Question

Which meristem helps in increasing the girth of the plant? ____.

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

Hint:

Remember the directions of growth: - Apical & Intercalary = Vertical growth (Up and Down Length). - Lateral = Horizontal growth (Sideways Girth).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Meristematic tissues are classified based on their position in the plant body into apical, intercalary, and lateral meristems, each serving a distinct growth role.

Step 2: Detailed Explanation:

• Lateral Meristem: These meristems occur in the mature regions of roots and shoots and run parallel to the long axis of the plant organ. They divide periclinally to produce secondary tissues, which directly increases the girth (thickness/diameter) of the plant. Examples include vascular cambium and cork cambium.
• Apical Meristem: Found at the tips of roots and shoots; helps in increasing the length of the plant (primary growth).
• Intercalary Meristem: Found between mature tissues (e.g., at the base of leaves or internodes in grasses); helps regenerate parts removed by grazing herbivores.

Step 3: Final Answer:
The lateral meristem helps in increasing the girth of the plant.

Answer 2

Girth refers to how thick or wide a plant's stem or root is, which is different from how tall or long it grows. Matching each meristem type to the direction of growth it produces will identify the one responsible for increasing girth.

1. Primary meristem: This is a broad category referring to meristems that contribute to a plant's primary growth (its initial elongation), rather than a distinct positional type on its own, so it does not specifically answer what causes thickening.
2. Apical meristem: Located at root and shoot tips, apical meristems drive primary growth, which increases the length of roots and shoots, not their thickness.
3. Intercalary meristem: Found at the base of leaves or internodes, especially in grasses, this meristem allows regrowth after grazing or mowing by adding length between existing tissues, again a lengthwise effect rather than a widening one.
4. Lateral meristem: Positioned parallel to the sides of stems and roots (for example, vascular cambium and cork cambium), lateral meristems divide to add new layers of tissue around the existing girth, directly increasing the diameter of the plant organ. This is what produces secondary growth (thickening).

Since only one of these meristem types adds tissue in a direction that widens the stem or root rather than lengthening it, that is the one responsible for increasing girth.

Therefore, the correct answer is Lateral meristem.