heartwood is absent even in very old trunk of

Options

A. Quercus and pinus
B. salix and morus
C. mangifera and Dalbergia
D. populus and salix.

Answer

To determine which plant species do not develop heartwood even in very old trunks, we can analyze the characteristics of the options provided.

### Step-by-Step Solution:

1. **Understanding Heartwood**: Heartwood is the dense inner part of a tree trunk, which is typically darker and provides structural support. It forms when the tree matures and the inner xylem becomes non-functional and is filled with various substances.

2. **Identifying the Options**: The options given are:
- Quercus and Pinus
- Selyx and Morax
- Magnifera and Delbergia
- Populus and Selyx

3. **Analyzing Quercus and Pinus**:
- Quercus (oak) is known for its hardwood characteristics. However, in the case of Pinus (pine), it has non-porous vessels and does not develop heartwood in the same way hardwoods do.
- The secondary xylem in Pinus is composed of tracheids and lacks vessels, which are essential for heartwood formation.

4. **Analyzing Other Options**:
- **Selyx and Morax**: These are not commonly referenced in terms of heartwood formation.
- **Magnifera and Delbergia**: Magnifera (mango) typically develops heartwood, and Delbergia (a type of legume) also forms heartwood.
- **Populus and Selyx**: Populus (poplar) does develop heartwood, while Selyx is less known.

5. **Conclusion**: Based on the analysis, Quercus and Pinus are the only combination where heartwood is absent even in very old trunks due to the characteristics of Pinus.

Thus, the correct answer is **Quercus and Pinus**.