Companion cells are usually seen associated with

Options

A. fibres
B. parenchyma
C. xylem vessels
D. sieve tubes

Explanation

**Step-by-Step Solution:**

1. **Understanding Companion Cells**: Companion cells are specialized cells found in the phloem tissue of vascular plants. They play a crucial role in the transport of nutrients.

2. **Association with Phloem**: Companion cells are primarily associated with sieve-tube elements, which are part of the phloem. The phloem is responsible for the conduction of organic nutrients, particularly sugars, throughout the plant.

3. **Function of Companion Cells**: Companion cells support the sieve-tube elements by providing them with the necessary metabolic functions, as sieve-tube elements are typically devoid of a nucleus and cannot perform these functions independently.

4. **Conclusion**: Thus, companion cells are usually seen associated with sieve-tube elements in the phloem tissue.

**Final Answer**: Companion cells are usually seen associated with sieve-tube elements.

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