Although the color phase (hue) of plants plays fundamental roles in quality of foods and horticultural species, principles of variations in hues of plant materials are neither fully understood nor extensively examined by researchers. This may be partly because plant colors are determined by complex physicochemical factors non-understandable to most biologists. For example, hue of soluble pigment has been demonstrated to change at different thickness of a layer or pigment concentrations in exceptional substances such as pumpkin seed oil. Such strange effect (dichromatism) of layer thickness on pigment hue was previously explained by application of Beer-Lambert law on absorbance spectra (Naturwissenschaften 2007;94:935-939). In this report, we demonstrate dichromatism in plant leaves and red spices. Dichromatism of these materials can be quite simply observed by extraction and dilution of pigments with dimethylformamide, a scarcely evaporating organic solvent. Hue of pigment solutions gradually changed with dilution from green to yellow-green for leaves, and from red to yellow for spices. These changes were also explained by changes in absorbance spectra with dilution, nevertheless spectra of absorption coefficient were stable. Dichromatism in leaves caused uniform negative correlation between lightness and hue in any plant species examined. Such correlation was successfully explained by calculation with a normalized RGB color matching function. (c) 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 605-611, 2015
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