Exploring the scattering and reabsorption of chlorophyll fluorescence: implications for remote sensing of photosynthesis

M.P. Cendrero-Mateo1,2, Christiaan van der Tol3, Karolina Sakowska4,5, Marco Celesti6, Anke Schickling1,7, Giorgio Alberti8, Luis Alonso2, Andreas Burkart9, Sergio Cogliati6, Roberto Colombo6, Gemini Delle Vedove8, Tommaso Julitta9, Radosław Juszczak10, Jose Moreno2, Onno Muller1, Cinzia Panigada6, Alessandro Peressotti8, Patrick Rademske1, Micol Rossini6, Giulia Tagliabue6, Nastassia Vilfan11, Peiqi Yang2, Franco Miglietta4,12, and Uwe Rascher1

1Institute of Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich GmbH, Germany; 2Image Processing Laboratory, University of Valencia, Spain; 3University of Twente, Faculty of Geo-Information Science and Earth Observation (ITC), The Netherlands; 4Institute of BioEconomy (IBE), National Research Council (CNR), Italy; 5Institute of Ecology, University of Innsbruck, Austria; 6Department of Earth and Environmental Sciences, University of Milano-Bicocca, Italy; 7German Aerospace Center, Germany; 8Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Italy; 9JB Hyperspectral Devices UG, Germany; 10Laboratory of Bioclimatology, Department of Ecology and Environmental Protection, Poznan University of Life Sciences, Poland;11Wageningen University & Research, Business Unit Greenhouse Horticulture, The Netherlands; 12Foxlab Joint CNR-FEM Initiative, Italy

Introduction

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Materials and Methods

POT AND FIELD TRIAL

UDINE, ITALY46°02'9.14"N, 13°13'31.63"E

Photosynthetic capacity and PAM fluorescence

SIF and transmittance, reflectance, absorbance

Specific leaf massPigments content Nitrogen content

fAPPFD LAI

NEE Reco

CANOPY

LEAF

CO2 exchange (GPP)

Transpiration

The principle underlying the use of sun-induced chlorophyllfluorescence (SIF) as a proxy of gross primary productivity(GPP) is based on the fact that the light energy absorbed bychlorophyll molecules can proceed into three differentpathways: photochemistry, heat dissipation, and chlorophyllfluorescence.Since these processes directly compete for the sameexcitation energy, measurements of SIF and non-photochemical quenching (NPQ) are expected to provideinformation on photosynthetic performance.However, SIF signal measured at the leaf level or beyond isaffected by several processes, including wavelengthdependent scattering and reabsorption, which may need tobe considered when linking SIF data and photosynthetic CO2assimilation.To address this question, we conducted a multi-scale andmulti-technique study that considered two soybean varietiesand used the collected data to calibrate the “Soil-CanopyObservation Photosynthesis and Energy fluxes” (SCOPE)model as a tool to investigate the reabsorption andscattering of SIF.

Full spectrum active fluorescence

SIF and reflectance

FLOXMSS

VARIANT 1Top of canopy SIF

reabsorption by leaves and canopy

VARIANT 2SIF emitted by photosystems

NO reabsorption by leaves and canopy

ME

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BIOPHYSICAL PARAMETERS

LEAF NET PHOTOSYNTHESIS vs. PPFD ABSORBED BY THE LEAF

NDVIMTCI

FRACTION OF PHOTOSYNTHETIC PHOTON FLUX DENSITY ABSORBED BY THE CANOPY

CANOPY LEVELSPECTRAL VEGETATION INDICES

CANOPY LEVELSIF and SIF YIELD

SIF

SIF

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Conclusions

MODELLING RESULTS

Source: © Cendrero-Mateo et al. All rights reserved.Source: © Cendrero-Mateo et al. All rights reserved.

NON-PHOTOCHEMICAL QUENCHING

Reflected PPFD

Transmitted PPFD

Photochemistry (P)

Chlorophyll fluorescence (SIF)

IncidentPPFD

Absorbed PAR (APAR)

18-98%

up to 82%

0.5-2%

Heat (NPQ)

Eiko < MinnGold3% < 10%

Reflected PPFD

• Despite the large difference in Chl content (the ratio of Chl between MinnGold and Eiko wasnearly 1:5), similar leaf and canopy photosynthesis rates were maintained in the Chl‐deficientmutant.

• This phenomenon wasn’t captured by traditional spectral vegetation indices related tocanopy greenness, nor by SIF measured in-situ.

• However, the modelling simulations revealed that when correcting for leaf and canopyscattering and reabsorption processes both varieties presented similar SIF yield (SIF/APPFD).

• Furthermore, both in-situ and modelled data showed that APPFD and NPQ in MinnGold werelower than in Eiko.

• This together explains the similar measured GPP and simulated SIF yield between the twovarieties, and indicates that interpretation and application of SIF as a GPP tracer requiresunderstanding and quantification of all these processes.

The SCOPE model was used to investigate the reabsoption and scattering of SIF

Data source:1) Sakowska et al. (2018) https://doi.org/10.1111/pce.13180

2) Cendrero-Mateo et al. (in preparation, all rights reserved)

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Legend:N – mesophyll scattering parameter

Cx – photochemical reflectance parameter, proxy of NPQ fqe - fluorescence quantum emission efficiency

LIDFa, LIDFb - leaf inclination parametersAPPFD – the amount of absorbed photosynthetically active photons

fAPPFD – fraction of absorbed photosynthetically active photons

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Top of canopy SIF SIF emitted by photosystems

LEAF LIGHT ABSORBANCE AT DIFFERENT WAVELENGTHS

Sakowska et al. (2018) https://doi.org/10.1111/pce.13180GROSS PRIMARY PRODUCTIONvs. PPFD ABSORBED BY THE CANOPY

Sakowska et al. (2018) https://doi.org/10.1111/pce.13180

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Sakowska et al. (2018) https://doi.org/10.1111/pce.13180 Sakowska et al. (2018) https://doi.org/10.1111/pce.13180

Sakowska et al. (2018) https://doi.org/10.1111/pce.13180

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