Summary
Pollen tubes grow by tip growth, with high levels of exocytosis at the apex. The commercial availability of FITC labelled α-linked dextrans provides a source of biologically inert tracers for endocytotic activity in pollen tubes. Growing tubes ofNicotiana andTradescantia were transferred to media containing 1% FD-4 for varying period of time before washing in control media and observation in a fluorescence microscope. Fluorescent material appeared to enter the pollen tubes only at the tip region, and to accumulate in vacuoles, starting with smaller vacuoles near the tip and spreading to the main vacuolated part of the tube. Mature tubes, with callose plugs, were only labelled up to the first complete plug from the tip, younger tubes without plugs were labelled into the pollen grain vacuole. The fluorescent material within the pollen tubes was shown to represent uptake of intact high molecular weight dextran by the following criteria: (i) free FITC and low molecular weight dextrans could not be detected in any of the media or pollen tubes using thin layer chromatography and (ii) pollen tube growth rates were unaffected by the fluorescent dextran, but were severely inhibited by low levels of free FITC. It was concluded that the dextrans entered the tubes by endocytosis, possibly in the tip region, and were then transferred to the vacuole system of the pollen tube.
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Abbreviations
- FITC:
-
fluorescein isothiocyanate
- FD:
-
fluorescent dextran
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O'Driscoll, D., Hann, C., Read, S.M. et al. Endocytotic uptake of fluorescent dextrans by pollen tubes grown in vitro. Protoplasma 175, 126–130 (1993). https://doi.org/10.1007/BF01385010
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DOI: https://doi.org/10.1007/BF01385010