Kotschyanus Boiss Research Articles

Assessment of some parameters of the chemical composition of Thymus kotschyanus Boiss. Growing in different ecological zones of the Republic of Armenia

Background: Thymus kotschyanus Boiss., commonly known as thyme, is a small semi-shrub valued for its aromatic and medicinal properties. Found throughout the Middle East and the Caucasus, it adapts to various ecological conditions and is rich in biologically active compounds, including essential oils, flavonoids, and phenolic acids. Its diverse chemical profile has made it a focus of pharmacological research for its antimicrobial, antioxidant, and anti-inflammatory effects, highlighting its potential therapeutic applications. Objective: The study aimed to investigate the bioactive compounds in wild T. kotschyanus Boiss. plants grown under diverse ecological conditions, with an emphasis on how these compounds change in response to varying environmental contexts. Materials and Methods: The chemical composition of Thymus kotschyanus Boiss. was investigated during its flowering phenophase. Aerial parts of plants were collected from the Tavush (40°880518N, 45°427958E) and Kotayk (40°17’56"N, 44°33’15"E) regions in Armenia between 2021 and 2023. The study focused on analyzing ash and moisture content, phytochemical screening, and mineral content. Results: The ethanolic extracts of Thymus kotschyanus Boiss from both regions contained a diverse array of bioactive compounds, including coumarins, flavonoids, alkaloids, tannins, phenols, carbohydrates, proteins, and saponins. Plants from the Tavush region exhibited a moisture content 1.83% higher than those from the Kotayk region, reflecting a 36.1% increase. Similarly, the ash content was 1.3% higher in Tavush plants, resulting in a 17.1% increase compared to Kotayk plants. Analysis of macro- and microminerals revealed that potassium was the most abundant macromineral, followed by calcium, magnesium, phosphorus, and sodium. Among the microminerals, iron had the highest concentration, followed by zinc and copper. Conclusion: The study demonstrated significant differences in the biologically active compounds, mineral composition, moisture, and ash content of T. kotschyanus Boiss. from different ecological zones in Armenia. Plants from the Tavush region exhibited higher moisture and ash content, as well as elevated levels of vitamins A and C, phenolic content, and essential minerals such as calcium, magnesium, sodium, potassium, and phosphorus, compared to those from the Kotayk region. These findings underscore the impact of environmental conditions on the quality and composition of T. kotschyanus Boiss., highlighting its potential as a valuable source of biologically active compounds and essential minerals. Keywords: aromatic plants, bioactive compounds, essential minerals, wild thyme, T. kotschyanus Boiss

Mountain-Xerophytic Vegetation Type Found in Daridag

Information about the mountain-xerophytic type of vegetation of the Daridag area is presented. Areas at an altitude of 1200-1600 m above sea level are characterized by plant species with mountain xerophytic vegetation. Mountain xerophytic flora is not homogeneous and represents a set of individual phytocenosis. Ephemeral plants play an important role in this vegetation. In addition to ephemerals, the vegetation includes bulbous, tuberous, and various grasses, mainly: Rhamnus pallasii Fisch. & C. A. Mey., Astragalus microcephalus Willd., Astragalus beckerianus Trautv., Astragalus aduncus Willd., Thymus kotschyanus Boiss. & Hohen., T. collinus M. Bieb.,Euphorbia seguieriana Neck., Caragana grandiflora (M. Bieb.) DC., Atraphaxis spinosa L., Acanthophyllum mucronatum C. A. Mey., Zygophyllum atriplicoides Fisch. & C. A. Mey., Z. fabago L., Acantholimon araxanum Bunge etc. In total, the study identified 6 groups of formations and 16 associations. These include thorn shrubs, monodominant tragacanth xerophytic shrubs, cushion xerophytic shrubs, subshrub phrygana and mixed shrubs, which are included in the mountain xerophytic vegetation type. The phytocenosis of mixed herbaceous shrubs is comprised of 35 species, of which 10 species are shrubs (28.56%), 1 species is a semi-shrub (2.86%), 1 species is a shrub (2.86%), 2 species are semi-shrubs (5.72%), and 21 species are perennial and biennial (60%) plants. With regard to their life forms, of the 21 species included in the monodominant tragacanth xerophytic shrub grouping, three species are shrub-like, two species are shrubs, two species are semi-shrubs, and 14 species are perennial grasses.

