Fertilization of a colchicine-treated gamete of the fern Marsilea vestita.
In the fern, Marsilea vestita, the addition of colchicine to the culture medium during the final stages of archegogenesis gives rise to a new distribution of cellular organelles and lipid droplets within the egg cytoplasm. These changes affect primarily the usually free space through which the spermatozoid moves towards the female nucleus. Depending on the length of the treatment this fertilization cone may disappear. Completion of fertilization, i.e. karyogamy, is only observed in the presence of this cone. When it is missing, progress of the male nucleus, which is no longer directly channeled towards the female nucleus, is notably slowed down and karyogamy does not occur. Then, male chromatin decondensation takes place in the egg cytoplasm. This event enables us to describe the structure of the sperm nucleus: it is composed of two cylindrical parallel units which, subsequently, break up into short fragments which may be the "male chromosomes".
D002467:Cell Nucleus / Q000648:ultrastructure; D003078:Colchicine / Q000494:pharmacology*; D003593:Cytoplasm / Q000648:ultrastructure; D005260:Female; D005306:Fertilization / Q000187:drug effects*; D010063:Ovum / Q000187:drug effects / Q000648:ultrastructure; D010944:Plants / Q000187:drug effects*
D003078:Colchicine