*Article* **Morpho-Physiological and Biochemical Responses of Hydroponically Grown Basil Cultivars to Salt Stress**

**Michele Ciriello 1, Luigi Formisano 1, Marios C. Kyriacou 2, Petronia Carillo 3, Luca Scognamiglio 1, Stefania De Pascale 1,\* and Youssef Rouphael <sup>1</sup>**


**Abstract:** Depending on duration and magnitude, abiotic stresses interfere with plant metabolic processes and may severely impact developmental and qualitative attributes. In this study, in addition to characterizing three different cultivars of basil ('Anise', 'Cinnamon', and 'Lemon') grown under hydroponics, we appraised the impact of NaCl salt stress (60 mM) on morphophysiological and nutraceutical properties of the basil crop. Salt stress significantly reduced fresh yield (51.54%, on average) and photosynthetic parameters (ACO2, E, and gs) in all cultivars by raising tissue concentrations of Na+ and Cl−. In addition to reducing the concentration of nitrate (77.21%), NaCl salt stress increased the concentrations of key bioactive molecules, notably carotenoids (lutein and *β*-carotene), phenolic acids, and flavonoid derivatives, thus resulting in a higher antioxidant activity of salt-treated basil plants compared to the untreated ones. Analysis by UHPLC revealed that cichoric acid was the most abundant polyphenolic compound in all basil cultivars, with the highest values recorded in 'Cinnamon'.

**Keywords:** antioxidant capacity; bioactive molecules; carotenoids; flavonoids; osmotic stress; phenolic acids; secondary metabolites
