Diffusive motions in living cytoplasm probed by laser Doppler microscopy

Abstract

SUMMARYWe have examined cytoplasmic motions in growing pollen tube tips using laser Doppler microscopy, a non‐invasive and non‐destructive technique. The observed correlation functions were consistent with the existence of diffusive motions in the tip cytoplasm. Further analysis of the data revealed the existence of at least two major and a third, minor, diffusing species in the cytoplasm. Information from quantitative electron microscopy and from published literature values of cytoplasmic viscosity was used to tentatively identify the organelles contributing to the observed diffusive motions. It is concluded that motions of mitochondria and secretory vesicles dominate the observed correlation functions with a minor component detected from either ribosomes or the microfilament network. Sources of variation in the observed data are discussed, as are the physical limitations that prevent a more positive analysis of the present data.