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Article

Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles

1
Optics of Photosynthesis Laboratory, Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, 00014 Helsinki, Finland
2
Image Processing Laboratory (IPL), University of Valencia, Paterna, 46980 València, Spain
*
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(5), 532; https://doi.org/10.3390/rs11050532
Submission received: 5 December 2018 / Revised: 20 February 2019 / Accepted: 26 February 2019 / Published: 5 March 2019

Abstract

Successful measurements of chlorophyll fluorescence (ChlF) spectral properties (typically in the wavelength range of 650–850 nm) across plant species, environmental conditions, and stress levels are a first step towards establishing a quantitative link between solar-induced chlorophyll fluorescence (SIF), which can only be measured at discrete ChlF spectral bands, and photosynthetic functionality. Despite its importance and significance, the various methodologies for the estimation of leaf-level ChlF spectral properties have not yet been compared, especially when applied to leaves with complex morphology, such as needles. Here we present, to the best of our knowledge, a first comparison of protocols for measuring leaf-level ChlF spectra: a custom-made system designed to measure ChlF spectra at ambient and 77 K temperatures (optical chamber, OC), the widely used FluoWat leaf clip (FW), and an integrating sphere setup (IS). We test the three methods under low-light conditions, across two broadleaf species and one needle-like species. For the conifer, we characterize the effect of needle arrangements: one needle, three needles, and needle mats with as little gap fraction as technically possible. We also introduce a simple baseline correction method to account for non-fluorescence-related contributions to spectral measurements. Baseline correction was found especially useful in recovering the spectra nearby the filter cut-off. Results show that the shape of the leaf-level ChlF spectra remained largely unaffected by the measurement methodology and geometry in OC and FW methods. Substantially smaller red/far-red ratios were observed in the IS method. The comparison of needle arrangements indicated that needle mats could be a practical solution to investigate temporal changes in ChlF spectra of needle-like leaves as they produced more reproducible results and higher signals.
Keywords: baseline correction; chlorophyll fluorescence; FluoWat; leaf morphology; lingonberry; photosynthesis; Scots pine; silver birch; sun-induced fluorescence baseline correction; chlorophyll fluorescence; FluoWat; leaf morphology; lingonberry; photosynthesis; Scots pine; silver birch; sun-induced fluorescence
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MDPI and ACS Style

Rajewicz, P.A.; Atherton, J.; Alonso, L.; Porcar-Castell, A. Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles. Remote Sens. 2019, 11, 532. https://doi.org/10.3390/rs11050532

AMA Style

Rajewicz PA, Atherton J, Alonso L, Porcar-Castell A. Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles. Remote Sensing. 2019; 11(5):532. https://doi.org/10.3390/rs11050532

Chicago/Turabian Style

Rajewicz, Paulina A., Jon Atherton, Luis Alonso, and Albert Porcar-Castell. 2019. "Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles" Remote Sensing 11, no. 5: 532. https://doi.org/10.3390/rs11050532

APA Style

Rajewicz, P. A., Atherton, J., Alonso, L., & Porcar-Castell, A. (2019). Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles. Remote Sensing, 11(5), 532. https://doi.org/10.3390/rs11050532

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