Effects of O

The effects of elevated O3 (O3) on photosynthetic characteristics of urban trees were studied in an open-top air chamber. The results showed that net photosynthetic rate (Pn), transpiration rate (Et), stomatal conductance (Gs) and water use efficiency (WUE) of different tree species decreased significantly with the increase of O3 concentration, while intercellular CO2 (Ci) concentration of different tree species increased significantly with the increase of O3 concentration. Under different O3 concentrations, the net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration of Ginkgo biloba (G. biloba) and Koelreuteria paniculata (K. paniculata.) were higher than those of Pinus bungeana (P. bungeana) and Platycladus orientalis(P. orientalis), and the WUE of P. bungeana and P. orientalis was higher than that of G. biloba and K. paniculata. The effect of elevated O3 concentration on plant photosynthesis is more obvious in K. paniculata and G. biloba