Figure 2. Effect of Cu supply on root ferric-chelate reductase activity. (A) Hydroponic Arabidopsis thaliana (Col-0) root ferric-chelate reductase activity in Fe sufficient or deficient plants, treated for 3 d with +Fe (25 μM) or –Fe and Cu concentrations as indicated. (B) Cucumber root ferric-chelate reductase activity in Fe sufficient or deficient plants, treated for 3 d with 10 μM, 0.5 μM, or –Fe, with indicated Cu concentrations in the hydroponic solution. Some treatments also included 5 μM BCS to test for Cu contamination.