【作者】 陈刚；

【导师】 王忠；

【作者基本信息】 扬州大学 ， 作物栽培与耕作， 2005， 博士

【摘要】 水稻是我国最主要的作物,目前我国生产上大面积种植的水稻品种产量虽高,但大部分米质不优。随着人民生活水平的提高以及稻米贸易对品质的要求,有效地提高水稻产量的同时,改善稻米品质,已成为水稻育种和栽培生产上急需解决的重大课题。胚乳是水稻颖果的主要食用部分,它的发育状况最终决定着稻米的产量和品质,而水稻颖果的发育状况既受遗传基因控制,又受环境因子的影响。在影响稻米产量和品质的诸多环境因子中,氮肥的施用量和施用时期对水稻植株生长和稻米品质的影响尤其明显,因此,它一直是科技工作者的研究热点。水稻胚乳中的淀粉特别直链淀粉含量与稻米的蒸煮食味品质有关,稻米直链淀粉含量偏高,往往使米饭的粘性、柔软性和光泽度变差,影响米饭的质地和适口性。而水稻胚乳中的直链淀粉主要由淀粉粒结合型淀粉合成酶(GBSS,即Wx蛋白)催化合成的,水稻胚乳中Wx蛋白的量和活性对稻米品质有重要影响。因此,研究氮肥和Wx蛋白对水稻颖果的发育和充实的影响,对阐明稻米品质形成的机理,改善稻米品质具有重要指导意义。 针对上述问题,本试验从内因和外因两方面进行研究,一是对扬稻6号和粳稻941两个水稻品种进行施氮时期和施氮量的处理,研究了不同施氮处理对水稻颖果发育、淀粉积累、胚乳细胞结构和稻米品质的影响;二是用Wx蛋白不同程度缺失的转反义Wx基因籼稻和粳稻为材料,研究Wx蛋白缺失对水稻颖果的发育和物质积累的影响。旨在探明控制水稻颖果发育的机理和改善稻米品质的途径。得到的主要结果如下: (1) 适量增施氮肥能增加颖果鲜重和干重,从施氮时期来看,后期增施氮肥对颖果鲜干重的影响比较显著。增加穗肥施氮量能显著提高颖果和颖壳中的叶绿素含量,显著降低颖果中的可溶性糖含量,有降低淀粉含量的趋势,但不明显。增加穗肥施氮量能显著降低颖果中直链淀粉含量,并使颖果中直链/总淀粉的比例降低,提高了稻米的蒸煮食味品质,其效果要好于分蘗期施氮。 (2) 在水稻颖果发育过程中,ADPG焦磷酸化酶(ADPG-PPase)、淀粉粒结更多还原

【Abstract】 Rice is one of the most important crops in China, most of the cultivated rice are high-yield, while the rice qualities are not well. So improving the rice quality is more and more important for the demand of high-quality from people and rice trade. In rice caryopsis, endosperm is the mainly edible part, the development of endosperm is most important for the rice yield and quality. Many factors can influence the development of rice endosperm, such as heredity, climate, environment and cultivation, and one of the factor, the nitrogen fertilizer and its application time, are especially important to the yield and quality of rice. Many achievements have got from the research of nitrogen fertilizer on the rice yield and quality, but the effects of N-fertilizer on the development of rice caryopsis are rarely reported. In addition, the starch, especially the amylose in rice endosperm is correlative to cooking and taste quality. High amylase content in rice endosperm is bad for the rice viscosity, plasticity, polish and taste. The amylose is synthesized under the catalysis of granule-bound starch synthase (GBSS, Wx protein), so the quantity and activity of Wx protein in rice endosperm are important to the rice quality.In this research, the development of caryopsis was studied from intrinsic factor (Wx protein) and extrinsic factor (N-fertilizer). Firstly, the two rice cultivars, Yangdao No.6 and Jingdao 941, were used as materials, to study the effects of various nitrogen treatments on the development of caryopsis, accumulation of starch and endosperm microstructure. Secondly, the transgenic japonica and indica rice with antisense Wx gene were also used, to study the effects of the Wx protein loss on the development of caryopsis and accumulation of stored matter in rice. The main results were as follows:(1) The proper application of nitrogen fertilizer could increase the fresh and dry weight of the caryopsis, especially the N-fertilizer at the heading stage had significantly effects on the fresh and dry weight in caryopsis. Increased application of panicle N-fertilizer could remarkably increase the chlorophyll content in caryopsis and glume, butsignificantly decrease the soluble sugar in the developing rice caryopsis, and the starch content was slightly reduced. The nitrogen fertilizer at the heading stage was negatively correlated with the amylose content in caryopsis, and reduced the ratio of amylose to total starch in developing caryopsis, so the cooking and taste quality was greatly promoted.(2) During the development of rice caryopses, the activities of ADP-glucose pyrophosphorylase (ADPG-PPase), granule-bound starch synthase (GBSS), soluble starch synthase(SSS) and starch branching enzyme (SBE) in endosperm changed as single peak curve. That was, the enzyme activities increased at the initial stage of grain filling, and then depressed after reaching their peak at 10~15d after flowering. Application of nitrogen fertilizer could promote the activities of ADPG-PPase, SSS and SBE in developing grains at middle and late filling stage, and decreased GBSS activity in early and middle filling stage, and the effects of the N-fertilizer at the heading stage were higher than at the tilling stage.(3) The protein percent (%) in caryopsis decreased gradually during the rice grain filling, but the protein content in each grain (mg/grain) increased in the developing caryopsis. Increased the application of panicle N-fertilizer was significantly correlated with the protein content in caryopsis, and had evident effects on the development of protein bodies and amyloplasts. Moreover, panicle N-fertilizer could increase the filling of amyloplasts, decrease the ratio of chalk, so the apparent quality was greatly improved. In addition, the protein and fat content in aleurone layer were higher under N-fertilizer applictation, the aleurone grains became smaller and their number increased.(4) The amylose content in rice caryopsis was remarkably decreased with the loss of Wx protein. In transgenic rice with anitsense Wx gene更多还原