Low-temperature limitation of primary photosynthetic processes in Antarctic lichens Umbilicaria antarctica and Xanthoria elegans

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Authors

BARTÁK Miloš VÁCZI Peter HÁJEK Josef SMYKLA Jerzy

Year of publication 2007
Type Article in Periodical
Magazine / Source Polar Biology
MU Faculty or unit

Faculty of Science

Citation
Web Polar Biology (Springer) home page
Field Botany
Keywords Chlorophyll fluorescence imaging; Extreme temperature; Freezing; Non-photochemical quenching
Description Temperature response curves of chlorophyll a fluorescence parameters were used to assess minimum subzero temperature assuring functioning of photosynthetic photochemical processes in photosystem II (PS II) of Antarctic lichens. Umbilicaria Antarctica and Xanthoria elegans were measured within the temperature range from minus20 to plus10 degC by a fluorometric imaging system. For potential (F V/F M) and actual (Phi II) quantum yields of photochemical processes the minimum temperature was found to be between minus10 and minus20 degC. Nonphotochemical quenching (NPQ) of absorbed excitation energy increased with temperature drop reaching maximum NPQ at minus15 degC. Image analysis revealed intrathalline heterogeneity of chlorophyll a fluorescence parameters with temperature drop. Temperature response of Phi II exhibited an S curve with pronounced intrathalline differences in X. elegans. The same relation was linear with only limited intrathalline difference in U. antarctica. The results showed that Antarctic lichen species were well adapted to subzero temperatures and capable of performing primary photosynthesis at minus15 degC.
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