Differentiation, Dedifferentiation and Redifferentiation: Practice Problems and FAQs

Let us do an activity. Take a tomato from your kitchen and separate the seeds from the fruit. Wash the seeds, plant them in one of the pots in your garden and water them. After a few days, you will observe small leaves coming out of the soil and soon, you will have fresh tomatoes from your garden to make a tangy soup.

Ever wondered how a small seed changes into a full grown plant? Meristematic cells are the actively dividing cells that contribute to the growth of plants. Meristematic cells are totipotent (can develop into any type of specialized cell) and remain undifferentiated (do not have any specific function). While some cells remain meristematic and contribute to the growth of plants, others differentiate and attain specific function.

List of Contents:

• Differentiation
• Dedifferentiation
• Redifferentiation
• Practice Problems of Differentiation
• FAQs of Differentiation

Differentiation

The process by which a cell loses its ability to divide and attains a specific function is known as differentiation. Meristematic cells differentiate to form permanent tissues.

Types of Permanent Tissue

There are two types of permanent tissues:

Simple Tissue

Tissues made up of only a single type of cell are called simple tissues. For example: Parenchyma, collenchyma, sclerenchyma.

Complex Tissue

Tissues made of more than one type of cell are called complex tissues. For example: Xylem, phloem

Changes that Occur During Differentiation

Let us consider the xylem tissue which is composed of tracheids, vessels, xylem parenchyma and xylem fibres. The tracheids and vessels together form the tracheary elements which help in the conduction of water and minerals. The tracheary elements remain alive during their developmental stage but become dead and hollow upon complete differentiation.

Do you know how these tracheary elements differentiate and develop from meristematic tissues? The meristematic cells undergo various changes while they differentiate into tracheary elements. Elongation of meristematic cells occurs in order to execute transportation of water.

Loss of protoplasm occurs in the cells. Cells develop very strong, elastic, lignocellulosic secondary cell walls in order to execute transport of water over distance under extreme water tension.

Dedifferentiation

The process by which a cell once again regains the ability to divide and lose the function it attained after differentiation is called dedifferentiation. For example: Formation of vascular cambium and cork cambium (meristems) from fully differentiated permanent tissues during secondary growth of a plant.

Cambium and Secondary Growth

Types of Cambium

Cambium can be classified into two types: Vascular cambium and cork cambium

Formation of Vascular Cambium

In the stem of a young dicot plant, vascular cambium is present in the form of patches in between the phloem tissue and the xylem tissue. A layer of cambium separating the xylem and the phloem is known as the intrafascicular cambium. Vascular bundles also consist of strips of parenchymatous cells known as medullary rays present radially.

Maturation of the dicot stem changes the cells of medullary rays adjoining the intrafascicular cambium to become meristematic and form interfascicular cambium.

Intrafascicular cambium and interfascicular cambium combined together form a cambial ring which regains the meristematic activity.

Once the cambial ring is formed, it cuts off on both sides. Growth of the cambial ring on the outer side results in formation of secondary phloem and its growth on the inner side results in formation of secondary xylem.

Redifferentiation

The process by which a dedifferentiated cell attains a particular function and loses its ability to divide again is called redifferentiation. For example: Formation of secondary xylem and phloem from dedifferentiated cells of the cambial ring.

Practice problems of Differentiation

Ques:- Which of the following statements correctly describes differentiation?

A. Process by which a dedifferentiated cell attains a particular function and loses its ability to divide again
B. Process by which a cell loses its ability to divide and attains a specific function
C. Process by which a cell once again regains the ability to divide and lose its functionality
D. None of the above

Solution: The process by which a cell loses its ability to divide and attains a specific function is known as differentiation. Meristematic cells differentiate to form permanent tissues. Hence the correct option is b.

Ques:- Redifferentiation is being shown by which of the following phenomena?

A. Formation of secondary xylem and phloem 
B. Formation of vascular cambium and cork cambium 
C. Formation of tracheary elements
D. None of the above

Solution: The process by which a dedifferentiated cell attains a particular function and loses its ability to divide again is called redifferentiation. For example: Formation of secondary xylem and phloem from dedifferentiated cells of the cambial ring.

Hence the correct option is a.

FAQs of Differentiation

Ques:- What is differentiation?

Solution: The process by which a cell loses its ability to divide and attains a specific function is known as differentiation. Meristematic cells differentiate to form permanent tissues.

Ques:- How are permanent tissues formed? What are the types of permanent tissues?

Solution: Meristematic cells are the actively dividing cells in a plant which are responsible for the plant growth. Meristematic cells differentiate to form permanent tissues which constitute cells with specific functions. Differentiation is a process by which a cell loses its ability to divide and attains a specific function. There are two types of permanent tissues:

• Simple tissue: Tissues made up of only a single type of cell are called simple tissues. For example: Parenchyma, collenchyma, sclerenchyma.
• Complex tissue: Tissues made of more than one type of cell are called complex tissues. For example: Xylem, phloem.

Ques:- What are the changes that occur in a meristematic cell during differentiation of tracheary elements?

Solution: The meristematic cells undergo various changes while they differentiate into tracheary elements. Elongation of meristematic cells occurs in order to execute transportation of water. Loss of protoplasm occurs in the cells. Cells develop very strong, elastic, lignocellulosic secondary cell walls in order to execute transport of water over distance under extreme water tension.

Ques:- How is dedifferentiation different from redifferentiation?

Solution: Dedifferentiation is a process by which a cell once again regains the ability to divide and lose the function it attained after differentiation while redifferentiation is a process by which a dedifferentiated cell attains a particular function and loses its ability to divide again.

Ques:- Mention one example of each of differentiation, dedifferentiation and redifferentiation.

Solution: Example of 

• Differentiation: Formation of tracheary elements.
• Dedifferentiation: Formation of vascular cambium and cork cambium (meristems) from fully differentiated meristems
• Redifferentiation: Formation of secondary xylem and phloem from dedifferentiated cells of the cambial ring.

Ques:- How does dedifferentiation occur? Explain with the help of an example.

Solution: Example of dedifferentiation is formation of vascular cambium and cork cambium (meristems) from fully differentiated meristems. In a young dicot plant, vascular cambium in the stem is present in the form of patches in between the phloem tissue and the xylem tissue. A layer of cambium separating the xylem and the phloem is known as the intrafascicular cambium. Vascular bundles also consist of strips of parenchymatous cells known as medullary rays present radially. As the dicot stem matures, the cells of medullary rays adjoining the intrafascicular cambium become meristematic and form interfascicular cambium. Intrafascicular cambium and interfascicular cambium combined together form a cambial ring which has regained the meristematic activity.

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