Effectiveness of the Study of Plant-Contaınıng Immunostımulants in Poultry Industry

The effect of the plant-derived preparation (Tilia cordata Mill., Thymus kotschyanus Boiss and Hohen., Matricaria chamomilla L.) Imuneo on the immunity indices in chickens vaccinated against avian infectious bronchitis was studied, and the immunostimulatory efficacy was evaluated. In the group of chickens treated with immunostimulants, a significant increase in their immune status was recorded. The immunostimulating effect of Imuneon was determined. Microbicidal and immunostimulating properties of plant-derived Hedalin preparation were studied. The expediency of using immunostimulating drugs in poultry complexes is presented.

Influence of Ag nanoparticles on physiological and biochemical aspects of callus of Thymus species and Zataria multiflora Boiss.

Thymus species have found remarkable importance in food and medicine industries. The present study investigates the potential effect of Ag nanoparticle elicitors on proliferation of callus, and production of carvacrol and thymol in Zataria multiflora and three Thymus species. Firstly, callus was induced on Murashige and Skoog (MS) medium containing 2 mg l−1 of 2, 4-dichlorophenoxy acetic acid (2,4-D) and 1 mg l−1 of kinetin (Kin)). Secondly, the effects of two different concentrations of Ag nanoparticles (4 and 8 mg l-1) were studied on callus growth and its secondary metabolites production. Results elucidated that after elicitation by 8 mg l-1 ofAg NPs, significantly the highest callus growth rate (CGR) (0.02 mm day-1), callus fresh mass (CFM) (0.99 g), and carvacrol (0.68 mg l-1) and thymol (11.09 mg l-1) content was achieved. Comparing different Thymus species, notably the greatest carvacrol and thymol amount was obtained in .kotschyanus Boiss. & Hohen. and T. Daenesis Čelak. at 8 mg l-1 concentration ofAg NPs. Hence, it is evident that the stimulation by NPs is dose-dependent. This study has potential to be commercially applied for the enhancement of pharmaceutical compounds in different species of Thymus.

Effect of Essential Oils and Hydrosols from Some Selected Lamiaceae Species on Redroot Pigweed (Amaranthus retroflexus L.)

Allelopathy refers to chemical effect of a plant direct or indirect on germination, growth or development of neighboring plants. Allelopathy can be considered as a component of biological control that reduces the development of other plants. This study was carried out to determine the effect of Greek sage (Salvia fruticosa Miller), basil (Ocimum basilicum L.), Dragonhead (Dracocephalum moldavica L.), spearmint (Menta spicata L.), sage (Salvia officinalis L.), lemon balm (Melissa officinalis L.), oregano (Origanum onites L.) and thyme (Thymus kotschyanus Boiss.) on the germination of redroot pigweed (Amaranthus retroflexus L.) which causes significant yield loss in agricultural production. Essential oil (9, 18, 36 µL/petri) and hydrosols (50, 75, 100%) of aromatic plants were applied to determine their inhibition effects on seed germination of A. retroflexus. The experimental design for in vitro was a randomized design with five replications. It has been shown that germination rate was decreasing by the increased concentration of essential oil and hydrosols of the tested plant species. Also, total germination inhibition of A. retroflexus depended on the essential oil doses; the rate ranged from-2.9 to 85%. Amongst the essential oils, the highest effect was observed in spearmint with 7% germination rate. It could be considered as an important solution, which would contribute in Integrated Weed Management of A. retroflexus by using different concentrations of essential oil and hydrosols from aromatic plants.

