What is not true about auxin ?

Options

A. It is derived from mevalonic acid
B. It promotes cell division
C. It promotes stem elongation
D. It inhibits lateral growth

Answer

To determine which statement about auxin is not true, we will analyze each of the four statements provided.

### Step-by-Step Solution:

1. **Identify the Statements**: We have four statements regarding auxin:
- A) It is derived from mevalonic acid.
- B) It promotes cell division.
- C) It promotes stem elongation.
- D) It inhibits lateral growth.

2. **Evaluate Each Statement**:
- **Statement A**: "It is derived from mevalonic acid."
- This statement is **not true**. Auxin, particularly indole-3-acetic acid (IAA), is primarily derived from the amino acid tryptophan, not mevalonic acid.
- **Statement B**: "It promotes cell division."
- This statement is **true**. Auxin is known to stimulate cell division in certain plant tissues.
- **Statement C**: "It promotes stem elongation."
- This statement is **true**. Auxin is well-known for its role in promoting stem elongation by stimulating cell elongation.
- **Statement D**: "It inhibits lateral growth."
- This statement is **true**. Auxin can inhibit lateral (or axillary) bud growth, promoting apical dominance.

3. **Conclusion**: The statement that is not true about auxin is **A) It is derived from mevalonic acid**.

### Final Answer:
The statement that is not true about auxin is: **A) It is derived from mevalonic acid.**