Abstract
Plants tend to die earlier in hot and drought conditions, but the underlying mechanisms are not yet understood. I propose here a new mechanism by which excessive residual water losses caused by high cuticular permeabilities and a high leaf-to-air vapor pressure deficits would trigger uncontrolled and sudden cavitation events. The combination of heat and drought stresses may therefore lead to an unsuspected risk of hydraulic failure. I explored this hypothesis with a new mechanistic model. The simulations support this hypothesis and highlight the critical role played by the cuticle phase transition temperature. Experiments are now awaited to confirm these predictions.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Cite as: Cochard, H. (2020) A new mechanism for tree mortality due to drought and heatwaves. bioRxiv, 531632, ver. 2 peer-reviewed and recommended by PCI Forest and Wood Sciences. doi: https://doi.org/10.1101/531632
Version 2 of this preprint has been peer-reviewed and recommended by Peer Community In Forest and Wood Sciences (https://doi.org/10.24072/pci.forestwoodsci.100002)
- eleaf (kPa)
- Vapor pressure of water in the leaf at Tleaf and ⍰leaf
- esat_leaf (kPa)
- Saturation vapor pressure in the leaf at Tair
- eair (kPa)
- Vapor pressure of water in the air at Tair
- esat_air (kPa)
- Saturation vapor pressure of the air at Tair
- E (mmol s−1 m−2)
- Leaf transpiration rate
- FT (poise−1)
- Dynamic fluidity of water
- gleaf (mmol s−1 m−2)
- Maximum leaf conductance to vapor
- gmin (mmol s−1 m−2)
- Minimum (residual) leaf conductance
- gs (mmol s−1 m−2)
- Leaf stomatal conductance
- Kplant (mmol s−1 MPa−1)
- Whole plant hydraulic conductance
- KT (mmol s−1 MPa−1)
- Hydraulic conductance
- Pair (kPa)
- Atmospheric pressure
- Pleaf (MPa)
- Leaf turgor pressure
- P50 (MPa)
- Xylem pressure inducing 50% loss of hydraulic conductance
- Q10a
- Leaf cuticle Q10 value below Tp
- Q10b
- Leaf cuticle Q10 value above Tp
- RHair (%)
- Air relative humidity
- RHair-min (%)
- Minimum daily air relative humidity
- RHair-max (%)
- Maximum daily air relative humidity
- tg0 (s)
- Time to stomatal closure
- tHF (s)
- Time to hydraulic failure
- Tair (°C)
- Air temperature
- Tair-min (°C)
- Minimum daily air temperature
- Tair-max (°C)
- Maximum daily air temperature
- Tleaf (°C)
- Leaf temperature
- Tp (°C)
- Leaf cuticle phase transition temperature
- VPD (kPa)
- Vapor pressure deficit between the leaf and the air
- ε (MPa)
- Leaf modulus of elasticity
- σT (Nm−1)
- Water surface tension.
- Ψleaf (MPa)
- Leaf water potential
- ΠT (MPa)
- Leaf osmotic potential