title: Alteration of foliar flavonoid chemistry induced by enhanced UV-B radiation in field-grown Pinus ponderosa, Quercus rubra and Pseudotsuga menziesii.
abstract: Chromatographic analyses of foliage from several tree species illustrate the species-specific effects of UV-B radiation on both quantity and composition of foliar flavonoids. Pinus ponderosa, Quercus rubra and Pseudotsuga menziesii were field-grown under modulated ambient (1x) and enhanced (2x) biologically effective UV-B radiation. Foliage was harvested seasonally over a 3-year period, extracted, purified and the flavonoid fraction applied to a mu Bondapak/C(18) column HPLC system sampling at 254 nm. Total flavonoid concentrations in Quercus rubra foliage were more than twice (leaf area basis) that of the other species; Pseudotsuga menziesii foliage had intermediate levels and P. ponderosa had the lowest concentrations of total flavonoids. No statistically significant UV-B radiation-induced effects were found in total foliar flavonoid concentrations for any species; however, concentrations of specific compounds within each species exhibited significant treatment effects. Higher (but statistically insignificant) levels of flavonoids were induced by UV-B irradiation in 1- and 2-year-old P. ponderosa foliage. Total flavonoid concentrations in 2-year-old needles increased by 50% (1x ambient UV-B radiation) or 70% (2x ambient UV-B radiation) from that of 1-year-old tissue. Foliar flavonoids of Q. rubra under enhanced UV-B radiation tended to shift from early-eluting compounds to less polar flavonoids eluting later. There were no clear patterns of UV-B radiation effects on 1-year-old P. menziesii foliage. However, 2-year-old tissue had slightly higher foliar flavonoids under the 2x UV-B radiation treatment compared to ambient levels. Results suggest that enhanced UV-B radiation will alter foliar flavonoid composition and concentrations in forest tree species, which could impact tissue protection, and ultimately, competition, herbivory or litter decomposition.
authors.affiliation: Department of Natural Resource Sciences, Washington State University, Pullman, WA 99164-6410, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Warren
authors.forename: John H
authors.initials: JH
authors.lastname: Bassman
authors.forename: D Scott
authors.initials: DS
authors.lastname: Mattinson
authors.forename: John K
authors.initials: JK
authors.lastname: Fellman
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Edwards
authors.forename: Ronald
authors.initials: R
authors.lastname: Robberecht
mesh_terms: D005415:Flavins / Q000378:metabolism*; D028223:Pinus / Q000378:metabolism / Q000528:radiation effects*; D041604:Pinus ponderosa; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D028224:Pseudotsuga / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D005415:Flavins