Which tissue is not a result of re-differentiation ?

Question

Accepted Answer

The correct option is 2: Phellogen

The tissue that is *not* a result of re-differentiation is **Phellogen**, which is the cork cambium. This is because Phellogen itself is a classic example of a tissue formed by the process of **de-differentiation**. In plant growth, we study three main processes of cellular transformation. First, **differentiation** is when primary meristematic cells mature into permanent, specialized tissues like parenchyma. When these permanent cells (e.g., parenchyma cells of the cortex) lose their specialization and regain the power of division, that is **de-differentiation**, which gives rise to a secondary meristem. Phellogen is a secondary meristem that arises this way to perform secondary growth. Finally, the daughter cells of this newly formed secondary meristem (Phellogen) once again mature and specialize into permanent tissues, and this final step is termed **re-differentiation**. Therefore, Phellogen is the meristematic source formed by de-differentiation, while its resulting tissues are products of re-differentiation.

The incorrect option is 1: Cork

Cork, or phellem, is a protective, permanent tissue that is produced by the Phellogen (cork cambium) towards the outside of the stem or root. The cells of the Phellogen divide and the outer daughter cells mature, become suberized, and die, forming the Cork. Since the Cork is a specialized, mature tissue derived from a secondary meristem (Phellogen), its formation is a result of the process of **re-differentiation**. This makes Option 1 an incorrect choice for the question, as it is indeed a product of re-differentiation.

The incorrect option is 3: Secondary cortex

The Secondary Cortex, also known as the phelloderm, is a parenchymatous, permanent tissue that is produced by the Phellogen (cork cambium) towards the inside of the stem or root. The cells of the Phellogen divide and the inner daughter cells mature and remain living, forming the Secondary Cortex. Like cork, the Secondary Cortex is a final, differentiated tissue derived from a secondary meristem (Phellogen). Its maturation and specialization from the secondary meristematic cells classifies its formation as **re-differentiation**.

The incorrect option is 4: Secondary xylem

The Secondary Xylem is a major component of wood, which forms the inner part of the secondary vascular tissue in a plant stem or root. It is produced by the lateral meristem known as the vascular cambium, which is another type of secondary meristem. The cells of the vascular cambium divide, and the inner derivatives mature and differentiate to become the water-conducting Secondary Xylem. Since the Secondary Xylem is a permanent, specialized tissue formed from a secondary meristem, its development is a direct result of the process of **re-differentiation**.