Jump to main content
Jump to site search

Issue 9, 2002
Previous Article Next Article

Effects of ultraviolet radiation and PAR on the content of usnic and divaricatic acids in two arctic-alpine lichens

Author affiliations

Abstract

The fruticose lichen Flavocetraria nivalis and the crustose lichen Ophioparma ventosa, both common in light-exposed arctic-alpine environments, were exposed to ultraviolet radiation (UVR) in growth chambers for 30 days. Treatment with visible light (PAR) served as control. Both species accumulate the UV-absorbing phenolic compound usnic acid in the upper cortex. The latter species also synthesises several UV-absorbing medullary compounds, among them divaricatic acid. The effects of treatment with UVR on the synthesis of these two compounds were investigated by analysing the compounds quantitatively by RP-HPLC. UV-exposed thallus tips of F. nivalis contained higher concentrations of usnic acid than those not grown under UVR. Both treatments had a positive effect on the synthesis of usnic acid in O. ventosa. An additional experiment with O. ventosa was performed by first storing samples in a low-light habitat for 1 year to obtain near-zero levels of phenolics, and thereby exposing the samples to UVR and PAR for 90 days. A rapid resynthesis of usnic acid was observed for both treatments. The amounts of divaricatic acid were highly variable in all groups, and were not correlated with usnic acid concentrations or treatments. A comparison of O. ventosa from three different habitat types showed that the highest usnic acid amounts were found in the habitat with the highest levels of solar radiation. Results indicate that the induction of usnic acid production by UVR depends on the species studied, and on how well acclimatised the lichen samples are to solar radiation before they are exposed to supplementary UVR. In lichens with an already well-developed internal screening capacity, like the population of F. nivalis, enhanced UVR need not induce further accumulation of usnic acid, but removal of UVR may induce a biodegradation of usnic acid. Results also indicate that PAR is just as important as UVR for triggering the resynthesis of usnic acid in shade-adapted lichens. Divaricatic acid seems to be of low importance for the UV-screening properties of O. ventosa.

Graphical abstract: Effects of ultraviolet radiation and PAR on the content of usnic and divaricatic acids in two arctic-alpine lichens

Back to tab navigation

Publication details

The article was received on 05 Apr 2002, accepted on 31 May 2002 and first published on 25 Jun 2002


Article type: Paper
DOI: 10.1039/B203399B
Citation: Photochem. Photobiol. Sci., 2002,1, 678-685
  •   Request permissions

    Effects of ultraviolet radiation and PAR on the content of usnic and divaricatic acids in two arctic-alpine lichens

    J. W. Bjerke, K. Lerfall and A. Elvebakk, Photochem. Photobiol. Sci., 2002, 1, 678
    DOI: 10.1039/B203399B

Search articles by author

Spotlight

Advertisements