Horizontal growth of seedlings, swelling of axis and apical hook formation in dicot seedlings is brought about by

Options

A. Auxin
B. Gibberellins
C. Ethylene
D. Kinetin.

Answer

To solve the question regarding the horizontal growth of seedlings, swelling of the axis, and apical hook formation in dicot seedlings, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which hormone is responsible for the horizontal growth of seedlings, swelling of the axis, and apical hook formation in dicot seedlings.

2. **Analyzing the Options**:
- **Option A: Auxin**: Auxins are known for promoting cell elongation and are involved in various growth processes, but they primarily facilitate vertical growth rather than horizontal growth. Therefore, this option is not correct.

- **Option B: Gibberellins**: Gibberellins are important for seed germination and stem elongation, but they do not specifically contribute to horizontal growth or the formation of apical hooks. Thus, this option is also incorrect.

- **Option C: Ethylene**: Ethylene is a plant hormone that plays a significant role in various growth processes, including the horizontal growth of seedlings, swelling of the axis, and the formation of the apical hook in dicot seedlings. This option matches all the criteria mentioned in the question.

- **Option D: Kinetin**: Kinetin is a type of cytokinin that primarily promotes cell division and is not directly involved in the processes mentioned in the question. Therefore, this option is incorrect.

3. **Conclusion**: Based on the analysis of the options, the correct answer is **Option C: Ethylene**. Ethylene is responsible for the horizontal growth of seedlings, the swelling of the axis, and the formation of the apical hook in dicot seedlings.

### Final Answer:
The correct answer is **Ethylene**.

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