Low-temperature limitation of primary photosynthetic processes in Antarctic lichens Umbilicaria antarctica and Xanthoria elegans
| Authors | |
|---|---|
| Year of publication | 2007 |
| Type | Article in Periodical |
| Magazine / Source | Polar Biology |
| MU Faculty or unit | |
| 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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