First data on isotope and trace element compositions of a Xerocomus subtomentosus mushroom sample from western Czech Republic.

A study of a sample of Xerocomus subtomentosus revealed that the fruiting body behaved as an accumulating biosystem with respect to Rb (BF = 36), K and Ag (BF = 5.0 for both), and, to a lesser extent, Mg, Cu, Zn, and Se (BF = 1.7-3.1). A Xerocomus mushroom has not shown to be a good accumulator of toxic As (BF = 0.64), Cd (BF = 0.65), and Pb and Cr (BF < 0.1 for both) from the soil. Within-mushroom distribution of the trace elements showed very high mobility of Ag (TF = 54) and As (TF = 16); moderate mobility of K, Ti, Pb, and Rb (TF = 2.1-3.1); and low mobility to immobility of other elements. A mushroom preferentially intakes isotopically heavy Mg (Δ26Mgstipe-soil = 0.22‰) and Zn (Δ66Znstipe-soil = 0.68‰), and isotopically light Cu (Δ65Custipe-soil =  - 1.04‰). The fruiting body has shown insignificant but measurable within-mushroom isotope fractionation with the higher parts of the fruiting body accumulating isotopically lighter Cu (Δ65Cucap-stipe =  - 0.06‰), Zn (Δ66Zncap-stipe =  - 0.18‰), and Mg (Δ26Mgcap-stipe =  - 0.31‰). Such a behavior is overall similar to that displayed by the higher plants.