Peppermint Plants Research Articles

Advancements in steam distillation system for oil extraction from peppermint leaves

The numerous advancements conducted experimentally to improve the efficiency of steam desalination systems to extract the essential oil from the peppermint plant are presented in this article. Peppermint oil is important for human life because of its health benefits. It is used in the medical sector and food industry as an herb and fragrance, respectively. In this study, two types of distillation systems, namely the solar distillation system and the electrical energy-based distillation system, are discussed. The major factors that lead to increased system efficiency, such as the mass flow rate of heat transfer fluid, inlet water flow rate to boiler and batch size of peppermint, are addressed.

Microencapsulation of lambda-cyhalothrin with polyurethane-urea and application on peppermint plant leaves containing a two-spotted red spider mite (tetranychus urticae)

In this study, lambda-cyhalothrin (LC) used as a pesticide was microencapsulated with polyurethaneurea (PUU) at 55°C temperature for 180 min. Wall thickness and dimensions of the microcapsules, the effect of mixing speed on the capsule size, active substance release times of LC-PUU microencapsules under UV rays and alcohol/water medium, microencapsulation yields and the effect of microencapsulated active substance on the red spider on peppermint plant leaves (mentha piperita) were investigated. The microcapsule yield was found 77.4–85.5%, also capsule shell thickness was 512.3–724.5 nm. The highest release percentage of the microcapsules was found to be 35.00% at 20°C for 4 h under UV light. When the LC-PUU microcapsules applied to the peppermint plant leaves (mentha piperita) which contained a two-spotted red spider mites (tetranychus urticae), it remained active for 8 weeks and during this period no insect formation was observed on the peppermint leaves.

A simple method to determine antioxidant status in aromatic plants subjected to drought stress.

Drought is a major environmental stress factor that affects the growth and development of plants. All plants have to maintain the reactive oxygen species within certain levels for normal cellular homeostasis by means of their antioxidant systems, which can be classified as enzymatic and non-enzymatic. Plants under drought stress generate an excess production of reactive oxygen species. At high concentrations, this can be detrimental by producing damage to the protein structures and inhibiting enzymes, as well as oxidizing macromolecules, which may eventually lead to cell death. There has been increasing attention paid to the antioxidant capacity of aromatic/medicinal plants, with a high antioxidant content having been reported in some plant extracts, such as in Mentha piperita (peppermint). Peppermint plants cultivated under drought stress also present high levels of phenolic compounds, peroxidase enzyme activity and lipid peroxidation of membranes. A simple and inexpensive laboratory class is proposed for teaching some mechanisms that plants have evolved to avoid reactive oxygen species damage. The series of lab experiments described is aimed at demonstrating the antioxidant status in aromatic plants subjected to drought stress, by measuring total phenolic compound content (non-enzymatic antioxidant compound), peroxidase activity (enzymatic antioxidant) and malondialdehyde, as convenient biomarkers for lipid peroxidation. The proposed class will be carried out by undergraduate students of the advanced biochemistry course, as part of our biology and agronomy studies. The experiment presented is intended to be used as a vehicle to emphasize the concepts that students have learned in their lectures. This lab exercise to be carried out by the students has dual goals: to apply a methodology only learned superficially on previous courses, and also to increase their understanding of how plants developed resistance mechanisms in order to tolerate drought stress.

Infestation of Field Dodder (Cuscuta campestris Yunck.) Promotes Changes in Host Dry Weight and Essential Oil Production in Two Aromatic Plants, Peppermint and Chamomile.

