水稻不同节位茎叶花后C、N再运转的功能分组及机制

It will have great significance for the regulation of grain filling in the middle and lower part of the large panicle rice varieties to clarify the contribution of the C and N retransferring after flower to the grain growth of different parts of rice. The accumulation of C and N in the grains was about 1/3 and 2/3, respectively, from the C and N re-translocation of stem and leaf after flower. However, the grain filling and the C and N re-translocation of the stem and leaf after flower (especially high yield and large panicle rice varieties) showed obvious sequence. So the function of C and N re-translocation of stem and leaf in different node must be grouped. Therefore, the field experiments and 15N and 13C isotope tracer test were conducted in this project, to study the dynamic process of the C and N accumulation of different branch grain and re-translocation of the C and N in stems and leaves after flowering. Meanwhile, to test the key enzymes activity and the genes expression involved in the metabolism of C and N of the grain, stem and leaf. This study will build the relationships between accumulation and re-translocation of carbon and nitrogen of the grain, the stem and the leaf base on position/node after flowering, propose the functional grouping methods of re-translocation of the carbon and nitrogen of the stem and the leaf after flower, clear their mechanisms and provide important theoretical basis for high yield cultivation.

明确水稻不同节位茎叶花后C、N的再运转对不同部位籽粒生长的贡献，对于调控大穗型水稻中部和下部籽粒灌浆有特别重要的意义。水稻籽粒中积累的C、N，分别大约有1/3和2/3来源于花后茎叶C、N的再运转。然而，水稻（特别是高产大穗型水稻品种）籽粒灌浆及花后茎叶C、N再运转均表现出明显的序列性。因此，不同节位茎叶花后C、N再运转的功能一定存在分组现象。为此，本课题拟通过大田试验和田间15N和13C同位素示踪试验，测定不同枝梗籽粒C、N积累和不同节位茎叶花后C、N再运转的动态过程，并同步测定籽粒和茎叶中主要C-N代谢相关酶活性及基因表达量的变化。项目完成后，可建立基于部位/节位的水稻籽粒C、N积累与茎叶花后C、N再运转关系，提出不同节位茎叶花后C、N再运转功能分组的方法，并解析其机制，为水稻优质高产栽培调控提供重要的理论依据。

以农乐1号和桂丰2号为材料进行田间试验和13C、15N示踪盆栽试验，研究水稻籽粒C、N积累与茎叶C、N再运转间的关系及机制。主要研究结果如下：.（1）根据单个一次枝梗籽粒灌浆参数，将一次枝梗分成三个枝梗群，即强一次枝梗群、中一次枝梗群和弱一次枝梗群，其养分、物质积累数量与速度依次下降，积累高峰期依次推迟。.（2）干物质和C再运转数量为节间＞叶鞘＞叶片，节间占50%以上。N再运转数量为叶片＞节间＞叶鞘，叶片占70%以上。器官中，倒3节间对干物质和C再运转作用最大，倒1叶、倒2叶对N再运转作用最大。.（3）水稻茎叶C再运转对籽粒C积累的表观贡献率为10%-30%，节间约占6%-20%。茎叶N再运转对籽粒N积累的表观贡献率为40%-60%，叶片约占26%-40%。.（4）C再运转对籽粒C积累的直接贡献率为2.9%-74.8%，下部籽粒＞中部籽粒＞上部籽粒，枝梗差异显著。茎叶N再运转对籽粒N积累的直接贡献率为57.2%-80.4%，枝梗差异小。.（5）顶部茎叶再运转功能分为三组。第一组为N再运转功能组，以N再运转为主。第三组为C再运转功能组，以C再运转为主。第二组为中间组，兼顾C、N再运转。.（6）上部籽粒C、N积累量大与其活跃灌浆期较高的ADPG焦磷酸化酶、谷氨酰胺合成酶活性及OsAGPL2基因、OsGS1;1基因的高表达量密切相关。. 本项目建立了水稻枝梗群分组及茎叶再运转功能的分组方法，从酶学和基因表达水平阐明了其生理机制。项目研究为挖掘水稻下部籽粒产量潜力的定向栽培调提供了重要理论依据。

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