Structure of Foliage Canopies and Photosynthesis

All living things on the earth, including plants, rely principally upon the photosynthate produced by plants for their daily food, and accordingly are strongly affected by the variation of plant photosynthesis over the globe. The distribution of solar energy with latitude determines to a great extent the geographic variation of photosynthetic activity of plants. Its latitudinal change in turn sets broad geographic limits to the different forms of terrestrial life, affecting the energy flow and the cycle of materials in ecosystems. On the other hand, the morphological and physiological characteristics of plants are thought to result from their evolutional adaptation to environmental conditions during the geological past. The morphological features as characterized by the geometrical structure (or architecture) of plant canopies have a great influence upon the processes of action and reaction between plants and their environment through the modification and interception of fluxes of radiation, heat, carbon dioxide, etc. Consequently it is obvious that the canopy structure is determinant of the photosynthetic productivity of plant canopies. The canopy structure as well as the physiological properties of leaves with respect to photosynthesis and respiration, therefore, can play an important role in the competition between plants. Since the relation between the photosynthetic activity and the structure of plant canopies was elucidated by Monsi & Saeki (100) in 1953, a great number of both theoretical and experimental studies have been done on this problem. Studies in this field have been greatly stimulated by the activities of the International Biological