Formation of interfascicular cambium from fully developed parenchyma cells is an example for

The correct answer is Dedifferentiation.

To understand why this is the case, let's break down the processes of plant cell development:
1. Differentiation: This is the process where cells derived from root apical and shoot apical meristems, as well as cambium, undergo structural and functional changes to mature into specific cell types (e.g., parenchyma cells, collenchyma cells, or tracheary elements) that perform dedicated functions. During differentiation, cells lose their ability to divide.
2. Dedifferentiation: Under certain conditions, fully differentiated (mature) living parenchyma cells that have lost the capacity to divide can regain the power of division. This phenomenon of reverting back from a mature state to a meristematic state is known as dedifferentiation. The formation of the interfascicular cambium and cork cambium from fully developed parenchyma cells of medullary rays and cortex is a classic example of this process.
3. Redifferentiation: The new cells produced by the dedifferentiated meristems (such as the interfascicular cambium) lose their capacity to divide once again and mature to perform specific functions. This second loss of division ability is called redifferentiation (e.g., formation of secondary xylem and secondary phloem).
4. Maturation: This is a general term describing the final stages of cell differentiation, where a cell attains its final structure and functional capability.

Since the formation of interfascicular cambium involves fully developed, mature parenchyma cells regaining their ability to divide to form a secondary meristem, it is a clear example of dedifferentiation.