Temperature effects on photosynthetic performance of Antarctic lichen Dermatocarpon polyphyllizum : a chlorophyll fluorescence study

TLDR: The OJIP-derived parameters, DI0/RC and Phi_D0 (quantum yield of energy dissipation) in particular, indicated that they might be used for the detection of early events in low temperature-affected lichens.

Abstract: Chlorophyll fluorescence is an important indicator of a photosynthetic energy conversion in chloroplast photosystem II and responds sensitively to stress factors affecting photosynthesizing organisms. Three different methods were employed to identify the most sensitive fluorescence parameters responding to thallus temperature decrease within Antarctic lichen Dermatocarpon polyphyllizum: (1) Fast chlorophyll fluorescence transient (OJIP with parameters characterizing photosystem II functioning) (2) Slow Kautsky kinetics supplemented by saturation pulses (to evaluate quantum yield of photosynthetic processes in photosystem II, as well as maximum quantum PSII efficiency and non-photochemical and photochemical quenching), and (3) Linear cooling from + 22 to − 40 °C (to determine change in ΦPSII and the critical temperature for PSII). A K-step (usually documented at highly stressed organisms) was found in OJIPs measured at + 22 °C at 0.22–0.40 ms and attributed to the negative effect of high temperature on PSII functioning, PSII donor side limitation in particular. At subzero temperature (− 0.5, − 5 °C), an L-step was detected at 0.05 ms and related to a low temperature-induced decrease in connectivity between light-harvesting complexes and PSII. An increase of DI0/RC (the flux of dissipated excitation energy) was reported for the first time in lichens. The OJIP-derived parameters, DI0/RC and Phi_D0 (quantum yield of energy dissipation) in particular, indicated that they might be used for the detection of early events in low temperature-affected lichens. Linear cooling data determined the critical temperature (− 12 °C) for primary photosynthetic processes (ΦPSII) in Dermatocarpon.