Uptake of zinc, cadmium and phosphorus by arbuscular mycorrhizal maize (Zea mays L.) from a low available phosphorus calcareous soil spiked with zinc and cadmium.

In a multifactorial pot experiment, maize (Zea mays L.) with or without inoculation with the arbuscular mycorrhizal (AM) fungus Glomus mosseae BEG167 was grown in a sterilized soil spiked with three levels of zinc (0, 300 and 900 mg Zn kg(-1) soil) and three levels of cadmium (0, 25 and 100 mg Cd kg(-1) soil). At harvest after 8 weeks of growth, the proportion of root length of inoculated plants colonized decreased with increasing Zn or Cd addition, and was 56% in the absence of both metals and was reduced significantly to 27% in the presence of the higher levels of both metals. Mycorrhizal plants had higher biomass than non-mycorrhizal controls except at the highest soil level of Cd. Cadmium had more pronounced effects on plant biomass than did Zn at the levels studied and the two metals showed a significant interaction. The data suggest that mycorrhizal inoculation increased plant growth with enhancement of P nutrition, perhaps increasing plant tolerance to Zn and Cd by a dilution effect. AM inoculation also led to higher soil solution pH after harvest, possibly reducing the availability of the metals for plant uptake, and lowered the concentrations of soluble Zn and Cd in the soil solution, perhaps by adsorption onto the extrametrical mycelium.