## 2 Results
### Identification and Classification of Differentially Accumulation Metabolites (DAMs)  
Based on VIP \(\geq\) 1 and fold change \(\geq\) 2 or \(\leq\)0.5, the analysis revealed a total of 331 differential metabolites exhibiting significant changes (Table S1). Most of the differential volatile metabolites were identified between the husks and leaf callus, with a total of 229 types. This was followed by combinations of leaves and leaf callus (160 types), leaves and husks (149 types), roots and husks (148 types), as well as leaves and seeds (145 types). Only 54 different volatile components were found between roots and seeds, while 76 different volatile components were identified between leaf callus and roots, as well as leaf callus and seeds. After intersecting the control groups in a Venn diagram, only 19 metabolites were found to be common among them. Overall, volatile components exhibited distinct spatial distribution patterns across various tissue sites (Figure 2C). The callus exhibited a greater number of differential metabolites in leaves and husks while showing fewer differences with roots, stems, and seeds (Figure 2D). The metabolic pattern of leaves exhibited signifi  
Figure 2: Analysis of volatile components in different tissue parts of _Aquilaria sinensis_. (**A**) The composition of volatile compounds in the class. (**B**) The principal component analysis (PCA) score plots of _A. sinensis_ between six different tissue parts and quality control (QC) samples. (**C**) Venn diagram illustrating the distribution of various VOCs across different tissue components of _A. sinensis_. Each circle in the graph represents a comparison group. The numbers in the overlaps between the circles represent the number of common metabolites among the comparison groups. The number in the circle without any overlaps represents the number of distinct metabolites among the comparison groups. (**D**) Statistics of differential accumulation metabolites (DAMs) with different comparisons. cant changes after callus formation, resembling the metabolic patterns observed in roots, stems, and seeds. Additionally, the heatmap clearly depicted their classification into six distinct categories (Figure 3), thereby indicating variations in metabolite content across six different tissue sites. Among them, terpenoids, ketones, and other volatile metabolites generally accumulate at high levels in leaf callus. The accumulation of various metabolites in the husk was minimal. These findings suggest that there are variations in tissue metabolite accumulation patterns among different types of _A. sinensis_. The top 20 differential metabolites were identified in distinct groups (Figure S3). In the comparison between husk and leaf, the heterocyclic compound 2,2'-Isopropylidenebis(5-methylfuran) was found to be significantly up-regulated, while the ester compound Methyl 3-methyl-2-butenoate was significantly down-regulated. The ketone compound 4-Hexen-3-one was consistently up-regulated as a highly significant differential metabolite, whereas the heterocyclic compound Isopropyl methoxy pyrazine and the alcohol compound trans-2-Nonen-1-ol were both significantly down-regulated. The ketone compound cyclopentanone exhibited a highly significant up-regulation in husk vs. stem, whereas the terpenoid compound cis-\(\alpha\)-bergamotene showed a highly significant down-regulation. The significantly down-regulated differential metabolites in leaf callus vs. husk/leaf/stem, root vs. leaf/stem, and seed vs. leaf/stem were exclusively ketone compound 4-Hexen-3-one. Conversely, the highly significantly up-regulated differential metabolites, except for leaf callus/root vs. leaf, comprised heterocyclic compound 2,2'-Isopropylidenebis(5-methylfuran), ketone compound Cyclopentanone in root/seed vs. stem comparison, and the remaining compounds were ketone compound 3-Acetylphenol and alcohols 6,10-dimethylundeca-5,9  
Figure 3: The heat map depicts the clustering of differential metabolites.