开放式CO2浓度升高和温度升高交互作用对水稻冠层光合速率影响的模拟研究

Climate change is mainly characterized by atmospheric CO2 concentration elevation and temperature increase, which strongly affect crop growth and yield. As the entry point for carbon assimilation, the impact of global climate change on C3 photosynthesis is a major determinant of overall crop productivity. Crop growth model is very important tool for quantifying the impacts of future climate change on crop growth and yield. However, the current crop growth models cannot predict canopy photosynthesis accurately under future climate change since they do not take into account not only the acclimation response of C3 photosynthesis to long-term the combination of elevated CO2 and elevated temperature, but also leaf senesces accelerated by the combination of elevated CO2 and elevated temperature that result in notable differences among different leaf positions. We will measure photosynthesis at different leaf positions in rice genotypes of different CO2 assimilation efficiency during all stages grown in free-air CO2 enrichment (FACE) system, installed in paddy fields. Biochemical parameters and mesophyll conductance parameters of the C3 photosynthesis model of Farquhar, von Caemmermer and Berry (the FvCB model), and stomatal conductance parameters of a stomatal conductance (gs) model will be estimated, and the acclimation responses of biochemical parameters and conductance parameters to elevated CO2 and increased temperature will be quantified based on field experiments. Based on these quantitative relationships, a model for predicting the impacts of elevated CO2 and increased temperature under future climate change on leaf and canopy photosynthesis in rice crop plants will be developed. The results of this project can improve the mechanism of the existing crop growth model, and facilitate the development of crop growth model which can assess the impacts of climate change on crop growth and yield accurately.

以CO2浓度升高和温度升高为特征的气候变化会直接影响作物生产。作物生长模型是评估气候变化对作物生产影响的重要工具。群体光合作用的模拟是作物生长模型的核心内容之一。已有的作物生长模型没有考虑长期CO2浓度升高和温度升高互作下，C3作物叶片光合速率产生适应性，且冠层不同部位叶片光合速率差异变大，从而影响对群体光合作用的准确模拟。本项目针对此问题，以不同光合效率水稻品种为研究对象，利用国内首个开放式CO2浓度升高和温度升高（T-FACE）系统平台，开展大田实验研究，并将实验观测数据与光合作用机理模型相结合，探究不同光合效率水稻品种植株不同叶位叶片的光合生化参数、叶肉导度和气孔导度对CO2浓度升高和温度升高互作的适应性响应机理及规律，建立交互作用对水稻叶片及冠层光合作用影响的模拟模型。为改善现有作物生长模型的机理性，及进一步建立准确评估气候变化对作物生产影响的作物生长模型提供理论依据和技术支撑。

以CO2浓度升高和温度升高为特征的气候变化会直接影响作物生产。作物生长模型是评估气候变化对作物生产影响的重要工具。已有的作物生长模型没有考虑长期CO2浓度升高和温度升高互作下，C3作物叶片光合速率产生适应性，且冠层不同部位叶片光合速率差异变大，从而影响对群体光合作用的准确模拟。另外，C3作物光合参数对季节性生长温度产生明显的适应性，然而目前仍不清楚现有的作物生长模型是否需要考虑该季节性温度适应，以此来更准确预估未来气候变化背景下作物的生长与产量。针对上述问题，以小麦和水稻为研究对象，利用国内首个开放式CO2浓度升高和温度升高（T-FACE）系统平台，开展小麦和水稻不同叶位叶片光合参数对CO2浓度升高和温度升高的适应性响应，及CO2浓度升高和温度升高背景下小麦和水稻叶片光合作用对季节性温度响应的模型模拟等方面的研究内容。研究结果表明，小麦和水稻叶片光合参数对CO2浓度升高和温度升高响应在叶位之间存在很大的差异，这种差异主要表现为CO2浓度升高和温度升高会更明显降低小麦和水稻中下部叶位的光合能力。然而叶位并不会改变CO2浓度升高和温度升高下小麦和水稻叶片光合参数与叶片氮素积累量的定量化关系。另外，在CO2浓度升高和温度升高背景下小麦和水稻叶片光合参数对季节性生长温度产生明显的适应性，但作物生长模型不考虑该适应性并不会影响对未来气候变化背景下小麦和水稻叶片光合速率的预测。本项目将实验观测数据与光合作用机理模型相结合，估算了CO2浓度升高和温度升高下小麦和水稻不同叶位叶片的光合参数，构建该光合参数与叶片氮素积累的定量关系，及光合参数与季节性生长温度的定量化关系，这些关键数据为建立交互作用对小麦和水稻叶片及冠层光合作用影响的模拟模型，评估光合参数的季节性温度适应对未来气候变化背景下小麦和水稻叶片光合速率的影响提供坚实的数据基础，为改善现有作物生长模型的机理性，进一步建立准确评估气候变化对作物生产影响的作物生长模型提供理论依据和技术支撑。

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