The Chlorophyll Fluorescence Ratio F735/F700 as an Accurate Measure of the Chlorophyll Content in Plants

A remote sensing technique is presented to estimate the Major, 1988). The relationship F685/F735 vs. Chl was expressed by a power function F685/F735 mChl2n. For difchlorophyll content in higher plants. The ratio between chlorophyll fluorescence at 735 nm and in the range 700– ferent plant species, the coefficients m and n were different, but the common features of the relationships were 710 nm, F735/F700 was found to be linearly proportional to the chlorophyll content (with determination coeffii) high sensitivity of the ratio to low to medium Chl content (from near zero to about 100–150 mg m22—slightly cient, r2, more than 0.95), and, thus, this ratio can be used as a precise indicator of chlorophyll content in plant green and yellowish-green leaves); and ii) the ratio F685/ F735 leveled off at moderate to high Chl content and its leaves. This new chlorophyll fluorescence ratio indicates chlorophyll levels with high precisionthe error in chlosensitivity to Chl.200 mg m22 was fairly low. Chlorophyll fluorescence depends to a great extent rophyll prediction over a wide range of chlorophyll content (from 41 to 675 mg m22) was less than 40 mg m22. on pigment content and the absorption of leaves (e.g., Buschmann and Lichtenthaler, 1988; Guyot and Major, The technique was tested and validated in three plant species: beech (Fagus sylvatica L.), elm (Ulmus minor 1988; Dahn et al., 1992). In green leaves, about 90% of Miller), and wild vine (Parthenocissus tricuspidata L.). the emitted Chl fluorescence at 685 nm is reabsorbed by Elsevier Science Inc., 1999 the Chl of the leaf (Gitelson et al., 1998). Recently, the effect of reabsorption of the Chl fluorescence was quantitatively estimated (Dahn et al., 1992; Gunther et al., INTRODUCTION 1994; Agati et al., 1993; 1995; Gitelson et al., 1998). It was found that the effect of reabsorption of the red Chl The ratio of fluorescence (F) measured at 685 nm and fluorescence at 685 nm is particularly large when leaves 735 nm, F685/F735, was successfully used to determine the possess a moderate to high Chl content. In order to dechlorophyll (Chl) content in leaves (e.g., Lichtenthaler termine why the sensitivity of the ratio F685/F735 to mod1987a; Lichtenthaler and Buschmann, 1987; Guyot and erate to high Chl content is low and in which spectral bands fluorescence is more sensitive to Chl content, absorption and reflectance spectra of the leaves have to be *Remote Sensing Laboratory, J. Blaustein Institute for Desert Research and Department of Geological and Environmental Sciences, studied together with emitted fluorescence. Ben-Gurion University of the Negev, Sede Boker Campus, Israel It was recently found that reflectance in the range †Botanisches Institut II, University of Karlsruhe, Karlsruhe, near 700 nm is consistently dependent on Chl content Germany and is almost equally sensitive to Chl content throughout Address correspondence to Anatoly A. Gitelson, Remote Sensing Lab., J. Blaustein Inst. for Desert Research, Ben-Gurion Univ. of the a wide range of its variation (Gitelson and Merzlyak, Negev, Sede-Boker Campus, 84990 Israel. E-mail: gitelson@bgumail. 1994; 1996; 1997). It would be expected that the use of bgu.ac.il Received 8 October 1998; revised 17 January 1999. fluorescence in the range near 700 nm, located farther