Structural features of the seed coat in Caucasian representatives of Minuartia (Caryophyllaceae)

Seeds of 18 species of Minuartia L. growing in the Caucasus were studied by means of scanning electron microscope (SEM) as well as light microscope (LM). Main focus was put on characteristics of the ultrastructure of the seed surface as well as on the anatomical structure of all layers of the seed coat. Several types of seed coat structure were identified. The most important characters for systematic purposes were identified: the microrelief of the outer cells of the exotesta due to the specific structure of the cuticular layer, the type of the curvature of the anticlinal exotesta walls, the so-called 'cell junctions', the shape of the thickenings of the exotesta periclinal cell walls and the presence or absence of pronounced endotesta and tegmen layers. In total, these features turned out to be species specific for each member of the genus. In addition, a link between molecular phylogenetic data and the structure of seed coat was established.