THE INFLUENCE OF SHEATHING (ECTO-) MYCORRHIZAS OF TREES ON THE UPTAKE AND TOXICITY OF METALS

Heavy metal tolerance has been widely reported in herbaceous plants and trees growing on spoil heaps of old metal mines; recently it has been found that tolerance may vary with mycorrhizal status. Experiments in controlled conditions with seedlings of birch, pine and spruce have usually shown that mycorrhizal associations with species of Amanita, Paxillus, Pisolithus, Rhizopogon, Scleroderma and Suillus decrease the toxicity of zinc, copper, nickel and aluminium. Except with very low-level treatments the presence of mycorrhizas decreases metal accumulation in shoots. Concentrations in roots are little altered, but large amounts of metal may be found in extramatrical hyphae.