Seed morphology in the genus Matthiola R. Br. (Brassicaceae): Identification of species and systematic implications

Seed coat morphology of 34 species of Matthiola R.Br. has been studied using light and scanning electron microscopy to assess their investigative value for systematic studies. Macro- and micromorphological characters, including seed shape, color, size, wing, and radicle position relative to cotyledons, epidermal cell shape, anticlinal boundaries, and periclinal cell wall are presented. Seed shape, color, and radicle position relative to cotyledons have limited taxonomic significance, as their variation is unhelpful. There against, seed size, wing, and seed coat ornamentation present informative characteristics that can be used professionally in distinguishing the studied taxa. Six different types of seed anticlinal cell wall boundaries are recognized and five different outer periclinal cell wall shapes are described. The sculpture of the secondary cell wall varies from striate, micropapillate to microreticulate, and smooth to fine folds. The taxonomic and phylogenetic implications of seed coat micromorphology were compared with those of the existing gross morphological and molecular data. Seed character analysis offered useful data for evaluating the taxonomy of Matthiola both on subgeneric and sectional levels. Seed micromorphological characters provide evidence that M. odoratissima and M. ovatifolia should be preserved as separate species. In addition, M. ghorana is not conspecific with M. graminea. Furthermore, M. tricuspidata was unique in the seed characters. A key to the identification of the examined taxa based on seed characters is provided.