THE RESPONSE OF WHEAT TO HIGH-TEMPERATURE FOLLOWING ANTHESIS .1. THE RATE AND DURATION OF KERNEL FILLING

Wheat (Triticum aestivum L.) plants were grown to anthesis at 18/13 degrees C day/night and either retained at 18/13 degrees C or transferred to a higher temperature (24/19 or 30/25 degrees C) for the grain-filling period. It was confirmed that high temperature resulted in a considerable drop in kernel dry weight at maturity and there was significant cultivar variation in the degree of the response, ranging from a 30 to 60% decrease in kernel dry weight at maturity for a rise in temperature from 18/13 to 30/25 degrees C. An analysis of the rate and duration of kernel filling of seven cultivars showed that those cultivars most tolerant of high temperature during kernel filling (least reduction of kernel dry weight at maturity) were those where the rate of kernel filling was most enhanced by high temperature, i.e. the increased rate compensated for the reduced duration of kernel filling. The importance of the rate of kernel filling in determining varietal responses to high temperature illustrates the need to isolate the effect of temperature on processes in the kernel during the linear phase of growth.