Question

Explain in 2-3 lines each of the following terms with the help of examples taken from different plant tissues.

a.Differentiation

b.De-differentiation

c.Redifferentiation

Answer 1

a. Differentiation

The process by which actively dividing meristematic cells undergo structural and functional specialisation to form permanent tissues is called differentiation.



Example:

The formation of tracheary elements (tracheids and vessels) of xylem takes place from the meristematic cells in the following manner:-

• Elongation of cells: This is a major structural change to perform its function of water transport.
• Loss of protoplasm: The cells lose their protoplasm. In other words, they slowly become dead to create enough space for water transport.
• Development of lignocellulosic secondary cell walls: A very strong, elastic cell wall with lignin deposition is formed to carry water to long distances even under extreme tension.

b. De-differentiation

The process by which specialised permanent tissues that had lost their ability to divide, regain the ability to divide is called dedifferentiation.

Example:

Dedifferentiation is noticed when the medullary rays (strips of parenchyma cells adjacent to intrafascicular cambium) become meristematic. This is called interfascicular cambium.

Formation of the cambial ring: The intra and interfascicular cambium are meristematic and form the cambial ring.




c. Redifferentiation

This process during which dedifferentiated meristematic cells lose their meristematic activity and again gain specialisation is called redifferentiation.

Example:

The parenchymatous cells which had gained meristematic activity forming interfascicular cambium and cork cambium through the process of dedifferentiation, again lose their meristematic activity and give rise to the secondary phloem, secondary xylem, secondary cortex, cork, etc.