Changes in the photosynthetic activity and content of chlorophylls and carotenoids in the Peltigera canina and Peltigera aphthosa lichens under the action of elevated temperature

Lichens are ancient symbiotic organisms that can survive in extreme conditions through unique resistance mechanisms. Lichens are associations between a fungus (mycobiont) and algae and/or cyanobacteria (photobionts). The photobiont composition of lichen can determine the specificity of the stress response to abiotic factors, including unfavorable temperatures. This work analysed stress-induced changes in the photosynthetic activity and content of chlorophylls and carotenoids on the closely related Peltigera canina and Peltigera aphthosa lichens, which differ by photobiontic composition, under elevated temperature. Stress treatment resulted in a decrease in the photochemical activity of photosystem II (PSII) in both lichens. By the analysis of stress-induced changes in the content of photosynthetic pigments in lichens, the exposure to elevated temperature of the P. canina lichen induced astaxanthin accumulation but P. aphthosa significantly decreased in the content of chlorophyll a and xanthophylls synthesized from β-carotene. Thus, the identified significant differences in the composition of chlorophylls and carotenoids in the studied lichens suggest the involvement of various mechanisms of stress response to the action of elevated temperature due to the specificity of their photobiontic composition.