Microtubular Motors in the Pollen Tube of Nicotiana tabacum

The Angiosperm pollen tube Is specialized in delivering the sperm cells during the process of fertilization (Cresti and Tiezzi, 1990). Microtubules and actin filaments are the main components of the vegetative cell cytoskeleton, which study has been extensively carried out mainly by electron and fluorescence microscopy (reviewed by Tiezzi, 1991). Many types of motility characterize the cytoplasm of the pollen tube, including the movement of generative and sperm cells and the translocation of organelles and vesicles (Pierson et al., 1990). The dependence of this movement on the cytoskeletal elements is not well understood, even though some recent observations seem to support the actin filament system as an active component (Tang et al., 1989). On the other hand the role of microtubules in the cytoplasmic movement and consequently in the tube growth is not yet clear. Some recent remarks (Åström et al., 1991) have suggested possible correlations between the microtubule cytoskeleton and the movement of generative cell and vegetative nucleus