Membrane permeability response of lichen Bryoria fuscescens to wet deposited heavy metals and acid rain

Lichen Bryoria fuscescens were treated in the field experiment with heavy m etal solutions, containing a mixture of Cu2+ and Ni2+ ions alone or in comb ination with acidity (H2SO4, pH 3), to study the effects of simulated acid rain and heavy metal deposition on the membrane integrity of lichen. Membra ne responses to pollutant treatments were assessed by measurements of the l eachate conductivity, the K+ leakage, and the ergosterol concentration. Bot h Cu and Ni concentrations of lichen were significantly increased by metal treatments. In addition a significant reduction of Ni with acid solution wa s found. The conductivity of leachate was significantly increased by the ac idity but not affected by the metal treatments alone. Increased thallus met al concentrations (> 400 mu g g(-1) Cu, > 100 mu g g(-1) Ni) significantly increased K+ leakage and reduced ergosterol concentration. The results sugg est that the differences in the membrane responses are associated with the different sensitivity of algal and fungal partners to the acidity of heavy metal solutions. (C) 1999 Elsevier Science Ltd. All rights reserved.