Apogamy

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Apogamy is a botanical technical term from the area of ​​"asexual reproduction", which was defined differently and is still not used uniformly today.

Anton de Bary (1878) took the term very broadly and applied it to all cases in which "a species (or variety) has lost sexual conception and is replaced by another reproductive process". In 1906, Hans Winkler introduced the term apomixis (in the broader sense including vegetative reproduction) and redefined apogamy as the "apomictic generation of a sporophyte from vegetative cells of the gametophyte."

In 1904 Eduard Strasburger differentiated (after Juel's preliminary work) for the first time between parthenogenesis and apogamy, the first term denoting a development of the egg without a reduction division , the apogamy one with a reduction division. Carl Correns accepted this separation at the time, but noted that it would have been better to designate the superordinate phenomenon or the phenomenon with reduction division as parthenogenesis. As you can see, Strasbuger's definition has little to do with Winkler's, since it concerns reproductive processes without meiosis.

The current use of the term is based on Winkler, but is not uniform. This is apparently due to the fact that Winkler's formulation “vegetative cells of the gametophyte” is interpreted differently. Apparently, some authors doubt that in spermatophytes , which reproduce asexually via agamospermia , generative and vegetative cells of the gametophyte can be clearly distinguished. Since meiosis in the embryo sac mother cell does not occur in them , a multinucleated embryo sac is created , the nuclei of which consistently have an unreduced set of chromosomes. Loos (2008) therefore only allows the term apogamy to apply to those plants that have a multicellular gametophyte in which the clearly distinguishable generative cells have become inoperable or have been aborted, and embryos arise from cells of the vegetative gametophyte tissue. Algae and fern plants come into question for this, theoretically also gymnosperms , in which apparently no cases of apogamy are known. According to other authors, however, a distinction can be made as to whether the embryo sac nucleus that reaches embryonic development without fertilization corresponds to the egg cell or a vegetative cell (cf. agamospermia). If the embryo emerges from the egg cell equivalent, it is parthenogenesis, otherwise apogamy.

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  • Götz Heinrich Loos: Plant-geographical contributions to the chorological, taxonomic and nature conservation assessment of the clan diversity of agamopserm (apomictic) flowering plant complexes: The example of Rubus subgen. Rubus (Rosaceae). - Dissertation Univ. Bochum, 99 p. (PDF; 2.35 MB)
  • Eduard Strasburger : The apogamy of the Eualchimillen etc. In: Jahrb. F. scientific botany. 41. 1904, p. 81 ff.
  • Carl Correns: Gregor Mendel's letters to Carl Nägeli 1866–1873.