The role of arbuscular mycorrhizal symbiosis in improving plant water status under drought

Arbuscular mycorrhizal fungi (AMF) have been presumed to ameliorate crop tolerance to drought. Here, we review the role of AMF in maintaining water supply to plants from drying soils and the underlying biophysical mechanisms. We used a soil-plant hydraulic model to illustrate the impact of several AMF mechanisms on plant responses to edaphic drought. The AMF enhance the soil's capability to transport water and extend the effective root length, thereby attenuating the drop in matric potential at the root surface during soil drying. The synthesized evidence and the corresponding simulations demonstrate that symbiosis with AMF postpones the stress onset limit, which is defined as the disproportionality between transpiration rates and leaf water potentials, during soil drying. The symbiosis can thus help crops survive extended intervals of limited water availability. We also provide our perspective on future research needs and call for reconciling the dynamic changes in soil and root hydraulics in order to better understand the role of AMF in plant water relations in the face of climate changes. We review the role of arbuscular mycorrhizal (AM) symbiosis in plant water relations in drying soils, focusing on how AM symbiosis affects below-ground hydraulics, their implications on plant stress responses, and the underlying mechanisms.

Automated summary

This article reviews the role of arbuscular mycorrhizal fungi (AMF) in improving crop drought tolerance, highlighting their effects on water supply and the biophysical mechanisms involved. Using a soil-plant hydraulic model, the authors demonstrate how AMF can enhance water transport in the soil and extend root length to mitigate the impact of soil drying on plant water potential. The synthesis of evidence and simulations suggest that AMF symbiosis postpones the onset of stress by regulating transpiration rates and leaf water potentials during drought, thus promoting crop survival under limited water availability. The article also calls for future research to integrate soil and root hydraulic dynamics in order to better understand the role of AMF in plant-water relations under changing climate conditions.