ELECTRON-MICROSCOPE COMPARISON OF PLASMA-MEMBRANE VESICLES FROM MERISTEMATIC AND MATURE SOYBEAN ROOT-TISSUE

Plasma membrane vesicles were isolated from homogenates of meristematic and mature soybean [Glycine max cv. Wells] root tissue by differential sucrose gradient centrifugation. Vesicles were positively identified by the phosphotungstic acid-chromic acid procedure (PACP). The 2 preparations were comparable in size class distribution, mitochondrial contamination and percent plasma membrane vesicles present. Purity levels were estimated to be greater than 75%. The specificity of PACP was observed for a variety of cell types from both regions. Some variability in PACP staining was offset by careful modulation of the stain protocol and was independent of developmental stage in subcellular fractions. Patchy or discontinuous staining, observed in both intact tissue and in subcellular fractions from both regions, was a function of stain time.