Making it big : how characean algae use cytoplasmic streaming to enhance transport in giant cells

Meent, J.W. van de

Organisms show a remarkable variation in sizes, yet cell sizes are surprisingly similar across species, typically ranging from 10 _m to 100 _m. A striking exception are the giant cells of the algal weed Chara, which can exceed 10 cm in length and 1 mm in diameter. A circulation known as cytoplasmic streaming takes place inside these cells, which has been hypothesised to mitigate the slowness of diffusion on these scales. Our work has sought to quantify how this circulation allows the organism to circumvent the diffusional bottleneck that appears to limits cell size in most organisms. We examine the circulation pattern in the cylindrical internodal cells that make up the shoot of this organism. Along the surface of these cells, two twisting bands carry the cellular fluid up and down, forming a pattern much like the red and white ribbon on a barber pole. Hydrodynamic analysis reveals that this twisting of the bands, which is most prominent during growth, may serve to enhance mixing...Show moreOrganisms show a remarkable variation in sizes, yet cell sizes are surprisingly similar across species, typically ranging from 10 _m to 100 _m. A striking exception are the giant cells of the algal weed Chara, which can exceed 10 cm in length and 1 mm in diameter. A circulation known as cytoplasmic streaming takes place inside these cells, which has been hypothesised to mitigate the slowness of diffusion on these scales. Our work has sought to quantify how this circulation allows the organism to circumvent the diffusional bottleneck that appears to limits cell size in most organisms. We examine the circulation pattern in the cylindrical internodal cells that make up the shoot of this organism. Along the surface of these cells, two twisting bands carry the cellular fluid up and down, forming a pattern much like the red and white ribbon on a barber pole. Hydrodynamic analysis reveals that this twisting of the bands, which is most prominent during growth, may serve to enhance mixing in the cell, thereby aiding diffusional transport. Flow measurements by means of injected tracers, as well as an MRI technique known as Magnetic Resonance Velocimetry, are consistent with our hydrodymic description of the flow field.Show less

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Making it big : how characean algae use cytoplasmic streaming to enhance transport in giant cells

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