Nitrogen, carbon, oxygen and hydrogen are basic elements in organisms, forming an essential part of living matter. The main source of nitrogen for plants are ammonium and nitrate ions contained in soil. According to the amount of an individual mineral nutrient in plant dry matter, four categories of its influence on plant growth and evolution are described: deficiency, optimum, luxury and toxicity. In this work the influence of different doses of nitrogen (0.3-3.6 g per cultivation pot) on growth of spring barley (Hordeum vulgare L.) is studied. In addition, different ways of assimilation of atmospheric, nitrate and amide nitrogen are described. Attention is also paid to possible regulation of transport and nitrogen amount in plants.