Figure 4

Substrate-concentration effect on the net nitrate uptake by intact roots (A) and leaf discs (B). Full circles, before nitrate supply; open circles, 4- (roots) or 12-h (leaves) after supply of 4 mM nitrate. The variable concentrations of potassium in the uptake solutions (0.05-10 mM KNO₃) were compensated with K₂SO₄. Data are means ± SD of two experiments with four replicates.