Structural basis of cytoplasmic streaming in Characean internodal cells. A hydrodynamic analysis

Summary Hydrodynamic equations were derived which relate the velocity profile of endoplasmic streaming with the motive force generated by active sliding of endoplasmic organelles in Characean internodal cells, under two implicit assumptions that (1) the sliding velocity of putative organelles is comparable to the streaming velocity of endoplasm, and (2) subcortical endoplasm is far less viscous than bulk endoplasm.The equations were extended so as to calculate the velocity profile in flattened or perfused internodal cells. Calculated profiles were basically consistent with reported patterns of streaming under these conditions.Utilizing published data, we deduce some hydrodynamic parameters of streaming, and predict the dimensions of putative organelles expected to drive entire cytoplasm. A revision for published values of the motive force of streaming is proposed.Hydrodynamic analyses made earlier on the spherical organelles are repeated. The results show that the organelles may generate streaming, depending on the configurationin vivo of fine filaments protruding from the body of the organelles.