One of the possible ways to challenge selenium (Se) and iodine (I) deficiency in human beings is the joint biofortification of plants with these elements. Though the relationship between Se and I is highly pronounced in mammals, little is known about their interactions in plants where Se and I are considered not to be essential. Peculiarities of Se and I assimilation by a natural Se accumulator, such as Brassica juncea L., cultivar Volnushka, were assessed upon joint and separate plant foliar supply with sodium selenate (50 mg Se L-1) and potassium iodide (100 mg I L-1), in two crop seasons (spring, summer). Conversely to the individual application of Se and I, their joint supply did not stimulate plant growth. Separate use of sodium selenate enhanced I accumulation by 2.64 times, while biofortification with I increased the Se content in plant leaves by 4.3 times; this phenomenon was also associated with significant increase of total soluble solids and ascorbic acid content in leaves. The joint supply of Se and I did not affect the mentioned parameters. Both joint and separate application of Se and I led to synergism between these elements in: inhibiting nitrate accumulation; stimulating flavonoids biosynthesis (2⁻2.3 times compared to control plants) as well as Al and B accumulation; decreasing Cd and Sr concentrations. Plant biofortification with I increased the content of Mn and decreased K and Li. The consumption of 100 g Brassica juncea leaves provided 100% of the adequate human requirement of Se and 15.5% of I.
Keywords: Brassica juncea; biochemical characteristics; crop season; element composition; foliar biofortification; iodine; selenium.