Phellogen

Phellogen

Phellogen, or suberofellodermic change or cork change, in botany, is a particular secondary meristematic tissue of spermatophytes. This tissue is part of the bark, which produces cork outward and phelloderm inward, both of the plant’s external protective tissues.
Phellogen or suberofellodermic cambium is a secondary meristem of the stem and roots of woody gymnosperm and angiosperm plants.
The fabrics produced by phellogen (cork or phelleme towards the outside of the stem and phelloderma towards the inside) serve to protect the internal parts of the tree: (book, gear and wood).

As an insulator, cork prevents exchanges with the outside and causes the death of all the tissues external to it (which become rind or rhytidoma, commonly called bark). Cork, phellogen and phelloderm together form the periderm. Phellogen can originate either from the cortical parenchyma (most frequent case) or even from the primary book; in any case it is a tissue made up of adult and already differentiated cells that de-differentiate and start dividing again, generating daughter cells that are very different from the parental ones.
It should be emphasized that in regions with a seasonal climate the activity of phellogen ceases during the winter period. With the arrival of summer, a new ring is formed within the already existing one, now dead.