High resolution measurements of solar induced chlorophyll fluorescence in the Fraunhofer oxigen bands

Year: 2017

Authors: Mazzoni M., Agati G., Cecchi G., Toci G., Mazzinghi P.

Autors Affiliation: IFAC, via Madonna del Piano, Sesto Fiorentino (Fi), 50019, Italy; INOA, Largo E. Fermi 650125 (Fi), Italy

Abstract: Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O2 absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.

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KeyWords: Chlorophyll; Image storage tubes; Plants (botany); Reflection; Stray light, Chlorophyll fluorescence; Fitting functions; High-resolution measurements; Laboratory experiments; Micro channel plate; Oxygen absorption bands; Reference spectrum; Reflectance functions, Fluorescence