HARITHA,Subject Matter Expert at Edumarz
Solution:Phellogen,phellem and phelloderm together form periderm.When dicot stems show secondary growth due to the activity of vascular cambium,the outer cortical and epidermis layers get replaced by new protective cell layers.After this meristematic tissue called cork cambium or phellogen forms in cortex region.Phellogen is formed of thick layered cells.It also cuts off cells present on both sides.The outer cells develop into cork or phellem and the inner cells develop into secondary cortex or phelloderm.The cork is not permeable to water due to presence of deposition of suberin in the cell wall.
Characters of dicot stem
It contains well developed epidermis with cuticle
Anatomy of dicot stem includes structures: epidermis,hypodermis,pericycle,vascular bundle and pith
Hypodermis is formed of collenchyma
Vascular bundles are seen as broken rings
Presence of well developed pith region
Presence of phloem parenchyma
Presence of trichomes
It also show secondary growth
It lacks bundle sheath on outer region of vascular bundle