The summer maize cultivars Zhengdan 958 and Xundan 20 were selected to study the effects of planting densities on the photosynthesis properties of canopy with four density treatments. The results showed that LAI of Zhengdan 958 increased with the increase of planting density. The light transmission of canopy was significantly higher in upper layer than in the lower layer. The chlorophyll content increased with the increase of planting density at first, then decreased when the density exceeded 82 500 plants/ha. Fv/Fm and qP were higher in the third leaf above ear than those in the ear leaf and the third leaf below ear,but NPQ was converse. With the advancing of development stages, the stem diameter increased first and then decreased,reaching the maximum in silking stage. The stem diameter of Xundan 20 decreased with the increase of density. The highest yield was obtained under the density of 90 000 plants/ha for Zhengdan 958 and 82 500 plants/ha for Xundan 20,and the highest yield of two cultivars were 12 166. 070,9 705. 709 kg/ha,respectively.%以夏玉米品种郑单958和浚单20为材料,研究了不同密度条件下夏玉米群体冠层辐射特征和光合特性.结果表明,郑单958玉米叶面积指数随种植密度增加而升高,两品种吐丝期叶面积指数均在82 500株/hm2处理时最高.透光率随密度增加而减小,冠层顶部透光率显著高于冠层底部.吐丝期两品种叶绿素a和叶绿素总含量表现为75 000株/hm2、82 500株/hm2处理高于67 500株/hm2、90 000株/hm2处理.穗位上第3叶Fv/Fm、qP高于稳位叶和穗位下第3叶,NPQ低于稳位叶和稳位下第3叶.随生育进程茎粗在吐丝期达到最大值,浚单20茎粗随密度增加而减小.郑单958在密度为90 000株/hm2时产量最高,为12 166.070 kg/hm2,而浚单20则在82 500株/hm2时产量最高,为9 705.709 kg/hm2.
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