heart wood differs from sapwood in

Options

A. The absence of vessels and parenchyma
B. Having dead and non-conducting elements
C. Being susceptible to pests and pathogens
D. The presence of rays and fibers

Answer

### Step-by-Step Solution

1. **Understanding Heartwood and Sapwood**:
- Heartwood (also known as the central wood) is the innermost part of a tree trunk, while sapwood is the outer layer of the wood.
- Heartwood is typically darker and denser than sapwood.

2. **Composition**:
- Heartwood is composed of dead xylem vessels that have been filled with tyloses, which are outgrowths of parenchyma cells.
- It is rich in deposits of resins and tannins, which contribute to its darker color and durability.

3. **Functionality**:
- Heartwood is non-functional in terms of water conduction, as it consists of dead cells.
- In contrast, sapwood contains living xylem vessels that are functional and actively transport water and nutrients.

4. **Resistance to Pests**:
- Heartwood provides resistance to pests and pathogens due to the presence of chemical compounds like resins and tannins, which deter insects and fungi.
- Sapwood, being younger and more metabolically active, is more susceptible to pests and diseases.

5. **Conclusion**:
- The main differences between heartwood and sapwood are:
- Heartwood consists of dead xylem vessels, while sapwood has living vessels.
- Heartwood is resistant to pests and pathogens, whereas sapwood is more vulnerable.
- Heartwood is darker and denser due to the accumulation of secondary metabolites.

### Answer:
Heartwood differs from sapwood primarily in that it contains dead xylem vessels and is resistant to pests and pathogens, while sapwood contains living xylem vessels and is more susceptible to damage.