Growth Of Peppermint Research Articles

Regulating the luminescence properties of Eu2W3O12 red-emitting phosphor via rare-earth ions doping for optical thermometry, white light-emitting diode and plant growth applications

To fulfil various applications, series of rare-earth (RE) ions (i.e., La3+, Gd3+, Sm3+) doped Eu2W3O12 (EWO) phosphors were synthesized. All the designed phosphors can emit glaring visible lights from Eu3+ and their fluorescence intensities were significantly enhanced through RE ions doping. To explore the impact of RE ions doping on the symmetric properties of Eu3+ in studied samples, theoretical calculation based on Judd-Ofelt theory was performed. Moreover, through utilizing temperature-related emission spectra, the thermal quenching behaviors of resultant phosphors were studied and found that their thermal stability had been improved by adding RE ions. Furthermore, the thermometric properties of designed phosphors were examined through adopting the single-band ratiometric technique to analyzing the temperature-dependent fluorescence intensity ratio of the emission band arising from 5D0 → 7F2 transition of Eu3+. It is found that maximum absolute and relative sensitivities of resulting phosphors were 0.197 and 1.202 % K−1, respectively. Additionally, two types of devices, i.e., white light-emitting diode (white-LED) and red-emitting LED, where the prepared phosphors play as red-emitting components, were fabricated. The packaged white-LEDs can emit warm white light with high color rendering index and low correlated color temperature, which are insensitive to operating current. Considering the red-emitting LEDs, their emission bands overlap with the absorption bands of plant pigments, which can promote plant growth and it was verified by peppermint growth experiments. These results verify that the introduction of RE ions is a feasible approach to modify the luminescence performances of phosphors to realize diversified applications.

Bio-fertilizer as a pathway to minimize nitrate leaching from chemical fertilizer in high yield peppermint production

The contamination of Iran's underground water sources with nitrate from chemical fertilizers poses a significant health risk to communities reliant on this essential water source. This study investigates the benefits of organic alternatives, such as vermicompost and bio-fertilizers, in sustainable peppermint production. The aim is to foster environmentally friendly agricultural practices and enhance soil health. Multiple fertilizer treatments were examined for their impact on peppermint growth, essential oil (EO) content, and bioactive properties. Results show that incorporating vermicompost with chemical or bio-fertilizers significantly improves plant height, dry leaf weight, leaf number, and drug fraction by 18.6%, 82%, 27.5%, and 25%, respectively. Vermicompost application leads to a remarkable 100% increase in EO content and a substantial 31.5% rise in menthol percentage compared to other treatments. Furthermore, the study reveals that enhanced menthol production coincides with improved antibacterial and antifungal properties of the plant extract and EO. Treatments with bio-fertilizers demonstrate a significant 23.4% increase in menthol percentage compared to the control group. Vermicompost usage also boosts the total phenolic, flavonoid, and anthocyanin content, along with the antioxidant capacity by 5%–17%. Replacing chemical fertilizers with vermicompost and bio-fertilizers shows notable improvements in peppermint production. These findings underscore the significance of employing organic fertilizers as a means to advance sustainable agricultural practices, mitigate health hazards linked to water contamination, and optimize the cultivation of peppermint as a globally valuable medicinal plant.

Response of mint varieties from Central Europe (Mentha spp.) to Meloidogyne infestation

Mentha is a cosmopolitan genus of medicinal and aromatic plants, which is characterised by the essential oils in its leaves and its therapeutic and aromatic qualities. Mint species are usually cultivated as a perennial crop and therefore susceptible for various pests and diseases. Root-knot nematodes of the genus Meloidogyne are one of the pathogens that can reproduce on mint and cause plant growth reduction. To better understand the pathogenicity of Meloidogyne on mint we studied whether an increasing number of Meloidogyne affects plant growth and essential oil content in the leaves. For our greenhouse experiments, we selected peppermint (Mentha x piperita ˈMultimenthaˈ) as the major mint variety cultivated in Central Europe and the root-knot nematode M. hapla that can pose a major threat in temporal regions. In addition, we evaluated the pathogenicity and reproduction of M. chitwoodi, M. fallax and M. incognita on peppermint and other commonly grown mint varieties in Central Europe, i.e. Mentha x piperita ˈFränkische Blaueˈ, apple mint (M. rotundifolia) and spearmint (M. spicata). None of the studied root-knot nematode species had a negative impact on plant growth of peppermint ˈMultimenthaˈ. However, high densities of M. hapla caused a reduction in the essential oil content. In conclusion, peppermint ˈMultimenthaˈ turned out to be a good host for M. hapla, but a non-host for M. chitwoodi, M. fallax and M. incognita. Plant growth of all four mint varieties was not affected by M. hapla infestation. In addition, peppermint ˈMultimenthaˈ and spearmint were more susceptible to M. hapla than apple mint and peppermint ˈFränkische Blaueˈ.

