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Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata



S.F. Hendawy, M.S. Hussein, A.E. El-Gohary and M.E. Ibrahim
 
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ABSTRACT

This study was carried out to evaluate the response of Mintha piperita var. citrata (Eau de Cologne mint) to foliar fertilization under Egyptian conditions. This study was carried out on Mintha piperita var. citrata (Eau de Cologne mint) at Sekem Experimental field. Fresh, healthy, insect and disease free suckers were transplanted in furrow at a depth of 4-5 cm as per the treatments. Three weeks later after transplanting, the plants were sprayed with aqueous solution of the test nutrient compounds humic acid (0. 2.5 and 5 g L–1) and amino spot (0, 1 and 1.5 mL L–1). The crop was harvested in mid-May (First cutting) and mid-August (Second cutting). Growth and yield characters were measure. The essential oil percentage was determined in both cuts from fresh herb. The essential oil was analyzed by GC/Mass. It can be observed that, humic acid and/or amino spot fertilizer (Algae extract) had a significant effect on growth characters during both cuts. Increasing amino spot doses increased growth characters (plant height, herb fresh and dry weight) at all doses in the two cuts. The results show that there were clear significantly positive trend in increasing growth characters by spraying of humic acid. The interaction effect was significant in both cuts, the highest values of plant height, herb fresh and dry weight (g plant–1) were produced from the treatment sprayed with humic acid at 5 g L–1+amino spot at 1.5 mL L–1, followed by the treatment sprayed with 2.5 g L–1 humic acid+1.5 mL L–1 amino spot at the two cuts. During the 1st cut, humic acid or amino spot fertilizer had a significant effect on essential oil percentage and yield (mL plant–1) while, all treatments produced significant effect on oil percentage and oil yield (mL plant–1) except the interaction treatments, which had no significant effect on essential oil percentage during second cut. Linalool and linalyl acetate were the main constituents of essential oil of this plant. All treatments or cuttings had a pronounced effect on essential oil constituents. Based on the experimental results it is recommended to treat Mintha piperita var. citrata (Eau de Cologne mint) plants with humic acid at 5 g L–1+amino spot at 1.5 mL L–1 to produce high mass production and oil yield.

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S.F. Hendawy, M.S. Hussein, A.E. El-Gohary and M.E. Ibrahim, 2015. Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata. Asian Journal of Agricultural Research, 9: 237-248.

DOI: 10.3923/ajar.2015.237.248

URL: https://scialert.net/abstract/?doi=ajar.2015.237.248
 
Received: May 24, 2015; Accepted: July 28, 2015; Published: August 15, 2015



INTRODUCTION

Mint is a perennial plant and productive up to 15 years. Primarily, it is grown for oil production from its leaves. The life span of a commercial mint field is 3-5 years and mainly depends on genetic and environmental factors. Generally the growth, development and the quality of aromatic plants are affected by the genetic background, environment and cultivation practices as well as the processing and storage of plant tissues (Clark and Menary, 1980a, b). The concentrations of secondary metabolites such as essential oils in plants result from their continuous formation and breakdown during plant growth. Mentha piperita var. citrata is a fully hardy deciduous herb. It is best planted in moist but well drained soil and grows to an ultimate height of 0.1-0.5 m in 1-2 years. Eau de Cologne mint, like many other members of this genus, is often used as a domestic herbal remedy, being valued especially for its antiseptic properties and its beneficial effect on the digestion. Like other members of the genus, it is best not used by pregnant women because large doses can cause an abortion. The leaves and flowering plant are anodyne, antiseptic, antispasmodic, carminative, cholagogue, diaphoretic, refrigerant, stomachic, tonic and vasodilator. A tea made from the leaves has traditionally been used in the treatment of fevers, headaches, digestive disorders and various minor ailments. The medicinal uses of this herb are more akin to lavender (Lavandula spp.) than the mints. It is used to treat infertility, rapid heartbeat, nervous exhaustion etc. The leaves are harvested as the plant comes into flower and can be dried for later use. The essential oil in the leaves is antiseptic, though it is toxic in large doses. The highest content of essential oil (1%) was obtained at 120 days while, the highest content the majority compounds-fenchol (49.92%) and cis-myrtanol (30.03%) reached its highest value at 120 and 150 days after transplanting, respectively (De Oliveira et al., 2012). The total oil accumulation depends on the genetic composition of the plant and it varies between genera and species (Franz et al., 1984).

