High resulution measurements of solar induced clorophyll fluorescence in the Fraunhofer oxygen band

Spectra of solar radiance reflected by leaves close tothe Fraunhofer bands show the net contribution ofchlorophyll fluorescence emission which adds to thereflected solar spectra. In a laboratory experiment, alow stray light, high resolution, 0.85 m doublemonochromator was used to filter radiation livingleaves still attached to the plant in correspondence ofthe 687 nm and 760 nm O2 absorption bands.Reference spectra from a non fluorescent whitereference were also acquired. Acquisition wasperformed by a Microchannel plate (MCP) intensifieddiode array with 512 elements. A fit of the spectraldata outside the absorption lines allowed to retrieve thespectral base-line as a function of wavelength for thereference panel and the leaf. Reflectance functionswere determined extending the Plascyck equationsystem [1] to all the resolved lines of the oxygenabsorption bands and using the base-lines for thecontinuum values. Fluorescence was deduced from thesame equation system, using both the measured leafand reference radiance spectra and the leaf reflectancefitting function.