Effects of EDTA application and arbuscular mycorrhizal colonization on growth and zinc uptake by maize (Zea mays L.) in soil experimentally contaminated with zinc

A pot experiment was conducted to investigate the uptake of Zn from experimentally contaminated calcareous soil of low nutrient status by maize inoculated with the arbuscular mycorrhizal ( AM) fungus Glomus caledonium. EDTA was applied to the soil to mobilize Zn and thus maximize plant Zn uptake. The highest plant drymatter (DM) yields were obtained with a moderate Zn addition level of 300 mg kg(-1). Plant growth was enhanced by mycorrhizal colonization when no Zn was added and under the highest Zn addition level of 600 mg kg(-1), while application of EDTA to the soil generally inhibited plant growth. EDTA application also increased plant Zn concentration, and Zn accumulation in the roots increased with increasing EDTA addition level. The effects of inoculation with G. caledonium on plant Zn uptake varied with Zn addition level. When no Zn was added, Zn translocation from roots to shoots was enhanced by mycorrhizal colonization. In contrast, when Zn was added to the soil, mycorrhizal colonization resulted in lower shoot Zn concentrations in mycorrhizal plants. The P nutrition of the maize was greatly affected by AM inoculation, with mycorrhizal plants showing higher P concentrations and P uptake. The results indicate that application of EDTA mobilized soil Zn, leading to increased Zn accumulation by the roots and subsequent plant toxicity and growth inhibition. Mycorrhizal colonization alleviated both Zn deficiency and Zn contamination, and also increased host plant growth by influencing mineral nutrition. However, neither EDTA application nor arbuscular mycorrhiza stimulated Zn translocation from roots to shoots or metal phytoextraction under the experimental conditions. The results are discussed in relation to the environmental risk associated with chelate-enhanced phytoextraction and the potential role of arbuscular mycorrhiza in soil remediation.