Figure 5.

Effect of apoplastic pH on apoplastic NH₄⁺ concentration and H⁺ net uptake from the apoplastic solution in leaf discs of oilseed rape. a, Steady-state apoplastic NH₄⁺ concentration at different pH values in the apoplastic solution. Leaf discs were infiltrated for 4 min with 150 mm Mes buffer, pH 5.0 and 6.0, or 150 mm Tes buffer, pH 7.0 and 8.0, adjusted to an osmotic potential of 350 mosmol with sorbitol. b, H⁺ net uptake from the apoplastic solution during the infiltrations described in a. •, pH in the infiltration solution prior to infiltration; ○, pH in the solution extracted after 4 min. Values are the means ± se of four replicates. FW, Fresh weight.