The Asteraceae family, also known as Compositae, has over 23,500 species distributed in some 1,600 genera making it the biologically richest and most diverse angiosperm family. Within this family, the
Essential oils are a product of plant secondary metabolism, which can be regulated by environmental stimuli. Two of the important factors that can regulate plant metabolism (due to their lack or excess) are nitrogen and light quality (Rehman et al., 2016), which consequently influence the synthesis of active compounds. Indeed, N deficiencies and excessive light are a common combination of stress factors that plants have to face under natural conditions. When exposed to high light intensity environments, plants can exhibit symptoms, such as chlorophyll degradation and growth inhibition, which are the result of secondary oxidative stress derived from an overload of the photosynthetic apparatus (Cohen et al., 2019). The adverse effect of combining low nitrogen fertilisations with high light intensity conditions (i.e. potentially acute photodamage) is inevitably reflected in a reduction in growth and productivity (Cohen et al., 2019). Thus, light and N fertilisers influence growth and development of plants, and each plant species may display particular responses to fluctuations in light intensities, while a balanced nutrient supply tends to favour plant development (De Oliveira et al., 2019). Optimal nitrogen dosage for plant growth in high irradiance is lower than that in low irradiance because the ratio of ribulose 1,5-bisphosphate carboxylase (RuBP-case) activity to electron transport/photophosphorylation activity decreases with the increase of irradiance (Fu et al., 2017).
Nitrogen (N) plays an important role in plant growth and development (Scott, 2008). This element is a constituent of proteins, nucleic acids and nucleotides that are essential for the metabolic function of plants (Marschner, 2012). It is also vital in cell development and cell division, biosynthesis of essential oils and the active ingredient of medicinal plants (Rahmani et al., 2012). Therefore, nitrogen nutrition can significantly affect essential oil biosynthesis (Khalid, 2013).
Light affects nitrate absorption by stimulating the activity of transporters, and at the same time, the enzyme nitrate reductase affects photosynthesis and plant growth. If photosynthesis is altered by changes in light intensity, nitrate absorption must also change to maintain the supply of N at the necessary rate. Contrarily, if nitrate absorption is altered, the photosynthetic rate must be recovered. Importantly, both light and nutrient availability regulate the expression of genes involved in N assimilation (Kaiser and Huber, 2001).
Light intensity may differentially affect the yield of essential oils among plant genotypes. The species
In general, plants often adapt leaf metabolism and biomass allocation pattern in response to light and nutrient availability (Sugiura and Tateno, 2011). For instance, light intensity and N fertilisation influence the nitrate uptake from the root zone and its assimilation in upperparts. In lettuce (
The experiment was carried out under greenhouse conditions (Table 1). Thirty-day-old marigold (
Mean temperature, relative humidity and light intensity recorded in the greenhouse during the performance of the study aimed at evaluating the effect of three levels of nitrogen and two percentages of shading during the flowering of marigold (
Shading (%) | Temperature (°C) | Relative humidity (%) | Light intensity (μmol · m−2 · s−1) |
---|---|---|---|
0 | 19.3 | 59.5 | 680 |
70 | 21.0 | 53.3 | 207 |
Two study factors at different levels were tested. The study factors were the N concentration in the nutrient solution at three levels (8.47, 12.71 and 16.94 mg · L−1) and the shading percentage at two levels (0 and 70%). The N levels were established considering that the high level (16.94 mg · L−1) is sufficient for this species in an open hydroponic system (free drainage) with daily nutrient supply. The shading percentage resulted from using or not a black 70% UV light duty screening shade cloth. The mean light intensities corresponding to the shading percentages of 0 and 70% were 680 and 207 μmol · m−2 · s−1, respectively (Table 1). Black shade cloth is commonly used in horticulture since it efficiently reduces photosynthetically active radiation (Stamps, 2009). Consequently, the experiment had a 3 × 2 factorial arrangement with a completely randomised distribution of treatments in the greenhouse. Treatments were applied during the flowering stage of marigold plants. One day after transplantation (31-day-old plants), the flower buds of plants were removed from all the plants since these were formed when the plants had not received the treatments yet. Each treatment had 40 replicates. The experimental unit was a single pot with a single plant.
