EFFECTS OF PLANT CANOPY STRUCTURE ON LIGHT INTERCEPTION AND PHOTOSYNTHESIS

A set of different plant canopies with vertically different and horizontally clumped leaf areal density was generated on a mainframe computer. Three-dimensional transfer of direct light in these canopies was numerically calculated and the irradiance of light on inclined leaf surfaces was predicted. Using this information the daily gross photosynthesis of the canopy was estimated. The effects of spatial distribution of leaf areal density and of leaf orientation on light interception and photosynthesis were analyzed. The distribution of leaf areal density affects the spatial distribution of sunflecked leaf area, while leaf orientation affects both the spatial distribution of sunflecked leaf area and the distribution of light irradiance on leaf surfaces. The results show that the influence of spatial distribution of leaf areal density is only about 1-8% of daily total canopy photosynthesis, and that leaf orientation has much greater effects on canopy photosynthesis. At summer solstice and lower latitudes, erectophile leaves could produce up to 25% higher daily photosynthesis in the canopy than planophile leaves.