Variation of Microfibril Angle Within Individual Tracheids

Utilizing the orientation of soft-rot cavities, microfibril angles were measured in individual tracheids (pulped fibers) and thin sections of southern pine in order to determine the extent of variation. Within individual tracheids of southern pine, microfibril angles were consistent along the length of a tracheid and when measured between bordered pits. Microfibril angles were highly variable on the radial walls containing bordered pits. Microfibril angles approached 90° around bordered pits, but the angles on the walls opposite the bordered pits were consistent with the average angle along the length of the tracheid. Variation (standard deviation) was less in latewood tracheids than in earlywood tracheids. Within individual tracheids, there was no correlation between microfibril angle and tracheid width. Across an annual ring of southern pine, microfibril angle gradually decreased through the earlywood and became much smaller in the latewood