Question

Which meristem helps in increasing the girth of the plant?

• A. Primary meristem
• B. Apical meristem
• C. Intercalary meristem
• D. Lateral meristem

Hint:

Distinguish between primary growth (length, by apical and intercalary meristems) and secondary growth (girth, by lateral meristems like cambium).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the type of meristematic tissue responsible for the increase in the diameter (girth) of a plant stem or root.

Step 3: Detailed Explanation:
Meristematic tissues are plant tissues where cells continuously divide to produce new cells. They are classified based on their position and function:
1. Apical meristem: Located at the tips of roots and shoots. Responsible for primary growth, which increases the length of the plant.
2. Intercalary meristem: Located at the base of internodes and leaves, particularly in monocots. Also responsible for primary growth (lengthening).
3. Lateral meristem: Consists of the vascular cambium and cork cambium. These meristems are responsible for secondary growth, which increases the girth or thickness (diameter) of the stem and root.
4. Primary meristem: A general term for meristems that contribute to primary growth (increase in length).
Therefore, lateral meristems are directly responsible for the increase in plant girth.

Step 4: Final Answer:
Lateral meristem helps in increasing the girth of the plant.

Answer 2

This question is about which meristem is responsible for a plant's increase in girth (thickness), so each option needs to be checked against what that particular meristem actually produces.

1. Primary meristem: This is really an umbrella term for the meristems descended directly from the embryo - the apical and intercalary meristems - and all of these produce primary growth, which lengthens the plant rather than thickening it.
2. Apical meristem: Found at the very tips of roots and shoots, this tissue adds new cells that extend the plant's length. It plays no role in making a stem or root wider.
3. Intercalary meristem: Located near the base of leaves and internodes, most often in grasses, this tissue also only lengthens the plant - it lets grass regrow quickly after being cut, but it does not add width.
4. Lateral meristem: This includes the vascular cambium and cork cambium, both of which run lengthwise along the sides of the stem or root. Cell division here adds new xylem and phloem inward and outward, which is exactly what increases the diameter, or girth, of the axis over time.

Only the lateral meristem produces the kind of growth that widens a stem or root rather than lengthening it.

Therefore, the correct answer is Lateral meristem.