Fig. 4.

Cell wall development and gene expression in stems at 0, 2, 4 and 6 weeks (from left to right). a Lignification shown by Phloroglucinol–HCl staining (pink colour). Staining is localised in the protoxylem at the 0-week stage and maturing secondary xylem and phloem fibres. b–m Expression of IRX10 (b–e), IRX9 (f–i) and GUX1 (j–m) transcripts shown by the purple staining occurs mainly in protoxylem (px), developing secondary xylem, especially in xylem fibres (xf) and in newly formed phloem fibres (pf). Expression is generally absent from mature phloem fibres (mpf) at the 6-week stage (arrows). Also indicated are cambium (ca) and ray parenchyma (rp). n–q Localisation of xylan in cell walls of 0- to 6-week-old stems detected with the LM10 antibody. Bars 250 μm (a), 100 μm (b–q)