Element uptake in thalli of the lichen Physcia caesia from sandstone and calcareous substratum

Physcia caesia is a foliose, saxicolous lichen commonly found on weakly acidic to alkaline rock and artificial calcareous substrata. Uptake of iron and phosphate, which are known to be significant for governing the calcifuge-calcicole behavior of lichens (as well as vascular plants), was studied in individuals of P caesia deriving either from variegated sandstone or concrete. Samples from either substratum originated from walls erected at the same location, i.e., lichens were exposed to the same atmospheric element load and microclimate prior to the experiments. Element uptake was investigated after short-term incubation in the laboratory involving solutions of FeCl 2 , FeCl 3 , and KH 2 PO 4 at pH 3 and 8. Uptake of Fe 2 + was significantly higher at either pH in the thalli from concrete than in those from sandstone, whereas Fe 3 + uptake was not significantly different between the two groups of lichen thalli, though there was an insignificant trend for higher Fe 3 + uptake at pH 8 in the samples from concrete. Phosphate uptake also was more efficient in thalli deriving from concrete than in those from sandstone, even though the initial P content was higher in the samples from sandstone. The results suggest that the ability of P caesia to adapt Fe and P uptake to the pH-dependent availabilities of these nutrients is responsible for the potential of the species to grow both on weakly acidic and alkaline substrata.