Description of Photosynthesis Within Plant Canopies

Abstract

The rate of photosynthesis of individual leaves can be measured by placing the leaf in a transparent chamber and monitoring the difference in CO/sub 2/ content of the ingoing and outgoing air. Using this technique, the rate of photosynthesis associated with any degree of illumination for any temperature, CO/sub 2/ content of air, moisture content, or air velocity can be determined. In plants, however, the concern is primarily with yield per unit of land area. Hence, measurement must be made of the capacity of an arrangement of leaves to utilize the light that falls on an area of land. This introduces the problem of estimating the efficiency with which the light is used in different leaf arrangements or canopies. A basic model in the form of a computer program was developed for the computation of the illumination of leaves at varying areas and leaf angles within the canopy under an ever changing light source. Modifications of the model include computation of the effects of CO/sub 2/ variations; movement of CO/sub 2/ into the canopy from the atmosphere above and the soil beneath, and from layer to layer within the canopy; and change in the assumption of stationary leaves. Parameters tomore » be included in future modifications of the photosynthesis model are discussed.« less