## 3 Results  
### Celery Volatile Profile by HS-SPME/GC-MS  
The volatile compounds identified by HS-SPME/GC-MS in both celery petioles and leaves are reported in Table 1, together with the retention time (RT) and the mean relative (%) area of the detected volatiles in each variety. Twenty-two volatile organic compounds were identified, although only very few of them exhibited a relative peak area in the chromatograms greater than 1%; generally, eight compounds in the CC and WC samples and only five in the BC and WTC varieties. The 11 monoterenes found in celery aroma accounted for 90% or more of the total chromatogram provided by petioles and leaves, respectively. Among monoterenes, limonene was the most abundant compound in the cultivated celery varieties CC, WC and BC with a comparable content in leaves and petioles close to 50% of the total area. By contrast, \(\beta\)-myrcene was the most abundant one in WTC, reaching 46% of the mean total area in petioles and 69% in leaves, while the mean relative content of limonene in the wild form of celery was noticeably lower (about 23% in leaves and 38% in petioles) than that observed in the cultivated varieties. Concerning (Z)-\(\beta\)-ocimene, relatively high mean percentage areas were detected in the chromatograms of petioles (11-12%) and  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & \multicolumn{2}{c}{**CC**} & \multicolumn{2}{c}{**WC**} & \multicolumn{2}{c}{**BC**} & \multicolumn{2}{c}{**WTC**} \\ \hline
**RT (min)** & **Compound** & **Petioles** & **Leaves** & **Petioles** & **Leaves** & **Petioles** & **Leaves** & **Petioles** & **Leaves** \\ \hline
6.65 & \(\alpha\)-Thujene & \(0.96\pm 1.07\) & \(0.08\pm 0.02\) & \(1.00\pm 1.03\) & \(0.17\pm 0.13\) & \(0.51\pm 1.09\) & \(0.12\pm 0.46\) & \(0.09\pm 0.03\) & \(0.05\pm  
leaves (26-30%) of both CC and WC samples, while the observed relative peak areas were much lower in both petioles and leaves of BC (approximately 1%) and WTC samples (approximately 3%). As regards sesquiterpenes, we found five compounds but only three of them, \(\beta\)-caryophyllene and \(\alpha\)- and \(\beta\)-selinene, were unequivocally identified based on their mass spectra and retention times. The sum of the peak areas of the five sesquiterpenes reached 5% in CC leaves at most and was on average slightly higher in leaves (ca. 3%) than in petioles (ca. 2%). The most abundant sesquiterpene was \(\beta\)-caryophyllene, providing a relative peak area of 1-2% in the chromatograms collected from petioles and leaves of the cultivated varieties. Terpenes have a broad ecological role in plants ranging from defense from insects or herbivorous mammals to antifungal or attractant for pollinators, as well as inter and intra specific signaling. In the case of celery, it has been reported [29] that the repellent effect of this plant towards the whitefly _Bemisia tabaci_ depends on limonene and \(\beta\)-myrcene, that are the most abundant components in its volatile profile  
The aroma of celery can be described as fresh, herbal, woody and citrus and the major contributors to those olfactory notes are terpenes. However, although limonene is the predominant component of celery essential oil, the major contributors to celery aroma are the phthalides (for example sedanolide, sedanenolide and 3-n-butylphthalide), which are responsible for the peculiar celery herbal and spicy aroma and flavor. [30]. It must be underlined that under our experimental conditions requiring a sampling temperature slightly above the room temperature and a very short extraction time (35 \({}^{\circ}\)C and 5 min, respectively) only the most volatile compounds can be extracted by SPME. Therefore, in the volatile profiles we obtained the phthalide fraction was completely lacking. Nevertheless, our aim was a comparison of different varieties of celery based on their volatile profiles and not an exhaustive description of the celery aroma compounds.