title: Synergids and filiform apparatus in the sexual and apomictic dandelions from section Palustria (Taraxacum, Asteraceae).
abstract: An evolutionary trend to reduce "unnecessary costs" associated with the sexual reproduction of their amphimictic ancestors, which may result in greater reproductive success, has been observed among the obligatory apomicts. However, in the case of the female gametophyte, knowledge about this trend in apomicts is not sufficient because most of the ultrastructural studies of the female gametophyte have dealt with amphimictic angiosperms. In this paper, we tested the hypothesis that, in contrast to amphimictic plants, synergids in apomictic embryo sacs do not form a filiform apparatus. We compared the synergid structure in two dandelions from sect. Palustria: the amphimictic diploid Taraxacum tenuifolium and the apomictic tetraploid, male-sterile Taraxacum brandenburgicum. Synergids in both species possessed a filiform apparatus. In T. brandenburgicum, both synergids persisted for a long time without any degeneration, in spite of the presence of an embryo and endosperm. We propose that the persistent synergids in apomicts may play a role in the transport of nutrients to the embryo.
authors: Department of Plant Cytology and Embryology, Jagiellonian University, 9 Gronostajowa St., 30-387, Cracow, Poland, bartosz.plachno@uj.edu.pl.
authors: Bartosz J
authors: BJ
authors: Płachno
authors: Krystyna
authors: K
authors: Musiał
authors: Piotr
authors: P
authors: Swiątek
authors: Monika
authors: M
authors: Tuleja
authors: Jolanta
authors: J
authors: Marciniuk
authors: Aleksandra
authors: A
authors: Grabowska-Joachimiak
mesh_terms: D060832:Apomixis; D055993:Germ Cells, Plant / Q000648:ultrastructure*; D031205:Taraxacum / Q000648:ultrastructure*
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