Photosynthesis in Plant Communities as Influenced by Leaf Angle1

Abstract

Flats of barley were seeded at three different rates and tilted at 0°, 30°, and 60° from the horizontal. When the first leaf had developed the flats were returned to the horizontal for measurements of photosynthesis, light penetration, and leaf area index. This method produced flats with uniform leaf angles of 90°, 53°, and 18° at different leaf areas.Results showed that differences in net photosynthesis, due to leaf angle, increased as leaf area index (ratio of leaf area to soil area) increased above two. The vertical leaves had a higher Pn and allowed more light to penetrate at high LAI's than horizontal leaves. Leaves at 90° required a leaf area index of 11 to intercept 95% of the light; 53° and 18° leaves intercepted 95% of the light at LAI's of 7 and 4.5, respectively. The mean extinction coefficients were 0.32, 0.45, and 0.60, respectively, for leaves 90°, 53° and 18° to the horizontal.When data from these experiments were analyzed in equations proposed by Saeki to predict the net photosynthesis of a plant community, the predicted results closely approximated experimental results.