Vascular cambium is a meristematic layer that cuts off

Options

A. Primary xylem and primary pholem
B. Xylem vessels and xylem tracheids
C. Primary xylem and secondary xylem
D. Secondary xylem, secondary pholem and medullary rays

Answer

### Step-by-Step Solution:

1. **Understanding Vascular Cambium**:
- Vascular cambium is a type of meristematic tissue found in plants. It is responsible for the secondary growth of stems and roots by producing secondary xylem (wood) and secondary phloem (bark).

2. **Formation of Vascular Cambium**:
- The vascular cambium is formed from two types of cambium: the inter-fascicular cambium (located between vascular bundles) and the intra-fascicular cambium (located within vascular bundles). Together, they form a complete ring of vascular cambium.

3. **Function of Vascular Cambium**:
- The cells of the vascular cambium are meristematic, meaning they can continuously divide. When these cells divide, they produce two types of daughter cells:
- **Inward Division**: The daughter cells that are produced towards the pith (the center of the stem) differentiate into secondary xylem.
- **Outward Division**: The daughter cells that are produced towards the cortex (the outer layer of the stem) differentiate into secondary phloem.

4. **Formation of Medullary Rays**:
- The cells that are squeezed out between the secondary xylem and secondary phloem are known as medullary rays. These are also derived from the meristematic cells of the vascular cambium.

5. **Evaluating the Options**:
- Now, we evaluate the provided options:
- **Option A**: Primary xylem and primary phloem - Incorrect.
- **Option B**: Xylem vessels and xylem tracheids - Incorrect.
- **Option C**: Primary xylem and secondary xylem - Incorrect.
- **Option D**: Secondary xylem and secondary phloem - Correct, as these are the products of the vascular cambium's activity.

### Final Answer:
The correct answer is **secondary xylem and secondary phloem**.

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