Biomass production, essential oil yield and composition of Mentha x piperita L. Deschamps, C. I ; Machado, M. I ; Bizzo, H.
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Physiological indexese macro- and micronutrients in plant tissue and essential oil of Mentha piperita L. David, E. II ; Marques, M. III ; Boaro, C. Mentha piperita L. This study aimed to evaluate physiological indexes, macro- and micronutrients inthe shootsand essential oil of Mentha piperita L. Shoot length, dry mass of the different organs, total dry mass, leaf area, essential oil yield and composition, and macronutrient N, P, K, Mg, Ca, S and micronutrient Mn, Cu, Fe, Zn contents in the shoot were evaluated.
This solution had better development compared to the other tested treatments. Therefore,we recommend Mentha piperita L. Keywords: Lamiaceae, menthol,hydroponics and nutrition. Recomenda-se, portanto, o cultivo da Mentha piperita L. Commonly known as mint or peppermint, Mentha piperita L.
The plants of this family have been extensively studied from an agronomical and chemical point of view due to their richness in essential oils, and the aims of these studies have been not only to maximize their essential oil content, but also to assess the variation in their oil compounds Martins, , which may completely change the oil quality. The essential oil is originated in the secondary metabolism of the plant; however, the compounds of this pathway depend on the primary metabolism.
Thus, plant productivity, which reflects the primary metabolism and it is determined by biomass gain, depends on leaf quantity, photosynthetic capacity of each leaf and nutrient availability. The suitable supply of mineral nutrients for the culture is one of the most important factors to increase productivity Fageria et al.
Thus, aromatic plants developed in hydroponics, with all nutrients available, had higher productivity and accumulated from 3 to 6-fold more essential oil per area, relative to plants grown using the traditional method Mairapetyan, Essential oil content can usually be increased with no need of additional production costs; therefore, appropriate propagation and cultivation forms that provide better oil yield have been the object of a number of studies Martins, Chemical and physical variations in the compounds of mint essential oil may occur since it is a mixture of compounds of different natures accumulated by the plant at specific rates.
Thus, the content of the substances present in the oil is highly dependent on environmental factors, and plants developed under different conditions may contain oils with different characteristics Maia, The qualitative and quantitative composition of the oil from medicinal plants may vary during the growth phases Castro et al. Several studies have shown the importance of mineral nutrition in the development of species of the family Lamiaceae and the content and composition of their essential oil.
Some researchers have evaluated M. Those authors noted that, regardless of the studied nutrient, its variation in the nutrient solution frequently interferes with the species development and oil yield by decreasing or increasing the oil content and varying its composition.
As the secondary metabolism, oil synthesis depends on compounds synthesized in the primary metabolism and plant productivity is determined by the quantity of leaves and their photosynthetic capacity, as well as nutrient availability, which are key factors for biomass gain.
Milthorpe and Moorby stated that the deficiency of a nutrient interferes with the final production, although the intermediate physiological variables that are compromised remain not fully understood Marschner, The efficiency of plants in obtaining a nutrient at a quantity sufficient for their growth depends not only on the available level of this element in the nutrient medium, but also on external factors associated with the environmental and physiological factors affecting absorption Epstein and Bloom, Among these external factors are the element itself and its level relative to the other elements in the substrate.
Studies have emphasized the importance of nutrient balance in the medium and have frequently reported interactions between nutrients which may be harmful to the plants. Thus, unbalanced concentrations of nutrients reciprocally influence their availability, uptake and transport in the plant Marschner, In addition to nutrient availability, the appropriate elemental ratio must be considered to ensure optimal plant growth Marenco et al.
Over the years, several formulations have been employed in nutrient solutions and that of Hoagland and Arnon contains all mineral elements known to be necessary for the rapid growth of plants. These elements are established at the highest allowed levels, without causing symptoms of toxicity or salt stress Zeiger, To obtain a product of higher quality, Leal, ; David et al.
Based on the results obtained in the above-mentioned studies and considering that nutrient solution of Hoagland and Arnon number 2 overestimates the content of macronutrients, modifications were done to establish the different treatments evaluated in the present study.
The modified nutrient solution with variation in the level of macronutrients N, P, K and Mg and their relationship were used for M.
Aerial branches of these plants were selected to prepare 10 cm-length apical cuttings with the first four leaves pairs. The nutrient solution, continuously aerated using a rotary blower, was renewed at every two weeks. Whenever needed, the solution volume in the pots was completed with water. Experimental design was a completely randomized, with four replicates, with one plant each, in a 4 x 5 factorial scheme, i. For the essential oil, the design was completely randomized with four replicates in 4 x 4 factorial arrangements, i.
The variables length, leaf area, dry mass of several organs and total dry mass had heterogeneous variance among treatments; thus, weighted regression analysis and log-transformation of the results were used for analysis of variance. In all harvests, the plants had their shoot length measured and the leaf area of all their leaves determined, according to David et al.
When completely dried, the material was weighed for dry mass determination. Leaf blades and stems plus petioles were ground to prepare the extracts according to Malavolta et al. On the third day, the dry mass was determined through hydrodistillation in Clevenger-type. After extraction, essential oil yield was calculated based on the difference between the final and the initial mass of the flask.
