Abstract: Pot experiments were conducted to study the effects of different nitrogen application time(at the tillering and booting stages under the same nitrogen amounts)on caryopsis development and grain quality of rice variety Yangdao 6.The increased nitrogen fertilizer(urea),especially at the booting stage,could evidently increase head rice rate,milled rice rate and protein content in grains compared with the control,while decrease chalky grain rate and amylose content.The increased nitrogen fertilizer applied at the tillering and booting stages could significantly affect caryopsis development and enhance grain weight,with more obvious when applied at the booting stage.In the course of caryopsis development the increased topdressing of nitrogen fertilizer at the tillering and booting stages could obviously decrease the total starch and amylose contents,but not obviously for amylopectin content.Increased topdressing of nitrogen fertilizer,especially at the booting stage,had significant effect on the development and structures of amyloplasts and protein bodies.That is,it could change the distribution,numbers and shapes of amyloplasts and protein bodies in the endosperm cells especially in grain abdomen.Compared with the control the arrangements of amyloplasts and protein bodies were closer,with more numbers and higher density and less interspaces each other.Furthermore,most amyloplasts showed polyhedron under the increased nitrogen fertilizer.

Key words: caryopsis development, rice quality, amylose, protein body, amyloplasts, nitrogen fertilizer, fertilizer application time

摘要： 通过盆栽试验研究了相同施氮量下不同施氮时期（分蘖期和孕穗期）对扬稻6号颖果发育及稻米品质的影响。与对照相比，增施氮肥（尿素）特别是孕穗肥能显著提高稻米精米率、整精米率、蛋白质含量，降低垩白粒率和直链淀粉含量；在分蘖期和孕穗期施氮肥能明显影响颖果发育，提高粒重，而后者的效果更为明显；在颖果发育过程中不同时期增施氮肥能显著降低颖果的总淀粉和直链淀粉含量，但对支链淀粉含量影响较小；不同时期增施氮肥特别是孕穗肥对淀粉体和蛋白质体的发育及结构均有显著影响，能显著改变籽粒中不同部位特别是腹部淀粉体和蛋白质的分布、数目和形状。与对照相比，淀粉体和蛋白质体的排列更紧密、相互间空隙较少、数量增加、密度增大，淀粉体形状多数呈晶状体。

关键词: 颖果发育, 稻米品质, 直链淀粉, 蛋白质体, 淀粉体, 氮肥, 施肥时期