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companion cell

com·pan·ion cell (plural com·pan·ion cells)


noun 
Definition:
 
cell associated with sieve tube: in flowering plants, a cell that lies alongside a sap-conducting sieve-tube element, whose function it is thought to influence. Companion cells have a prominent nucleus and dense cytoplasm, and form fine cytoplasmic connections plasmodesmata with the adjacent sieve-tube element.

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