叶绿体结构调控水稻光合氮素利用率的机制研究

Photosynthetic nitrogen use efficiency (PNUE), is a key component of nitrogen use efficiency. Further study on the influence factor and regulation pathway to PNUE is also very important for improving the rice yields and nitrogen fertilizer utilization. Leaf nitrogen and water status all have effect on the chloroplast development, photosynthesis and PNUE. However, there is little information on the difference in chloroplast development among rice cultivars with different nitrogen use efficiency, and the mechanism of the effects of chloroplast structure and aquaporins (AQPs) on PNUE is still not full clear. This question will be intensively studied through the following contents , (1)the effects of different nitrogen levels on the nitrogen content, photosynthetic enzyme activity, photosynthetic characteristics and chloroplast size of rice cultivars with different nitrogen use efficiency will be studied to analyze the response difference of PNUE to varied nitrogen conditions. We will discuss the relationships between PNUE and chloroplast structure, and systematically elucidate the unique characteristics of chloroplasts of high nitrogen use efficiency varieties ; (2) the leaf anatomy, aquaporins (AQPs), chloroplast degradation, granum lamellae and starch granules of rice plants with different growth stages will be compared to illustrate the action mechanism of chloroplast structure on PNUE, and the possible way to regulate chloroplast development and improve PNUE by nitrogen and water will also be discussed. The results will be expected to provide theoretical basis for high efficiency utilization of water and fertilizer, improving PNUE and rice yields.

光合氮素利用率（PNUE），是氮素利用率的重要组成部分，深入研究PNUE的影响因素与调控途径对提高水稻产量及氮肥利用具有重要意义。叶片氮素与水分状况均能影响叶绿体发育、光合及PNUE，但是不同氮效率水稻品种间叶绿体发育状况差异，以及叶绿体结构、水通道蛋白等对PNUE的作用机制尚缺乏系统研究，针对这一问题，本项目拟通过以下内容深入展开，（1）研究不同氮素水平对不同氮效率品种水稻氮素含量、光合酶活性、光合特性、叶绿体大小等参数的影响，分析不同氮素效率品种PNUE对不同氮素水平的响应差异及PNUE与叶绿体结构关系，系统阐明氮高效品种叶绿体所具有的特征；（2）比较不同生育时期水稻叶片结构、水通道蛋白、叶绿体降解、基粒片层、淀粉粒等的差异，阐明叶绿体结构对PNUE的作用机制，探讨氮素营养和水分调控叶绿体发育及提高PNUE的可能途径。研究结果预期能够为水肥高效利用，提高PNUE及水稻产量提供理论依据。

水稻是我国重要的粮食作物，保证水稻高产稳产对于保障我国粮食安全至关重要，科学合理的水肥管理也是水稻高产高效的重要措施。本项目以不同氮效率品种水稻为研究对象，比较不同氮素供应及不同水分条件供应下水稻的光合、氮素利用率、产量、叶绿体发育等差异，研究了水氮耦合条件对叶绿体发育的影响机制及如何提高光合氮素利用率。研究结果表明：（1）氮高效品种具有较低的茎叶比及较高的籽粒产量，干湿交替水分条件显著提高了两个品种水稻的有效分蘖及穗粒数，且能够降低氮低效品种的茎叶比、提高结实率，提高水稻产量。（2）两个水稻品种的氮肥偏生产力均随供氮水平增加而显著降低，干湿交替条件显著提高了水稻的氮肥偏生产力、氮肥农学效率及氮肥回收利用率；辽星品种氮肥利用率高于秋田品种，且在干湿交替条件下，辽星品种氮肥利用率提高幅度大于秋田品种。（3）两个品种水稻光合速率随供氮水平增加显著增加，在较低氮水平下，干湿交替处理光合速率显著高于常规淹水处理，在较高氮水平下，两个水分处理间光合速率无显著差异；两个水稻品种在干湿交替条件下光合氮素利用率显著高于常规淹水条件，两种水分条件下辽星品种光合氮素利用率显著高于秋田品种。（4）干湿交替条件下具有较高的荧光参数及更高的叶肉导度，且辽星品种叶肉导度显著高于秋田品种。虽然高氮条件下具有较多的叶绿体及较厚的类囊体堆叠，但是单位面积下单个叶绿体的光合能力降低，叶片光合氮素利用率降低。干湿交替条件下淀粉粒含量较少，光合产物输出能力强，有利于光合氮素利用率的提高。要保持较高的光合和光合氮素利用率，氮高效品种叶片氮素含量应低于1.20 g·m-2，氮低效品种叶片氮素含量应低于1.46g·m-2，因此，合理的氮素和水分供应能够调控光合氮素利用率，为提高水稻光合能力及产量提供理论依据。