Fig. 2.

Secondary growth and natural variation of secondary growth in Arabidopsis thaliana. (A) Schematic illustration of the anatomy of the primary and secondary stem. Note that the primary stem shows several discrete vascular bundles composed of phloem (yellow), xylem (blue) and cambium (red), while the secondary stem carries closed cylinders of phloem (yellow), xylem (blue) and cambium (red). (B and C) Examples of natural variation in secondary growth in Arabidopsis thaliana. B shows a cross-section collected immediately above the uppermost rosette leaf of the main stem of the Pla-1 accession. (C) shows a cross-section of the main stem of the Rou-0 accession collected at the same position. Note that Pla-1 displays more IC-derived cells (ICD) than Rou-0 (indicated by red brackets). Both accessions were harvested when the height of the main stem was 20 cm. Asterisks indicate the position of primary vascular bundles.