Lichen substances prevent lichens from nutrient deficiency.
The dibenzofuran usnic acid, a widespread cortical secondary metabolite produced by lichen-forming fungi, was shown to promote the intracellular uptake of Cu(2+) in two epiphytic lichens, Evernia mesomorpha and Ramalina menziesii, from acidic, nutrient-poor bark. Higher Cu(2+) uptake in the former, which produces the depside divaricatic acid in addition to usnic acid, suggests that this depside promotes Cu(2+) uptake. Since Cu(2+) is one of the rarest micronutrients, promotion of Cu(2+) uptake by lichen substances may be crucial for the studied lichens to survive in their nutrient-poor habitats. In contrast, study of the uptake of other metals in E. mesomorpha revealed that the intracellular uptake of Mn(2+), which regularly exceeds potentially toxic concentrations in leachates of acidic tree bark, was partially inhibited by the lichen substances produced by this species. Inhibition of Mn(2+) uptake by lichen substances previously has been demonstrated in lichens. The uptake of Fe(2+), Fe(3+), Mg(2+), and Zn(2+), which fail to reach toxic concentrations in acidic bark at unpolluted sites, although they are more common than Cu(2+), was not affected by lichen substances of E. mesomorpha.
Hauck
Markus
M
Department of Plant Ecology, Albrecht von Haller Institute of Plant Sciences, University of Göttingen, Germany. mhauck@gwdg.de
Willenbruch
Karen
K
Leuschner
Christoph
C
D001572:Benzofurans / Q000378:metabolism*; D001692:Biological Transport; D003300:Copper / Q000378:metabolism*; D053630:Depsides / Q000378:metabolism*; D008011:Lichens / Q000737:chemistry / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*
D001572:Benzofurans; D053630:Depsides; C073339:usnic acid; D008345:Manganese; D003300:Copper