Knots in stems are formed due to

Options

A. Bacterial infection of wounds
B. Injury caused by wounds
C. Outgrowth of secondary tissues caused by falling of branches
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the formation of knots in stems. Knots are typically associated with the areas where branches were once attached to the main stem.

2. **Identifying the Options**: The options provided are:
- A) Bacterial infections of wounds
- B) Injury caused by wounds
- C) Outgrowth of secondary tissue caused by falling of branches
- D) None of these

3. **Analyzing the Options**:
- **Option A**: Bacterial infections of wounds do not directly lead to the formation of knots. Instead, they can cause decay or disease in the plant.
- **Option B**: Injury caused by wounds may lead to some healing processes, but it does not specifically explain the formation of knots.
- **Option C**: Outgrowth of secondary tissue caused by falling of branches is a plausible explanation. When a branch falls, it creates a wound that triggers a response in the stem, leading to the formation of knots.
- **Option D**: This option suggests that none of the previous answers are correct, which is not the case here.

4. **Conclusion**: The correct answer is **Option C**: Outgrowth of secondary tissue caused by falling of branches. This process involves rapid cell division at the site of the wound, leading to the formation of knots.

5. **Explanation of the Process**: When a branch falls, it creates a wound in the stem. The cells around this wound undergo rapid division to heal the area. However, the healing is not complete, and the resulting tissue forms a knot. This knot consists of a mass of undifferentiated cells, which may eventually be covered by cork tissue, leading to the characteristic knot structure.