*2.5. Association Analysis of the DAMs and DEGs*

Correlation analysis was carried out on the DAMs and DEGs. The variations in the metabolites and their corresponding genes with the Pearson correlation coefficient over 0.8 were selected to draw nine quadrant diagrams and the correlation coefficient cluster heat map. As shown in Figure 5, the higher number of DAMs and DEGs was in the seventh and ninth quadrants; and they were positively correlated in the seventh quadrant and negatively correlated in the ninth quadrant.

**Figure 5.** Quadrant diagrams representing the association of the DAMs and DEGs between the non-mycorrhizal and mycorrhizal *A. roxburghii* growth for six months. The x-axis represents that the log2 ratio of gene and the y-axis represents the log2 ratio of metabolite; black dotted lines represent the different threshold; each point represents a gene or metabolite; black dots represent the unchanged genes or metabolites; green dots represent differentially accumulated metabolites with unchanged genes; red dots represent differentially expressed genes with unchanged metabolites; blue dots represent both differentially expressed genes and differentially accumulated metabolites; it is divided into -1 –-9 quadrants from left to right and from top to bottom with black dotted lines; the -1 , -2 and -4 quadrants indicate that the expression abundance of metabolites is higher than that of genes; the -3 and -7 quadrants indicate that the expression patterns of genes are consistent with the metabolites; the -<sup>5</sup> quadrant indicates that the genes and metabolites are not differentially expressed; the -6 , -8 and -9 quadrants indicate that the expression abundance of metabolites is lower than that of genes.
