The terricolous species Cladonia foliacea (Cladoniaceae,
lichenised Ascomycota) widely distributed in open, dry lowland steppe and rocky mountain
grassland vegetation in Europe was chosen as a potential test organism for ecological
experiments, since their thalli are producing cortical solar radiation-protective
and UV screening pigment dibenzofuran usnic acid and medullary secondary substance
depsidone fumarprotocetraric acid. Significant seasonal differences were found in
the amounts of lichen secondary metabolites analysed by HPTLC and HPLC-PDA between
summer and winter collected thalli in sandy grassland area in Hungary. The concentrations
of usnic acid varied between 7.34 and 15.52 mg/g in summer collected samples and 13.90
and 21.61 mg/g in winter collected ones. A comparable amount (11.61±0.29 mg/g) was
measured in pulverised samples. The concentrations of fumarprotocetraric acid varied
between 0.60 and 3.01 mg/g in summer collected samples and 2.26 and 5.81 mg/g in winter
collected thalli. A comparable amount (2.45±0.21 mg/g) was found in pulverised samples.
The range of concentration values is comparable with data known from lichens. A higher
amount of usnic acid is produced in winter probably to ensure sufficient protection
also for summer. The fumarprotocetraric acid content of the medulla might contribute
to the solar irradiation reflecting role of the pale lower surface lobes turning upwards
in dry condition.
