Partitioning of biologically active radiation in plant canopies

Abstract

Plant germination, growth, maturation, and productivity are heavily influenced by the quality and quantity of the light in its environment. The light environment has traditionally been quantified in terms of radiant heat energy and available photosynthetic radiation (PAR), but detailed spectral irradiance or photon flux distributions have rarely been studied. This information is needed to translate the research that plant photobiologists and photochemists have been conducting with regard to understanding the light controls on plant physiology in the field environment of plant canopies. More interest has recently been generated as the potential impacts of global climate changes on intensively managed and natural terrestrial ecosystems are identified and evaluated. Linkages between the identified impacts of various wavelengths of light on plant physiology and the light environment of the plant canopy are identified, with detailed discussion concerning the impacts of plant canopy structure on the plant light response. Solar radiation in the ultraviolet-B (280–320 nm), ultraviolet-A and blue (350–500 nm), PAR (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 from the top of the plant canopy to the photoreceptor at the cellular level within the plant phytoelement.