Exogenous melatonin differentially affects biomass, total carbohydrates, and essential oil production in peppermint upon simultaneous exposure to chitosan-coated Fe3O4 NPs

Melatonin and iron play important roles in the growth processes and production of secondary metabolites in medicinal plants. To evaluate the effects of melatonin and Chitosan-Coated Iron Oxide Nanoparticles (Fe-CTs NPs) on peppermint growth, essential oil content and constituents, total carbohydrates and antioxidant enzyme activities, a factorial experiment was conducted based on randomized complete block design (CRBD) with three replications (n = 3). Treatments consisted of different concentrations of melatonin (0, 100, and 200 mg L−1) and Fe-CTs NPs (0, 7.5, and 15 mg L−1). During the experiment, foliar applications of melatonin and Fe-CTs NPs were performed three times with 20 days’ interval. Treatments with melatonin, and Fe-CTs NPs had significant effects on the studied traits. The results showed that with increasing melatonin and Fe-CTs NPs concentrations, fresh and dry weights, total carbohydrates, and leaf area index were significantly (P < 0.05) increased in treated plants. The highest CAT and APX activities were observed in plants treated with melatonin at 100 mg L−1 and Fe-CTs NPs at 15 mg L−1. Eucalyptol, Menthyl acetate, Thiophene, 2-ethyl-5-(2-methylpropyl), Mint furanone, and Viridiflorol were found as the major essential oil constituents in peppermint plants under experimental treatments. Moreover, analytical results showed that the highest amount of Menthol (38.48 %) was obtained in plants exposed to Fe-CTs NPs at 7.5 mg L−1, however, the highest L-Menthone (30.53 %) was observed in plants treated with melatonin at 200 mg L−1 and Fe-CTs NPs at 15 mg L−1. The findings provide insights into the regulatory mechanisms of melatonin and Fe-CTs NPs on peppermint growth, physiology and biosynthesis of volatile compounds.

Antifungal Activity and Alleviation of Salt Stress by Volatile Organic Compounds of Native Pseudomonas Obtained from Mentha piperita.

As salt stress has a negative impact on plant growth and crop yield, it is very important to identify and develop any available biotechnology which can improve the salt tolerance of plants. Inoculation with plant-growth-promoting rhizobacteria (PGPR) is a proven environmentally friendly biotechnological resource for increasing the salt stress tolerance of plants and has a potential in-field application. In addition, bacterial volatile organic compounds (mVOCs) are signal molecules that may have beneficial roles in the soil-plant-microbiome ecosystem. We investigated the effects of mVOCs emitted by Pseudomona putida SJ46 and SJ04 on Mentha piperita grown under different levels of NaCl stress by evaluating their growth-promoting potential and capacity to increase salt tolerance effects. Furthermore, we evaluated under control and salt stress conditions the biocontrol ability of VOCs emitted by both these strains to inhibit the growth of Alternaria alternata and Sclerotium rolfsii. The VOCs emitted by both strains under control conditions did not lead to an significant improvement in peppermint growth. However, under salt stress conditions (75 or 100 mM NaCl), an amelioration of its physiological status was observed, with this effect being greater at 100 mM NaCl. This led to an enhancement of the number of leaves and nodes and, increased the shoot fresh and root dry weight by approximately twice in relation to control stressed plants. Moreover, the VOCs released by the two bacteria grown in control or saline media showed a significant reduction in the mycelial growth of A. alternata. In contrast, S. rolfsii growth was reduced 40% by the mVOCs released only under control conditions, with no effects being observed under salt stress. We also explored the composition of the bacterial volatile profiles by means of a solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) analysis. From the headspace of SJ46, three VOCs were identified: n-octanol, decane and tetradecane. The emission of SJ04 had the same chromatographic profile, with the addition of two more compounds: 1-(N-phenyl carbamyl)-2-morpholino cyclohexene and tridecane. Only compounds that were not present in the headspace of the control groups were recorded. The salt stress conditions where the bacteria were grown did not qualitatively modify the mVOC emissions. Taken together, our results suggest that plant-associated rhizobacterial VOCs play a potentially important role in modulating plant salt tolerance and reducing fungal growth. Thus, biological resources represent novel tools for counteracting the deleterious effects of salt stress and have the potential to be exploited in sustainable agriculture. Nevertheless, future studies are necessary to investigate technological improvements for bacterial VOC application under greenhouse and open field conditions.