The following morphological variables were measured 30 days after the beginning of treatments (dat). The height of side branches (HSB) was determined from the visible base of the aerial part of the plant to the apex of lateral branches, containing the flower buds, using a graduated flexometer. The number of primary branches (NPB) and number of secondary branches (NSB) of the plant were quantified. The number of opened flower buds (NOFB) per plant was also evaluated. The diameter of flower (DF) was measured with a digital vernier calliper.
Isolation of the essential oil was done 38 days after the beginning of the treatments. Four plants in the flowering stage were randomly sampled per treatment. The plants were separated into flowers, leaves and stems. Once separated, the samples were dried in a hot air stove (Felisa, FE291AD; Guadalajara, Mexico) at 40°C for 48 h according to Babatunde et al. (2017). The dried material was ground, and each plant organ was processed separately. Essential oil extraction was performed according to the method described by Bowman et al. (1997) with some modifications. From each sample, 0.125 g were weighed, and the material was placed in a vacuum flask with a glass stopper and 2.5 mL dichloromethane was added. The flask was connected to a vacuum system and allowed to stand for 24 h. The samples were filtered, and the obtained extracts were kept in amber-coloured bottles at −20°C. Subsequently, the extracts were concentrated at 0.5 mL with a gentle stream of chromatographic grade nitrogen gas.
To identify the compounds, a gas chromatography/mass spectrometry (GC-MS) instrument was used, with a Hewlett Packard HP-6890 Series® (Agilent, Santa Clara, CA, USA) GC coupled to an HP-5973 mass detector. The gasified extract was run through an HP-5MS column (length 30 m, ID 0.250 mm, film 0.25 μm), with a mean speed of 36 cm · s−1. The operation conditions of the chromatograph were initial temperature 40°C for 5 min, first ramp-up to 150°C, with an increase of 9°C · min−1. This was maintained for 3 min; second ramp-up to 220°C with an increase of 9°C · min−1; the ion trap at 230°C, with a quadrupole at 150ºC; splitless injector mode, the temperature at 220°C, 6.97 psi. The gas carrier at 99.9% purity was helium and 1 μL of the concentrated samples was injected manually. Identification of terpenoids was performed by retention times and comparing mass spectra using the NIST database of the US National Institute of Standards and Technology (NIST/EPA/NIH, 2002) according to Adams (2007).
A one-way analysis of variance (ANOVA) was carried out to analyse the morphological data and components of the essential oil. When statistical differences were found, the mean separation was done by using the Tukey test with
Nitrogen had significant effects on the variables NSB and DF, while shading influenced HSB, NPB and number of opened flower buds. The interaction of the study factors was significant on all morphological variables evaluated 30 dat (Table 2).
Statistical significance of study factors and their interaction on the morphological variables of marigold (
Source of variation | HSB | NPB | NSB | NOFB | DF |
---|---|---|---|---|---|
Nitrogen (N) | 0.1490 ns | 0.0540 ns | <0.0001* | 0.9253 ns | 0.0005* |
Shading (S) | <0.0001* | 0.0052* | 0.9779 ns | <0.0001* | 0.1602 ns |
N × S | 0.0494* | 0.0463* | 0.0030* | <0.0001* | 0.0037* |
significant and no significant (ns) (Tukey,
DF, diameter of flower; HSB, height of side branches; NOFB, number of opened flower buds; NPB, number of primary branches; NSB, number of secondary branches.
The N level in the nutrient solution was positively associated with the NSB (Figure 1A), which increased to 65.9 and 123.9% with the concentrations of 12.71 and 16.94 mg · L−1 N, respectively, in comparison with the lowest level of N (8.47 mg · L−1 N). Likewise, the DF increased to 1.2 and 5.9% with medium and high levels of N, as compared with the low level of N (Figure 1B).
