Which of the following is not a physiological effect of auxin?

Options

A. Initiates rooting in stem cuttings.
B. Promotes flowering
C. Prevente fruit and leaf drop at early stages
D. Promotes bolting

Answer

To determine which of the following options is not a physiological effect of auxin, we will analyze each option based on the known functions of auxin in plants.

1. **Understanding Auxin**: Auxin is a plant hormone that plays a crucial role in various growth and developmental processes in plants. It is known for its role in promoting cell elongation, apical dominance, and other physiological effects.

2. **Analyzing Each Option**:
- **Option A: Initiate rooting in stem cutting**: Auxin is known to promote root formation in cuttings. This is a well-documented effect of auxin, making this option a physiological effect of auxin.
- **Option B: Promote flowering**: Auxin can influence flowering by increasing the production of ethylene, which is involved in the flowering process. Therefore, this option is also a physiological effect of auxin.
- **Option C: Prevent fruit and leaves from falling at an early stage**: Auxin helps in delaying the abscission (falling off) of fruits and leaves, thus preventing early drop. This is another physiological effect of auxin.
- **Option D: Promote bolting**: Bolting refers to the rapid growth of a flowering stalk, which is primarily influenced by other hormones like gibberellins rather than auxin. Therefore, this option is not a physiological effect of auxin.

3. **Conclusion**: Based on the analysis, the option that is not a physiological effect of auxin is **Option D: Promote bolting**.

### Step-by-Step Solution Summary:
1. **Identify the hormone**: Auxin is a plant hormone involved in growth and development.
2. **Evaluate each option**:
- A: Initiates rooting → Yes, auxin does this.
- B: Promotes flowering → Yes, auxin influences flowering.
- C: Prevents early fruit/leaf drop → Yes, auxin helps in this.
- D: Promotes bolting → No, this is not a function of auxin.
3. **Select the correct answer**: The correct answer is **Option D**.