Response of A. gerardii to Arbuscular Mycorrhizal Fungi in the Context of Phytoremediation

Heavy metal contamination is one of the most pervasive and devastating environmental issues facing our world today. Phytoremediation, or the use of plants to restore polluted soils, holds significant promise for the treatment of heavy metal pollution. Phytoremediation provides a cheaper and cleaner alternative to destructive traditional methods. Incorporating obligate symbionts like arbuscular mycorrhizal fungi (AMF) is vital to the effectiveness of phytoremediation. We performed a greenhouse experiment to examine the efficacy of AMF in soils polluted with Zn, Cd, and Pb from nearly a century of zinc smelting. We measured performance of two Andropogon gerardii ecotypes: seeds collected from recent plantings on site and from a natural grassland on a serpentine outcrop, which is high in Ni, Mg, Cr, and Fe. We used whole soil and root inoculum (10ml) to apply AMF species: Rhizophagus clarus, Claroideoglomus etunicatum, a 1:1 mixture of the two, or sterile inoculum. Plant ecotype and AMF factors were fully-factorial with two levels of soil metal contamination, thereby producing 16 distinct treatment combinations. After 10 weeks, we assessed plant height, biomass, and mycorrhizal root colonization.

Plant height, biomass, and AMF colonization varied with all three experimental factors. The importance of AMF to A. gerardii in these soil environments is evinced by plants without AMF having 600-700% less biomass than those with AMF. Provided that AMF are present, A. gerardii thrives in high stress environments, signifying it as an operative phytoremediator. A tradeoff between economic and AMF efficiency was discovered. An equilibrium between the cost and effectiveness of a remediation plan is vital. These results will provide a greater understanding of the importance of AMF to phytoremediation and allow for increased implementation of phytoremediation.