水是影响荒漠植物生存、生长和分布的重要环境因子。C3-C4中间型植物特有的叶片结构和光合生理生化特性，将为全面理解植物应答水分胁迫时光合碳同化途径的适应性变化提供新的视野。本研究以荒漠C3-C4中间型植物松叶猪毛菜和白枝猪毛菜为研究对象，C3植物天山猪毛菜和C4植物木本猪毛菜为对照，通过水分胁迫试验研究水分胁迫下植物的叶片显微、超微结构、光合生理特性和水分利用效率，明确C3-C4中间型植物是否通过增强C4光合途径的表达程度来适应水分胁迫，并通过调整植物叶片结构和光合生理特征来适应；揭示水分胁迫下C3-C4中间型植物和C3、C4植物的光合碳同化途径的适应性变化的差异；探讨水分胁迫下C3-C4中间型植物光合碳同化途径的适应性变化规律。预期成果有助于理解荒漠C3-C4中间型植物在干旱环境下的适应策略，对深入研究干旱区植物响应环境因子及其适应机制具有重要意义。

Water is one of the important environmental factors which affects the survival, growth and distribution of desert plants. C3-C4 intermediate plants have the particular leaf structures and photosynthetic physiological and biochemical characteristics. They provide a new view of understanding the transition of photosynthetic carbon assimilation pathway from C3 to C4 under water stress. In this study, four species including two C3-C4 intermediate species, Salsola laricifolia and Salsola arbusculiformis, and C3 species Salsola junatovii and C4 species Salsola arbuscula as controls, are studied using water-stressed test. Leaf microstructure and ultrastructure, photosynthetic physiological characteristics and water use efficiency are researched under water stress, with a focus on the following aims: 1) identifying whether the C3-C4 intermediate plants adapt to water stress by enhancing the expression levels of the C4 photosynthetic pathway through changes of leaf strctures and photosynthetic physiological characteristics; 2) comparing the differences of photosynthetic carbon assimilation pathway among C3, C4 and C3-C4 intermediate plants under water stress; 3) exploring adaptative mechanism of plant photosynthetic carbon assimilation of C3-C4 intermediate plants under water stress. The expected results will contribute to understanding adaptative strategies of the desert C3-C4 intermediate plants in arid environments, and studying intensively how desert plants response to environmental factors and their adaptive mechanisms.