Response of Aeroponically Cultivated Baby-Leaf Lettuce (Lactuca sativa L.) Plants with Different Zinc, Copper, Iodine, and Selenium Concentrations

Abstract

Over two billion people worldwide suffer from micronutrient deficiencies. Biofortifying vegetables can enhance micronutrient intake through the diet. This study assessed the biofortification of indoor-grown baby-leaf lettuce using aeroponics. Four experiments, two each, were conducted by adding different concentrations of Zn (from 10 to 450 µM) or Cu (from 3 to 250 µM) into a nutrient solution. A fifth experiment was conducted by simultaneously adding to the nutrient solution the optimal concentration of I (5 µM) and Se (13 µM), chosen on the basis of previous works, and the optimal concentration of Zn (250 µM) and Cu (150 µM), chosen on the basis of the results obtained in the first four experiments. Leaf biomass, mineral concentrations, chlorophylls, carotenoids, phenols, flavonoids, nitrates, and antioxidant capacity were measured 21 days after transplanting. Higher concentrations of Cu, Zn, I, or Se in the nutrient solution led to an increase in their concentrations in lettuce leaves, without affecting the growth or leaf quality of lettuce plants. The simultaneous application of I with the other elements induced a higher accumulation in leaves compared to when I is applied alone. One hundred grams of lettuce leaves biofortified with Se, I, Cu, and Zn would provide the 6.1%, 35.3%, and 263.0% of Adequate Intake for Cu, Se, and I, respectively, and 4.5% of Population Reference Intake for Zn. Our results suggest that simultaneously biofortifying baby-leaf lettuce with these four minerals is a practical and convenient way to integrate these micronutrients into the diet without reducing the yield or quality of lettuce.