During the period from 2012 to 2014, Zhengdan 958 (ZD958) and Denghai 605 (DH605) were used with five treatments in a randomized complete block design with three replicates, including increasing light (L) from tassel stage (VT) to maturity stage (R6) and three shading treatments (40% of ambient light intensity) from VT to R6 (S1), from the sixth leaf stage (V6) to VT (S2), and from emergence stage (VE) to R6 (S3), and natural lighting in the field (CK). The illumination intensity of L on cloudy day was 1600?1800 μmol m-2 s-1. This experiment was conducted to explore the effects of light on endosperm cell proliferation, grain filling, starch content, dry matter accumulation and yield of summer maize. The dry matter accumulation of embryo and endosperm was significantly decreased under shading, as well as the content of starch and the endosperm cell plumpness decreased also. Effect of S3 on endosperm cell proliferation was the most, while that of S2 was the smallest. At R6, the endosperm cells number of S3, S2, S1 decreased by 33%, 6%, 29% in ZD958 and 41%, 5%, 29% in DH605. The dry matter accumulation of embryo and endosperm as well as the content of starch and the endosperm cell plumpness were increased after increasing light. The grain filling rate decreased and the days to maximum grain filling rate postponed under shading, while those increased after increasing light. The maximum grain filling rate of S1, S2, S3 decreased by 34%, 13%, 58% in ZD958 and 38%, 13%, 64% in DH605. The grain yield of S1, S2, S3 decreased by 58%, 26%, 81% in ZD958 and 67%, 27%, 81% in DH605. Results indicate that the number of endosperm cells, starch content and grain filling rate are decreased under shading, resulting in grain yield reducing, while L treatment can contribute to increasing the number of endosperm cell and grain yield.
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