| Abstract: | Al and Pb tolerance of different ectomycorrhizal fungi was tested in Petri dishes divided into three compartments. One compartment contained nutrient solution supplemented with Al or Pb but without P to avoid precipitation of Al or Pb phosphates. Phosphate was supplied in the agar compartment while a third compartment served as control containing nutrient solution without P. The tested ectomycorrhizal fungal species and isolates varied greatly in their Al and Pb tolerance. A more than 50% growth reduction was observed at 2000 μM Al in Paxillus involutus MAI but already at 200 μM in P. involutus NAU and P. involutus 533. In contrast, growth of Pisolithus tinctorius 956 appeared to be stimulated by Al. Al tolerance therefore decreased in the following order: P. tinctorius 956 > P. involutus MAI > P. involutus NAU, P. involutus 533. To test the effect of agar on Al tolerance, P. involutus MAI was grown with agar in all three compartments. In presence of agar, even 2000 μM Al had no effect on growth. Lead at concentrations of 1 and 10 μM Pb had no significant effect on fungal growth. A more than 50% decrease of mycelial surface area occurred at 500 μM Pb in P. involutus MAI and P. involutus 533 and at 100 μM Pb in P. involutus NAU and P. tinctorius 956. Pb tolerance therefore decreased in the following order: P. involutus MAI, P. involutus 533 > P. involutus NAU, P. tinctorius 956. Divided Petri plates appear to be a valuable tool to test metal tolerance of fungi as complexation of the metals by agar or precipitation with P are avoided. The results indicate that some ectomycorrhizal fungi may be more sensitive to Al and Pb than previously reported. |
