It has often been suggested that ectomycorrhizas ameliorate metal toxi
city in forest trees. This paper will present a review of investigatio
ns carried out to assess amelioration of metal toxicity by ectomycorrh
izas. These investigations have used a number of metals and a range of
ectomycorrhizas. In a small number of cases amelioration of metal tox
icity could be shown for specific metals by some fungi. In recent inve
stigations on the ability of two species of ectomycorrhizas to improve
Cd tolerance in Picea abies, a clear amelioration of Cd toxicity coul
d be shown with Paxillus involutus. This improvement could not be rela
ted to decreased Cd uptake. However, in general, evidence suggests tha
t ectomycorrhizas do not universally ameliorate metal toxicity. Amelio
ration is dependent upon the species and strain of the ectomycorrhiza
and the metal being considered. (C) 1998 Elsevier Science Ltd.