Effects of ozone fumigation on epiphytic macrolichens: ultrastructure, CO2 gas exchange and chlorophyll fluorescence

The lichen species Anaptychia ciliaris, Collema nigrescens, Evernia prunastri, Hypogymnia bitteri, Lobaria pulmonaria, Pseudevernia furfuracea and Usnea rigida s.l. were fumigated with site-relevant concentrations (for Central Europe) of ozone over 80 days (180 microg m(-3) during daytime, 80 microg m(-3) during the night). Chlorophyll fluorescence measurements revealed a significant reduction of Fv/Fm after ozone fumigation in five of the species investigated, indicating severe stress on photosystem II due to ozone. The physiological impairment paralleled our fine structural investigations, revealing a significantly higher percentage of collapsed photobiont cells. This indicates that the effects of ambient ozone concentrations under experimental conditions included biophysical and physiological, as well as structural impairment in the lichens studied.