LIGNIN STRUCTURE IN BUXUS SEMPERVIRENS REACTION WOOD

The chemical structure of lignins in Buxus sempervirens wood samples s howing a progressive grading from normal wood to reaction wood was inv estigated by thioacidolysis. The mechanical states of the various samp les were assessed quantitatively by measuring the growth strains at th e stem surface. Sample woods with the more pronounced compression char acter showed the highest lignin contents. Buxus lignins are composed o f guaiacyl and syringyl units, similar to more evolved angiosperm lign ins. The proportion of syringyl units, together with that of labile in ter-unit ether bonds, was, however, lower in boxwood lignins than in p oplar or birch lignins. More importantly, lignins in boxwood samples w ith a pronounced compressed character were found to have structural si milarities with gymnosperm compression wood lignins, i.e. a higher con tent of carbon-carbon inter-unit bonds and of p-hydroxyphenyl units, c ompared with normal wood lignins. Copyright (C) 1996 Elsevier Science Ltd