Describe the contribution of cork cambium in secondary growth.

(N/A) $\rightarrow$ As the stem increases in girth due to the activity of the vascular cambium,the outer cortical and epidermal layers break and need to be replaced to provide new protective cell layers. Consequently,a meristematic tissue called cork cambium or phellogen develops in the cortex region.
$\rightarrow$ Phellogen is a couple of layers thick and consists of narrow,thin-walled,and nearly rectangular cells. Phellogen cuts off cells on both sides.
$\rightarrow$ The outer cells differentiate into cork or phellem,while the inner cells differentiate into secondary cortex or phelloderm.
$\rightarrow$ The cork is impervious to water due to suberin deposition in the cell walls.
$\rightarrow$ The cells of the secondary cortex are parenchymatous.
$\rightarrow$ Phellogen,phellem,and phelloderm are collectively known as periderm.
$\rightarrow$ Due to the activity of the cork cambium,pressure builds up on the remaining layers peripheral to the phellogen,and ultimately these layers die and slough off.
$\rightarrow$ Bark: Bark is a non-technical term that refers to all tissues exterior to the vascular cambium,including secondary phloem.
$\rightarrow$ Early and Late Bark: Bark refers to a number of tissue types,namely periderm and secondary phloem. Bark formed early in the season is called early or soft bark. Towards the end of the season,late or hard bark is formed.
$\rightarrow$ Lenticels: In certain regions,the phellogen cuts off closely arranged parenchymatous cells on the outer side instead of cork cells. These parenchymatous cells soon rupture the epidermis,forming a lens-shaped opening called lenticels.