Fig. 6

The levels of SOD (a), free proline (b) and MDA (c) in leaves. SOD, superoxide dismutase. MDA, malonaldehyde. LN, low nitrogen. AN, adequate nitrogen. The bars indicate means ± SE (n = 12). Different letters on the bars indicate significant differences (P < 0.05) based on multiple comparisons (Tukey’s HSD test) in ANOVA. P-values of the two-way ANOVA of water (W), nitrogen (N) and their interactions (W × N) are indicated. *P < 0.05; **P < 0.01; ns, not significant