**5. Conclusions**

Despite the phylogenetic distance and significant differences in yield and quality, the three basil types ('Anise', 'Cinnamon', and 'Lemon') tested had similar responses to NaCl salinization. Specifically, salinized plants enacted adaptive stress responses mainly based on reduced photosynthetic activity and growth (total fresh weight, fresh leaf weight, height, number of leaves, leaf area, and total dry weight) but at the same time increased secondary metabolites, increasing their antioxidant properties. Specifically, as shown in Figure 8, salt stress modulated the production of polyphenolic compounds in a cultivar-dependent manner. Although the moderate tolerance of basil to salinity is noted several times, we can state that the use of 60 mM NaCl in the nutrient solution is limiting for the production of the basil tested. In any case, considering the interest of the cosmetic, pharmaceutical and perfume industries in secondary metabolites with bioactive action, the feasibility of using salt stress as an enhancer of such compounds could be explored.




**Figure 8.** Effect of salt stress on representative phenolic compound of 'Anise', 'Cinnamon', and 'Lemon' basil.

**Supplementary Materials:** The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/antiox11112207/s1, Table S1: Effect of basil cultivars (CV) and stress (S) on plant height, leaf number, leaf area, total dry weight, and total dry matter; Table S2: Effect of basil cultivars (CV) and stress (S) on leaf transpiration (E), leaf stomatal conductance (gs), CO2 net assimilation rate, and Chlorophyll fluorescence (Fv/Fm).

**Author Contributions:** Conceptualization, M.C., S.D.P. and Y.R.; methodology, M.C. and L.F.; software, M.C. and L.F.; validation, M.C. and L.F.; formal analysis, M.C. and L.F.; investigation, M.C. and L.F.; resources, S.D.P. and Y.R.; data curation, M.C. and L.F.; writing—original draft preparation, M.C. and L.F.; writing—review and editing, M.C., L.F., M.C.K., P.C., L.S., S.D.P. and Y.R.; visualization, S.D.P. and Y.R.; supervision, S.D.P. and Y.R.; project administration, S.D.P. and Y.R.; funding acquisition, S.D.P. and Y.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The datasets generated for this study are available on request to the corresponding author.

**Acknowledgments:** We would like to acknowledge Alberto Ritieni and Giulia Graziani for providing the access to HPLC-DAD and UHPLC facilities and analysis. The authors are also grateful to Christophe El-Nakhel and Daniele Capurso for technical support in the field experiment.

**Conflicts of Interest:** The authors declare no conflict of interest.
