中文摘要：

在开顶式小型温室内模拟大气CO2浓度增高,并在N0,N100,N200计3个氮素水平〔施N量分别为纯N0、0.1、0.2 g/kg（土）〕下盆栽小麦,研究小麦光合作用和水分利用效率（WUE）对大气CO2升高的响应及其氮素调控机制。结果表明,760μmol/molCO2浓度×N素小麦叶片的净光合速率、叶片胞间CO2浓度、气孔限制值及叶片水分利用效率较对照呈明显上升趋势,叶片气孔导度显著降低,蒸腾速率则呈先降后升的趋势;在400μmol/molCO2浓度下,N0和N100处理的小麦光合速率明显下降,但N200处理较当前CO2浓度处理明显升高;气孔导度,胞间CO2浓度以及蒸腾速率呈现下降的趋势,小麦的气孔限制值Ls和WUE在N200条件下表现最高,较各个处理均达到极显著水平。两种大气CO2浓度下的小麦叶片光合速率和气孔导度均随氮素水平的升高而明显升高,胞间CO2浓度和蒸腾速率表现均不一致。因此,长期高CO2浓度使得小麦叶片WUE和Ls值显著升高,在低中氮处理下产生明显的光合下调现象,但在高氮处理下却不发生。

英文摘要：

The top-open chamber was used to simulate elevating atmospheric CO2 concerntration,where wheat（Triticum aestivum L.） was grown under different N application levels and atmospheric CO2 concerntration to study the response of wheat photosynthesis and water use efficiency（WUE） to the change of these two factors and the regulation mechnism of nitrogen application.The results showed that the net photosynthetic rate（Pn）,intercellular CO2 concentration（Ci）,stomatal limitation value（Ls） and WUE were increased,but stomatal conductance（Gs） decreased gradually,while,transpiration rate（Tr） decreased first and then increased with nitrogen levels increasing under high atmospheric CO2 concentration conditions.Compared to ambiment atmosphric CO2 treatments,Pn was decreased significantly in 0 and 0.1 g N/kg（soil） treatments and significantly increased in 0.2 g N/kg treatment with different atmospheric CO2 concerntration,while Gs,Ci and Tr were decreased.Ls and WUE got to the highest in 0.2 g N/kg,and the differences were significant compared to the other treatments.Pn and Ls were significantly increased with nitrogen levels under the condition of different atmospheric CO2 concerntration.but the response of Ci and Tr were inconsistent.So,WUE and Ls was significantly increased under long-term high CO2 concentration.The photosynthetic down-regulation occured in 0 and 0.1 g N/kg,but not under 0.2g N/kg treatment.