The contribution of chlorophyll fluorescence to the reflectance spectra of green vegetation

Green vegetation has a relatively low reflectance in the red region (670 nm to 700 nm) due to strong absorption of chlorophyll a. Fluorescence of green vegetation has strong emission peaks at 685 nm and 740 nm. The red-NIR region (670 nm to 760 nm) has been widely used in remote sensing applications without considering the effects of chlorophyll fluorescence. It is vital to understand the contribution of chlorophyll fluorescence to the red-NIR region of the reflectance spectra. These investigation were conducted to determine the contribution of fluorescence to the reflectance of green vegetation. Measurements necessary for the determination the effects of fluorescence were made using soybeans grown at different nitrogen levels in order to obtain a range of reflectance and fluorescence spectra. The contribution of chlorophyll a fluorescence to reflectance in the red-NIR region is significant, and found to be as great as 23% of the reflectance at 685 nm and 4% at 740 nm. There is no significant contribution of fluorescence to the “red edge shift”