Application of modeling techniques for the identification the relationship between environmental factors and plant species in rangelands of Iran

The objective of the present research was to compare Ecological Niche Factor Analysis (ENFA) and Artificial Neural Networks (ANN) to determine the optimum threshold of plant species (Thymus kotschyanus Boiss and Hohen. and Dactylis glomerata L.) in rangelands of Ardabil province. Systematic random sampling of vegetation was performed, and an overall 111 sites were considered and divided into two groups, namely sites with plant species and sites without plant species. Five plots of one square meter were placed in each site. The size of the plots was based on the magnitude of one or double the average area of the most common plant species. Plots were positioned along a 40-m transect (from the bottom of the slope to high altitudes with a distance of 10 m between the plots). Soil sampling was done in a depth of 0–30 cm (selected based on the activity of root plant species). Maps of environmental factors were prepared in ArcGIS 10.4.1 software. The sensitivity and specificity were considered to specify the optimum threshold. The optimal threshold between plant species, determined by modeling methods, showed that the highest accuracy belonged to ENFA model in T. kotschyanus habitat (with optimum threshold = 0.62 and sensitivity = 0.58) and ANN model in D. glomerata habitat (with optimum threshold = 0.37 and sensitivity = 0.02) had the lowest accuracy.

Lectotypification of Some Names in Dianthus L. (Caryophyllaceae)

In this study, lectotypifications of 21 valid or synonym names of the genus Dianthus L. (Caryophyllaceae) were determined. Among these; the types of D. acrochlorus Stapf, D. haussknechtii Boiss., D. hypochlorus Boiss. & Heldr., D. kastembeluensis Freyn & Sint., D. kotschyanus Boiss. & Heldr., D. lydus Boiss., D. micranthus Boiss. & Heldr., D. multipunctatus Ser. var. gracilior Boiss., D. pallens Sibth. & Sm. var. oxylepis Boiss. and D. striatellus Fenzl were based upon the specimens collected from two or more localities. The types of D. bitlisianus Kotschy ex Boiss., D. brevicaulis Fenzl, D. carmelitarum Reut. ex Boiss., D. cibrarius Clem., D. hymenolepis Boiss., D. muschianus Kotschy ex Boiss., D. polycladus Boiss. and D. setisquameus Hausskn. ex Bornm. were based upon the specimens collected from a single locality without mentioning any “type”. And D. arpadianus Ade & Bornm. var. trojanus Bornm. & Sint., D. engleri Hausskn. & Bornm. and D. siphonocalyx Blakelock were based upon the specimens for which multiple “types” were stated. Most of the specimens of the lectotypes determined in this study were collected from Turkey and the rest came from Syria and Iraq.

Investigating the effect of water stress on yield, essential oil content and physiological characteristics of Thymbra spicata L.

