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Journal of Cell Science, Vol 89, 551-560, Copyright © 1988 by Company of Biologists

Submitted on November 18, 1987
Accepted on December 21, 1987

Insemination of the archegonium and fertilization in Taxus baccata L

ROGER I. PENNELL 1 and PETER R. BELL 2

1 Department of Botany and Microbiology, University College London Cower Street, London WCIE 6BT, UK; Present address and correspondence to: John Innes Institutue and AFRC Institute of Plant Science Research Colney Lane, Norwich NR4 7UH, UK
2 Department of Botany and Microbiology, University College London Cower Street, London WCIE 6BT, UK

A study of fertilization in Taxus baccata in the electron microscope has revealed novel features. Insemination of the archegonium is facilitated by local perforation of the wall of the young pollen tube. Digestion of the wall begins before the pollen tube pierces the megaspore membrane but is not completed until its tip makes contact with the neck cells of the archegonium. As soon as a pore is formed a single sperm nucleus and some cytoplasm of the male gametophyte enter the archegonium. Which of the paired sperm nuclei move from the pollen tube into the archegonium appears to be a matter of chance. Close apposition of sperm nucleus and egg nucleus is followed by the formation of numerous points of contact between the two. The membranes fuse at these points and pores are rapidly formed. The progressive enlargement of these pores ultimately eliminates any partitions and yields the zygotic nucleus. There is a possibility that, as in some other gymnosperms, the plastids and mitochondria of the zygote come in part from the male gametophyte, but whether from the remains of the spermatogenous cell cytoplasm or from the. pollen tube lumen is not clear.

Key words: fertilization, gymnosperm, sperm nucleus, Taxus baccata

Submitted on November 18, 1987
Accepted on December 21, 1987




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© The Company of Biologists Ltd 1988