## 5 Discussion  
The VCs of laurel are a mixture of various compounds, also known as secondary metabolites, with a peculiar taste, useful in modern industry including the pharmaceutical, tobacco, food industries [41] and plant protection against insects and pathogens [42]. EO content and composition are known to be affected by environmental conditions including physical and chemical characteristics of soils [43; 44; 45], and macronutrient and micronutrient contents of soils [46; 47; 48]. In this study, the effects of different concentration of salt on the composition of the VC extracted from the leaves of laurel were investigated. The analysis revealed that 1,8-cineole, \(\alpha\)-terpenyl acetate and methyl eugenol are the main components, with other compounds being present at lower and different percentages or even in traces. This is in accordance with various experimental studies: [PERSON] et al. [29], for instance, found that 1,8-cineole is the major component in the leaves EO of laurel. Many constituents of laurel EOs have different and important utilizations. 1,8-Cineole, in particular, is widely used in the preparation of pharmaceuticals. It is also used as a local anesthetic and disinfectant in the treatment of inflammation and for inducing sputum and lowering blood pressure [49]. Under salt stress, the composition of VC of several species was modified. [PERSON] et al. [50] demonstrated that stresses caused by abiotic environmental factors such as salinity as well as drought can have a prominent effect on the chemical plasticity of the EO composition of medicinal herbs. In fact, salt stress affected EO composition of _Matricaria chamomila_[51], _Melissa officinalis_[52], _Calendula officinalis_[53] and _Mentlu piperita_[54]. Significant correlations were observed between salt concentrations and major EO components of _Mentlu piperita_[10]. Accordingly, our results indicate that the compositions of VC are modified in moderate and high salinity. Particularly, we noted that major compounds are significantly affected by salinity (Table 1). The relative amount of 1,8-cineole decreased with increasing salt concentration and achieved lower values at 100 mM NaCl. Similar results were observed in _Rosmarinus officinalis_ by [PERSON] et al. [55], as the relative content of 1,8-cineole decreased with the increase of the NaCl level. Additionally, [PERSON] et al. [56] showed that geranyl acetate and geraniol were the main components of _Dracocophanum moldavica_ EO and with increasing salinity, the relative amount of these two compounds decreased significantly. Comparable effects were reported in _Mentlu Piperita_ grown under salt stress by [PERSON] et al. [57], who found a decrease in its VCs. As can be seen in Table 1, for the others predominant components, we observed that with increasing salinity their relative amount was also significantly affected. \(\alpha\)-Terpenyl acetate increased in percentage with increasing NaCl concentration. We also noted that salt stress increased methyl eugenol in comparison to the control and this was more pronounced at 100 mM NaCl. According to [PERSON] et al. [58], these variations may be explained by the induction of the specific enzymes involved in the biosynthesis of the later compounds by salt stress. Accordingly, [PERSON] and [PERSON] [33] revealed that variations in EO composition could be due to its effect on enzyme activity and metabolism improvement. It has been highlighted the important biological role of EOs against plant pathogens and even in plant-to-plant interaction [59; 60; 61], but it is not clear if they are involved in plant adaptation to environmental abiotic stresses. Various studies have suggested that 1,8-cineole has an inhibitory effect on germination and early development of plants [29; 62]. It has been also hypotized that an increase of these substances might reduce water losses and leaf temperature [59].