Chromosome numbers of 17 taxa of Hieracium s.str. from Bulgaria, Greece, Poland and Romania are specified and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. engleri R. Uechtr. (4x), H. kritschimanum Mattfeld & Zahn (3x), H. latifolium Link (3x), H. tephrosoma subsp. amaurocranum Zahn (5x), as well as five undescribed species belonging to the H. lachenalii agg. (3x), H. rohacsense agg. (4x), H. vagneri agg. (4x), H. vranjanum agg. (4x) and H. wiesbaurianum agg. (3x), and a new hybrid between H. caesium s.lat and H. umbellatum (4x).

Cell wall components, especially arabinogalactan proteins (AGPs) and pectins as the source of signaling molecules active in cell-to-cell communication, are involved in many biological processes, including plant growth and development. Understanding the mechanisms of intercellular communication is particularly important in the context of reprogramming cell fate and transition from somatic to germline identity. The present study focuses on immunodetection of some pectic epitopes and AGPs in young ovules of selected Hieracium, Pilosella and Taraxacum species. The purpose of this research was to answer the questions: (1) whether the distribution of pectins and AGPs is related to the mode of reproduction and (2) whether their spatial and temporal distribution in young ovules may herald a later differentiation of the nutrient tissue present in the integument of mature ovules. We analyzed the localization of low and highly methyl-esterified pectins and AGP epitopes using monoclonal antibodies, i.e., LM19, LM20, JIM13, respectively. Our research found no significant differences in the localization of pectins and AGPs in young ovules of sexual and apomictic species, and the initial distribution pattern of these compounds did not appear to be related to the subsequent differentiation of the periendothelial nutrient zone. The presented findings may confirm the existence of a general developmental trend in the spatial and temporal distribution of pectins and AGPs during the maturation of ovules in angiosperms.