## 3 Results and Discussion
### Analysis of Differential Metabolite KEGG Enrichment Pathways in Different Tea Cultivars  
_Subjected to Drought Stress_  
To further elucidate the pivotal metabolic pathways associated with the alterations in VOCs for different tea cultivars subjected to drought stress, we performed a comprehensive VOC metabolite pathway enrichment analysis. This analysis enabled the visualization of pathway significance and weight through the enrichment of volatiles with analogous functions. As depicted in Figure 8, KEGG metabolic pathway analysis identified a total of 12 and 14 differential metabolic pathways for the comparisons of FD-D vs. FD-CK and WNZ-D vs. WNZ-CK, respectively. Comprehensive details regarding \(p\)-values, false discovery rates (FDRs), impact factors, compound names, and pathway links are provided in Tables S8 and S9. The identified pathways encompassed monoterenoid biosynthesis, butanoate metabolism, phenylalanine metabolism, fatty acid degradation, fatty acid biosynthesis, caffeine metabolism, cutin, suberine, and wax biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, fatty acid elongation, alpha-linolenic acid metabolism, the biosynthesis of unsaturated fatty acids, and the biosynthesis of various secondary metabolites. Notably, these 12 pathways were consistently observed in both FD and WNZ. In addition, the WNZ-D vs. WNZ-CK comparison revealed two supplementary enriched pathways: phenylalanine, tyrosine, and tryptophan biosynthesis, alongside tryptophan metabolism, primarily attributed to the differential accumulation of the target compound indole. Figure 8: Pathway enrichment analysis of significantly altered VOCs of FD-D vs. FD-CK and WNZ-D vs. WNZ-CK. Differential VOC KEGG enrichment pathway bubble maps (**A**,**C**) and network maps of key target volatiles (**B**,**D**) of FD-D vs. FD-CK and WNZ-D vs. WNZ-CK, respectively. As depicted in Figure 8A,B, the pathways enriched in FD-D vs. FD-CK involved 19 differential VOCs across eight metabolic network pathways. The most significantly enriched metabolic pathway (\(p<0.05\)) was monoterpenoid biosynthesis, which included six differentially accumulated volatiles: nerol, geraniol, perilla alcohol, beta-myrcene, D-limonene, and delta-3-carene. Remarkably, nerol and perilla alcohol levels increased in the FD-D group, whereas geraniol, beta-myrcene, D-limonene, and delta-3-carene were more abundant in the FD-CK group. Moreover, in the WNZ-D vs. WNZ-CK analysis, 23 differential VOCs were linked to seven metabolic networks. The pathways of sesquiterpenoid and triterpenoid biosynthesis, as well as monoterpenoid biosynthesis, were significantly enriched (\(p<0.05\)). Within the sesquiterpenoid and triterpenenoid biosynthesis pathway, the differentially accumulated VOCs included delta-cadinene, carryophyllene, alpha-farnesene, (E)-beta-farnesene, alpha-caryophyllene, and cedrol. In contrast, the enriched VOCs in the monoterpenoid biosynthesis pathway included nerol, geraniol, beta-myrcene, D-limonene, and delta-3-carene. Following drought stress, the only VOC exhibiting increased expression in the WNZ-D cultivar within these two enriched terpenoid metabolic pathways was alpha-farnesene, while the remaining enriched VOCs were found in higher concentrations in the WNZ-CK group. The findings suggest that drought stress markedly influences the accumulation of sesquiterpenes, resulting in a greater prevalence of terpene oxides, including linalool oxides and carryophyllene oxides. In conclusion, both FD and WNZ cultivars were implicated in fatty acid degradation, fatty acid biosynthesis, fatty acid elongation, the biosynthesis of unsaturated fatty acids, and cutin, suberine, and wax biosynthesis post-drought stress. This indicates that tea plants may sustain cellular osmotic pressure and physiological functionality through the synthesis of medium-chain VFADs and unsaturated fatty acids, while simultaneously mitigating water loss via cutin, suberine, and wax biosynthesis to endure drought conditions [50; 51; 52; 54].