Which one of the following pairs is not correctly matched?

Options

A. Abscisic acid-Stomatal closure
B. Gibberellic acid-Leaf fall
C. Cytokinin-Cell division
D. IAA - Cell wall elongation

Answer

To determine which pair is not correctly matched, we will analyze each option provided in the question.

1. **Option A: Abscisic acid involved in stomatal closure**
- Abscisic acid (ABA) is a plant hormone that plays a crucial role in regulating water loss by promoting the closure of stomata during drought conditions. This match is correct.

2. **Option B: Gibberellic acid involved in leaf fall**
- Gibberellic acid (GA) is a plant hormone that promotes growth and is primarily involved in processes such as seed germination and stem elongation. It is not associated with leaf fall; instead, leaf fall is often regulated by other hormones such as ethylene. Therefore, this match is incorrect.

3. **Option C: Cytokinins involved in cell division**
- Cytokinins are indeed a class of plant hormones that promote cell division (cytokinesis) in plant tissues. This match is correct.

4. **Option D: Indole acetic acid (IAA) involved in cell wall elongation**
- Indole acetic acid (IAA) is a type of auxin that is known to promote cell elongation and is involved in the growth of plant cells. This match is also correct.

After analyzing all the options, we find that the incorrect match is:

**Option B: Gibberellic acid involved in leaf fall.**

### Summary of the Solution:
- Option A: Correct
- Option B: Incorrect (Gibberellic acid is not involved in leaf fall)
- Option C: Correct
- Option D: Correct

Thus, the answer to the question is **Option B**.