中文摘要：

土壤水分条件能够改变叶片呼吸作用,进而影响叶片、个体及生态系统的碳平衡。在内蒙古自治区额济纳旗境内,根据地下水埋深度的差异建立了干旱和湿润2块样地,并对其中生长的胡杨（Populus euphratica）叶片的呼吸作用特性进行了观测。结果表明,干旱样地胡杨叶片的相对含水量（RWC）和单位质量氮含量（Nmass）显著低于湿润样地,但叶片单位面积氮含量（Narea）和比叶面积（SLA）差异不显著。叶片暗呼吸速率（Rn）和光下线粒体呼吸速率（RL）均随地下水埋深的降低而升高,其中地下水埋深度的变化对RL影响更加明显。光对叶片暗呼吸速率具有抑制作用,其抑制程度在11%—57%变化。光对暗呼吸的抑制程度同Rubisco酶的最大氧化速率（vo）呈负相关。湿润样地胡杨叶片光合速率（A）同光下线粒体呼吸速率的比值（A/RL）显著高于A同Rn的比值（A/Rn）,而在干旱样地2者间差异不显著。胡杨叶片呼吸速率和光对暗呼吸抑制作用对地下水埋深的响应可能同细胞抗旱对能量和物质需求的增加有关。此外,叶片A/R比值不仅受到光照条件的影响,同时受到水分条件的调控。

英文摘要：

Soil water availability affects leaf respiration, thereby influencing leaf, plant individual and ecosystem carbon balance. Two sites with different depth to underground water table （Dry site and wet site） were established in Ejina Banner, Inner Mongolia, and leaf respiratory characteristics of Populus euphratica were investigated. The results showed that leaf relative water content （RWC） and mass-based nitrogen content （Nrnass） were lower at the dry site than those of the wet site. However, no significant difference was found on area-based nitrogen content （Narea） or specific leaf area （SLA）. Leaf respiration rates （R） in darkness （Rn） and under daylight （RL） were both higher at the dry site, with the increased R being more evident for RL. Leaf R was inhibited by light at both sites （e.g. RL〈Rn）, with the inhibitory effect ranging from 11% to 57% and it was negatively correlated with the rates of Rubisco oxygenation at saturated irradiance （Vo）. The ratio of photosynthetic rate （.4） to RL （A/RL） was significantly higher than the ratio of A to Rn （A/Rn） at the wet site, while no significant difference was found between the two parameters at the dry site. Water induced upregulation of leaf R and the response of light inhibition of dark respiration to underground water table may result from the increased cellular metabolic demand on energy and carbon skeleton for drought resistance. Furthermore, A/R ratio was not only associated with light but also strongly manipulated by soil water availability.