In plant anatomy, the 'Periderm' is a secondary protective tissue that replaces the epidermis in stems and roots undergoing secondary growth. It consists of three main layers: the phellem, phellogen, and phelloderm. The 'phellem' is also known as: MCQ with Answer and Explanation

The periderm is the outer protective covering of stems and roots that have undergone secondary growth (thickening), replacing the primary epidermis. It is composed of three distinct layers: 1) Phellem (cork): The outermost layer, consisting of dead, compactly arranged cells with suberized (waterproof) walls that provide protection and prevent water loss. 2) Phellogen (cork cambium): The middle, meristematic layer that produces phellem outwards and phelloderm inwards. 3) Phelloderm (secondary cortex): The innermost layer, consisting of living, parenchymatous cells.