Abstract: In this paper the hypothesis that most structural features of leaf can be explained as the adaptation to maximise leaf photosynthesis capacity has been explored. The light envi ronment within leaf is described by the application of the K-M theory and a leaf photo synthesis model incorporating it was presented.Finally, the adaptation of mesophyll stru cture to environmental light condition to maximise leaf photosynthesis was demonstrated by applying optimization theory. Comparing the leaf photosynthesis with different ratios of palisade to spongy tissue showed that there is an optimal ratio (e.g.Kp = depth of pa lisade layer/depth of spongy layer = 0.6), which is very close to actual leaf structure (Table 2). It has been demonstrated by further analysis that the optimal ratio (Kopt) of leaf mesophyll varies with environmental light condition. The fraction of palisade tis sue which makes up the total leaf thickness increases with environmental light intensity, and the optimal ratio (Kopt) depends on the photosynthesis properties of palisade and spongy tissues (Table 3).

Key words: Leaf mesophyll structure, Photosynthesis, Mathematical model, Adaptation to light