Turkish Journal of Botany Turk J Bot (2016) 40: 147-163 http://journals.tubitak.gov.tr/botany/ © TÜBİTAK Research Article doi:10.3906/bot-1503-51 The examinations of achene ultrastructural features of section Acrolophus (Centaurea, Asteraceae) via scanning electron microscopy 1 2, 2 2,3 2 2 Feyza CANDAN , Tuna UYSAL *, Osman TUGAY , Meryem BOZKURT , Kuddisi ERTUĞRUL , Hakkı DEMİRELMA 1 Department of Biology, Faculty of Science and Art, Celal Bayar University, Manisa, Turkey 2 Department of Biology, Faculty of Science, Selçuk University, Konya, Turkey 3 Advanced Technology Research and Application Center, Selçuk University, Konya, Turkey Received: 30.03.2015 Accepted/Published Online: 29.06.2015 Final Version: 09.02.2016 Abstract: 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. Key words: Taxonomy, Centaurea, Acrolophus, Asteraceae, fruit surface, endemic, micromorphology, Turkey 1. Introduction identification (Kaya et al., 2011). The seed coat morphology An important and relatively large genus in the flora of and microsculpturing were investigated in certain genera Turkey, Centaurea L. comprises ca. 250 species, currently of Brassicaceae and provided evidence for the close distributed over Eurasia, especially in Irano-Turanian and relationships among various genera (Koul et al., 2000; Mediterranean regions (Anderberg et al., 2007). Centaurea Moazzeni et al., 2007). These kinds of peculiarities were has one of the highest rates of endemism in Turkey, with used in the identification of families such as Brassicaceae 112 endemics among 181 total species, 18 endemics among (Cruciferae) Burnett and Scrophulariaceae Juss. (Murley, 32 subspecies, and 16 of the 28 varieties (Uysal, 2012). The 1951; Juan et al., 2000). genus Centaurea has been subjected to morphological, Plant species are traditionally examined to perform palynological, and cytotaxonomic studies for a very identification or characterization by stereomicroscopy, long time by several experts (Routsi and Georgiadis, but in many cases, when taxonomists disagree on the 1998; Villodre and Garcia-Jacas, 2000; Çelik et al., 2008; identity of taxa, the micromorphological characters of Gömürgen et al., 2010), but only a limited number of leaves, pollens, fruit, and seeds are examined via scanning studies were performed on the achene morphologies of electron microscopy (SEM) to illustrate diagnostic Centaurea in terms of shedding light on the taxonomy of differences (Shehata, 2006). Seeds display a great deal of the genus (Dittrich, 1968). variation and high morphological diversity, including Morphological and anatomical studies on the fruit valuable taxonomic information. Their shapes, colors, and and seed structures play an important role in systematics. sizes can be of high systematic significance (Chuang and Microstructural details of the fruit coat and seed make Ornduff, 1992). possible the distinguishing of the taxa (Kaya et al., 2011). The seed and fruit are both distinctive features in taxon These features, important characters for taxonomic and diagnosis of the family Asteraceae. In regards to this, there evolutionary studies, were used as parameters for species are many reports providing information for different * Correspondence: [email protected] 147 CANDAN et al. / Turk J Bot taxonomical levels and groups (Wagenitz et al., 1998; Tan cell walls not distinct. Pappus 2.6–3.8 mm. Scales present et al., 2007; Kreitschitz and Valles, 2007). The general (Figures 1a–1c). morphologies of the seeds of Acrolophus (Cass.) DC. taxa Centaurea inermis Velen.: Achenes 3.1–3.9 mm, were described simply by Wagenitz (1975) and Davis et al. ovoid-oblong; swollen, pericarp wholly cream; sometimes (1988). Although some studies were reported on the fruit- grayish lines on cream pericarp, strigose, pitted. Rotund coat surface structure of Centaurea L. species (Celik et al., at the base. Fruit coat roughish, ornamentation irregular 2005a, 2005b; Uysal et al., 2005; Aksoy et al., 2010; Okay sulcate. Cells sometimes one on another. Cells and cell and Demir, 2010; Shabestari et al., 2013; Bona, 2014), none walls distinct. Pappus 0.7–1.5 