A new method in mitigation of drought stress by chitosan-coated iron oxide nanoparticles and growth stimulant in peppermint

Damage to the plant's photosynthetic system is known as the main symptoms of sensitivity to environmental stresses. Little is known about beneficial role of new chitosan compounds such as Kitoplus®, and chitosan-coated nanomaterials on alleviation of adveres effects of drought stress in plants. In the present study, a factorial experiment was conducted in a split-plot manner based on a randomized complete block design (RCBD) with three replications to evaluate the effects of Kitoplus® growth stimulant and Chitosan-Coated Iron Oxide Nanoparticles (Fe-CTs NPS) on peppermint growth, chlorophyll fluorescence and essential oil biosynthesis under drought stress conditions. Treatments included three levels of drought stress (irrigation at soil moisture levels of 30%, 60%, and 90%), three concentrations of Kitoplus®(control without Kitoplus®, 0.5% and 1%), and three concentrations of Fe-CTs NPs (control without Fe-CTs NPs, 5 and 10 µM). Drought stress, growth stimulation treatment with Kitoplus®, and Fe-CTs NPs had significant dual and triple effects on the studied physiological traits. According to the results, chlorophyll index and stomatal conductance were significantly lower in control plants than in those undergoing drought stress. Under 60% field capacity moisture conditions, the chlorophyll index was increased with 1% Kitoplus® treatment. The maximum fluorescence (Fm) and variable fluorescence (Fv) raised as the drought stress intensity increased. The highest Fm and Fv were observed in plants treated with 1% Kitoplus® and 10 µM Fe-CTs NPS under 30% soil moisture stress . Results also showed that the highest value of menthone (33.31%) was obtained in plants treated with Kitoplus® at 1% and Fe-CTs NPs at 10 μM under drought stress of 60% field capacity. In addition, the highest amount of menthol (26.5%) was observed in plants treated with 0.5% Kitoplus® under drought stress of 30% field capacity. The overall importance of the study lies in devising the simultaneous application of biostimulants and nanomaterials in enhancing essential oils production in the mint plant under drought stress challenges. • Peppermint Vegetative yield improved by increasing the concentration of Kitoplus® and Fe-CTs NPS. • Menthol's highest amount was observed in plants with Kitoplus® (0.5%) and Fe-CTs NPs (10 μM) interaction under 90% FC. • The highest amount of menthol was observed in plants following interaction of Kitoplus® (0.5%) and Fe-CTs NPs (10 μM) under 90% FC. • The maximum menthone obtained in plants treated with Kitoplus® (1%) and Fe-CTs NPs (10 μM) under drought stress of 60% FC. • Chlorophyll fluorescence in plants treated with Kitoplus® and Fe-CTs NPS was significantly higher than that of controls.

Pepermint (Mentha piperita L.) growth and biochemical properties affected by magnetized saline water.

Due to the limitation of suitable water for crop production in the world, recycling water is among the most proper methods enhancing water efficiency and availability. One modern method, which is of economic, health, and environmental significance, and may improve water properties for plant use is water magnetization. Medicinal plants are of nutritional, economic and medical values and their growth decreases under salinity stresses. This research was hypothesized and conducted because there is not any data, to our knowledge, on the use of magnetized salty water affecting the growth and biochemical properties of peppermint (Mentha piperita L.). The experiment was a split plot design with three replicates. The main plots consisted of magnetic fields at control (M1), 100mT (M2), 200mT (M3), and 300mT (M4), the sub-plots consisted of salinity treatments (NaCl) at control (S1), 4dS/m (S2), 8dS/m (S3), and 12dS/m (S4), and the growth media including cocopeat (X1), palm (X2), cocopeat+perlite (V/V=50, X3) and palm+perlite (V/V=50, X4) were located in the sub-sub-plots. Different plant growth and biochemical properties including plant fresh and dry weight, plant menthol, menthone, chlorophyll and proline contents were determined. Analysis of variance indicated the significant effects of experimental treatments and their interactions on the growth and biochemistry of peppermint. Different magnetic fields significantly increased plant growth, and interestingly with increasing the salinity level the alleviating effects of magnetic field on salinity stress became more clear (significant interaction between salinity and magnetic field treatments). Cocopeat was the most efficient growth medium. At the third level of salinity (8dS/m) just the two levels of 100 and 200mT increased plant menthol concentration. Treatments M3S2X4 and M1S1X1 resulted in the highest (38%) and the least menthol percentage (13%), respectively. Treatments S2 and M2 and M3 significantly increased plant menthone concentration, especially in the growth media of X1 and X3. However, at the third level of salinity, M3 and M4 were the most effective treatments. The highest (25.8%) and the least (1.2%) concentrations of menthone were related to treatments M3S2X4 and M2S4X1, respectively. The results indicated that it is possible to alleviate the stress of salinity on peppermint growth and improve its biochemical (medicinal) properties using magnetized salty water, although proline concentration was not much affected by the magnetic field.

