Ovule and megagametophyte development in selected species of Apeibeae and Grewieae (Malvaceae–Grewioideae) from South America and its systematic implications

Abstract

Ovule and female gametophyte development in C. argutus, L. divaricata and T. semitriloba was analyzed. The ovules of all species are anatropous, bitegmic and crassinucellate mixed type. The micropyle of the studied species is formed by the outer integument (exostome). The ovule of L. divaricata differs from those of the other two species because the chalazal tissue expands forming a cap, giving rise to a wing in the seed. All species present one hypostase. The megaspore mother cell gives rise to a linear megaspore triad in C. argutus and L. divaricata, whereas in T. semitriloba, triads and diads can be observed in the same ovule. The chalazal megaspore develops a seven-celled and eight-nucleate female gametophyte corresponding to the Polygonum type. The synergids of L. divaricata have hooks and a conspicuous filiform apparatus. The antipodal cells in C. argutus are persistent, whereas in the other species, they are small and ephemeral. This is the first embryological report of the Grewioideae subfamily, which contributes to the characterization of the studied genera. Then compare to the data known for the family are inferred embryological characters for the group.