Taxonomic Significance Of Seed-Coat Microsculpturing In Noccaea Moench And Thlaspi L. (Brassicaceae: Coluteocarpeae, Thlaspideae)

We studied seeds of 25 species of Noccaea and 3 species of Thlaspi s.s. from Europe, southwestern Asia and northern Africa using scanning electron microscopy (SEM). Macro- and micromorphological characters, including seed shape, the size and shape of epidermal cells, anticlinal boundaries, outer periclinal cell walls and the outlines of outer cell walls were recorded. Two types of anticlinal cell wall boundaries were recognised and 5 different shapes of outer periclinal walls are described. The secondary sculpture of the cell walls varies from smooth to striate, micro-papillate to finely foled and rugulate. The epicuticular wax comes in platelets in all the species. SEM examinations at higher magnifications revealed 5 types of seed surface sculpture: colliculate, reticulate, mixed (colliculate-reticulate), verrucate and foveolate in Noccaea, in addition to ribbed and reticulate patterns in Thlaspi s.s. SEM studies of the taxa showed that the seed patterns are species-specific and support a clear distinction between Noccaea and Thlaspi. However, some species of Noccaea cannot be separated based on seed size and shape, but may only be identified to their groups. Micromorphological features of the seed surface are thus of great value, both for the differentiation between the genera Noccaea and Thlaspi and for the species-level taxonomy. A key to the identification of the investigated taxa based on the micromorphological characters is provided.