Spectral Ratio of Reflectance for Estimating Chlorophyll Content of Leaf

Abstract

This study was made to find an index for estimating chlorophyll content (Ch1) of a leaf by means of reflected light with rice, wheat and barley leaves. Two well-discriminating wavebands were defined from hemispherical reflectance (ρ) spectra of the leaves; one is Ch1-dependent visible band (V, 500-650 nm) and another Ch1-independent near infrared band (IR, above 750 nm). When the wavelengths 800 and 550 nm were chosen for IR and V bands, respectively, the highest correlation with Ch1 per unit leaf area (Ch1/LA) was found in either difference (ρ800 − ρ550) or ratio (ρ800/ρ550) of reflectances. The correlation with Ch1/LA was generally higher in the ratios than in the differences of reflectances and the coefficients were almost constant in the ratios when the wavelengths 530 to 630 nm were used for V band. The ratios of ρ800/ρ550 also had a very close correlation with the readings of a chlorophyllometer. These facts clearly demonstrate that the ratio of hemispherical reflectance in the wavelengths above 750 nm to that of 530–630 nm may be the most reliable index to estimate Ch1/LA of a leaf for at least the three gramineous crops. © 1985, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.