Figure 3.

Ni and His concentrations in xylem sap (a) and in root fresh biomass (b; fresh weight) of B. juncea. The hydroponic root medium of 6-week-old plants was supplemented with various solutes, i.e. none (control), 300 μm Ni, 300 μm Ni and 300 μm l-His, 300 μm Ni preceded by a pre-exposure to 1 mm l-His for 4 h (Pre-l-His + Ni), 300 μm Ni and 300 μm d-His, or 300 μm Ni and 300 μm l-His with an excess of 3 mm Ala. Values are arithmetic means ± sd of n = 6 replicates, and means ± sd of n = 3 replicates for the Ni + l-His + Ala and the Ni + d-His treatments. Each replicate value corresponds to pooled samples from three plants in one culture vessel. For each compound analyzed, different characters indicate that mean values are significantly different at P < 0.05 (uppercase for His and lowercase for Ni). Two independent experiments were performed with three replicate culture vessels per treatment in each experiment, except for the Ni + l-His + Ala treatment, which was not repeated in an independent experiment. n.a., Not analyzed; n.d., not detectable.