Peppermint (Mentha piperita L.) and chamomile (Chamomilla recutita (L.) Rausch.) are aromatic plants with considerable economic value. These plants and their essential oils are used in medicine, cosmetics, and the food industry. One of the main limiting factors in peppermint and chamomile commercial cultivation is weed competition since weeds are able to decrease both oil amount and biomass yield. The purpose of the present study was to determine the effect of parasitism by field dodder (Cuscuta campestris Yunck.) on peppermint and chamomile dry weight and their essential oil yield and composition. Essential oils from both noninfested and infested peppermint and chamomile plants were obtained by hydrodistillation and characterized chemically by gas chromatography (GC) coupled with mass spectrometry (MS). The amount of dry matter accumulated by peppermint and chamomile plants infested by field dodder was lower (25% and 63%, respectively) compared to noninfested plants. Essential oil yield increased for peppermint (3.87% (v/w) and 3.63% (v/w)), but decreased for chamomile (0.2% (v/w) and 0.5% (v/w)) both from infested and noninfested plants, respectively. The oil composition profile significantly differed in terms of content. In peppermint plants, field dodder infestation increased menthone content by 23%, and decreased the content of both menthol by 11% and pulegone by 67%. Furthermore, δ-cadinene was detected only in oil extracted from infested peppermint plants. Compared to peppermint, chamomile plants were significantly more affected by field dodder in terms of essential oil yield, as well as oil composition and plant dry weight. In chamomile plants, (E)-dendrolasin was detected in the oil of noninfested plants, and 1,4-dimethyl-7-(1-methylethyl)-azulen-2-ol was detected only in the oil of infested plants.

Menthol, Balance of Menthol/Menthone, and Essential Oil Contents of Mentha × Piperita L. under Foliar-Applied Chitosan and Inoculation of Arbuscular Mycorrhizal Fungi

Mentha × Piperita L. or peppermint belonging to the family Lamiaceae (mint) is an important herb and useful in pharmaceutical, medicinal and cosmetic industries. In this study, the interactive effects of the foliar application of chitosan and inoculation of the rhizomes of peppermint seedlings with arbuscular mycorrhizal fungi (AMF) on growth and of the contents of menthol and balance of menthol/menthone of the essential oil from M × Piperita in a randomized complete block design (RCBD) were evaluated. The essential oil from the aerial parts (stem and leaves) of this herb was analyzed by GC-FID and GC/MS. Results indicated that the experimental treatments especially the inoculation of the peppermint plants with AMF influenced fresh and dry herbal weights and dry matter of the herb. The major constituents of the essential oil of M × Piperita were menthol and menthone belonging to oxygenated monoterpenes. The highest contents of essential oil yield, menthol and balance of menthol/menthone of the essential oil from M × Piperita were obtained from the peppermint plants under foliar spraying of chitosan and inoculation with AMF, however, the herbs under the foliar application of chitosan (both concentrations) without inoculation showed the highest percentages of menthone and limonene. The results indicated that elicitation of the peppermint with chitosan and inoculation of the peppermint plants with AMF has positive effects on dry herbal weight and secondary metabolites and can be improved the quantity and quality active substances of M × Piperita L.

Impact of Soil Rhizobacteria Inoculation and Leaf-Chewing Insect Herbivory on Mentha piperita Leaf Secondary Metabolites.

Secondary metabolites commonly play important physiological roles in plants and can be modified quantitatively and qualitatively by exposure to biotic and abiotic interactions. Plant growth promoting rhizobacteria (PGPR) and herbivory induce systemic resistance. In the present study, we analyzed the induction of secondary metabolites in peppermint plants in response to chewing insect herbivory on PGPR-inoculated Mentha piperita plants. The secondary metabolites of M. piperita plants were increased when plants were inoculated with PGPR and also exposed to caterpillar herbivory. It was found that the total essential oil yield in inoculated plants with insect damage was ~2.6-fold higher than in controls. The yield was similar to that of plants either damaged by insects or inoculated, indicating that there was no synergism. The same trend was observed for phenolic compounds. In contrast, VOC emissions were significantly higher in plants infested by insects, independent of whether they were inoculated. Insect damaged plants had 5.5 times higher monoterpene emissions than control plants, and ~ 2-fold higher emissions than on PGPR-inoculated plants without insects. To gain a better understanding of how herbivory on PGPR-inoculated plants can cause an increase in secondary metabolites of peppermint, we examined changes in plant defense hormones in inoculated plants after herbivory. We found that the combination of both treatments increased the endogenous jasmonic and salicylic acid levels to the same extent as in plants only inoculated or only insect-damaged. Because different interactions can alter the phytochemistry of plants such as M. piperita, this topic is both ecologically and economically relevant.

