Soybean responses to Azospirillum brasilense and plant regulators in drought conditions

The objective of this study was to evaluate the photosynthetic and productive responses of the soybean inoculated with A. brasilense, via seed and foliar spray application of foliar spray application of plant regulators, submitted to severe drought. For this we used a randomized block design with five treatments and five replications: irrigated control, drought control, A. brasilense seed with drought, foliar spray A. brasilense with drought and foliar spray plant regulators (auxin, gibberellin and cytokinin - AX+GA+CK) with drought. The evaluations performed daily and after rehydration consisted of: relative water content (RWC), soil gravimetric moisture (Ug) and gas exchange. In severe drought the chlorophyll a fluorescence was evaluated, and at the moment of maturation, the number of pods per plant and grains per pod, mass of 100 grains and production. RWC and Ug did not show variations between treatments maintained in drought. In the gas exchanges the foliar spray application of A. brasilense assisted in the maintenance of CO2 assimilation and increased the water use efficiency. In relation to the production the foliar spray application of A. brasilense or AX + GA + CK softens the losses in drought conditions. It is concluded that the use of A. brasilense foliar or plant regulators alleviates losses in production when the incidence of drought in the flowering period.