Mechanisms for Alleviation of Plant Water Stress Involving Arbuscular Mycorrhizas

Abstract

Arbuscular mycorrhizal (AM) fungi can aid in the alleviation of host plant water stress under soil water-deficit conditions. AM fungi are likely to alleviate water stress through a combination of processes. The mechanisms involved may operate directly through enhancing plant water uptake or indirectly through modification of the rhizosphere-soil environment. Direct mechanisms of water alleviation to the host plant have been reported through the ultra-narrow hyphal network, which is the external phase of AM fungi ability to scavenge water/nutrients within soil pores and also extend beyond the root depletion zone. Additionally, AM fungi are reported to increase beneficial plant biochemical compounds that alleviate oxidative stress (antioxidants) and enhance osmoregulation (proline) caused by soil water deficit. Indirect enhancement of soil structure to enhance soil water relations through AM fungi hyphae is through a combination of physical, biochemical, and biological soil interactions which altogether has the capacity to increase soil aggregation.