Which of the following is involved in the synthesis of the plant hormone IAA and the vasoconstriction serotonin ?

Options

A. Tryptophan
B. Tyrosine
C. Phenylalamine
D. None of these

Answer

To solve the question regarding which amino acid is involved in the synthesis of the plant hormone IAA (Indole-3-acetic acid) and the vasoconstrictor serotonin, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Plant Hormone IAA**:
- IAA, also known as auxin, is a crucial plant hormone that regulates various aspects of plant growth and development.

2. **Determine the Amino Acid for IAA Synthesis**:
- The synthesis of IAA is primarily associated with the amino acid **Tryptophan**. Tryptophan is converted into IAA through various biochemical pathways in plants.

3. **Identify the Vasoconstrictor Serotonin**:
- Serotonin is a neurotransmitter that also acts as a vasoconstrictor in the body, influencing blood vessel constriction.

4. **Determine the Amino Acid for Serotonin Synthesis**:
- Tryptophan is also the precursor for serotonin. It is converted into serotonin through a series of enzymatic reactions.

5. **Evaluate the Options**:
- Given the options:
- **Tryptophan**: Correct, as it is involved in both IAA and serotonin synthesis.
- **Tyrosine**: Incorrect, as it is not involved in IAA synthesis.
- **Phenylalanine**: Incorrect, as it is not involved in IAA synthesis.
- **None of these**: Incorrect, since Tryptophan is the correct answer.

6. **Conclusion**:
- The correct answer is **Tryptophan**, as it is the amino acid involved in the synthesis of both the plant hormone IAA and the vasoconstrictor serotonin.

### Final Answer:
**Tryptophan**