Seed morphology and post-seminal development in Leiothrix Ruhland (Eriocaulaceae, Poales)
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The genus Leiothrix (Eriocaulaceae) is restricted to South America, where most species occur in the Espinhaço mountain chain in Brazil. Seed ornamentation has a distinctive origin in the family and in most species of Leiothrix the seed coat has a striated pattern. The objective of this study was to evaluate the morphological aspects of seeds of Leiothrix as well as the post-seminal development. Leiothrix seeds are elliptical or oval, the seed coat has a primary sculpture of isodiametric or hexagonal cells with concave periclinal walls and straight or sinuose anticlinal walls. Most species also have a secondary sculpture, which forms the striate ornamentation and this may be continuous or discontinuous with isolated, connected or cruciform annular striae. A comparative table of seed characters shows that most of them corroborate the current circumscription of the subgenera of Leiothrix. The seed coat striae expand with wetting and may help in seed imbibition during germination. Leiothrix seeds show a high germination rate and the post-seminal development pattern is similar to that described for other species of Eriocaulaceae.