In aquatic plants such as the Characean algae, the force generation that
drives cyclosis is localized within the cytoplasm, yet produces fluid flows
throughout the vacuole. For this to occur the tonoplast must transmit
hydrodynamic shear efficiently. Here, using magnetic resonance velocimetry, we
present the first whole-cell measurements of the cross-sectional longitudinal
velocity field in Chara corallina and show that it is in quantitative agreement
with a recent theoretical analysis of rotational cytoplasmic streaming driven
by bidirectional helical forcing in the cytoplasm, with direct shear
transmission by the tonoplast.Comment: 5 pages, 3 figure