Stomatal closure during water deficit is controlled by below-ground hydraulics
Mohanned Abdalla1,2, Mutez Ali Ahmed1,3, Gaochao Cai1
1Chair of Soil Physics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany.
Annals of Botany
|December 6, 2021
Summary
Plant root hydraulics significantly influence stomatal closure during drought. Shorter root systems lead to earlier stomatal closure, highlighting the critical role of below-ground water transport in plant drought response.
Area of Science:
- Plant Physiology
- Soil-Plant Hydraulics
- Drought Stress Response
Background:
- Stomatal closure is a key plant response to water scarcity.
- While leaf and xylem hydraulics are well-studied, the influence of below-ground hydraulics on stomatal regulation is largely unknown.
Purpose of the Study:
- To investigate the impact of below-ground hydraulics on stomatal regulation during soil drying.
- To determine how rootstock characteristics affect the relationship between transpiration and leaf water potential.
Main Methods:
- Utilized a novel root pressure chamber to measure transpiration rate (E) versus leaf xylem water pressure (ψleaf-x) in tomato plants with contrasting rootstocks.
- Measured the E(ψleaf-x) relationship under drying soil conditions and with and without root pressurization.
- Employed a soil-plant hydraulic model to simulate and interpret the experimental data.
Main Results:
- The E(ψleaf-x) relationship transitioned from linear to non-linear as soil dried.
- Root system length significantly altered the E(ψleaf-x) relationship during drought.
- Plants with shorter root systems exhibited earlier non-linearity and stomatal closure, requiring greater soil water pressure gradients for transpiration.
Conclusions:
- Stomatal regulation during soil drying is predictably controlled by below-ground hydraulics.
- Hydraulic conductivity loss in the soil is a likely driver of observed non-linearity.
- Stomatal regulation is intrinsically linked to root and soil hydraulic conductances.
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