Fig. 4.

Scanning electron microscopy analysis of stem tissues in Populus trichocarpa ptrcesa4, ptrcesa7a/b and ptrcesa8a/b mutants (CesA, cellulose synthase). (a) Scanning electron microscopy (SEM) images of cross‐sections of basal stems from 6‐month‐old wild‐type (WT) and ptrcesa mutant trees. (b) Xylem fibres, vessels, and ray cells within inset boxes in the (a) and secondary and primary phloem fibres (SPF and PPF) in the WT and these mutants were magnified under SEM. Some mature wood fibres (indicated by pentangles) have developed the thick G‐layers inside the secondary cell walls (SCWs). Xylem‐I, developing xylem; Xylem‐II, mature xylem; V, vessel cell; F, fibre cell; R, ray cell. Bars: (a) 250 μm; (b) 20 μm.