## 4 Discussion  
Volatile metabolites are key mediators in plant-environment interactions, contributing to chemical defense, ecological signaling, and the sensory qualities of plant-derived products [3; 4; 5]. In the present study, we employed untargeted GC-MS-based metabolomics integrated with rOAV screening and sensory annotation to investigate the volatile profiles of two _Phoebe_ species of ecological and ornamental importance, namely _P. zhennan_ and _P. chekiangensis_. Our findings revealed extensive volatile diversity, with pronounced organ- and species-related patterns that reflect both functional differentiation and evolutionary divergence. A total of 1666 volatile metabolites were detected across all seed and leaf samples. These metabolites spanned multiple structural classes, with terpenoids, aldehydes, alcohols, ketones, and aromatic compounds dominating the profiles (Figure 1C). Such diversity is characteristic of Lauraceae and comparable to other aromatic trees such as _Cinnamomun_ and _Litsea_[24; 25]. The PCA and hierarchical clustering (Figure 1B, D) showed a clear separation of samples by both species and tissue type, with distinct clustering patterns observed  
Figure 6: Venn diagram analysis of differential volatile metabolites highlighting species-related and organ-related differences. (**A**) Venn diagram comparing differential volatile metabolites between seeds (ZJN1_vs_ZN1) and leaves (ZJN2_vs_ZN2) of _P. chekiangensis_ and _P. zhennan_. The overlapping metabolites represent species-related core volatile differences conserved across tissues. (**B**) Venn diagram comparing differential volatile metabolites between seeds and leaves of _P. chekiangensis_ (ZJN2_vs_ZJN1) and _P. zhennan_ (ZN2_vs_ZN1). for both _P. zhennan_ and _P. chekiangensis._ Leaves generally exhibited a greater representation of terpenoid- and GLV-related compounds, often associated with herbivore resistance, allelopathy, or stress responsiveness [26; 27]. In contrast, seeds were richer in volatiles with fruity, sweet, and floral descriptors, likely linked to seed protection and attraction of dispersal agents. The rOAV analysis identified 540 aroma-active metabolites, with a few standout compounds, such as two metabolites (3-Cyclohexene-1-methanethiol,\(\alpha\),\(\alpha\),\(\alpha\)-trimethyl- and \(\beta\)-damascone) that displayed extremely high values in _P. zhennan_ leaves (Figure 2). Their accumulation in _Phoebe_ leaves may indicate active carotenoid turnover and oxidative pathways, potentially linked to light-induced signaling or stress responses. Sulfur-containing compounds, on the other hand, often contribute to pungent green or garlic-like aromas and are known to play antimicrobial or herbivore-deterring roles [28]. These findings underscore the importance of combining concentration data with odor threshold values to identify functionally relevant volatiles that dominate the perceived aroma profile. The comparison of differential metabolite enrichment between species revealed additional layers of divergence. The Volcano plot analysis (Figure 3) showed that _P. zhennan_ had a greater abundance of metabolites in seeds, while _P. chekiangensis_ exhibited more downregulation in leaves, suggesting tissue-related repression or metabolic channeling. The KEGG enrichment analysis (Figure 4) supported this trend: _P. chekiangensis_ seeds were enriched in monoterenoid and phenylpropanol biosynthesis pathways, while _P. zhennan_ leaves showed greater involvement of sesquiterpenoid, triterpenoid, and terpenoid backbone biosynthesis. These observations are consistent with prior studies highlighting lineage-specific expansion and expression divergence of terpene synthase (TPS), cytochrome P450s, and BAHD acyltransferases in Lauraceae [29; 30]. Species-dependent specialization of volatile pathways may reflect differing ecological niches, historical uses, or adaptive strategies. From a sensory perspective, our flavoromics analysis provided a functional interpretation of the metabolomic data.