هدف انجام این آزمایش بررسی تغییرات عملکرد بوته، اسانس و برخی ویژگی­های فیزیولوژیک برگ دو اکوتیپ گیاه داروئی زوفایی به اعمال تنش رطوبتی بود. آزمایش در قالب طرح کرت­های خرد­شده بر پایه بلوک­های کامل تصادفی در سه تکرار و در دو سال (1395 و 1396) در مزرعه تحقیقاتی دانشگاه ایلام انجام گرفت. کرت­های اصلی شامل سه سطح تنش رطوبتی (آبیاری نرمال، تنش ملایم و تنش شدید) و کرت­های فرعی دربرگیرنده فاکتور فرعی شامل دو اکوتیپ گیاه زوفایی بود. نتایج آزمایش نشان داد که سطوح مختلف تیمارهای تنش رطوبتی بر صفات موردبررسی ازجمله عملکرد خشک برگ و بوته، درصد و عملکرد اسانس، شاخص سطح برگ، ارتفاع بوته و رنگیزه­ های فتوسنتزی تأثیر معنی­داری داشت. به‌طوری‌که افزایش فاصله آبیاری از آبیاری نرمال تا تنش شدید سبب کاهش معنی­دار تمامی صفات مذکور شد. بیشترین عملکرد خشک برگ، بوته، شاخص سطح برگ و کلروفیل a در تیمار آبیاری نرمال و بیشترین میزان درصد و عملکرد اسانس، کلروفیل b، کلروفیل کل و کاروتنوئید در تیمار تنش ملایم حاصل گردید. با توجه به یافته­های آزمایش اکوتیپ ملکشاهی ازنظر عملکرد خشک برگ و بوته، درصد و عملکرد اسانس نسبت به اکوتیپ سومار برتری داشت. نتیجه بررسی دوساله آزمایش نشان داد که طی سال دوم به دلیل افزایش ارتفاع و شاخص سطح برگ بوته­ ها، میانگین صفاتی از قبیل عملکرد خشک برگ و بوته و عملکرد اسانس 1.7 درصد نسبت به سال اول آزمایش افزایش نشان داد. ازآنجاکه دو اکوتیپ مورد آزمایش در طبیعت به‌صورت خودرو بوده و با شرایط اقلیمی ناپایدار و نامنظم بارشی سازگاری یافته­اند، بنابراین اعمال آبیاری منظم در کشت آن‌ها به‌صورت زراعی در مقایسه با ایجاد محدودیت آبی ملایم موجب پاسخ منفی این گیاه ازنظر درصد و عملکرد اسانس و سایر خصوصیات رشدی می­گردد که در مدیریت زراعی آن باید در نظر گرفته شود.

Determination and analysis of volatile components from Thymus kotschyanus Boiss with a new solid-phase microextraction fibre and microwave-assisted hydrodistillation by periodic mesoporous organosilica based on alkylimidazolium ionic liquid.

Research on the volatile oil composition of Thymus kotschyanus Boiss was conducted by applying mesoporous organosilica based on alkylimidazolium ionic liquid (PMO-IL) as a fibre coating material via a method referred to as microwave-assisted headspace solid-phase microextraction (MA-HS-SPME). This technique entails microwave irradiation of the sample and collection of the volatile sample components. These components are further introduced into a gas chromatography-mass spectrometry (GC-MS) injection port for further analysis. A simplex method was used for the optimisation of three different parameters affecting the efficiency of the extraction. The MA-HS-SPME method proved to be the most suitable technique in oil determination and extraction from Thymus kotschyanus owing to its advantageous aspects of cost effectiveness, simplicity and solvent independence.

Variations in Chemical Composition and Bioactive Compounds of Thymus kotschyanus Boiss. & Hohen Populations Originated from Different Collection Sites

Variations in essential oil yield and oil composition of Thymus kotschyanus Boiss. & Hohen populations originating in different locations across Iran were evaluated using hydrodistillation and GC/MS analysis. The aerial parts of the plants varied in their essential oil yields from 1 to 1.41% across the populations. Under optimum distillation and analysis conditions, thirty-eight constituents accounting for about 88.7-99.9 % of the total components were identified with thymol (6.8-66.15%), carvacrol (2.38-20.06%), linalool (1.39-22.23%), α-terpineol (0.16-11.64%), and geraniol (0.36-11.37%) as the major compounds. Plant samples were also analyzed for their flavonoid and total phenolic contents. Results indicated that total phenolic content of the essential oil from T. kotschyanus Boiss. & Hohen populations ranged from 25.04 to 60.25 mg TAE g-1 DM while total flavonoid content ranged from 2.11 to 8.14 mg QE g-1 DM. Antioxidant activity was assessed by the two complementary analytical approaches of DPPH free-radical scavenging and reducing power systems to discover that both methods revealed comparable antioxidant activities in the extracts, with the highest values belonging to populations 1 (IC50:256.6 μg mL-1) and 5 (IC50:259 μg mL-1). The populations with high thymol contents and antioxidant activities will promise beneficial as supplements in functional food ingredients and pharmaceutical products.

