Selenium (Se) is one of the elements that determine the normal functioning of an organism; it has antioxidant properties and protects the organism against the actions of free radicals and carcinogenic factors. Selenium is an element that fulfils an important physiological function (Kieliszek and Blažejak 2013), but apart from all the elements, selenium has one of the narrowest range between dietary deficiency (< 40 µg/day) and toxic levels (> 400 µg/day) (Fordyce 2007).While there is no evidence of Se need for higher plants, several reports show that when Se added at low concentrations, it exerts beneficial effects on plant growth. Se may act as quasi-essential micronutrient through altering different physiological and biochemical traits; thus, plants vary considerably in their physiological and biochemical response to Se (El-Ramady et al. 2016).During the last decade, studies related with strategies for Se biofortification in food plants for human nutrition have increased significantly because this metalloid is incorporated into human metabolism mainly as a constituent of food plants (Mora et al. 2015). Biofortification is defined as the process of increasing the bioavailable concentrations of essential elements in the edible portions of cultivated plants through agricultural management (fertilization) or genetic improvement (White and Brodlay 2005).Plant-derived foodstuffs, namely cereals, are the major dietary sources of Se in most countries throughout the world, even if Se contents are strongly dependent upon the corresponding levels in cereal-growing soils. Therefore, wheat is one of the staple crops that appears as an obvious candidate for Se biofortification, considering its Possibility of selenium biofortification of winter wheat grain

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Due to continuous single nitrogen fertilization, we hypothesized a built-up deficiency of micronutrients in crops that would limit plant growth and crop quality. In 2-year field experiments using urea-N fertilized grain maize (Zea mays L.), hybrid KWS 2376 at 0, 120 and 240 kg N ha (1 crop uptake of Zn, Mn, Cu and Fe was studied at DC 32, DC 61 and in the grain harvested. Micronutrient contents at DC 32 stage Á 1st node (aboveground phytomass) and DC 61 Á flowering (ear leaf) were all at levels indicative of adequate micronutrient supply to the crop. At both sampling occasions the Fe:Zn and Fe:Mn ratios were adequate implying that Fe did not inhibit the uptake of Zn and Mn. The application of nitrogen increased the Fe content at the 1st sampling in both years; in the second year the same was also the case for the Zn content. Nitrogen nutrition increased the contents of Mn and Fe at the 2nd sampling only in year 2; in the other treatments no changes were observed in the micronutrient contents. Micronutrient correlations in the grain were discovered between Zn and Mn contents and between Fe and Mn contents. In the second year the highest N-rate significantly increased the Fe and Zn content of the grain compared with the lower rates of nitrogen fertilization. Grain yields were not affected by the rate of nitrogen and ranged between 13.65 and 14.34 t ha (1 (1st year) and between 13.68 and 14.18 t ha (1 (2nd year). Nitrogen fertilization did not reduce the content of micronutrients in the plant or grain of maize. It is evident that the continuous single use of N fertilization so far has not resulted in a micronutrient deficiency of the plants limiting the nutrient density of the grain or reducing its quality.

The influence of application of increasing doses of selenium (0.05 mg, 0.10 mg and 0.20 mg/kg) into soil in pot experiments, with NPK fertilization of spring wheat (Triticum aestivum L., variety Banti), on the biomass yield (grain, straw, roots) and on selenium accumulation was observed. Selenium in the form of sodium selenite (Na 2 SeO 3 ·5H 2 O) and the NPK nutrients in the form of LAD-27, Ca(H 2 PO 4 ) 2 and KCl were applied. The average two-year results showed the expected indifferent effect of increasing doses of selenium on the yield of wheat grain, straw and roots. The differentiated doses of selenium into soil caused a significant increase of selenium content in dry matter (dm) of grain, straw and roots of wheat. The highest content of selenium (0.732 mg/kg in grain, 0.227 mg/kg in straw and 1.375 mg/kg in roots dm) was determined in the variant where 0.2 mg Se/kg of soil was applied. When applying the lowest dose of selenium (0.05 mg Se/kg of soil) the content of selenium was 0.155 mg Se/kg in grain. The selenium content in individual analysed parts of wheat was increasing in the following order: straw -grain -roots.

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