种植密度、氮肥和水分胁迫对玉米产量形成的影响

为阐明种植密度、氮肥和水分胁迫对不同玉米品种产量形成的影响，选用6个玉米品种，在两种密度(45 000株 hm^-2和75 000株 hm^-2)、两种施氮水平(纯氮112.5 kg hm^-2和337.5 kg hm^-2)和两种水分(前期干旱控水和正常灌水)处理下进行大田试验，调查玉米源库性状的主要生理参数和籽粒产量。结果表明，在环境压力较小时(低密度、高氮和正常灌水)，玉米品种间籽粒产量、源性状(叶面积指数、穗位叶净光合速率和群体源供应能力)、库性状(群体库容量)、源库协调性状(群体库源比值、籽粒灌浆速率和收获指数)以及成熟期干物质积累量和吐丝期至成熟期干物质积累量差异较小，而逆境胁迫下(高密度、低氮和干旱)，差异较大。环境压力较大时(高密度、低氮和干旱)，叶面积指数、群体源供应能力、成熟期干物质积累量、吐丝期至成熟期干物质积累量、群体库容量和收获指数与籽粒产量呈显著或极显著正相关。由此说明，在玉米品种产量改良中要强化逆境人工选择，以适应自然选择，改善玉米品种逆境下的群体源库性状，增强吐丝期至成熟期叶片的光合生产效率，强源促库，提高逆境下的生产能力和适应性。

Effects of Plant Density, Nitrogen Application, and Water Stress on Yield Formation of Maize

It is important to promote adaptability of maize varieties to high-density, low nitrogen and drought stresses so as to improve maize yield. Six maize varieties of Yuyu 22, Shaandan 902, Jingdan 28, Shaandan 8806, Xianyu 335 and Zhengdan 958 were planted under two kinds of densities (45 000 and 75 000 plants ha^-1), pure nitrogen levels (112.5 and 337.5 kg ha^-1) and water treatments (controlling water at prophase and normal irrigation) in fields to elucidate effects of stresses (high density, low nitrogen and drought) on yield formation of maize varieties. Main physiological parameters of source-sink characters The results showed that differences of grain yield were little among maize varieties under less environmental pressure (low density, high nitrogen and normal irrigation), while these were significant under stress (high density, low nitrogen and drought). Changes of source characters (LAI, P_n of ear leaves and source capacity), sink characters (sink capacity of population), harmonious source-sink characters (sink-source ratiograin yield. There were significantly positive correlations between grain yield and LAI, source capacity, dry matter accumulation at maturity, dry matter accumulation from silking stage to maturity, sink capacity of population and HI. To improve maize yield, we should strengthen artificial selection for adapting to natural selection, improve source-sink characters of maize population under stress, enhance leaf photosynthetic efficiency from silking stage to maturity, strengthen source and promote sink, and improve production capacity and adaptability under stresses., grain filling rate and HI), dry matter accumulation at maturity and dry matter accumulation from silking stage to maturity showed the same rules as and grain yield were measured.