Efficiency Of Endophytic Bacteria On Nitrogen Uptake By Sunflower Plants.

Sunflower (Helianthus annuus L.) is widely cultivated for oil production. The growth microorganisms application has been studied as an alternative to minimize the use of chemical fertilizers, especially, nitrogen (N), reducing costs and risks to the environment. Endophytic bacteria isolated from sunflower plants were tested for their ability to N uptake. This study was carried out in greenhouse conditions in pots with four liters of capacity and five replicates, containing a mixture of vermiculite and sand (1:1) previously sterilized. The irrigation was made by capillarity. The plants received the Hoagland and Arnon solution with 30% of the N rate and inoculated with the isolates. The cultivar BRS 321 was used, and the treatments consisted of 21 bacteria isolates from the genus Bacillus spp., which compared with two controls without inoculation: i) full N rate (210 mg L^-1) and ii) 30% of the N rate (70 mg L^-1). Photosynthetic rate, SPAD unit, shoot dry weight, stem diameter, leaf area, N leaf content, and plant height were evaluated 40 days after sowing. All variables were higher in treatment without inoculated and full N rate (210 mg L^-1). When compared to the uninoculated control and 30% of N rate, only three isolates [CH (Bacillus cereus), RN (Bacillus cereus), and ZR (Bacillus megaterium)] increased the N leaf, accompanied by higher values of others variables studied. Excluding the variable N leaf content, the 16 isolates without N were higher than control with 30% of N for photosynthetic rate, SPAD unit, shoot dry weight, stem diameter, leaf area, and plant height. The results indicate that the use of these microorganisms can be an alternative to promote the sunflower plants growth of in soils with low N concentration.