RESUMEN
BACKGROUND AND AIMS: The objective of this research was to characterize the physiology and cell ultrastructure of two soybean genotypes subjected to nutrient solutions with increasing concentrations of manganese (Mn) at two contrasting iron (Fe) concentrations. Genotypes 'PI227557' and 'Biloxi' were selected based on their distinctly different capacities to accumulate Mn and Fe. * METHODS: Bradyrhizobium-inoculated plants were grown in hydroponic cultures in a greenhouse. Nutrient solutions were supplied with Mn concentrations ranging from 0.3 to 90 microm, at either 5 or 150 microm Fe as FeEDTA. * KEY RESULTS: For both genotypes and at both Fe concentrations, Mn concentrations from 6.6 to 50 microm did not affect shoot, root and nodule mass, or leaf and nodule ureide concentration. Mn concentrations of 70 and 90 microm did not result in visible toxicity symptoms, but hindered growth and nodulation of 'Biloxi'. An Mn concentration of 0.3 microm was, however, deleterious to growth and nodulation for both genotypes, and caused an accumulation of ureides in leaves and major alterations in the ultrastructure of chloroplasts, nuclei and mitochondria, regardless of the Fe concentration. In 'PI227557', there was also a proliferation of Golgi apparatus and endoplasmic reticulum in the cytoplasm of leaf cells, and nodules showed disrupted symbiosomes lacking poly-beta-hydroxybutirate grains concomitantly with a proliferation of endoplasmic reticulum as well as arrested bacterial division. At 15 microm Fe, ferritin-like crystals were formed in the lumen of chloroplasts of 'PI227557' plants. For both genotypes, there was an antagonism between the Fe and Mn concentrations in leaves, the higher values of both microelements being detected in 'PI227557'. The absence of any detectable relationship between Fe or Mn and zinc, phosphorus and copper concentrations in leaves ruled out those micronutrients as relevant for Mn and Fe nutrition in soybeans. * CONCLUSIONS: The results confirmed the greater capacity of 'PI227557' for Mn and Fe accumulation than 'Biloxi' for most nutrient treatments. Hence, 'PI227557' may be a very useful genetic resource both in developing soybean cultivars for growth on low nutrient soils and in physiological studies to understand differing approaches to nutrient accumulation in plants.
Asunto(s)
Glycine max/genética , Glycine max/fisiología , Hierro/fisiología , Manganeso/fisiología , Bradyrhizobium , Clorofila/metabolismo , Genotipo , Hidroponía , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/ultraestructura , Raíces de Plantas/crecimiento & desarrollo , Brotes de la Planta/crecimiento & desarrollo , Glycine max/crecimiento & desarrollo , Glycine max/ultraestructuraRESUMEN
A Revisão Sistemática de Literatura (RS) constitui em importante instrumento metodológico de pesquisas na área de medicina, enfermagem e saúde pública baseadas na evidência. O presente estudo apresenta o percurso metodológico e os resultados obtidos na realização de uma RS, tendo como tema o efeito neurotóxico da exposição ocupacioanl ao mércurio, chumbo e manganês.
Asunto(s)
Plomo , Manganeso/fisiología , Mercurio , ToxicologíaRESUMEN
Se realizaron experimentos en trabéculas auriculares de rana catesbeiana, con la técnica de imposición de voltaje de doble puente de sacarosa, con el objetivo de determinar los efectos del cloruro de manganeso (MnCl2,3 mM) sobre el potencial de acción y las corrientes iónicas de estas preparaciones. Los resultados fueron los siguientes. El MnCl2 provocó: 1)Un acortamiento significativo en la duración del potencial de acción, eliminando la fase de meseta. 2) Evitó la prolongación del potencial de acción inducida por pulsos catódicosdurante la meseta. 3) Redujo la corriente de Na pico en 27 por ciento. 4) Provocó una inhibición en la corriente lenta hacia adentro (Isi), de un 97-100 por ciento. 5) Redujo Ik1 en un 15-20 por ciento, en el rango de -30 a + 40 mV. El MnCl2 no afectó el componente de rectificación retardada Ix1. Los presentes resultados indican que el MnCl2 no es selectivo en su acción sobre la permiabilidad de la membrana y permite concluir que la repolarización, en estas preparaciones, está gobernada por la inactivación de Isi (AU)