Seed-coat microsculpturing of selected <i>Noccaea</i> Moench and <i>Thlaspi</i> L. species (Brassicaceae: tribes Coluteocarpeae, Thlaspideae) and its taxonomic significance

4 October 2018

Antkowiak, Wojciech; Klimko, Malgorzata; Janyszek, Magdalena

Seed of 25 species of Noccaea and 3 species of Thlaspi s.str. from Europe, Southwestern Asia and North Africa have been studied using scanning electron microscopy. 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 are presented. 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 fine folds and rugulate. The pattern of the epicuticular wax is platelets. SEM examinations at higher magnifications revealed 5 types of seed surface sculpture: colliculate, reticulate, mixed (colliculate-reticulate), verrucate and foveolate in Noccaea as well as ribbed and reticulate patterns in Thlaspi s.str. SEM studies of the taxa have shown that the seed patterns are species-specific and support the clear distinction between Noccaea and Thlaspi. Our results suggest that some species of Noccaea cannot be separated based on seed size and shape, but may only be identified to their groups. Micromorphological features of seed surface are of taxonomic importance both for the differentiation between the genera Noccaea and Thlaspi and within these two genera. A key for the identification of the investigated taxa based on the micromorphological characters is provided. The present study investigated seeds of 28 taxa for the first time in terms of seed micromorphology and provided some important new data.