Ultraviolet-B radiation alters phenolic salicylate and flavonoid composition of Populus trichocarpa leaves.
We investigated foliar phenolic composition of field- and greenhouse-grown Populus trichocarpa Torr. & A. Gray (black cottonwood) ramets subjected to near zero (0x), ambient (1x) or twice ambient (2x) concentrations of biologically effective ultraviolet-B (UV-B) radiation. After a 3-month treatment period, several age classes of foliage samples were harvested and the phenolic compounds extracted, separated by high performance liquid chromatography and identified and quantified by diode-array spectrometry and mass spectrometry. Foliar phenolic concentration was greater in 1x- and 2x-treated tissue than in 0x-treated tissue. Phenolic compounds that increased in response to UV-B radiation were predominantly flavonoids, primarily quercetin and kaempferol glycosides. Enhancement of UV-B radiation from 1x to 2x ambient concentration did not result in further flavonoid accumulation in either greenhouse or field ramets; however, a non-flavonoid phenolic glycoside, salicortin, increased in response to an increase in UV-B radiation from 1x to 2x ambient concentration. Increased salicortin concentrations accounted for at least 30-40% of the total (5%) increase in UV-absorption potential of 2x-treated tissue. Because salicortin and other salicylates are important in plant-herbivore-predator relationships, these increases are discussed in the context of collateral feeding studies. We conclude that enhanced solar UV-B radiation may significantly alter trophic structure in some ecosystems by stimulating specific phenolic compounds.
USDA Forest Service, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331, USA.
Jeffrey M
JM
Warren
John H
JH
Bassman
John K
JK
Fellman
D Scott
DS
Mattinson
Sanford
S
Eigenbrode
D005419:Flavonoids / Q000032:analysis* / Q000096:biosynthesis; D018515:Plant Leaves / Q000737:chemistry / Q000528:radiation effects*; D032107:Populus / Q000737:chemistry / Q000528:radiation effects*; D012459:Salicylates / Q000032:analysis*; D014197:Trees / Q000737:chemistry / Q000528:radiation effects*; D014466:Ultraviolet Rays
D005419:Flavonoids; D012459:Salicylates