The plate description of a typical, thin, compact plant leaf, introduced previously, has been generalized to the noncompact case and applied to experimental data including average reflectance and transmittance measurements on 200 mature, field-cotton leaves. A compact leaf has few and a noncompact leaf has many intercellular air spaces in the mesophyll. No statistically significant difference was found between the average leaf thickness and the mean effective water thickness of the leaves. The Kubelka–Munk scattering coefficient s for a typical leaf, measured at the 1-μ spectral region, is approximated by the relation s = r/t, where r and t, respectively, are the reflectance and transmittance of the leaf. The approximate equality of r and t, noted by previous investigators, is explained on the basis of the scattering of diffuse light within the leaf by critical internal reflections. Predictions from the plate (P) model for cotton leaves compare favorably with those of the Kubelka–Munk (K–M) and Melamed (M) theories. Applied to vegetation, all three theories predict a characteristic linear dimension related to the cellular structure of the leaf.
© 1970 Optical Society of America
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