Heavy metal content and localization in mycorrhizal Euphorbia cyparissias zinc wastes in southern Poland

Abstract

Arbuscular mycorrhiza (AM) development, heavy metal uptake by the plant and localization of heavy metals within plant and AM fungal structures, has been investigated in Euphorbia cyparissias collected from zinc wastes in Poland and from two other stands differing in soil parameters. The plant was selected on the basis of preliminary research on mycorrhiza of plants colonizing zinc wastes. E. cyparissias was strongly mycorrhizal and arbuscules were abundant except at the very beginning of the vegetation period. Light microscopy after rhodizoniate staining and SEM equiped with an EDS system have been used to localize heavy metals within the fungal mycelium and mycorrhizal roots. About 80% of the total intraradical mycelium show an increased content of heavy metals in comparison to the remaining 20% where heavy metals were under detection limit. At the same time the number of arbuscules formed by mycelium stained by rhodizoniate is slightly lower than in mycelium containing a low level of these elements. Using the rhodizoniate staining lead was found in epidermal cell walls, root hairs, in mycorrhizal mycelium and in crystaloids deposited within latex and inside cortical cells, around fungal hyphae. SEM observations with EDS system confirmed that these crystaloid depositions contained higher concentrations of Zn than root cell wall and fungal structures.