PARENT SESSION
Poster Session 3: GIS and Remote Sensing.
Monday, August 2 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Thermal infrared spectroscopy of plant leaves: A tool for species identification.
Ribeiro da Luz, Beatriz*,1, Crowley, James2, 1 University of Sao Paulo, Sao Paulo, Brazil2 U.S. Geological Survey, Reston, VA
ABSTRACT- Thermal infrared (TIR; 2.5-14 
m) attenuated total reflectance (ATR) spectra were measured from green leaves of over 200 plant species. The work is part of a project to define linkages between TIR spectral properties and plant cuticle compositions, and to explore the utility of TIR spectral measurements for ecological research. The ATR measurements of individual leaves were made by using a Nicolet FTIR spectrometer and ATR accessory with a ZnSe crystal. The ATR interaction involves a thin (∼1-5 m) surface layer, and thus, is restricted to the outermost epicuticular substances. Variability in the ATR spectra of different plant species is associated with differing amounts of major organic constituents such as alkanes, alcohols, acids, and esters. Some species also display absorption features in the 8-14 mm wavelength region related to amorphous silica. Most of the species examined in this study produced distinctive ATR spectra. To evaluate the use of the ATR measurements as a species identification tool, spectra of 51 individuals belonging to 14 different species were analyzed as "unknowns" against a spectral library containing ATR spectra of 200 species. The search procedure correctly identified 46 of the 51 individuals. This application requires awareness of several additional sources of spectral variability, including changes in cuticular wax composition with leaf age and incident illumination intensity. ATR measurements are simple to make and both field and laboratory ATR equipment is available. We suggest that ATR spectral measurements could have utility for ecological studies that require detailed field surveys of plant species composition.
Key words: plant leaves, spectroscopy