Arbuscular mycorrhizas modify plant responses to soil zinc addition

Zinc deficiency is one of the most commonly reported plant and human nutrient deficiencies worldwide. Conversely, Zn is also a common environmental contaminant, significantly reducing plant growth. These contrasting effects of Zn on plant growth and nutrition have been the focus of a considerable number of studies; however, most studies focus on plant responses to soil Zn concentration under either deficient or toxic concentrations, but not both. The formation of arbuscular mycorrhizas (AM) can increase plant Zn uptake under low soil Zn concentrations, and on the other hand, ‘protect’ plants against excessive Zn accumulation under high soil Zn conditions. Here we report the findings of an experiment in which we studied the response of AM formed by tomatoes under low, medium and high soil Zn conditions. To control for the formation of AM in this study we used a mycorrhiza defective tomato mutant and its mycorrhizal wildtype progenitor. While mycorrhizal colonization was not significantly impacted by soil Zn addition, the growth of plants and tissue Zn concentrations were. Together these data highlight the complex interactions between AM and Zn, and the utility of a genotypic approach for studying AM in this context.