Micromorphology of endemic Centaurea glaberrima subsp. divergens (Asteraceae)

In this study, the micromorphology of vegetative and reproductive structures endemic Centaurea glaberrima Tausch subsp. divergens (Vis.) Hayek (Asteraceae), using scanning electron microscope (SEM), is presented for first time. Uniseriate whip-like non-glandular biseriate glandular trichomes are found on surface all aboveground parts (stem, leaves, peduncles, involucral bract). On adaxial leaf epidermis ribbed thickenings (striation pattern) outer periclinal cell walls, slightly curved anticlinal walls anomocytic stomata noticed. Rugose abaxial with thorny protuberances bract documented. Corolla glabrous longitudinally parallel epidermal cells distinct straight outline. Isopolar, radially symmetric tricolporate microechinate pollen grains seen. Short stylar hairs, without cuticular striations, present along sides style, while inner (abaxial surface) constitute papillate stigmatic surface. Microcharacters in cypsela as follows: body; rotund base; lateral concave insertion; short, unicellular curly acute trichomes; smooth epidermis; fine-sulcate ornamentation; rod shaped obtuse end walls; poorly developed minutely dentate pericarp rim; dimorphic pappus bristles different length morphology, pinnules restricted to margins bristles. The results obtained contribute knowledge about studied species provide features its better identification. taxonomic significance analyzed characters discussed. Some well defined microcharacters might have value.