We studied the effects of foliage architecture on crop photosynthesis through the CO_2 diffusion in the canopy by the following method. The effect of different characteristics of foliage architecture (i.e., leaf inclination, leaf size in respect of width, leaf area profile) on crop photosynthesis was simulated by using each coefficient concerned with the CO_2 diffusion in a canopy described in our previous paper (Hirota & Takeda 1987). The results of the study are summarized as following; Photosynthetic rate of the canopy which had spindle-shaped leaf area profile was about 1% higher than that of the canopy which had a mushroom-shaped. The leaf inclination affected both the light extinction coefficient (k) and the wind speed attenuation coefficient (β) in the canopy. When the photosynthesis light response curve of the C_3 plant was used for simulating the crop photosynthesis, the erectophile canopy was superior in crop photosynthesis to the planophile canopy because of the former’s smaller k. When the G-light curve was used, on the contrary, the planophile canopy was better in crop photosynthesis than erectophile canopy, because leaves having G-light curve (not saturated) had higher photosynthetic rates at a high light intensity; and the planophile canopy was also superior to the erectophile canopy in CO_2 diffusion. Photosynthetic rate of a canopy with narrow leaves (1 cm wide) was about 3% higher than that of a canopy with broad leaves (9 cm diameter).
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