Abstract: Leaf gas exchange, titratable acidity and chlorophyll content were measured in Vanilla planifolia cultivated in artificial shading condition during four different seasons. The relationship between different leaf ages and photosynthetic types and seasonal variations were researched in detail. The mature leaves perform stable Crassulacean Acid Metabolism (CAM), which uptake and rarely release CO2 for most times during the light period, and express marked diurnal acid fluctuation.

Key words: Vanilla planifolia