四种荒漠植物的光合响应

研究了胡杨（Populus euphratica Oliv）、疏叶骆驼刺（Alhagi sparsifolia B.Keller et Shap)、多枝柽柳（Tamarix ramosissima Lbd)和头状沙拐枣（Calligonum caput-medusae Schrenk)等四种塔克拉玛干荒漠植物的光合响应曲线，结果表明：（1）四种植物中，疏叶骆驼刺光呼吸（Rp)和CO2补偿点（Г）最高，净光合速率（An）以及水分利用效率（WUE）最低；而C4植物头状沙拐枣无论Rp还是Г都最低，它的An、光补偿点（LCP）及光饱和点（LSP）都显著高于其它3种植物（P≤0．05），而且因为非常低的蒸腾速率（E），沙拐枣的WUE也较高。（2）4种植物都为喜光植物，但仍然表现出一定的差异。根据它们光曲线中LCP以及暗呼吸速率（Rd)，4种喜光植物的喜光顺序为：头状沙拐枣，疏叶骆驼枣刺，多枝柽柳，胡杨。（3）柽柳光合响应曲线与日变化中的An,gs等值差异较大，可能是该植物的温度生态位较其它三种植物范围较窄，设置的25℃不在其最适温度范围内，或者是在这个温度下气孔对光强变化的不敏感。（4）综合前人的结果表明，在特定的环境条件，发育阶段以及经过一定的诱导处理，胡杨可以因诱导而表现出一些C4植物特征。

The studies about the photosynthetic response of the four desert plants

Populus euphratica Oliv.、Alhagi sparsifolia B.Keller et Shap.、Tamarix ramosissima Lbd. and Calligonum caput-medusae Schrenk., are all constructive plants in Taklamaka Desert. Responses of photosynthetic parameters of the four desert plants to changes light intensity and CO2 concentration were studied, the results are as follows:①Among the four plants, A. sparsifolia has the highest photorespiration rate (Rp) and CO2 compensation point(Γ), and it has the lowest maximal net assimilation rate(Am) and water use efficiency (WUE) in irradiance responses. On the contrary, as a C4 plant, C.caput-medusa has a lower Rp and Γ,and a significantly higher An, light compensation point(LCP) and light saturation point(LSP) than those of the other plants(P≤0.05), it also had the highest WUE owed much to its very low transpiration rate(E).②According to their LCP and respiration in dark(Rd), we arranged them from sunny to less: C.caput-medusa, A. sparsifolia,T. ramosissima, P. euphratica. And our results also favored the view that relative shade-tolerant plants have higher An in weak light environment than those sun ones.③Further studies are expected to be done on if T. ramosissima has a narrow temperature niche or less stomata sensitivity to irradiance than the other plants. ④Having present a striking contrast between the previously reported results and ours, we suggest P.populus could be inducible for some C4-like characteristics in some special environments, growth stages or under some special treatments.