Which of the following cells helps in maintaining the pressure gradient in the sieve tubes?

Options

A. Pholem parenchyma
B. Bast fibre
C. Companion cells
D. Wood fibre

Answer

To answer the question "Which of the following cells helps in maintaining the pressure gradient in the sieve tubes?", we will analyze the options provided and identify the correct one step by step.

### Step-by-Step Solution:

1. **Understanding Sieve Tubes**:
- Sieve tubes are part of the phloem tissue in plants responsible for the transport of nutrients, particularly sugars produced during photosynthesis.

2. **Identifying the Options**:
- The options given are:
- A) Phloem parenchyma
- B) Bast fibers
- C) Companion cells
- D) Wood fibers

3. **Analyzing Each Option**:
- **A) Phloem parenchyma**:
- These cells primarily function in the storage of food and do not play a direct role in maintaining pressure gradients in sieve tubes.
- **B) Bast fibers**:
- These are dead cells made of sclerenchyma that provide structural support and do not contribute to pressure maintenance in sieve tubes.
- **C) Companion cells**:
- These are specialized parenchyma cells closely associated with sieve tubes. They help in loading and unloading sugars into the sieve tubes and are crucial for maintaining the pressure gradient necessary for the flow of sap.
- **D) Wood fibers**:
- These are also supportive cells and do not have a role in the functioning of sieve tubes.

4. **Conclusion**:
- Based on the analysis, the correct answer is **C) Companion cells**. They are essential for maintaining the pressure gradient in the sieve tubes, allowing for efficient transport of nutrients.