Introduction
Centranthus kellereri
is a Bulgarian endemic plant species, found only in two locations in the world: The Balkans Mountains (Stara Planina), above the town of Vratsa, and The Pirin ...Mountains, above the town of Bansko, Bulgaria. Being endemic and endangered species precluded any significant research on it. The hypothesis of this study was that the populations of
C
.
kellereri
may represent genetically, phytochemically, and morphologically distinct forms and these will differentiate from
C
.
ruber
. Furthermore,
C
.
kellereri
possibly imperfect embryology may preclude its more widespread distribution under natural conditions.
Results
This study revealed the phytochemical profile, antioxidant activity, embryology, surface microstructural morphological traits, and genetic differences between the
C
.
kellereri
plants from the only two natural populations and compares them to the ones of the related and better-known plant
C
.
ruber
. The essential oil (EO) content in aboveground plant parts and in roots was generally low and the EO composition varied significantly as a function of plant part, year of sampling, location, and species. Methylvaleric acid was a major EO constituent in the
C
.
kellereri
EO, ranging between 60.2% and 71.7% of the total EO. The EO included monoterpenes, sequiterpenes, long-chain alkanes and fatty acids. Phytochemical analyses of plant tissue revealed the occurrence of 32 compounds that were tentatively identified as 6 simple phenolics, 18 flavonoids, 1 quinone, 1 lipid, 1 alkaloid, 2 diterpenes, and 3 triterpenes. There were differences in detected compounds between the
C
.
kellereri
plants at the two locations and between the roots and shoots in both species. The total phenols and flavonoids varied between the two species but were also dissimilar between the plants from the two populations of
C
.
kelleri
. Free radical scavenging activity, measured with ABTS and DPPH in aqueous and methanol extracts, had similar values; however, overall,
C
.
kellereri
from Vratsa showed the highest antioxidant activity while
C
.
ruber
had the lowest activity. Genetic analyses showed a clear differentiation between
C
.
kellereri
and
C
.
ruber
, and between the two populations of
C
.
kellereri
. Embryological studies revealed the peculiarities of the male and female generative spheres of the two species that were defined as being sexually reproducing. The pollen had high viability; however, the low viability of seeds demonstrated possible high sensitivity of
C
.
kellereri
to the environmental conditions, perhaps the main factor modifying and restricting the population sizes. The SEM analyses exposed differences in surface microstructural traits between the species (C.
kellereri
and
C
.
ruber
) but also between the two populations of
C
.
kellereri
. The observed dissimilarities in genetic makeup, micromorphological characteristics, and phytochemical composition strongly indicate that the two populations can be classified as distinct subspecies or varieties of
C
.
kellereri
; var.
pirinensis
and var.
balkanensis
. Further research is needed to introduce
C
.
kellereri
into culture and develop it as a high-value specialty crop or ornamental in order to conserve
C
.
kellereri
natural populations.
C
.
kellereri
may be utilized as a source for phytochemicals of interest and as an ornamental plant like
C
.
ruber
; however, it may have a greater environmental plasticity and adaptation as evidenced by its current locations.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Balkans endemic species Alkanna primuliflora Griseb., A. stribrnyi Velen., and A. graeca Boiss. & Spruner have limited distribution in the Balkan Peninsula and a large variation in the ...morphological characteristics. The populations of the three Alkanna species in the Bulgarian flora are small and fragmented. There are no previous reports on the chemical profile or on the embryology of these species. The hypothesis was that the limited distribution of A. primuliflora, A. stribrnyi, and A. graeca was due to their reproductive capacity and genetic diversity. Furthermore, we hypothesized that the three species will contain pyrrolizidine alkaloids (PAs), as other species of the genus Alkanna (Boraginaceae), but they would have differential alkaloids composition. The population genetic structure and differentiation showed a clear distinction between species and revealed average levels of genetic diversity among the natural populations of the three Alkanna species. The embryological investigation observed stability of the processes in the male and female generative spheres and high viability of mature pollen and embryo of the three species. The normal formation of male and female gametophytes without deviations or degenerative processes, and observed levels of genetic diversity between Alkanna individuals are important in maintaining the size and resilience of the Alkanna populations. Eight alkaloids were identified by GC-MS in A. primuliflora and A. graeca and six alkaloids in A. stribrnyi. The main pyrrolizidine alkaloids (PAs) in all investigated species was triangularine. A. primuliflora and A. graeca showed similar chemical composition that comprised 9-angeloylretronecine, 7-tigloylretronecine, 9-tigloylretronecine, triangularicine, dihydroxytriangularine, dihydroxytriangularicine, whereas, in A. stribrnyi 9-tigloylretronecine, triangularicine and dihydroxytriangularicine were not found. This is the first report on the presence of PAs in A. primuliflora, A. stribrnyi and A. graeca. Besides, this is the first report on the embryology of these endemic species. The results contribute to the knowledge of the three endemic Alkanna species and will facilitate policy-making and defining new strategies for their conservation.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Alpine plants are well adapted to environments with extreme conditions – low temperatures, a short growing season, increased air humidity and precipitation, and are therefore of particular interest ...for research. The aim of the present study is to reveal the main reproductive characteristics of two endemic species of the family Campanulaceae, namely Campanula orbelica (Balkan endemic) and Jasione bulgarica (Bulgarian endemic). The main features of the reproductive biology (embryological features, type of reproduction) were established based on the study of micro- and macrosporogenesis and the development of male and female gametophytes. The established features of the reproductive structures and processes characterized C. orbelica and J. bulgarica as sexually reproducing species. Despite the extreme conditions of existence, the studied species presented normal generative progresses leading to the formation of pollen and embryo, which ensures their successful reproduction, populations stability and their distribution in the subalpine environment. In addition, the genome size of C. orbelica was studied by flow cytometry. The estimated genome size varied in the range 1C = 1.34–1.38 pg. No deviation in the ploidy level was found in 22 specimens fresh leaves of which were collected from different parts of the Rila and Pirin Mts.
