Summary
The structure of sperm cells and their association with the vegetative nucleus in pollen tubes ofNicotiana tabacum grown in styles were observed with the electron microscope, demonstrating the existence of a male germ unit. The two sperm cells are arranged in tandem and are closely associated with the vegetative nucleus, which always takes the lead. The leading sperm cell (SC 1) has a long and narrow cytoplasmic projection which lies within the enclaves of the much lobed vegetative nucleus, thus forming a physical association. The trailing sperm cell (SC 2) and the SC 1 are not only joined by a common transverse cell wall but also are surrounded by a periplasm bounded by the plasma membrane of the sperm cells and that of the vegetative cell, thus forming a structural connection. The sperm cells are elongated, with cytoplasmic projections at the anterior end of the SC 1 and at both ends of the SC 2. The cytoplasm of both sperm cells includes mitochondria, endoplasmic reticulum, dictyosomes, ribosomes, small vacuoles and axially oriented microtubules. No plastids were observed.
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Abbreviations
- DAPI:
-
4,6-diamino-2-phenylindole
- MGU:
-
male germ unit
- MT:
-
microtubule
- SC 1:
-
the leading sperm cell physically associated with the vegetative nucleus
- SC 2:
-
the trailing sperm cell
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Yu, HS., Hu, SY. & Zhu, C. Ultrastructure of sperm cells and the male germ unit in pollen tubes ofNicotiana tabacum . Protoplasma 152, 29–36 (1989). https://doi.org/10.1007/BF01354237
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DOI: https://doi.org/10.1007/BF01354237