Question

In dicot root, which tissue becomes dead due to activity of phellogen?

• A. All tissue outside cortex
• B. Tissue outside hypodermis
• C. Tissue outside endodermis
• D. Tissue outside pericycle

Answer 1

The correct option is D Tissue outside pericycle

Pericycle is the outer most covering of stele, lying just beneath the endodermis. During secondary growth, the cells of pericycle present against protoxylem divide and form multiple layers of cells which are joined by cambial cells derived from conjunctive tissues and together they make a complete cambium ring. Cambial activity produces secondary tissues that push and rupture epidermal cell and outer cortex; a new protective layer, periderm is formed. Periderm divides to form cork cambium or phellogen. The cork cambium exhibit meristematic activity and produces cork or phellem towards the periphery and phelloderm on inside, i.e., extrastellar growth. These secondary tissues cause pressure and rupture the cells layers present outside the pericycle (endodermis and cortex)
A dicot root has tissues layers in following order: epidermis, cortex, endodermis, pericycle and vascular tissues, cork cambium activity rupture the cells layers present outside the pericycle. Hypodermis is the thickest layer of epidermis but is present in leaves not in roots
So, the correct answer is 'Tissue outside pericycle'