Quality and quantity of flowers are greatly influenced by climatic, geographical and nutritional factors. Proper fertilisation is of paramount importance for growth and development of plants as well as for a good quality of flower production in marigold (Priyadarshini et al., 2018). In this research, higher N levels stimulated the growth of secondary branches and flower diameter. These responses may result from a more efficient nutrients flow into the plants, which consequently may enhance plant growth and emergence of auxiliary buds. The easy uptake of nutrient and simultaneous transport of growth-promoting substances to the auxiliary buds may stimulate a breakage of apical dominance and thus a faster mobilisation of photosynthates and early transition of the plant from vegetative to reproductive phase (Priyadarshini et al., 2018). In China aster (
Shading reduced the HSB by 4.1% (Figure 2A), the NPB by 5.4% (Figure 2B) and the NOFB by 23.3% (Figure 2C), as compared with plants without shading. Shading is a common agricultural practice aimed to reduce heat stress in the summer. However, inappropriate shading decreases photosynthesis and consequently reduces plant growth (Qiu et al., 2018). Branching results from several interrelated processes: axillary bud formation, dormancy induction and release, bud outgrowth (involving the growth of preformed leaves), internode extension and initiation of new leaf primordia by the shoot apical meristem and then shoot extension (Leduc et al., 2014). Both endogenous (i.e. autonomous) and environmental (i.e. non-autonomous) pathways regulate the transition from vegetative to reproductive stages. Endogenous pathways function independently of environmental pathways and their inputs to flowering induction vary among, and even within, species (Amasino and Michaels, 2010). Importantly, environmental signals leading to floral transition include light, sucrose, cytokinins, gibberellins and reduced N compounds that are translocated in the phloem sap from leaves to the shoot apical meristem. Endogenous signals controlling flowering time function in cascades within four promotive pathways, all of which converge on the integrator genes
Shading not only reduces radiation but also increases the fraction of diffuse light and alters the spectral quality. Diffuse light is utilised more efficiently by plants and can produce small decreases in direct radiation and enhance leaf CO2 uptake, photosynthesis and growth. With increasing shading, the fraction of blue light (400–500 nm) increases while that of red light (600–700 nm) decreases, which may affect both physiological parameters (e.g. photosynthesis and chlorophyll biosynthesis) as well as plant morphology (Li et al., 2010). Plant species differ in their responses to light quality, but red and blue lights generally have the strongest effects on plant growth. Stomata regulate gas exchange and water loss in plants. Their opening and closure are influenced by many environmental factors, including light, CO2, and temperature (Ye et al., 2017). Among all these factors, light is the main environmental signal that controls stomatal movement. Usually, stomata are open in the light and closed in the dark. Occurring in all green tissues, chlorophyll is one of the most important pigments in higher plants, responsible for capturing light for photosynthesis. Therefore, chlorophyll is a key player in the interaction with light during the entire life cycle of plants (Ye et al., 2017), and photoreceptors such as phytochromes may mediate the regulation of chlorophyll biosynthesis (Inagaki et al., 2015). Based on the wide distribution of light-harvesting pigments and photoreceptors in various plant organs, buds will contain all photoreceptor types, thus affecting plant responses to light (Leduc et al., 2014). Furthermore, phytohormones are also affected by phytochromes, and thus they participate in the regulation of stem elongation and shoot branching (Krishna-Reddy and Finlayson, 2014; Lymperopoulos et al., 2018).
The highest HSB was recorded in plants treated with the medium dose of N and no shading; it was 7.1 and 6.6% higher than those found in plants exposed to shading receiving medium and low N doses (Figure 3A). The NPB in the treatments with medium dose of N was influenced by the light intensity; a 12% reduction in this variable in shaded plants was observed, compared with unshaded plants (Figure 3B). The NSB was positively related to the N dose in the nutrient solution (Figure 3C).
