## 3 Discussion
In our study, the contents of sesquiterpenes such as (\(-\))-\(\beta\)-elemene, \(\beta\)-panaxalene, (\(-\))-\(\alpha\)-neeboutene and \(\gamma\)-gultrane were high in ginseng. In addition, derivatives of methoxypyrazine, an earthy aroma component in wine, may be the main source of ginseng's unique flavor. 2-Isobutyl-3-methoxypyrazine was detected in all groups, consistent with previous studies and, with increasing growth-years, its contents gradually increased. Secondly, combined with multivariate analysis, it was found that different cultivation modes affected the volatile components in ginseng. Although both GCG and MCG are sources of ginseng, their cultivation modes are quite different. GCG is planted in the field, and the growth process is subject to human interference. Thus, the light exposure time, light intensity, and nutrition of GCG are much better than those of MCG. For comparison, the volatile components of _Zea mays_ L. decrease significantly under light or nutrient deficiency and the contents of (\(Z\))-3-hexenyl acetate and (\(Z\))-3-hexen-1-ol in _Brassica napus_ decreased under nitrogen deficiency [20]. This precedent indicates that light, nutrition, and temperature may be important factors for the significant differences in volatile components of ginseng, and may be the reasons why some volatile component contents were higher in GCG than in MCG [21]. However, although the contents of hexanal, 2-oxo-pentanoic acid, heptanal and octanol in GCG were higher than in MCG, it has been reported that alkane components and intermediate products such as 2-oxo-pentanoic acid contribute less to the fragrance of plants. \(\beta\)-Gurjunene with balsam flavor was significantly higher in MCG than that in GCG, which may be why the taste of MCG is more popular with consumers. In short, the cultivation environment leads to different volatile components among MCG and GCG. Five components were selected as potential cultivation-dependent chemo-markers for the differentiation between \(\text{MCG}_{5,10,15-\text{years}}\) and \(\text{GCG}_{5,10,15-\text{years}}\), including hexanal, 2-oxo-pentanoic acid, heptanal, octanal, and \(\beta\)-gurjunene. The contents of the first four compounds were significantly higher in \(\text{GCG}_{5,10,15-\text{years}}\), while \(\beta\)-gurjunene was significantly higher in \(\text{MCG}_{5,10,15-\text{years}}\). Thirdly, the compositional variation with growth years was explored in MCG. A total of 12 volatile components were selected as potential growth-year-dependent chemo-markers for discrimination among \(\text{MCG}_{5,10,15-\text{years}}\), including \(\beta\)-panaxinsene, \(\beta\)-neoclovene, (\(-\))-\(\alpha\)-neoclovene, \(\beta\)-chamigrene, \(\gamma\)-gurjunene, 2-oxo-pentanoic acid, (\(E\))-2-heptenal, 3-octen-2-one, benzaldehyde, (\(E\))-2-octenal, heptanal, and octanal. The first to sixth compounds were responsible for discrimination between \(\text{MCG}_{5,\text{years}}\) and \(\text{MCG}_{10,15-\text{years}}\), and 2-oxo-pentanoic acid was responsible for the differentiation between \(\text{MCG}_{10,\text{years}}\) and \(\text{MCG}_{5,15-\text{years}}\). The contents of the sixth to twelfth chemo-markers in \(\text{MCG}_{15-\text{years}}\) were significantly higher. Of the 12 chemo-markers, except for benzaldehyde, the contents of the other 11 compounds increased with the growth years, consistent with the market assessment that the higher the growth-years, the greater the value. Therefore, our data suggest that the 12 volatile components might be used as unique chemo-markers to distinguish among \(\text{MCG}_{5,10,15-\text{years}}\). Finally, the compositional variation with growth years was explored in GCG. A total of six volatile components were selected as potential growth-year-dependent chemo-markers for discrimination among \(\text{GCG}_{5,10,15-\text{years}}\), including hexanal, 2-oxo-pentanoic acid, heptanal, benzaldehyde, octanal, and 2-isopropyl-3-methoxypyrazine.