1. Metabolically active: Intermediate companion cells are highly metabolically active cells that play a role in maintaining the energy requirements of the sieve elements in the phloem.
2. Connected to sieve elements: Intermediate companion cells are connected to sieve elements via plasmodesmata. This connection allows for the transport of sugars and other molecules between the companion cells and sieve elements.
3. Nucleus and organelles: Intermediate companion cells possess a large nucleus and various organelles such as mitochondria, ribosomes, and endoplasmic reticulum. These organelles are involved in cellular processes and provide the necessary energy for the companion cells.
4. Thickened cell walls: The cell walls of intermediate companion cells are thicker compared to other plant cells. This thickening provides structural support and allows for efficient transfer of nutrients and molecules between cells.
5. Active transport: Intermediate companion cells actively transport sugars such as sucrose into the sieve elements through specialized membrane proteins. This process requires the expenditure of energy in the form of ATP.
6. Phloem loading/unloading: Intermediate companion cells are involved in the loading and unloading of sugars into and out of the sieve elements of the phloem. They regulate the movement of sugars from source tissues (such as leaves) to sink tissues (such as roots or developing fruits).
7. Regulation of sieve tube pressure: Intermediate companion cells help regulate the pressure within the sieve tubes by actively pumping ions in and out of the sieve elements. This control of pressure is important for the efficient transport of nutrients through the phloem.
8. Communication and signaling: Intermediate companion cells also play a role in communication and signaling between different parts of the plant. They can communicate information about nutrient availability, stress signals, and plant defense responses.
Characteristics of intermediate companion cells
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