Nitrogen concentration in plant tissues often decreases in both elevated concentrations of CO2 and low nutrient availability, whereas it increases in low light environments (Bernacchi et al., 2007). The adverse effects of over-illumination can be aggravated by N limitation since the shortage of this nutrient can disrupt protein synthesis and impair the capacity of chloroplast proteins involved in the photosynthetic electron transfer chain and carbon assimilation. Lower photosynthetic capacity results in an excess of electrons in the thylakoid membrane and limitation of electron acceptors on the PSI side, which in turn stimulates the formation of reactive oxygen species (Cohen et al., 2019). Under N-deficient conditions, a limited sink development might induce downregulation feedback of the photosynthetic machinery and, ultimately, growth inhibition. Nitrogen uptake may be regulated by shoot-borne light signals, resulting in the upregulation of root N transporters and, ultimately, in an additional increase in N uptake (Cohen et al., 2019). Excessive N supply under high light intensity has adverse effects on plant growth (Fu et al., 2017).
On average, the NOFB was 32.3% higher in plants without shading than in plants with shading, independent of the N level in the nutrient solution. Opened flower buds of plants with low N level were more affected by shading, with 39% reductions as compared with the same N level without shading (Figure 4A). Flowers of plants without shading and high N level exhibited the higher diameter, surpassing in 9.5 and 6.1% DF with shade and medium level of N, and plants without shading and with low levels of N, respectively (Figure 4B).
Apart from N supply and light intensity, stress conditions such as heat, salt and UV light can promote flowering (Lin and Tsay, 2017). Moreover, the capacity of plants to develop new sink organs also depends on photosynthesis and N availability.
In calendula (
In this study, a slight increase of 1.7% in the DF in shaded plants was observed, with respect to plants without shade (Figure 4B).
Fifteen different compounds were identified in the plant organs of
Chemical compounds of the essential oil of leaves, flowers, and stems of marigold (
Compound | RT (min) | Compound | RT (min) |
---|---|---|---|
12.24 | 26.99 | ||
Ocimene | 12.64 | Terpinolene | 13.40 |
Caryophyllene | 19.36 | Piperitone | 16.60 |
Sabinene | 10.94 | γ-elemene | 21.27 |
Carene | 13.34 | Spathulenol | 23.25 |
β-phellandrene | 10.94 | Verbenone | 24.32 |
β-myrcene | 11.36 | β-farnesene | 20.03 |
α-pinene | 10.00 |
RT, retention time.
The compound content and amount in the essential oils are affected by factors such as the environment where the plant grows (Karousou et al., 2005), its phenological stage, the different parts from where the oils are extracted, the composition of the soil and mineral fertilisation (Fischer, 1991). Therefore, it is common to find differences even among plants of the same species. In some Mexican species of this genus, such as
Despite variations in the relative concentrations, the main constituents of
In this research, the main effects of the study factors (nitrogen and shading) and their interactions were significant in almost all the components studied, as observed in Table 4.
