Leaf Reflectance vs. Leaf Chlorophyll and Carotenoid Concentrations for Eight Crops1

Abstract Leaf reflectance in the 0.40‐ to 0.75‐ μ m wavelength interval is influenced primarily by the pigments chlorophyll and carotenoid. However, the literature contains very few references to the relation between reflectance from leaves and their carotenoid content. Our objectives in this study were to determine which of three wavelengths in the visible spectral region best related leaf reflectance to total chlorophyll and carotenoid concentrations, and the relative effect of these pigments on reflectance. Hemispherical reflectances of single leaves at each of the 0.45‐, 0.55‐, and 0.67‐ μ m wavelengths for cantaloupe ( Cucumis melo L. cv. reticulatus Naud.), corn ( Zea mays L.), cotton ( Gossypium hirsutum L.), cucumber ( Cucumis sativus L.), head lettuce ( Lactuca sativa L. cv. capitata L.), grain sorghum ( Sorghum bicolor (L.) Moench), spinach ( Spinacia oleracea L.), and tobacco ( Nicotiana tabacum L.) were regressed on each crop's leaf total chlorophyll and carotenoid concentrations. The crops were grown in sand culture, and their leaf pigment concentrations were varied by supplying N at rates of 14, 28, 84, 140, and 196 ppm to a basic nutrient solution. Hemispherical reflectance of leaves was inversely related to each crop's leaf chlorophyll and carotenoid concentrations. However, of the three wavelengths tested, the 0.55‐ μ m wavelength seemed superior for individually relating the two pigments to leaf reflectance. The independent effects of carotenoid on hemispherical reflectance were small and generally not statistically significant, whereas the independent effects of chlorophyll while small were generally significant. The combined effects of these variables were highly significant and accounted for 39 to 95% of the reflectance variability. This study indicated that even though including carotenoid with total chlorophyll measurements improved the correlation of reflectance with pigment concentration, satisfactory results would be obtained by chlorophyll analysis alone.