Improving growth, phytochemical, and antioxidant characteristics of peppermint by phosphate-solubilizing bacteria along with reducing phosphorus fertilizer use

Phosphorus is a vital nutrient for plant growth and development. Its deficiency in farmlands is obviated by the phosphate fertilizer application. Excessive consumption of phosphate fertilizers harms to human health and the environment. Some soil bacteria are capable to increase phosphate fertilizers efficiency. Two-year field experiment was conducted to evaluate the effect of phosphate-solubilizing bacteria inoculation with phosphorus fertilizer on growth, antioxidant status, and phytochemical features of peppermint (Mentha piperita L.). The treatments were three amounts triple superphosphate (0, 50, and 100 kg ha−1) and PSB strains (Pseudomonas putida and Pantoea agglomerans) which were arranged as factorial based on randomized complete block design. The results showed that phosphorus supplying by chemical fertilizer or PSB improved peppermint growth features included stem number, leaf length, leaf number, and dry weights of leaf, stem, and plant. The contents of photosynthetic pigments increased by chemical or biological phosphorus fertilizer application. The application of PSB with triple superphosphate reduced soluble carbohydrates and increased protein. The antioxidant enzymes activities including catalase, peroxidase, ascorbate peroxidase, and polyphenol oxidase were increased by the PSB inoculation. In contrast, activities of these enzymes were reduced by the triple superphosphate application. The highest EO yield was obtained by Pseudomonas putida and Pantoea agglomerans inoculation as phosphate-solubilizing bacteria with 50 kg ha −1 triple superphosphate. The menthol content was increased in response to the triple superphosphate and the PSB inoculation. Therefore, PSB inoculation increased phosphate fertilizer efficiency which leads to reducing phosphate fertilizer consuming and increasing the plant biomass as well as EO yield.1

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

Peppermint (&lt;em&gt;Mentha ×piperita&lt;/em&gt; 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&lt;sup&gt;−1&lt;/sup&gt;, 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 (&lt;em&gt;Poa pratensis&lt;/em&gt; L.) accounting for 20% of total weed population, annual meadow grass (&lt;em&gt;Poa annua&lt;/em&gt; L.) 17%, common chickweed [&lt;em&gt;Stellaria media&lt;/em&gt; (L.) Vill.] 20%, creeping yellowcress [&lt;em&gt;Rorippa sylvestris&lt;/em&gt; (L.) Besser] 8%, hairy galinsoga [&lt;em&gt;Galinsoga ciliata&lt;/em&gt; (Raf.) S. F. Blake] 7%, gallant soldiers (&lt;em&gt;Galinsoga parviflora&lt;/em&gt; Cav.) 6%, Canadian horseweed [&lt;em&gt;Conyza canadensis&lt;/em&gt; (L.) Cronq.] 6%, common groundsel (&lt;em&gt;Senecio vulgaris&lt;/em&gt; L.) 5%, and annual nettle (&lt;em&gt;Urtica urens&lt;/em&gt; L.) 5%. Other species occurred sporadically. The total number and fresh weight of weeds growing on 1 m&lt;sup&gt;2&lt;/sup&gt; 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.

