Acetone rinsing - A method for testing ecological and physiological roles of secondary compounds in living lichens

Acetone can extract secondary compounds from many air-dry lichens without a ffecting their viability. More polar solvents were highly detrimental to ph otosystem II (PSII), whereas less polar solvents failed to extract the comp ounds. Acetone tolerance, assessed by chlorophyll fluorescence after a 48 h rs recovery subsequent to the acetone submersion, varied between the 12 stu died species. Peltigera aphthosa suffered already after 30 minutes, whereas the vitality of Lasallia pustulata did not start to decline until after 25 0 hrs submersion. Lichens with Coccomyxa, Dictyochloropsis and Nostoc photo bionts were more acetone-susceptible than the five tested Trebouxia lichens . Whereas secondary compounds could be completely extracted within <1 hr in Xanthoria parietina, a 200 hrs extraction was needed for L. pustulata and Xanthoparmelia conspersa. Secondary compounds of P. aphthosa, Nephroma arct icum and Lobaria pulmonaria could not be extracted before the viability was severely affected. Accordingly, Trebouxia lichens appeared to be most suit ed for testing ecological and physiological roles of secondary compounds.