Which of the following is essential for indole acetic acid (IAA)?

Options

A. zinc
B. copper
C. boron
D. molybdenum

Answer

To solve the question "Which of the following is essential for indole acetic acid (IAA)?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which micronutrient is essential for the synthesis or function of indole acetic acid (IAA), a plant hormone.

2. **Identify the Options**: The options provided are:
- Zinc
- Copper
- Boron
- Molybdenum

3. **Research Micronutrient Functions**: We need to recall the functions of these micronutrients in relation to IAA:
- **Zinc**: Known to be essential for various enzymatic activities, including those involved in the biosynthesis of hormones like IAA.
- **Copper**: Plays a role in several enzymatic reactions but is not specifically linked to IAA.
- **Boron**: Important for cell wall formation and reproductive development but not directly linked to IAA.
- **Molybdenum**: Involved in nitrogen fixation and enzyme functions but not specifically in IAA synthesis.

4. **Link Zinc to IAA**: It is established that zinc is crucial for the activity of carbonic anhydrase, which is important for the biosynthesis of auxins, including IAA. Zinc also activates carboxylase and dehydrogenase enzymes, which are vital for the metabolic pathways involving IAA.

5. **Conclusion**: Based on the above analysis, we conclude that zinc is essential for indole acetic acid (IAA).

### Final Answer:
**Zinc** is essential for indole acetic acid (IAA).

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