Effects of the application of selenium nanoparticles on the physicochemical characteristics and the antioxidant system of purslane (Portulaca oleracea L.)

Purslane ( Portulaca oleracea L.) is a leafy vegetable rich in bioactive compounds; however, greenhouse cultivation often reduces its phytochemical content. In this study, the effects of the foliar application of selenium nanoparticles (Se-NPs) at different concentrations (0, 5, 25, 50, 250 and 500 mg L −1 ) on the physicochemical properties and antioxidant responses of purslane, grown under greenhouse conditions, were evaluated. Foliar application of Se-NPs at 5 mg L −1 was associated with increased levels of photosynthetic pigments and bioactive compounds, including total phenols, flavonoids, and ascorbic acid, as well as enhanced in vitro antioxidant activity, and with reduced oxidative stress markers including malondialdehyde and polyphenol oxidase activity. In contrast, higher Se-NP concentrations (250 and 500 mg L −1 ) were associated with reduced growth and stress-related responses, including increased activity of SOD, CAT, APx, and POD, indicating a dose-dependent response. Overall, the results identify 5 mg L −1 as an effective biostimulant dose for improving the nutritional and antioxidant quality of greenhouse-grow purslane, while documenting phytotoxic effects at concentrations ≥ 250 mg L −1 .