At favorable air-and/or soil-temperature for the assimilates to translocate into the tuber, the growth of whole plant was increascd caused probably by the higher photosynthetic rate of leaves. In the regime of this experiment, 17/12-24/24°C (air-soil, day/night temperature) and 24/19-24/19°C were most favorable for both tuber and plant growth. Taking air-and soil-temperature into consideration, the optimum mean temperature for tuber production seemed to be around 20°C. When air temperature is higher or lower than the optimum, dropping or raising of soil temperature by some methods may be very effective in promoting plant and tuber growth.