IAA mainly inhibits the growth of

Options

A. Root
B. Leaf
C. Shoot
D. Generally whole plant

Answer

To answer the question "IAA mainly inhibits the growth of," we will analyze the role of IAA (indole-3-acetic acid), which is a type of auxin in plants.

### Step-by-Step Solution:

1. **Understanding IAA**:
- IAA stands for indole-3-acetic acid, which is a naturally occurring plant hormone classified as an auxin. Auxins are known for their role in promoting plant growth.

**Hint**: Remember that IAA is a type of auxin, which is a growth-promoting hormone in plants.

2. **Role of Auxins**:
- Auxins, including IAA, are primarily involved in cell elongation, apical dominance, and the regulation of various growth processes in plants.

**Hint**: Think about how auxins influence different parts of the plant and their growth.

3. **Apical Dominance**:
- One of the key functions of IAA is to promote apical dominance, where the growth of the main shoot (apical bud) inhibits the growth of lateral buds. This means that when the apical bud is present, it suppresses the growth of shoots that would come from the sides.

**Hint**: Consider how the presence of the main shoot affects the growth of side shoots.

4. **Effect of IAA on Different Plant Parts**:
- While IAA promotes growth in certain areas, it mainly inhibits the growth of lateral shoots. This means that the growth of the shoot (the main stem) is favored over the growth of the roots or leaves.

**Hint**: Focus on which part of the plant is primarily affected by the presence of IAA.

5. **Conclusion**:
- Based on the understanding of IAA's role in promoting apical dominance, we can conclude that IAA mainly inhibits the growth of the shoot.

**Final Answer**: The correct option is **C: shoot**.

### Summary:
IAA mainly inhibits the growth of the shoot, promoting the dominance of the main stem over lateral shoots.