Abstract
(1) The maximum rate of photosynthesis on leaf area (Pmax) increases with leaf development and peaks at around the full leaf area expansion (FLE) in annual herbs. But, in evergreen trees, Pmax at FLE is very low and continues to increase for another two to three weeks. Cell division and chloroplast division continued to the later stages in leaf development and thereby chloroplast maturation occurs well after FLE. Competition for resources and energy among these developmental processes would explain the delayed maturation in evergreen tree leaves.
(2) Sun leaves have thicker palisade tissue. In flush-type deciduous trees, number of cell layers in the palisade tissue is determined by the light environment when leaves develop in the winter bud. Similarly, in annual herbs, the layer number in developing leaves is determined by light environment of the mature leaves. But, sun/shade chloroplast development depends on current, local light environment.
