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Published September 2017 | Supplemental Material
Journal Article Open

Connecting active to passive fluorescence with photosynthesis: a method for evaluating remote sensing measurements of Chl fluorescence

Abstract

Recent advances in the retrieval of Chl fluorescence from space using passive methods (solar-induced Chl fluorescence, SIF) promise improved mapping of plant photosynthesis globally. However, unresolved issues related to the spatial, spectral, and temporal dynamics of vegetation fluorescence complicate our ability to interpret SIF measurements. We developed an instrument to measure leaf-level gas exchange simultaneously with pulse-amplitude modulation (PAM) and spectrally resolved fluorescence over the same field of view – allowing us to investigate the relationships between active and passive fluorescence with photosynthesis. Strongly correlated, slope-dependent relationships were observed between measured spectra across all wavelengths (Fλ, 670–850 nm) and PAM fluorescence parameters under a range of actinic light intensities (steady-state fluorescence yields, Ft) and saturation pulses (maximal fluorescence yields, Fm). Our results suggest that this method can accurately reproduce the full Chl emission spectra – capturing the spectral dynamics associated with changes in the yields of fluorescence, photochemical (ΦPSII), and nonphotochemical quenching (NPQ). We discuss how this method may establish a link between photosynthetic capacity and the mechanistic drivers of wavelength-specific fluorescence emission during changes in environmental conditions (light, temperature, humidity). Our emphasis is on future research directions linking spectral fluorescence to photosynthesis, ΦPSII, and NPQ.

Additional Information

© 2017 The Authors. © 2017 New Phytologist Trust. Version of record online: 30 June 2017; Manuscript Accepted: 14 May 2017; Manuscript Received: 2 February 2017. We thank Dr Joseph A. Berry for insightful suggestions on the instrumental setup and experiment design and three anonymous reviewers for their helpful insights. The research was supported by a NASA Postdoctoral Program fellowship award to T.S.M., California Institute of Technology startup funds to C.F., and the Keck Institute for Space Studies. The research was carried out, in part, at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. California Institute of Technology. Government sponsorship is acknowledged. Author contributions: T.S.M., C.F. and J.B.F. designed the research; T.S.M., C.F. and K.S. modified the original instrument; T.S.M., C.F., G.B.N. and T.S.D. performed the research; T.S.M. analyzed the data; T.S.M., C.F., J.B.F., Y.S., G.B.N., T.S.D., A.K. and K.S. contributed to interpretation of the analyses and writing the paper.

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August 21, 2023
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October 26, 2023