PARTITIONING OF BIOLOGICALLY-ACTIVE RADIATION IN PLANT CANOPIES

Plant germination, growth, maturation, and productivity are heavily in fluenced by the quality and quantity of the light in its environment. The light environment has traditionally been quantified in terms of ra diant heat energy and available photosynthetic radiation (PAR), but de tailed spectral irradiance or photon flux distributions have rarely be en studied. This information is needed to translate the research that plant photobiologist and phytochemists have been conducting with regar d to understanding the light controls on plant physiology in the field environment of plant canopies. More interest has recently been genera ted as the potential impacts of global climate changes on intensively managed and natural terrestrial ecosystems are identified and evaluate d. Linkages between the identified impacts of various wavelengths of l ight on plant physiology and the light environment of the plant canopy are identified, with detailed discussion concerning the impacts of pl ant canopy structure on the plant light response. Solar radiation in t he ultraviolet-B (280-320 nm), ultraviolet-A and blue (350-500 nm), PA R (400-700 nm), blue (400-500 nm), green (500-600 nm) red (600-700 nm) , far red (700-800 nm) and near infrared (800-1100 nm) is followed fro m the top of the plant canopy to the photoreceptor at the cellular lev el within the plant phytoelement.