## 3 Discussion
This is a relatively short period of time in comparison to the time that _Iris_ rhizomes collected for commercial purposes are usually being stored to produce significant amounts of irones, i.e., at least 2-3 years. For example, an analysis of the EO obtained from a 3-month-old rhizomes of a 3-year-old _1. forentina_ resulted in merely 4.21% of \(\alpha\)-irone and 7.88% of _trans_-2,6-\(\gamma\)-irone, while none was detected in the fresh rhizomes [41]. Keeping in mind that irone formation is generally considered to be a slow process lasting at least 2-3 years or longer [3], it is interesting to note that less than a month had passed between the collection of our first and last sample (Table 4). This indicates the possibility of a much faster conversion rate. However, the two remaining samples of _I. pseudopallida_ were harvested on the same day from two separate locations, and irones were found only in one of them. Therefore, the difference in sample collection can only partially explain the observed variations in irone contents. Other factors may also have influenced the irone production, such as the environmental conditions in which the plants were growing and the age of rhizomes before harvest. Based on the literature data, it is possible to assume that the relatively short period of storage of the samples analyzed in the present study was not enough for most of them to develop detectable amounts of irones, but they may be found in samples stored for a longer period of time. It was beyond the aims of the present work to account for various factors that could influence the irone production and VOC compositions in general. A separate study that would include more samples and/or their analysis at various time points in the future could be beneficial, in combination with different harvesting periods, keeping in mind that, in the present study, rhizomes were collected in April, while for commercial purposes, they are usually collected during July and August [4]. It would probably be more difficult to collect a much greater number of samples for each taxon if the plant material would need to be collected from the wild and would need to include underground parts of endemic taxa, which are not always easy to find and/or are not sufficiently represented for sampling. Therefore, an analysis of different taxa cultivated in the same botanical garden might be a better and more sustainable approach, which could also eliminate environmental factors contributing to the synthesis of iridals (irone precursors). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Taxon** & **Sample Code** & **Location** & \begin{tabular}{c} **Collection** \\ **Date** \\ \end{tabular} & **Latitude/Longitude** \\ \hline _Iris_ & _I. pseudopallida_ B & Bast & 28 April 2019 & \begin{tabular}{c} 43°19’58.4′′ N/ \\ 16°59′′2.4′′ E \\ \end{tabular} \\ _pseudopallida_ & _I. pseudopallida_ D & Dubrovnik & 7 April 2019 & \begin{tabular}{c} 42°39’36.4′′ N/ \\ 18°04′01.7′′ E \\ \end{tabular} \\ _I. pseudopallida_ T & Topici & 28 April 2019 & \begin{tabular}{c} 43°21’46.0′′ N/ \\ 16°57′28.4′′ E \\ \end{tabular} \\ \hline _Iris_ & _I. invlica_ V & Vir & 23 April 2019 & \begin{tabular}{c} 44°18′27.3′′ N/ \\ 15°17′52.5′′ E \\ \end{tabular} \\ _I. invlica_ Z & Zaton & 19 April 2019 & \
\begin{tabular}{c} 43°46′26.5′′ N/ \\ 15°50′10.8′′ E \\ \end{tabular} \\ \hline _Iris_ & _I. adriatica_ & Brač & 4 April 2019 &
\begin{tabular}{c} 43°21’30.3′′ N/ \\ 16°35′49.6′′ E \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Sample codes, harvesting locations, collection dates, and geographic coordinates for investigated _Iris_ taxa. Be that as it may, considering their commercial importance, it is of great interest to establish the amounts of irones in EOs obtained from _Iris_ rhizomes. HS-SPME was previously shown to be suitable for irone extraction [24].