## 5 Conclusions  
A total of 32 volatile compounds were identified from flowers of _L. caudata_ using HS-SPME-GC-MS. The main groups of the compounds were aliphatic alcohols, aliphatic alkanes, benzenoids, monoterpenes, and irregular terpen previously described in plants. Qualitative and quantitative changes in scent emission varied significantly during different flowering stages and times, as well as within different flower organs. The full-blooming stage showed the highest emission of VOCs and was rich in aliphatic alcohols (e.g., 2-nonanol, 1-hexanol) and monoterpenes (e.g., nerol and geraniol). In addition, nine compounds (including nerol, geraniol, and linalool) correlated with the flower opening process. Tissue-specific VOC variation was also found in _L. caudata_. Compared with other isolated  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compounds** & **CAS Number** & **Formula** &
\begin{tabular}{c} **Regression** \\ **Equation** 1  & \(r^{2}\) (n = 3)** \\ \hline
2-Nonanol & 628-99-9 & C\({}_{9}\)H\({}_{20}\)O & y = 2.41 \(\times\) 10\({}^{7}\)x & 1.000 \\ Nerol & 106-25-2 & C\({}_{10}\)H\({}_{18}\)O & y = 1.41 \(\times\) 10\({}^{7}\)x & 1.000 \\ \(\beta\)-Citral 2  & 106-26-3 & C\({}_{10}\)H\({}_{16}\)O & y = 5.26 \(\times\) 10\({}^{6}\)x & 1.000 \\ (E)-Citral 3  & 141-27-5 & C\({}_{10}\)H\({}_{16}\)O & y = 8.44 \(\times\) 10\({}^{6}\)x & 1.000 \\ \(\rm{Linalool}\) & 78-70-6 & C\({}_{10}\)H\({}_{18}\)O & y = 6.70 \(\times\) 10\({}^{6}\)x & 1.000 \\ Citronellal & 106-23-0 & C\({}_{10}\)H\({}_{18}\)O & y = 6.29 \(\times\) 10\({}^{6}\)x & 1.000 \\ Citronellol & 106-22-9 & C\({}_{10}\)H\({}_{20}\)O & y = 6.15 \(\times\) 10\({}^{6}\)x & 0.999 \\ Geraniol & 106-24-1 & C\({}_{10}\)H\({}_{18}\)O & y = 1.36 \(\times\) 10\({}^{7}\)x & 1.000 \\ 2-Heptanol & 543-49-7 & C\({}_{10}\)H\({}_{16}\)O & y = 2.56 \(\times\) 10\({}^{7}\)x & 1.000 \\ 2-Nonanone & 821-55-6 & C\({}_{9}\)H\({}_{18}\)O & y = 1.81 \(\times\) 10\({}^{7}\)x & 0.998 \\ Phenylethyl alcohol & 60-12-8 & C\({}_{8}\)H\({}_{10}\)O & y = 2.84 \(\times\) 10\({}^{7}\)x & 0.999 \\ \(p\)-Anisaldehyde & 123-11-5 & C\({}_{8}\)H\({}_{8}\)O\({}_{2}\) & y = 2.37 \(\times\) 10\({}^{7}\)x & 0.998 \\ \hline \hline \end{tabular}  
* \(y\) is the peak area count and x is the concentration (ug mL\({}^{-1}\)) of each sample. 2 isomers of standard sample of 2,6-octadienal, 3,7-dimethyl-, (CAS number: 5392-40-5).  
\end{table}
Table 7: Basic information and calibration curve characteristics of 12 standards used.  
-floral parts, the stamen had the highest levels of total emissions. Our findings provide a theoretical basis for the development and utilization of _L. caudata_ and will exploit new routes for breeding varieties with pleasant odors.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/molecules28020478/s1](https://www.mdpi.com/article/10.3390/molecules28020478/s1)]([https://www.mdpi.com/article/10.3390/molecules28020478/s1](https://www.mdpi.com/article/10.3390/molecules28020478/s1)), Figure S1: Calibration curve of 12 standards used; Table S1: Volatile compounds emitted by _L. caudata_.  
Conceptualization, M.C. and Q.Z.; investigation, W.X. and Y.X.; formal analysis, W.X.; writing-original draft preparation, W.X.; writing-review and editing, M.C. and Y.X.; supervision, H.P. and Q.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (31500574) and the National Key R and D Program of China (2020 YFD1000502, 2019 YFD1001004).  
Not applicable.  
The authors are thankful to the Beijing Academy of Agriculture and Forestry Sciences, Beijing, China, for providing the GC/MS and to [PERSON] for the draft revision.  
The authors declare no conflict of interest.  
Samples of the compounds are available from the authors.