Streptomyces strains alleviate water stress and increase peppermint (Mentha piperita) yield and essential oils

Drought is the most significant factor limiting plant production in a majority of agricultural fields worldwide. PGPRs (plant growth promoting rhizobacteria) are beneficial soil microorganisms, promote plant growth under normal and stress conditions. In a greenhouse study, the PGP potential of two salt-tolerant antagonistic Streptomyces (S. rimosus strain C-2012 and S. monomycini strain C 801) on peppermint growth and essential oils (EOs) content and composition under normal and water stress was evaluated. To realize the practical use of the PGPR strains, a field experiment was also carried out. In greenhouse and field experiments, soil inoculated with strain C-2012 and C 801 increased shoot fresh and dry weight compared to the non-inoculated controls. Strain C-2012 enhanced shoot dry weight 74% and 63% in greenhouse and field, respectively. Water stress decreased shoot fresh and dry weight but increased EOs and menthol content compared to normal irrigation. In stress conditions, inoculation with PGP strains increased plant growth, total EOs and menthol content. The frequency of soil inoculation with each strain resulted in different effects on plant growth and EOs content and composition. To our knowledge, this is the first report on the application of PGPR Streptomyces strains to increase peppermint and its EOs yield in greenhouse and field conditions. Our results certify the beneficial role of the salt-tolerant antagonistic Streptomyces strains to increase biomass and EOs content of peppermint and also to save water.

Influence of biochar amendment on herb growth in a green roof substrate

The objectives of this research were: 1) to assess the effect of biochar incorporation on the growth of basil (Ocimum basilicum ‘Genovese Compact, Improved’) and peppermint (Mentha × piperita) and, 2) to determine the physical characteristic differences in heat-expanded clay (HEC) substrate following incorporations of biochar at 5%, 10%, or 15% (by volume). A commercially-available green roof substrate, Rooflite Intensive Ag (IA) substrate, was included for comparison. The IA substrate had the highest total porosity (TP), container capacity (CC), and air-filled porosity (AP). The HEC substrate showed a linear increase in TP and CC and a linear decrease in dry bulk density with increasing amounts of biochar. The commercially available IA substrate had the highest water retention (CC = 25.0%). Overall, there was a maximum increase of peppermint shoot dry weight (g/shoot) response in the HEC substrate using 15% biochar. Coverage area measurements indicated that peppermint benefited more than basil from the incorporation of biochar. Biochar alone did not influence stomatal conductance, although basil or peppermint grown in the IA substrate had higher stomatal conductance than plants grown on HEC with all three biochar incorporation rates at 3 and 4 d after irrigation, probably due to the lower aboveground biomass of the IA-grown plants. In conclusion, the addition of biochar amendment to HEC substrate had a minor influence on peppermint growth and no influence on stomatal conductance of either basil or peppermint.

Efeitos da adubação química e da calagem na nutrição de melissa e hortelã-pimenta

O trabalho objetivou avaliar os efeitos da adubação química e da calagem no crescimento e na nutrição da melissa (Melissa officinalis) e hortelã-pimenta (Mentha piperita), com a técnica da diagnose por subtração. Os tratamentos foram: Completo (adubado com N, P, K, S, B, Cu, Fe e Zn+ calagem); Completo calagem; Completo N; Completo P; Completo K; Completo S; Completo B; Completo Zn; Completo Fe e Testemunha (solo natural). Após 120 dias da semeadura a calagem e a adubação mostraram ser essenciais para o crescimento de melissa e hortelã-pimenta. No solo utilizado, a falta da calagem e dos nutrientes N e P causaram as maiores quedas ou ausência, no caso da falta de calagem em melissa, na produção de folhas, órgão usado na medicina popular e que contém os princípios ativos.

In vitro and in vivo peppermint (Mentha piperita) growth promotion by nonmycorrhizal fungal colonization.

• Here peppermint growth and terpene production of in vitro generated plants (Mentha piperita) in response to inoculation with a leaf fungal endophyte were characterized. • Peppermint plants were studied by means of morphometric, biochemical and image analysis, employing both in vitro and in pot cultures. Leaf essential oils were analysed by gascromatography-mass spectrometry. • The endophyte induced profound effects on the growth of peppermint, which responded with taller plants bearing more expanded leaves. The observed increase of leaf dry matter over leaf area suggested a real improvement of peppermint metabolic and photosynthetic apparatus. Root architecture was of the herring-bone type, showing greater dry biomass percentage over the total. A sustained lowering of (+)-menthofuran and an increase of (+)-menthol percentage concentrations were found in plants from both in vitro and pot cultures. • The study represents the first report on specialized endophytic fungi in peppermint green tissues and highlights some of the principal morphological and biochemical aspects of this mutualism. Effects exerted on plant growth and essential oil production in peppermint suggest further biotechnological applications.

