Fig. 5.

FLA11 regulates stem fibre development. Toluidine blue O‐stained transverse sections, taken 1 cm from the base of stems of Arabidopsis wild‐type (WT) (a–c) and OE‐FLA11 1TC (one transgene copy) (d–f) plants at growth stage 6.9 (Boyes et al., 2001), show increased stem diameter in OE‐FLA11 1TC compared to WT. Images of vascular tissues showed that phloem fibre (PhF) cells had secondary cell walls (SCWs) in WT stems (b) but not OE‐FLA11 1TC stems (e). Higher‐magnification images of interfascicular fibre (IF) tissues showed more layers of IF from secondary growth (sIF) and the existence of IF cambial (IFC) cells in OE‐FLA11 1TC stems (f) compared to WT (c). (g–j) Transverse stem sections imaged by transmission‐electron microscopy (TEM) showed increased thickness of SCWs in IF of OE‐FLA11 1TC base stems (i, j) compared to WT (g, h). SCWs in IF of WT (h) have three discernible layers, S1, S2, and S3, whereas OE‐FLA11 1TC IFs showed multiple internal layers (ILs) (j). (k) IF wall thickness, quantified from stage 6.9 base stems. (l) IF length, quantified from base stems at growth stage 6.9. Data shown are average values ± SD (n = 2 plants from two independent transformed lines). Asterisks indicate a significant difference compared to WT plants according to Student’s t‐test (*, P < 0.05). Co, cortex; Ep, epidermis; Ph, phloem; Xy, xylem. Bars: (a, d) 100 µm; (b, c, e, f) 20 µm; (g, i) 5 µm; (h, j) 1 µm.