Figure 6

Regression analysis of nitrogen (N) allocation proportions in the photosynthetic system (P_P), light-harvesting components (P_L), Rubisco (P_R), and bioenergetics (P_B) with the photosynthetic N use efficiency (PNUE) in the seedling leaves of the four tree species after exposure to different soil N treatments. The determination coefficients (R²) and P-values are shown. The lines fitted for the N-fixing and non-N-fixing trees are significantly different (P < 0.05) according to the results of a one-way analysis of covariance (ANCOVA) with the PNUE as a dependent variable, whether it could fix nitrogen as a fixed factor, and P_P, P_R, P_B, and P_L as covariates.