Which of the following auxin is widely used as weedicide?

Options

A. IAA
B. IBA
C. 2, 4-D
D. NAA

Answer

To answer the question "Which of the following auxin is widely used as weedicide?", we will analyze the given options and their uses.

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for the specific auxin that is commonly used as a weedicide. A weedicide is a substance that kills unwanted plants (weeds).

2. **Identify the Options**: The options provided are:
- IAA (Indole-3-acetic acid)
- IBA (Indole-3-butyric acid)
- 2,4-D (2,4-Dichlorophenoxyacetic acid)
- NAA (Naphthalene acetic acid)

3. **Analyze Each Option**:
- **IAA (Indole-3-acetic acid)**: This is a natural auxin that promotes plant growth but is not primarily used as a weedicide. It helps in cell elongation and division.
- **IBA (Indole-3-butyric acid)**: This auxin is mainly used for promoting root formation in plants, not as a weedicide.
- **2,4-D (2,4-Dichlorophenoxyacetic acid)**: This is a synthetic auxin that is widely used as a weedicide, particularly effective against broad-leaved plants. It increases respiration rates in plants, leading to their death.
- **NAA (Naphthalene acetic acid)**: Similar to IAA and IBA, NAA is used for rooting and plant growth regulation, not as a weedicide.

4. **Conclusion**: Based on the analysis, the auxin that is widely used as a weedicide is **2,4-D**.

### Final Answer:
The correct answer is **2,4-D (2,4-Dichlorophenoxyacetic acid)**.

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