Azospirillum brasilense, pseudomonas fluorescens e auxina contribuem no metabolismo foliar e desenvolvimento da soja?

Abstract

Coinoculation with Azospirillum brasilense and Pseudomonas fluorescens may be a promising practice for obtaining high soybean yields. Furthermore, the use of phytohormones such as auxin can assist in leaf metabolism and plant development. We aimed to evaluate the effect of coinoculation of A. brasilense and P. fluorescens and the application of auxin on the photosynthetic metabolism and development of soybean plants. The coinoculation methods were as follows: CK, inoculated only with Bradyrhizobium spp. (without coinoculation), while the other coinoculation methods used Bradyrhizobium spp. and a commercial source containing A. brasilense and P. fluorescens, arranged as follows: APs, coinoculation with A. brasilense and P. fluorescens via seed; APf, coinoculation via foliar at stage V3 and APs+f, via seed + via foliar, all associated or not with foliar application of auxin at stage V4. At 36, 40 and 44 days after sowing (DAS) the photochemical aspects and gas exchange were evaluated, and at 49 DAS we evaluated the development characteristics of biomass production of leaves, branches, nodules and roots. The application of auxin had little influence on photochemical yields, while the best values of photochemical activities in the reaction centers of photosystem II occurred in plants co-inoculated with APs+f. In general, the best results in photosynthesis, carboxylation efficiency and water use occurred with APf and APs+f coinoculation. Developmental responses depending on coinoculation methods vary with auxin application. We observed that the application of auxin contributed positively to the leaf area and biomass production of leaves, roots and nodules. Coinoculation with APf and APs+f favored the earlier emission of flowers and a greater number of pods. The effects of the methods and application of auxin vary with the evaluation periods. It was concluded that coinoculation with A. brasilense and P. fluorescens via seed + foliar and the application of auxin contributes positively to the photosynthetic metabolism and development of soybean plants.