Caracterização de espécies paramagnéticas em sementes por ressonância paramagnética eletrônica

AUTOR(ES)

Viviane Maria Barbana

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

01/03/2012

RESUMO

Paramagnetic species were characterized in the seeds of radish wild, rice, mustard, wheat, oats, sorghum, sunflower, soybean, cotton, beans, maize and barley by EPR (Electron Paramagnetic Resonance). Some paramagnetic species present in the soil were also investigated, such as goethite, hematite, magnetite, and ferrihydrite. EPR experiments were performed at X-band microwave frequency (9.5 GHz) on the JEOL spectrometer (JES-PE-3X) at room temperature and 77K, using, in the last case, a thermal container (JES -UCD-2X) containing liquid nitrogen. Others experiments were made in temperature range of 132 to 385 K using a variable temperature controller (JES-VT-3A) coupled in the EPR spectrometer and flow of liquid nitrogen. The g marker MgO:Mn2+ (g = 1.981 in the fourth line) was maintained in the cavity of the EPR spectrometer, so that the data were obtained simultaneously with the samples spectra, which were introduced in quartz tubes of 4 mm. In EPR spectra, we detected the same complex of Fe3+ present in the goethite in g = 2.0 and in the seeds of radish wild, rice, mustard, wheat, oats, sorghum, sunflower, soybean, cotton, beans, maize and barley. Free radicals were detected with g = 2.004, in all the seeds, and g = 2.013, only on sorghum, at room temperature, the sunflower seeds showed the highest signal intensity of organic free radical with g = 2.004. By varying the temperature of samples from 132 to 273 K, the EPR spectra change just a little. But when the seeds and goethite were submitted at 77 K, their spectra changed dramatically, but similarly, appearing in lines g = 6.0 and g = 3.7, which are due to rhombic symmetry and higher symmetry than rhombic symmetry (but not in axial symmetry), respectively. Thus, these results confirm that the seeds have analyzed structures of Fe3+ similar to goethite.

ASSUNTO(S)

sementes - efeito da radiação minérios de ferro reações de radicais livres ressonância paramagnética eletrônica solos - teor de ferro seeds effect of radiation on iron ores electron paramagnetic resonance free radical reactions

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