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 that are responsible for the transport of nutrients, particularly sugars.

2. **Characteristics of Sieve Tubes**: At maturity, sieve tubes are composed of living cells that have thin cell walls. These cells are designed to facilitate the movement of substances.

3. **Maturity of Sieve Tubes**: When sieve tubes reach maturity, they undergo significant changes. One of the most notable changes is the loss of their nucleus. Although they remain alive, the absence of a nucleus is a key characteristic of mature sieve tubes.

4. **Role of Companion Cells**: Because sieve tubes lack nuclei, they rely on companion cells for their metabolic needs. Companion cells are adjacent to sieve tubes and provide essential functions, such as supplying proteins and ATP for the sieve tubes to function effectively.

5. **Identifying What Sieve Tubes Lack**: The question asks what sieve tubes do not possess at maturity. Based on the characteristics discussed, we conclude that sieve tubes do not possess a nucleus at maturity.

6. **Final Answer**: Therefore, the correct answer is that at maturity, sieve tubes do not possess a **nucleus**.