Subcellular Motions in Nitella flexilis studied by Photon Correlation Spectroscopy

Photon correlation spectroscopy was used to study the motions of subcellular components of the giant internodal cells of the Characean alga Nitella flexilis both during endoplasmic streaming and during the electrically-induced, transitory arrest of streaming. With the direction of streaming oriented parallel to the scattering wave vector, the streaming of subcellular particles was detected as periodic oscillations in the intensity autocorrelation functions derived from scattered laser light. When streaming was oriented perpendicular to the scattering wave vector, monotonically decaying intensity autocorrelation functions were observed and during the cessation of streaming the decay rate measured at a delay time (τ) of 100 μs became faster, whereas at τ = 2 ms the decay rate became slower. Removal of the chloroplasts from the scattering region did not affect the decay rates recorded from cells in which streaming was oriented perpendicular to the scattering wave vector. The results are discussed in relation to mechanisms proposed for the generation of the motive force of endoplasmic streaming in Characean algae.