Re-absorption of chlorophyll fluorescence in canopies: a revised approach

MARÍA GABRIELA LAGORIO; GABRIELA CORDON; JUAN M. ROMERO

CABA

Simposio; Exploring the Frontiers of Chemistry: Challenges for the 21st Century; 2019

Facultad de Ciencias Exactas y Naturales de la UBA y Ben-Gurion University

Chlorophyll fluorescence is widely used as an indicator of photosynthesis and physiological state of plants. Remote acquisition of fluorescence allows the diagnosis of large field extensions, even from satellite measurements, becoming increasingly important in relation to the monitoring of plant health and Carbon Budget on the planet [1]. Nevertheless, fluorescence emerging from chloroplasts, the one directly connected to plant physiology, undergoes re-absorption processes both inside the leaf and the canopy [2]. Therefore, to draw accurate inferences about plant health, it is necessary to correct the observed canopy fluorescence taking into account these two re-absorption processes. Here we show the theoretical refinement and experimental validation of a biophysical model we developed in 2018 [3], which allows retrieving leaf fluorescence from that at top of canopy (TOC) using a correction factor which is a function of canopy and soil reflectance and canopy transmittance.We validate this model in three types of crops of agronomic interest (Pea, Rye grass and Maize) with different architecture. Our model accurately predicts leaf fluorescence spectral distribution from that measured at canopy level and also the fluorescence ratio. Furthermore, we not only eliminate artifacts affecting the spectral distribution of the emission, but we are able to calculate the quantum yield of fluorescence at leaf level from the experimental quantum yield at the canopy level. This represents an advance in the study of these systems because it allows correcting by light re-absorption, not only the fluorescence ratio but also the intensity of the observed fluorescence.[1] Meroni, M., Rossini, M., Guanter, L., Alonso, L., Rascher, U., Colombo, R., & Moreno, J. (2009). Remote sensing of solar-induced chlorophyll fluorescence: Review of methods and applications. Remote Sensing of Environment, 113(10), 2037 ?2051.[2] Porcar-Castell, A., Tyystjärvi, E., Atherton, J., Van Der Tol, C., Flexas, J., Pf ündel, E. E., ? Berry, J. A. (2014). Linking chlorophyll a fluorescence to photosynthesis for remote sensing applications: Mechanisms and challenges. Journal of Experimental Botany, 65(15), 4065 ?4095. https://doi.org/10.1093/jxb/eru191[3] Romero, J. M., Cordon, G. B., & Lagorio, M. G. (2018). Modeling re-absorption of fluorescence from the leaf to the canopy level. Remote Sensing of Environment, 204 (October), 138 ?146.