Electron Microscopy and X-ray Microanalysis of Antimonate Precipitates in Healthy and Virus Infected Leaves of Tobacco

Abstract

SUMMARYIn this research we observed the distribution of potassium pyroantimonate (KPA) precipitable inorganic cations in the cells of Nicotiana glutinosa L. leaves either healthy or mechanically infected with tobacco mosaic virus (TMV).We applied different techniques of preparation of the leaf samples for transmission and scanning electron microscopy. In addition, we analyzed the nature of antimonate precipitates by three different approaches. First, thin sections, checked for containing deposits, were floated on a solution of EDTA.The precipitates disappeared from the sections after 15 min: of treatment. Second: X-Ray Microanalysis was performed on thick (1μ), unstained sections of material fixed with KPA and embedded in Epon-Araldite. Third: X-Ray Microanalysis was made also on the leaf material, fixed with KPA, critical point dried and observed with a scanning electron microscope Jeol JSM/U3, equipped with an Energy Spectrometer Dispersive system (Laben Montedel). We applied these techniques to study the ion contents in the cross section of the leaf vein in both healthy and necrotic tissue. We found a smaller amount of ions in the lesions than in healthy tissues. We observed that the potassium pyroantimonate deposits, containing calcium, were localized on the xylem walls and on the substance(s) occluding the lumen of the tracheids which are at the boundary of the lesion.