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ORCHID EMBRYOLOGY: MEGAGAMETOPHYTE OF EPIDENDRUM SCUTELLA FOLLOWING FERTILIZATION
Author(s) -
Cocucci Alfredo,
Jensen William A.
Publication year - 1969
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1969.tb07579.x
Subject(s) - biology , zygote , pollen tube , egg cell , endosperm , botany , sperm , human fertilization , double fertilization , nucleus , microbiology and biotechnology , polysome , embryo , ultrastructure , cytoplasm , fertilisation , anatomy , pollen , genetics , embryogenesis , pollination , ribosome , rna , reproductive technology , gene
The megagametophyte of Epidendrum scutella , an orchid, was examined with the electron microscope after the entrance and discharge of the pollen tube. The pollen tube enters the embryo sac by growing through the filiform apparatus of a synergid and discharges through a terminal pore into the degenerating cytoplasm of the synergid. The synergid nucleus appears pushed to one side by the discharge of the pollen tube. What is believed to be the remains of the vegetative nucleus has been found in the degenerate synergid, but no trace of the sperm cytoplasm has been seen. The zygote is approximately the same size as the egg. The ribosomes become grouped into polysomes. Both the egg and the zygote apparently completely lack dictyosomes. The polar nuclei partially fuse before fertilization, but fusion of the sperm nucleus with the polar nuclei does not occur and no endosperm is produced. Polysome formation occurs in the central cell and large amounts of tubular, smooth ER are seen. The antipodals remain following fertilization, undergoing ultrastructural changes similar to the central cell.