Statistical significance of the study factors and their interaction on the components of essential oil of leaves, flowers and stems of marigold (
Source of variation | Leaves | |||||||||||
Ocimene | Caryophyllene | Sabinene | Carene | β-phellandrene | β-myrcene | α-pinene | Terpinolene | Piperitone | γ-elemene | |||
Nitrogen (N) | 0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <.00001* |
Shading (S) | <0.0001* | <0.0001* | <0.0001* | <0.0001* | 0.1106 ns | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <.00001* |
N × S | 0.0009* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | <0.0001* |
Source of variation | Flowers | |||||||||||
Ocimene | Caryophyllene | Spathulenol | Piperitone | Verbenol | ||||||||
Nitrogen (N) | <0.0001* | <0.0001* | 0.0555 ns | <0.0001* | <0.0001* | <0.0001* | <0.0001* | |||||
Shading (S) | 0.5939 ns | 0.1473 ns | <0.0001* | <0.0001* | <0.0001* | 0.1292 ns | <0.0001* | |||||
N × S | <0.0001* | <0.0001* | 0.0015* | <0.0001* | <0.0001* | <0.0001* | <0.0001* | |||||
Source of variation | Stems | |||||||||||
Caryophyllene | Piperitone | β-farnesene | ||||||||||
Nitrogen (N) | <0.0001* | <0.0001* | <0.0001* | |||||||||
Shading (S) | 0.0004 | <0.0001* | <0.0001* | |||||||||
N × S | <0.0001* | <0.0001* | <0.0001* |
significant and no significant (ns) (Tukey,
With exception of carene, where the study factor shading had no significant influence, the main effects of nitrogen and shading and its interaction had significant influence in all components of essential oil in leaves (Table 4). In leaves, four compounds were consistently identified in all the treatments:
The most abundant compounds found in this study were ocimene,
With the lowest N dose in the nutrient solution, there was an inhibition in the synthesis of caryophyllene, β-phellandrene,
Some components of the oil were found only in the leaves with the extreme doses of the tested treatments (either at the minimum or the maximum levels). Thus, γ-elemene was only identified in leaves of plants exposed to 70% shading and a high N dose. Conversely, sabinene and terpinolene were only identified in the treatment with no shading and a low N dose (Table 3). Sabinene has been identified as a derivate of the resin extract of
Also,
In general, ocimene,
In flowers, the main effects of the study factors and their interactions were significative on compounds of flower essential oil, with exception of nitrogen on caryophyllene and shading on
Interestingly, caryophyllene was constantly found in flowers of the six treatments evaluated. Even though the effect of N was not significant as already indicated, and it was negatively affected by shading. On average, this compound was present in percentages lower than 1% (Table 5). For
The area under the curve (%) of the chemical compounds of the essential oil present in the leaves of marigold (
Compound | RT (min) | N (mg · L−1) | Shading (%) | ||||
8.47 | 12.71 | 16.94 | 0 | 70 | |||
12.24 | 20.33 ± 2.22 a | 12.35 ± 0.57 b | 6.73 ± 1.85 c | 15.19 ± 3.46 a | 11.08 ± 2.94 b | ||
Ocimene | 12.64 | 26.43 ± 5.78 a | 13.34 ± 2.60 b | 10.72 ± 2.79 c | 20.41 ± 6.39 a | 13.25 ± 2.92 b | |
