Leaf scattering polarimetry and chlorophyll fluorescence

• Published in: Journal of quantitative spectroscopy & radiative transfer Vol. 242; p. 106760
• Main Author: Martin, W.E.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2020
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2019.106760

•Light from leaves contains both scattered light from the source and fluorescence from chlorophyll and helper molecules.•Spectropolarimetry using a white light source and movable narrow band filters can separate scattered light from fluorescent emissions.•Light from leaves illuminated with white light can contain ~15% polarised fluorescent light.•Stokes V scattering measurements contained ~20% circularly polarised fluorescence.•Previous reports of chiral light scattering from biological material are likely to have been significantly contaminated by the polarised fluorescence emissions of chlorophyll.•No evidence of direct chiral elastic scattering was seen. A number of spectropolarimetry measurements on leaves using white light and narrow band illumination have been reported in recent years because of interest in signatures for remote sensing of exoplanet life. Chlorophyll fluorescence occurs in white light illuminated experiments and is known to be polarised and so might contaminate surface scattering measurements. A displacing filter experiment was performed on the leaves of two common plants, Ficus benjamina and Chamaedorea elegans, to estimate the contribution of chlorophyll fluorescence in the spectropolarimetry of leaf scattering and transmission. Chlorophyll fluorescence is present as a measurable polarised component of up to 15% of scattered and transmitted light for the leaf samples. Other effects emerged which indicate that in vivo measurements on leaves are subject to the responsive nature of the leaves to changes in colour and intensity of the incident light.