Xanthona parietina thalli were collected from a ‘clean-air’ location and from a polluted area. Ramalina duriaei thalli were collected from the same ‘clean-air’ location and some thalli were transplanted to air polluted locations, where R. duriaei no longer occurs. The effects of air contaminants on these two lichens were compared under controlled laboratory conditions and in field experiments. Air contaminants and exposure to bisulphite ions had little or no damaging effect on X. parietina, whereas severe damage was caused to R. duriaei, as judged by chlorophyll degradation, autofluorescence of photobionts, photosynthetic activity, membrane integrity and ATP content. The different responses presented confirm the sensitivity of R. duriaei and resistance of X. parietina to air pollution.

Lipids and fatty acids from the lichen Rhizoplaca peltata, growing either high in the mountains or in nearby foothills, were analysed and compared. It was shown that the same lichen species had considerable differences in the content of triacylglycerols, free sterols, wax esters, steryl esters, glycolipids, betaine and phospholipids, as well as in fatty acid content, depending on altitude.

Surveys of the distribution of the lichens Xanthoria panetina and Ramalina duriaei in Israel showed that environments with air pollution had no damaging effectson X. panetina, whereas R. duriaei had disappeared from polluted environments: physiological studies supported this relative sensitivity. Investigations of possible defence mechanisms protecting X. parietina from the damaging effects of air pollution showed a multitude of possible protective systems. These included constitutive avoidance such as: efficient buffering capacity; a relatively high potassium content; and antioxidation by parietin, and induced tolerance such as: SO2 oxidation to non-toxic sulphate; increased glutathione content; induced praline and arginine synthesis; and increased detoxification of active oxygen forms.

Early stages of lichen colonization on glass are reported for the first time from Antarctica. In the initial establishment of the lichen thallus rhizomorphs play an importantrole for the attachment to the substratum and the exploitation of nutrient and photobiont resources. The micrographs presented indicate that in Antarctica colonization of bare substrata bylichens is not necessarily an extremely slow process. Furthermore, our findings demonstrate that the use of artificial substrata such as glass could provide a simple method for studies in lichencolonization and development in extreme environments.