| Summary: | Lichens can survive and cope with unsufficient water supply resulting in low intrathalline relative water content. Under such conditions, photosynthesis is negatively affected by different degree of dehydration. In our study, fully hydrated samples of Xanthoria elegans, Umbilicaria decussata and Usnea aurantiaco-atra were light-acclimated and during following desiccation from a fully hydrated to dry state, steady-state chlorophyll fluorescence (FS), effective quantum yield of photochemical processes in PSII (ФPSII), and nonphotochemical quenching (qN) were measured in response to decreasing relative water content (RWC). The three experimental lichen species showed a high desiccation tolerance. The desiccation-induced decrease in ФPSII was found in X. elegans, U. decussata and U. aurantiaco-atra, at the RWC values below 30%. This is well comparable to the evidence reached in other Arctic / Antarctic lichen species. Interspecific differences in desiccation tolerance of these selected Antarctic lichens, based on the analysis of photosystem II effectivity and quenching mechanisms, were described and discussed.
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