INVESTIGATION OF MICROMORPHOLOGICAL AND ANATOMICAL FEATURES
OF SPECIES ONOSMA L. SPREADING IN THE PROVINCE OF BINGÖL
Abstract
In this study, six Onosma L. (Boraginaceae) species which is five endemic in Bingöl
province, (Onosma rechingeri H. Riedl., Onosma neglectum H. Riedl., Onosma sericea Willd.,
Onosma proballantherum Rech. fil., Onosma stenoloba Hausskn. ex H. Riedl..) was studied for
the first time in comparatively micromorphological and anatomical terms.
In anatomical
investigations, cross-sections of the body and leaves of the species were examined, and
anatomically comparisons were made between the species. In micromorphological studies, body
and leaf epidermal surfaces and seed surface were examined and the characteristics obtained
were presented in tables. Although the anatomical structure of the body shows a similar
structure in almost all the investigated species, it has been determined that the leaf mesophyll
structure differs anatomically from the species. The type of stoma is amphistomatic
INTRODUCTION
According to the classification system of Cronquist, the Boraginaceae family was
included in the Asteridae sub-class and Lamiales Ordo of the Magnoliopsida class of
angiosperms (Cronquest, 1981). It has been determined that the Boraginaceae family, which is
ninth among the families of the most species in Turkey, is represented by 44 species and 375
taxons in the flora of Turkey (2). One hundred three endemic taxons represent approximately
50% of the Onosma species in Turkey Flora (Güner et al 2012; Binzet, 2016).Austria made
Onosma L. that grows in our country the description of the species. (Riedl, 1978). Onosma
species, the base leaves are usually star-shaped feathers, Asterotrichia, the base leaves are
simple feathers Haplotricha and basal leaves are both simple and star-shaped feathers are
covered by heteroricha are examined by Riedl in three groups. (Riedl 1978; Koyuncu et. al.,
2013).
Also, Onosma species which are grown as ornamental plants because of their attractivelooking flowers and rich in nectar, contain taxons which are economically important for
beekeeping. (Dukas and Dafni, 1990).
Morphological, micromorphological and anatomical studies on Onosma species have
been extensively observed in our country. In morphological and anatomical studies, body and
leaf anatomy of endemic species were investigated. In micromorphological studies, epidermal
surface and nutlet surface were studied.
In this study, the micromorphological and anatomical structure of six species belonging
to the Onosma species (O. argentata, O. neglectum, O. proballantherum, O. rechingeri, O.
sericea, O. stenoloba) that spread in Bingöl and its environs was investigated for the first time.
The lack of morphological characters used in the identification of Onosma taxons puts the
species into a problematic situation systematically.We hope that the micromorphological and
anatomical characters obtained from the species studied in this study will contribute to the
species taxonomy.
Results and Discussion
The body structure of the investigated species was similar. At the outermost level, the cuticle
layer is 0.6-1.7 µm thick. Under the cuticle, there is a single-row epidermis tissue that consists
of an oval, cubic or rectangular cells. In the epidermis, a small number of coverts and rarely
secretion hairs are seen. Covert hairs are 1-3 cells, upright or slightly curled. The secretory hairs
are composed of a capitate type, a 1-2-cell stem, and a round head. Just below epidermis is the
cortex layer. This layer consists of collenchyma, parenchymal and endodermis layers. At the top
of the cortex layer, there is a 3-6-row collenchyma layer. The collenchyma layer follows two to
five sequential parenchymal cells. O. neglectum and O. parenchymal cells of stenoloba species
contain more intense starch than other species. In the inner part of the cortex, there are one or
two lined endodermis layers. Just below the endodermis, there are three lined phloem layers.
The cambium texture between phloem and Xylem is often indistinguishable. Xylem tissue in the
form of self-correct bundles, along with some regions with phloem is interrupted by the annulus
to the core. The core region consists of parenchymatic cells with thin walls, fragmented, round
or polygonal shape (Figure 4).
