Europium Uptake and Partitioning in Oat (Avena sativa) Roots as Studied by Laser-Induced Fluorescence Spectroscopy and Confocal Microscopy Profiling Technique

摘要

The uptake of Eu{sup}(3+) by elongating oat roots was studied by fluorescence spectroscopy, fluorescence lifetime measurement, and a laser excitation time-resolved confocal fluorescence profiling technique. The results of this work indicated that initial uptake of Eu{sup}(3+) was highest within the undifferentiated cells of the root tip just behind the root cap, a region of maximal cell growth and differentiation and with incomplete formation of the Casparian strip around the central vascular cylinder. Distribution of assimilated Eu{sup}(3+) within the root's differentiation and elongation zone was nonuniform. Higher concentrations of Eu{sup}(3+) were observed within the vascular cylinder, specifically in the phloem and developing xylem parenchyma. Elevated levels of the metal were also observed in the root hairs of the mature root zone. Fluorescence spectroscopic characteristics of the assimilated Eu{sup}(3+) suggested that the Eu{sup}(3+) exists as inner-sphere mononuclear complexes inside the root. This work also demonstrated the effectiveness of a time-resolved Eu{sup}(3+) fluorescence spectroscopy and confocal fluorescence profiling techniques for the in vivo, realtime study of metal [Eu{sup}(3+)] accumulation by a functioning intact plant root. This approach can prove valuable for basic and applied studies in plant nutrition and environmental uptake of actinide radionuclides.