The net photosynthetic rate(Pn), stomotal conductance(gs), transpiration rate (E)and water use efficiency (Wue) were measured using a LI-6400 portable photosynthesis system for Pinus massoniana. In this experiment, the CO_2 concentration were set at three levels: 360 μmol·mol~(-1)?800 μmol·mol~(-1)?1 200 μmol·mol~(-1). The result showed that: under present CO_2 concentration(360 μmol·mol~(-1)) and 1 000 μmol·m~(-2)·s~(-1) of light intensity, the Pn of conifer leaves are 3.46 μmol·m~(-2)·s~(-1), E are 0.273 mmol.m~(-2).s~(-1), gs a...