PT  - JOURNAL ARTICLE
AU  - Cochard, Hervé
TI  - A new mechanism for tree mortality due to drought and heatwaves
AID  - 10.1101/531632
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 531632
4099  - http://biorxiv.org/content/early/2020/12/05/531632.short
4100  - http://biorxiv.org/content/early/2020/12/05/531632.full
AB  - 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 StatementThe authors have declared no competing interest.Abbreviations:eleaf (kPa)Vapor pressure of water in the leaf at Tleaf and ⍰leafesat_leaf (kPa)Saturation vapor pressure in the leaf at Taireair (kPa)Vapor pressure of water in the air at Tairesat_air (kPa)Saturation vapor pressure of the air at TairE (mmol s−1 m−2)Leaf transpiration rateFT (poise−1)Dynamic fluidity of watergleaf (mmol s−1 m−2)Maximum leaf conductance to vaporgmin (mmol s−1 m−2)Minimum (residual) leaf conductancegs (mmol s−1 m−2)Leaf stomatal conductanceKplant (mmol s−1 MPa−1)Whole plant hydraulic conductanceKT (mmol s−1 MPa−1)Hydraulic conductancePair (kPa)Atmospheric pressurePleaf (MPa)Leaf turgor pressureP50 (MPa)Xylem pressure inducing 50% loss of hydraulic conductanceQ10aLeaf cuticle Q10 value below TpQ10bLeaf cuticle Q10 value above TpRHair (%)Air relative humidityRHair-min (%)Minimum daily air relative humidityRHair-max (%)Maximum daily air relative humiditytg0 (s)Time to stomatal closuretHF (s)Time to hydraulic failureTair (°C)Air temperatureTair-min (°C)Minimum daily air temperatureTair-max (°C)Maximum daily air temperatureTleaf (°C)Leaf temperatureTp (°C)Leaf cuticle phase transition temperatureVPD (kPa)Vapor pressure deficit between the leaf and the airε (MPa)Leaf modulus of elasticityσT (Nm−1)Water surface tension.Ψleaf (MPa)Leaf water potentialΠT (MPa)Leaf osmotic potential