PHOTOSYNTHETIC CHARACTERISTICS IN LEAVES OF LITCHI CHINENSIS

Plants of Litchi chinensis were grown under greenhouse conditions that were controlled to mimic natural environmental condition. Net photosynthesis increased with increasing incident quantum flux from 0 to 0.15 m mol m^-2s^-1, PN=10.32p+0.14. Photosynthetic light compensation point occurred at 0.02 m mol m^-2s^-1 photon and photosynthesis rate of 1.76 μ mol m^-2s^-1 was measured at irradience of 0.7 m mol m^-2s^-1 photon. Leaf conductance to water vapor and transpiration also increased as the incident quantum flux increased from 0 to 0.15 m mol m^-2s^-1 photon.Litchi leaves were not so much sensitive to change in the leaf to air water vapor gradient. In this humidity range, leaf conductance decreased slightly, G=-0.28⊿W+35.2.Net photosynthesis increased as intercellular CO₂ concentration increased from 0 to 230 μ1 1^-1and the projected CO₂ compensation point was approximately 38.5μ1 1^-1.There was a small dependence of net photosynthesis on leaf temperature beween 22 to 6℃. Photosynthetic rate decreased rapidly at the temperature above 30℃.These results suggest that lower net photosynthesis may be alimited factor of the growth of plant and under natural field condition photosynthesis in leaves of Litchi is likely to be reduced by high temperature that commonly occure during midday periods in summer.