Salicylic acid effects on some physiochemical properties and secondary metabolite accumulation in Mentha piperita L. under water deficit stress

Salicylic acid (SA) play important roles in different physiological processes of plants such as plant growth, stress response, plant adaptation and secondary metabolite accumulation. This study was conducted to evaluate the effect of exogenous SA applications on the growthmeasurements such as fresh and dry weight of aerial part and lead dry weight, biochemical properties (membrane permeability, lipid peroxidation, Proline content and ROS scavenger enzymes) and secondary metabolite accumulation(total phenolic and the flavonoid and essential oil content) in peppermint (Mentha piperita L.) plants grown at different levels of water deficit stress (Field capacity: FC). For this aim, three different water deficit stress (no stress (100% FC), mild stress (75% FC) and moderate stress (50% FC)) and four different SA concentrations (0, 1, 2 and 2.5 mM) were applied to peppermint plants. Results showed that all of the measured parameters were affected by the water deficit stress and SA application. By elevating the level of water deficit stress, fresh and dry weights of aerial parts and dry leaf weight decreased. Increasing in the water deficit stress level from mild to moderate stress resulted to reduce the essential oil content while proline, lipid peroxidation, total phenolic contents, flavonoid content, and antioxidant enzyme activities increased depending on water deficit stress. Exogenous application of SA obstructed the negative effects of water deficit stress by decreasing the lipid peroxidation and membrane permeability and improving the antioxidant enzymes activities. Essential oil content increased significantly in plant treated with SA grown under water deficit stress conditions. Application of 2 or 2.5 mM of SA enhanced the plant growth and development without any toxic effects and increased significantly the total phenolic content, dry leaf weight, and the essential oil content in stressed and even in control (100% FC) peppermint plants.

Effect of powdered extract of peppermint (Mentha piperita) on adult cowpea bruchid (Callosobruchus maculatus) mortality during storage in Jos - Plateau

The over dependence and continues use of synthetic insecticides to control storage pests have been associated with several demerits. This study was conducted to evaluate the insecticidal effect of peppermint (Mentha piperita) leaf powder on Callosobruchus maculatus. The peppermint plant was sourced locally and the C. maculatus were cultured to obtain the adult Bruchids. The peppermint was washed, dried under ambient temperature and pulverized. Complete Randomized Design was adopted for this trial with three replications of six treatment dosages of 2.5, 5.0, 7.5, 10.0, 12.5 and 0.0 g respectively of the plant material. The trial lasted for four weeks. High Bruchids mortality was observed after treatment with Mentha piperita leaf powder extract. Phytochemical screening of the test plant revealed presence of flavonoids, tannins, saponins, carbohydrates and cardiac glycosides. Descriptive statistic and analysis of variance (ANOVA) were used to analyze the data. Means (p≤0.05) were separated using Duncan Multiple Range Test (DMRT). Dosage rate and mean mortality values at the various doses were statistically significant after 48, 72 and 96 hours. The mortality could be attributed to high presence flavonoid in the Mentha piperita leaf powder. The results suggest that the leaf of peppermint has insecticidal property against adult C. maculatus. However, further trials are required to investigate effective dosage rates for other stored grains and to isolate and characterize the active flavonoids contained in the plant.

Exogenous salicylic acid modifies gas exchange and biomass production of Mentha x piperita L.

