Bidirectional flow of endoplasm inPhysarum plasmodium under centrifugal acceleration

Summary The behavior of cytoplasmic streaming in plasmodial strand ofPhysarum polycephalum was studied under centrifugal acceleration using a centrifuge microscope of the stroboscopic type. Cytoplasmic streaming in the plasmodium was greatly affected by changes in the acceleration. The endoplasmic flow in the centrifugal direction was accelerated, while that in the centripetal was retarded, by centrifugal acceleration. The centrifugal acceleration required to stop the endoplasmic flow in the centripetal direction did not cause total cessation of streaming but always induced a bidirectional flow of endoplasm in one and the same strand. Each profile of velocity distribution of the bidirectional flow was both parabola with flattened apex. One possible cause of the bidirectional flow is discussed.Dedicated to Emeritus Professor Noburo Kamiya on the occasion of his 80th birthday