サツマイモ塊根の肥大に対する根温の影響

―直接的および間接的な温度の影響―

抄録

Root temperature effects on tuberous root growth of sweetpotato were examined using a hydroponic system where the temperature conditions of shoot, tuberous root and fibrous roots were controlled independently. Plants were grown under various root temperature conditions of 24/24, 24/28, 28/28, 32/28 and 32/32°C (tuberous root temp./fibrous root temp.), and volume changes in the tuberous root were measured on-line. Growth of fibrous roots was also examined for 16, 20, 24, 28 or 32°C of fibrous root temperature in another experiment. In all the experiments, shoot environment was controlled at 28°C, 70% RH, PPFD 300 μmol m^-2s^-1and a photoperiod of 12 h. In the fibrous roots, rates of elongation and dry matter accumula-tion were enhanced by an increase in the temperature. In the tuberous root, rates of growth and dry matter accumulation were higher in the temperature combinations of 24/24°C and 28/28°C, and extremely lower in 24/28°C and 32/32°C. The inhibition of the tuberous root growth in those temperature conditions was found to be caused by changes in ratio of carbon partitioning between the tuberous root and the fibrous roots in relation to sink strength of fibrous root. Based on our findings, the tuberous root growth of sweetpotato is sensitive to growth activity of fibrous root.