Velocity Distribution of the Protoplasmic Streaming in Nitella Cells

Abstract

1)The intracellular velocity distribution of the rotational streaming was determined in cells of rhizoid, 'leaf' and internode of Nitella flexilis.
2) In the cells havig a central vacuole, the plasmasol (endoplasm) at different layers flows with a nearly equal rate giving rise to an only insignificant velocity gradient inside. Only in the very narrow interfacial region between sol and gel layers there is an enormous velocity gradient.
3) In the cell, the whole space of which is filled artificially with endoplasm, the streaming of endoplasm occurs with a velocity distribution which coincides with that we would expect the endoplasm to assume when it is moved passively between two semicylindrical walls which shift in the opposite directions.
4) On the basis of analysis of the intracellular velocity distribution with the aid of a model experiment it was concluded that the flow of endoplasm is passive; the mechanism which drives endoplasm actively resides in the interfacial region between plasmasol (endoplasm) and plasmagel (ectoplasm).