中文摘要：

采用盆栽和人工控制土壤水分的方法,使用Li-6400便携式光合测定系统观测本氏针茅（Stipa bungeana）光合生理生态特征的日变化。结果表明：在不同土壤水分状况下,本氏针茅净光合速率日变化曲线均呈＂双峰＂型,并有不同程度的＂午休＂现象,且上午的净光合速率明显高于下午,随着土壤水分的升高而增加;蒸腾速率日变化曲线也呈＂双峰＂型,表现为较高土壤水分处理针茅具有较高的蒸腾速率;气孔导度受水分和光热胁迫的影响,日变化曲线呈凹型;胞间CO2浓度受空气CO2浓度和气孔导度的双重影响,呈现早晚高,正午低的日变化进程;水分利用效率最高值出现在上午较早的时段,随着土壤水分的增加,水分利用效率却降低。

英文摘要：

The diurnal variations of photosynthetic characteristics of Stipa bungeana Trin. were measured under pot planting and water controlling condition using the Li-6400 portable photosynthesis system. The results show that the diurnal course of net photosynthetic rate was displayed in a two-peak pattern with a typical midday depression pattern under different drought stress; the net photosynthetic rate in forenoon was higher than that in afternoon and increased along with the raising of soil moisture. The diurnal course of transpiration rate was also displayed in a two-peak course and the higher transpiration rate was corresponding to the higher soil moisture. The stomatal conductance was affected by soil moisture and stress of light and heat, and the diurnal dynamics was a concave form. The intercellular COz concentration was affected by the atmosphere COz concentration and stomatal conductance with higher value in morning and evening and lower in midday. The water use efficiency culminated in the early morning and decreased along with the raising of soil moisture.