Accumulation of trace elements in the peripheral and central parts of a foliose lichen thallus

Total concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, and Zn were compared in the peripheral (younger) and central (older) part of the thallus of the epiphytic lichen Parmelia caperata from a background area of central Italy. The results showed that the trace element content was highly variable. Concentrations were similar for several elements (As, Cr, Fe, Hg, Mn, Ni, Sb). Elements of limited metabolic significance (Al, Cd, Pb) had higher concentrations in the central parts, suggesting that they are trapped in the medulla, while elements essential for lichen metabolism (Co, Cu, Mo, Zn) had higher concentrations in the peripheral parts, suggesting that they are easily displaced from one part of the thallus to another.