## 3 Discussion  
The identification of VOCs of three species of the genus _Tillandsia_ was achieved through the use of the HS-SPME/GC-MS method. By using the CAR/PDMS fiber and two extraction methods with different values of extraction time and temperature developed in a previous study, the majority of the volatile compounds emitted by the flowers of _Tillandsia_ species were extracted efficiently. Indeed, it was shown that the CAR/PDMS fiber allowed to extract the maximum of volatile compounds from _T. xiphoides_ flowers compared to PDMS/DVB and DVB/CAR/PDMS fibers; moreover, considering the volatility of analytes  
Figure 4: Heatmap, the levels of each VOC in the three types of flowers were normalized in the range of \(-4\) to \(4\). Blue (\(-4\)) and yellow (\(4\)) represent the lowest and highest levels, respectively. affecting the optimal conditions of temperature and duration of extraction, it is necessary to use two extraction methods in order to trap the majority of volatiles emitted by _Tillandsia_ flowers [11]. After the GC-MS analysis, the profiles of the volatiles emitted by the flowers of the different species studied were compared qualitatively. This is the first time that a comparison of the VOCs emitted by different fragrant flowers of the genus _Tillandsia_ has been performed. The results showed a difference in volatile profiles between the flowers of the species _T. xiphioides_, _T. crocata_, and _T. caliginosa_. Indeed, the flowers of the two forms of _T. xiphioides_ present a profile of volatile compounds much more enriched in monoterepenes and sesquiterpenes, compared to the flowers of _T. crocata_ and _T. caliginosa_, which present relatively more similar profiles. This could be confirmed by a morphological difference but also by a difference in pollinator type between _T. xiphioides_ species and those of _T. crocata_ and _T. caliginosa_. Indeed, it is shown that _T. caliginosa_ and _T. crocata_ are morphologically closer--these species present the same types of foliage and flowers; moreover the old name given to _T. caliginosa_ is _T. crocata var. tristis_[17]. This difference in the composition of floral volatiles could also be confirmed by the attraction of different pollinators [18] for _T. crocata_, whose floral odor attracts Euglossine bees [15] and _T. xiphioides_, which is considered sphingophilous [19]. Indeed, it is shown that plants pollinated by the same ecological guild show similar visual and olfactory signals [20]. Even though it is not the only characteristic that can play a role in the attraction of pollinators, the floral odor constituted by a complex mixture of volatile compounds belonging to different chemical families plays a very important role in the stimulation and attraction of pollinators. These floral volatile compounds can be classified in the family of terpenoids, phenylpropanoids/benzenoids, and fatty acid derivatives, according to their biosynthetic pathways. Found predominantly in the flowers of both forms of _T. xiphioides_, terpenoids are derived from two precursors with five carbons isopentenyl diphosphate (IPP) and its allylic isomer dimethylallyl diphosphate (DMAPP) and represent the largest class of floral volatile compounds. The latter are synthesized in plants from two independent pathways: the mexulonic acid pathway, where synthesis is carried out in the cytosol, giving rise to precursors of volatile sesquiterpenes (C\({}_{15}\)); and the methyl-erythnitol phosphate pathway, where synthesis is carried out in the plastids mainly responsible of the formation of monoterepenes (C\({}_{10}\)) and volatileiterpenes (C\({}_{20}\)) [1]. Regarding the odor of this group of compounds, monotereponid hydrocarbons generally have a spicy and/or resinous odor, oxygenated monoterepenes have a sweet or citrus odor, and sesquiterpenes have a green and floral odor; however,iterpenes are rarely present in floral fragrances due to their low volatility [7]. Although close in the composition of floral volatiles, the two forms of _T.