Introduction in the A central objective of plant ecology is to understand the causes of patterns distribution and abundance of species. Physiological ecologists advance this goal by studying how various morphological and physiological properties permit a plant to survive and compete successfully in certain environments but not in others. Physiologi- cal ecology thus provides an important window on the proximal mechanisms that under- lie species differences in distribution and habitat-specific competitive ability chemical Photosynthetic energy capture provides green plants with almost all of their in energy, and is central to their ability to compete and reproduce. Photosynthesis, turn, is directly and dramatically influenced by the amount of light striking a plant's leaves. Many investigators have therefore studied how different levels of irradiance by photosynthetically active radiation affect photosynthesis, and the leaf traits that how develop under different levels of irradiance influence a plant's photosynthetic response to light level. Comparative studies of the photosynthetic response and leaf character istics of plants grown under high and low levels of irradiance have provided crucial 0310-7841/88/010063$03.00