Contribution of ovule anatomy to the taxonomic context of Parodia Spegazzini (Cactaceae)

Abstract The taxonomic history of Parodia Speg. is marked by many incongruences regarding its circumscription. The main question remains regarding the union of five genera into Notocactus s.l. and, later, the union of Notocactus s.l. with Parodia s.s., leading to Parodia s.l. Given that the ovules are conserved structures and that their anatomical structure remains unexplored within the genus, we sought to identify whether the anatomical traits of these structures show potential taxonomic applicability and whether they provide information that allows the genus to be circumscribed. Samples of flower buds of 15 species and two taxa in synonymy were processed and stained using plant anatomy methods for light microscopy. The ovules of Parodia are campylotropous, bitegmic, and crassinucellate, with the micropyle delimited by the inner integument; in Parodia s.s. we observed the nucellus and embryo sac projection and changes to the micropyle type, characteristics that reflect the circumscriptions that distinguish this genus from others in the synonymy of Parodia s.l. The results may also be useful with regard to infrageneric issues, allowing the distinction of some morphologically similar taxa, adding to the discussion of their infrageneric positions. Thus, we highlight the importance of ovule anatomical traits within the taxonomic context of Parodia.