Figure 4.

Effect of different inhibitors on NH₄⁺ uptake from the apoplastic solution in leaf discs of oilseed rape. a, 20 μm CCCP (a protonophore) and 100 μm DES (an ATPase inhibitor) supplied by petiole feeding during a 1-h pretreatment period and subsequently added to the infiltration solution. b, KCl and NaCl added in increasing concentrations to the infiltration solution. c, 10 mm of the nonspecific channel blocker La³⁺ (LaCl₃). d, 10 mm specific K⁺-channel blocker TEA-Cl. In addition to the specified inhibitor the infiltration solution contained 150 mm Mes, pH 6.2, and 10 mm NH₄Cl and was adjusted to an osmotic potential of 350 mosmol with sorbitol. The experiments were carried out at 20°C with a incubation period of 4 min. Values are the means ± se of four replicates.