提高水稻等作物的光合作用效率是大幅度提高水稻等粮食作物单产的重要技术途径。前人在温光水气肥等环境因子对光合作用的影响与机理等已有广泛研究，但研究大多基于环境因素达到稳态后的影响效应。由于太阳的方位变化、风云、雾霾等变化，以及作物群体上部叶片与相邻植株的遮挡，光强波动不可避免。水稻光合作用对光强波动的响应及其机理、与光能利用效率的关系等的研究目前鲜见报道。为此，本项目拟选用不同光效品种，通过盆栽和大田设置不同的光强波动处理，采用Li-Cor 6400XT和同位素质谱仪测定结合，系统研究：①不同光合效率基因型水稻的Rubisco酶、叶绿素荧光动力学、叶片气体交换特性等对光强波动的响应；②叶片的形态和解剖结构特征与光合作用光强波动响应的关系；③氮素运筹对光强波动响应的影响。旨在阐明不同光合效率基因型水稻光合作用对光照波动的响应与机理，为水稻高光效品种筛选和高光效栽培提供理论依据和技术指导。

Improving crop photosynthetic efficiency including rice is a critical strategy to improve the grain yield per unit area. Numerous previous literatures related researches are focused on the effects of the photosynthetic active radiation (PAR), temperature, irrigation, nutrient supply and atmospheric environmental CO2 concentration on the crop photosynthesis. However, most of these findings are concerned mainly on the photosynthesis effects affected by these environmental when they reach a steady state. Actually, affected by the azimuth variation, cloudy cover, smog, shading by the upper leaves and adjacent plant block, light intensity intercepted by rice leaf blade always suffers from PAR fluctuations. The responses of photosynthesis to the PAR fluctuations, its adjusted ability and the related mechanisms are unclear and few reports present at present. .Therefore, this proposal attends to elucidate the effects of PAR fluctuation on photosynthesis and its mechanisms. A group of rice varieties with different radiation use efficiency (RUE) is selected based on our previous findings. Increasing the light intensity using higher power Leds, decreasing the light intensity through shading are planned to serve as the PAR fluctuation treatments. The variation and responses of stomatal movement, activities of the key photosynthetic enzymes, and chlorophyll fluorescence kinetic characteristics to the PAR fluctuation are focused to study using the advanced technology measuring with Li-Cor 6400XT combined with isotope mass spectrometer. It is expected to reveal the genetic variation of photosynthesis responses to the PAR fluctuation, and its associated mechanisms. The findings are expected to provide theoretical support and technical guidance for screening higher photosynthetic efficiency rice varieties and development higher RUE cultivation.