At maturity, sieve tubes do not possess –

Options

A. Cell wall
B. Nucleus
C. Cytoplasm
D. Vacuoles

Answer

**Step-by-Step Solution:**

1. **Understanding Sieve Tubes**: Sieve tubes are specialized structures in the phloem of flowering plants responsible for the transport of nutrients, particularly carbohydrates like sucrose.

2. **Maturity of Sieve Tubes**: At maturity, sieve tubes undergo significant changes. They lose certain cellular components to facilitate their function in nutrient transport.

3. **Identifying Absent Components**: The question asks which component is absent in mature sieve tubes. The options provided are cell wall, nucleus, cytoplasm, or vacuoles.

4. **Analyzing Each Option**:
- **Cell Wall**: Sieve tubes do have a cell wall, although it may be modified.
- **Nucleus**: Mature sieve tubes do not possess a nucleus. This is crucial for their function as they rely on companion cells for metabolic support.
- **Cytoplasm**: Sieve tubes retain some cytoplasm, although it is less than in typical cells.
- **Vacuoles**: Mature sieve tubes may have vacuoles, but they are not a defining feature that is absent.

5. **Conclusion**: The component that is definitively absent in mature sieve tubes is the nucleus.

6. **Final Answer**: Therefore, the correct answer is **Nucleus**.

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