Under pot planting and water controlling condition, the diurnal variations of photosynthetic characteristics of Urtica dioica L. Were measured under 5 different soil water conditions using Li26400 portable photosynthesis system. The results showed 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 maximum value of net photosynthetic rate appeared from 17:00 to 9:00 with the increase of soil moisture. Coordination existed Between daily change process of transpiration rate and dairy change process of stomatal conductance in Urtwa dioica L. And a two peak course was displayed. The order of T3 > T2 > T1 > T4 > T5 was founded in Tr and Gs. The water use efficiency culminated in the early morning. And the water use efficiency in forenoon was higher than that in afternoon.%采用盆栽和人工控制土壤水分的方法,使用LI6400便携式光合测定系统观测了5种土壤水分条件下异株荨麻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,异株荨麻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,随着土壤水分的升高,最高值从下午17:00提前到上午的9:00;蒸腾速率和气孔导度日变化具有较好的协同性,也呈“双峰”型,大小顺序依次为T3处理＞T2处理＞T1处理＞T4处理＞T5处理；水分利用效率最高值出现在上午较早的时段,且上午的水分利用效率明显高于下午.
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