Perfusion experiments with excised internodes of tomato (Lycopersicon esculentum cv Moneymaker) showed that the uptake of glutamic acid and sucrose from the xylem vessels is accompanied with coupled proton co-transport and potassium antiport at low pH (<5.5). At high pH (5.5) both proton and potassium co-transport accompany the uptake. The results fit into the proton pump concept. © 1979.
Van Bel, A. J. E., & Van Erven, A. J. (1979). Potassium co-transport and antiport during the uptake of sucrose and glutamic acid from the xylem vessels. Plant Science Letters, 15(3), 285–291. https://doi.org/10.1016/0304-4211(79)90121-4