Cytoplasmic streaming in Chara corallina studied by laser light scattering

Area of Science:

• Cell Biology
• Biophysics
• Plant Physiology

Background:

• Cytoplasmic streaming is vital for intracellular transport in plant cells.
• Previous methods for measuring streaming velocity are often time-consuming or lack quantitative precision.

Purpose of the Study:

• To develop and validate a novel laser-Doppler velocimetry apparatus for quantifying cytoplasmic streaming in Chara corallina.
• To assess the in vivo rheological properties of algal cytoplasm.

Main Methods:

• Utilized a laser-Doppler velocimeter to analyze laser light scattered by motile cytoplasm.
• Measured the power-frequency spectrum of photomultiplier current from scattered laser light.
• Correlated velocimeter measurements with traditional light microscopy techniques.

Main Results:

• Observed a distinct Doppler peak in the spectrum, indicative of cytoplasmic streaming.
• Demonstrated that the Doppler peak disappears upon cessation of streaming via electrical stimulation.
• Achieved streaming velocity measurements (46-7 µm s⁻¹) comparable to light microscopy (44-3 µm s⁻¹).

Conclusions:

• The laser-Doppler velocimeter offers a rapid and quantitative method for assessing cytoplasmic streaming.
• This technique provides valuable data on the in vivo rheological properties of cytoplasm.
• The study indicates a narrow distribution of streaming velocities within Chara corallina cells.