The effects of ruthenium red,lanthanum, fluorescein isothiocyanate and trifluoperazine on vesicle transport,vesicle fusion and tip extension in pollen tubes

The effects of ruthenium red, lanthanum, fluorescein isothiocyanate and trifluoperazine, all antagonists of Ca²⁺ function in cells, have been studied in growing pollen tubes of Tradescantia virginiana. All four drugs inhibit pollen-tube growth but bring about different ultrastructural changes at the growing tips and within the cytoplasm. The results strongly support the hypothesis that Ca²⁺ plays a vital role in the mechanism of pollen-tube tip growth. The effect of ruthenium red provides evidence that sequestration of Ca²⁺ by mitochondria critically adjusts the concentration of these ions at tube tips. Fluorescein isothiocyanate appears to be a potent inhibitor of vesicle fusion at the plasma membrane, with vesicles accumulating in the tip at rates equivalent to those determined previously for their production. Both vesicle fusion and tip extension are regulated by Ca²⁺ but appear to be independently controlled processes.