CYTOLOGY OF FERTILIZATION AND PROEMBRYOGENY IN SOME GYMNOSPERMS

Cytological research on fertilization and pre-embryogeny in the Abietaceae showed that after fertilization a new cytoplasm, or neocytoplasm, arose in the oosphere, formed mainly from the former nucleoplasm of the zygote and the cytoplasm of the perinuclear zone of the oosphere. It is from this neocytoplasm that the cytoplasm of the proembryo and that of the embryo itself are progressively built up. An analysis of the evolution of the ultrastructure of the neocytoplasm enabled the origin of the mitochondria and plastids of the embryo to be determined, at least in the case of the species Larix decidua. The greater part of the mitochondria of the embryo arose from the perinuclear zone of the female gamete; a few were introduced by the pollen. The plastids of the embryo, on the other hand, derived entirely from the pollen; the highly deformed plastids of the oosphere did not penetrate into the neocytoplasm. © Taylor & Francis Group, LLC.