Conceptual design of LED-based hydroponic photobioreactor for high-density plant cultivation

A novel hydroponic photobioreactor is proposed for high-density cultivation of plants. This cultivation can be achieved by growing plants on a floatable platform, allowing the roots to directly contact a continuously aerated nutrient solution. Plant growth of Mentha x piperita (peppermint) can be shown to strongly correlate with the light intensity at incident light intensities between 0 and 650 &mgr;mol m(-)(2) s(-)(1). For a constant incident light intensity (I(0) = 420 &mgr;mol m(-)(2) s(-)(1)), the overall specific growth rates of these plants are found to be strongly dependent on the plant density. They range from 0.023 to 0.075 d(-)(1) for plants grown at a density range from 16 to 256 plants m(-)(2). A simple mathematical model is presented that allows one to predict these effects of light intensity and plant density on peppermint growth. Light delivery is derived from the modification of Beer-Lambert's law. From this, the relationship between the light extinction coefficient and plant density can be experimentally determined. The light transport can then be coupled with plant growth kinetics under light-limiting conditions. The predicted growth results agree reasonably well with most experimental results from a growth period of 17-20 days. On the basis of these simulation results, we suggest that a more efficient way of delivering light to this photobioreactor can be attained by supplying light from both the top and the bottom of the plant shoots. The proposed design takes advantage of the small size and low weight of light emitting diodes, which allow them to be mounted on platforms for delivering light closer to the plants.

Irrigation of Peppermint for Optimal Yield

AbstractLittle field research has documented the water use of peppermint (Mentha piperita L.), an important irrigated crop of the Pacific Northwest grown for oil and tea leaves. Our objective was to determine a peppermint yield—water use function and to develop a crop coefficient (Kc) to relate crop evapotranspiration (ET) to potential ET. Trials were conducted from 1992 to 1994 at Madras, OR on a Madras loam mesic Aridic Argixeroll (fine‐loamy, mixed, mesic Xerollic Duriargid). A line‐source sprinkler irrigation system was used to impose five irrigation treatments ranging from 30 to 120% of the ET required for maximum yield. Evapotranspiration was measured by monitoring the water balance components of irrigation, precipitation, drainage, and soil water storage. Peppermint yield was sensitive to irrigation, with both deficit and excess irrigation lowering oil yields compared with the optimum treatment, which was 324, 388, 364, and 487 mm season‐1 for the four trials. Peppermint ET‐yield functions exhibited a greater transpiration component (89%) than other crops due to its thick canopy that reduces soil evaporation. The highest yielding irrigation treatment kept the soil water pressure between −18 and −50 kPa in the top 0.3 m. The Kc followed the general three‐lines model with an initial value of 0.3 that increased to 0.85 at mid‐season and declined to 0.5 at harvest. Thermal units were used to normalize the inflection points for the Kc curve for 2 yr of the trial (1993 and 1994). Late winter tillage in 1992 delayed peppermint growth and shifted the Kc curve.

Growth of Peppermint in Compost

ABSTRACT To evaluate compost as a medium for production of herbs, peppermint (Mentha × piperita L.) was grown in flats of compost in a greenhouse. Composts were made from mixed municipal solid wastes (one high in ammonium; one low in ammonium), biosolids (sewage sludge) mixed with woodchips (one mature, one immature), agricultural wastes, autumn leaves, and yard wastes. The agricultural, leaf, and yard-waste composts were mature. Shoot growth of mint was recorded after an 8-week growth period. Ammonium and nitrate concentrations, electrical conductivity, and pH of composts were determined at the initiation and at intervals during the experiment. Shoot growth was vigorous in all composts except the immature biosolids-woodchips and yard waste composts. Except for the leaf and yard waste composts, these media had sufficient nitrogen for plant growth. High initial ammonium concentrations and high salinity in immature biosolids-woodchips compost were responsible for inhibited shoot growth. Ammonium concentrati...

Effect of Deuterium Oxide on the Growth of Peppermint II.: Histological effects

Representative sections of leaf, stem, and root of peppermint plants grown in 70 per cent D 2 O nutrient were examined microscopically; comparison was made of the significant histological features with sections from plants grown in an aqueous nutrient. The major effect of deuterium on the growth of peppermint appears to be inhibition of cell divisions. Parenchyma cells are enlarged and vascular tissue appears to be reduced in the deuteriated plants. In general, the effects were more pronounced in growing tissues than in tissue exposed to deuterium after differentiation had occurred.