Journal
TREE PHYSIOLOGY
Volume 23, Issue 8, Pages 527-535Publisher
OXFORD UNIV PRESS
DOI: 10.1093/treephys/23.8.527
Keywords
black cottonwood; phenolic glycosides; plant-insect interactions; salicin
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We investigated foliar phenolic composition of field- and greenhouse-grown Populus trichocarpa Torr. & A. Gray (black cottonwood) ramets subjected to near zero (Ox), 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 Ox-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.
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