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Photosynthetic performance of Antarctic lichen Dermatocarpon polyphyllizum as affected by desiccation and low temperature.

Autoři: Bednaříková M., Váczi P., Lazár D., Barták M.Publikováno : Photosynthesis Research 145(2), 159-177Rok: 2020

Lichens are symbiotic organisms well adapted to desiccation/rehydration cycles. In the last decades, the physiological background of their photosynthetic response, specifically activation of the protective mechanism during desiccation has been studied at the level of photosystem II of lichen photobiont by several biophysical methods. In our study, the effects of desiccation and low temperature on chlorophyll fluorescence and spectral reflectance parameters were investigated in Antarctic chlorolichen Dermatocarpon polyphyllizum. Lichen thalli were collected in the James Ross Island, Antarctica. After transfer to a laboratory, samples were fully hydrated and exposed to desiccation at the temperature of 18, 10 and 4 °C. During the desiccation, relative water content (RWC) was measured gravimetrically and photosynthetic parameters related to the fast transient of chlorophyll fluorescence (OJIP) were measured repeatedly. Similarly, the change in spectral reflectance parameters (NDVI, PRI, G, NPCI) was monitored during thallus dehydration. Dehydration-response curves showed a decrease in majority of the OJIP-derived parameters (e.g. absorption: ABS/RC, maximum quantum yield of photosystem II photochemistry: FV/FM, and performance index: PI) in D. polyphyllizum, more apparently at the RWCs below 20%. Activation of protective mechanisms in severely dehydrated thalli was documented by increased thermal dissipation (DI0/RC) and its quantum yield (Phi_D0). Low temperature accelerated these processes. Analysis of the OJIP shape revealed the presence of K-band (300 ms), and L-band (80 ms) attributed to dehydration-induced stress. Changes in spectral reflectance indices in response to the RWC decrease and temperature indicated those responding sensitively to the two factors, i.e. NDVI and NPCI. The indices might be used in follow-up ecophysiological photosynthetic studies of lichens undergoing rehydration/dehydration cycles.

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