Food Structure


The distribution of aromatic constituents, including lignin , in the leaf cell walls of "Coastal" hermudagrass (Cynodon dacrylon (L.) Pers.) was investigated using scanning ultraviolet (UV) microspectrophotometry. Leaf blade sections and individual tissue types were scanned at three wavelengths representing the absorbance maxima (318, 287 and 250 nm) of aromatic constituents present in bermudagrass leaves. The measured absorbance data were printed in a geometric arrangement to produce an image of the distribution and amount of aromatic constituents among and within cell wall types which vary in digestibility . Differences in absorbance were observed among cell wall types, among walls of the same cell type, and at different sites in individual cell walls. Scans of the mid vein at lOX magnification showed that various tissues and cells could be distinguished on the basis of U V absorbance. The abaxial sclerenchyma and mestome sheath gave the highest absorbance followed by those of the epidermis and parenchyma bundle sheath . The lowest levels of absorbance were observed in the mesophyll, parenchyma tissue and xylem tissue. Images produced from scanning individual cell walls at lOOx magnification showed the heterogeneous nature of aromatic constituents within a cell wall. Varying the wavelength resulted in similar but not identical images, indicating that variations in the chemical structures of aromatic constituents in the cell wall can he detected using this technique.

Included in

Food Science Commons