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 will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding Sieve Tube Elements**:
- Sieve tube elements are part of the phloem in vascular plants and are responsible for the transport of nutrients, especially sugars. They are living cells that lack a nucleus at maturity.

**Hint**: Remember that sieve tubes are involved in the transport of food in plants.

2. **Identifying Companion Cells**:
- Companion cells are specialized parenchyma cells that are closely associated with sieve tube elements. They play a crucial role in the functioning of sieve tubes by maintaining the pressure gradient necessary for the transport of substances.

**Hint**: Companion cells are essential for the functioning of sieve tubes.

3. **Analyzing Option A**:
- "Having peripheral cytoplasm and large central vacuole but without nucleus."
- This statement is true as companion cells have a peripheral cytoplasm and large vacuoles, and they do not have a nucleus at maturity.

**Hint**: Think about the structure of companion cells and their characteristics.

4. **Analyzing Option B**:
- "Controls function of sieve tube elements."
- This statement is false because the function of sieve tube elements is controlled by the companion cells, not the other way around.

**Hint**: Consider who controls the functions in the relationship between companion cells and sieve tubes.

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

**Hint**: Recall the presence of companion cells in different plant types.

6. **Analyzing Option 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, allowing for communication and transport between them.

**Hint**: Think about how cells communicate and connect in plant tissues.

### Conclusion:
Based on the analysis:
- The correct answers are **A** and **D**.
- The specialized parenchyma cells closely associated with sieve tube elements are characterized by having peripheral cytoplasm and large central vacuoles (A), and they are connected by pit fields (D).

### Final Answer:
The specialized parenchyma cells closely associated with sieve tube elements are:
**A. Having peripheral cytoplasm and large central vacuole but without nucleus.**
**D. Connected by pit fields present between their common longitudinal walls.**