By taking six families ofSloanea hemsleyana as the tested materials, theirs four kinds of photosynthetic parameters were and monitored and measured, the photosynthetic characteristics of different families were comparatively studied through continuous monitoring in order to provide theoretical basisfor the selection and protection ofS. hemsleyana superior family. The studying results show that there were signiifcant differences of net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentra...