Vitality of the cyanolichen Peltigera praetextata exposed around a cement plant (SW Slovakia): a comparison with green algal lichens

The suitability of the cyanolichen Peltigera praetextata (Sommerf.) Zopf as indicator of the effects of air pollution around a cement industry was investigated. For this purpose, lichen samples taken from an unpolluted site were exposed for 1–6 months at selected sites (a cement mill, two quarries, inhabited and agricultural sites) in SW Slovakia: physiological parameters and ultrastructural features were examined prior and after exposure. The responses of P. praetextata were then compared with those of the green-algal lichens Evernia prunastri and Xanthoria parietina co-located at the same sites. The performance of the cyanobacterial photobiont of P. praetextata (as reflected by the maximum quantum yield of primary photochemistry FV/FM and by the performance index PIABS) was negatively influenced mainly by the length of exposure in the urban and agricultural sites and less by dust pollution around the cement mill and the quarries. A significant increase in membrane lipid peroxidation products reflected the effects of oxidative stresses in all sites. The alteration of the content of water soluble proteins was detected in the samples exposed around the cement mill, while dehydrogenase activity did not show any significant pattern. Similarly to green algal lichens, ultrastructural alterations featured lipid droplets increase, swelling of cellular components, thylakoid degeneration and sometimes plasmolysis, which on the whole gave the cells an aged appearance, especially in the urban and agricultural sites. On the whole, E. prunastri confirmed to be the most sensitive to dust pollution, P. praetextata was likely influenced by microclimatic conditions and habitat eutrophication and X. parietina was the most resistant. When compared with green-algal lichens, P. praetextata was not the best indicator of the effects of cement dust pollution.