中文摘要：

运用LI-6400便携式光合测定系统，研究了准噶尔盆地荒漠区2种典型短命植物——狭果鹤虱（Lappula semiglabra）和四齿芥（Tetracme quadricornis）的净光合速率、蒸腾速率和水分利用效率特征。结果表明：狭果鹤虱和四齿芥的光合能力分别为44．92、34．57μmol·m^-2·s^-1狭果鹤虱和四齿芥的净光合速率日均值分别为29．72、23．0μmol·m^-2·s^-1，蒸腾速率日均值分别17．23、12．84mmol·m^-2·s^-1，狭果鹤虱均高于四齿芥，属于高光合、高蒸腾类型；二者的净光合速率和水分利用效率日变化均呈双峰曲线，而蒸腾速率日变化呈单峰曲线；二者的光合“午休”现象主要是由气孔因素引起的；通过对2种植物光合和蒸腾速率与环境因子的相关分析显示，辐射强度是影响2种植物光合速率最主要的环境因子。

英文摘要：

With LI-6400 portable photosynthetic system the net photosynthetic rates,transpiration rates and water use efficiencies of two ephemeral plants,Lappula semiglabra and Tetracrne quadricornis in the Desert Area of the Junggar Basin, were studied. It was shown that the photosynthetic capacities of Lappula semiglabra and Tetracrne quadricornis were separately 44. 92 μmol·m^-2·s^-1 and 34. 57 μmol·m^-2·s^-1;the net photosynthetic rates of the two plants were separately 29.72 μmol·m^-2·s^-1 and 23.0 μmol·m^-2·s^-1 and the transpiration rates of the two plants were separately 17.23 mmol·m^-2·s^-1 and 12. 84 mmol·m^-2·s^-1 ;Lappula serniglabra had a higher photosynthetic rate and a higher transpiration rate than Tetracrne quadricornis did, so that it belonged to the type of plants with high photosynthetic rate and high transpiration rate;the two plants presented the net photosynthetic rates and the water use efficiencies that appeared to vary in a single-peak curve and the transpiration rate that appeared to vary in a doublepeak curve;in the two plants,the midday depression in transpiration mainly resulted from stomatal factors; the analysis of the correlation between the photosynthetic rates and transpiration rates of the two plants indicated that radiation intensity was the most important environmental factor affecting the photosynthetic rates of the two plants.