Peculiarities of the formation and functioning of soybean-rhizobial complexes and the productivity of soybean culture under the influence of retardant of paclobutrazol


V.G. Kuryata, L.А. Golunova

The effect of triazole derivative retardant of paclobutrazol on the formation and function of soybean-rhizobial complex, activity of key ferments of nitric metabolism-nitrogenase and nitratereductase, morphogenesis and photosynthetic apparatus of soybean plants in connection with the productivity of the culture have been established. The inoculation of bacteria of seeds with highly effective strain M 8 Bradyrhizobium japonicum followed by treatment of the plants with antigibberellic preparation of paclobutrazol during budding caused essential anatomic-morphological and physiological changes in function of the source-sink system optimized the formation and function of bean-rhizobial complexes. Since the intensity of symbiotic nitrogen fixation is considerably dependent on the process of photosynthesis application of the retardant proved to be effective, for it was followed by increase of leaves in number and in their total area per plant as a result from the stem branching. The simultaneous application of paclobutrazol caused the formation of a more powerful mezostructure of the leaves due to the enhanced development of the main photosynthetic tissue – chlorenchima, per unit of the leaf area. Thus the application of paclobutrazol tended to bring into action the more developed of source spheres of the plants which provided with assimilates symbiotic nitrogen fixation as well as processes of carpogenesis. The result obtained in the research testify to the steady trend towards the formation of bean-rhizobium complexes: under the effect of retardant the number and weight of tubers on the roots of the inculcated plants increased. The analysis of the nitrogen-fixing activity of the tubers shows that under paclobutrazol there was a significant increase of the nitrogen activity of bean-rhizobial complexes, which occurred, evidently, also due to more intensive absorption of assimilators in consequence of photosynthetic intensification of plant productivity. Along with generative organs bean-rhizobial complexes serve as supplementary traction centres for the redistribution of products of photosynthesis. One of the important factors which influenced the formation of plant productivity was that to enhance the assimilate assurance of the processes of symbiotic nitrogen fixation causing a shift of nitrogenase activity towards a later stage of ontogenesis - the green bean phase. Beside the assimilation of free nitrogen, due to the nitrogen activity of the tubers, a part of nitrogen was consumed by plants from the soil in the nitrate form, which dominated the bound forms of nitrogen. The analysis of the obtained data testifies to the use of paclobutrazol preceded by inoculation of soybean seeds with strains M 8 Bradyrhizobium japonicum which provided growth activity of nitratereductase both in roots and in leaves of soybean plants. We found out that the highest activity of nitrate reduction with mutual use of strain and retardant occurred in the period of blossom. Thus, the application of paclobutrazol against the inoculation background with strains M 8 brought into effect a considerable growth of nitrogen reduction activity both in the leaves and in the roots in comparison with the absolute control (spontaneous inoculation), and which efficiently enhanced the nitrogen metabolism of plants. To sum up, the complex application of paclobutrazol after inoculation of the seeds with strain M8 Bradyrhizobium japonicum proved to be the efficient cause of stem branching as well as growth of beans in number and their crop productivity due to the formation of a more powerful photosynthetic apparatus and more essential redistribution of nitrogene in the plants.

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