Fig. 4

Stem anatomical properties of Catalpa bungei seedlings under varying water and nitrogen supply. (A) Anatomical diagram of the xylem. (B) Statistical analysis of xylem parameters. ph, phloem; xyl, xylem; ves, vessel. 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