Problem 208 - Objective Biology for NEET

Question

Assertion: Secondary xylem is example of redifferentiated cells. Reason: Secondary xylem develops from dedifferentiated cells.

Step-by-Step Solution

Answer

Both the assertion and reason are correct and linked properly. Secondary xylem is indeed an example of redifferentiated cells because it develops from dedifferentiated cells of vascular cambium that redifferentiate into a more specialized form-functioning as secondary xylem.

Step 1: Understanding Terminology

Firstly, knowing the terms is crucial for solving the exercise. Secondary xylem is a plant tissue, specialized for water conduction and storage. 'Redifferentiated' cells refer to those cells that have returned from a less specialized state (dedifferentiated) to a more specialized state. 'Dedifferentiated' cells are those that were specialized but then lost their specialized characteristics to return to a less specialized state.

Step 2: Analyzing Assertion and Reason

Next, analyze the assertion and the reason given. The assertion states that secondary xylem is an example of redifferentiated cells. The reason is that secondary xylem develops from dedifferentiated cells. These two statements can now be evaluated against the understanding of these terms.

Step 3: Forming a conclusion

From the knowledge it's known that secondary xylem indeed develops from vascular cambium, which is a layer of cells that have a capacity to dedifferentiate and then redifferentiate into a more specialized form and function as secondary xylem. So, both assertion and reason are correct. Also, the reason correctly explains why the secondary xylem is considered a model of redifferentiated cells. Hence the assertions and reasonings are logically connected.

Key Concepts

Redifferentiation

Redifferentiation is a remarkable process observed in plant cells where cells that have lost their specialized function regain it. This typically occurs after a phase known as dedifferentiation, where the cell loses its specific characteristics. During redifferentiation, these cells transition back to a specific, functional role. Think of it as a cell that once was a teacher, then became a student again for a while, only to revert back to teaching once more.

• Redifferentiation is essential in forming secondary tissues in plants.
• The process allows the plant to adapt and grow new structures when required, such as secondary xylem.
• It helps in the repair of tissues and regeneration of parts like roots and stems.

Secondary xylem, found in woody plants, exemplifies this process. It originates from cells that have re-specialized to form a crucial part of the plant's circulatory system, effectively enabling water transport throughout the plant.

Dedifferentiation

Dedifferentiation is the initial stage where mature cells revert to a simpler, less specialized form. This gives them the flexibility to undergo further cellular changes, such as redifferentiation. Imagine it like rebooting your computer to make software updates possible.

• Dedifferentiation opens up possibilities for cells to adapt to new roles.
• It often results in a pool of cells capable of becoming different types of tissues.
• This process is seen in the recovery and healing of plant tissues after injury.

Vascular tissues like vascular cambium undergo dedifferentiation to form secondary xylem and other structures. By reverting to a less differentiated state, they can maintain a capacity for change and specialization as needed by the plant.

Vascular Cambium

The vascular cambium is a layer of meristematic tissue in plants that plays a pivotal role in secondary growth. Picture it as a continuously producing factory line, keeping the plant in good supply of essential structures.

• It's responsible for the production of secondary xylem and phloem.
• This cambium ensures the plant can grow in thickness, not just height.
• The cells in vascular cambium can undergo dedifferentiation and redifferentiation.

Functioning as the life force behind plant growth in girth, the vascular cambium is indispensable. It's crucial in forming wood and bark, tissues that allow the plant to distribute nutrients and water effectively as it thickens.