Peppermint (Mentha x piperita L.) is a medicinal plant that produces an essential oil used as an additive in food and pharmaceutical formulations. Salicylic acid is a phenolic compound widely distributed throughout the plant kingdom, being able to modify plant physiological and metabolic responses. The objective of this study was to evaluate the effects of the application of salicylic acid on the production of biomass, pigments, as well as gas exchange of peppermint plants. For this purpose, a completely randomized design composed of four replications was applied. Pigment evaluations were carried out in a 4x4 factorial scheme, consisting of the application treatments: 0 (control), 75, 150, and 225 mg L-1 of salicylic acid and four harvest periods. Gas exchange and physiological growth rates were evaluated in a 4x3 factorial scheme. Data were submitted to analysis of variance and regression. The application of salicylic acid increased CO2 assimilation and use, stomatal conductance, water use efficiency, and transpiration, which in turn, resulted in increased height, and dry stem and root mass production. It is concluded that the application of salicylic acid influences the primary metabolism, increasing gas exchange and biomass production of peppermint plants.

Economic valuable traits of promising breeding samples and ‘Chornolysta’ variety of Mentha piperita L. after in vitro sanitation and micropropagation

Purpose. To study the impact of clonal micropropagation and sanitation in vitro by viricide Ribavirin on ex vitro plant productivity, quantitative content and qualitative composition of peppermint essential oil components obtained from four breeding samples of peppermint plants (Mentha piperita L.) and the ‘Chornolysta’ variety. Methods . The study used methods of field agrotechnical one-factor experiment, essential oil distillation with water vapor according to the Ginzberg method, capillary gas chromatography and statistical analysis. Results. Due to the sanitation process in vitro, the yield of air-dried leaves of breeding samples increased by 2.9–7.1%, the ‘Chornolysta’ variety by 51.4% and rhizomes by 2.2–3.8% and 28.5% respectively, which amounted 0.35–2.74 t/ha. A significant increase of essential oil yield of breeding samples from 4.0 to 9.9 kg/ha was shown, and of the ‘Chornolysta’ variety – up to 28.6 kg/ha. After in vitro sanitation and clonal cropropagation of the breeding sample M 01-12, the content of essential oil was more than 4%. The following components of peppermint essential oil were identified: limonene, cineole, menton, mentofuran, isomenton, menthyl acetate, β-caryophyllene, isomenthol, menthol, pulegon, piperitone and carvone. A clear tendency to a decrease in the amount of menton and isomenthol with isomenton and menthol increase in plants, sanitated and propagated in vitro, was revealed. Conclusions . The use of tissue and organ culture methods and in vitro sanitation improves the qualitative composition of terpenoids by increasing the amount of menthol and menton reducing. The data obtained on the composition of terpenoids should be considered in peppermint selection as one of the integral criteria, which should be included in the list of economically valuable characteristics of peppermint plants, such as foliage, biomass of air-dried leaves, plant rhizomes and the amount of peppermint essential oil. Six indicators of the essential oil of the breeding sample M 01-02, namely citric acid, cineole, mentofuran, isomentone, pulegon, carvone, as well as the cineole / limonene ratio, meet the criteria of the European Pharmacopoeia, so it can be considered as promising for cultivation among the studied samples.

Evaluation of the efficacy of using ultraviolet radiation and the two extracts of peppermint and aloe vera plants in reduction Fumonisin B1 toxin and growth of Fusarium proliferatum isolated from imported banana fruits

