Phytohormone which inhibits flowering in serveral plants but stimulates flowering in Pineapple plants is .

Options

A. 2-4 D
B. IBA
C. `GA_(3)`
D. Ethylene

Answer

### Step-by-Step Solution:

1. **Understanding Phytohormones**: Phytohormones are chemical substances produced in plants that regulate growth and development. Different phytohormones have different effects on flowering and other processes.

2. **Identifying the Phytohormone in Question**: The question asks for a phytohormone that inhibits flowering in several plants but stimulates flowering in pineapple plants.

3. **Analyzing Ethylene**: Ethylene is a well-known phytohormone. It is primarily known for its role in inhibiting flowering in many plants. For example, it inhibits the formation of female flowers in cucumber plants.

4. **Ethylene's Unique Role in Pineapple**: Interestingly, ethylene has a unique role in pineapple plants. While it inhibits flowering in many other plants, it actually stimulates flowering in pineapple. This dual role makes ethylene a significant hormone in plant development.

5. **Eliminating Other Options**:
- **Gibberellins**: While gibberellins can promote flowering in some plants, they do not have the specific role described in the question regarding pineapple.
- **Auxins (2,4-D and IBA)**: 2,4-D is a synthetic auxin used as a herbicide and does not influence flowering. IBA (Indole Butyric Acid) is a natural auxin that promotes root development and apical dominance but does not play a role in flowering.

6. **Conclusion**: Based on the analysis, the correct answer to the question is ethylene. It inhibits flowering in several plants but stimulates flowering in pineapple plants.

### Final Answer:
The phytohormone which inhibits flowering in several plants but stimulates flowering in pineapple plants is **ethylene**.

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