ANALYSIS OF REFLECTANCE AND FLUORESCENCE-SPECTRA FOR ATYPICAL FEATURES - FLUORESCENCE IN THE YELLOW-GREEN

An experiment designed to search for remotely detectable, identifying features of anthropogenic contaminants by remote sensing of vegetation is described. Reflectance and fluorescence measurements are made from single leaves, still attached to the plant. In order to maximize the opportunity for detection and identification of possibly subtle spectr a features, all optical measurements are made under controlled conditi ons. Reflectance is measured using diffuse illumination and a well-def ined illumination and viewing geometry over a wide range of wavelength s (0.35-2.5 mu m). Fluorescence spectra are measured from live leaves at over 30 excitation wavelengths. Analysis procedures are designed to facilitate sorting through large amounts of data and allow interactiv e manipulation of the spectral data sets. Reflectance of single leaves from soybean plants subjected to water stress differed little from re flectance of the leaves from control plants. (This may not be indicati ve of canopy reflectance.) Blue and red fluorescence was somewhat grea ter for the water stressed plants. Unusual fluorescence features in th e yellow-green part of the spectrum were also found in both control an d the stressed plants. These features were exceptionally sensitive to stress.