The cell functionally associated with sieve tube is -

Options

A. Phloem fibres
B. Phloem parenchyma
C. Companion cell
D. Collenchyma

Answer

To solve the question "The cell functionally associated with sieve tube is -", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of Phloem**:
- Phloem is a type of vascular tissue in plants responsible for the transport of nutrients, particularly sugars produced through photosynthesis.

2. **Identify the Components of Phloem**:
- The main components of phloem include sieve tube elements, companion cells, phloem fibers, and phloem parenchyma.

3. **Focus on Sieve Tube Elements**:
- Sieve tube elements are specialized cells that facilitate the transport of sugars and other metabolic products.

4. **Determine the Role of Companion Cells**:
- Companion cells are closely associated with sieve tube elements. They are responsible for providing metabolic support to the sieve tubes, which lack a nucleus and some organelles at maturity.

5. **Connection Between Companion Cells and Sieve Tubes**:
- Companion cells are connected to sieve tube elements through structures called plasmodesmata, which allow for the transfer of nutrients and signaling molecules.

6. **Evaluate Other Options**:
- Phloem fibers and phloem parenchyma, while part of the phloem, do not have a direct functional association with sieve tube elements.
- Collenchyma is not a component of phloem at all.

7. **Conclusion**:
- Based on the functional association and support provided, the correct answer is **companion cell**.

### Final Answer:
The cell functionally associated with sieve tube is **companion cell**.