Figure 1.

Effect of cadmium on NO₃⁻ uptake and concentration and NO₃⁻ reductase activity in the roots and the NO₃⁻ concentration in xylem sap in Col-0 plants. Plants were precultured in complete nutrient solution using 2.25 mm NO₃⁻ and 750 μm NH₄⁺ as the nitrogen source for 5 weeks, and then were transferred to complete nutrient solution alone (control) or containing 10 μm CdCl₂ (Cd) for 7 d, after which the analyses were performed. A, Rate of NO₃⁻ uptake by the roots. B, NO₃⁻ concentration in the roots. C, NO₃⁻ reductase activity in the roots. D, NO₃⁻ concentration in the xylem sap. NO₃⁻ uptake by Col-0 plants was measured using 2.25 mm ¹⁵NO₃⁻ for 5 min. Bars represent the sd (n = 4–5 biological replicates). Asterisks indicate significant differences compared with the controls (**P < 0.01, ***P < 0.001; two-tailed Student’s t test). FW, Fresh weight.