sprouting rate of aerial tubers on the 7th day after culturing was also the highest, at 76%, and the final sprouting rate reached over 80%. Although the initial sprouting rates of seed tubers cultured at 20°C and 35°C were the same, the sprouting rates on the 7th and final days in the cultures were higher at 25°C and 30°C. It was considered that the optimal temperature range for the sprouting of aerial and seed tubers in this study was about 30°C and 25–30°C, respectively. The lengths of plumules and radicles of aerial tubers were the longest at 30°C. The heavier the aerial tuber, the longer the plumule and radicle. The lengths of the plumule of seed tubers were also the longest at 30°C; however, the length of radicles was the longest at 25°C and 30°C. No clear effects of the initial size of aerial tubers on the number of sprouted buds were observed. According to the results of the above experiments, we concluded that the optimal temperature for early growth of aerial and seed tubers was about 30°C and 25–30°C, respectively.