Rhythmicity

Abstract

In protoplasmic streaming there are cases when no rhythmicity whatsoever is observed in the movement as in the typical rotation seen in Characeae, while in other cases the visible movement manifests conspicuous rhythmicity as is the case in myxomycete plasmodium. As to circulation, its movement has a rhythmical nature in that the streaming direction reverses itself from time to time. Küster (1956) claims that one of the most important points distinguishing rotation from circulation is that the former is aperiodic while the latter is periodic. Without doubt the most remarkable and regular rhythm manifested by the protoplasmic streaming is found in myxomycete plasmodia. There is a classical work of Voxjk (1910) on the rhythmicity of the streaming in the plasmodium of Didymium nigripes. He measured successively the duration of forward and backward flow and came to the conclusion that the total duration of progressive and regressive streamings, or what is called “rhythm duration” by Youk, is constant.