Companion cells, which are specialized parenchyma cells found in the phloem tissue of plants, have several important functions:
1. Loading and unloading of sugars: Companion cells play a crucial role in the transport of sugars produced during photosynthesis. They are responsible for actively loading the sugars (mainly sucrose) into the sieve tubes, which are the main conducting elements of the phloem. This process requires energy derived from the companion cells' mitochondria.
2. Maintenance and regulation of sieve tube elements: Companion cells provide metabolic support to the adjacent sieve tube elements. They help in maintaining the structural integrity of sieve tubes and provide essential nutrients, such as amino acids and ATP, needed for the activity and functioning of sieve tube elements. They also regulate the osmotic pressure within the phloem for efficient sugar transport.
3. Communication and signaling: Companion cells act as a communication hub within the phloem tissue. They facilitate the exchange of information and signaling molecules between different cells, including sieve tube elements, adjacent companion cells, and surrounding cells. This communication is crucial for coordinating different metabolic processes and responses to environmental stimuli.
4. Defense against pathogens: Some companion cells have a role in plant defense mechanisms. They can produce chemical compounds or defense-related proteins that help protect the phloem tissue from pathogens, such as insects, fungi, or bacteria. These defenses can include antimicrobial molecules, receptor proteins for pathogen detection, or cell wall reinforcements to prevent pathogen invasion.
What are the functions of companion of cells (4 Functions)
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