o:3116 Development, physiology and anatomy of soybean root nodles Razvoj, fiziologija i anatomija nodula na korenu soje en Abstract: The exceptional ecological and economic importance of soybeans is that, as a nitrogen-fixing plant, it has the ability to convert atmospheric nitrogen into an ammonia form available to plants. The process takes place on soybean roots in nodules that are formed in the symbiosis of the plant and bacteria from the genus Bradhyrhizobium japonicum. The contact between the plant and the bacteria begins with the excretion into the soil of various types of polyphenols (isoflavones), signal compounds that attract the bacteria. After the diffusion of isoflavones through the bacterial membrane, the Nod factor of the bacteria is activated, i.e. of lipochitooligosaccharides with which the bacterium infects the root hair. After infection, the formation of a nitrogen-fixing nodule begins, in which all metabolic processes are under the complete control of the plant. Biological fixation in the nodule is carried out by the enzyme nitrogenase under anaerobic conditions. Together, the plant and the bacteria create the compound leghemoglobin, which binds oxygen and enables the creation of anaerobic conditions that favor the nitrogenase enzyme for the nitrogen fixation process. Also, leghemoglobin gives the active nodule a red color on cross-section. The anatomical structure of the active nodule is represented structurally by three different zones. The largest zone is the central part, i.e. tissue infected with bacteria (rhizobium field), and the inner bark (cortex) and the outer bark (external cortex) rest on it. The first nodules begin to carry out nitrogen fixation in the stage of soybean development “two trefoils” (V2) or “three trefoils” (V3), so that the largest number of active nodules would be in the phenophase “the beginning of seed formation” (R5). Average nodule activity lasts 30 to 40 days. There is a lot of scientific knowledge about these processes, but there is still a lot of room for improvement elucidating the relationship between the soybean plant and bacteria Bradhyrhizobium japonicum, all in function of the benefits they bring to agricultural production. soybean, nodul, isoflavones, nitrogen fixation, Bradhyrhizobium japonicum 1552100 978-86-87109-17-9 2023-10-23T12:18:22.078Z 44 no 46 Vladimir Miladinović Institute of Soil Science 0000-0001-7394-0173 46 Vladan Ugrenović Institute of Soil Science 0000-0001-6642-8235 46 Elmira Saljnikov Institute of Soil Science 0000-0002-6497-2066 46 Tara Grujić Institute of Soil Science 0000-0002-0122-6402 46 Nikola Koković Institute of Soil Science 0000-0002-0366-916X 46 Dušica Delić Institute of Soil Science 0000-0002-0626-0482 application/pdf 68375 https://unilib.phaidrabg.rs/o:3116 no yes 1 70 92000004 71A05 X SYMPOSIUM OF THE SERBIAN ASSOCIATION OF PLANT BREEDERS AND SEED PRODUCERS AND VII SYMPOSIUM OF THE SERBIAN GENETIC SOCIETY SECTION OF THE BREEDING OF ORGANISMS 2023