As this difference corresponded to the oil extracted from 30 g shoot dry mass, the yield was estimated for g of its mass. However, these slight increases did not result in higher dry mass yields or essential oil Figure 2c and Table 1. These plants had lower Mg content in the leaves blade Table 4 and stems plus petioles, Table 5 , with no signs of Mg deficiency. It suggests that despite the decrease of Mg, even in the lowest concentration tested in the nutrient solution, plants had enough of this element to supply its metabolic demands.
Although it is possible to occur substitution of Mg by other elements in some metabolic processes, it is indispensable in several stages of photosynthesis, with a role related to conversion and maintenance of energy, and regulation effect upon Calvin cycle enzymes Epstein and Bloom, The hypothesis that the lowest concentration of Mg tested supplied the metabolic demands is confirmed by the assessment of CO 2 assimilation rate, when this treatment was related to higher assimilation Figure 3.
The present results agree in part with those obtained by Valmorbida et al. These results also corroborate those of Valmorbida et al. It must be emphasized, however, that in the present study the reductions were simultaneous for N, P and K, whereas in the remaining studies the reduction was for only one of the minerals.
Santos et al. These plants absorbed smaller quantity of K and larger quantity of Mg, which can be confirmed by the levels of these nutrients in the leaf blades and stems plus petioles Tables 2 and 3. These results show the interaction between K and Mg, which compete by the root binding sites during absorption Marschner, When an ion is in a higher concentration than another, competition causes decline on absorption rate of the latter.
In the present study, higher concentration of Mg probably caused decrease on K absorption, without differences on CO 2 assimilation Figure 3. However, these plants that showed no great differences in CO 2 assimilation, revealed adequated exports from leaves to branches and petioles, as demonstrated by the evaluation of leaf mass ratio, and confirmed by the distribution of dry mass of branches and petioles David and Boaro, Then, the amount of this nutrient offered was adequate, once these plants showed normal growth, with no interference in the translocation of carbohidrates to other organs.
These plants showed higher average yield of essential oil during its cycle Table 1 , showing that secondary metabolism depends on primary metabolism, since oil producing glands are carbon consumers and relies on adjacent photosynthetic cells for the suplly of these precursors Croteau and Johnson, Thus, the decreased N, P, K and Mg levels in these plants did not damage their physiological functions and were satisfactory to the plant growth, essential oil yield and quality of M.
In all treatments evaluated, major compounds of essential oil were menthol and menthone. Biosynthesis of menthol follows a series of metabolic pathways, under the action of enzymes responsible by its production Maia, This conversion is a slow process and is associated to plant maturation and nutrition Murray et al.
The environmental conditions can redirect metabolic pathways, affecting biosynthesis of several compounds Moraes, Nutrition is one of the external factors that can affect qualitatively and quantitatively the production of some secondary metabolites Lima et al. Although for M.
These variations may be associated with a greater leaf development and the emergence of new organs, concomitant to a steady content of secondary metabolites Gobbo-Neto e Lopes, Mineral nutrition influences Carbon metabolism directly and indirectly, because of its influence on growth and morphogenesis. Nitrogen affects positively biomass production, because of several physiological factors that contributes to synthesis of carbohidrates, aminoacids and nucleic acids Maia, This element in linked to photosythesis metabolism and its equilibrium is essential for all steps of Calvin-Benson cycle Salisbury Ross, ; Lawlor, Phosphorus is incorporated to several organic compounds such as pentose-phosphates, fosfolipids, and nucleotides Malavolta ,; Zeiger, ; Marschner, It also plays important roles in the regulation of Calvin-Benson cycle and transport of metabolites and assimilated compounds Larcher, Potassium activates enzymatic reactions such as P-transferase, acetate-kinase, piruvate-kinase, and hydrolysis reactions.
It also promotes synthesis of ribulose-biphosphate-carboxilase, which affects CO 2 assimilation. It is essential for activation of ATPase that is needed for the exchange of nutrients and metabolites among apoplasts and simplasts Wilkinson, Magnesium has specific roles on activation o enzymes related to respiration, DNA and RNA synthesis and in photosynthesis, as a component of chlorophyll molecule Hinkle and Eisennenger, ; Zeiger, All nutrient functions referred here are related to primary metabolism, but secondary metabolism may also be affected directly by the role of these nutrients upon enzymes of the mevalonic acid pathway and terpenoids production Zeiger, Leal , Valmorbida et al.
The results found in those studies and in the present study showed the influence of mineral nutrition on the production and composition of M. Piperita essential oil. As shown in Table 5 , regardless of the treatment to which M. These results agree with those of Lima and Mollam and Leal , who grew M. Plants grown with the complete level of nutrients, i. The highest level of these nutrients seems to have damaged plant growth, delaying the cycle, as shown in Figures 1 a-c and Figures 2 a-c.
Ruiz reported that the nutrient solution number 2 of Hoagland and Arnon overestimates all nutrients used in its composition. According to Zeiger , the elements in that solution were established at the highest level that do not produce symptoms of toxicity or salt stress; therefore, these levels may be several fold higher than those found in the soil surrounding the roots.
In conclusion, considering that this solution is not specific for M. Biosynthesis of terpenoids in glandular trichomes. Biology and chemistry of plant trichomes. Plenum Press, New York, Revista Brasileira de Plantas medicinais. Revista Braileira de Plantas Medicinais.
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