Transpiration and Surface Temperature: from Modeling to Measurement.

The role of foliage surface temperature as the state variable that balances the plant canopy energy budget justifies its use to diagnose water availability for transpiration. Still, interpretation of leaf temperature measurement is not trivial because spatial arrangement of leaves determines their exposure to energy exchange by radiation, convection and conduction. Simplified models of the interaction between canopy geometrical structure and energy exchange show that the spatial distribution of leaf temperature widens with decreased water availability. Application of this result to detection of water stress in real plant canopies by radiative measurement of surface temperature remains a challenging issue.