Estimation of leaf chlorophyll content with polarization measurements: Degree of linear polarization

Leaf chlorophyll content (LCC) is an important indicator of plant physiological status, photosynthetic capacity, plant stress and senescence. Optical reflection measurements offer a nondestructive method for estimating LCC and have been widely used in plant science and ecological applications. Light reflected from leaves surfaces can be described by photometric and polarimetric measurements. In this study, previously introduced spectral indices based on photometric measurements did not yield highly accurate estimates of LCC using multi-angular measurement in the forward scattering directions. Subsequently, an index derived from photometric measurements, the bidirectional reflectance factor (BRF), and some previously introduced spectral indices based on the degree of linear polarization (DOLP) were used to estimate LCC. We found that a newly proposed spectral index based on BRF and 1/DOLP allowed the convenient estimation of LCC with a high accuracy, explaining more than 90% of LCC variation. The method, which relates LCC to the BRF and 1/DOLP of leaves using multi-angular measurements, indicates that both photometric and polarimetric properties are effective for LCC estimation. This study opens the possibility for estimating LCC based on polarization reflected from leaves. One advantage of using polarization to remotely sense leaf biochemical parameter is that DOLP measurements do not need to be normalized by a reference panel as BRF measurements. (C) 2019 Elsevier Ltd. All rights reserved.