The Distribution of Stomata and Photosynthetic Pathway in Leaves THE ACTIVITY CHANGES OF NADP-MALIC ENZYME AND ITS REGULATION IN THE TRANSFORMATION C_3 TYPE PHOTOSYNTHESIS INTO CAM TYPE THE COMPARISON RESEARCH OF PEP CARBOXYLASE ISOZYME IN CAM PLANTS Environmental Regulation of CO2 Exchange Pattern in Facultative CAM Plants The Identification of Photosynthetic Subpathways of Some C4 and CAM Plants The Relation Between Activity of Phosphoenolpyruvate Carboxykinase and Photosynthesis in Aloe vera Leaves