Influence of Instantaneous and Integrated Light-Flux Density on Leaf Anatomy and Photosynthesis

Abstract

Experiments were conducted to examine whether leaf adaptation to light in Fragaria virginiana (Rosaceae) was determined by peak photon-flux density or by total quanta received during the day. Leaf structure and apparent photosynthesis rates were similar under environments where total energy received was the same even though peak photon-flux density was different. When peak photon-flux density was held constant and total quanta varied, significant differences were noted in apparent photosynthesis, leaf thickness, specific leaf weight, mesophyll cell volume, and Ames/A ratio. High total quanta produced high-light or sun-type leaves even at relatively low peak intensities. Thus, total light energy received during the day has a greater influence on leaf adaptation to light than does peak photon-flux density.