## 3 Discussion
For instance, pollutants present or accumulated by plants may affect their emission of VOCs and how pollinators react to this phenomenon. The emission of VOCs can be different depending on the action the plant needs. Thus, VOCs could be emitted as inhibitors of bacterial growth or to reduce the threat of herbivores such as insects and larvae [34]. One of the functions of the emission of VOCs from a flower's plant is the attraction of pollinators. Pollinators like hummingbirds, bats, moths, and bees are known in the _Tillandsia_ genus [35; 36; 37]. Their attraction is most of the time very specific [11]. Consequently, emission of VOCs from scentless flowers as the ones studied here can have an ecologicalrole like pollinators attractors, together with the shape and color of the scentless flowers. The eight major compounds identified in the _Tillandsia_ species (except _T. palacea_ and _T. bandensis_) were, for most of them, not identified in our previous study conducted by [PERSON] et al. [26; 27]. Only benzaldehyde (22) and benzacetaldehyde (24) were previously identified, meaning that these compounds might be specific to the scentless or faint-scented species of the _Tillandsia_ genus or were not detected in our previous study because they were minor. This difference in the composition of volatile profiles could also be confirmed by the attraction of different pollinators [38; 39; 40]. Indeed, hummingbirds are more attracted by non-scented or faint-scented flowers [41]. Among the volatile compounds identified here, 8 of them are present in the majority of the 14 species and nonanal (49) was identified in all the species. In comparison, two of the eight compounds were identified in our previous studies (benzaldehyde (22) and benzacetaldehyde (24)). Nonanal (49) isolated from plants has already been studied from _Solanum lycopersicum_ for its anti-fungal activity against _Penicillium cyclopium_ and from _Artemisia ludoviciana_ for anti-diarrheal activity [42; 43]. Other aliphatic aldehydes were identified in this study such as hexanal (43), heptanal (44), octanal (47), decanal (51), 2-heptanal (45), 2-octenal (48), or 2-nonenal (50), for instance. Some of these aliphatic aldehydes were already studied for their in vitro antibacterial activity from _Olea europen L_. [44]. Last but not least, some of these aldehydes such as nonanal (49), octanal (47)--but also other compounds isolated in this study like 3-hexen-1-ol (39) and methyl salicate (28)--were also studied for their plant-insect interaction and appeared to have a good attraction power for beneficial insects [45]. Usually, aldehydes are often known for their contribution to the aroma and taste of fruits or plants [46]. 2-pentylfuran (59) has also been identified in 10 of the 14 _Tillandsia_ species studied here. This compound is described in the literature to be a repellent of _Drosophila suzukii_ in order to avoid the use of insecticides [47]. Consequently, the emission of 2-pentylfuran (59) by 10 of the _Tillandsia_ species studied here could be linked to a repellent activity. In the same way, benzaldehyde (24), a well-known volatile compound, was identified in this study and has been described for its herbicidal activity from _Melaleuca aajputti_[48].