Anatomical and micromorphological study on some understudied taxa of Thlaspi L. s. lat. (Brassicaceae)

This study investigates the seed and fruit anatomy and micromorphology of five pennycress taxa ( Thlaspi L. sensu lato) from Turkey, some of which have not been previously investigated. Systematic work in this group suffers from a lack of comprehensive anatomical and micromorphological data, especially for narrowly endemic species. We find that seed surface structure is taxonomically more useful than seed coat anatomy in Thlaspi s. lat., but despite this, it remains understudied. Our results indicate that the most useful anatomical characters are seed-epidermis cell shape and the presence of mucilage cells. As for micromorphology, seed periclinal walls and cell shape were most significant. Thlaspi ceratocarpon Murray, the only taxa remaining in Thlaspi sensu stricto, was unique among these taxa both anatomically and micromorphologically. It notably differs from Thlaspi alliaceum L., according to our results, corroborating recent studies that placed the latter into Mummenhoffia Esmailbegi & Al-Shehbaz. Our PCoA analysis resulted in a close grouping of T. jaubertii Hedge , T. crassum P.H. Davis and T. cilicicum (Boiss) Hayek, three species that have been moved to Noccaea Moench, based on molecular evidence. We discuss the fragmentation of Thlaspi s. lat. into smaller genera in the context of broader trends in plant systematics.