Companion cells

Definition

Companion cells are specialized parenchyma cells found in the phloem of flowering plants. They play a crucial role in the transport of photosynthates (sugars) from source tissues to sink tissues.

5 Must Know Facts For Your Next Test

1. Companion cells are intimately connected to sieve tube elements through numerous plasmodesmata.
2. They assist in loading and unloading sugars into the sieve tubes for translocation throughout the plant.
3. Companion cells help maintain the metabolism and function of sieve tube elements, which lack certain organelles.
4. They have dense cytoplasm and a prominent nucleus compared to other plant cells.
5. In some plants, companion cells can be involved in signaling and defense mechanisms against pathogens.

Review Questions

Related terms

Sieve Tube Elements: Specialized elongated cells in the phloem that are responsible for transporting sugars and other organic nutrients.

Phloem:

The vascular tissue responsible for the transport of nutrients, particularly sucrose, throughout the plant.

Plasmodesmata:

Microscopic channels that traverse cell walls, allowing transport and communication between individual plant cells.