Leaf fatty acid composition of some Lamiaceae taxa from Turkey

Fatty acids composition leaves of Satureja hortensis L., Satureja boissieri Hausskn ex Boiss., Thymus kotschyanus Boiss.& Hohen. var. glabrescens Boiss., Thymus kotschyanus Boiss. & Hohen. var. kotschyanus, Thymus hausknechtii Velen., Thymus pubescens Boiss. & Kotschy ex Celak var. pubescens, Thymus fallax Fisch & Mey, Origanum vulgare L. subsp. gracile and Origanum acutidens L., were analyzed by gas chromatography. The fatty acid composition of plants used to this study showed different saturated and unsaturated fatty acid concentrations. The main fatty acids found were Palmitic acid methyl ester (13.49-27.71%), Linoleic acid methyl ester (10.85-19.47%), and Linolenic acid methyl ester (40.68-56.53%); while other fatty acids were found in minor proportions. As a result, all taxa had the highest total unsaturated fatty acid amounts (39.05-73.19%) and the lowest total saturated fatty acid amounts (19.43-51.12%). The highest unsaturated fatty acid determined to Satureja hortensis (73.19%), the lowest to Thymus hausknechtii (39.05%). In this study, palmitic acid methyl ester was found the major saturated fatty acids in all studied taxa.

Essential oil composition of two Thymus kotschyanus Boiss. varietes from Elazığ (Turkey)

In this study aerial parts essential oil of T. kotschyanus Boiss. & Hohen. var. kotschyanus and T. kotschyanus Boiss. & Hohen. var. glabrescens Boiss. were analyzed by HS-SPME/GC-MS. As a result forty one and thirty nine components were identified representing 90.4% and 89.3% of the oil, respectively. Thymol (31.2%), carvacrol (19.5%), p-cymene (11.2%) and γ-terpinene (8.4%) were detected the main compounds of T. kotschyanus var. kotschyanus; thymol (26.3%), carvacrol (24.3%) and p-cymene (17.6%) were detected the major constituents of T. kotschyanus var. glabrescens. With this study, chemotypes of studied taxa were detected carvacrol and thymol. In addition studied plant samples were found to be rich in respect to essential oils and the results discussed natural product, renewable resources and chemotaxonomy.

Identification of volatile components in two Thymus species from Iran and their antioxidant properties

Thymus species are well known to have significant amount of phenolic compounds and exhibit strong antioxidant activities. This study is designed to analyze the essential oils of two Iranian Thymus species, ( T. kotschyanus Boiss. et Hohen and T. pubescense Boiss. et Kotschy ex Celak) obtained by hydrodistillation of aerial part of this plants, using GC-FID and GC/MS and evaluate the in-vitro antioxidant activities in two quantitative methods (namely DPPH. and ABTS.+ assay) to determine the total phenolic content of the species (assayed by colorimetric techniques) and to study the possible compositionantioxidant activity relationship. The major aroma constitutes in the essential oil of T. pubescense were found to be thymol (38.7 %), γ-terpinene (7.5 %), p-cymene (5.5 %), α-terpenyl acetate (3.8 %) and β-bisabolene (3.7 %) while in the essential oil of T. kotschyanus, α-terpineol (16.9 %), 1,8-cineol (14.4 %), linalool (9.6 %), thymol (7.2 %) and geranyl acetate (5.4 %) were the main compounds. Both of the tested essential oils exhibited concentration-dependent antioxidant activity. T. pubescense showed more activity in both DPPH. [IC50= 285.2 (236.5-344.0) μg/mL] and ABTS.+ methods [IC50= 1.956 (1.810-2.113) μg/mL], as well as total phenolic content of T. pubescence [70254 ± 0.0049 μg/mg] was found to be slightly higher than T. kotschyanus [62933 ± 0.0026 μg/mg].

Antioxidant and antibacterial activity of flavonoid-, polyphenol- and anthocyanin-rich extracts from Thymus kotschyanus boiss & hohen aerial parts.

