Abstract: The compound effects of nitrogen level and high temperature at late booting stage on rice yield were investigated at two nitrogen levels, with hybrid rice combination (Ganxin 203) and  conventional rice cultivar (Zhong 531) as materials at 38 °C for 4 days at late booting stage. We analyzed the difference in grain yield and physiological indicators of the  two rice cultivars and nitrogen effects under high temperature. The results showed that yield per plant, effective panicle number per plant, spikelet number per panicle, spikelets fertility, differentiated spikelet number per panicle, and harvest index of  the two rice cultivars decreased to various degrees under high temperature at the same nitrogen level at late booting stage. Furthermore, high temperature significantly decreased yield per plant, spikelet  fertility, and harvest index   compared with natural temperature (P< 0.05). The ratio of degenerated spikelets, leaf weight per stem, stem and sheath weight per stem increased under high temperature, while under high temperature  the ratio of degenerated spikelets significantly increased  compared with natural temperature (P< 0.05).  At  the same nitrogen level, the chlorophyll contents of the two cultivars increased to various degrees at the late stage under high temperature. For Zhong 531, the chlorophyll contents increased by a  lower increasing percentage at  high nitrogen level compared with that at normal nitrogen level  under  high  temperature. In addition,  yield per plant and effective panicle number per plant of the two cultivars at  high nitrogen level were higher than those at  normal nitrogen level. Under  high temperature, spikelet number  per panicle, 1000grain weight, and harvest index of Zhong 531 at  high nitrogen level were significantly higher than those at normal nitrogen level, while spikelet fertility was significantly reduced. It was worth noting that  yield per plant of the two cultivars at  high nitrogen  level decreased by a lower percentage  compared with normal nitrogen level under high temperature, implying that   appropriate  high nitrogen levels contributed to relief of  the effects of high temperature on grain production.

Key words: rice, late booting stage, high temperature, grain yield, chlorophyll contents, nitrogen level

摘要： 为探究氮肥和孕穗后期高温对水稻产量的复合影响，以杂交稻淦鑫203和常规品系中531为材料，设置2个氮肥水平，于水稻孕穗后期38℃高温处理4 d，分析高温处理下2个水稻品种产量、生理指标的差异及氮肥效应。结果表明，同一氮肥水平下，与自然温度相比，孕穗后期高温处理下2个供试品种的单株产量、单株有效穗数、每穗总粒数、结实率、每穗颖花分化数和收获指数均表现出不同程度的降低，其中，单株产量、结实率和收获指数差异达显著水平；而颖花退化率、单茎叶质量和单茎茎鞘质量则不同程度增加，其中颖花退化率差异达显著水平。同一氮肥水平下，与自然温度相比，高温处理后期2个品种的叶绿素含量均有不同程度上升，中531高氮处理的叶绿素含量增幅低于正常氮肥处理。自然温度和高温处理下，与正常氮肥水平相比，高氮处理增加2个品种的单株产量和单株有效穗数。另外，在高温条件下，与正常氮肥水平相比，高氮处理显著增加中531每穗总粒数、千粒重和收获指数，显著降低结实率。值得注意的是，高温条件下，2个品种高氮处理的单株产量降幅低于常氮处理，说明适当高氮可减轻高温的减产作用。

关键词: 水稻, 孕穗后期, 高温, 产量, 叶绿素含量, 氮肥