Enhancing Nutritional and Functional Properties of Hydroponically Grown Underutilised Leafy Greens Through Selenium Biofortification

Nutrient intake is vital for human health, yet micronutrient deficiencies remain widespread despite sufficient calorie consumption. Biofortification is the process by which the nutrient density of food crops is increased through various strategies without altering key agronomic characteristics. This approach is widely recognised as a cost-effective method for addressing micronutrient malnutrition. When combined with the nutritional properties and inherent resilience of underutilised crops to harsh conditions, biofortification emerges as highly promising and sustainable solution. This study investigates the effects of selenium biofortification by adding different doses of SeO₂ (0, 1, 2, and 4 μM) in the nutrient solution in three underutilised leafy vegetables [<i>Portulaca oleracea</i> L. (purslane), <i>Taraxacum officinale</i> L. (dandelion), and <i>Mesembryanthemum crystallinum</i> L. (iceplant)] grown in an open soilless system. The addition of SeO₂ to the nutrient solution increased yield in all three species, although iceplant exhibited reduced yield at the highest SeO₂ dose. In particular, the total yield of purslane was enhanced by 14-19% when treated with 1, 2, and 4 doses of SeO₂, whilst the dandelion yield increased by 25% under 4 μM SeO₂. Furthermore, the yield of iceplant increased by 14.7-17.8% at 1 and 2 μM SeO₂. SeO₂ application led to a dose-dependent increase in selenium concentration in the shoot tissues while remaining within safe intake limits. More specifically, selenium concentration in purslane, dandelion, and iceplant tissues increased by 92%, 91%, and 89%, respectively, at the highest SeO₂ dose (4 μΜ) compared to untreated plants. Selenium treatment also influenced the nutritional profile of the examined plant species. With regard to the antioxidant activity, the highest recorded value was observed at 1 μM SeO₂ for purslane and iceplant, and at 4 μM SeO₂ for dandelion. These values were enhanced by 20%, 12%, and 27%, respectively, in comparison with 0 μM SeO₂. In conclusion, rootzone SeO₂ supplementation via a nutrient solution can be considered an effective biofortification strategy that enhances growth characteristics and antioxidant properties of the three investigated underutilised leafy vegetables without compromising their nutritional value.