Journal of Tea Science Research, 2024, Vol.14, No.6, 322-334 http://hortherbpublisher.com/index.php/jtsr 328 withering time, the main volatile aroma components in tea leaves (especially terpenes and esters) accumulated significantly, and the aroma score and Owuor aroma index increased simultaneously (Figure 2). Figure 2 Tea plant leaves changes in water content, temperature and overview of nonvolatile compounds. (a) The phenotype of the picked tea leaves at 0, 6, 12, 18, 24, and 30 h. (b) The moisture content and temperature of tea leaves following withering for different time periods. Data represent the mean value ± standard deviation (n = 3), *, p < 0.05 compared with the sample of 0 h; **, p < 0.01 compared with the sample of 0 h. (c) The proportion of total content of various volatile substances in tea plant leaves during withering. (d) Principal component analysis score plot of tea leaves with different withering times (0, 6, 12, 18, 24, and 30 h). (e) KEGG classification of differential metabolites during withering (Adopted from Deng et al., 2023) Image caption: The figure shows that as the withering time increases, tea leaves gradually lose moisture, change color, and curl, accompanied by a rise in temperature. Terpenes and esters accumulate significantly, and the PCA results confirm that aroma compounds undergo stage-specific changes over time. KEGG enrichment further reveals that metabolic pathways closely related to terpene and ester biosynthesis are activated, verifying the active synthesis of volatile compounds (Adapted from Deng et al., 2023) Key terpenes (such as linalool) and esters (such as 3-hexen-1-ol acetate) peaked at 12-30 hours, enhancing the perception of floral and fruity aromas. Gene expression analysis found that α-linolenic acid metabolism and jasmonic acid signaling pathways were activated, and related enzyme genes (like AOS and JAR) were upregulated, promoting aroma synthesis. In addition, the WGCNA co-expression network identified three modules closely related to aroma accumulation and locked in potential regulatory genes such as ACOT and GOLS2, which may promote the release of fatty acids through drought stress response mechanisms and provide a source for ester precursors (Deng et al., 2023; Liu et al., 2024). 6.2 Oolong tea enhances aroma accumulation through JA pathway The unique aroma of oolong tea is an important determinant of its quality and market value. Different tea varieties show great differences during processing (Kong et al., 2023; Li et al., 2024a). A study focused on two tea varieties, "Chungui (CG)" and "Fuyun No. 6 (F6)", which is not suitable for making oolong tea, and compared their aroma metabolism, transcriptome expression and jasmonic acid (JA) accumulation after withering and mechanical damage treatment (Li et al., 2024a). The study found that after treatment, the CG variety accumulated more
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