This Article Full Text Full Text (PDF) All Versions of this Article: 145/3/997    most recent pp.107.106872v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Physiol. Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Veerman, J. Articles by Bruce, D. Search for Related Content PubMed PubMed Citation Articles by Veerman, J. Articles by Bruce, D. Agricola Articles by Veerman, J. Articles by Bruce, D.

BIOENERGETICS AND PHOTOSYNTHESIS

Photoprotection in the Lichen Parmelia sulcata: The Origins of Desiccation-Induced Fluorescence Quenching¹

Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada L2S 3A1

Lichens, a symbiotic relationship between a fungus (mycobiont) and a photosynthetic green algae or cyanobacteria (photobiont), belong to an elite group of survivalist organisms termed resurrection species. When lichens are desiccated, they are photosynthetically inactive, but upon rehydration they can perform photosynthesis within seconds. Desiccation is correlated with both a loss of variable chlorophyll a fluorescence and a decrease in overall fluorescence yield. The fluorescence quenching likely reflects photoprotection mechanisms that may be based on desiccation-induced changes in lichen structure that limit light exposure to the photobiont (sunshade effect) and/or active quenching of excitation energy absorbed by the photosynthetic apparatus. To separate and quantify these possible mechanisms, we have investigated the origins of fluorescence quenching in desiccated lichens with steady-state, low temperature, and time-resolved chlorophyll fluorescence spectroscopy. We found the most dramatic target of quenching to be photosystem II (PSII), which produces negligible levels of fluorescence in desiccated lichens. We show that fluorescence decay in desiccated lichens was dominated by a short lifetime, long-wavelength component energetically coupled to PSII. Remaining fluorescence was primarily from PSI and although diminished in amplitude, PSI decay kinetics were unaffected by desiccation. The long-wavelength-quenching species was responsible for most (about 80%) of the fluorescence quenching observed in desiccated lichens; the rest of the quenching was attributed to the sunshade effect induced by structural changes in the lichen thallus.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Doug Bruce (dbruce{at}brocku.ca).

www.plantphysiol.org/cgi/doi/10.1104/pp.107.106872

^* Corresponding author; e-mail dbruce{at}brocku.ca.

Received August 3, 2007; accepted August 30, 2007; published September 7, 2007.

Related articles in Plant Physiol.:

On the Inside

Peter V. Minorsky
Plant Physiol. 2007 145: 573-574. [Full Text]