Concentrations of Foliar Quercetin in Natural Populations of White Birch (Betula pubescens) Increase with Latitude |
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Authors: | Sari Stark Riitta Julkunen-Tiitto Esa Holappa Kari Mikkola Ari Nikula |
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Affiliation: | (1) Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FIN-96301 Rovaniemi, Finland;(2) Natural Product Research Laboratory, Department of Biology, University of Joensuu, FIN-80101 Joensuu, Finland |
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Abstract: | We investigated latitudinal and regional variations in the composition and concentrations of foliar flavonoids and condensed
tannins in wild populations of white birch (Betula pubescens EHRH) in a large climatic transect in Finland. Concentrations of quercetin derivatives were correlated positively with latitude.
By contrast, the concentrations of apigenin and naringenin derivatives were correlated negatively with latitude. These compound-specific
latitudinal gradients compensated each other, resulting in no changes in the concentration of total flavonoids. Our results
thus demonstrate a qualitative, but not quantitative, latitude-associated gradient in the foliar flavonoids in white birch.
Due to higher antioxidant capacity of the quercetin derivatives in relation to other flavonoids, the qualitative change can
reflect higher adaptation to light in the north than south. An investigation on a regional scale in the northern boreal zone
showed that the temperature sum was correlated positively and soil P concentration was correlated negatively with the concentrations
of foliar flavonoid, while the concentration of condensed tannins was correlated with slope. The variation in concentrations
of flavonoids at large-scale geographical patterns is in line with the conjecture that foliar flavonoids are synthesized for
protection against photooxidative stress. |
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Keywords: | Betula pubescens Condensed tannins Flavonoids Phenolics |
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