Abstract
Effect of the starting time of cooling at the flowering stage together with the effects of water temperatures and light conditions after cooling on the fertility percentage were examined. The fertility percentage of the spikelets cooled from the end of the light period was 20% higher than that of the spikelets, with identical maturity, cooled from the end of the dark period. No effect was observed on the fertility if water temperatures (at 25°C and at 15°C) and light conditions (light and dark) were changed after cooling. This suggests that the difference of the fertility percentage between the two cooling starting times, morning and evening, is determined by the difference of some physiological properties of the spikelets at the start for cooling.
