The effects of arbuscular mycorrhizal fungi (AMF) on heavy metal absorption by plants are controversial. This is due to the differences in soil metal availability, AMF and plant species, and also to possible interactions among these and other environmental/abiotic factors. The aim of the experiment was to evaluate the effect of AMF inoculation (Glomus macrocarpum), and soil base saturation (SBS) on growth, nutrition and Pb uptake of soybean grown on a Latossolo Vermelho-Amarelo, an Oxisol. Plots were treated with or without AMF inoculation, raising of the soil base saturation to 63 and 82 % by two lime doses, and five Pb doses (0; 7.5; 37.5; 150; 300 mg dm-3) with Pb(NO3)2 as source. AMF inoculation improved the dry matter yield, P concentration, as well as P, Ca, Mg, Mn, Fe, and Zn shoot contents. Increasing Pb doses in the soil reduced the inoculated soybean plants' growth at both base saturation levels. At 63 % SBS, the application of the maximum Pb dose caused a decrease in the mycorrhizal colonization of 40 %; the Pb concentration of the inoculated was 30 % lower than that of the not inoculated soybean plants, and the plants presented a five times higher Pb uptake than those grown at a SBS of 82 %. Pb addition thus affected both establishment and functionality, of the symbiosis, decreasing plant growth. At the lowest SBS, the AMF played a relevant role in the decrease of shoot Pb concentration and confirmed the plant tolerance at excessive Pb concentrations in soil.
mycorrhizal fungus; heavy metal; abiotic factors; symbiosis