title: Influence of PAR and UV-A in determining plant sensitivity and photomorphogenic responses to UV-B radiation.
abstract: The role of photosynthetically active radiation (400-700 nm) (PAR) in modifying plant sensitivity and photomorphogenic responses to ultraviolet-B (280-320 nm) (UV-B) radiation has been examined by a number of investigators, but few studies have been conducted on ultraviolet-A (320-400 nm) (UV-A), UV-B and PAR interactions. High ratios of PAR-UV-B and UV-A-UV-B have been found to be important in ameliorating UV-B damage in both terrestrial and aquatic plants. Growth chamber and greenhouse studies conducted at low PAR, low UV-A and high UV-B often show exaggerated UV-B damage. Spectral balance of PAR, UV-A and UV-B has also been shown to be important in determining plant sensitivity in field studies. In general, one observes a reduction in total biomass and plant height with decreasing PAR and increasing UV-B. The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The quality of PAR is also important, with blue light, together with UV-A radiation, playing a key role in photorepair of DNA lesions. Further studies are needed to determine the interactions of UV-A, UV-B and PAR.
authors.affiliation: Climate Stress Laboratory, Natural Resources Institute, Agricultural Research Service, US Department of Agriculture, Beltsville, MD 20705-2350, USA. krizekd@ba.ars.usda.gov
authors.forename: Donald T
authors.initials: DT
authors.lastname: Krizek
mesh_terms: D004260:DNA Repair; D018744:DNA, Plant / Q000528:radiation effects; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects*; D063245:Plant Development; D018515:Plant Leaves / Q000254:growth & development / Q000528:radiation effects; D018521:Plant Physiological Phenomena / Q000528:radiation effects*; D010944:Plants / Q000528:radiation effects*; D011827:Radiation; D011836:Radiation Tolerance; D012993:Solar Energy; D014466:Ultraviolet Rays
chemical_list: D018744:DNA, Plant; D005419:Flavonoids; D010636:Phenols