Isolation of Vacuoles from Root Storage Tissue of Beta vulgaris L

Morphologically intact and osmotically active vacuoles were isolated from root storage tissue of the red beet Beta vulgaris L., and the factors influencing both yield and stability of the vacuoles were determined. Successful isolation depended upon slicing the tissue in an apparatus specifically designed to cut open plant cells without the use of high shear forces and to liberate cellular organelles into an undisturbed reservoir of osmoticum. The resulting brei was centrifuged at 2,000g for 10 min to yield a pellet which contained many vacuoles but which also contained tissue fragments, nuclei, mitochondria, and plastids. The vacuoles were further purified by accelerated flotation through a Metrizamide step gradient. Biochemical assays, light microscopy, and electron microscopy confirmed that there was only trace contamination of the final vacuole preparation by other organelles. Isolated vacuoles were intact and retained their in vivo coloration.