Fig. 2.

Metabolomics heat map based on LC-MS secondary mass spectrometry. The color gradient illustrates the Z-scores of seven metabolites in the shoot (A) and root (B), calculated as the mean-centered normalized intensity values divided by the SD for each metabolite. SCK, ST1, and ST2 indicate the metabolites in the shoots of plants exposed to sole NO₃^–, mixed N, and sole NH₄⁺ supply, respectively. RCK, RT1, and RT2 indicate the metabolites in the root of plants exposed to sole NO₃^–, mixed N, and sole NH₄⁺ supply, respectively. Seven repeats were performed for each N treatment. Significant difference for each metabolite was defined as P<0.05 and fold change ≥1.5 or ≤0.66. Compared with the effects of sole NO₃^– supply, the concentration of metabolites is either increased by both mixed N and sole NH₄⁺ supply (blue bracket), increased by only sole NH₄⁺ supply (purple bracket), reduced by both mixed N and sole NH₄⁺ supply (green bracket), reduced by only sole NH₄⁺ supply (brown bracket), or does not differ among the treatments (orange bracket).