Question

7. Explain the process by which cells and tissues are produced by the vascular cambium and cork cambium. Be specific as to the initials (including fusiform and ray initials) and their derivatives

Answer 1

The growth can be primary (Increase in height) or secondary ( increase in girth). The dicots have secondary growth but monocots do not. The secondary growth is the work of lateral meristem. There are two types of lateral tissues in plants (Cambria), that are vascular Cambria and the cork Cambria.
Vascular Cambria produces secondary phloem and xylem and is responsible for the concentric rings in the trees. The active Cambria ring of vascular Cambria differentiates into new cells towards middle and periphery regions. The middle layers mature into secondary xylem whereas the peripheral cells mature into the secondary phloem. There are two types of vascular Cambria: Fusiform initials and Ray initials. Fusiform cells are tall and axially oriented. The Ray initials are smaller , round to angular isodiametric cells. Ray initials mostly produce phloem and xylem parenchyma.
Cork Cambria (aka Phellogen) essentially replaces the soft meristem with hard woody cork. It differentiates into the outer cortex (phellum), inner cortex (phelloderm). This also gives rise to Lenticels for the exchange of gases.