Calcium Toxicity and Tolerance in Lichens: Ca Uptake and Physiological Responses

Abstract

Although differential sensitivity of lichens to calcium excess has been documented previously at the community level, ecophysiological studies, which would shed light on the calcifuge or calcicole nature of lichens, are virtually absent. In the present study, we compared physiological responses of two morphologically similar foliose lichens, Dermatocarpon miniatum (calcicole lichen) and Umbilicaria hirsuta (calcifuge lichen) to Ca excess (up to 100 mM). The degree of total Ca uptake by the lichens after 24-h prolonged exposure was compared with selected physiological markers including levels of assimilation pigments, chlorophyll a fluorescence, soluble proteins, ergosterol, TBARS, and hydrogen peroxide. Both tested lichens accumulated Ca from the applied solutes of CaCl2 by a dose-dependent manner, although excess of Ca did not change content of assimilation pigments in both tested lichens, as well as integrity of lichen symbiont membranes (tested as TBARS, K content, and ergosterol content) when compared to respective controls. However, we observed significant, concentration-dependent decrease of chlorophyll a fluorescence, content of soluble proteins, and hydrogen peroxide production in U. hirsuta, while in D. miniatum were all these parameters stable through all tested Ca concentrations.