Heavy metal binding properties of Pinus sylvestris mycorrhizas from industrial wastes

Abstract

Mycorrhizas of Pinus sylvestris, collected from zinc wastes in Poland and France were investigated using transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with energy dispersion spectroscopy (EDS) and electron energy loss spectroscopy (EELS). At both sites, mycorrhizas of Hebeloma were the most frequent, however, they were often characterised by a sparse or only locally developed fungal mantle. Mycorrhizas formed by suilloid fungi were much less frequent, and usually produced a clearly defined fungal mantle characterised by abundant formation of pigments and crystals covering the hyphae of the outer mantle. These two groups of mycorrhizas differed in their heavy metal binding properties. A biofiltering effect of Pb and Zn by the fungal mantle was observed only in the case of suilloid mycorrhizas, which represented up to 10% of the total number of mycorrhizas. No statistical differences between the mantle, the cortical cell walls and the vascular tissue were demonstrated in mycorrhizas formed by other fungi dominating on industrial wastes. In the case of Hebeloma and Inocybe, however, elements such as Cu and Cd were present in higher amounts in the extra-matrical mycelium, whereas no or only low amounts of these elements were detected within fungal mantles, mainly in mycorrhizas from the French waste. Analysis of the root systems has shown relatively high percentage of nonmycorrhizal short roots, suggesting the inhibition of mycorrhiza formation or a decreased number of mycorrhizal propagules. The role of dead roots and mycorrhizas in biosorption and immobilization of heavy metals was discussed.