Plant nutrition is one of the most important factors that increase plant production. Nitrogen (N) is the most recognized in plant for its presence in the structure of the protein molecule. Accordingly, N plays an important role in synthesis of the plant constituents through the action of different enzymes (Jones et al., 1991). Nitrogen fertilization has been reported to reduce essential oil content in creeping juniper (Juniperus horizontalis) (Robert, 1986), although it has been reported to increase total essential oil yield in thyme (Thymus vulgaris L.) (Baranauskiene et al., 2003). Baranauskiene et al. (2003) found that N fertilizer increased herb yield, but essential oil content was not remarkable of thyme (Thymus vulgaris). Ashraf et al. (2006) showed that N fertilization had a significant increase in the oil content of black cumin (Nigella sativa L.) seeds. Phosphorous (P) plays an important role in various metabolic processes. It is a constituent of nucleic acid, phospholipids, the coenzymes, DNA and NADP and most importantly ATP. It activates coenzymes for amino acid production used in protein synthesis and it decomposes carbohydrate production in photosynthesis; as well as involved many other metabolic processes required normal growth, such as photosynthesis, glycolysis, respiration, fatty acid synthesis. Application of 100 kg ha–1 P significantly increased the fresh and dry weights in feverfew (Tanacetum parthenium L.) Schultz Bip) plant while, all P levels (50, 100 and 150 kg ha–1) as compared with the control significantly enhanced the EO concentration (Saharkhiz and Omidbaigi, 2008). Application of 50 kg P2O5 ha–1 significantly increased the total dry matter and EO yield in mint (Mentha longifolia) plant (Alsafar and Al-Hassan, 2009). The leaf biomass of garden sage (Salvia officinalis L.) and EO content increased with adding P fertilizer (Nell et al., 2009). Potassium (K) is one of the most important elements for plant nutrition, which content occupies 1-5% of crops’ dry matter, it plays a very important role in the growth, yield and quality of crops, K is involved in the activities of over 60 kinds of plant enzymes, potassium affects the metabolism of N and carbohydrates and the synthesis of lipid, starch and protein. Potassium also plays a very important role in substance transportation inside plants (Zahra et al., 1984). Adding K fertilizer increased herb, EO and its constituents in rue (R. graveolens L.) (Khalid et al., 2007). The highest peppermint (Mentha piperita) EO production was in K at 218 mg L–1 concentration (Mollafilabi et al., 2010). Addition of K at 123 kg ha–1 year–1 enhanced the total EO yield of palmarosa (Cymbopogon martini [Roxb.] Wats. var. Motia burk) plant by 23.7% in comparison to no K application (Singh, 2008). Potassium fertilization increased EO and anethole content of anise (Pimpinella anisum L.) plant (Al-Awak, 2010). Amino acids have traditionally been considered as precursors and constituents of proteins. Many amino acids also act as precursors of other nitrogen containing compounds, e.g., nucleic acids. Amino acids can play wide roles in plants including acting as regulatory and signaling molecules. Amino acids also affect synthesis and activity of some enzymes, gene expression and redox-homeostasis (Rai, 2002). Talaat and Youssef (2002) found a pronounced increase in vegetative growth of basil plant as a result of lysine and ornithine treatments. However, S-adenosyl-methionine play a role via the methyl group as a donor to produce estragole and t-anethole in cell-free extracts of the bitter fennel plant (Gross et al., 2002). Maxwell and Kieber (2004) indicated the link of methionine to the biosynthesis of growth regulating substances, e.g cytokinins, auxins and brassinosteroids in plants. Whereas, the link of tryptophan to the biosynthesis of auxins, the phytoalexin camalexin, phenylpropanoids and other related natural products in plants was recently reported (Tao et al., 2008). Humic acid provides numerous benefits to crop production. It has been reported to influence the plant growth both directly and indirectly. The indirect effects of humic acid compounds have been attributed to the improvement of physical, chemical and biological conditions of soil. It breaks up clay and compacted soils, assists in transferring micronutrients from the soil to the plant, enhances water retention, increases seed germination rates, improves nutrient absorption, plant growth and penetration and stimulates the development of microflora populations. The direct effects on plant growth is to the increase the cell chlorophyll content, the acceleration of the respiration process, hormonal growth responses, increasing substances penetration to plant membranes, affect the dry matter production and the uptake of nutrients by plants (Rao et al., 1987). Also, humic acid has positive effects on the promotion of root development. It increases the root/shoot ratio as well as the product ion of thin lateral roots of some plants (Tattini et al., 1990, 1991).

