ECTOMYCORRHIZAS AND AMELIORATION OF METAL STRESS IN FOREST TREES

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.