Figure 4.

The influence of Cu on Fe uptake (A) and Fe/Cu reductase (B). C. reinhardtii cultures were subjected to different treatments: 1, control; 2, 1 d without Fe; 3, 1 d without Fe and 4 d without Cu; 4, 4 d without Cu; 5, 3 d without Cu, supplemented with Cu for the last day; and 6, 3 d without Cu and Cu resupply by concomitant remove of Fe for the last day. A, Fe was applied as Fe³⁺-hydroxyethylenediamine triacetic acid (HEDTA), or for Fe²⁺ uptake 10 mm ascorbic acid was added (bars labeled with an asterisk). B, Fe³⁺ and Cu²⁺ (*) reductases were measured. Values represent the mean of three independent assays. ses are shown.