Which of the following parts of the plant is used as commercial wood ?

Options

A. Primary xylem
B. Primary phloem
C. Secondary xylem
D. Secondary phloem

Answer

To determine which part of the plant is used as commercial wood, we need to understand the structure and function of the different types of xylem and phloem present in the plant.

### Step-by-Step Solution:

1. **Identify the Types of Vascular Tissue**:
- The plant has two main types of vascular tissues: xylem and phloem. Xylem is responsible for the transport of water and minerals, while phloem transports sugars and nutrients.

2. **Differentiate Between Primary and Secondary Tissues**:
- Primary xylem and primary phloem are formed during the primary growth of the plant, which occurs at the tips of roots and shoots.
- Secondary xylem and secondary phloem are produced during secondary growth, which increases the thickness of the plant stem and roots.

3. **Understand the Role of Vascular Cambium**:
- The vascular cambium is a layer of meristematic tissue that produces secondary xylem (wood) towards the inside and secondary phloem towards the outside of the stem.

4. **Identify the Composition of Wood**:
- Wood is primarily composed of secondary xylem. As the plant grows, the vascular cambium continues to produce layers of secondary xylem, which accumulate over the years, forming the bulk of the wood.

5. **Conclusion**:
- Since wood is made up of secondary xylem, the part of the plant that is used as commercial wood is **secondary xylem**.

### Final Answer:
The part of the plant that is used as commercial wood is **secondary xylem**.

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