mm. Scales present (Figures of them gave comprehensive and whole information on 1d–1f). achene surface characteristics of the section Acrolophus. Centaurea kilaea Boiss.: Achenes 3.6–4.3 mm, The present study was mainly undertaken to illustrate lanceolate, swollen, pericarp wholly grayish green; the external morphology of mature seeds using SEM sometimes creamy lines on brown pericarp, strigose, and to obtain information on the achene ultrastructural not pitted. Obtuse at the base. Fruit coat roughish, construction of Acrolophus (Centaurea) taxa of Turkey. ornamentation irregular sulcate. Cells sometimes one on another. Cells and cell walls distinct. Pappus 2.3–3.0 mm. 2. Materials and methods Scales present (Figures 1g–1i). Between 2004 and 2008, many materials belonging to Centaurea cuneifolia Sm.: Achenes 3.0–4.1 mm, section Acrolophus were collected from several localities lanceolate, swollen, cream lines on grayish or brown of Turkey by our research team and the samples collected pericarp, strigose, not pitted. Obtuse at the base. Fruit were deposited in the KNYA herbarium (Table 1). coat roughish, ornamentation irregular sulcate. Cells are For SEM observation, at least 10 achenes for each taxon sometimes one on another. Cells distinct, cell walls not were dehydrated in an acetone series, critical-point-dried distinct. Pappus 0.7–1.5 mm. Scales present (Figures 1j– using carbon dioxide, and mounted on stubs using double- 1l). sided adhesive tape. Achenes were coated with gold under Centaurea zeybekii Wagenitz: Achenes 2.8–4.2 mm, JEOL JSM-6060 model SEM low-vacuum mode at about lanceolate, swollen, cream lines on brown pericarp, 20 nm in thickness for observing their surface structures puberulent, not pitted. Obtuse at the base. Fruit coat (Candan et al., 2009). SEM photographs of all taxa were roughish, ornamentation irregular sulcate. Cells usually taken at 30× size for the achenes’ general view, 1000× for one on another. Cells and cell walls distinct. Pappus 1.3– the general view of the achenes’ surface, and 2000× for 2.5 mm. Scales present (Figures 2a–2c). close views of achenes’ microstructural features. Achene Centaurea tuzgoluensis Aytaç & H. Duman: Achenes surface structural terminology follows Stearn (1983). 3.8–4.3 mm, obovoid, swollen, pericarp wholly dark Fifteen characters were investigated and used in this brown; sometimes creamy-yellow spots on brown analysis. Characters and character states were determined pericarp; sometimes brown lines on creamy white through examination of herbarium specimens stored at pericarp, puberulent, not pitted. Rotund at the base. Fruit the KNYA herbarium. Both qualitative and quantitative coat not roughish, ornamentation irregular sulcate. Cells characters were scored for numerical taxonomic studies and cell walls distinct. Pappus 1.5–2.6 mm. Scales present and constructed as a data matrix (Tables 2 and 3). A (Figures 2d–2f). similarity index indicating the relationship among taxa Centaurea olympica (DC.) K.Koch: Achenes 2.0–3.0 was generated based on the data matrix. Cluster analysis mm, obovoid, swollen, pericarp wholly brown; sometimes was performed using UPGMA methods and a dendrogram creamy lines on brown pericarp, pilose, pitted. Obtuse at based on similarity index was constructed with NTSYS PC the base. Fruit coat roughish, ornamentation irregular v.2.2 (Rohlf, 1997). sulcate. Cells and cell walls not distinct. Pappus absent. Scales absent (Figures 2g–2i). 3. Results Centaurea ulrichiorum Wagenitz, F.H.Hellw. & Parolly: In this study, the seeds of 31 taxa belonging to the genus Achenes 3.3–4.2 mm, lanceolate, compressed, pericarp Centaurea were examined micromorphologically via SEM. wholly grayish white, strigose, pitted. Obtuse at the base. Very detailed information about the structure of the seed Fruit coat not roughish, ornamentation irregular sulcate. surface taxa is given in Tables 2 and 3. Cells distinct, cell walls not distinct. Pappus 1.2–2.2 mm. Centaurea arenaria M.Bieb. ex Willd.: Achenes 2.6–3.6 Scales present (Figures 2j–2l). mm, oblong-rectangular, compressed, pericarp wholly Centaurea polyclada DC.: