companion cell

noun

, Botany.

1. any of a number of specialized parenchymal cells adjacent to a sieve tube in the phloem of flowering plants, believed to regulate the flow of nutrients through the tube.

companion cell

/ kəm-păn′yən /

1. A specialized parenchyma cell, located in the phloem of flowering plants and closely associated with the development and function of a sieve-tube element. Companion cells probably provide ATP, proteins, and other substances to the sieve-tube elements, whose cytoplasm lacks many structures necessary for cell maintenance.

Word History and Origins

Origin of companion cell¹

First recorded in 1885–90