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Key message : The Cyperaceae fruit consistency depends on the mesocarp. Seed structure is diverse and related to the evolutionary history of their species. A new storage tissue is described for Cyperaceae. Anatomy and histochemistry of Cyperaceae fruits (including seeds) are poorly known due to their hard, isolating tissues that prevent anatomical techniques. We performed the first, most comprehensive structural diversity characterisation of fruit and seed in Cyperaceae, accompanied by an unprecedented histochemical characterisation of seeds for this family. We analysed fruits of 29 species, included in 19 genera and 12 tribes within the subfamilies Cyperoideae and Mapanioideae, using light microscopy. Cyperaceae fruits have a pericarp with a one-cell-layered exocarp and endocarp, and a multi-cell-layered mesocarp. The mesocarp of the Mapanioideae has a spongy-fleshy outer region and a hard inner region. The mesocarp of the Cyperoideae has only a hard region. The pericarp is free from the seed coat. Cyperaceae seeds have a three-layered seed coat, an embryo with haustorial function of its scutellum, and two storage tissues: the endosperm and a putative perisperm. Nine seed morphotypes and four seed subtypes were observed among the studied species. Our results suggested that the fruit consistency is determined by the mesocarp. Both the terms "nut" and "achene" should be accepted to refer to the dry fruit of the Cyperaceae until a widely accepted fruit classification for angiosperms is proposed. The Cyperaceae seed structural diversity is high and related to the evolutionary history of the species. The "perisperm" is a new tissue proposed for sedge seeds, and is here characterized for the first time. The seed coat has a different structure than the one described so far for the family. [ABSTRACT FROM AUTHOR]

Inflorescences in Cyperaceae are a source of characters with significant systematic value; however, the structure and primary homologies pose a challenge to their interpretation. The relationships among members of Abildgaardieae are not clear due to the absence of a phylogeny with strong support, comprising a representative number of species. Establishing correct primary homologies of inflorescences within Abildgaardieae might help to clarify the relationships among its members, as well as to find synapomorphies for the most important clades. Variations in the mature inflorescences within Abildgaardieae have been related to their “shape” and “structure”, and preliminary phylogenetic studies in species of Bulbostylis have shown that inflorescence structure traits are phylogenetically informative, but this is not true for the mere shape. While similar structures in the adult inflorescences of the members of different clades within Abildgaardieae might be considered homologous, it must be ascertained whether such similar structures share the same developmental process or have different developmental patterns. By studying the development of inflorescences in selected species of Abildgaardieae using SEM, we were able to show that inflorescences with homologous structures share a similar developmental process and, therefore, the adult structure of inflorescences may be relied on for establishing correct primary morphological homologies in this plant group. Most structural variations of inflorescences in Abildgaardieae depend on the degree of development of processes shared by the studied species. While phyllotaxis in the main axis of Cyperus may be modified during inflorescence development after primordial inception, variations in the phyllotactic patterns of leaves on vegetative shoots (=nomophylls) and of leaves on fertile shoots (=bracts or hypsophylls) within Abildgaardieae, might establish deeper differences in inflorescence structure, since they depend on changes in the shape of the apical meristem. [ABSTRACT FROM AUTHOR]