Enrichment of some leafy vegetables with magnesium

Two thirds of the world’s population do not consume the recommended amounts of magnesium (Mg). Hence, there is an increasing interest in producing plants enriched with this element. However, while designing any enrichment treatment, the effects of the amended supply of ions on the quantity, quality and safety of food products must be considered. Leafy vegetables are readily consumed and can be a promising source of Mg and antioxidants. An attempt has been made to evaluate the effect of enriching selected cultivars of lettuce (Romaine lettuce cv. Amadeusz and head lettuce cv. Omega) and endive (cv. Burundi) with Mg (40 – optimal, 80, 120 and 160 mg Mg dm-3) on the (1) concentration of Mg and other elements (K, Ca, Fe and Zn), and the impact of higher Mg concentrations on the (2) biomass accumulation, (3) efficiency of the photosynthetic apparatus, (4) level of reactive oxygen species (ROS), (5) activity of antioxidant enzymes and (6) the content of phenolic compounds. Although plants enriched with Mg had a higher concentration of Mg, they usually contained less Fe. The content of Mg in plants was sufficiently high for them to be considered as an alternative dietary source of this element, but the results varied from species to species. A higher concentration of Mg had a minor effect on the biomass accumulation and the efficiency of the photosynthetic apparatus, but significantly affected the generation of ROS and changed the activity of the examined antioxidant system’s components. These findings demonstrate that enrichment with Mg may simultaneously elevate levels of ROS, which must be taken into consideration prior to implementing any enrichment technology. Among the tested cultivars, endive cv. Burundi proved to be most suitable for Mg enrichment. Plants of this cultivar grown in the presence of Mg in concentrations up to 120 mg Mg dm-3 accumulated considerable amounts of Mg, without any negative side effects.