THE BREAKDOWN OF PARAQUAT AND DIQUAT BY SOIL FUNGI

Abstract

S ummary Mucor hiemalis, Zygorhynchus heterogamous, Aspergillus niger and Penicillium frequentans were incubated in media containing either [methyl‐ 14 C] paraquat or [ethylene‐ 14 C] diquat. Aspergillus niger liberated 14 CO 2 from both herbicides and Penicillium frequentans only from paraquat. Mucor hiemalis and Zygorhynchus heterogamous were unable to release 14 CO 2 from either. Those species able to degrade paraquat or diquat have correspondingly low intracellular levels of the herbicides and are able to tolerate high concentrations in the medium. By contrast, species unable to break them down are characterized by high intracellular levels and by their inability to grow at low concentrations. Tolerance to these herbicides appears to be the result of an ability to degrade them.