The study was conducted in the laboratories of Faculty of Agriculture/University of Kufa for the period from 24/12/2017 to 24/2/2019 to isolate and diagnose fungi associated with imported bananas fruits (Musa spp.) in local markets. The study included five varieties of bananas for different origins to identify the ability of isolated fungi and their production for mycotoxins, including F. proliferatum. and evaluation of the effectiveness ultraviolet radiation uv-c with a wavelength of 254 nm, for 15 minutes and different concentrations of peppermint and aloevera extracts were evaluated their effectiveness in reducing of Fumonisin B1. The results showed the effect of UV-C and different concentrations of hot water extracts of peppermint and aloe vera to inhibit growth fungus F. proliferatum on PSA medium, a significant effect of peppermint extract,as it showed an inhibition of the growth fungus F. proliferatum. Concentration 1.5%, with amounted to 75.52% compared to control treatment, in which the percentage of inhibition was 0.00%. Ultraviolet light (UV-c) had a significant role in inhibiting the growth of the fungus. Inhibition which increasing the duration of the fungus exposure to ultraviolet (UV) radiation, as the duration of 15 minutes gave the highest rate of inhibition amounting to 81.35 % compared to control treatment of 0.00 %. The results also showed the high efficiency of ultraviolet radiation and peppermint extract at concentration of 1.5% in reducing toxicity of Fumonisin B1 and the protecting banana fruits from fungal infection, in addition to the possibility of prolonging the storage period.

Impact of Salicylic Acid Application on Growth, Photosynthetic Pigments and Organic Osmolytes Response in Mentha arvensis under Drought Stress

Background and Objective: The drought stress restricts the normal growth and development of plants. Salicylic acid (SA) is considered from the essential chemical compounds used to reduce the dangerous impacts of drought stress on plants. The objective of this study was to evaluate the growth attributes, some biochemical parameters of drought-stressed peppermint plants to salicylic acid application. Materials and Methods: A pot experiment was carried out to investigate the response of the morphological parameters (plant height, root length fresh and dry biomass), photosynthetic pigments (chlorophyll a and b, carotenoids and total pigments) and some organic osmolytes (proline, total soluble sugar and total soluble nitrogen) of peppermint (Mentha arvensis L.) grain pre-soaked in SA (0.05 M) and grown under drought conditions. Results: The data obtained in this study showed that drought stress significantly caused a massive reduction in the growth parameters and photosynthetic pigments but caused a remarkable increase in the root length and the organic osmolytes. Furthermore, the application of SA neutralized the reverse impacts of drought stress on the peppermint plant. The highest values of all the measured parameters were observed with droughted and nondroughted plants treated with SA. Conclusion: In general, results showed that water stress caused negative impacts on peppermint plant growth which was mitigated by the salicylic acid pre-soaking which was accompanying with some significant modification in some physiological processes. Moreover, these findings indicate that salicylic acid can be used to enhance the drought-tolerance in peppermint plant.

The influence of clonal micropropagation on productivity and differentiation of Mentha pіperіta plant tissues

Peppermint grass, as a raw medicinal plant material, has great importance for the pharmaceutical industry. The influence of clonal micropropagation and chemotherapy has been established in vitro on six breeds of Ukrainian selection peppermint plants, in particular on the sprouts’ conductive system structure and tissue development, general biomass accumulation, and in vivo productivity of breeds. The influence of clonal micropropagation and chemotherapy on important productivity indices of the plants has been established in vitro in six breeds of Ukrainian selection peppermint plants as pharmacopeial plants. The linear meter method, the microscopic method, the standard histochemical methods, and the statistical analysis method were used in the studies. A clear tendency to increase in the leaf cover, air-dry leafage and rhizome was observed in breeds of Ukrainian selection peppermint to which propagation and in vitro improvement technology was applied. The air-dry leafage yield significantly increased after in vitro culture from 7.6% in the Lidiia breed to 51.4% in the Chornolysta breed recognized as a state mint standard in Ukraine. The leaf cover increased from 8% to 21% in peppermint plants improved in іn vitro culture. This method promoted essential oil quantity increase from 9.8 to 28.6 kg per hectare. The rhizome yield increased by 6.3–40.4% in all peppermint plants breeds after improvement in in vitro culture on average within one vegetation year. The Lebedyna Pisnіa and Mama breeds were characterised by the most intensive development of all investigated anatomic and morphological indices after in vitro culture: rhizomes yield increased by 40.4% and 40.1%, air-dry leafage by 37.1% and 26.6%, leaf cover by 21.0% and 13.0%, and essential oil quantity per hectare increased by 38.1% and 28.5% accordingly. Anatomical and histochemical studies of sprouts of Ukrainian selection peppermint plants breeds confirmed increase in xylogenesis intensity in the majority of the studied breeds (except Lidiia and Ukrains’ka Pertseva) after in vitro culture improvement. The xylogenesis process was most expressed in the Mama and Chornolysta breeds. Air-dry leafage, rhizome yield, and leaf cover increased in all peppermint plants breeds after in vitro improvement, which could be critical for the pharmaceutical industry.

