Diurnal Dynamics of SIF, Photosynthesis and Plant Water Status in Maize

Solar-induced chlorophyll fluorescence (SIF) offers a promising method to remotely monitor photosynthesis at the canopy and regional scale. However, in order to interpret satellite SIF measurements in a biological context, there needs to be a better understanding of the diurnal dynamics of SIF and photosynthesis under variable stress conditions. Photons absorbed by a leaf can enter photochemistry, be actively dissipated via non-photochemical quenching (NPQ), or be re-emitted as chlorophyll fluorescence. Therefore, having better understanding of NPQ should improve interpretation of SIF. At the canopy scale, we utilized the photochemical reflectance index (PRI) to capture diurnal dynamics of xanthophyll cycle-mediated NPQ. We then coupled leaf-level measurements of photosynthesis and plant water status with canopy-level SIF, PRI and GPP to explain responses of maize to water stress in a field situated in upstate New York.