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Usnic Acid and Atranorin Concentrations in Lichens in Relation to Bands of UV Irradiance

Michael D. BeGora and Dianne Fahselt
The Bryologist
Vol. 104, No. 1 (Spring, 2001), pp. 134-140
Stable URL: http://www.jstor.org/stable/3244925
Page Count: 7
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Usnic Acid and Atranorin Concentrations in Lichens in Relation to Bands of UV Irradiance
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Abstract

Using spectral filters, Cladonia uncialis and Cladina rangiferina were exposed for seven days to visible light supplemented with two intensities of three different bands of ultraviolet in a growth chamber. The concentrations of lichen secondary products separated by thin-layer chromatography were then determined densitometrically. In Cladonia uncialis, higher intensity exposure to visible light enhanced with UV-A, while UV-B and UV-C were excluded, significantly increased usnic acid concentrations over control levels. However, less usnic acid accumulated under high intensity enhancement of both UV-A and UV-B. The effect of supplemental UV-A and UV-B was the same on atranorin concentrations in Cladina rangiferina. This suggested that UV-A caused increased accumulation of both compounds, but that the effect was negated by UV-B. Concentrations of usnic acid in natural populations of Cladina mitis were significantly lower in spring and summer when UV-B flux is greatest.

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