The specialised parenchyma cells closedly associated with sieve tube elements are
A. Having peripheral cytoplasm and large central vacuole but without nucleus.
B. Controls function of sieve tube elements
C. Absent in most monocots.
D. Connected by pit fields present between their common longitudinal walls.

Options

A. B & D are correct
B. A & D are correct
C. A & C are correct
D. B & C are correct

Answer

To solve the question regarding the specialized parenchyma cells closely associated with sieve tube elements, we need to analyze each of the provided statements carefully.

### Step-by-Step Solution:

1. **Identify the Specialized Cells**:
- The specialized parenchyma cells associated with sieve tube elements are known as **companion cells**. They play a crucial role in the functioning of sieve tubes.

2. **Evaluate Each Statement**:
- **Statement A**: "Having peripheral cytoplasm and large central vacuole but without nucleus."
- This statement is **true**. Sieve tube elements lack a nucleus and have a peripheral cytoplasm with large central vacuoles. The function of the sieve tube is controlled by the nucleus of the companion cells.

- **Statement B**: "Controls function of sieve tube elements."
- This statement is **false**. The function of sieve tube elements is controlled by the companion cells, not by the sieve tube elements themselves.

- **Statement C**: "Absent in most monocots."
- This statement is **false**. Companion cells are present in monocots, although the structure of phloem may vary.

- **Statement D**: "Connected by pit fields present between their common longitudinal walls."
- This statement is **true**. Companion cells and sieve tube elements are connected through pit fields in their common longitudinal walls.

3. **Summarize the True Statements**:
- From the evaluation, we find that statements A and D are true, while statements B and C are false.

4. **Select the Correct Option**:
- The correct answer is that the specialized parenchyma cells closely associated with sieve tube elements are described by statements A and D.

### Final Answer:
The correct option is **A and D are correct**.

---