Re-absorption of chlorophyll fluorescence in canopies

MARÍA GABRIELA LAGORIO; GABRIELA B. CORDON; JUAN M. ROMERO

Buenos Aires

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

Facultad de Ciencias Exactas y Naturales, UBA

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 satellitemeasurements, becoming increasingly important in relation to the monitoring of plant health and CarbonBudget on the planet [1]. Nevertheless, fluorescence emerging from chloroplasts, the one directly connectedto plant physiology, undergoes re-absorption processes both inside the leaf and the canopy [2]. Therefore, todraw accurate inferences about plant health, it is necessary to correct the observed canopy fluorescencetaking into account these two re-absorption processes. Here we show the theoretical refinement andexperimental validation of a biophysical model we developed in 2018 [3], which allows retrieving leaffluorescence from that at top of canopy (TOC) using a correction factor which is a function of canopy and soilreflectance 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 fluorescencespectral distribution from that measured at canopy level and also the fluorescence ratio. Furthermore, we notonly eliminate artifacts affecting the spectral distribution of the emission, but we are able to calculate thequantum yield of fluorescence at leaf level from the experimental quantum yield at the canopy level. Thisrepresents an advance in the study of these systems because it allows correcting by light re-absorption, notonly 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). Remotesensing of solar-induced chlorophyll fluorescence: Review of methods and applications. Remote Sensing ofEnvironment, 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: Mechanismsand 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 theleaf to the canopy level.Remote Sensing of Environment, 204 (October), 138 ?146.