The total phenolic and flavonoid contents, antioxidant and antibacterial properties of flavonoid- (water, ethyl acetate and hexane fractions), polyphenol- and anthocyanin-rich extracts of Thymus kotschyanus aerial parts were investigated. All the extracts showed significant amounts of phenolic and flavonoid compounds and exhibited strong antioxidant activity. Among the extracts, water fraction contained the highest phenolic and flavonoid contents (881.06 ± 16.52mg GAE/g of extract and 74.60 ± 3.05mg QE/g of extract, respectively). It also presented the highest DPPH(•) scavenging activity with an IC50 of 14.21 ± 0.53μgmL(-1), and the highest reducing power at 400μgmL(-1) by A700 = 2.46 ± 0.04. The extracts were found to exert moderate antibacterial activity against both Gram-negative and Gram-positive bacteria. These findings highlighted a scientific basis to the traditional usage of T. kotschyanus, also showed its potential as a rich source of natural antioxidant and antibacterial compounds.

Morpho-physiological variation and essential oil content of Iranian populations in Thymus kotschyanus Boiss. & Hohen grown under similar condition

Thymus kotschyanus Boiss. & Hohen is one of the medicinal herbs native of Iran. According to the economic importance of thyme, identify of morphological characteristics and essential oil content is important in different populations. We studied the pattern of variation of 33 morphological and physiological characteristics of T. kotschyanus in 15 Iranian populations experimentally grown under similar conditions. The results showed that in important traits, the highest mean of flowering stem length was related to Zanjan-I population, the most number of shoots pre plant was in Azarbayejangharbi-IV population, the highest leaf’s length and width respectively, belonged to Tehran and Lorestan population, the highest plant height was in Zanjan-I population, the most fresh and dry weight was related to Azarbayejangharbi-II population and the longest inflorescence was observed in Qazvin-II population. Cluster analysis of quantitative traits divided three main groups in thymus populations and Azarbayejangharbi populations were separated partially. Based on the qualitative traits, populations were classified in five main groups. As such, Zanjan and Qazvin populations were in separate groups. The results showed that the most content of essential oil and the highest mean of the most morphological traits were belonged to Azarbayejangharbi-I, IV and Tehran populations. Therefore, the morphophysiological characteristics of medicinal plants have many effects on essential oil’s content. Thus, the planting of diverse population in the equal environmental conditions will reduce the environmental impacts on incidence of vegetative traits, also better reveals the diversity of genetical differences between populations.

Chemical Composition and Antimicrobial and Antioxidant Activities of three Turkish Thyme Essential Oils

The aim of present study was to compare the antioxidant and antimicrobial activities of three Thymus kotschyanus varieties on the basis of the chemical compositions of oils obtained by hydrodistillation. GC-MS analysis of the isolated essential oils from aerial parts of Thymus kotschyanus Boiss. & Hohen. var. eriophorus (Ronniger) Jalas, Thymus kotschyanus Boiss. & Hohen. var. kotschyanus and Thymus kotschyanus Boiss. & Hohen. var. glabrascens resulted in the identification of 55,, 34 and 57 constituents, respectively. The major components in the essential oils of T. kotschyanus Boiss. & Hohen. var. eriophorus (Ronniger) Jalas and T. kotschyanus Boiss. & Hohen. var. kotschyanus were described as geraniol (55.0–59.1 %) and geranyl acetate (27.1–28.8 %). The oil of T. kotschyanus Boiss. & Hohen. var. glabrascens is characterized by the high monoterpene fraction (86.5 %) and especially by the presence of carvacrol (57.2 %) and its precursor p-cymene (11.0 %). The essential oils were studied in vitro for antimicrobial activity (as inhibition zone and MIC) against fourteen bacteria strains using agar disc diffusion and broth micro-dilution methods. The oils exhibited moderate zone of inhibitions against bacteria when compared to standard antibiotics ketoconazol and chloramphenicol used as controls. The samples were subjected to a screening for their possible antioxidant activities by using 2,2-diphenyl-1-picrylhydrazyl (DPPH). When compared with the antioxidative potentials of the standard compound used in this study (BHA), essential oils of the T. kotschyanus varieties studied exerted remarkable antioxidant activity.