Compounds accumulated on the surface of plant tissues and structures like glandular trichomes and thin epicuticular layer are defined as exudate, external, superficial. They exhibited important ...protective activities - antifungal, antibacterial, insect antifeedant, larvicidal, antiplasmodial, and UV protective. The exudate obtained from Helichrysum arenarium flowers was evaluated for its inhibitory activity on germination and initial radicle elongation of Lolium perenne seeds. The experiment was done in vitro in Petri dishes. The exudate, in water–acetone mixture (99.5:0.5), was assayed at concentrations of 1, 3, 5, 7, and 10 mg/mL. The chemical composition of the exudate was analyzed by GC/MS. Exudate solution with 5 mg/mL concentration was found to cause more than 90% of seed germination inhibition. At the same concentration, complete inhibition of root growth was observed. The main bioactive component of exudate was identified as flavonoid aglycone–naringenin. The inhibitory activity of H. arenarium on seed germination was investigated for the first time in the present study.
Primula veris (Primulaceae) is a valuable medicinal plant. The main characteristics for assessing the reproductive potential (embryological features; mode of reproduction; pollen and seed viability) ...and the genetic diversity of populations of the species from Bulgaria were studied. The anthers are tetrasporangiate. Their wall development follows the Dicotyledonous-type and consists of: epidermis, a fibrous endothecium, an ephemeral middle layer and a secretory (glandular) tapetum. After meiosis in pollen mother cells and simultaneous microsporogenesis tetrahedral tetrads are formed predominantly in the anthers. Many ovules (approximately 20) develop in the unilocular ovary and are anatropous, tenuinucellate and bitegmic. The embryo sac (ES) develops after Polygonum (monosporic)-type from the chalazal cell of linear megaspore tetrad in the ovule. After double fertilization, a Caryophyllad-type embryo and initially nuclear endosperm form. In the studied populations, high pollen viability of more than 95% was established. Extremely low viability (about 4%) of the seeds obtained from natural populations was established. The results reveal P. veris to be a predominantly amphimictic (sexually reproducing) species, although rare vegetative propagation is also observed. As a result of this study, essential data were obtained about the reproductive structures and processes and for assessing the reproductive potential of P. veris.
is a valuable medicinal plant species with declining populations, protected in Bulgaria by the Biodiversity Act. The present study aimed to increase its extremely low seed germination rate, starting ...with seeds originating from two Bulgarian populations, and to set up an ex situ field collection. The stimulation effect of three factors was tested in in vivo and in vitro experiments: seeds treated with gibberellic acid (in different concentrations and exposure time), light quality (white, infrared, red, and blue or dark), and cold stratification. The combination of factors resulted in 36 treatment variants in vivo and 8 treatment variants in vitro. No germination was observed in control treatment variants. The highest germinating rate (95%) was noticed in vivo under blue monochromatic light after seed soaking into 0.2% GA
for 10 h; however, the best results (55% of well-developed seedlings) were observed with a combination of blue light and 0.3% GA
for 5 h. Seedlings were successfully strengthened in vermiculite in a phytotron, potted in soil and grown in a greenhouse, and then 75 plants were transferred to the field plot, where most of them bloomed at the first vegetation season. These results are intended to serve as a basis for establishing a pilot agriculture of the species.
