Next Article in Journal
Characterization of the Calmodulin/Calmodulin-like Protein (CAM/CML) Family in Ginkgo biloba, and the Influence of an Ectopically Expressed GbCML Gene (Gb_30819) on Seedling and Fruit Development of Transgenic Arabidopsis
Next Article in Special Issue
Genetic Variation and Genotype by Environment Interaction for Agronomic Traits in Maize (Zea mays L.) Hybrids
Previous Article in Journal
Morphological, Biochemical, and Proteomic Analyses to Understand the Promotive Effects of Plant-Derived Smoke Solution on Wheat Growth under Flooding Stress
Previous Article in Special Issue
Plants and Phytoplasmas: When Bacteria Modify Plants
 
 
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Chemical Investigation and Dose-Response Phytotoxic Effect of Essential Oils from Two Gymnosperm Species (Juniperus communis var. saxatilis Pall. and Larix decidua Mill.)

1
Department of Food, Environmental and Nutritional Sciences, Milan State University, Via Mangiagalli 25, 20133 Milan, Italy
2
National Interuniversity Consortium of Materials Science and Technology, Via G. Giusti 9, 50121 Firenze, Italy
3
Department of Biomedical, Surgical and Dental Sciences, Milan State University, Via G. Celoria 2, 20133 Milan, Italy
4
Department of Environmental Science and Policy, Milan State University, Via G. Celoria 2, 20133 Milan, Italy
5
Department of Drug Chemistry and Technology, Sapienza University, P.le Aldo Moro 5, 00185 Rome, Italy
*
Author to whom correspondence should be addressed.
Those authors contributed equally to this work.
Plants 2022, 11(11), 1510; https://doi.org/10.3390/plants11111510
Received: 16 May 2022 / Revised: 27 May 2022 / Accepted: 1 June 2022 / Published: 4 June 2022
(This article belongs to the Special Issue 10th Anniversary of Plants—Recent Advances and Perspectives)

Abstract

:
The chemical composition of the liquid and vapor phases of leaf essential oils (EOs) obtained from two species of Gymnosperms (Juniperus communis var. saxatilis Willd. and Larix decidua Mill.) was investigated using the SPME-GC-MS technique. The results highlighted a composition characterized by 51 identified volatile compounds (34 in J. communis and 39 in L. decidua). In both bloils, monoterpenes prevailed over the sesquiterpenes, albeit with qualitative and quantitative differences. Sabinene (37.5% and 34.5%, respectively) represented the two most abundant components in the liquid and vapor phases of J. communis, and α-pinene (51.0% and 63.3%) was the main constituent in L. decidua. The phytotoxic activity of the two EOs was assessed in pre-emergence conditions using three concentrations in contact (2, 5, 10 µL/mL) and non-contact (2, 20, 50 µL) tests against Lolium multiflorum Lam. (Poaceae) and Sinapis alba L. (Brassicaceae). Treatments were effective in a dose-dependent manner by significantly reducing the germination (up to 100% and 45–60%, respectively, with filter paper and soil as a substrate) and the seedling development (1.3 to 8 times) of both target species. Moreover, an exploratory survey on the residual presence of volatile compounds in the soil at the end of the tests was carried out.

1. Introduction

Since man became a farmer 10,000 years ago, he has always had to fight against weeds, which have been a constant component of the agro-ecosystem. They have adapted to crop systems and co-evolved with them, significantly interfering with the human activities. From an ecological point of view, weeds are plants capable of colonizing potentially productive environments, managing to persist in conditions of repeated disturbance [1]. In the field, they cause significant damage for farmers. The most relevant effects include a decrease in crop production and a deterioration in its quality, in addition to an obstacle to mechanical operations. Another equally important aspect concerns the enrichment of the stock of seeds in the soil following the dissemination caused by their uncontrolled development [2]. Weeds can be controlled by various means (physical, ecological, mechanical, and chemical). Synthetic herbicides have been widely used since their discovery in the first decades of the previous century [3]. However, the growing problems related to weed management, such as resistance to herbicides, their low biodegradability, and high percolation and persistence in the soil, are increasing concerns relating to human health and environmental issues [4].
As a result of these problems, in recent years, various natural products have been studied for their allelopathic activity, including essential oils (EOs) and some of their constituents. EOs are multicomponent mixtures of plant volatiles able to exert a phytotoxic effect by providing an eco-chemical approach [5]. Their contact action causes rapid drying of the green plant parts by destroying the leaf cuticle and cell membranes [6]. In detail, allelochemicals can affect physiological functions, such as seed germination, respiration, photosynthesis, ion uptake, enzyme activity, transpiration, and hormone levels. They can also alter gene expression, the signal transduction chain, and permeability of the cell wall and membrane, and enhance the production of reactive oxygen species, or modify both the division and differentiation of cells [7]. The inhibition of germination and plant growth by EOs has been mainly attributed to terpenes, in particular, monoterpenes [8]. In general, essential oils offer an interesting class of compounds for management of parasites and weeds due to their low persistence in soil, relatively low toxicity towards mammals, and less stringent regulatory approval mechanisms [9].
In this work, we focused on the phytotoxic potential of EOs from two species of gymnosperms, namely Juniperus communis var. saxatilis Pall. (Cupressaceae) and Larix decidua Mill. (Pinaceae). The allelopathic activity of gymnosperms has long been known [10]. Several families—Araucariaceae, Cupressaceae, Pinaceae, Podocarpaceae, and Taxaceae—shows a strong negative allelopathic effect on the germination and growth of other plants [11]. In most of the cases, the allelochemicals identified as responsible for these interactions are the phenolic compounds leached from the litter consisting mainly of tree needles [10,11]. Until now, few reports have documented the phytotoxicity including autotoxicity of EOs obtained from leaves of species belonging to Juniperus [12,13,14] and Larix [15,16,17] genera. Our aim was to evaluate and compare the inhibitory effects of the two EOs used in different ways—via air and direct contact—on the germination and seedling growth of both monocot and dicot weed species, after determining the chemical composition of both liquid and vapor phases by means of the solid-phase micro-extraction gas chromatography-mass spectrometry (SPME-GC-MS) technique. The changes in the volatile profile occurring in the soil samples after the treatments with the EOs were also investigated.

