Structural Features of the Leaf of Ephemeral Species of Representatives of the Brassicaceae Burnett Family in Southwestern Kyzylkum (Uzbekistan)

The results of a study conducted by light microscopy of the anatomical structure of the leaf in ephemeral species from the family Brassicaceae growing under the conditions of Kyzylkum (Uzbekistan) are presented. The following diagnostic, structural adaptive features were revealed: a leaf lamellar, dentate (Diptychocarpus strictus), in Leptaleum filifolium—valky. It is pubescent with various types of trichomes: stellate, dendroid (Meniocus linifolius), equilater-al (Streptoloma desertorum) and unequal (Strigosella, Leptaleum filifolium species), unicellular hooked (Leptaleum filifolium). Epidermal cells flattened with wavy or winding walls. The stomata are numerous, not submerged, anomocytic, hemiparacytic, anisocytic types are noted. In all species, the iso-late-palisade type of leaf mesophyll predominates. Vascular bundles of all species are sclerified. The main protective features of the leaf of species of the family Brassicaceae are pubescence and sclerification of vascular bundles. We consider the mesomorphic and xeromorphic lines of development ancient and independent. Identified and described signs that can be used in taxono-my and ecology.


Introduction
The Brassicaceae family is very polymorphic, widely distributed mainly in the northern hemisphere (Mediterranean, Western and Central Asia), including 372 genera and more than 4 thousand species. A distinctive feature of the family is the abundance of biennial monocarpic (that is, blooming only in the last year of life) herbs [1] [2].
The leaf organs of the ephemera attract the attention of researchers, due to their lability to environmental conditions. The study of their structure in the ontogenesis of plants determines the strategy of adaptation of plants, that is, the path of adaptation during the transition from germinal leaf organs (cotyledons) to the leaf. There is evidence of the leaf structure of several species from different habitats ephemers: Karakum [3], the foothills of Western Tien-Shan [4] [5] and Kopetdag [6]. The type of leaf mesophyll of some types of ephemers of Kyzylkum and the ratio of palisade and spongy tissues are reflected in the works of G.F. Begbaeva [7] [8] [9] [10], G.S. Tursinbaeva and A.A. Butnik [11].
In the capital summary C.R. Metcalfe and L. Chalk [12] noted that leaf trichomes of the species of the family Brassicaceae are very diverse; mesophyll is predominantly dorsiventral, but it is also isolated-palisade. The stomata are anisocytic on both sides of the leaf. Idioblasts with myosin are present in all organs, which, when coagulated, turns red or purple, which can be used as a diagnostic sign. E.I.
Volkova [6] studied the structure of 10 species of ephemers, including Brassicaceae species, in the conditions of Kopetdag and the Moscow Region. She noted a variety of leaf types and an increase in mesomorphic under conditions of introduction in the Moscow region. N. Rao and I. Inamdar [13] described the morphology and leaf venation of 35 species of Brassicaceae, including species of the genus Alyssum: leaves are simple, regular, but the shape of the plate is very diverse. Venation is mainly kraspedromny. G.F. Begbaeva [7] described the type of leaf mesophyll in 2 species of Isatis. Isatis species are valuable in nutritional plants, and contain all the essential amino acids and a significant amount of carbohydrates [14]. Thus, information on the leaf structure of desert species of Brassicaceae is scarce.

Materials and Methods
The objects of research are 13 species of ephemeral representatives of Brassicaceae Burnett family, growing in southwestern Kyzylkum: Diptychocarpus strictus Trautv., Goldbachia laevigata DC., Hymenolobus procumbens Nutt., Isatis minima Bunge., Isatis viollascens Bunge., Lachnoloma lehmanii Bunge., Leptaleum filifolium DС., Meniocus linifolius (Willd.) DC., Strigosella africana (L.) Botsch., Strigosella grandiflora (Bunge) Botsch., Strigosella scorpioides (Bunge) Botsch., Streptoloma desertorum Bunge., Tauscheria lasiocarpa Fisch (Figure 1  Sections were made with a dangerous razor, stained with methylene blue, glued to glycerin-gelatin. The shape and shape of the main epidermal cells are described by the method of S.F. Zakharevich [19]. The measurements were carried out according to the standard technique [20]. The preparations were drawn using the RA-6 drawing apparatus under the MBI-3 microscope. The measure-American Journal of Plant Sciences ments were carried out in thirtyfold replicates, calculated in average value, measurement errors and significance by B.A. Dospekhov's formula [21] using a personal computer (MS-Excel program).       Leptaleum filifolium DС. A leaf 3 -3.5 cm long, divided into 5 -6 narrow (1 -1.5 mm wide) lobes, pubescent with 1 -2 radial hairs with curved hook-shaped ends of the rays. On the adaxial side above the vein, a recess is noticeable, with the abaxial side, a protrusion. The epidermis is single-row. On the adaxial side, the cell walls are slightly wavy, on the abaxial side, meandering, the outer walls of the cells thickened. The leaf is amphystomatic. The stomata are small, nu-merous, anomocytic, less often hemiparacitic, not submerged. There are no stomata on the adaxial side above and below the main vein. In cross section, the proportion of a crescent-shaped leaf with blunts ends. Mesophyll is isolateral-palisade with 3 rows of palisade cells on both sides of the plate, between them 4 -5 rows of spongy cells. The intercellular spaces are large. On the cross section of the leaf lobe, 4 large vascular bundles and 5 -6 small ones pass. The main and large lateral vascular bundles with 15 -20 vessels are surrounded by a sclerenchymal lining. The leaf is xeromorphic due to the reduction of the evaporating surface (narrow lobes), the thickened outer walls of the epidermis, the isolate-palisade mesophyll (3 rows of cells on each side) and the sclerification of the vascular bundles ( Figure 8).

Results and Discussion
Meniocus linifolius (Willd.) DC. The leaf is linear, solid, 3 -3.5 cm long, and 3 -4 mm wide, pubescent with stellate hairs. The epidermis is single-row, from the surface of flattened cells with slightly wavy, often straight walls. The stomata are small, numerous, not submerged, anomocytic, hemiparacitic and paracytic, arranged randomly. Mesophyll is isolated-palisade ( Figure 9).   Tauscheria lasiocarpa Fisch. The middle leaf is lamellar with a heart-shaped base, sessile, with an outstanding main vein. The epidermis is single-row, from the surface of the cell are flattened, their walls are winding, on a cross section with a thickened outer wall. The leaf is amphystomatic. The stomata are numerous, small anomocytic and hemiparacytic, not submerged. Mesophyll is isolated-palisade. On the adaxial side, 2 rows of large palisade cells, on the abaxial side, 1 row. Between them 4 -5 rows of loose spongy parenchyma ( Figure 14).
The intercellular spaces are large throughout mesophyll. The median bundle is sclerified from the abaxial side, the vessels are few ( Figure 14).
Thus, the leaf of the species of the Brassicaceae family is lamellar, dentate

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.