Morphophysiological responses of soybean seedling to bioinputs based on Bacillus spp.
Abstract The high demand for soybeans in Brazil requires seeds with high physiological quality, enabling the establishment of vigorous seedlings. Abiotic stresses can limit seedling development. In this context, bio-inputs based on Bacillus spp. have stood out, acting in the promotion of root growth, nutrient availability, and induction of resistance. Thus, the objective was to evaluate the action of a commercial bio-input based on Bacillus spp. bacteria on the physiology of soybean seedlings. The bio-input was inoculated in sand substrate in trays, at concentrations of 0 (distilled water); 50; 100; 150 and 200 µL. Two hundred seeds were sown per treatment, with 4 repetitions. The emergence of soybean seedlings, length and dry mass, as well as gas exchange, chlorophyll a fluorescence, and anatomical and histochemical analysis of the leaves were analyzed. Doses between 100 and 150 µL were able to improve seedling performance, length, and biomass. All doses of the bio-input provided ideal values of potential quantum yield of PSII (Fv/Fm), close to 0.83, reaching a maximum at the estimated dose of 132.07 µL, with a peak of 0.77. The leaves of seedlings treated with the bio-input showed greater xylidine staining, indicating an increase in protein compounds and, consequently, expansion of intercellular spaces in the spongy parenchyma, in contrast to the control group, which showed less xylidine staining. Furthermore, a strong positive correlation was found between the potential quantum yield of PSII (Fv/Fm) and growth variables, including emergence (EM), shoot length (CA), root length (CR), shoot dry mass (MA), and root dry mass (MR). The bio-input was able to stimulate the initial growth of soybean seedlings, mainly at concentrations of 100 to 150 µL, although further studies are needed to validate its action under real cultivation conditions.