关键词: 南方岩榆, 光合作用, 日变化, 影响因子

Abstract: Taking the one-year seedlings of Ulmus crassifolia as subjects, which were introduced from America and cultivated in the field, the daily courses of its net production rate (Pn), transpiration rate (Tr) and water utilization efficiency (WUE) in leaves, and its influencing factors were studied under natural condition.The results showed that the curve of Pn diurnal variation was a single peak and its peak value appeared at 11:00;Tr daily courses of leaves from different parts were obviously one-peak curves.Tr peak values of both middle and bottom leaves appeared at 13:00 and peak value of top leaves came out at 15:00 and the descending order of Tr peak values was middle leaves, bottom leaves, top leaves;WUE daily courses of leaves from different parts all presented a one-peaked curve decreasing at one side, WUE of middle and bottom leaves lower than those of top leaves.By main component analysis, path coefficient analysis, or multiple return analysis, major physiological and ecological factors affecting Pn were temperature, Vpdl and light intensity;the influencing factors of Tr and WUE were temperature and Vpdl.

Key words: Ulmus crassifolia, photosynthesis, daily variation, influencing factor