<Original>Studies on Hemicelluloses in Tension Wood : I. Chemical Composition of Tension, Opposite and Side Woods of Japanese Beech (Fagus crenata Blume)

Abstract

Three different types of woods, tension, opposite and side woods, were isolated from Fagus crenata Blume and their anatomical and chemical properties were compared. Tension wood was composed of well developed gelatinous fibers and was characteristic in its low lignin and pentosan contents as well as its high ash, alpha-cellulose and uronic acid contents. Carbohydrate portion of tension wood has been found to be peculiar in that tension wood contains the highest amount of galactose in contrast to the lowest amount of mannose among three types of wood. Each wood was further subjected to sequential fractional extractions. The peculiarity of the chemical composition of the tension wood reflected the differences in the carbohydrate compositions of the extracted hemicelluloses. In analysing the molecular weight distribution of the extracted hemicelluloses by gel nitration on Sepharose 4B, it has been found that all components included in the gel matrices have quite similar molecular weights in spite of the differences in the carbohydrate compositions. These results may give a clue in ellucidation of the distribution and function of hemicelluloses in wood.