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Abstract
Recent hypotheses suppose that dry lichens emit a faint chlorophyll a fluorescence because of a “long-wavelength quencher” embedded in the antenna complex that protects photosystem II (PSII) from photodamage. To verify in the field the PSII re-activation promptness induced by water availability, chlorophyll a fluorescence was measured on the epiphytic lichen Flavoparmelia soredians after two months without rainfall events in a Mediterranean cork oak wood (Bosco Santo Pietro, Sicily, Italy). Measurements were carried out at dawn and sunset on north- and south-exposed populations under different regimes of hydration and dark-adaptation. The results show that prolonged hydration increases the photochemical conveying of energy to PSII and decreases the non-photochemical energy dissipation that otherwise might occur in the antenna complex of the lichen photobionts. A slight decrease in PSII efficiency caused by photoinhibition was observed in thalli exposed to ambient light (up to 600 μmol photons m−2 s–1) only when kept fully hydrated. The results are discussed on the basis of our knowledge on the ecology of the species, that is a representative component of Mediterranean epiphytic lichen communities.
Acknowledgements
This work was possible thanks to the generous help of several fellow members of the Italian Lichen Society. We are in debt to Domenico and Mariella Puntillo (Cosenza, I) for lending us their camper, Maria Grillo (Catania, I) and Giovanna Caniglia (Carlentini, I) for their warm hospitality and help in selecting the study area, and Stefano Bertuzzi (Trieste, I), Massimo Bidussi (Ås, NO) and an anonymous referee for critical remarks to the manuscript. The study was funded by D.T.N. (f.o.o.p.) funds from M.T.