THE UPTAKE AND TRANSPORT OF LEAD IN SOME ECTOMYCORRHIZAL FUNGI IN CULTURE

Various fungi interact with heavy metals (HM) differently regarding th eir binding ability and their tolerance. Besides the ability of the fu ngus to form an extensive extramatrical mycelium, its binding and tran sport properties are the most important factors in ameliorating the ef fects of HM toxicity on the mycorrhizal symbiosis. The tolerance of se ven ectomycorrhizal fungi to elevated lead concentrations was tested u sing agar cultures and the results were compared to those from liquid culture. Critical toxic concentrations, where the growth of the myceli um was inhibited to 50%, were lower in liquid cultures (around 0.2 mM) in comparison to agar cultures (0.5-2 mM). The less tolerant fungi in agar culture were Amanita muscaria and Laccaria laccata, the most tol erant Lactarius piperatus, Pisolithus tinctorius and two strains of Su illus bovinus, DB83 from a lead polluted area and DB84 from a non-poll uted area. Tolerance indices, based on the dry weight of mycelia from liquid culture, differ from the tolerance indices obtained from solid culture. L. laccata growth was limited to a lesser extent than other f ungi and the growth of S. bovinus DB83 was strongly stimulated at a Pb concentration of 30 mu M, which could indicate lower susceptibility o f this strain to low lead concentrations. The uptake, transport and re lease of Pb were then studied with Pb-210 tracer using Conway cells wi th the active tracer added to the inoculated medium in the centre comp artment. The uptake of Pb by P. tinctorius (1.1% of the added activity ) was much lower than the uptake by L. laccata and S. bovinus DB83 (6. 2 and 5.4% of the added activity respectively). The same situation was reflected in the activity of the tracer transported in the mycelia. F urther, the release of transported Pb from mycelia to the outer medium differs between L. laccata and S, bovinus DB83 mycelia, reaching 45 a nd 10% of the transported activity, respectively, indicating stronger binding of lead to S. bovinus DB83. The results of the tracer study ar e discussed with respect to various experiments with ectomycorrhizal s eedlings and lead.