Summary
An analysis of the entrance and discharge of the pollen tube into the embryo sac of Gossypium hirsutum was made with the light and electron microscopes. The following sequence of events is seen in cotton:
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1.
One of the two synergids begins to degenerate following pollination but before the pollen tube reaches the embryo sac. This degeneration is marked by the swelling and darkening of the organelle membranes, the collapse of the vacuoles, and the disappearance of the plasma membrane. Striking chemical changes accompany the structural degeneration.
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2.
The pollen tube grows into the degenerating synergid through the filiform apparatus. The tube ceases growth while the tip is still in the synergid. A pore develops on the chalazal side of the tube in a subterminal position.
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3.
The pollen tube cytoplasm and the sperm are discharged into the degenerating synergid through the pore in the tube. Following discharge a plug forms at the pore. None of the discharge leaves the synergid except the sperm nuclei which enter the egg or central cell directly from the synergid. The X-bodies present in the synergid are the remains of the sperm cytoplasm.
The data stress the importance of the degenerating synergid in pollen tube discharge and the entrance of the sperm nuclei into the egg and central cell. A hypothesis is presented to explain the passage of the sperm nuclei into the egg and central cell. The data show clearly that the pollen tube does not destroy the synergid it enters, and that the degenerating synergid following pollen-tube discharge is remarkably stable.
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References
Balls, W. L.: The sexuality of cotton. In: Yearbook of the Khedivial Agr. Soc., p. 199–222. Cairo 1905.
Colwin, A. L., and L. H. Colwin: Role of the gamete membrane in fertilization. In: 22nd Symp. of the Soc. for the study of development and growth (M. Locke, ed.), p. 233–279. New York: Academic Press Inc., 1964.
Gore, U. R.: Development of the female gametophyte and embryo in cotton. Amer. J. Bot. 19, 795–807 (1932).
Jensen, W. A.: Botanical histochemistry. San Francisco: W. H. Freeman & Co. 1962.
—: The ultrastrucuture and histochemistry of the synergids of cotton. Amer. J. Bot. 52, 238–256 (1965).
Jensen, W. A., and D. B. Fisher: Cotton embryogenesis: double fertilization. Phytomorphology (in press) (1968).
Maheshwari, P.: An introduction to the embryology of angiosperms. New York: McGraw-Hill Book Co. 1950.
Nawaschin, S. G.: Über die Befruchtungsvorgänge des Spermakerns bei einigen Angiospermen. Ber. dtsch. bot. Ges. 18, 224–230 (1900).
Pluijm, J. E. van der: An electron microscopic investigation of the filiform apparatus in the embryo sac of Torenia fournieri. In: Pollen physiology and fertilization (H. F. Linskens, ed.), p. 8–16. Amsterdam: North-Holland Publ. Co 1964.
Tyler, A.: The biology and chemistry of fertilization. Amer. Naturalist 99, 309–334 (1965).
Wylie, R. B.: Some aspects of fertilization in Vallisneria. Amer. J. Bot. 28, 169–174 (1941).
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Jensen, W.A., Fisher, D.B. Cotton embryogenesis: The entrance and discharge of the pollen tube in the embryo sac. Planta 78, 158–183 (1967). https://doi.org/10.1007/BF00406648
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DOI: https://doi.org/10.1007/BF00406648