Effects of high air temperature on ripening in rice plant - Analysis ofripening performance under climate conditions by changing in croppingseasons and/or transferring pots from lowland to upland [Japanese]

摘要

The effects of high temperature in August in Fukuyama city, Japan, on the grain weight and the grain quality of rice plants were examined. Air temperature was manipulated by 1) changes in cropping seasons by different planting dates and 2) transferring pots from lowland to upland at the heading stage. In the first experiment, no significant differences were found among the mean grain weights and the grain quality of any cropping seasons. In the second experiment, no significant difference was found in the mean grain weight between the two treatments, but significant differences in the grain quality and the weights of grain with a thickness of more than 1.9mm were observed. In experiments 1) and 2), the grain weight/mean solar radiation during 20 days from the 4 days after flowering stage at the top of the panicles (=S20) correlated negatively with the mean temperature at that stage. The rate of normal grains/S20 did also. These results suggest that the negative influence of high temperature, 27 similar to 28 degreesC, on grain weight is counteracted when solar radiation increases, accompanied by temperature increase. When temperature increases without increases in solar radiation, however, the grain weight and grain quality were adversely affected.