中文摘要：

【目的]从细胞学角度探讨玉米花后不同时期遮光对玉米籽粒重量及品质的影响。【方法】以普通玉米泰玉2号为材料，大田条件下分别于授粉后1—14d（S1）、】L5--28d（S2）及29—42d（S3）遮光55％，以大田自然光照条件下生长的玉米作为对照（SO），对不同遮光处理下玉米粒重、品质、胚乳细胞增殖变化及穗轴可溶性糖含量进行了分析测定，对小穗柄维管束截面积、胚乳细胞及胚乳传递细胞的超微结构进行了观察。【结果】各时期遮光使籽粒重量、淀粉含量、胚乳细胞数量和体积降低，籽粒胚／胚乳比、蛋白质含量、粗脂肪含量升高。遮光延迟了淀粉粒的发育，降低了胚乳细胞的充实度；前期遮光籽粒胚乳细胞数目最少，中期遮光淀粉粒体积最小，胚乳细胞的充实状态最差。遮光后穗轴中可溶性糖含量升高，小穗柄维管束截面积无明显变化；遮光使胚乳细胞中蛋白质体增多，胚乳传递细胞变小，传递细胞壁内突变稀、变短，不同层次问连接程度下降，养分传输能力降低，胚乳传递细胞中线粒体数量减少。【结论】花后不同时期遮光改变了玉米籽粒品质，系籽粒中胚比重增加及胚乳细胞内含物比例变化所致。遮光后胚乳传递细胞形态与功能的变化及较低的线粒体数量限制了养分的传输，“流”不畅是生育后期遮光玉米粒重降低的重要原因之一。

英文摘要：

[Objective] The objective of the current study was to investigate the effects of different-stage shading after anthesis on grain weight and quality of maize at cytology level. [ Method] The shading experiment was conducted in the field from 2005 to 2006, with a common maize cultivar （TY2） as the experimental material. Plants were stressed using horizontal shading net and the light intensity reduced by 55%. Field-grown maize plants were shaded at 1-14 d （S1）, 15-28 d （S2） and 29-42 d （S3） after pollination respectively. Control plants （SO） were grown under natural light. Grain weight, quality, endosperm cell proliferation, cob sugar content and grain pedicel vascular bundle cross section area were measured. The ultrastructural changes of endosperm cells and endosperm transfer cells were observed after pollination. [Result] The result indicated that the grain weight, starch content, endosperm cell number and volume were declined after shading. On the contrary, embryo/endosperm ratio, protein content and fat content in grain increased. Shading treatments significantly delayed the development of the starch granules, also remarkably reduced the endosperm filling status. Among the three treatments, the number of the grain endosperm was the least under shading stress at 1-14 d after pollination. However, the volume of starch granules and the substantiation of endosperm under shading treatment at 15-28 d after pollination were the worst. Compared with the control （natural sunlight without shading）, the soluble sugar of maize cob increased significantly, while there was no obvious change in vascular structure of small cluster stalk. The number of protein body in maize endosperm was influenced markedly by low light at different stages after pollination. Low light decreased the volumeof the grain endosperm transfer, and the cell wall extensions of the basal transfer cells became thinner and shorter under shading treatment than those of the control, furthermore, the degree of connect extent and the ca