Abstract: The physiological and biochemical properties of dendrobium offcinale of orchidaceous plant were studied.The properties of Dendrobium offcinale,soybean of the typical C_3 plant,corn of the C_4 plant and cactus of the CAM plant were compared. The results show that, the value of chlorophyll a/b of Dendrobium offcinale is lower,it is similar to the change of pH between Dendrobium offcinale and cactus, which is from lower to higher a daytime and reverses at night.It fluctuates day and night . The PEPCase activi...