Soil Rather Than Xylem Vulnerability Controls Stomatal Response to Drought.

Andrea Carminati,Mathieu Javaux

doi:10.1016/j.tplants.2020.04.003

Abstract

The current trend towards linking stomata regulation to plant hydraulics emphasizes the role of xylem vulnerability. Using a soil-plant hydraulic model, we show that xylem vulnerability does not trigger stomatal closure in medium-wet to dry soils and we propose that soil hydraulic conductivity loss is the primary driver of stomatal closure. This finding has two key implications: transpiration response to drought cannot be derived from plant traits only and is related to soil-root hydraulics in a predictable way; roots and their interface with the soil, the rhizosphere, are key hydraulic regions that plants can alter to efficiently adapt to water limitations. We conclude that connecting below- and aboveground hydraulics is necessary to fully comprehend plant responses to drought.

Highlights

There is an increasing need for mechanistic and predictive models of transpiration and stomatal response to drought and soil water availability
Sensitivity to hydraulic and hormonal signals differs between plant species and results in varying degrees of iso- and anisohydricity; these definitions indicate the capacity of plants to regulate stomatal conductance to maintain a constant or less constant leaf water potential [6]
Soil–Plant Water Fluxes Water flows through the soil–plant–atmosphere continuum driven by a gradient in water potential, which depends on the water flow rate and the hydraulic conductivity of the different pathways

Summary

Soil Rather Than Xylem Vulnerability Controls Stomatal Response to Drought

The current trend towards linking stomata regulation to plant hydraulics emphasizes the role of xylem vulnerability. Using a soil–plant hydraulic model, we show that xylem vulnerability does not trigger stomatal closure in mediumwet to dry soils and we propose that soil hydraulic conductivity loss is the primary driver of stomatal closure. This finding has two key implications: transpiration response to drought cannot be derived from plant traits only and is related to soil–root hydraulics in a predictable way; roots and their interface with the soil, the rhizosphere, are key hydraulic regions that plants can alter to efficiently adapt to water limitations.

Sperry and

Soil Drying Constraints on Stomatal Conductance and Transpiration

Findings

Outstanding Questions