Effect of High Temperature and Drought Stress on Carbohydrate Translocation in Japanese Apricot ‘Nanko’ Trees

抄録

With the continuing trend of global warming, the adverse impact of high temperature and the inevitably accompanying drought stress on the growth of Japanese apricot trees (Prunus mume Siebold et Zucc.) are of concern. Therefore, the effects of these factors on photosynthesis and carbohydrate translocation were analyzed. An investigation was conducted at average daytime temperatures of 24°C, 30°C, and 34°C under both irrigated and drought conditions. The 34°C temperature was higher than the open air temperature by 5°C. Stable isotope ¹³C was administered to trees to determine carbohydrate positioning. Under the drought stress condition, the photosynthetic rate declined accompanied by temperature elevation, and at the highest temperature of 34°C, ¹³C concentrations in the twigs and roots were lower than those in the irrigated trees at 24°C. Two-way analysis of variance revealed a trend of ¹³C translocation to the young organs above ground, and old organs, while roots were affected by water status, temperature, and their combination, respectively. In the irrigated trees, the photosynthetic rate reduction was not detected, even at higher temperatures. However, translocation incompetence reflecting a decline in ¹³C concentration in the roots was observed at 34°C. These results indicate that the permissible diurnal average temperature during summer for the growth of Japanese apricot trees is approximately up to 30°C, and in the temperature range around this irrigation is helpful to facilitate regular functioning of carbohydrate translocation under drought stress conditions.