FT-IR microspectroscopic imaging of flax (Linum usitatissimum L.) stems

Fourier transform infrared (FT-IR) microspectroscopy was used to image and subsequently produce maps of the distribution chemical components in flax stem tissue. Cross-sections of two flax cultivars, Ariane and Natasja, were examined. The infrared maps produced were keyed to the visible images of the samples, thus permitting superimposition of chemical composition onto anatomical structure. The functional group frequencies utilized to produce chemical maps were based on their diagnostic capability for indicating each component to the exclusion of others in the matrix, by comparison of the spectra of "pure" components. Waxes were best indicated by a sharp shoulder at 2850 cm(-1) and appeared primarily in the cuticular and epidermal tissues. Pectins gave a band ca. 1615 cm(-1) for the Ca2+ salt form that was primarily detected in tissue surrounding the fiber bundles. Cellulose was the strongest contributor to the band located at ca. 1335 cm(-1) that showed its greatest intensity in the fiber cells. Aromatic compounds were indicated most readily by the band at 1510 cm(-1) and were located primarily in the core tissue. Acetyl groups, likely associated with hemicellulosic polysaccharides, were indicated by a band centered at 1250 cm(-1) and found within the fibers and core tissue.