Trying to Understand the Complicated Taxonomy in Amaranthus (Amaranthaceae): Insights on Seeds Micromorphology.

Amaranthus is a genus taxonomically complex because of its high morphological variability, which led to nomenclatural disorders, misapplication of names, and misidentifications. Floristic and taxonomic studies on this genus are still incomplete, and many questions remain open. Seed micromorphology has been shown to play an important role in the taxonomy of plants. Regarding Amaranthaceae and Amaranthus, investigations are rare, and they refer to one or a few species. With the primary aim to test if seed features are helpful in the taxonomy of Amaranthus, we here present a detailed SEM study on seed micromorphology in 25 Amaranthus taxa using morphometric methods. Seeds were collected from field surveys and herbarium specimens; 14 seed coat features (7 qualitative and 7 quantitative) were measured on 111 samples (up to 5 seeds per sample). The results obtained revealed that seeds micromorphology provides interesting new taxonomic data concerning some taxa (species and below ranks). In fact, we were able to distinguish a few seed types, including one or more taxa, i.e., blitum-type, crassipes-type, deflexus-type, tuberculatus-type, and viridis-type. On the other hand, seed features are not useful for other species, for example, those included in the deflexus-type (A. deflexus, A. vulgatissimus, A. cacciatoi, A. spinosus, A. dubius, and A. stadleyanus). A diagnostic key of the studied taxa is proposed. Subgenera cannot be distinguished using seed features, thus confirming the published molecular data. All these facts reveal, once again, the taxonomic complexity of the genus Amaranthus since, e.g., just a few seed types can be defined.

Comparative SEM and LM foliar epidermal and palyno-morphological studies of Amaranthaceae and its taxonomic implications.

Palynological features as well as comparative foliar epidermal using light and scanning electron microscope (SEM) of 17 species (10genera) of Amaranthaceae have been studied for its taxonomic significance. Different foliar and palynological micro-morphological characters were examined to explain their value in resolving the difficulty in identification. All species were amphistomatic but stomata on abaxial surface were more abundant. Taxonomically significant epidermal character including stomata type, trichomes (unicellular, multicellular, and capitate) and epidermal cells shapes (polygonal and irregular) were also observed. Pollens of this family are Polypantoporate, pores large, spheroidal, mesoporous region is sparsely to scabrate, densely psilate, and spinulose. All these characters can be active at species level for identification purpose. This study indicates that at different taxonomic levels, LM and SEM pollen and epidermal morphology is explanatory and significant to identify species and genera.