Effect of Ultra-Centrifuging on the Cells of the Root-Tip of the Bean

Abstract

ROOT-TIPS of the bean were centrifuged in the Beams ultra-centrifuge at approximately 400,000 times gravity for twenty minutes. The effect is shown diagrammatically in Fig. 1. Fig. 1(a) is a control cell showing the normal distribution of the cytoplasmic components and inclusions. Fig. 1(b) represents an ultra-centrifuged cell showing the redistribution of the cytoplasmic components and inclusions into layers in the order of their relative and decreasing specific gravity, as follows: (1) a layer of starch grains and plastids (when present in the cell); (2) a layer of mitochondria (plastidome and pseudo-chondriome); (3) a layer of cytoplasm (which is 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. Thus, it is evident from this study that the osmiophilic platelets are discrete structures in plant cytoplasm, and differ greatly in specific gravity from the plastids and mitochondria.