Which of the following hormone is weak organic acid having unsaturated ring structures and derived from amino acid?

Options

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

Answer

To solve the question regarding which hormone is a weak organic acid with unsaturated ring structures and derived from an amino acid, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Characteristics of the Hormone**:
- The hormone in question must be a weak organic acid.
- It should have unsaturated ring structures.
- It must be derived from an amino acid.

2. **Recall Plant Hormones**:
- Familiarize yourself with the various plant hormones (phytohormones) such as auxins, gibberellins, cytokinins, ethylene, and abscisic acid.

3. **Focus on Auxin**:
- Among the plant hormones, auxin is known to be a weak organic acid.
- The most common form of auxin is Indole-3-acetic acid (IAA).

4. **Check the Structure of Auxin**:
- Indole-3-acetic acid (IAA) contains an unsaturated ring structure, specifically an indole ring.

5. **Determine the Source**:
- Auxin (IAA) is derived from the amino acid tryptophan, which acts as a precursor in its biosynthesis.

6. **Conclusion**:
- Based on the characteristics and the derivation from an amino acid, the hormone that fits all the criteria is auxin.

### Final Answer:
The hormone that is a weak organic acid having unsaturated ring structures and derived from an amino acid is **Auxin** (specifically Indole-3-acetic acid, IAA).

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