Effect of high light on the efficiency of photochemical energy conversion in a variety of lichen species with green and blue-green phycobionts |
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Authors: | Barbara Demmig-Adams Cristina Máguas William W. Adams III Angelika Meyer Ellen Kilian Otto L. Lange |
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Affiliation: | (1) Lehrstuhl für Botanik II, Universität Würzburg, Mittlerer Dallenbergweg 64, D-8700 Würzburg, Germany;(2) Departamento de Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, 1700 Lisboa, Portugal;(3) Present address: Department of Environmental, Population, and Organismic Biology, University of Colorado, 80 309-0334 Boulder, CO, USA |
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Abstract: | Exposure to high light induced a quantitatively similar decrease in the rate of photosynthesis at limiting photon flux density (PFD) and of photosystem II (PSII) photochemical efficiency, FV/FM, in both green and blue-green algal lichens which were fully hydrated. Such depressions in the efficiency of photochemical energy conversion were generally reversible in green algal lichens but rather sustained in blue-green algal lichens. This greater susceptibility of blue-green algal lichens to sustained photoinhibition was not related to differences in the capacity to utilize light in photosynthesis, since the light-and CO2-saturated rates of photosynthetic O2 evolution were similar in the two groups. These reductions of PSII photochemical efficiency were, however, largely prevented in lichen thalli which were fully desiccated prior to exposure to high PFD. Thalli of green algal lichens which were allowed to desiccate during the exposure to high light exhibited similar recovery kinetics to those which were kept fully hydrated, whereas bluegreen algal lichens which became desiccated during a similar exposure exhibited greatly accelerated recovery compared to those which were kept fully hydrated. Thus, green algal lichens were able to recover from exposure to excessive PFDs when thalli were in either the hydrated or desiccated state during such an exposure, whereas in blue-green algal lichens the decrease in photochemical efficiency was reversible in thalli illuminated in the desiccated state but rather sustained subsequent to illumination of thalli in the hydrated state.Abbreviations and Symbols Fo yield of instantaneous fluorescence - FM maximum yield of fluorescence induced by pulses of saturating light - FV variable yield of fluorescence - PFD photon flux density (400–700 nm) - PSII photosystem IIThis work was supported by the Deutsche Forschungsgeneinschaft (Forscherguppe Ökophysiologic and Sonderforschungsbereich 251 of the University of Würzburg) and the Fonds der Chemischen Industrie. W.W.A. gratefully acknowledges the support of a fellowship from the Alexander von Humboldt Foundation. We thank Professor T.G.A. Green for identifying and supplying all of the New Zealand lichen material and Professor F.-C. Czygan for advice concerning the chlorophyll analyses which were performed by Johanna Leisner. |
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Keywords: | Chlorophyll fluorescence Chlorophyta Cyanobacteria Desiccation Lichens Light stress Photoinhibition in phycobionts Phycobiont |
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