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.
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.
noun, Nautical. 1. an inboard ladder or stair, as in a companionway.
noun 1. a literary or musical work that has a close relationship to another work by the same author or composer.
noun 1. the cultivation of different types of plants in close proximity so as to benefit each other, as planting a deer-repellent plant in a flower garden.
- Companion set
noun 1. a set of fire irons on a stand