Secondary xylem produced outside of primary xylem

Vascular cambium has formed a cylinder

Parenchyma predominates in secondary xylem of storage roots

A transverse section of sugar beet (Beta vulgaris) root showing a vascular cylinder with secondary growth. Note the high proportion of living parenchyma cells with non-lignified walls in the secondary xylem. This is characteristic of a storage tissue, which is typically mostly parenchyma.

1 = primary xylem, 2 = secondary xylem, 3 = vascular cambium, 4 = secondary phloem, 5 = ray, 6 = vessel, 7 = cortex or proliferated pericycle