Abstract:

The photosynthetic characteristics of Cinnamomum camphora and its response to CO₂ enrichment in subtropical evergreen broadleaf forest area were investigated using Li-COR 6400 portable photosynthesis system. The results showed that the diurnal net photosynthetic rate of C.camphora in sunny day varied with double peak curves. The peaks occurred at 10:00 and 14:00 respectively. There was a significant midday depression. Stomatal factors, such as the stomatal conductance, were the main causes of the depression. At midday, light intensity was the largest, vapor pressure deficit between leaves and air reached maximum, but air relative humidity, stomatal conductance and intercellular CO₂ concentration were minimum, and hence photosynthetic middy depression occurred. The light compensation point and light saturation point of leaves at the ambient CO₂ concentration were 40.6 μmol·m^-2s^-1 and 1 250 μmol·m^-2s^-1 ,respectively. When light intensity reached 1 000 μmol·m^-2s^-1 and ambient CO₂ concentration, its CO₂ compensation point and CO₂ saturation point were 50 μmol·mol^-1 and 1 200 μmol·mol ^-1 ,respectively. With the increases of light intensity, water use efficiency, sotmatal conductance and transpiration rate were improved at different CO₂ concentration. And in 24～35℃,the net photosynthetic rate showed a decreasing trend with the temperature and photosynthetic active radiation increasing.

Key words: Cinnamomum camphora, Photosynthetic rate, CO₂concentration, Temperature