Nickel toxicity to fungi: influence of environmental factors

The toxicity of nickel (Ni) to the mycelial growth rates of filamentous fungi was influenced by environmental abiotic factors. Increasing the pH from acidic to alkaline levels completely eliminated the toxicity of Ni to Achyla sp. and Saprolegnia sp. Magnesium or zinc, but not potassium, sodium, calcium, or ferric, ions reduced the toxicity of Ni to Achyla sp. An antagonistic interaction between a combination of Ni + Pb was noted toward growth of Achyla sp. and Saprolegnia sp.; the interactions between combinations of Ni + Cd or Ni + Hg were less well defined. Chlorophyll, at 1%, reduced the toxicity of Ni toward Saprolegnia sp. and Cunninghamella blakesleeana, and increasing the chlorophyll concentration from 0.2 to 1% progressively reduced the toxicity of Ni to Aspergillus clavatus. The addition of 1% humic acid reduced the toxicity of Ni to Saprolegnia sp. and C. blakesleeana, and increasing the humic acid concentration from 0.2 to 1% progressively reduced the toxicity of Ni toward Aspergillus flavus. A. flavus was more resistant to Ni at 33 than at 23 degrees C.