中文摘要：

【目的】探讨稻茬小麦高氮肥利用率条件下群体花后衰老特征。【方法】2010—2012年，在稻麦两熟制条件下，以扬麦20为材料，采用三因素裂区设计，以施氮量（纯N）为主区，设210.0 kg·hm-2、262.5 kg·hm-2两个水平；以施氮比例为副区，设基肥﹕壮蘖肥﹕拔节肥﹕穗肥分别为3﹕1﹕3﹕3、5﹕1﹕2﹕2两个水平；以穗肥追氮时期为裂区，设剑叶露尖、孕穗期、抽穗期和开花期四个水平。通过试验构建不同氮肥利用率（NUR）群体，研究其产量、物质生产、氮素吸收及花后剑叶衰老特性的变化特征。【结果】不同群体NUR变幅在31.18%—72.23%， NUR≥60%群体（氮高效群体）籽粒产量8500 kg·hm-2以上，比NUR40%—60%群体（氮中效群体）和NUR≤40%群体（氮低效群体）籽粒产量分别高6.84%和21.36%，群体间差异均达显著水平。NUR 与籽粒产量呈极显著线性正相关。不同群体间花前干物质积累量和氮素积累量差异未达显著水平。但随NUR增高，花后及总的干物质积累量、开花期植株氮素含量和成熟期群体氮素积累量增加，NUR≥60%群体花后和总的干物质积累量分别达6000和17500 kg·hm-2以上，开花期植株氮素含量和成熟期群体氮素积累量分别达1.50%和215 kg·hm-2以上。此外，随NUR的提高，花后群体光合面积衰减逐渐减缓，净同化率逐渐增加；植株花后剑叶光合能力和抗衰老能力逐步增强，在籽粒灌浆后期表现更为明显，促进了花后光合物质生产。NUR≥60%群体花后叶面积衰减率、光合势和净同化率分别在0.14 LAI·d-1、105＆#215;104m2·d·hm-2和9.50 g·m-2·d-1左右。综合两年结果，在氮肥适当后移（3﹕1﹕3﹕3）条件下，穗肥适当早施（剑叶露尖、孕穗期），产量及氮肥利用率较高；高施氮量（262.5 kg·hm-2）的增产效果不明显，且氮肥利用效率较低。在施氮量210.0 kg·hm-2、氮肥运筹3﹕1﹕3

英文摘要：

[Objective]This study investigated the post-anthesis characteristics of wheat population in rice-wheat rotation system under high nitrogen utilization efficiency condition.[Method] From 2010 to 2012, using wheat variety Yangmai 20 as material, the field experiments were conducted as split-plot design which included 16 combinations of two applications of nitrogen amount （210.0 kg·hm-2 and 262.5 kg·hm-2）, two nitrogen applied ratios of basis﹕tillering﹕elongation﹕booting （3﹕1﹕3﹕3 and 5﹕1﹕2﹕2）, and four nitrogen topdressing stages （flag leaf stage, booting stage, heading stage and anthesis）. In the rice-wheat rotation system, wheat populations at different nitrogen utilization rate （NUR） levels were established by agronomic management. The differences of grain yield, matter production, nitrogen absorption, and flag leaves senescence characteristics after anthesis among different NUR level populations were analyzed, respectively.[Result]The range of NUR in different populations was 31.18%-72.23%. Grain yield of NUR≥60% population （NUR-H） was more than 8 500 kg·hm-2, which was 6.84% higher than NUR 40%-60% population （NUR-M） and was 21.6% higher than NUR≤40% population （NUR-L）. There were significant differences among the three populations. NUR was significantly positively correlated with grain yield. And different NUR populations were not distinct in dry matter accumulation amount and nitrogen accumulation amount before the stage of anthesis. With NUR improvement, dry matter accumulation amount after anthesis and at maturity, plant nitrogen content at anthesis, and population nitrogen accumulation amount at maturity increased, which were more than 6 000 kg·hm-2, 17 500 kg·hm-2, 1.50% and 215 kg·hm-2 in NUR≥60% population, respectively. Moreover, along with NUR increasement, decay of population photosynthetic area after anthesis gradually postponed, and net assimilation further increased, as well as flag leaves photosynthetic capacity and anti-oxidant ability af