Name a principal naturally occurring auxin present in plants.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Auxins**: Auxins are a type of plant hormone, also known as phytohormones, that play a crucial role in regulating plant growth and development.

2. **Functions of Auxins**: These hormones are primarily responsible for promoting cell elongation and growth, particularly in the stems and roots of plants.

3. **Identifying Naturally Occurring Auxin**: The question specifically asks for a principal naturally occurring auxin. The most well-known and widely studied naturally occurring auxin is Indole-3-acetic acid (IAA).

4. **Conclusion**: Therefore, the principal naturally occurring auxin present in plants is Indole-3-acetic acid (IAA).

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