Most of the observations show that canopy temperati re is lower than air temperature of 1.5m.above the canopy in the wheat fields with an adequate water supply during day and night.Smoetimes, leaf temperature is slightly higher than air temperature from 8:00-10:00 in the morning. The maximum difference between leaf temperature and air temperature occurs in the period from after sunset to before dewing. It occurs about one hour after sunset under calm,clear day. In daytime, the canopy temperature of summer m...