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United States Department of Agriculture

Agricultural Research Service

Title: Ftir Microspectroscopic Imaging of Flax (Linum Usitatissimum L.) Stems

Authors
item Himmelsbach, David
item Khalili, Sadia - SWEDISH UNIV DEPT FOREST
item Akin, Danny

Submitted to: Molecular and Cellular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 3, 1997
Publication Date: N/A

Interpretive Summary: Due to the increased worldwide interest in natural fibers for textiles and industrial purposes, there is renewed interest in flax as a source of fiber. With this interest has come the need to improve the quality assessment and the processing methods used to produce flax fiber. This need has generated a requirement for better knowledge about the chemistry and structure of this plant tissue. This study reveals that infrared microscopic imaging can be used to provide that knowledge. It was found that each of the major components of flax tissue generated specific vibrations indicative of their presence. By selecting for these specific vibrations, the location and relative amounts of these components could be determined. This permitted the generation of maps that indicated the position and concentration of: lipids, pectins, cellulose, aromatics and non-cellulosic carbohydrates in flax stem tissue. This single method was thus able to provide a general assessment of the chemical nature of each tissue type present in flax stems. These results provide both a means of assessing the quality of raw plant material and a basis on which new processing methods can be evaluated. Specifically, it will permit the determination of the effects of applying certain chemicals and/or enzymes to raw flax to most efficiently access the fibers. This will permit the generation of the best quality of fiber for each intended purpose.

Technical Abstract: Fourier-transform infrared (FTIR) microspectroscopy was used to image and subsequently produce maps of the distribution of chemical components in flax (Linum usitatissimum L.) stem tissue. Dried cross-sections of two flax cultivars, Ariane and Natasja, were examined between BaF*2 windows and mapped over the spectral region of 4000-850 cm*-1 in the transmission mode. .The infrared maps were keyed to the visible images of the samples, thus permitting the imposition of chemical composition onto anatomical structure. Area maps of the tissue showed the location of the major components of flax by frequency selection for specific functional groups. The frequencies were selected based on the potential of a band to indicate that component to the exclusion of others in the matrix, by comparison of the spectra of "pure" components. Waxes or lipids were best indicated by a sharp shoulder at 2850 cm*-1 and appeared primarily in the cuticular and epidermal tissues of both cultivars and some within the fibers of Natasja flax. Pectins gave a band ca. 1615 cm*-1 for the Ca*2+ salt form that was detected in tissue on both sides of the fiber bundles of Natasja flax but mostly on the exterior side of Ariane flax bundles. Cellulose was the strongest contributor to the band located at ca. 1335 cm*-1 that showed its greatest intensity in the fiber cells with lower intensity displayed in the core tissue. Aromatic compounds were indicated most readily by the band at 1510 cm*-1 and were located primarily in the core tissue and to a lesser extent in cuticular and epidermal tissue of both cultivars. Acetyl groups, likely associated with hemicellulosic non-cellulosic polysaccharides, were indicated by a band centered at 1250 cm*-1 and found within the fibers of both samples of flax and in the core tissue of Natasja flax.

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