Caryophyllene | 19.36 | ND ± 0.00 c | 1.40 ± 0.07 b | 1.57 ± 0.22 a | 0.83 ± 0.32 b | 1.15 ± 0.44 a | |
Sabinene | 10.94 | 3.54 ± 1.94 a | ND ± 0.00 b | ND ± 0.00 b | 2.36 ± 1.77 a | ND ± 0.00 b | |
Carene | 13.34 | 1.50 ± 0.82 b | 2.78 ± 0.10 a | 1.28 ± 0.70 b | 1.78 ± 0.68 a | 1.92 ± 0.72 a | |
β-phellandrene | 10.94 | ND ± 0.00 c | 2.17 ± 0.09 a | 1.62 ± 0.37 b | 1.48 ± 0.56 a | 1.05 ± 0.48 b | |
β-myrcene | 11.36 | 1.81 ± 0.39 a | 1.20 ± 0.05 b | 0.73 ± 0.20 c | 1.61 ± 0.34 a | 0.88 ± 0.20 b | |
α-pinene | 10.00 | 1.98 ± 0.31 a | 1.12 ± 0.04 b | 0.61 ± 0.16 c | 1.52 ± 0.39 a | ND ± 0.25 b | |
26.99 | ND ± 0.00 b | ND ± 0.00 b | 12.40 ± 6.79 a | ND ± 0.00 b | 8.27 ± 6.20 a | ||
Terpinolene | 13.40 | 2.64 ± 1.44 a | ND ± 0.00 b | ND ± 0.00 b | 1.76 ± 1.32 a | ND ± 0.00 b | |
Piperitone | 16.60 | 15.87 ± 4.24 a | 3.81 ± 2.09 c | 4.26 ± 2.33 b | 10.71 ± 5.18 a | 5.25 ± 1.97 b | |
γ-elemene | 21.27 | ND ± 0.00 b | ND ± 0.00 b | 0.11 ± 0.06 a | ND ± 0.00 b | 0.07 ± 0.06 a | |
Compound | RT (min) | N (mg · L−1) and shading (%) | |||||
8.47 and 0 | 8.47 and 70 | 12.71 and 0 | 12.71 and 70 | 16.94 and 0 | 16.94 and 70 | ||
12.24 | 24.13 ± 0.49 a | 16.53 ± 1.12 b | 11.7 ± 0.67 c | 12.46 ± 0.27 bc | 9.74 ± 1.20 c | 3.71 ± 0.57 d | |
Ocimene | 12.64 | 36.78 ± 1.64 a | 16.07 ± 0.56 b | 8.64 ± 0.04 c | 18.04 ± 0.60 b | 15.80 ± 0.07 b | 5.64 ± 0.32 c |
Caryophyllene | 19.36 | ND ± 0.00 d | ND ± 0.00 d | 1.31 ± 0.07 bc | 1.49 ± 0.04 b | 1.18 ± 0.04 c | 1.96 ± 0.06 a |
Sabinene | 10.94 | 7.08 ± 0.09 a | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b |
Carene | 13.34 | ND ± 0.00 b | 2.99 ± 0.08 a | 2.79 ± 0.13 a | 2.76 ± 0.10 a | 2.56 ± 0.09 a | ND ± 0.00 b |
β-phellandrene | 10.94 | ND ± 0.00 c | ND ± 0.00 c | 2.16 ± 0.12 a | 2.18 ± 0.08 a | 2.27 ± 0.11 a | 0.96 ± 0.02 b |
β-myrcene | 11.36 | 2.50 ± 0.13 a | 1.10 ± 0.02 b | 1.23 ± 0.05 b | 1.16 ± 0.05 b | 1.09 ± 0.05 b | 0.36 ± 0.03 c |
α-pinene | 10.00 | 2.54 ± 0.08 a | 1.42 ± 0.04 b | 1.13 ± 0.05 c | 1.11 ± 0.03 c | 0.89 ± 0.04 c | 0.32 ± 0.01 d |
26.99 | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | 24.80 ± 0.10 a | |
Terpinolene | 13.40 | 5.27 ± 0.03 a | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b |
Piperitone | 16.60 | 23.6 ± 0.08 a | 8.14 ± 0.04 c | ND ± 0.00 e | 7.62 ± 0.04 d | 8.52 ± 0.05 b | ND ± 0.00 e |
γ-elemene | 21.27 | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | 0.22 ± 0.03 a |
Means ± DE with different letters in each row and study factor indicates statistical significance (Tukey,
ND, compound was not detected; RT, retention time.
The area under the curve (%) of the chemical compounds of the essential oil present in the flowers of marigold (
Compound | RT (min) | N (mg · L−1) | Shading (%) | ||||
8.47 | 12.71 | 16.94 | 0 | 70 | |||
12.24 | ND ± 0.00 b | 0.15 ± 0.08 a | 0.15 ± 0.07 a | 0.10 ± 0.07 a | 0.10 ± 0.07 a | ||
Ocimene | 12.64 | ND ± 0.00 b | 0.25 ± 0.13 a | 0.27 ± 0.15 a | 0.18 ± 0.13 a | 0.16 ± 0.12 a | |
Caryophyllene | 19.36 | 0.49 ± 0.03 a | 0.55 ± 0.04 a | 0.55 ± 0.06 a | 0.61 ± 0.03 a | 0.45 ± 0.02 b | |
26.99 | ND ± 0.00 c | 8.15 ± 4.47 a | 1.89 ± 1.03 b | 6.69 ± 3.70 a | ND ± 0.00 b | ||
