LASER-INDUCED FLUORESCENCE (LIF) SPECTRA OF HERBACEOUS AND WOODY PRE-DIGESTED AND POST-DIGESTED PLANT-MATERIAL

Filtrate from pre- and post-digested plant material was exposed to 355 -nm pulsed laser light and the subsequent laser-induced fluorescence ( LIF) was recorded. Similarities and differences among spectra from 20 materials are discussed. Each material was replicated once, dried, gro und, and exposed to chloroform (CHCl3) for 24 h. The material represen ted aged (1 to 18 years old) plants from different herbaceous (grasses and forbs) and woody plant life forms. Mean peak fluorescence recorde d among materials differed (P < 0.0001) in both wavelength and peak am plitude (counts) across the spectral range (387 to 788 nm). Peak fluor escence was evaluated within each of three arbitrary color categories, blue near 455 nm and red near 674 nm, while only 16 of the materials produced a green peak near 528 nm. In general, the blue and green fluo rescence peaks were broad while the red peak was narrow. Mean peak cou nts were largest in the red range. Varying amounts of laser beam absor ption occurred among the materials evaluated due to different concentr ations of filtrate and different absorption efficiencies; therefore, a mplitude data (counts) were not used to determine statistical differen ces among materials. To overcome difficulties attributed to the raw co unt data, red/blue, red/green and blue/green count ratios within repli cates were calculated. Using all three count ratios in a multivariate analysis of variance, the 16 materials could be separated into nine di fferent (P < 0.05) material groupings. The LIF technique may provide a reliable means to separate ground pre- and post-digested plant materi als following further research into determining what fluorophores are producing the spectral signatures and how sample preparation affect pe ak wavelengths. (C) 1998 Elsevier Science B.V.