So far, there is no report on the yield and composition of the essential oil of Mentha piperita f. citrata plants cultivated under this experimental condition in literature. This study was carried out to evaluate the response of this variety to foliar fertilization under Egyptian conditions especially there is no enough data on this variety.

MATERIALS AND METHODS

The experiment was carried out on Mintha piperita var. citrata (Eau de Cologne mint) at Sekem experimental field during two successive seasons (2012 and 2013). The soil characteristics and nutrient concentration in soil of experiment (0-30 cm depth) were shown in Table 1. The experiment was laid out in Factorial Randomize Block Design (FRBD) with three replications. Fresh, healthy, insect and disease free suckers were transplanted in furrow at a depth of 4-5 cm as per the treatments.

Table 1: Physical and chemical properties of the soil
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata

Table 2: Guaranteed analysis and physical data of humic total
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata

Table 3: Some chemical properties of amino spot
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata

Three weeks later after transplanting, the plants were sprayed with aqueous solution of the test nutrient compounds, humic acid and amino spot. Foliar application was repeated after two weeks from 1st cut. Humic acid which produced by Leili Agrochemistry Co., LTD, China and its properties are shown in Table 2. Amino spot which is produced by Keymand Co. for Fertilizers and Chemical Industries-2nd Industrial Zone-El-Nobarya (Special formula abstracted from the algae which is very rich with-free amino acids and cytokinin+major elements as shown in Table 3).

Treatments which were carried out can be summarized as following:

Control (Foliar application with water)
Foliar application with humic acid at 2.5 g L–1
Foliar application with humic acid at 5 g L–1
Foliar application with amino spot at 1 cm L–1
Foliar application with amino spot at 1.5 cm L–1
Foliar application with humic acid at 2.5 g L–1+amino spot at1 cm L–1
Foliar application with humic acid at 2.5 g L–1+amino spot at 1.5 cm L–1
Foliar application with humic acid at 5 g L–1+amino spot at 1 cm L–1
Foliar application with humic acid at 5 g L–1+amino spot at 1.5 cm L–1

The crop was harvested in mid-May (First cutting) and mid-August (Second cutting). The data on plant growth, fresh and dry herb yield, oil content and oil yield were recorded at the each cutting. The extracted essential oil was dehydrated over anhydrous sodium sulphate and stored at freezer till used for gas chromatography-mass spectrometry (GC-MS) analysis.

Essential oil production: The percentages of volatile oil were determined in the fresh herb using 100 g samples for each cut per plant. Water distillation of the volatile oil according to Guenther (1961).

