Physiological responses of Urochloa ruziziensis inoculated with Azospirillum brasilense to severe drought and rehydration conditions

Abstract

This study evaluated the tolerance of U. ruziziensis under severe water stress conditions and its recovery when rehydrated, based in responses of relative leaf water content and gas exchange of the crop. The experiment was conducted in green house in Oxisol. The experimental design was a randomized block design, totaling five treatments, was represented by inoculation of A. brasilense strains AbV5 + AbV6, as follow: seed inoculation, foliar spray application, seed inoculation + foliar spray application, a non-inoculated control with water deficit treatment and a irrigated control without inoculation. Drought was imposed 45 days after sowing, after the vessel was irrigated until saturation of the substrate, by total removal of irrigation for six days, and evaluated three days after the resumption of water, evaluating gravimetric soil moisture, relative leaf water content and gas exchange. Soil moisture showed non variation to treatments non irrigated, but the relative leaf water content was lower in the control without water. The control and the treatment inoculated with A. brasilense in seeds exhibited lower rates of gas exchange. Recovery full of photosynthetic activity occurred three days after rehydration in all treatments. A. brasilense foliar sprayed is efficient to increase the tolerance of U. ruziziensis to water deficit and presented higher photosynthetic rates even under conditions of severe water deficit.