Which of the following microelements is related to the synthesis of plant auxin (IAA) ?

Options

A. Molybdenum
B. Chlorine
C. Zinc
D. Boron

Answer

To solve the question regarding which microelement is related to the synthesis of plant auxin (IAA), follow these steps:

### Step-by-Step Solution:

1. **Identify the Question**: The question asks which microelement is involved in the synthesis of plant auxin, specifically indole acetic acid (IAA).

2. **Review the Options**: The options provided are:
- Molybdenum
- Chlorine
- Zinc
- Boron

3. **Understand the Role of Microelements**: Microelements are essential nutrients that play various roles in plant growth and development. Each of the options has different functions in plant physiology.

4. **Focus on Auxin Synthesis**: Auxins, particularly indole acetic acid (IAA), are crucial for plant growth, influencing cell elongation, root formation, and various developmental processes.

5. **Research the Functions of Each Option**:
- **Molybdenum**: Primarily involved in nitrogen fixation and enzyme functions.
- **Chlorine**: Mainly associated with osmosis and ionic balance in plants.
- **Zinc**: Plays a critical role in the synthesis of auxins and is essential for the activity of certain enzymes, including carbonic anhydrase.
- **Boron**: Important for cell wall formation and reproductive development.

6. **Identify the Correct Answer**: Based on the functions, zinc is specifically noted for its role in the biosynthesis of indole acetic acid. A deficiency in zinc can lead to auxin degradation, confirming its importance in auxin synthesis.

7. **Conclusion**: Therefore, the microelement related to the synthesis of plant auxin (IAA) is **Zinc**.

### Final Answer:
Zinc is the microelement related to the synthesis of plant auxin (IAA).

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