Divergent sensitivity of red and far-red Fraunhofer line fluorescence in-filling to water stress dynamics in almond orchards

Plant primary responses to water stress involve changes in both transpiration and photosynthesis, with the relationship between these processes varying during the stress. Currently, precision irrigation decisions are based mainly on transpiration as an indicator of water stress. However, this practice can be misleading as crop yield and quality are also affected by stress-related impairment of photosynthesis, which may be hidden in remote sensing thermal data. In this study, we acquired airborne hyperspectral and thermal imagery to evaluate the coupling between transpiration and photosynthesis in almond ( Prunus dulcis ) trees at mild- and high-level water stress and post-rehydration recovery stages, assessing canopy–air temperature difference (T c T a ) as a marker of transpiration, with sun-induced chlorophyll fluorescence (SIF) and fluorescence in-filling across Fraunhofer lines (FLs;…