title: A model for proton and potassium co-transport during the uptake of glutamine and sucrose by tomato internode disks.
abstract: Internode disks of tomato (Lycopersicon esculentum cv. Moneymaker) were shaken in glutamine and sucrose solutions. At low external pH (<±5.5), the uptake of these substances was accompanied with K(+) efflux, at high pH (>±5.5) with K(+) influx. Low concentrations of external K(+) (2 mmol l(-1)) stimulated the uptake of glutamine, which was strongly inhibited by the supply of high K(+) concentrations (20 mmol l(-1)). The effect of K(+) was particularly pronounced at high pH-values. Addition of CCCP in light reduced the uptake of glutamine to the same level as in the dark, and stopped the K(+) fluxes which coincided with the uptake. A model is presented wherein the movements of K(+) across the membrane are related to co-transport, depending on the membrane potential and the Nernst potential of K(+).
authors: Botanical Laboratory, State University of Utrecht, Lange Nieuwstraat 106, 2501, Utrecht, The Netherlands.
authors: A J
authors: AJ
authors: van Bel
authors: A J
authors: AJ
authors: van Erven