Plant growth promoting rhizobacteria improve the antioxidant status in Mentha piperita grown under drought stress leading to an enhancement of plant growth and total phenolic content

An experiment was conducted to investigate the effects of plant growth promoting rhizobacteria (PGPR) on Mentha piperita grown under drought stress. We performed root inoculation with strains of two PGPR species (Pseudomonas fluorescens WCS417 r and Bacillus amyloliquefaciens GB03) on peppermint plants and subjected them to moderate (MS) or severe drought stress (SS). To determine the growth-promoting potential and ability of PGPR to increase the drought tolerance in peppermint, different plant growth parameters were measured, along with the activities of antioxidant enzymes such as peroxidase (PX) and superoxide dismutase (SOD), as well as the non-enzymatic antioxidant proline and total phenolic content (TPC). In addition, to determine whether drought stress induces oxidative damage in peppermint, membrane lipid peroxidation was analyzed. An increment in the level of drought stress produced a reduction in plant growth, fresh weight, leaf number and leaf area. However, these negative effects of drought were mitigated in plants exposed to PGPR inoculation, resulting in significantly less reduction in the above growth traits related to plants not treated with PGPR, regardless of the severity of the drought treatment. In addition, drought-stressed plants treated with PGPR had a significantly higher total phenolic content than water-stressed plants without PGPR. Higher enzymatic activities were also observed in drought-stressed plants inoculated with PGPR. The proline content did not change in stressed plants, but inoculation reduced the amount of proline in the different stressed conditions tested. Membrane lipid peroxidation was also decreased in inoculated plants grown under drought conditions.These results are important as they illustrate the potential of PGPR to mitigate the adverse consequences of drought stress, and offer a way of increasing the tolerance of peppermint plants grown and TPC under water deficit conditions.

Essential Oil Composition at Different Plant Growth Development of Peppermint (Mentha x piperita L.) Under Water Deficit Stress

Peppermint is one of the most important and commonly used medicinal and aromatic plants worldwide. Present experiment was conducted to evaluate the essential oil content and quantitative changes of the main components of peppermint plants at different stages of crop growth. Greenhouse pots with peppermint Plants (30, 60 and 90 days after transplanting) were subjected to three different field capacity (FC) irrigation conditions, i.e. no stress, mild stress (60±5 % FC) and moderate stress (40±5 % FC) for one month. Essential oil composition and accumulation in peppermint was differentþ by plant growth stage alterations. The proportions of some monoterpene such as menthofuran, limonene, and pulegone decreased as plant matured, while those of menthol, cineole, and neomenthol increased. Both mild and moderate water stresses changed the essential oil content. Essential oil content of plants subjected to mild stress increased while moderate water stress treatment caused a significant reduction in essential oil content in different plant growth stage. Moderate stress reduced the essential oil percentage and changed the essential oil profile. Menthone content decreased and menthofuran content increased under moderate stress. Also, relative proportions of sesquiterpenes increased with water stress.

Two arrays of defense strategies of Brassicaceae plants that eavesdrop on mint volatiles

ABSTRACT Brassica rapa can eavesdrop on volatile compounds emitted from peppermint and consequently boost its defense responses against Plutella xylostella. In the current study, to assess how B. rapa receiver plants cultivated near peppermint plants resist P. xylostella, two biological assays were conducted. The data showed that the receiver plants cultivated with peppermint exhibited lower weight gain of P. xylostella larvae, compared to that exhibited by non-receiver plants. Moreover, a lower rate of oviposition of adult female P. xylostella was observed on B. rapa plants cultivated with peppermint plants compared to the rate on B. rapa plants cultivated with glass-enclosed peppermint plants, although receiver B. rapa plants that had been previously incubated with peppermint for 7 days and non-receiver B. rapa plants exhibited similar rates of oviposition. Taking all these findings together, we conclude that cultivation of B. rapa receiver plants with peppermint results in two arrays of defense strategies.

