Male sterility caused by cooling treatment at the young microspore stage in rice plants. XXVIII. Prevention of cool injury with the newly devised water management practices. Effects of the temperature and depth of water before the critical stage.

Abstract

Potted rice plants were grown in the phytotron with different water temperature and water depth during the period from the spikelet differentiation stage to just before the young microspore stage, and then cooled at 12°C for 3 days at the young microspore stage to test their cool tolerance. The degree of cool tolerance at the young microspore stage was greatly varied with the temperature and depth of water before the critical stage. It was enhanced with raising the water temperature up to 25°C and with increased water depth up to 10 cm. Effect of the deep water irrigation as countermeasures against cool injury were experimented under the severe cool-temperature conditions in the phytotron. Yield-decrease due to cool air temperature during the critical stage was remarkably reduced by keeping the water depth at 10 cm before the critical stage, and it's effect was larger than that of the former deep water irrigation of 20 cm during the critical stage. Preventive effect of cool injury by combining the deep water irrigation before and during the critical stage was not additive but synergistic. Based on these results, we proposed the water management with a depth of 10 cm during the period from the spikelet differentiation stage to the young microspore stage as a newly devised countermeasure against cool injury.