Enzymatic activity, gas exchange and production of soybean co-inoculated with Bradyrhizobium japonicum and Azospirillum brasilense

Abstract

Soybean occupies a prominent place in the national scenario, and the search for new technologies is continuous. Thus, this study aimed to evaluate the co-inoculation, through seeds, from diazotrophs bacteria of genus Bradyrhizobium japonicum and Azospirillum brasilense, and its effects against the nodulation, enzyme activity, gas exchange, and soybean production. The experiment was conduced in completely randomized design, with seven treatments and four replications. Seven treatments were constituted in the control (no nitrogen fertilization and seed inoculation); application of N mineral; seed inoculation with B. japonicum and A. brasilense AbV5+AbV6 and AbV5+AbV6+AbV7 strains and their co-inoculations. The evaluations were performed in V4 and R4 stages, with particular biometric characteristics of shoots and roots, the gas exchange indices of the leaves and the activity of peroxidase and phenylalanine ammonia lyase enzymes. Also in the R9 stage were determined components of production and production per plant culture. The results indicate that, when combining two species of bacteria through seeds have limitation in nodulation. The A. brasilense, strains AbV5+AbV6+AbV7, inoculated through seed promotes increase in nodulation from the natural soil population; it still raises the activity of plant defense enzymes in V4 stage, however, reduces the photosynthetic rate per foliar unit. Nitrogen fertilization, seed inoculation with B. japonicum, A. brasilense (AbV5+AbV6+AbV7) and A. brasilense (AbV5+AbV6+AbV7) + B. japonicum, provide the highest yields per plant. It has been observed even though the dry mass of root and aerial part have a direct influence on plant production, and a negative relation between stomatal conductance and the number of nodules in the growing season, and that photosynthesis does not influence the plant's production, just its production factors.