Which one of the following phytohormone is formed in response to the unfavourable environmental conditions

Options

A. Abscisic acid
B. Ethylene
C. `GA_(3)`
D. Indole acetic acid

Answer

To answer the question "Which one of the following phytohormone is formed in response to the unfavorable environmental conditions?", we can follow these steps:

### Step-by-Step Solution:

1. **Identify Unfavorable Environmental Conditions**:
- Unfavorable environmental conditions can include drought, waterlogging, high temperatures, and high light intensity. These conditions create stress for plants.

2. **Understand Plant Responses to Stress**:
- Plants have developed mechanisms to respond to these stress conditions. One of the key responses involves the production of specific phytohormones.

3. **Recognize the Role of Phytohormones**:
- Phytohormones are chemical messengers that regulate various physiological processes in plants. Different hormones are produced in response to specific environmental stresses.

4. **Identify the Relevant Phytohormone**:
- Among the various phytohormones, abscisic acid (ABA) is known as the "stress hormone." It is produced in response to unfavorable conditions such as drought and helps the plant cope with stress.

5. **Explain the Function of Abscisic Acid**:
- Abscisic acid causes stomatal closure to reduce water loss through transpiration. It also stimulates the abscission of leaves and flowers when necessary, helping the plant conserve resources during stressful periods.

6. **Conclusion**:
- Based on the above points, the correct answer to the question is **abscisic acid**, as it is the phytohormone formed in response to unfavorable environmental conditions.

### Final Answer:
The phytohormone formed in response to unfavorable environmental conditions is **abscisic acid**.

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