Deriving diurnal variations in sun-induced chlorophyll-a fluorescence in winter wheat canopies and maize leaves from ground-based hyperspectral measurements

Abstract

Remote sensing of solar-induced chlorophyll-a fluorescence (SIF) is a promising method for quantifying photosynthetic activity at the Earth's surface. Some recent studies therefore aim to clarify to what extend passive SIF measurements can be used to track photosynthetic processes. The present study contributes to that research by investigating the diurnal relationship between shortterm variability of SIF and gas exchange rates in terms of stomatal conductance (g s ). Quantification of SIF was performed using the Fraunhofer line discriminator (FLD) principle in the O 2 -A absorption band and by applying a novel approach using the second derivative of the reflectance. Experimental measurements were conducted for two crops, namely winter wheat and maize under stressed and unstressed conditions. Overall, 47 high-spectral-resolution signatures and measurements of g s were collected on three different days during the 2014 growing season. During two days of unstressed conditions, diurnal variability of g s could -to a large extent (R 2 = 0.62 and 0.78) -be explained by the fraction of SIF in the target radiance flux between 655 and 665 nm (F fraction ). In an experiment with heat and water stress no diurnal relationship appeared between g s and F fraction , which can be attributed to the occurrence of non-photochemical quenching under stress conditions. ARTICLE HISTORY

Downscaling of far-red solar-induced chlorophyll fluorescence of different crops from canopy to leaf level using a diurnal data set acquired by the airborne imaging spectrometer HyPlant

“…In general, observed diurnal trends of and for all crops followed the temporal dynamic of PAR. This is in accordance with previous studies presenting diurnal courses of SIF 760 of different plants at canopy ( Campbell et al, 2019 ; Liu et al, 2017 ) and leaf level ( Süß et al, 2016 ; Amoros-Lopez et al, 2008 ). In addition, several studies reported data ranges of ( Liu et al, 2019 ; Pinto et al, 2017 ; Rossini et al, 2015 ; Wieneke et al, 2016 ) comparable to those shown here.…”

Diurnal Response of Sun-Induced Fluorescence and PRI to Water Stress in Maize Using a Near-Surface Remote Sensing Platform

“…Analogous to NDVI, PRI is calculated using Equation (1), which uses reflectance at 531 nm and a reference reflectance at 570 nm that is insensitive to the xanthophyll cycle [11]. It has been demonstrated that PRI can track changes in the photosynthesis and water stress of plants at the canopy level using ground or aerial platforms [4,12,16,20].…”

Ground Based Hyperspectral Imaging to Characterize Canopy-Level Photosynthetic Activities

“…Common SIF retrieval approaches include conventional Fraunhofer line discrimination (FLD), improved FLD variants, and reflectance-based ratios [24]. Many studies explored the use of ground based spectrometers to retrieve the SIF values of plant leaves, and reported high correlations between SIF measurements and fluorescence measured using active techniques (e.g., PAM fluorometers) [24][25][26][27]. Large national research institutions (e.g., the European Space Agency, the EPA, and the National Aeronautics and Space Administration (NASA)) launched programs to investigate the use of hyperspectral imagery sensed remotely from planes and satellites to monitor SIF changes at the regional and global levels, to estimate carbon fixation (or flux of carbon dioxide) and gross primary productivity (GPP).…”