Ultraviolet-B radiation alters phenolic salicylate and flavonoid composition of Populus trichocarpa leaves

Abstract

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.

Functional Characterization of CsBGlu12, a β-Glucosidase from Crocus sativus, Provides Insights into Its Role in Abiotic Stress through Accumulation of Antioxidant Flavonols

“…Thus, our results suggest that the stress tolerance of CsBGlu12 overexpression lines may be due to the accumulation of flavonols (kaempferol and quercetin), which are known to play key roles in abiotic stress (48). There are many instances where kaempferol and quercetin levels were shown to increase in response to UV-B irradiation (49). It has also been reported that a brief exposure of plants to UV-B provides a regulatory signal, eliciting the accumulation of flavonols to confer protection to UV-induced damage due to their absorption in this region (50,51).…”

The Wound-, Pathogen-, and Ultraviolet B-ResponsiveMYB134Gene Encodes an R2R3 MYB Transcription Factor That Regulates Proanthocyanidin Synthesis in Poplar

“…The activation of flavonol biosynthetic genes exhibited a reduction at 12 h, which may have been caused by the absence of the stimulus during the night or by circadian regulation. Flavonol glycosides are known to be important UV-B protective compounds (Li et al, 1993;Landry et al, 1995), and increased flavonol accumulation in leaves has been observed in poplar and other trees under elevated UV-B light (Warren et al, 2002(Warren et al, , 2003Keski-Saari et al, 2005;Turtola et al, 2005). HPLC analysis of extracts from leaves after 7 d of HL exposure revealed a large increase in total flavonol glycosides ( Fig.…”

Elevational Trends in Usnic Acid Concentration of Lichen Parmelia flexilis in Relation to Temperature and Precipitation

“…Research to examine the species response to climate change would draw complementary data sets from observations and functional analyses, i.e., changed species interaction and chemical compositions. Global climate change conditions often alter plant chemical composition, which in turn can affect food and fodder quality and decomposition rates [2]. These alterations in the chemical composition of plants grown under the current climate can provide significant information concerning the impact of climate change on synthesis of secondary metabolites.…”