## 3 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **HMGR** & **SS** & **FPS** & **SE** & **DS** & **PPDS** & **PTS** & **B-AS** & **OAS** \\ \hline Rg1 & 0.11 & \(-\)0.90 ** & \(-\)0.18 & \(-\)0.71 * & \(-\)0.55 & \(-\)0.88 ** & \(-\)0.01 & \(-\)0.92 ** & \(-\)0.99 ** \\ Re & \(-\)0.04 & \(-\)0.95 ** & \(-\)0.34 & \(-\)0.81 ** & \(-\)0.65 & \(-\)0.95 ** & 0.17 & \(-\)0.97 ** & \(-\)0.99 ** \\ Rf & \(-\)0.03 & \(-\)0.90 ** & \(-\)0.37 & \(-\)0.80 ** & \(-\)0.60 & \(-\)0.95 ** & 0.26 & \(-\)0.95 ** & \(-\)0.99 ** \\ Rb1 & 0.12 & \(-\)0.87 ** & \(-\)0.22 & \(-\)0.71 * & \(-\)0.51 & \(-\)0.90 ** & 0.10 & \(-\)0.92 ** & \(-\)1.00 ** \\ Rc & \(-\)0.34 & \(-\)1.00 ** & \(-\)0.54 & \(-\)0.93 ** & \(-\)0.86 ** & \(-\)0.95 ** & 0.28 & \(-\)0.98 ** & \(-\)0.89 ** \\ Rb2 & \(-\)0.55 & \(-\)0.91 & \(-\)0.80 ** & \(-\)0.99 ** & \(-\)0.90 ** & \(-\)0.97 ** & 0.65 & \(-\)0.93 ** & \(-\)0.79 ** \\ Rb3 & 0.21 & \(-\)0.85 ** & \(-\)0.09 & \(-\)0.63 & \(-\)0.45 & \(-\)0.83 ** & \(-\)0.06 & \(-\)0.88 ** & \(-\)0.98 ** & \(-\)0.98 ** \\ Rd & 0.08 & \(-\)0.91 ** & \(-\)0.21 & \(-\)0.73 * & \(-\)0.56 & \(-\)0.90 ** & 0.04 & \(-\)0.93 ** & \(-\)0.99 ** \\ Ro & \(-\)0.19 & 0.84 ** & \(-\)0.01 & 0.58 & 0.47 & 0.73 * & 0.27 & 0.82 ** & 0.89 ** \\ PPT & 0.62 & 0.83 ** & 0.60 & 0.83 ** & 0.92 ** & 0.69 & \(-\)0.24 & 0.74 * & 0.52 \\ PPD & 0.48 & \(-\)0.24 & 0.08 & \(-\)0.16 & 0.14 & \(-\)0.43 & 0.13 & \(-\)0.38 & \(-\)0.60 \\ Total & 0.22 & \(-\)0.70 * & \(-\)0.18 & \(-\)0.58 & \(-\)0.32 & \(-\)0.81 ** & 0.19 & \(-\)0.79 * & \(-\)0.92 ** \\ \hline \hline \end{tabular}  
* indicates a significant correlation (\(p<0.05\)). ** indicates a significant correlation (\(p<0.01\)).  
\end{table} 
Table 12: Correlation analysis between gene expression and ginsenosides in leaves at different growth times. photosynthetically active radiation may damage the leaves, thus causing the reduction of ginsenosides. Soil water potential were negatively correlated with most of the individual ginsenosides, and suitable drought conditions can improve the biosynthesis of ginsenosides. Relative humidity is an important factor affecting the quality of medicinal materials. Appropriate drought stress can improve the active ingredients in these medicinal materials [39]. With the development of molecular biology, people have also begun to focus on the influence of intrinsic genetic factors on the formation of medicinal materials [40]. HMGR was differentially expressed among tissues, with a high level of expression in the leaf and low level of expression in the stem, suggesting that leaves are crucial to terpenoid biosynthesis [41]. [PERSON] et al. reported that overexpression of FPS caused an approximate 2.4-fold increase of ginsenoside content in transgenic ginseng hairy roots [42]. [PERSON] et al. introduced the SS gene of P. ginseng into Eleutherococcus semicosus by Agrobacteriumium-mediated transformation, and found that SS activity significantly improved the production of phytosterols and triterpenoids [43]. [PERSON] et al. cloned SQE from the root of P. notoginseng by PCR. Real time quantitative PCR analysis showed that its cDNA had a different expression pattern and is highly expressed in the root, especially in three-year-old root [44]. [PERSON] et al. analyzed the transcriptomes of _P. ginseng_ and identified 133 CYP450 genes by 454 sequencing technology. Their study laid an important foundation for the further screening of CYP450 involved in ginsenoside biosynthesis [45]. In this study, expression analysis by real-time quantitative PCR indicated that genes were differentially expressed among tissues. SS, DS, SE, PPTS, and PPDS had high levels of expression in the leaf, which is closely related to the distribution of dammarane ginsenoside in leaves. FPS, HMGR, \(\beta\)-AS, and OAS had high levels of expression in the root, which is consistent with the distribution of Ro mainly in the root.