, dry weight and MDA in leaves. Time course of the changes in FV/FM and ΦII (A), dry weight in leaves (B) and MDA levels (C) of Zea mays plants, previously grown for 17 days under nitrogen starvation (T0) and incubated for further 6, 30 and 54 h in the absence or presence of 10 mM NO3-. Symbol in Figure A: open squares, Control; closed squares, 10 mM NO3- ; horizontal bar: white bars, light periods; black bars, dark periods (for details see Figure 1). Values are the mean ± SE of three independent biological samples analyzed in triplicate (n = 9). Samples indicated with the same letters do not differ significantly according to Tukey's test (p < 0.01).