Interactions of Vesicular-Arbuscular Mycorrhizal Infection and Heavy Metals in Plants. I. The Effects of Heavy Metals on the Development of Vesicular-Arbuscular Mycorrhizas

The degree of infection of onions with the vesicular-arbuscular mycorrhizal fungus Glomus mosseae was strongly reduced by additions of zinc, copper, nickel or cadmium to the soil medium, and could be completely elimited by heavy rates of application. A split pot experiment was used to show that zinc translocated within the plant from other roots was effective in decreasing infection levels. Despite this, clover plants growing on areas which had been heavily contaminated with metal were found to be strongly infected with mycorrhizal fungi. A comparison of G. mosseae isolated from these plants with the isolate used at Rothamsted showed the former to be much more tolerant of zinc and cadmium in the soil. There was some indication that mycorrhizal infection, particularly with the tolerant isolate, could protect plants against the effects of heavy metal additions. These infections might be very important in revegetation of polluted sites.