Pollen morphology of Centaurea L. (Asteraceae) in Iran

Abstract

The genus Centaurea L. is one of the largest genera in the family Asteraceae. The number of taxa included in this genus ranges from 500 to 600 worldwide. Iran is one of the major centers of diversity for this genus. Pollen morphology has proved useful in the systematics of Asteraceae, as well as in that of some of its genera and species. The pollen morphology of 19 taxa of the genus Centaurea was investigated in detail by light and scanning electron microscopy. Examination under light microscopy showed pollen grains to be tricolporate, isopolar, radially symmetrical, oblate spheroidal, prolate spheroidal, subprolate, tectum perforate and scabrate. Based on the exine ornamentation observed under scanning electron microscopy, we identified two types of pollen grains, designated type I (dense acute spinules) and type II (sparse spinules). All of the taxa evaluated resemble Wagenitz's Jacea type. We present micrographs of pollen grains, together with descriptions of the characteristics of their structure. We found that the pollen characters (shape, exine structure, sculpturing) were useful for classification.

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

“…Our work is the first important study that explains in detail the external morphology and the ultrastructural formation of mature achenes for Acrolophus (Centaurea) taxa by using SEM. As reported in previous studies (Celik et al, 2005a;Aksoy et al, 2010;Bancheva and Gorgorov, 2010;Shabestari et al, 2013;Bona, 2014), Centaurea species have great variation in terms of achene micromorphology, which has great importance in identifying the species taxonomically. Unlike some genera of Asteraceae, Centaurea species have smooth and ribbed achene surfaces and different types of pappus that provide dispersal of seeds by wind.…”

Systematic implications of achene characteristics in genera <i>Centaurea</i> L., <i>Cyanus</i> Mill., <i>Psephellus</i> Cass. and <i>Rhaponticoides</i> Vaill. (Asteraceae)

“…Though previous studies support the use of achene surface patterns as diagnostic characters at species and subspecies levels for the genus Centaurea s.l., understanding the importance of these characters at generic and subgeneric levels requires further studies (Uysal et al, 2005;Çelik et al, 2005a, b;Aksoy et al, 2010;Okay and Demir, 2010;Shabestari et al, 2013;Bona, 2014;Candan et al, 2015). With this in mind, this study examines the exomorphic achene characters of 23 taxa belonging to the genera Centaurea, Cyanus, Psephellus and Rhaponticoides in Asteraceae by using light microscope (LM) and scanning electron microscope (SEM).…”

Cypsela micromorphology and anatomy in Cirsium sect. Epitrachys (Asteraceae, Carduoideae) and its taxonomic implications

“…Fruit and seed ornamentation provide a useful tool for taxonomy and its potential values have been recognized in several plant groups (Sheikh Akbari and Azizian 2006, Kaya and Dirmenci 2008, Pınar et al 2009, Bayrakdar et al 2010, Shabestari et al 2013, Hussein and Eldemerdash 2016. Achene morphology provide relatively constant characters that is relatively less affected by the growth environment (Sears 1922).…”