TOLERANCE OF ECTOMYCORRHIZAL FUNGI AND PLANTS ASSOCIATED TO TOXIC LEVELS OF METALS

Ectomycorrhizas are associations between plant roots and fungi. They are very important for plant survival and growth since they increase nutrient uptake and protect plants against adverse conditions. Ectomycorrhizal fungi are able to chelate ions of toxic metals, removing them from the soil and reducing damages to the host. Four isolates of ectomycorrhizal fungi were used in this study: UFSC-Sc68 (Scleroderma sp.); UFSC-Ch163 (Chondrogaster angustisporus); UFSC-Pt116 and UFSC-Pt188 (Pisolithus microcarpus). Seedlings of Eucalyptus dunnii were tested for their response to aluminium (Al), cadmium (Cd), chromium (Cr) and manganese (Mn) mixed to the planting substrate in two experiments under greenhouse conditions. In the first experiment, in the absence of the fungi and, in the second experiment, after inoculation with those organisms. In the experiment with non-inoculated seedlings, Cr was the most toxic metal. No plant survived when submitted to 1.000 and 10.000 mg.kg(-1) of this metal. Regarding the other metals, the dry matter decreased as the concentration was increased. In the experiment with inoculated seedlings, Cd was the most toxic metal, reducing significantly plant survival and growth. The isolates UFSC-Pt188 and UFSC-Ch163 were the most efficient in protecting plants against metals, improving the survival and the production of dry matter. The isolate UFSC-Ch163, particularly, was the most efficient in improving metal tolerance by the plants, indicating its potential for utilization in contaminated soils to promote plant survival and growth.