(A) Nitrate concentration, (B) enzymatic activity and (C) Northern Blot analyses of NR. Assay and northern blot were performed on root and leaf of plant during the progression of Fe deficiency treatment. Sampling was performed at 0, 1, 3, 7 days after Fe withdraw. The activities are expressed as percentage (%) of the relative activity of the Fe-deficient samples (columns 1, 3, 7 d) compared to Fe sufficient plants (column 0 d). Activity of control (0 d) was 5.6 and 9.8 nmol NADH mg-1 prot min-1, respectively for root and leaf (complete activity data are reported in Additional file 1). Data are means ± SE (n = 4). In the case of significant difference (P<0.05) values with different letters are statistically different.