GC-MS analysis: The GC-Ms analysis of the essential oil samples was carried out in the second season using gas chromatography-mass spectrometry instrument stands at the Department of Medicinal and Aromatic Plants Research, National Research Center with the following specifications. Instrument: A TRACE GC Ultra Gas Chromatographs (THERMO Scientific Corp., USA), coupled with a THERMO mass spectrometer detector (ISQ Single Quadrupole Mass Spectrometer). The GC-MS system was equipped with a TG-WAX MS column (30 m×0.25 mm i.d., 0.25 μm film thickness). Analyses were carried out using helium as carrier gas at a flow rate of 1.0 mL min–1 and a split ratio of 1:10 using the following temperature program: 40°C for 1 min; rising at 4.0°C min–1 to 160°C and held for 6 min; rising at 6°C min–1 to 210°C and held for 1 min. The injector and detector were held at 210°C. Diluted samples (1:10 hexane, v/v) of 0.2 μL of the mixtures were always injected. Mass spectra were obtained by Electron Ionization (EI) at 70 eV, using a spectral range of m/z 40-450. Most of the compounds were identified using two different analytical methods: (a) KI, Kovats indices in reference to n-alkanes (C9-C22) and (b) mass spectra (authentic chemicals, Wiley spectral library collection and NSIT library).

Statistical analysis: Data was combined over the two seasons for statistical analysis. All recorded data was subjected to analysis of variance procedures and treatment means were compared using LSD at 5% described by Snedecor and Chochran (1980).

RESULTS AND DISCUSSION

Growth characters: Concerning variance analysis results in Table 4 and 5, it can be observed that, humic acid and/or amino spot fertilizer had a significant effect on growth characters during both cuts.

Data presented in Table 6 and 7 indicated that humic acid and/or amino spot fertilizer affected growth characters in both cuts.

Increasing amino spot doses increased growth characters (plant height, herb fresh and dry weight) at all doses in the two cuts. These doses had increased growth characters compared to the control treatment. Nitrogen, is the structural component of cell constituents and metabolically active element, helps in maintenance of energy transformation, enzyme action and improves quality of leafy crop. The beneficial effect of phosphorus in influencing herbage yield is due to its role in various metabolic activities of plant which might have resulted in increased herbage yield.

Table 4:Summary of analysis of variances for morphological traits and qualitative and quantitative yield of eau de cologne mint plant (1st cut) mean values of two successive seasons
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata
ns: Not significant, *Significant, **Moderate significant, ***Highest significant

Table 5:Summary of analysis of variances for morphological traits and qualitative and quantitative yield of eau de cologne mint plant (2nd cut) mean values of two successive seasons
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata
ns: Not significant, *Significant, **Moderate significant, ***Highest significant

Table 6:Effect of amino spot fertilizer and humic acid on yield characters and essential oil content of eau de cologne mint plant (1st cut) mean values of two successive seasons
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata
ns: Not significant, *Significant, **Moderate significant, ***Highest significant

Table 7: Effect of amino spot fertilizer and humic acid on yield characters and essential oil content of eau de cologne mint plant (2nd cut) mean values of two successive seasons
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata
ns: Not significant, *Significant, **Moderate significant, ***Highest significant

Phosphorus, also a structural component of nucleic acid, plays an important role in energy transfer and protein metabolism and potassium helps in osmotic and ionic regulation.

The results in Table 6 and 7 show that plant growth is a function of nutrients supply providing, there were clear significantly positive trend in increasing growth characters by spraying of humic acid. Similar results were reported by Zaghloul et al. (2009), they indicated that spraying Thuja orientalis plants with humic acid increased growth compared with control plants due to the direct effect of humic acid on solubilization and transport of nutrients. These results are in accordance with those obtained by Arancon et al. (2004) on marigolds, peppers and number of fruits of strawberries. Chen and Avaid (1990) added that humic substances have a very pronounced influence on the growth of plant roots and enhance root initiation and increased root growth which known root stimulator. Humic acid improve growth of plant foliage and roots. Vaughan (1974) proposed that humic acids may primarily increase root growth by increasing cell elongation or root cell membrane permeability, therefore increased water uptake by increased plant roots and added that it can produce root systems with increased branching and number of fine roots, as a result potentially increase nutrients uptake by increase root surface area (Rauthan and Schnitzer, 1981).

The interaction effect was significant in both cuts, the highest values of plant height, herb fresh and dry weight (g plant–1) were produced from the treatment sprayed with 1% humic acid at 5 g L–1+amino spot at 1.5 mL L–1, followed by the treatment sprayed with 2.5 g L–1 humic acid+1.5 mL L–1 amino spot at the two cuts.

