On the variability of spherosome-like bodies in Phaseolus vulgaris

Abstract

Root and shoot apices and primary leaves of 3- to 4-day-old seedlings of Phaseolus vulgaris L. were examined in the electron microscope after fixation with (a) glutaraldehyde followed by osmium tetroxide, (b) glutaraldehyde followed by potassium permanganate, (c) osmium tetroxide alone, and (d) potassium permanganate alone. The distribution, shape, and substructure of the spherosome-like bodies in the cytoplasm varied markedly depending upon the tissue, its age, and the fixation used. Shapes varied from stellate through polygonal to spherical. The electron density of the interior of the organelles varied from uniformly dark after osmium tetroxide fixation to almost none after permanganate fixation. In addition to differences caused by fixatives, marked variation of the electron density of the same organelles with identical fixation was observed. Structural, and possibly physiological, heterogeneity seems to be characteristic of spherosomes but in spite of their variability, they may be recognized in the electron microscope as a group of similar structures distinct from other organelles.