氮素增强水稻光合作用抗高温能力的生理机制研究

Enhancing the tolerance of photosynthesis to high temperature stress is of vital importance for improving the food security. In this research, the effects of nitrogen and high temperature stress (40 oC) on photosynthesis in pot-grown rice species will be studied, to understand the mechanisms of the improved high temperature tolerance of photosynthesis by nitrogen. A systematic investigation will be conducted considering the limitations to photosynthesis by stomatal conductance (gs), mesophyll conductance (gm), and Rubisco carboxylation capacity. It will facilitate us to study the effects and mechanisms of high temperature stress on photosynthesis, and to clarify the mechanisms that nitrogen enhances the tolerance of photosynthesis to the stress. After that, the effects of temperature stress on Rubisco activity, and Rubisco activase content will be studied to evaluate their correlations with photosynthesis. In addition, the interactive effects of nitrogen and high temperature stress on gs will be studied. This will allow us to evaluate the influences of leaf morphology and anatomy, and the permeability of membrane on gs and its response to temperature stress, and to clarify the mechanism for a less depression on gs by high temperature with nitrogen. Finally, the interactive effects of nitrogen and high temperature stress on gm will be studied. The effects of leaf anatomy on gm and its response to high temperature will be systematically investigated, and the relationship between gm and the tolerance of photosynthesis to high temperature will be evaluated. The findings can fully explain the reasons for the enhanced high temperature tolerance of photosynthesis by nitrogen, and can provide theoretical basis for breeding rice cultivars that are tolerant to high temperature stress, and also can provide theoretical basis for reducing the decreases in crop yield and nitrogen use efficiency by high temperature stress.

提高光合作用抗高温能力对保障粮食安全具有重要意义。本项目拟运用盆栽试验研究氮素与高温互作对水稻光合作用的影响与机理。首先研究氮素与高温互作对光合作用各限速步骤的影响规律，阐明高温对光合作用的影响与机理，解析氮素缓解高温抑制的途径。然后研究高温对不同氮处理Rubisco酶活性、Rubisco激酶含量的影响规律，阐明它们与光合作用抗高温能力的关系。随后研究氮素与高温互作对气孔导度（gs）的影响与机理。阐明叶片形态与解剖结构、膜透性等能否通过调节叶片水力导度来影响gs及其对温度的响应，解析氮肥缓解高温对gs影响的内在机理；最后研究氮素和高温互作对叶肉导度（gm）的影响与机理。阐明叶片解剖结构等能否调节gm及其对温度的响应，探讨gm与不同氮处理光合作用抗高温能力的关系。项目成果能够阐明氮素增强光合作用抗高温能力的机制，解析水稻抗高温的叶片结构特性，为缓解高温下产量和氮肥利用效率的降低提供理论依据。

高温胁迫是限制水稻生长和光合作用的主要环境因子之一，增强光合作用的抗逆能力对于保障粮食安全具有重要的意义。光合作用对于温度的变化非常敏感，光合速率一般在25—30 oC 之间达到最高值，高于或低于此最适温度光合速率均会显著降低。在本研究中，我们重点探讨了不同氮肥处理下水稻光合作用对高温的响应差异及其生理机制，并运用最优化气孔模型系统分析了不同水稻品种气孔导度对温度的响应差异及其内在机理，解析了叶片水势如何影响光合作用对温度的响应以及运用两相模型探究了水稻叶肉导度对温度的响应机理，阐明了水稻光合作用对温度的响应规律及其内在生理机制。主要结果包括：（1）氮素能够缓解高温对水稻光合作用抑制的生理机制，主要原因是高氮能够缓解高温下气孔的关闭；（2） 运用最优化气孔模型探究气孔导度对温度的响应规律及其生理机制，发现气孔导度对温度的响应规律与光合作用的限制因子有关；（3）阐明了叶片水势调控光合作用对温度的响应及其机理，高温下水势的下降抑制了叶肉导度对温度的响应能力；（4）揭示了光合作用与叶片水力导度对温度的响应机制，发现不同温度下叶片水势的变化能够影响叶片水力导度对温度的响应规律；（5）氮素和生育期会影响水稻光合作用和叶肉导度对温度的响应与机理研究，分蘖期叶肉导度对温度变化更为敏感；（6）不同C3作物叶肉导度对温度的响应差异及其与叶片结构的关系，叶肉导度对温度的敏感性与叶绿体的比表面积呈显著的正相关关系。我们的研究结果能够为提高作物光合作用的抗高温能力提供理论支撑。