The wall-thickening material in tracheids and vessels are

Options

A. cuting and suberin
B. cellulose and cutin
C. suberin and cellulose
D. lignin and cellulose

Answer

To answer the question regarding the wall-thickening material in tracheids and vessels, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components**:
- Tracheids and vessels are types of water-conducting cells found in vascular plants.
- They have specialized cell walls that provide structural support and facilitate water transport.

2. **Identify the Materials**:
- The question asks for the wall-thickening materials specifically found in tracheids and vessels.
- Common materials that contribute to the thickening of cell walls in these structures include cellulose and lignin.

3. **Evaluate the Options**:
- **Option A**: Cutin and Suberin - These are found in the epidermis and cork cells, not in tracheids and vessels.
- **Option B**: Cellulose and Cutin - While cellulose is present, cutin is not found in tracheids and vessels.
- **Option C**: Suberin and Cellulose - Suberin is found in cork and endodermis, not in tracheids and vessels.
- **Option D**: Lignin and Cellulose - Both of these materials are indeed present in the walls of tracheids and vessels.

4. **Conclusion**:
- After evaluating all options, the correct answer is **Option D: Lignin and Cellulose**. These materials are responsible for the thickening of the walls in tracheids and vessels, providing them with strength and support.

### Final Answer:
The wall-thickening material in tracheids and vessels are **lignin and cellulose**.

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