The uptake of cadmium and zinc by mycelia and their accumulation in mycelia and fruiting bodies of edible mushrooms

Cd and Zn concentrations were determined by optical emission spectroscopy in various parts of the fruiting body and the mycelium of two wild mushrooms, Agaricus macrosporus and Agaricus silvicola, and in cultivated Stropharia rugosoannulata. Cd was distributed in a characteristic manner within the fruiting body of all three species. The Cd content of the cap was a function of its radius as well as its height. Concentrations of Cd and the chemically related Zn in the investigated mushroom segments were strongly correlated, whereas Al, Cu and Ag correlated poorly with Cd. To our knowledge, this is the first study of Cd contents in wild mycelia. We found similar concentrations of Cd and Zn in isolated mycelia and stems of the corresponding fruiting bodies. In addition, substrates were analysed to study soil-specific effects on Cd accumulation. The extent of Cd and Zn transfer from soil to mushroom was species-specific and influenced by the availability of these two heavy metals, as well as the age of the mushroom. Interestingly, the typical Cd and Zn distributions described here were not affected by the extent of accumulation, indicating that uptake and distribution of Cd and Zn are actually two separate mechanisms.