Companion cells

Options

A. Are specialised sclerenchymatous cells
B. Are specialised parenchymatous cells
C. Are associated with phloem fibres
D. Are without cell wall

Answer

### Step-by-Step Solution for the Question on Companion Cells:

1. **Understanding Companion Cells**: Companion cells are specialized cells found in the phloem tissue of angiosperms (flowering plants). They are closely associated with sieve tube elements.

**Hint**: Remember that companion cells are specifically related to the phloem and play a crucial role in transport.

2. **Cell Type**: Companion cells are classified as specialized parenchyma cells. Parenchyma cells are fundamental tissue types in plants that are involved in various functions, including storage and transport.

**Hint**: Focus on the type of cells; they are not just any cells but specialized parenchyma cells.

3. **Cell Structure**: These cells are nucleated, meaning they contain a nucleus. They also have a significant number of ribosomes, plastids, and mitochondria, which are essential for their metabolic functions.

**Hint**: Recall that the presence of organelles like ribosomes and mitochondria indicates active metabolic processes.

4. **Function**: The primary function of companion cells is to assist in the transport of sugars and amino acids into and out of the sieve tube elements. They utilize transmembrane proteins to actively transport these substances from source tissues (like leaves) into the sieve tubes.

**Hint**: Think about the role of companion cells in nutrient transport, especially in relation to the sieve tubes.

5. **Association with Sieve Tubes**: Companion cells are directly associated with sieve tube elements, which lack certain organelles (like ribosomes and nuclei). This relationship is crucial for the functioning of the phloem.

**Hint**: Remember that companion cells help sieve tubes function effectively due to their structural and functional differences.

6. **Evaluating Options**: When considering the options provided:
- **Option 1**: Incorrect, as they are not specialized clarenchyma cells.
- **Option 2**: Correct, as they are specialized parenchyma cells.
- **Option 3**: Incorrect, as they are associated with sieve tubes, not phloem fibers.
- **Option 4**: Incorrect, as they do have a cell wall.

**Hint**: Analyze each option carefully based on the characteristics and functions of companion cells.

### Conclusion:
The correct answer is that companion cells are specialized parenchyma cells associated with sieve tube elements in the phloem tissue of angiosperms.