Thickness variation of the G-layer along a mature and a differentiating tension wood fiber in Populus euramericana

Abstract

The thickness variation of the secondary wall layers along a mature tension wood fiber was examined, using serial transverse sections, and that of the gelatinous layer along a differentiating fiber was also studied. In a mature gelatinous fiber the G-layer was the thickest in the central region of the fiber and decreased in thickness toward the tips. The thickness of the S2 layer also decreased from the center toward the tips, whereas the S1 layer showed a uniform thickness throughout the fiber length. From the observations of some differentiating fibers it was concluded that the G-layer possesses a uniform thickness along the length of a fiber at the earliest stage of G-layer formation and that the more the fiber develops, the greater is the reduction in thickness of the G-layer from the center of the fiber toward the tips. The thickening process of secondary wall layers is discussed.