Spathulenol | 23.25 | 1.37 ± 0.75 a | 1.09 ± 0.60 b | ND ± 0.00 c | 0.91 ± 0.68 a | 0.72 ± 0.54 b | |
Piperitone | 16.60 | ND ± 0.00 b | 0.57 ± 0.31 a | 0.54 ± 0.29 a | 0.38 ± 0.28 a | 0.36 ± 0.27 a | |
Verbenol | 24.32 | ND ± 0.00 b | ND ± 0.00 b | 0.35 ± 0.19 a | ND ± 0.00 b | 0.23 ± 0.35 a | |
Compound | RT (min) | N (mg · L−1) and shading (%) | |||||
8.47 and 0 | 8.47 and 70 | 12.71 and 0 | 12.71 and 70 | 16.94 and 0 | 16.94 and 70 | ||
12.24 | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | 0.30 ± 0.01 a | 0.29 ± 0.01 a | ND ± 0.00 b | |
Ocimene | 12.64 | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | 0.49 ± 0.02 a | 0.53 ± 0.01 a | ND ± 0.00 b |
Caryophyllene | 19.36 | 0.54 ± 0.02 bc | 0.44 ± 0.02 c | 0.62 ± 0.01 ab | 0.47 ± 0.03 c | 0.66 ± 0.03 a | 0.44 ± 0.01 c |
26.99 | ND ± 0.00 c | ND ± 0.00 c | 16.30 ± 0.22 a | ND ± 0.00 c | 3.77 ± 0.02 b | ND ± 0.00 c | |
Spathulenol | 23.25 | 2.73 ± 0.04 a | ND ± 0.00 c | ND ± 0.00 c | 2.17 ± 0.03 b | ND ± 0.00 c | ND ± 0.00 c |
Piperitone | 16.60 | ND ± 0.00 b | ND ± 0.00 b | 1.13 ± 0.03 a | ND ± 0.00 b | ND ± 0.00 b | 1.07 ± 0.02 a |
Verbenol | 24.32 | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | ND ± 0.00 b | 0.69 ± 0.04 a |
Means ± DE with different letters in each row and study factor indicates statistical significance (Tukey,
ND, compound was not detected; RT, retention time.
The main effects of the study factors and their interactions had a significant effect on the compounds of the essential oil from stems, as is observed in Table 4.
In the oil obtained from stems, only three compounds were identified. The positive effect of N on the synthesis of β-farnesene was observed in the medium and high doses under evaluation. In plants treated with low N doses (i.e. 8.47 mg · L−1), this last compound and caryophyllene were not identified in the stems. Piperitone was the component that had the highest percentage with the low N level without shading (6.3%) (Table 7).
The area under the curve (%) of the chemical compounds of the essential oil present in the stems of marigold (
Compound | RT (min) | N (mg · L−1) | Shading (%) | ||||
8.47 | 12.71 | 16.94 | 0 | 70 | |||
Caryophyllene | 19.44 | ND ± 0.00 c | 1.27 ± 0.70 a | 1.14 ± 0.62 b | 0.76 ± 0.57 b | 0.85 ± 0.64 a | |
Piperitone | 16.53 | 3.15 ± 1.73 b | ND ± 0.00 c | 5.80 ± 0.17 a | 4.13 ± 1.55 a | 1.84 ± 1.38 b | |
β-farnesene | 20.03 | ND ± 0.00 c | 2.37 ± 0.49 b | 2.75 ± 0.06 a | 1.45 ± 0.62 b | 1.97 ± 0.75 a | |
Compound | RT (min) | N (mg · L−1) and shading (%) | |||||
8.47 and 0 | 8.47 and 70 | 12.71 and 0 | 12.71 and 70 | 16.94 and 0 | 16.94 and 70 | ||
Caryophyllene | 19.44 | ND ± 0.00 c | ND ± 0.00 c | ND ± 0.00 c | 2.54 ± 0.05 a | 2.28 ± 0.01 b | ND ± 0.00 c |
Piperitone | 16.53 | 6.3 ± 0.10 a | ND ± 0.00 c | ND ± 0.00 c | ND ± 0.00 c | 6.08 ± 0.04 a | 5.51 ± 0.08 b |
β-farnesene | 20.03 | ND ± 0.00 e | ND ± 0.00 e | 1.48 ± 0.04 d | 3.26 ± 0.02 a | 2.85 ± 0.03 b | 2.64 ± 0.02 c |
Means ± DE with different letters in each row and study factor indicates statistical significance (Tukey,
ND, compound was not detected; RT, retention time.
Herein, both N nutrition and light intensity were demonstrated to significantly affect plant morphology and essential oil composition of