A comprehensive treatment of light propagation through intact leaves based on the theories of radiative transfer and absorption statistics was used to calculate the theoretical absorption spectra of the chlorophyll-containing particles under conditions of multiple scattering and pigment spatial distribution equivalent to those in a leaf. These spectra were compared with the experimental in vivo spectra of leaves and in vitro spectra of chlorophyll-protein complexes extracted form these leaves. We conclude that the main discrepancies between the in vivo and in vitro spectra are apparently due to the optical artifacts specific for light propagation in leaves-multiple scattering and distributional error. Alterations of the pigment properties upon extraction significantly contribute to these discrepancies. The method has an estimated accuracy of about 10% and can be applied to derive the intrinsic optical properties of the photosynthetic mechanism in a leaf, as well as for the systematic study of their changes in the course of light adaptation.
Calculations of radiative transfer require knowledge of the absorption and scattering coefficients and the asymmetry factor of scattering in the medium. A method is presented for estimating these coefficients in living plant leaves from fiber-optic measurements. We consider the plant leaf as consisting of two layers of different refractive indices and with reflecting surfaces. Light intensities at the boundaries of these layers in several irradiated plant leaves have been measured using a thin (70-microm) glass fiber connected to a photomultiplier. The diffuse reflection and transmission were measured with an integrating sphere. From these values we derive an estimation of the scattering and absorption coefficients and the asymmetry factor of scattering applying an inversion of the multiflux theory of light propagation in turbid media. In addition, we compare these coefficients with those obtained by using the Kubelka-Munk theory.
Parameters of light propagation in plant leaves‐absorption and scattering coefficients, asymmetry of scattering‐have been estimated on the basis of measured transmission and remission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4‐flux radiative transfer‐a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiply scattering sample. Using the gained parameters, light flux gradients in a two‐layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two‐flux (Kubelka‐Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for two different plants.
Abstract— Parameters of light propagation in plant leaves—absorption and scattering coefficients, asymmetry of scattering—have been estimated on the basis of measured transmission and remission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4‐flux radiative transfer—a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiply scattering sample. Using the gained parameters, light flux gradients in a two‐layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two‐flux (Kubelka‐Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for two different plants.
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