## 4 Discussion  
In this study, we identified a very high number of VOCs emitted by _Barlia robertiana_: considering all the analyzed samples, more than 100 compounds were identified. These results largely encompass the findings of our preliminary study [31]. As for VOC compositions, notably, in a study performed in Spain [32], [PERSON] et al. found \(\alpha\)-pinene, \(\beta\)-pinene, and limonene as the main components of the floral scent of _B. robertiana_. In our samples, instead, \(\alpha\)-pinene and limonene were detected, and only at low percentages, and they were not always present (Table 1), whereas \(\beta\)-pinene was found \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Calciano** & **Calciano** & **Potenza** & **Potenza** & **[PERSON] 2** & **[PERSON]. [PERSON] 2** \\ \hline
**Year of Sampling** & **2018** & **2019** & **2018** & **2019** & **2018** & **2019** \\ \hline
**Compound** & **r.t. [min]** & & & & **Area (\%)** & \\ \hline Tetradecane & 17.02 & & & & 0.96 & \\ \(\alpha\)-zingiberene & 17.09 & 2.63 & & 0.97 & & 0.94 & \\ Caryophyllene & 17.12 & & 1.74 & 0.32 & 6.75 & & 3.34 \\ \(\alpha\)-Bergamotene & 17.29 & & 0.64 & & & 0.50 \\ (Z)-\(\beta\)-Farnesene & 17.47 & & 1.77 & & 0.49 & 0.42 & 1.50 \\ Trans-Geranyl acetone & 17.50 & & 0.37 & & & & \\ Geranyl acetone & 17.52 & 0.21 & & 0.09 & & 0.37 & \\ _cis_-\(\alpha\)-bergamotene & 17.58 & 1.73 & & 0.67 & & 0.77 & \\ (\(E\))-\(\beta\)-Farnesene & 17.60 & & 14.22 & & & & 5.29 \\
2,6-bis(1,1- & & & & & & & \\ dimethylethyl)-2,5- & 18.11 & 0.19 & & & 0.63 & 0.64 & \\ cyclohexadiene-1,4- & & & & & & & \\ dione & & & & & & & \\ \(\beta\)-curcumene & 18.13 & 1.53 & & 0.31 & & 1.56 & \\ Longipinene & 18.40 & 3.86 & & 0.34 & & 4.40 & \\ \(\beta\)-Bisabolene & 18.42 & & 5.22 & & 2.00 & & 3.82 \\ Pentadecane & 18.49 & 0.79 & & & & & \\ \(\delta\)-selinene & 18.65 & 7.04 & & 1.37 & & 17.59 & \\ \(\beta\)-sesquiphellandrene & 19.35 & 0.91 & 1.98 & & 8.97 & & 24.95 \\ Hexadecane & 19.65 & & 0.35 & & 1.01 & & \\ Nerolidol & 19.73 & 0.33 & & & & 0.57 & \\ Ethyl dodecanoate & 19.93 & 0.67 & & & 1.10 & 0.33 & \\
2,3-Dihydrofarnesol & 21.08 & & & & & & 11.28 \\ Heptadecane & 21.29 & 7.41 & & & & & \\ Pristane & 21.68 & 35.57 & & & 22.57 & 9.61 & \\ Farnesol & 21.85 & & & & 19.36 & & \\ Farnesol & 22.04 & & 0.54 & & & & \\ Tetradecanoic acid & 22.5 & 0.30 & & & & & \\ Ethyl tetradecanoate & 22.58 & 12.40 & & 1.23 & & & \\ Dihydrofarnesol & 22.7 & 0.52 & & & & & \\
2,3-Dihydrofarnesyl & 22.76 & & & & 0.86 & & \\ acetate & 22.78 & & & & & & 0.90 \\ Isopropyl miristate & 22.78 & & & & & & 0.90 \\ Octadecane & 22.85 & & & & & 0.31 & & \\ pentadecanal & 23.02 & & & & & 0.27 & \\ Hexahydroarnesyl & 23.21 & & & & & 0.29 & & \\ acetone & 23.98 & 0.28 & & & & & \\ methyl hexadecanoate & 25.08 & 0.22 & & & & & \\ Eicosane & 25.39 & 1.36 & & & & & \\ \(i\)-propyl 14-methyl- & & 26.35 & & & & 0.57 & & \\ pentadecanoate & 26.4 & & & & 0.28 & & \\ \hline
**Number of compounds** & & **24** & **22** & **31** & **19** & **21** & **18** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._with even less frequency and lower percentages. On the other hand, the compounds that most characterize the plants from Italian populations have been not detected in the samples carried out in Spain or, therein, they were only present with very low values; this was the case with verbenone, for example. Considering the influence that analytical tools and sampling procedures may have on the results obtained from VOC analysis, we argue that most of detected differences in the floral scents of _B. robertiana_ are due to an intrinsic extreme capability of this species to vary its floral emissions, both qualitatively and quantitatively. At present, the data collected do not allow hypothesizing how much of this variability is under genetic control and how much depends on contingent environmental conditions.