The Impact of Salinity on Growth, Physio-Biochemical Characteristics, and Quality of Urospermum picroides and Reichardia picroides Plants in Varied Cultivation Regimes

Salinity stress is severely affecting modern horticulture and puts food security under threat for current and future generations. The aim of the present study was to evaluate the effect of saline conditions (three salinity levels: 2.0, 5.0 and 10.0 dS m(-1)) on the growth, physiological processes and quality of two wild edible species (Urospermum picroides and Reichardia picroides) grown under three different cropping systems (pots indoors (GP) and outdoors (FP); and floating hydroponics (FH)). Our results indicate that high salinity affected growth parameters in all the studied cropping systems in the case of U. picroides, whereas R. picroides was not affected only when grown in pots outdoors. Moreover, total soluble solids content and titratable acidity in both species were not affected by high salinity for any of the cropping systems, except for in the case of FP system. Similarly, carotenoids content decreased under high salinity when both species were grown in the FP system. A varied effect was recorded for total phenolic compounds content in response to salinity levels, although the FP system resulted in considerably higher phenolics accumulation in both species, while proline content increased when plants were subjected to high salinity, regardless of the cropping system. The antioxidant activity also varied among the studied treatments for both assays (TEAC and FRAP), although cultivation outdoors in pots resulted in considerably higher values compared to the other systems. Finally, nitrate content showed decreasing trends with increasing salinity in plants grown in the GP (both species) and FP system (only U. picroides), whereas no significant differences in physiological parameters in comparison to the control treatment were recorded, except for the stomatal conductance (FP and GP system) and transpiration rate (FP) of R. picroides plants. In conclusion, it seems that the tested plant species responded differently to the salinity treatments but they both displayed a lack of severe stress even at high salinity.