Fig. 6

Scanning electron micrographs of TW fibres and G-layers from Salix Tora stem cross sections. Control (a, b, e, f, i, j, m, n) and after 2- (d) and 3-day treatment with cellulase (Cellic CTec2) (c, g, h, k, l, o, p). Top row (a–d) from 40 cm height of the stem, row 2 (e–h) from 200 cm and rows 3 and 4 (i–p) from 360 cm height. The G-layer varied in thickness between different growth rings and between early- and latewood being recognized as an extra layer lining the secondary cell wall (arrowheads, b, f, j, m). The G-layer was hydrolyzed after 3-day cellulase treatment (c, g, h, k, l, o, p). Morphological changes of the secondary cell walls and the compound middle lamellae between fibres, vessels and parenchyma cells and storage materials [e.g., starch granules, n. (S)] through enzyme treatment were not apparent. Occasional fibrous remnants of the G-layer were observed on sections treated for shorter periods (d, arrowheads). Enzyme treatment caused removal of the G-layers