The phyohormone which induces triple respone is

Options

A. IAA
B. ABA
C. `GA_(3)`
D. `C_(2)H_(4)`.

Answer

To solve the question regarding which phytohormone induces the triple response, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the phytohormone that induces the triple response in plants. The triple response is a growth pattern that occurs in seedlings when they encounter mechanical stress.

2. **Identify the Options**: The options provided are:
- IAA (Indole-3-acetic acid)
- ABA (Abscisic acid)
- GA3 (Gibberellic acid)
- C2H4 (Ethylene)

3. **Research the Functions of Each Hormone**:
- **IAA**: This is a type of auxin that primarily promotes cell elongation and is involved in various growth processes.
- **ABA**: Abscisic acid is known for its role in stress responses, particularly in drought conditions, and it generally inhibits growth.
- **GA3**: Gibberellic acid promotes stem elongation, seed germination, and flowering but does not induce the triple response.
- **C2H4 (Ethylene)**: Ethylene is a gaseous hormone that regulates various aspects of plant growth and development, including the triple response during mechanical stress.

4. **Determine the Correct Answer**: The triple response, characterized by stem elongation, thickening, and horizontal growth, is specifically induced by ethylene (C2H4) when a seedling encounters mechanical stress.

5. **Conclude the Answer**: Therefore, the phytohormone that induces the triple response is **C2H4 (Ethylene)**.

### Final Answer:
The phytohormone which induces the triple response is **C2H4 (Ethylene)**.

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