This study compared the essential oils (EO) composition of
(Bulgarian populations) with that of the cultivated species
. The EO composition of
and
were analyzed via gas chromatography. In general, 75 ...components were identified in
EO and 79 in
EO. The predominant constituents in
EO were
-pinene (34.64-44.35%) and sabinene (10.63-11.1%), which affirmed the examined population as a new chemical type. Overall, the main EO constituents of
originating in France, Bosnia and Corsica were neryl acetate (4.04-14.87%) and
-himachalene (9.9-10.99%). However, the EOs profile of
introduced from the above three countries differed to some extent. D-limonene (5.23%), italicene,
-guaiene and neryl acetate (14.87%) predominated in the
introduced from France, while
-pinene (13.74%), δ-cadinene (5.51%),
-cadinene (3.3%),
-caryophyllene (3.65%) and
-calacorene (1.63%) predominated in plants introduced from Bosnia. The EOs of the plants introduced from France and Corsica had similar chemical composition and antimicrobiological activity.
Glycyrrhiza glabra L. (Fabaceae), commonly known as licorice, is a perennial medicinal plant. Its healing properties are due mainly to the secondary metabolites glycyrrhizin and flavonoids ...accumulated in the roots of plants aged 3 years or more. Overexploitation of licorice populations in Bulgaria led to their rapid decrease. The species is protected by the national Biodiversity Act. The present study aimed at establishing of an ex situ collection of G. glabra using plant material originating from its Bulgarian populations in order to evaluate the main characteristics of the cultivated plants and their potential use as a source of plant material for the creation of a plantation. Plants were obtained from stolon cuttings of donor wild-growing plants from three Bulgarian populations and then cultivated for 3 years in the experimental field plot. Plants originating from all three populations produced glycyrrhizin and flavonoids in similar concentrations under the controlled conditions of the ex situ collection, despite the significant inter-population differences noted in situ. The soil type and supply of soil organic matter, total nitrogen and other nutrients turned out to be most important for the quality of plants in terms of both their growth and biosynthetic capacity. In addition, in vitro micropropagation has proven to be a suitable method for accelerating seedling production. These results would be of practical importance in establishing an agricultural plantation of G. glabra.
The application of natural products for pest control is important in modern farming. In the present study, Artemisia santonicum L. and Artemisia lerchiana Weber essential oil and exudate profiles ...were determined, and their potential as inhibitors of seed germination, acetylcholinesterase, and phytopathogenic mycelium growth were evaluated. Essential oils (EO) were obtained via hydrodistillation and exudates (AE) by washing aerial parts of the species with acetone. EO and AE’s composition was identified using GC/MS. Eucalyptol (1,8-cineole) and camphor were found to be the main components of A. lerchiana EO, while β-pinene, trans-pinocarveol, α-pinene, α-terpineol, and spathulenol were established as major compounds of A. santonicum EO. Strong inhibition on Lolium perenne seed germination was found at 2 µL/mL and 5 mg/mL using aqueous solutions of EO and AE, respectively. An inhibitory effect on acetylcholinesterase was established, with an IC50 value of 64.42 and 14.60 μg/mL for EO and 0.961, >1 mg/mL for the AE of A. lerchiana and A. santonicum, respectively. The low inhibition on the mycelium growth of studied phytopathogenic fungi was established by applying 2 µL of EO and 15 µL of 100 mg/mL of AE, with the exception of A. lerchiana AE against Botrytis cinerea. These results show that the studied EO and AE exhibited strong phytotoxic and AChE inhibitory activities, providing new data for these species.
Essential oils from Monarda fistulosa L., Satureja pilosa Vel., Origanum vulgare subsp. hirtum Ietswaart. (Greek oregano), Micromeria dalmatica Benth., Thymus longedentatus (Degen Urum.) Ronniger, ...and Artemisa campestris L. were evaluated as inhibitors of seed germination in target plants Lolium perenne L. and Trifolium pratense L. using in vitro assays. The essential oils were applied on the seeds as aqueous solutions at concentrations ranging from 0.5–3.0 µL/mL. Complete inhibition was established at a concentration of 1.5 µL/mL with the most effective essential oils. Oregano oil was evaluated for its inhibitory activity on seed germination under field conditions; the essential oil was applied as an aqueous solution at concentrations of 3, 5, and 10 µL/mL on superabsorbent Terawet. The mass obtained was mixed with the seeds of the target plants and planted in a field. After 1 month, the results were evaluated based on the weight of the aerial parts of the plants from control and experimental areas. At the highest concentration studied, the weight of the plants was 77% lower in the experimental areas than in the controls. The chemical composition of the essential oils was analyzed using gas chromatography–mass spectrometry. The results showed that carvacrol-rich essential oils had a strong inhibitory effect on seed germination. The inclusion of the essential oil on a superabsorbent was a good way to preserve its herbicidal activity under field conditions as this prevented its rapid evaporation.
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