Abstract
Field experiments were carried out at 8 sites: Chiang Mai and Ubon in Thailand, Taoyuan of Yunnan and Nanjing in China and Kitakami, Ina, Kyoto and Matsue in Japan, to clarify the relationship between the translocation rate of dry matter from vegetative organs to panicle and air temperature in 2001 and 2002. The potentially degradable dry matter in leaves and stems under the field condition was determined by an enzymatic degradation method using protease and α-amylase. The dry matter was determined at the full heading stage and 2 weeks later in 9 varieties: Takanari, IR72, Shanguichao, CH86, IR65564-44-2-2, Nipponbare, Takenari, Banten and WAB450-1-B-P-38-HB. The maximum daily air temperature during the 2 weeks after full heading correlated with the translocation rate of dry matter from vegetative organs to panicles more closely than the mean and minimum daily air temperature. The highest translocation rate was recorded when the average of maximum daily air temperature was around 30°C. There was a significantly positive correlation between the translocation rate and the average of daily air temperature difference (maximum-minimum temperature). The relationship between the translocation rate and air temperature was expressed by a simplified non-linear model that has 2 exponential equations with 4 parameters.
