Seed Morphology of Some Barbarea (Brassicaceae) Taxa

The seed macroand micromorphologies of four taxa (Barbarea auriculata Hausskn. ex Bornm. var. auriculata, Barbarea trichopoda Hausskn. ex Bornm., Barbarea verna (Mill.) Asch. and Barbarea vulgaris R. Br. subsp. vulgaris) belonging to Barbarea R. Br. were investigated with scanning electron microscopy (SEM). Significance of seed features as taxonomic characters including seed color, shape, winged, measures, seed coat pattern were determined. Two coat patterns were observed; irregularly-reticulate and tuberculatereticulate, and three shapes were distinguished; broadly oblong, oblong and broadly elliptic. The results showed that the morphological characteristics of seed could be contribute as criteria to distinguish taxa. This is the first SEM study about seed surface of any Barbarea taxa. Research Article Article History Received : 23.01.2020 Accepted : 19.03.2020


INTRODUCTION
Brassicaceae is one of the largest family in the Angiospermae, and is easily distinguished by its flower and fruit characteristics. Brassicaceae comprises cosmopolitan plants that are mainly distributed in temperate zones and the Mediterranean region; this family of plants is represented by 338 genera and 3,709 species (Warwick et al., 2006). Barbarea R.Br. species are distributed in the warm regions of Eurasia, Australia, and North America; in some South American countries; and in the eastern parts of Africa. This genus is represented by 29 species throughout the world and 13 species and 18 taxa distributed in Turkey (Bağcı, 2012). The morphological characters Brassicaceae, especially those of the fruits, seeds, and cotyledons, are used in the tribal separation within the family (Bentham and Hooker, 1862). The morphology of the seed coat patterns are considered as stable characteristic and minimally affected by external environmental conditions (Heywood, 1971;Cole and Behnke, 1975;Barthlott, 1981;Barthlott, 1984). In this study, the seed macro-and micromorphologies of four taxa; Barbarea auriculata Hausskn. ex Bornm. var. auriculata, Barbarea trichopoda Hausskn. ex Bornm., Barbarea verna (Mill.) Asch., and Barbarea vulgaris R.Br. subsp. vulgaris were investigated with scanning electron microscopy (SEM). Seed surfaces, color, and size are valuable characteristics for distinguishing taxa belonging to genera such as Alyssum L., Alyssoides Tourn. ex Adans., Berteroa DC., Clypeola L., Fibigia Medik., Lobularia Desv., Ptilotrichium C.A.Mey., Arabis L., Cardamine L., Cardaminopsis Hayek, Nasturtium Mill., Rorippa Scop., Boleum Desv., Brassica L., Cakile Mill., Calepina Adans., Conringia Heist. ex Fabr., Diplotaxis DC., Eruca Mill., Erucaria Gaertn., Erucastrum C.Presl, Moricandia DC., Raphanus L., Sinapis L., Succowia Medik., Armoracia G.Gaertn., B.Mey. & Scherb., Draba L., Hesperis L. and Lepidium L. (Vaughan and Whitehouse, 1971;Barthlott, 1981;Koul et al., 2000;Karaismailoğlu, 2019). The main objective of this study is to examine and describe the seed coat of some taxa of Barbarea growing in Turkey by using scanning electron microscope and to be reference in future research about rest of the Barbarea species or related genera.

MATERIAL and METHODS
The study material comprised samples of ripe seeds from four taxa belonging to Barbarea collected from natural habitats in Turkey between 2015 and 2017.
The samples were stored at Konya Selçuk University Faculty of Science Herbarium (KNYA). The locations and collector registration numbers of the taxa studied are provided in Table 1; the seed micromorphology characteristics are provided in Table 2. Twenty seeds from each taxon were examined in our study. Samples examined in our analyses using scanning electron microscopy (SEM) were first passed through a series of 70, 80, 96, and 100% alcohol for 20 min each. The surfaces were then observed and photographed with the scanning electron microscope at 30x, 1000x, and 2000x magnification in high vacuum mode. The seed micromorphology terminology used was according to Stearn (1992), Koul et al. (2000), and Zeng et al. (2004).

RESULTS and DISCUSSION
The micrographs from the seeds of the four taxa studied are shown in Fig. 1 and the macro-and micromorphological properties of the seeds are provided in Table 2.
Barbarea auriculata var. auriculata: Seed dark brown to black, broadly oblong, unwinged, glabrous, 1.41-1.52 x 1.01-1.12 mm and the seed coat pattern is irregularly reticulate (Table 2, Figure 1).  Figure 1). SEM studies showed that seed, fruit, and leaf surface model characteristics are useful for describing different families and genera (Kumar et al., 2012;Shavvon et al., 2012;Akçin et al., 2013). In general, oblong seeds were observed in the taxa used in our study. Similarly, Gabr (2018) have reported oblong seeds for Raphanus sativus L., Cakile arabica Velen., and Sisymbrium irio L., none of which are related to Barbarea. Vaughan et al. (1971) have reported the seed shapes to be orbicular to oval for B. verna and B. vulgaris; however, according to Stearn (1992), it is more appropriate to describe the shape of B. verna seeds as broadly elliptical and the shape of  Ghaempanah et al. (2013) have reported a glabrous structure in Erysimum L. species that are not related to those of Barbarea.
The studied characteristics were not distinctive for Barbarea in genus level but the shape and size of the seeds and that seed coat patterns can be used as distinctive characteristics among the studied taxa. In future seed morphology studies about the rest of the Barbarea species will contribute to the interpretation of relationships of the taxa.