A Method of Direct Visualization of Plant Cell Organelles for Scanning Electron Microscopy

Identification of plant and animal cell organelles by scanning electron microscopy (SEM) has been demonstrated by several workers using a variety of methods. In one method Tanaka and lino exposed contents of fixed animal cells by cracking chilled tissues infiltrated with epoxy resin. Cracked tissues were dried and coated to reveal a number of cell organelles by small surface irregularities in an otherwise smooth break. We have achieved a more nearly in toto visualization of cell organelles by SEM using uncoated specimens fractured in chilled resin. This was done by rendering fixed tissues electrically conductive by the ligand-mediated osmium binding technique of Kelley, et al, prior to cracking. Unlike previous methods based on surface topography or sections, this procedure takes advantage of intrinsic secondary emissions from various organelles (Fig. 1) as a result of heavy osmium binding.