A study of protoplasmic streaming in Nitella by laser Doppler spectroscopy

Abstract

Laser light scattered from particles in the streaming protoplasm of a living cell is shifted in frequency by the Doppler effect. The spectrum of the scattered light can be measured and interpreted to infer details of the velocity distribution in the protoplasm. We have developed this approach to study the protoplasmic streaming in the fresh-water alga Nitella. Our results indicate a characteristic flow pattern to which diffusion makes a negligible contribution. No difference in the velocity of particles of different size is indicated. The streaming velocity linearly with temperature with a supraoptimal temperature of 34 degrees C, and the velocity distribution becomes narrower at high temperatures. The protoplasmic streaming can be inhibited by laser light, and this effect has been used to study the photoresponse of the algae. Using beam diameters of about 50 mum, we have shown that the inhibition is very local, becoming minimal at a displacement of about 200 mum in the upstream direction and 400 mum in the downstream direction. Prolonged exposure produces a bleached area free of chloroplasts, which is three orders of magnitude less sensitive to photoinhibition.

Hydrodynamic models of viscous coupling between motile myosin and endoplasm in characean algae.

“…Laser-light scattering is a more senskive technique for velocity analysis than is simple microscope observation, because light scattering can detect nonvisual events such as fluctuations in refractive index due to concentration fluctuations (15). Velocity histograms obtained NOTHNAGEL AND WEBB with either the Doppler (15,16,18,19) or the correlation (17,20) technique are in close agreement and show that most of the endoplasm moves with velocities failing in a narrow range around the most probable velocity. The most probable velocity corresponds very closely to the velocity of the bulk endoplasm as measured by light microscopy.…”

Batchelor Prize Lecture Fluid dynamics at the scale of the cell

“…Early measurements (Kamiya & Kuroda 1956;Mustacich & Ware 1976) of the cross-sectional flow using endogenous particles as tracers and a laser Doppler technique revealed an S-shaped longitudinal velocity profile along one particular diameter, interpolating between the upward and downward wall-driven flows. But these were not capable of revealing the entire flow profile and testing even the most basic aspects of the global flow, such as whether the idea of piecewise constant forcing was a sensible result from multitudes of stochastic molecular motors moving along an array of filaments.…”

Measurement of cytoplasmic streaming in single plant cells by magnetic resonance velocimetry

“…The first direct measurements of the wall-to-wall profile are those of Kamiya and Kuroda (1956), who studied rhizoid cells, 'leaf' cells sprouting from nodes, and internodal cells, and found a constant velocity within the cytoplasm and a curved shear profile within the vacuole. Mustacich and Ware (1976) improved on these measurements by using laser-Doppler scattering through a chloroplast-free window obtained by exposure to an argon laser prior to observation. Pickard (1972) obtained velocity measurements for a collection of native particles in an internodal cell of Chara braunii, showing consistency with the velocity deduced under the approximation of non-helical indifferent zones.…”