## 3 Results and Discussion
### OAV Analysis of HS-SPME-GC-MS Data
Notably, seven VOCs shared across all four groups exhibited OAVs \(\geq\)1, including 1-octen-3-ol (earathy, mushroom), linalool (floral), geraniol (floral), \(\beta\)-damascone (fruity), (E)-\(\beta\)-ionone (floral), citral (citrus), and \(\beta\)-myrce (spicy). These volatiles contribute significantly to the floral and fruity aromatic characteristics of tea leaves. Linalool, which had the highest OAV, is ubiquitous in a wide range of teas, including green tea, black tea, oolog tea, white tea, and yellow tea. Its production is predominantly linked to the light fermentation and drying phases of tea processing, where it imparts a fresh floral fragrance. In addition, geraniol, \(\beta\)-damascone, (E)-\(\beta\)-ionone, and \(\beta\)-myrcene are typically more abundant in black and oolong teas, particularly during fermentation, oxidation, and rolling processes. In contrast, 1-octen-3-ol and citral are more frequently detected in green and white teas, especially during the light fermentation and drying stages. Upon drought stress, 10 key VOCs in the FD cultivar with OAVs exceeding 1 showed a notable increase, including 1-octen-3-ol, 6-methyl-5-hepten-2-one, (E)-\(\alpha\)-ionone, \(\beta\)-damascone, (E,E)-2,4-heptendiad, octanol, oriental, ondocanal, and linalool oxide I. These compounds predominantly contribute to enhanced fruity, citrus, and orange aroma profiles. Conversely, nine volatiles demonstrated a decline in OAVs, such as (Z)-hex-3-en-1-ol, linalool, geraniol, (Z)-jasmone, (E)-\(\beta\)-ionone, (E)-2-nonenal, \(\beta\)-myrcene, \(\beta\)-cadinene, and cedrol, primarily associated with green, grassy, floral, and spicy aromatic characteristics. In contrast, the WNZ cultivar under drought stress exhibited an increase in 15 volatiles with OAVs exceeding 1, including methyl salicate, 1-octen-3-ol, 6-methyl-5-hepten-2-one, 1-octen-3-one, (E)-\(\alpha\)-ionone, \(\beta\)-damascone, hexanal, (E,E)-2,4-heptendiad, octanol, (E)-2-nonenal, (E)-2-decenal, nonana-(2E,4E)-dienal, linalool oxide I, and linalool oxide II, which contribute to heightened minty, earthy, citrus, violet, fruity, fatty, spicy, floral and woody aroma notes. On the other hand, eight VOCs displayed reduced OAVs, including hex-(3Z)-enyl acetate, linalool, geraniol, (Z)-jasmone, (E)-\(\beta\)-ionone, nonanal, \(\beta\)-myrcene, and \(\delta\)-cadinene, characterized by green, floral, orange, spicy, and woody aromas. In summary, these findings suggest that drought stress predominantly intensified citrus and fruity aromas, while diminishing green and grassy notes. A consistent trend across both cultivation and growth of the OAVs, including the 1-octen-3-ol, 6-methyl-5-hepten-2-  
vars was the elevation of OAVs for aldehyde and ketone VOCs, whereas certain alcohol and terpene VOCs exhibited decreased OAVs. Particularly noteworthy is the observed reduction in linalool's OAV, accompanied by a corresponding increase in linalool oxide's OAV, indicating a potential conversion of linalool to its oxides in response to environmental stressors, thus contributing to floral and woody aroma characteristics. This phenomenon aligns with the results derived from HS-GC-IMS analyses. Synthesis of the data presented in Figure 3 and Table S4 underscores the distinct adaptive responses of the two tea cultivars to drought stress. The FD cultivar's response was characterized by an expansion in the number of VOCs, while the WNZ cultivar exhibited a strategy of enhancing the concentrations of low-threshold, aroma-active compounds, thereby augmenting their OAVs and leading to a more pronounced aromatic profile. This differential response between cultivars presents an intriguing avenue for future exploration.