In a six year old stem, the oldest layer of secondary xylem is situated just

Options

A. outside the primary xylem
B. outside vascular cambium
C. on the inner side of cork cambium
D. on the inner side of vascular cambium.

Explanation

To answer the question, "In a six-year-old stem, the oldest layer of secondary xylem is situated just outside the primary xylem," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Secondary Growth**:
- Secondary growth occurs in plants, allowing them to increase in thickness. This is primarily facilitated by the vascular cambium, which produces secondary xylem and secondary phloem.

2. **Identifying Xylem Layers**:
- Xylem is a type of vascular tissue responsible for the conduction of water and minerals. In a stem, there are two types of xylem: primary xylem (formed during primary growth) and secondary xylem (formed during secondary growth).

3. **Location of Secondary Xylem**:
- The secondary xylem is formed outside the primary xylem. As the plant ages, more layers of secondary xylem are added each year. The newest layer of secondary xylem is closest to the vascular cambium, while the oldest layer is furthest away.

4. **Position of Oldest Layer**:
- In a six-year-old stem, the oldest layer of secondary xylem will be the layer that was formed first during the secondary growth process. This layer will be located just outside the primary xylem.

5. **Conclusion**:
- Therefore, in a six-year-old stem, the oldest layer of secondary xylem is situated just outside the primary xylem.

### Final Answer:
The oldest layer of secondary xylem in a six-year-old stem is situated just outside the primary xylem.

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