上海地区8种落叶阔叶树夏季光合蒸腾特性研究

为了定量评价移栽大苗在夏季光合作用与蒸腾耗水规律，使用LI-6400XT光合仪测定了上海市8个阔叶落叶树种的光合作用特征，对其水分利用效率和光能利用率、主要环境因子、主要光合作用参数日变化、光合生理参数及环境因子的相关显著性等进行比较分析，并揭示其主要影响机理。结果表明:8个树种夏季净光合速率（P_n）日变化均为双峰型，具有明显的“光合午休”现象，峰值分别出现在11:30、15:30，无患子、白玉兰、鹅掌楸具有较高的日均净光合速率，栾树日均净光合速率较低，白玉兰、无患子、榉树、三角枫具有较高的蒸腾速率，栾树蒸腾速率相对较低；8个树种气孔导度日变化在测定时段均为双峰型，胞间CO₂浓度日变化呈“W”形；榉树、栾树、白玉兰、鹅掌楸午间P_n的下降为气孔限制，无患子、三角枫、悬铃木、银杏在午间的P_n下降为非气孔限制；鹅掌楸、无患子、银杏、白玉兰具有更高的水分利用效率，分别为4.173、3.976、3.742、3.638 μmol·mmol^-1，无患子、白玉兰和鹅掌楸光能利用效率较高，分别为0.767%、0.699%、0.525%；在树种配置时，白玉兰、无患子光和蒸腾作用较强，可作为优选绿化树种，栾树较弱，可适量引种并注意与其他树种的搭配，同时要注意绿化树种特殊观赏特性的应用与植物景观的时间与空间搭配。

Photosynthetic and Transpiration Characteristics of Eight Deciduous Broad-leaved Trees in Summer in Shanghai

In order to quantitatively evaluate the water consumption of transplanting seedlings by transpiration and photosynthesis law in summer, LI-6400XT photosynthetic apparatus was used to determine the photosynthetic characteristics of 8 deciduous broad-leaved trees in summer of Shanghai. Comparative analyses were conducted on the indices such as water use efficiency (WUE) and light use efficiency, main environmental factors, diurnal variations of main photosynthetic parameters, photosynthetic parameters and their correlations to the environmental factors, to reveal the main the mechanism of the impact. The results showed that the diurnal variations of the net photosynthetic rate（P_n）of 8 species were in bimodal shape, with obvious “midday depression” phenomenon, the peak values appeared at 11:30 and 15:30, respectively. Sapindus mukorossi, Magnolia denudate, Liriodendron chinense had higher average daily P_n, and lower for Koelreuteria paniculata. M. denudate, S. mukorossi, Zelkova schneideriana, Acer buergerianum had higher transpiration rate, relatively low for K. paniculata. The diurnal variation curves of stomatal conductance of 8 species were all in bimodal shape during the measurement period. Intercellular CO₂ concentration diurnal variations were in “W” shape. The decreases of P_n of Z. schneideriana, K. paniculata, M. denudate, and L. chinense were stomatal limitation, while for S. mukorossi, A. buergerianum, Platanus Linn., and Ginkgo biloba, the decreases were nonstomatal limitation. L. chinense, S. mukorossi, G. biloba, M. denudata had higher WUE, 4.173, 3.976, 3.742, and 3.638 μmol·mmol^-1, respectively. The light use efficiencies of S. mukorossi, M. denudate and L. chinense were higher, 0.767%, 0.699%, and 0.525%, respectively. When referring to the tree configuration, the photosynthesis and transpiration of M. denudate, S. mukorossi were stronger, which could be used as optimizing greening tree species. K. paniculata exhibited low capability in photosynthesis and transpiration, it could be introduced appropriately, and mixed with other species. More attention should also be paid to the application of special ornamental characteristics, and to time and spatial coordination of plantscape.