Ultrastructural behavior of cell wall polysaccharides

Studies on the behavior of wood polysaccharides inside and outside the cell wall were carried out under varying conditions using the electron microscope in combination with physico-chemical methods to gain new information on the super- molecular structure of the polysaccharides. Several fractions containing different polyoses were obtained by fractionation of the alkali extract of holocellulose. Isolated polyoses are at least partially able to arrange themselves in fibrillar elements. After delignification, the cellulose is recognizable within the cell wall as microfibrils with an average diameter of about 250 À. However, these fibrillar units seem to be rather unstable as they can easily be split into units 120 À in diameter by chemical treatment. After partial hydrolysis, isolated cellulose shows more subunits about 30 A in diameter at higher magnification. Moreover, the more sensitive portions of the fibrils in the longitudinal direction are attacked by partial hydrolysis, and these portions seem to grow with increasing duration of the hydrolysis. Fractionation of cellulose isolated from thermally treated wood shows that the chain fragments are multiples about 300 À in length, A tentative model of the supermolecular arrangement of the cellulose in relation to the other cell wall components is presented.