The role of arbuscular mycorrhizas in improving plant zinc nutrition under low soil zinc concentrations: a review

Many of the world's soils are zinc (Zn) deficient. Consequently, many crops experience reduced growth, yield and tissue Zn concentrations. Reduced concentrations of Zn in the edible portions of crops have important implications for human Zn nutrition; this is a cause of global concern. Most terrestrial plant species form arbuscular mycorrhizas (AM) with a relatively limited number of specialized soil fungi. Arbuscular mycorrhizal fungi (AMF) can take up nutrients, including Zn, and transfer them to the plant, thereby enhancing plant nutrition. Under high soil Zn concentrations the formation of AM can also 'protect' against the accumulation of Zn in plant tissues to high concentrations. Here, a short review focusing on the role of AM in enhancing plant Zn nutrition, principally under low soil Zn concentrations, is presented. Effects of Zn on the colonisation of roots by AMF, direct uptake of Zn by AMF, the role of AM in the Zn nutrition of field grown plants, and emerging aspects of Zn molecular physiology of AM, are explored. Emergent knowledge gaps are identified and discussed in the context of potential future research.