For performing necessary physiological function to buildup different yield attributes these nutrients, inorganic and organic which have been integrated in present study were possibly responsible for synthesizing necessary enzymes, proteins, energy (ATP and NADP), chlorophyll and other for the translocation of photosynthates and perhaps only because of these factors.

Essential oil production: The ANOVA results indicated that, during the 1st cut, Humic acid or amino spot fertilizer had a significant effect on essential oil percentage and yield (mL plant–1), while all treatments produced significant effect on oil percentage and oil yield (mL plant–1) except the interaction treatments which had no significant effect on essential oil percentage during second cut.

The mean values of essential oils due to amino spot application at 1 and 1.5 mL L–1 increased in both cuts. Fertilization might enhance the essential oil biosynthesis processes through its direct or indirect role in plant metabolism resulting in more plant metabolites. These finding are in agreement with those of Omer (1998) and Omer et al. (2008), who said that nitrogen fertilizer was effective in increasing essential oil of Origanum syriacum and Ocimum americanum, respectively. Essential oil percent in mint fresh herb were significantly affected as a result of foliar application with humic acid (Table 6 and 7). Zaghloul et al. (2009) reported that humate application lead to increase oil content in Thuja orientalis.

From the above mentioned results, it could be concluded that foliar application of humic acid promoted growth and possessed the best oil percentage in mint plant.

Generally, the maximum essential oil content (%) was observed in the fresh herb of plants that sprayed with 5 g L–1 humic acid and 1.5 mL L–1 in the two cuts.

The oil yield of mint (mL plant–1) was affected by foliar application of humic acid and/or amino spot in both cuts. The higher the dose of amino spot, the higher was the oil yield. The response of volatile oil content to amino spot fertilization might be attributed to de novo meristemic cell metabolism in building dry matter with essential oil production. These results agree with those of Omer (1998) and Omer et al. (2008), who found a positive correlation between fertilizer and essential oil content in herbage of Origanum syriacum and Ocimum americanum, respectively in all cuttings. In addition, spraying mint plants with humic acid caused an increase in the essential oil yield (Table 6 and 7). Generally, the highest essential oil yield (mL plant–1) was obtained from plants sprayed with amino spot at 1.5 mL L–1 and humic acid at 5 g L–1 in both cuts.

Essential oil constituents: The essential oil composition varies according to cuts and/or different treatments and was characterized by high percentage of oxygenated compounds ranged from 61.07-79.96% in the 1st cut and from 71.43-84.27 in the second one. The components of essential oil in herb for different treatments during two cuts were shown in Table 8 and 9. The identified components ranged from 28-30 in the 1st cut and from 27-30 in the 2nd one representing about 96.14-100% as a result of different treatments during both cuts.

Table 8:Essential oil constituents of eau de Cologne mint plant as affected by amino spot fertilizer and humic acid (1st cut of the 2nd season)
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata
1: Control (Foliar application with water), 2: Foliar application with humic acid at 2.5 g L–1, 3: Foliar application with humic acid at 5 g L–1, 4: Foliar application with amino spot at 1 cm L–1, 5: Foliar application with amino spot at 1.5 cm L–1, 6: Foliar application with humic acid at 2.5 g L–1+amino spot at 1 cm L–1, 7: Foliar application with humic acid at 2.5 g L–1+amino spot at 1.5 cm L–1, 8: Foliar application with humic acid at 5 g L–1+amino spot at 1 cm L-–1, 9: Foliar application with humic acid at5 g L–1+amino spot at 1.5 cm L–1

