Active Transport of Choline Sulfate by Barley Roots

Abstract
Barley roots (Hordeum vulgare) take up choline sulfate by 2 mechanisms: A low-range mechanism which is the result of active transport and operates at half maximal velocity at a choline sulfate concentration of approximately 10-5 M. and a high-range mechanism which becomes apparent at about 2 x 10-4 M. A 2-site carrier for choline sulfate with an anionic site which binds the quaternary N and a cat ionic site which binds the sulfate group is proposed.