Tyloses thickenings are seen in

Options

A. Phloem cells
B. Ray parenchyma only
C. Collenchyma
D. Ray parenchyma and xylem cells

Answer

**Step-by-Step Solution:**

1. **Understanding Tylosis**: Tylosis refers to the formation of a bag-like structure that occurs in the vessels of the xylem. It is a response to stress in the plant, often resulting from infection or damage.

2. **Function of Tylosis**: The primary function of tylosis is to prevent further damage to the plant by blocking the xylem vessels. When a plant is under stress, tylosis can form to create a dam-like structure that stops the flow of water and prevents the spread of pathogens.

3. **Identifying Where Tylosis Occurs**: Tylosis is specifically associated with xylem vessels. It is important to note that while tylosis can be found in parenchyma cells, it is not exclusive to them.

4. **Evaluating the Options**:
- **Option 1: Flow-in cells** - Incorrect, as tylosis is not present in these cells.
- **Option 2: Re-parenchyma only** - Incorrect, while tylosis is present in parenchyma, it is not limited to just these cells.
- **Option 3: Colenchyma** - Incorrect, as tylosis does not occur in colenchyma cells.
- **Option 4: Re-parenchyma and xylem cells** - Correct, as tylosis is indeed found in both parenchyma and xylem cells.

5. **Conclusion**: The correct answer to the question "Tyloses thickenings are seen in" is **Option 4: Re-parenchyma and xylem cells**.

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