Abstract: The yield of all green plants is closely related to their photosynthetic capacity. The same is true to tea trees. It was calculated that the photosynthetic capacity of an interplanted tea stand was 4. 6% higher than that of a monoculture tea plantation. Accordingly, the former could have higher yield of tea leaves than the latter. Transpiration of tea plants also affects directly the quality of their leaves. As transpiration increases, the tea leaves become aged, resulting in deterioration of their quality. Our investigation conducted in Xiashu Forest Station, Nanjing Forestry University, indicates that the daily transpiration of the pure tea plantation was 23. 54% higher than that of the interplanted tea stand in summer which produced better quality tea leaves.