Abstract: The experiments were made with Dendrobium huoshanense. It was studied that photosynthesis and chlorophyll fluorescence of D. huoshanense. The results indicated that there were positive correlation between daily
change of photosynthesis and it of light intensity under cultivation environment of forest shadow , as well as photosynthesis rate was low. Low light intensity is the reason to result in low growth of D. huoshanense and is not suitable
light intensity for dendrobium growth in forest shadow. Daily change of photosynthesis represents V type and there is the lowest photosynthesis at noon under natural light . From 9 : 00 to 17 : 00 photosynthesis is negative value and there is no photosynthesis accumulation , as well as there is photosynthesis accumulation only during low light intensity on morning or night . Daily change of chlorophyll fluorescence shows that light intensity beyond 800 μmol·m^-2·s ^-1 is not suitable to grow dendrobium , because strong photoinhibition of photosynthesis is occurred before negative
photosynthesis accumulation when the light intensity is beyond 800 μmol·m^-2·s ^-1 in natural light . The experiments controlling light intensity show that ETR rises rapidly , rate of electronic transmission of photosynthesis and NPQ increase , light energy can be used effectively and surplus light energy can be dissipate at 500μmol·m^-2·s ^-1 light intensity as well as dendrobium has much better responsibility for light .

Key words: Dendrobium huoshanense, Photosynthesis, Chlorophyll fluorescence parameters, Photoinhibition