Mature sieve tubes do not have nucleus but they are living and metabolically active . The cell which is associated with sieve tube is :

Options

A. Companion cell
B. Phloem parenchyma
C. Transfer cells
D. Transfusion tissue

Answer

**Step-by-Step Solution:**

1. **Understanding Sieve Tubes**: Mature sieve tubes are specialized cells in the phloem of flowering plants that are responsible for the transport of carbohydrates. They are unique because they lack a nucleus but are still considered living and metabolically active.

2. **Identifying Associated Cells**: To understand which cells are associated with sieve tubes, we need to look at the structure and function of cells in the phloem. The options provided include companion cells, phloem parenchyma, transfer cells, and transfusion tissue.

3. **Role of Companion Cells**: Companion cells are closely associated with sieve tube members. They play a crucial role in the functioning of sieve tubes by providing metabolic support. Companion cells have a well-developed nucleus and dense protoplast, which allows them to carry out necessary metabolic activities.

4. **Developmental Origin**: Both sieve tube members and companion cells originate from a common mother cell during the process of cell division. The phloem mother cell undergoes longitudinal division, resulting in two daughter cells of unequal size. The smaller daughter cell becomes the companion cell, while the larger one develops into the sieve tube member.

5. **Conclusion**: Given that companion cells are structurally and functionally associated with sieve tubes and provide the necessary support for their metabolic activities, the correct answer to the question is that the cell associated with sieve tubes is the **companion cell**.

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