Effects of High Nitrogen Supply on the Susceptibility to Coolness at the Young Microspore Stage in Rice(Oryza sativa L.)

摘要

The combined effects of high nitrogen supply, cool temperature regimes and shading on factors related to fertility in rice plants were investigated. High nitrogen supply during the period from the spikelet differentiation stage to the young microspore stage caused a decrease in the number of microspores per anther. High nitrogen supply plus cool treatment at the young microspore stage(12°C for 3 or 4 days)resulted in a conspicuous decrease in the number of engorged pollen grains per anther. Shading also decreased the number of microspores and pollen grains. The lowest numbers of microspores and pollen grains were observed in a treatment combining high nitrogen supply with shading and cooling. The number of pollen grains shed on the stigma and germinated pollen grains were decreased by cooling. These results suggested that the lower fertility due to high nitrogen supply combined with cooling resulted from 1)decrease in number of microspores, 2)large decrease in number of pollen grains per anther, and 3)decreases in number of pollen grains and germinated pollen grains on the stigma.