Drought-induced ultra-fast Fluorescence quenching in Photosystem II in lichens studied by femto-picosecond time-resolved fluorescence spectrophotometry at cryogenic temperature

Abstract

Lichens are photoautotrophic symbionts of fungi and algae and survive even under the drought environments. It has been suggested that dried lichens immediately convert excess light energy into heat to prevent the photoinhibition in photosystem II (PSII). A recent report suggests that the chlorophyll emitting fluorescence at 740 nm (Chl740) is present and acts as an energy quencher in PSII in lichen [1]. We used the same type of lichens and measured ultrafast fluorescence decay in dry lichen cells by the combination of upconversion and streakcamera system at 4-300 K to study whether and where Chl740 is present in PSII.
The fluorescence of Chl740 rising within 1 ps after laser excitation, decaying in several picoseconds was observed. The rate of EET and quenching process in PSII was estimated.
We also discuss with respect to other two different types of lichens.
[1] Veerman et al, Plant Physiol., 145, 997-1005 (2007)