Efeitos de ácidos húmicos e óxido nítrico no crescimento e metabolismo de raízes transformadas de manjericão (Ocimum basilicum L.)

Abstract

A study carried out of chemical and spectroscopic characterization in humic acids extracted from soils (AH1-Red-Yellow Latosols (Oxisols); AH2-Haplic Chernosol and AH3- Haplic Organosols (Histosols)) (Experiment 1) to verify the difference between these humic acids. Subsequently an experiment was performed (Experiment 2), to evaluate the parameters of growth of transformed roots of sweet basil (Ocimum basilicum L.) treated with the humic acids extracted from different soils and with sodium nitroprusside (SNP) as a donor of nitric oxide (NO) at doses of 0, 1, 2, 3, 4 and 5 mM Carbon L-1 and 0, 0.1, 10, 50, 100 and 200 μM SNP L-1 medium, respectively, with assessments conducted in the assembly, 5 and 15 days of experiment. It was found that the dose of carbon 3mM L-1 for the humic acids and the dose of 100 μM SNP L-1 (nitric oxide) were the doses provided the best responses in growth parameters. With the results of this study were mounted two more tests, the first (Experiment 3), to evaluate the nitrogen metabolism, the responses of proton pumps, catalase activity and NO histolocalization and reactive oxygen species (ROS) in vivo in roots transformed basil, collected at 5 and 15 days after installation of the experiment. The second trial (Experiment 4) was to evaluate the NO and ROS histolocalization in vivo, and the activity of important enzymes involved in the growth and nutrient uptake, and this essay collected six hours after treatment. The roots were treated with two concentrations of nitrate, a low dosage of N-NO3- (0.5 mM) and high (5.0 mM) were added in which the bioactive substances (AH3-3mM Carbon L-1 and 100 μM SNP L-1). In all parameters evaluated root growth, the treatments with humic acid and nitric oxide showed higher growth compared to control. Moreover, the evaluation of the parameters of nitrogen metabolism in the two tested doses of N-NO3- bioactive substances provided with increased enzyme activities and nutrient content, compared to controls, especially at the lower dose of N-NO3 -. It is a consensus among scientists that the bioactivity of humic acid is mainly related to the presence of molecules similar to auxin and possibly other hormones. The generation of nitric oxide in plants is related to root growth and this growth can be provided by endogenous production of auxin by application of synthetic auxin analogs or application of humic acids. Thus the signaling of nitric oxide may be related to the bioactivity of humic acids. These effects were evidenced by the increase of root growth, uptake N-NO3 - of -activation of H+-ATPase plasma membrane in transformed roots of basil. Similarly, we observed increased activity of catalase, an enzyme related to root growth, by providing the dismutation of hydrogen peroxide produced in the processes of cell differentiation and expansion as well as to detect ROS in vivo, increased in treatments with bioactive substances. With the results in this thesis can give the use of humic acids may serve as a biotechnological tool in the production of biofertilizers fertilizers, for growing plants in soils of low fertility and also as components in the production of inoculants of beneficial microorganisms.