Impact of effective microorganisms on weed infestation and yield of peppermint cultivated on muck-peat soil

Peppermint (<em>Mentha ×piperita</em> L.) rootstock cuttings with 9–11 internodes were planted on April 10, 2014 in rows 50 cm apart and with 25-cm distance in the row, on well fertilized muck-peat soil containing 82.1% of organic matter with a pH of 5.9. Peppermint plants were sprayed once with an activated EM-1 preparation, then on two or three further occasions as follows: at 10 cm height (May 10), at branching stage (May 29), and during rapid growth (June 19). EM did not affect peppermint growth or yield. Yields of the fresh and dry herb were high (means: 15,563 and 2,661 kg ha<sup>−1</sup>, respectively) and characterized by a medium (1.85–1.90%) essential oil content in the dry herb. Twenty-nine compounds were identified in the oil and its main components were menthol (53.1–58.5%), menthone (14.6–16.8%), isomenthone (6.3–6.7%), menthyl acetate (4.0–5.0%), germacrene D (2.3–3.4%), ß-caryophyllene (1.8–2.4%), viridiflorol (1.5–2.3%), and 1,8-cyneole (0.3–3.7%). EM did not affect the content of essential oil in the dry herb or the oil composition (except for 1,8-cyneole). Thirty-four days after planting, 22 weed species grew in the experimental plots and the dominant were common meadow grass (<em>Poa pratensis</em> L.) accounting for 20% of total weed population, annual meadow grass (<em>Poa annua</em> L.) 17%, common chickweed [<em>Stellaria media</em> (L.) Vill.] 20%, creeping yellowcress [<em>Rorippa sylvestris</em> (L.) Besser] 8%, hairy galinsoga [<em>Galinsoga ciliata</em> (Raf.) S. F. Blake] 7%, gallant soldiers (<em>Galinsoga parviflora</em> Cav.) 6%, Canadian horseweed [<em>Conyza canadensis</em> (L.) Cronq.] 6%, common groundsel (<em>Senecio vulgaris</em> L.) 5%, and annual nettle (<em>Urtica urens</em> L.) 5%. Other species occurred sporadically. The total number and fresh weight of weeds growing on 1 m<sup>2</sup> were 412 and 246 g on plots treated with EM and 389 and 227 g on control plots, respectively, but the differences were not statistically significant.

Transcriptome profiling of peppermint (Mentha piperita) with improved antioxidant properties in response to salicylic acid elicitation

Peppermint (Mentha piperita) is a plant widely consumed as infusion due to its beneficial health properties that are related to its phytochemical profile, which has been shown to improve with the foliar application of salicylic acid to the plants during their cultivation. However, analysis of transcriptome changes induced by the application of salicylic acid in peppermint, have not been previously reported. In order to identify the genes involved in salicylic acid signaling, the RNA sequencing strategy was employed to evaluate the transcriptional profiles in peppermint. Results showed 178,723,476 high-quality reads, of which, 77.89% corresponded to the salicylic acid elicited peppermint, whereas the remaining 22.11% was from controls plants. We found that foliar treatment with salicylic acid in peppermint plants had an important influence in many relevant biological processes, mainly photosynthesis, light response, transport of protons and phenylpropanoid pathway. Therefore, these results might explain the improvement of the bioactive metabolites concentration and nutraceutical properties induced by salicylic acid in peppermint observed in previous studies.

Transitions in nutation trajectory geometry in peppermint (Mentha x piperita L.) with respect to lunisolar acceleration.

