Embryo traits and their taxonomic implications in stipoid grasses (Poaceae: Stipeae) in Asia

Abstract Micromorphological traits have been extensively used for taxonomic classification due to their high stability within species and genera. In this study, we investigated embryo variations across 49 species from 10 genera within the tribe Stipeae, primarily located in Asia, using scanning electron microscopy. Our findings indicate that quantitative traits—such as embryo size (length and width), overall shape (length-width ratio, widest position of embryo), sharpness of coleoptile—along with one qualitative trait (the presence or absence of a scutellar cleft) demonstrate stability within genera and are suitable for using as taxonomic characters. Based on nine quantitative traits, cluster analysis and principal component analyses revealed seven distinct embryo types. These embryo types are stable within genera and clearly differentiate most examined genera, which have traditionally been circumscribed mainly by lemma epidermal patterns and results of molecular systematics. Our findings further support the recognition of Patis, Timouria, and Neotrinia as independent genera, as well as the generic placements and phylogenetic relationships of several disputed species, including the reassignment of Ptilagrostis pelliotii to Achnatherum, Stipa bhutanica to Ptilagrostis and Achnatherum duthiei to Ptilagrostis. These results demonstrate the taxonomic and phylogenetic significance of embryonic traits at the genus level for the tribe Stipeae. These traits can be used for identifying generic placements of the Asian stipoid grasses during taxonomic practices.