Fig. 2
Relevant signals and defense mechanisms induced by drought. (A) Content of free proline, soluble protein, NO and Ca2+ in leaves. (B) Content of GSH, soluble protein, SOD, APX and CAT activity in leaves under the combined conditions of water and N forms. The four water conditions (well-watered condition (WW), partial-root zone drought in horizontal (H-PRD) and vertical (V-PRD) direction, and full root zone drought (FRD) are combined with nitrate (NN) or ammonium (AN) treatment. Means ± SE are indicated by the columns and the bars above columns (n = 4). Statistically different values (P < 0.05) based on the multiple comparisons (Fisher’s LSD test) in ANOVA are indicated by different letters above the bars. The results of two-way ANOVA (water effect, nitrogen effect, and interaction effect) are listed as: *P < 0.05; **P < 0.01; ns, not significant