Phloem elements which are long, tube-like structures, arranged longitudinally and are associated with the companion cells

Answer

**Step-by-Step Solution:**

1. **Understanding Phloem Tissue**: Phloem is a complex tissue in plants responsible for the transport of nutrients, particularly sugars produced during photosynthesis. It consists of several types of cells.

2. **Identifying Phloem Elements**: The main components of phloem include:
- Sieve tube elements
- Companion cells
- Parenchyma
- Fibers

3. **Focusing on Sieve Tube Elements**: Among these components, the question specifically refers to the long, tube-like structures that are arranged longitudinally. These are known as sieve tube elements.

4. **Characteristics of Sieve Tube Elements**:
- They are elongated and form continuous tubes.
- They have perforated walls that resemble a sieve, which is why they are named "sieve tubes."
- They lack a nucleus, which is a distinctive feature.

5. **Association with Companion Cells**: Sieve tube elements are closely associated with companion cells, which help in the maintenance and functioning of the sieve tubes.

6. **Function of Sieve Tube Elements**: The primary function of sieve tube elements is to transport food (sugars) from the leaves, where it is produced, to other parts of the plant.

7. **Conclusion**: Therefore, the answer to the question is "sieve tube elements."

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