The upper and lower epidermis is covered with a thin cuticula in the transverse sections of all
taxons studied. The upper epidermis cells are more significant than the lower epidermis cells.
Epidermis cells consist of single-row, tightly lined, rectangular, square and oval-shaped cells.
The epidermis is densely covered with covertings and rarely secreted feathers. The coverts
surface are tubercled — 1-3 celled, straight or slightly curved shape. Secretory hairs are
rarefied, capitate type. Mesophyll structure differs between species. O. Argentata, O. sericea
and O. rechingeri species of leaves are an equivocal (isobilateral) type. On the other hand, O.
neglectum, O. probellantherum, and O. stenoloba species of leaves, bifacial (dorsiventral) type
(Figure 2). This is one of the most fundamental differences between species in leaf anatomy. In
the median vein zone, there are sizeable collagenous type vascular of all types. Xylem is
directed towards upper epidermis with phloem. At the top of the xylem and below the phloem,
there are several subsequent collenchyma layers. Stomas of all species studied are located in
both upper and lower epidermis of the leaf (amphistomatic) and anomositic type.
The leaves are bifacial; the palisade parenchyma is lined with two lines, plentiful chloroplasts,
cylindrical and tight. The sponge parenchyma is oval or round with 2-4 lines and loose
sequences. In the median vein zone, there is a wide range of collateral type vascular. Xylem is
directed towards upper epidermis, phloem towards lower epidermis. At the top of the xylem, 1-2
lines and 2-4 lines of collenchyma layer are seen below the phloem. Stomas are located in both
upper and lower epidermis in the Leaf (amphistomatic). Also, anomocytic and anisocytic type
are seen less frequently (Figure 14, 15).
Micromorphological studies have shown that the body and leaves of species contain dense
coverts and sparsely secretion hairs. Covert hairs are usually 1-2 cells, straight or slightly
curled. The secretion feathers are less common, consisting of a 1-2-cell stem and a round head
(figure 18). In the diagnosis of Boraginaceae genus members, feathers are of great importance.
Metcalfe and Chalk indicated Boraginaceae as a rough, mostly single-cell but sometimes two or
more-cell conical, calcium salts containing, or shrubby, as the cause of Boraginaceae members '
surfaces and named them Boraginaceae hair. The body and leaf epidermal surfaces of the
onosma species in our study are heavily covered feathers (setae) and rarely secreted feathers.
Tubercled long trichomes on leaves contain beams at the base of some taxons. Unlike other
species, on the leaf surfaces of the O. rechingeri species, there are simple hairs with pointed or
lying ends and setas shorter than simple setas. The base of the setas is swollen and feathered. At
the bottom of some setas, large cells containing cystolith were observed (figure 19). The
indumentum structure in the leaves of the taxons is different. While the indumentum structure of
O. stenoloba was asterotrichous, it was observed that all other species were haplotrichous
(Figure 4).
In comparison to the feathers of secretions and coverts, it is less common. While the leaves were
observed more intensively, they were found to be rarer on the stem. The most excessive
secretion hair, has been seen in the leaves of the O. rechingeri and O. neglecta species. The hair
is made up of a sequence or pear-shaped head cell and a single or two-cell stem cell.
All taxons were examined on leaf epidermal surfaces; stomas were intense. Stomas are an
anomocytic and rarely anisocytic type.
In the studies carried out by Akçin and Binzet 20109, the anatomical structure of the stem and
leaves were investigated. It has been observed that the data obtained have a similar structure
with the Onosma species studied. However, it has been determined that there are differences in
the number of layers of cells and tissues, the density of trichomes and the types of leaf
mesophyll.
The comparative biometric measurements of the taxons studied are given in Table 2. There were
no significant differences in the measurement of the cells and tissues of the taxons.
In Akçin (2007b) and Akçin and Binzet (2011) studies, the epidermal surface of Onosma nuts
was examined in 4 types. Two of these types (reticulate type and rugose type) were obtained in
our studies.