A comparison of latewood pits, fibril orientation, and shrinkage of normal and compression wood of giant sequoia

Abstract

Giant sequoia latewood compression wood (CW) tracheids had pit canals that flared toward the lumen with extended poorly defined inner apertures that paralleled the fibrils in the S2 walls. Boiling and drying of CW and normal wood (NW) blocks induced split extensions at the CW pit aperture grooves but not at the NW pit apertures. These split extensions of the CW pit apertures were present also in longitudinal microsections. The mean fibril angle of 21 to 25 degrees of this well-defined CW was appreciably below the 45 degrees frequently reported. The CW tangential/radial shrinkage ratio of about 1 was distinetly lower than NW (1.6 and 2.1), and appeared to be the result of much lower tangential shrinkage. Both NW and CW specimens when dried quickly in an oven at 100° C had higher shrinkage (long., tang. and rad.) than when air-dried first at lower temperature and higher relative humidity.