Thermeau Team

The Thermeau team's research question focuses on studying the interactions between water and heat stress. Depending on the type of interaction and the level studied, these interactions can have a synergistic effect (i.e. thermal stress increasing vulnerability to water stress, as observed during heat waves when leaves are less able to reduce their evapotranspiration) or an antagonistic effect (i.e. a species is rarely resistant to both severe drought and intense frost). These interactions can be studied through exposure to stresses:
- Simultaneous:
What are the points of articulation in responses to thermal and water stresses? This aspect requires a focus on the regulation of biophysical processes at relatively short time scales (e.g. stomatal regulation in response to a rise in temperature, root absorption in response to soil cooling).
- Successive:
How does prior exposure to one stress (water or thermal) modulate vulnerability to a subsequent stress?

This aspect draws on concepts related to the after-effects of stress, whether active in inducing a faster and/or more intense response to a second stimulus (i.e. a stress memory or “priming” effect) ; or passive, for example related to the structural consequences of impaired growth on total leaf area the following year or reduced carbon balance on frost resistance the following winter (legacy effect).

The team's approaches and expertise focus on physical measurements (assessment of material and energy flows) and biological measurements (genetic variability, phenotypic plasticity and regulation of functional responses) as part of a three-pronged approach combining field observations, experiments under controlled conditions, and experimental or predictive modelling.

In order to gain an in-depth understanding of these interactions, the team has a number of methods for studying different stresses, which can be adapted or developed depending on the context:

• Hydraulic failure in the context of cold, frost or summer water deficit stresses using flow-based methods (Xyl'Em, Cavitron), imaging (X-ray tomography, magnetic resonance imaging, CaviCam), and acoustic detection of cavitation events.
• Cellular damage in the context of cold, frost, summer water deficit, heat waves and light stress using the electrolyte leakage method, diameter variations and meristematic zone anatomy.
• Leaf function, transpiration regulation and damage to photosynthetic machinery (drought box, infrared gas analyser, fluorimetry, infrared thermography, NDVI and hyperspectral imaging).
• Growth potential through forcing tests and micro-variations in diameter.
   

A number of these methods have the potential to measure physiological processes of interest in a non-destructive, non-invasive, autonomous and rapid scanning manner, enabling them to be deployed in natural conditions to detect when physiological thresholds are exceeded.