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, measured on analytical scale, and kept in a freezer at –5 °C until all distillations were finished. The essential oil content (yield) was calculated by weight, as grams of oil per 100 g of fresh herbage, and expressed as percentage of oil in the fresh

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Essential oils were extracted from leaves, flowers, and stems of Ocimum basilicurn, O. kilimandscharicum, and O. micranthum by solvent extraction, hydrodistillation, and steam distillation for essential oil content and the oil analyzed by GC and GC/MS for composition. While the yield of essential oil was consistently higher from steam distillation than hydrodistillation, a similar number of compounds was recovered from both hydrodistillation and steam distillation. Though the relative concentration of the major constituents was similar by both methods, the absolute amounts were higher with steam distillation. Essential oil content and composition varied by plant species and plant part. Essential oil content was highest in flowers for O. basilicum and in leaves for O. micranthum. No significant differences were observed in essential oil yield and relative concentration of major constituents using fresh or dry samples and using samples from 75 g to 10 g of dry plant tissue. While minor differences between hydrodistillation and steam distillation were observed, both methods resulted in high yields and good recovery of essential oil constituents. Hydrodistillation is a more-rapid and simpler technique than steam and permits the extraction of essential oil where steam is not accessible.

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Abstract

Sweet basil (Ocimum basilicum L.) plants were grown, until flower buds became visible, in a peat-lite mix and watered daily with a complete nutrient solution with 10 mm N as either NO 3 or NH 4 + . Ammonium decreased plant height and stem plus petiole dry weight. Leaf blade dry weight was not affected by N form. However, the essential oil content was decreased by 28% with NH 4 + , thereby decreasing the essential oil yield per plant. Although NH 4 + decreased the content (nl·g-1 leaf blade dry weight) of linalool and eugenol, their percentage was not altered. Therefore, the changes in total yield of these individual constituents was simply a reflection of less total extractable essential oil. The total amount of the other major constituents in sweet basil, 1,8-cineole, methyl chavicol, and total sesquiterpenes was not affected significantly. While N form did not alter the percentage of monoterpenes and aromatic polypropa-noides, NH 4 + -N increased the total sesquiterpene percentage. Nitrogen form altered the essential oil content and composition of sweet basil and, therefore, should be considered in nutritional studies with aromatic plants.

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Plants of rosemary [Rosmarinus officinalis L. (Lamiaceae)] were grown in pots containing a soilless (1 sphagnum peat:1 perlite) or soil-based (1 sphagnum peat: 1 perlite:1 field soil) growing medium and fertilized with either 12N-5.2P-12.5K controlled-release fertilizer (CRF) at 9.0 g/pot; constant liquid fertilization (LF) with 20N4.3P-16.7K at 150 mg N/liter; constant LF at 150 mg N/liter, plus CRF at 4.5 g/pot; weekly LF at 150 mg N/liter; or weekly LF at 150 mg N/liter, plus CRF at 4.5 g/pot. Constant LF plus CRF generally reduced plant height and depressed shoot fresh weight relative to other fertilizer regimes. Essential oil content was highest in plants receiving weekly LF. Plants grown in the soil-based mix were shorter, shoot fresh and dry weight tended to be lower, and essential oil yield was higher when compared to plants grown in the soilless mix. Satisfactory growth was obtained in both media when rosemary plants were fertilized with 12N-5.2P-12.5K CRF at 9.0 g/pot or weekly LF with 20N<.3P-16.7K at 150 mg N/liter.

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. Similarly, Simon et al. (1992) reported that moderate water stress imposed on sweet basil resulted in higher oil content and greater total oil yield. Furthermore, the authors indicated that water stress changed essential oil composition: water stress

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; MIRC, 2009 ). If the distillation wastewater from an aromatic crop is shown to have growth-promoting effects on peppermint and spearmint or improve their essential oil content, such an extract could be applied to large-scale production systems, bringing

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increase carvone concentration of ‘Scotch’ spearmint ( Zheljazkov and Astatkie, 2011a ). In another study, the application of MJ had no significant effect on essential oil content of ‘Native’ spearmint ( Zheljazkov et al., 2010b ). In the same study, the

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, 1973 ). Like with other aromatic plants, A. annua essential oil content and composition is modified by genotype and the environment ( Tzenkova et al., 2010 ), by distillation method ( Scheffer, 1993 ), and by other factors. A recent report ( Ferreira

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still expanding ( Croteau et al., 1981 ). Research on Cistus ladanifer showed that young leaves produce more flavonoids and diterpenes ( Masa et al., 2016 ). Thus, leaf age is an important factor affecting essential oil content and composition

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essential oil production is at flowering, when the oil content and preferred composition are the highest ( Topalov, 1962 ; Zheljazkov, 1998 ). Various basil species and cultivars provide essential oil with different compositions and aroma. The

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