Ultrastructural study of the female gametophyte and the epistase in cabombaceae and nymphaeaceae

• Autores: Zini, Lucía Melisa; Galati, Beatriz Gloria; Ferrucci, María Silvia; Zarlavsky, Gabriela Elena; Rosenfeldt, Sonia
• Año de publicación: 2016
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Flora, 2016, vol. 220, p. 25-36.
• Materia: Cabomba caroliniana; Filiform apparatus; Nymphaea gardneriana; Transfer cell
• Institución: Universidad Nacional del Nordeste

Fil: Zini, Lucía Melisa. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina.
Fil: Zini, Lucía Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste.
Fil: Galati, Beatriz Gloria. Universidad de Buenos Aires. Facultad de Agronomía; Argentina.
Fil: Ferrucci, María Silvia. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina.
Fil: Ferrucci, María Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste.
Fil: Zarlavsky, Gabriela. Universidad de Buenos Aires. Facultad de Agronomia; Argentina.
Fil: Rosenfeldt, Sonia. Universidad de Buenos Aires; Argentina.
Ultrastructural studies on the female gametophyte are restricted to species at relatively derived positions in the angiosperm phylogenetic tree. Therefore, this topic remains mostly unknown for the early divergent lineages, in which a four-celled megagametophyte is common. Here, ultrastructure of the megagametophyte and micropylar nucellar epidermis was investigated in Cabomba caroliniana A. Gray (Cabombaceae), Nymphaea gardneriana Planch. and Victoria cruziana Orb. (Nymphaeaceae). The micropy lar nucellar epidermis ofthe studied species differentiates into an epistase. These cells have metabolically active cytoplasm and thickened inner tangential walls. Epistase ultrastructure is compatible with a trans fer cell specialization. This tissue may play an adaptive role in the secretion of chemotropic substances to direct the pollen tube growth toward the female gametophyte. The cytological characteristics of the female germ unit in members of Cabombaceae and Nymphaeaceae are generally similar to other angiosperms that develop a typical seven-celled, eight-nucleate female gametophyte; however, they differ in some specific points. In V. cruziana and N. gardneriana, the micropylar end of the synergids develops a rudimentary filiform apparatus with slight inward projections. By contrast, the synergids lack a filiform apparatus in C. caroliniana. Unlike most studied angiosperms, the filiform apparatus in the clade Cabombaceae-Nymphaeaceae is underdeveloped or absent, therefore character state transfor mations have occurred within basal angiosperms. The potential evolutionary shifts of this reproductive feature are highlighted.