The examinations of achene ultrastructural features of section Acrolophus (Centaurea, Asteraceae) via scanning electron microscopy

In this study, the achene surfaces of 31 taxa belonging to the genus Centaurea L. were examined in detail by means of electron microscopy. The main aim of this study was to characterize the microsculpture of the achene surface of the Turkish species of Centaurea sect. Acrolophus (Cass.) DC. (Asteraceae). Detailed descriptions of the achene surface were given for each taxon and a fruitful dendrogram was established by numerical analyses derived from the determined micromorphological features. The relationships among the taxa studied were briefly assessed using this generated dendrogram. The results indicated that the examined taxa had very high variations regarding their achene surfaces and these variations have great importance in determining the taxonomic relationships of the discussed taxa. According to the results, pericarp texture and color could be used for taxonomical diagnosis of the Acrolophus species because they contain differences over a broad spectrum. The fruit coat was usually roguish and its ornamentation was fairly variable; therefore, this taxonomical microcharacter might also be useful in distinguishing closely related taxa. The hairiness of the surface of the pericarp was characteristic in all Acrolophus species and it would be evaluated as a decisive micromorphological character of the section within the genus.