INVESTIGADORES
FERRUCCI Maria silvia
artículos
Título:
Ultrastructural study of the female gametophyte in Cabombaceae and Nymphaeaceae and its evolutionary implications
Autor/es:
ZINI, L. M.; GALATI, B.G.; FERRUCCI M.S.; ZARLAVSKY, G.
Revista:
FLORA
Editorial:
ELSEVIER GMBH
Referencias:
Año: 2016 vol. 220 p. 25 - 36
ISSN:
0367-2530
Resumen:
Ultrastructural studies on the female gametophyte arerestricted to species at relatively derived positions in the angiospermphylogenetic tree. Therefore, this topic remains mostly unknown for the early divergentlineages, in which a four-celled megagametophyte is common. Here,ultrastructure of the megagametophyte and micropylar nucellar epidermis wasinvestigated in Cabomba caroliniana A. Gray (Cabombaceae), Nymphaea gardnerianaPlanch. and Victoria cruziana Orb. (Nymphaeaceae). The micropylar nucellarepidermis of the studied species differentiates into an epistase. These cellshave metabolically active cytoplasm and thickened inner tangential walls.Epistase ultrastructure is compatible with a transfer cell specialization. Thistissue may play an adaptive role in the secretion of chemotropic substances todirect the pollen tube growth toward the female gametophyte. The cytologicalcharacteristics of the female germ unit in members of Cabombaceae andNymphaeaceae are generally similar to other angiosperms that develop a typicalseven-celled, eight-nucleate female gametophyte; however, they differ in somespecific points. In V. cruziana and N. gardneriana, the micropylar end of thesynergids develops a rudimentary filiform apparatus with slight inwardprojections. By contrast, the synergids lack a filiform apparatus in C.caroliniana. Unlike most studied angiosperms, the filiform apparatus in theclade Cabombaceae-Nymphaeaceae is underdeveloped or absent, therefore characterstate transformations have occurred within basal angiosperms. The potentialevolutionary shifts of this reproductive feature are highlighted.