Seed structure of some taxa of the genus Crocus L. (Iridaceae) series Crocus

Turkish Journal of Botany Turk J Bot (2018) 42: 722-731 © TÜBİTAK doi:10.3906/bot-1712-17 http://journals.tubitak.gov.tr/botany/ Research Article Seed structure of some taxa of the genus Crocus L. (Iridaceae) series Crocus 1, 2 1 1 Mehmet Cengiz KARAİSMAİLOĞLU *, Levent ŞIK , Almıla ÇİFTÇİ , Osman EROL  Division of Botany, Department of Biology, Faculty of Science, İstanbul University, İstanbul, Turkey 2 Department of Biology, Faculty of Arts and Sciences, Celal Bayar University, Manisa, Turkey 1 Received: 08.12.2017 Accepted/Published Online: 19.06.2018 Final Version: 22.11.2018 Abstract: In this study, the macro- and micromorphological seed characteristics of the genus Crocus L. series Crocus taxa, including C. pallasii, C. turcicus, C. dispathaceus, C. asumaniae, C. mathewii, C. thomasii, C. oreocreticus, and C. cartwrightianus, were observed. Morphological characteristics, such as the size, shape, color, and seed surface structures, were analyzed using stereo and scanning electron microscopes. Testa layer structures including the outer and inner testae, phytomelan layer structure and thickness, and seed endosperm cell features were studied. Differences in the seed, raphe size, seed surface patterns, inner testa features, and phytomelan layer thickness were observed at an interspecific level. The results revealed differences in the seed morphology and anatomy with a few exceptions. Key words: Crocus, seed, morphology, anatomy, scanning electron microscopy, phytomelan layer 1. Introduction Crocus L. (Iridaceae) comprises 235 taxa (Petersen et al., 2008; Kerndorff and Pasche, 2011; Peruzzi and Carta, 2011; Carta et al., 2015; Ruksans, 2017), and is distributed from West Europe and Northwest Africa to West China, with the center of species diversity in the Balkan Peninsula and Turkey. Turkey is the richest country with 137 Crocus taxa (Harpke et al., 2012; Ruksans, 2017). Different conventional morphological features used in Crocus taxonomy with regards to possibly distinguishing monophyletic groups within the genus have been reported in the literature (Harpke et al., 2012, 2014; Carta et al., 2015), in which it was found that none of the traditional morphological features were suitable for discriminating Crocus sections or series. This status has caused some problems in their classification; therefore, additional characteristics that can assist the existing diagnostics are needed for the classification of Crocus taxa. Crocus seed color, structure, and surface sculpture are of much importance in terms of taxonomical applications (Maw, 1886). However, with the exception of a few studies (Kujat and Rafiński, 1978; Grilli Caiola et al., 2010; Carta et al., 2015), Crocus seed has not been a popular research subject. Mathew (1982) attributed this situation to the fact that the capsules and seeds of crocuses flowering in either autumn or spring reach maturity during April and May. According to our experiences from field observations, it is hard to find and collect capsules on the ground when vegetation is dense and tall. Therefore, Crocus seed studies require the cultivation of related taxa and capsule and seed harvesting should be done carefully. Seeds and fruits may possess various macro- and micromorphological structures that can provide valuable information for plant taxonomy. The shape, color, size, and especially microstructure (including anatomical features) of the seeds and fruits are valuable information for plant systematics (Kerndorff et al., 2015). There have been many plant epidermal surface analyses using scanning electron microscopes (SEMs). According to Barthlott (1981), surface characteristics can basically be divided into 4 main groups: 1) cellular arrangement, 2) shape of the cells, 3) relief of the outer cell walls, and 4) epicuticular secretions. These characteristics vary widely among species and at the family level, and are not easily affected by environmental conditions. Moreover, Kerndorff et al. (2015) stated that the microstructures of Crocus seed testae are very taxonomically valuable, and just this character alone can be adequate for a systematic grouping of the genus. In addition, the seed anatomical characters are generally as useful as the morphological characters for plant identification and are frequently used in the discrimination of closely related taxa (Karamian et al., 2012; Karaismailoğlu, 2015). * Correspondence: 722 This work is licensed under a Creative Commons Attribution 4.0 International License. KARAİSMAİLOĞLU et al. / Turk J Bot The main aim of this study was to investigate the morphological and anatomical seed characteristics of subgenus Crocus, section Crocus, series Crocus of Crocus L. taxa, including C. pallasii Goldb., C. turcicus (Mathew) Ruksans, C. dispathaceus Bowles, C. asumaniae Mathew, C. mathewii Kerndorff & Pasche, C. thomasii Ten., C. oreocreticus B.L.Burtt, and C. cartwrightianus Herb., following the new combinations of Ruksans (2017), to detect the variations and specificities in the seed morphology and anatomy of the studied taxa with the use of statistical analysis. This is the first study describing both the micromorphological and anatomical seed structures of these taxa in detail. 2. Materials and methods The observed taxa were analyzed using 10 seeds from each taxon, and their origins and İstanbul University Science Faculty Herbarium (ISTF) data are presented in Table 1. All the taxa were cultivated at the İstanbul University Alfred Heilbronn Botanical Garden in clay pots filled with sand, loam, clay, and a small amount of sheep manure. The seeds were harvested between 03.04.2013 and 01.06.2013, just before the dehiscence of the capsules. Seed macromorphological features, such as the color, shape, size, and raphe structure, were analyzed using an Olympus ZS51 stereomicroscope and Kameram imaging software. Furthermore, to examine structures such as the type, intensity, and hair length, the presence of secondary structures on the hairs, papillae, primary structure, and specimen cell sizes, samples were micromorphologically prepared for electron microscopy by mounting them on a stub with silver adhesive, coating them with gold, and analyzing them with JEOL Neoscope-5000 SEM at 10 kV. In addition, anatomic cross-sections of the seeds were studied by a fully automatic microtome (Thermo Shonda Met Finesse) from the middle of the seeds. Afterwards, they were passed through a variety of alcohol and xylene series and stained with hematoxylin (Harris- Table 1. Examined taxa and their origins. No. Specimen no. Taxon Locality ISTF number 1 SC1 C. pallasii Muğla, 28.10.2009 40176 2 SC2 C. pallasii Muğla, 28.10.2009 40177 3 SC5 C. pallasii Muğla, 29.10.2009 40179 4 SC7 C. pallasii Muğla, 29.10.2009 40181 5 SC8 C. pallasii Muğla, 29.10.2009 40182 6 SC10 C. pallasii İzmir, 20.11.2009 40666 7 SC12 C. pallasii Denizli, 24.11.2009 40668 8 SC17 C. pallasii (...truncated)