水稻光合作用对光强波动的响应及其机理研究

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.

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。

摘要：在自然条件下，作物生长的光照条件是非常复杂的，主要原因是由于太阳方位的改变、云层遮挡、受风力影响的相邻叶片间的遮挡等，为了达到最大程度的利用光能，同时不损害自身的结构，植物需要有快速应对光强变化（波动）的能力，探明水稻光合作用及其相关过程对光强波动的响应和机理、氮素运筹对这些过程的影响，将有助于进一步明确水稻高光效机理，为高光效品种筛选和优化氮肥运筹提高大田光合效率提供理论指导。因此，本项目主要围绕不同环境下水稻叶片光合作用对波动光的响应及机理进行了研究，主要的研究结果如下：（1）不同水稻品种光合作用和气孔导度对波动光的响应存在显著的基因型差异，不同水稻品种光合作用对波动光额响应主要受气孔响应的限制，而受生化反应过程的影响较小；光合作用和气孔导度对波动光的响应主要受叶片气孔形态的影响，气孔越小、密度越大，光合作用和气孔导度对波动光的响应速率越快；相比于二倍体水稻，四倍体水稻气孔大，密度小，光合作用和气孔导度对波动光的响应速率更慢。（2）干旱胁迫下，“水力信号”引起气孔导度和叶肉导度的降低，限制了光合速率；在波动光环境下，干旱胁迫处理可以加快水稻叶片光合作用对光强变化的响应速率，其机理是由于干旱胁迫下气孔的响应加快所致。（3）不同光强处理显著影响水稻叶片结构和稳态光合生理特性，高光处理显著降低了气孔初期的延迟，提高了气孔导度的响应及叶片内 CO2 供应，从而提高了光合作用的响应速率。（4）随着施氮量增加，气孔导度和生化反应过程对波动光的快速响应促进了光合作用的响应速率；随着 CO2 浓度增加，光合作用对光强变化的响应速率逐渐加快，气孔导度的响应速率无明显变化。