The role of microelements B, Mn, Zn, Mo and Co in activity regulation of key enzymes of nitrogen and carbohydrates metabolism that determine quantity and quality of yield (sugar beet, soybean) has been studied in multiple experiments. The positive influence of microelements on the enzymes activity is better manifested under the humidity stress conditions. Some of microelements (B, Fe, Mn, Mo) promote the synthesis of osmotic active compounds in organs of grapevine (carbohydrates, aminoacids, organic acids), enhance the resistance of sunflower to the mushroom diseases. The use of microelements in complex with biologic active compounds is more effective for the plant resistance and productivity enhancement.