The effect of ultracentrifuging on the cells of the root tip of the bean ( Phaseolus Vulgaris)

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Abstract
Root-tips were centrifuged in the Beams ultra-centrifuge at approximately 400,000 times gravity for 20 min. A marked stratification of the various materials present in the cells takes place in the order of their relative specific gravity. In cells where starch grains and vacuoles are not well developed the osmiophilic platelets are displaced to the centripetal pole while the mitochondria and plastids collect at the centrifugal pole. Thus a very important difference in relative specific gravity seems to exist between them. The order of distribution in such centrifuged cells seems to be as follows, starting at the centrifugal pole: (1) a layer of starch grains and plastids (when present in the cell); (2) a layer of mitochondria; (3) a layer of cytoplasm (often quite free of various cytoplasmic components) ; (4) a layer of osmiophilic platelets (Golgi bodies of Bowen) ; (5) a layer composed of or formed by the fusion of vacuoles; and (6) a layer of lipoid material. The nucleus is frequently stretched in the direction of the centrifuged force with the nucleolus constituting its heaviest component. In extreme cases the nucleolus is thrown completely out of the nucleus centrifugally.