Anatomical characteristics of Xeranthemum L. (Compositae) species: taxonomical insights and evolution of life form

Abstract

Comparative anatomical and micromorphological analyses of root, stem, peduncle, leaf and inflorescence have been conducted on two Xeranthemum species, X. annuum and X. cylindraceum, by light microscopy (LM) and scanning electron microscopy (SEM). The main goal of the study was to examine the most important anatomical features and to find new valid taxonomic delimiting characters for the first time in both species. Regarding vegetative organs anatomy, the data obtained in this study indicated that both species possessed secondary tissues in the root, although these plants are annual. Also, stem anatomy was a typical of the Compositae family members, and anomocytic stomata type and dorsiventral leaf structure were present. On the involucral bracts surface crystals were noticeable, while highly developed multilayer sclerenchyma was present in the mesophyll. Palea anatomy was very similar to bract anatomy. Some floral features were as follows: lateral anther dehiscence, corolla composed of uniseriate epidermis and with a homogeneous parenchyma in the mesophyll, inferior ovary and anatropous ovule with basal placentation. The specific quantitative characters that were different between the examined species were emphasized. Some selected, well defined qualitative anatomical characters (e.g. shape of the young stem and peduncle cross-sections, type of glandular trichomes and cortical vascular bundles occurrence), on the basis of which the studied species were distinguishable, strengthen the taxonomy of the Xeranthemum genus and provide features for better identification of the taxa. This is the first study of the anatomy of Xeranthemum species and some of the characters found (secondary growth and dorsiventral leaves) points towards an adaptation of mesophilous ancestors to xeric habitats in Xeranthemum.

Stem anatomical survey of the genera Matricaria and Tripleurospermum (Asteraceae) from Turkey with its taxonomical and ecological implications

“…Ozcan & Demiralay (2018) re-ported these types of cortical bundles in the stems of some Turkish Cirsium taxa. These bundles have also been reported by Gavrilović et al (2016) in Xeranthemum annuum L. from Serbia and by Gavrilović et al (2020) in Amphoricarpos neumayerianus (Vis.) Greuter from Montenegro, respectively.…”

Comparative anatomical investigation of five Artemisia L. (Anthemideae, Asteraceae) species in view of taxonomy

“…sinaitica (Bakr 2014) regarding isolateral leaf structure and amphistomatous leaves with large stomatal chamber, but in contrast to leaf anatomy of two varieties of A. absinthium, where stomata were found only on the abaxial side and where bifacial leaf structure was described (Konowalik and Kreitschitz 2012). Although leaf mesophyll, in Asteraceae plants, typically contains palisade and spongy tissue (Duarte et al 2011;Jane et al 2011;Gavrilović et al 2018b), it is known that leaf anatomy often reflects environmental factors too. Plants with isolateral leaf structure usually grow on dry habitats with intense solar radiation, shown for the genera Aster L., Galatella Cass., Tripolium Nees.…”

“…Likewise, all other vegetative anatomical characters are also useful in taxonomic studies and are important in perceiving phylogenetic relationships of particular plant groups (Lersten and Curtis 2001;Dengler 2002). Anatomical data also may provide useful and valuable characters which may 1 3 help in identification of ambiguous plant taxa, as well as establishing their taxonomic relationships (Metcalfe and Chalk 1957;Scatena et al 2005;Sosa et al 2014;Karanović et al 2015;Gavrilović et al 2018b). Also, micromorphological characteristics, e.g., trichomes, have played an important role in plant taxonomy at generic and species levels (Hayat et al 2009;Gavrilović et al 2018b).…”

Leaf and stem anatomy and micromorphology of four Inuleae (Compositae) genera, with notes on their taxonomic significance

“…However, anatomical and micromorphological features of the vegetative organs of Inula, Dittrichia, Limbarda and Pulicaria are not documented in sufficient detail, as research focus has been limited to a few species of economic or medicinal value (Nikolakaki and Christodoulakis 2004, Sulborska 2007, Toma et al 2010. The taxonomic significance of leaf and stem anatomy and micromorphology has been confirmed in a number of studies of Compositae (Breitwieser 1993, Adedeji and Jewoola 2008, Sosa et al 2014, Karanović et al 2015, Gavrilović et al 2019, Janaćković et al 2019, Ulukuş and Tugay 2020.…”