Nutations of plant organs are significantly affected by the circatidal modulation in the gravitational force exerted by the Moon and Sun (lunisolar tidal acceleration, Etide). In a previous study on nutational rotations of stem apices, we observed abrupt alterations in their direction and irregularities of the recorded trajectories. Such transitions have not yet been analysed in detail. Peppermint plants were continuously recorded with time-lapse photography and aligned with contemporaneous time courses of the Etide estimates. Each nutational stem tip movement path was assigned to one of two groups, depending on its geometry, as: (i) regular elliptical movements and (ii) irregular movements (with a random type of trajectory). Analyses of the correlation between the plant nutation trajectory parameters and Etide, as well as of the trajectory geometry of the individual plants were performed. The trajectory geometry of young mint stem apices was related to the velocity of the apex rotation and significantly affected by the gravitational force estimated from the Etide. A low velocity of nutational movement, associated with the random character of the trajectory, usually occurred simultaneously with local minima or maxima of Etide. As the mint plant ages, the transitions in the stem tip trajectory were limited; no correspondence with Etide dynamics was observed. The results indicate that the plant tip geometry path transitions with respect to the changing gradient of lunisolar tidal acceleration could be interpreted as manifestation of a continuous accommodation of the shoot apical part to the state of minimum energy dissipation.

Effect of clonal reproduction on quantitative indices and component composition of essential oil of peppermint varieties

Quantitative and qualitative composition of essential oils of peppermint breeds Lebedinaya Pesnya, Lubenchanka, Lidiya, Ukrainskaya Perechnaya, Mama, Chornolista was investigated before and after clonal microreproduction by the method of isolated tissues and bodies culture in vitro. Methods of essential oil steam distillation, capillary gas chromatography and statistical analysis were used in the research. It is established that increase in essential oil quantity was observed for peppermint breeds on which reproduction and improvement іn vіtro technology was applied. As a result of clonal microreproduction of peppermint plants in culture іn vіtro on nutrient medium Murasige and Skug, in which the growth regulators 0.75 mg/l of 6-benzylaminopurine, 0.1 mg/l of adenine, 0.05 mg/l of indolil-3-acetic acid and 0.5 mg/l of gibberellins acid were added and virocide Ribavirin in concentration 10 mg/l, improvement was obtained in comparison with vegetatively reproduced plants; increase in essential oil quantity per hectare was established for the following breeds; Chornolista by 54.2%, Lebedinaya pesnya by 38.2%, Ukrainskaya Perechnaya by 36.7%, Mama by 28.5%, Lubenchanka by 17.1% and Lidiya by 11.6%. For oil content the highest indices were noted for Lubenchanka, Mama and Lebedinaya Pesnya peppermint breeds with product yield 4.02%, 3.98% and 3.84% respectively. It was established that the essential oil component composition in non-clonal peppermint plants raw materials and plants-regenerants after culture in vitro is variable depending on breed. Limonene, cineole, menthone, menthofuran, iso-menthone, menthyl acetate, β-caryophyllene, iso-menthol, menthol, pulegone, germacren, piperitone, carvone were identified in peppermint essential oil. High content of menthol, low content of carvone, piperitone, pulegone (except for Chornolista, Ukrainskaya Perechnaya breeds) and menthofuran (except for Chornolista, Ukrainskaya Perechnaya and Lubenchanka breeds) are characteristic for Ukrainian selection peppermint investigated breeds. A clear tendency to menthol and menthone content ratio increase is observed in plants which were improved in conditions іn vіtro. Pulegone was not detected in essential oil samples of Lebedinaya Pesnya, Lidiya and Mama breeds. Biochemical markers of Lebedinaya Pesnya, Lubenchanka, Mama breeds, which differentiate them within the group of investigated breeds, are higher limonene, piperitone and menthol pool; for Ukrainskaya Perechnaya and Chornolista breeds – pulegone, cineole and menthone; for Lidiya breed – iso-menthone.