中文摘要：

揭示作物光合作用、蒸腾作用和水分利用效率（WUE）对大气CO2浓度变化的响应,对预测未来大气CO2浓度升高条件下作物生产力与需水规律的变化具有重要意义。在自然CO2浓度、CO2倍增和倍增后恢复到自然CO2浓度3种情况下,对大豆（Glycine max）、甘薯（Ipomoea batatas）、花生（Arachis hypogaea）、水稻（Oryza sativa）、棉花（Gossypium hirsutum）、玉米（Zeamays）、高粱（Sorghum vulgare）和谷子（Setaria italica）8种作物的气体交换参数进行了研究。结果表明：CO2浓度倍增可以提高光合速率,降低蒸腾速率,从而提高WUE,其中光合速率提高的贡献更大;C3比C4作物的光合速率、WUE增幅大,C3作物光合速率提高对WUE的贡献大于C4作物;通过对比倍增后恢复到自然CO2浓度时气体交换参数随环境条件变化的响应确定了其内在调控机制;倍增后恢复到自然CO2浓度时作物光合速率低于自然CO2浓度下的光合速率,而蒸腾速率无明显差异。由此判断：CO2浓度倍增下存在光合下调现象,这可能是由于Rubisco酶蛋白含量、活化水平和比活性降低等＂非气孔因素＂造成的,并非由气孔导度的降低引起的。

英文摘要：

Aims Our objective was to elucidate the response of crop photosynthesis,transpiration and water use efficiency to atmospheric CO2 concentration.This has great significance to predicting crop productivity and water-demand changes under increasing atmospheric CO2 concentration.Methods The photosynthesis rate,transpiration rate and water use efficiency of eight crops（soybean（Glycine max）,sweet potato（Ipomoea batatas）,peanut（Arachis hypogaea）,rice（Oryza sativa）,cotton（Gossypium hirsutum）,corn（Zea mays）,sorghum（Sorghum vulgare） and millet（Setaria italica）） were studied under natural CO2 concentration,doubled CO2 concentration and natural CO2 concentration after doubled CO2 conditions.Important findings Doubled CO2 concentration increased the photosynthesis rate and decreased the transpiration rate,and therefore water use efficiency was more significantly increased.The increase of water use efficiency showed greater dependence on the increase of photosynthesis rate than the decrease of transpiration rate.The variations of photosynthesis rate and water use efficiency of C3 crops were larger than those of C4 crops.The effect of photosynthesis rate of C3 crops on the water use efficiency was larger than that of C4 crops.The photosynthesis rate under natural CO2 concentration after doubled CO2 concentration was lower than that under natural CO2 concentration,but no significant difference was found for the transpiration rate.The photosynthetic capacity under natural CO2 concentration after doubled CO2 concentration was decreased mainly by the decreasing of some non-stomatal factors,including the protein content,activation levels and specific activity of the enzyme Rubisco.