Table 9:Essential oil constituents of eau de Cologne mint plant as affected by amino spot fertilizer and humic acid (2nd cut of the 2nd season)
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata
1: Control (Foliar application with water), 2: Foliar application with humic acid at 2.5 g L–1, 3: Foliar application with humic acid at 5 g L–1, 4: Foliar application with amino spot at 1 cm L–1, 5: Foliar application with amino spot at 1.5 cm L–1, 6: Foliar application with humic acid at 2.5 g L–1+amino spot at 1 cm L–1, 7: Foliar application with humic acid at 2.5 g L–1+amino spot at 1.5 cm L–1, 8: Foliar application with humic acid at 5 g L–1+amino spot at 1 cm L–1, 9: Foliar application with humic acid at 5 g L–1+amino spot at 1.5 cm L–1

L. Linalool was identified as the major compound in the different treatments ranging from 14.68-23.51% in the 1st cut and from 12.67-25.23% in the 2nd one. Linalyl acetate, the second main component, ranged from 12.49-26.37% and from 8.08-16.71% in the 1st and 2nd cuts, respectively. In the oil of the 1st cut, the third main component was eucalyptol which ranged from 4.93-7.72% followed by β-Fenchyl alcohol which ranged from 4.16-6.56%. On the other hand, the third main component in the 2nd cut was caryophyllene which ranged from 5.08-12.14% followed by β-Fenchyl alcohol (6.11-8.94%). In this respect, chemical composition of essential oil of mint herb is very variable depending on the habitat and climate.

Table 10: Regression analysis and correlation coefficient of the relation between fertilizers treatments and mint characters (1st cut)
 
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata

Table 11: Regression analysis and correlation coefficient of the relation between fertilizers treatments and mint characters (2nd cut)
Image for - Effect of Foliar Organic Fertilization on the Growth, Yield and Oil Content of Mentha piperita var. citrata

In the 1st cut untreated plants produced the maximum value of linalool (23.51%) followed by foliar application treatment with amino spot at 1.5 cm L–1, which gave 21.09. The highest value of linalyl acetate (28.15%) as a result of foliar application with humic acid at 5 g L–1 followed by foliar application with humic acid at 2.5 g L–1+amino spot at1 cm L–1, which gave 26.37%. In the 2nd cut linalool reached to its maximum value (25.23%) as a result of foliar application with humic acid at 2.5 g L–1 followed by foliar application with humic acid at 5 g L–1 which gave (23.56%). On the other hand, foliar application with humic acid at the 2.5 g L–1 produced the highest relative percentage (16.71%) followed by untreated plants which gave (16.50%). The effect of different treatments on EO yield and constituents may be due to their effect(s) on enzyme activity and metabolism of EO production. It is already known that fertilizers affect the growth and essential oil synthesis in medicinal plants. These components influence the levels of enzymes that are very important in the biosynthesis of important terpenoides.

Regression analysis and correlation coefficient of the relation between fertilizers treatments and mint characters: Results of the regression analysis of the relation between growth characters, essential oil percentage and essential oil yield of mint and all fertilizers treatments are presented in Table 10 and 11. The regression coefficients of all characters were significant at p≤0.0001 and had the positive trend. The adjusted determination coefficients ranged from 0.470 for herb fresh weight to 0.848 for essential oil percentage for the 1st cut while, it ranged from 0.497 for herb fresh weight to 0.662 for 2nd cut.

As, a conclusion from this regression analysis that as fertilizer increased, essential oil percentage increased by 0.006 and 0.004% as well as essential oil yield by 0.004 and 0.010% increased during 1st and 2nd cuts, respectively.

Moreover, data in Table 10 and 11 clear that, there are positive relationship between fertilizers treatments and different characters under study. The correlation coefficient values ranged from 0.67 for herb dry weight to 0.92 for essential oil percentage and from 0.70 for herb fresh weight to 0.81 for herb dry weight and essential oil yield during 1st and 2nd cuts, respectively.

These results showed the positive effect of fertilizer treatments on growth characters and essential oil content.

CONCLUSION

From the above mentioned results, it could be concluded that foliar application of humic acid and/or amino acids promoted growth and possessed the best oil percentage and yield in mint plant. Based on the experimental results it is recommended to treat Mintha piperita var. citrata (Eau de Cologne mint) plants with humic acid at 5 g L–1+amino spot at 1.5 mL L–1 to produce high mass production and oil yield.

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