CELLULAR-DISTRIBUTION OF GUAIACYL AND SYRINGYL LIGNINS WITHIN AN ANNUAL RING IN OAK WOOD

To clarify the relationship between cell position within an annual rin g and composition of guaiacyl and syringyl lignins, UV (ultraviolet) a bsorption spectra were measured for almost all cells in the section co ntained in one annual ring of mizunara (Japanese oak, Quercus mongolic a Fischer var. grosseserrata Rehd. et Wils.). Transverse sections cont ain cells of various diameters, which can he supposed to include long and narrow fusiform cells which are cut at various positions from the tip ends to the other ends. Thus the relationships between cell diamet ers and lambda max of UV absorption spectra were examined, As a result , it was clarified that the tips of cells were rich in syringyl lignin compared with the bodies (middle parts) of the cells, and it was sugg ested that guaiacyl and syringyl lignins were distributed heterogeneou sly in the axial direction of one long fusiform cell, The relationship s between distances from vessel elements and lignin compositions were examined on the bodies of fusiform cells. Consequently, the proportion of cells rich in syringyl lignin tended to increase at the location m ost distant from vessel elements. Scanning electron microscopy of pit structures on the fractured surfaces suggested that the cell types ten ded to change gradually from vasicentric tracheids to libriform wood f ibers via fiber-tracheids as the distance from vessel elements increas ed. Thus it was suggested that the proportions of syringyl lignins ten ded to increase as cell functions changed from water conduction to mec hanical support.