An ethnobotanical survey of some medicinal plants in Keban (Elazığ -Turkey).

In this study, 61 wild plant taxa belonging to 30 families that are used as medicine are documented in Keban (Elazog). The most encountered medicinal plant families were Lamiaceae (10 taxa), Asteraceae (8 taxa), Fabaceae (6 taxa) and Rosaceae (5 taxa), the most common preparations were infusion and decoction. These folk medicinal plants are mostly used for treatment of kidney stones, colds and flu, analgesic, cough, for skin and diabetes diseases. Mentha longifolia (L.) Huds. subsp. typhoides (Briq.) Harley var. typhoides , Salvia syriaca L., Rosa canina L., Thymus kotschyanus Boiss. & Hohen. var. kotschyanus , Portulaca oleracea L. and Rumex acetosella L. were the plants most used by the local people in Keban, Turkey.

Essential Oil Compositions of Thymus kotschyanus Boiss. Obtained by Hydrodistillation and Microwave Oven Distillation

The essential oils of the aerial parts of Thymus kotschyanus Boiss. obtained by hydrodistillation (HD) and microwave oven distillation (MD) were analyzed by GC and GC-MS. 39 components were identified in the essential oil of this plant (95.0 % in HD and 94.8 % in MD). The components of the essential oil extracted by MD were similar to those obtained by HD. T. kotschyanus essential oil was characterized by a high amount of carvacrol (64.6 % in HD and 44.7 % in MD). Other major compounds were identified as p-cymene, γ-terpinene and L-Borneol. Thymoquinone was absent in HD method. Although the time of MD was 12 times less than HD, but the percentage of essential oil was only 15 % less (1.2 % in MD and 1.4 % in HD). Moreover, the amount of carvacrol as the main component of the plant essential oil, in MD was 20 % less than HD.

Life form and preference can drive spatial relationships among plant species in semi-arid rangelands of middle Iran

The interaction among species is one of the most important factors influencing the distribution of plants in a given habitat. Vegetation of arid rangelands often appears patchy with many herbaceous species associated with shrub species. It was hypothesised that plant interactions among different life forms together with the effect of grazing preference generate this type of spatial distribution of plant species in the semi-arid rangelands of middle Iran. Spatial patterns and associations were quantitatively analysed using Hopkins’ index and Chi-square tests to establish links between spatial relationships, plant life forms and preference by grazers on the south foothills of the Taleghan ranges, Alborz Province. Data were collected from three geographical sites with different dominant species and clumped patterns of plant spatial distributions for these species were detected. These spatial patterns were probably generated by the interplay of life form-dependent facilitative interactions among plants and the grazing pressure on preferred species rather than due to their intrinsic characters. In the study sites, grass species were significantly more frequently observed in the vicinity of nurse species than in open areas. It was also found that plant-plant interactions may change in response to changes in environmental conditions, such as soil characters and the benefits achieved by the beneficiary species from being associated with nurse species. All preferred perennial species were spatially associated with shrub species (Astragalus gossypinus Fischer and Thymus kotschyanus Boiss & Hohen), while nurse species that just physically protect the beneficiary species from grazing (e.g. A. gossypinus) did not associate with non-preferred species (e.g. Stipa barbata Desf). Instead, these non-preferred species may positively aggregate with nurse plants showing other beneficial characteristics such as nitrogen fixation and improvement of soil conditions.

Evaluation effect of microwave irradiation on the amount of volatile compounds, monoterpenes and sesquiterpenoids from Thymus kotschyanus Boiss with four methods

This article investigates the effect of microwaves on the amount of volatile compounds from Thymus kotschyanus Boiss with four methods, headspace single-drop microextraction, microwave-assisted headspace single-drop microextraction, microwave distillation extraction and hydrodistillation, for the analysis of essential oil. Solvent selection, solvent volume, microwave power, irradiation time and sample mass were optimised by simplex method.