The Anatomical Characteristics of Endemic Aethionema dumanii Vural & Adıgüzel (Brassicaceae)

The present study deals with the anatomical properties of Aethionema dumanii, which is an endemic species growing in Salt Lake (Konya). The stem cross-sections have a single-layered epidermis, parenchymatous cortex, vascular bundles, and pith cells. An equifacial mesophyll type was observed in the leaves with multiple-layered palisade tissue, but the spongy parenchyma was reduced. Vascular bundles were smaller. The cross-sections of fruit had single exocarp, 3or 4-layered mesocarp, and single-layered endocarp. Transverse sections of the seed showed an epidermis, palisade tissue, endosperm, and embryo. The anatomical characteristics of A. dumanii has been found to have valuable taxonomic importance. Research Article Article History Received : 05.11.2019 Accepted : 27.12.2019


INTRODUCTION
The family Brassicaceae is represented by 321 genera and about 3660 species worldwide, and at such high numbers, it is known as a significant dicot family (Al-Shehbaz, 2012). In Turkey, the list of this family is composed of 91 genera and 686 taxa (Güner et al. 2012). The major distribution centres of the family are the Mediterranean, Irano-Turanian, and Saharo-Sindian regions (Hedge, 1976). Turkey is one of the richest countries in this respect, with 653 native species belonging to 61 genera in the family Brassicaceae (Al-Shehbaz et al. 2007).
Aethionema dumanii is a perennial, dwarf, and endemic plant that only grows in salty areas. There have been no anatomical studies about this halophytic species.
In this study, A. dumanii endemic plant, which is only known from Salt Lake, were evaluated using their anatomical characteristics, both vegetative organs, fruit, and seeds.

MATERIAL and METHODS
The plant materials were collected from Salt Lake in the province of Konya. Some were prepared according to standard herbarium techniques, while others were placed into 70% ethyl alcohol. The paraffin method was used for the vegetative organs, fruit and seed of the studied taxa for cross-sections (Johansen, 1940). 5 plant samples were used and the experiments were done at least 3 times. The vegetative and generative organs of the species were cut into small pieces. Next, they were treated through an increasing alcohol series to remove the water from the tissues. As the next step, a portion of paraffin was added to small glass flasks. The paraffin blocks were made and 12-16-µm-thick transverse sections were cut using a Leica microtome with disposable blades. The safranin-fast green were used for dying anatomical sections. Under a light microscope (Leica DM 1000), the best sections were chosen and photographed at magnifications of 10x, 20x, and 40x. The measurements, which were made with the Kameram 21 software programme, were based on at least 30 or more cells per specimen. The mean values of the measurements of all of the investigated taxa were given (Table 1). If the paraffin method was unsuccessful, cross-sections were taken by hand using a razor blade. Permanent slides were observed under a Leica DM 1000 light microscope (LM). Measurements were made using the Kameram 21 programme and photos were taken with a Canon EOS 450D camera that was attached to the LM. The stomata were classified based on the criteria of Metcalfe and Chalk (1954).

Stem anatomy
Four main anatomical regions were determined in the cross-sections of the stems. These layers could be counted from the peripheral to the centre, as the epidermis, cortex, vascular bundles, and pith regions ( Figure 1-A). The outermost surface of the stems was limited to rectangular-shaped epidermis cells with 8.47-12.08 × 12.03-25.05 µm (Table 1). Ten or 11 rows of cortex cells, which were parenchymatous, followed the epidermis towards the centre and their shape is defined as oval. The single-lined vascular bundles were composed of the xylem and phloem with sclerenchyma above them and they are well-developed. The pith region was fully filled with oval-shaped parenchymatous cells and their size were measured as 35.7×70.8 µm (Figure 1-B).

Leaf anatomy
The cross-sections of the leaves of the studied species had 2 epidermis with mesophyll tissue and their shapes were determined as rectangular-oval ( Figure  2). The mesophyll was equifacial and composed of 4 or 5 rows of palisade and reduced spongy parenchyma cells. The vascular bundles of the leaf were arranged in a single line and the median one is the biggest. The other vascular bundles were smaller than the median one.
The leaves of A.dumanii are amphistomatic and the stomata was observed as anizocytic type according to with the level of epidermis ( Figure 3). The shapes of epidermis cells are irregular or polygonal. The cell walls of epidermis cells are smooth (Figure 3-A,B). The stomatal index in upper surface was calculated as 33.3 and, 29.3 in lower surface and the ratio of stomata index 1.13.

Fruit anatomy
The transverse sections of the fruit were triangularshaped and the pericarp was composed of a lined exocarp, 3 or 4 rows of mesocarp, and a single-layered endocarp (Figure 4-A). The vascular bundle was located in the endocarp layer (Figure 4-B).   The cross-sections of the seed determined the integuments, endosperm, and embryo ( Figure 5-A). The seed cross-sections showed that there was a singlelayered epidermis. Single-layered palisade tissue was under the epidermis, as well as crushed palisade tissue. The endosperm layer was composed of rectangular-oval-shaped cells (Figure 5-B). The embryo was present in the seeds.

DISCUSSION and CONCLUSION
The present work is the first report about the anatomical traits of the vegetative organs, fruit, and seeds of A. dumanii in the family Brassicaceae.
Investigations conducted regarding the anatomical traits of the genus Aethionema are little-known (Atçeken et al., 2016, Karaismailoğlu, 2019. The epidermis in the stem was similarly shaped, but they were different with regards to the number of layers. A. dumanii had a single-lined epidermis, similar to A. arabicum and A. karamanicum (Atçeken et al., 2016). However, some Aethionema taxa (A. cordatum and A. armenum) have a 2-or 3-rowed epidermis in their stem anatomy (Atçeken et al., 2016). The cortex was parenchymatous, and sclerenchymatic groups were placed above the vascular bundles in A. dumanii. Atçeken et al. (2016) declared that A. karamanicum and A. armenum had sclerenchyma above the vascular bundles, but that was not present in A. arabicum and A. cordatum. Unifacial and equifacial mesophyll in the genus Aethionema were reported by Atçeken et al. (2016). According, in our study, A. dumanii had equifacial mesophyll in its leaf anatomy. Moreover, the palisade parenchyma was well-developed in the leaves of A. dumanii and increasing palisade tissue occurred in the habitat (salty soils) of A. dumanii.
The fruit and seed anatomical properties contained essential information about the taxonomy of the family Brassicaceae (Mummenhoff et al., 2008;Mühlhausen et al., 2010;Lenser et al., 2016). In many Brassicaceae species, a living endosperm layer around the embryo plays an essential role in the regulation of the germination and dormancy of the seeds (Müller et al. 2006;Graeber et al. 2012 species of Aethionema are also examined. In conclusion, A. dumanii was studied in the present work and the anatomical characteristics of stem, leaf, fruit and seed were determined for the first time.