# Phenotyping canopy-level photosynthetic responses to intermittent shading: beyond the daily light integral in multilayered cropping systems

Laura Lescroart, Marcos Mc Cormick, El Hadji Boubabar Sarr, Christine Granier, Frédéric Boudon, Maxime Duthoit, Hélène Marrou, Raphaël Perez

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## To cite this version:

Laura Lescroart, Marcos Mc Cormick, El Hadji Boubabar Sarr, Christine Granier, Frédéric Boudon, et al.. Phenotyping canopy-level photosynthetic responses to intermittent shading: beyond the daily light integral in multilayered cropping systems. European Plant Phenomics Symposium (EPPS 2025), EPPS; Forschungszentrum Jülich, Sep 2025, Bonn, Germany. 1 p. hal-05346855

HAL Id: hal-05346855

https://hal.science/hal-05346855v1

Submitted on 4 Nov 2025

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# Phenotyping canopy-level photosynthetic responses to intermittent shading: beyond the daily light integral in multilayered cropping systems

Laura LESCROART¹,², Marcos MCCORMICK¹,², El Hadji Boubabar SARR¹,², Christine GRANIER², Frédéric BOUDON¹,², Maxime DUTHOIT³,⁴, Hélène MARROU², Raphaël PEREZ¹,²

¹ CIRAD, UMR AGAP Institut, Montpellier, France

² UMR AGAP Institut, Univ Montpellier, CIRAD, INRAE, Institut Agro, Montpellier, France

³ UMR Eco&Sols, Univ Montpellier, CIRAD, INRAE, IRD, Montpellier SupAgro, Montpellier, France

⁴ CIRAD, UMR Eco&Sols, F-34398 Montpellier, France

Multilayered cropping systems such as agrivoltaics, agroforestry, and intercropping create spatiotemporal light variability, including daily shade intermittence. While its physiological impacts are recognised, shade intermittence remains understudied and is not accounted for in crop models, which typically consider a daily light integral (DLI). Beyond photosynthetic adjustments to rapid light changes, it also affects integrative traits such as plant morphology and reduces radiation use efficiency (RUE) compared to constant shading with the same daily light integral. In a recent experiment across 14 rice genotypes, intermittent shading was compared to constant shade with the same DLI. Yield and aboveground biomass were significantly reduced, likely due to source limitations. These limitations were driven by the natural nonlinear light-assimilation response and decreased photosystem efficiency, with ΦPSII and electron transport rates reduced under both low and high light. Crop responses were consistent among genotypes, but performance varied widely. These findings emphasise the need to consider factors beyond DLI, such as shading dynamics, when phenotyping crop responses in such systems. Moreover, plant responses to shade intermittence vary with shading amplitude, frequency, and duration. To address this, we combined canopy-level flux chamber measurements with leaf-level photosynthesis assessments (Li-6800) on two rice varieties. The flux chamber produced five daily shade intermittence patterns using removable shading nets. Canopy assimilation was measured under these patterns and combined with leaf-level fluorescence (ΦPSII, NPQ, ETR) and gas exchange measurements to characterise photosynthetic responses in detail. Objectives include observing canopy assimilation dynamics under varying shading durations, identifying traits relevant for phenotyping rice photosynthesis under intermittent shading, and determining shading pattern variables that explain these responses for modelling. This approach to phenotyping photosynthesis and carbon assimilation under intermittent shading opens new possibilities for improving genotype selection and optimising multilayered system design.