2. Results

2.1. Essential Oil Chemical Composition

To describe the chemical profile of the liquid and vapor phases, the EOs were analyzed using the SPME-GC-MS technique. In total, 51 compounds were identified, of which 34 were in J. communis and 39 in L. decidua (Table 1). In both oils, the monoterpenes prevailed over the sesquiterpenes. Among the former, sabinene (37.5%, 34.5%) was the most abundant component in the liquid and vapor phases of J. communis, respectively, and α-pinene (51.0%, 63.3%) was the main constituent of L. decidua. Furthermore, the vapor phase of J. communis was enriched with limonene (14.0%), p-cymene (7.5%), and β-myrcene (12.6%), and that of L. decidua was enriched with β-ocimene (10.2%), β-pinene (7.9%), β-myrcene (6.2%) and limonene (4.5%) as principal compounds.
Qualitative differences between the two EOs were noted. In particular, β-ocimene (10.2%), 1,8-cineole (3.2%), and trans-pinovcarveol (1.1%) were detected only in L. decidua; cis-thujopsene (2.1%), δ-cadinene (2.4%), τ-muurolol (0.6%), and α-cadinol (0.4%) were characteristic only in J. communis; and a number of other minor compounds (ranging from 0.1% to 0.3%) were detected in one of the EOs.

2.2. Soil Chemical Composition

The chemical composition of the EO residual vapor phase emitted from the soils at the end of both non-contact and contact tests was investigated using the SPME-GC/MS technique. The compounds detected in the samples with 20 or 50 µL of J. communis EO submitted to the non-contact test are listed in Table 2. In total, 55.9% of the starting compounds remained. cis-Thujopsene was the most abundant compound in all soils with percentage values equal to 30.2% and 40.5% in the samples where L. multiflorum seeds were sown at 20 and 50 µL, respectively, and 26.7% and 32.2% in the corresponding samples with S. alba seeds. This compound was followed by α-pinene (19.0% and 20.4%) in the presence of L. multiflorum and by β-elemene (12.9% and 13.7%) in the presence of S. alba. No residual volatile component was found in the soils treated with 2 µL of EOs.
The compounds released from the soils with 20 or 50 µL of L. decidua EO without direct contact with seeds are listed in Table 3. Among the five detected components, α-pinene was the most abundant in all the samples, with values ranging from 37.8% (soil with S. alba at 20 µL EO) to 87.7% (soil with L. multiflorum at 20 µL EO). Moreover, in this case, no residual volatile component was found to be emitted from the soils treated with 2 µL of EOs.
Only three compounds were detected for the soil samples containing L. multiflorum and S. alba seeds in direct contact with 5 and 10 µL of J. communis and L. decidua EOs (Table 4 and Table 5). α-Thujene was the main volatile for the soils treated with J. communis EO, regardless of the type of seed species. In particular, it was the only one for the sample with S. alba seeds subjected to the action of 5 µL of L. decidua EO (Table 4). In contrast, α-pinene (≥81.8%) characterized the chemical composition of the volatile emission of the soils in direct contact with L. decidua EO (Table 5).

2.3. Effectiveness of EOs in Non-Contact Germination Test (Filter Paper Substrate)

The results for J. communis and L. decidua EOs showed a significant impact (p-values = 0.000) on all the considered indices, in both target species (Table 6). In particular, the treatments performed with the highest dose (50 µL) of J. communis EO totally inhibited the L. multiflorum germination (G = 0%) and reduced that of S. alba by 67.3%, also affecting the other considered parameters (CVG = −75%; MGT = +11.6%; SVI = −92.3%; root length = −90.3%; shoot length = −71.2%). The same dose of Larix decidua EO was even more effective, preventing the germination of both L. multiflorum and S. alba. Moreover, the obtained data evidenced that L. multiflorum was the most susceptible species. The values of its indices, except for MGT in some cases, were also significantly decreased by the lowest doses (2 and 20 µL) of both EOs.

2.4. Effectiveness of EOs in Non-Contact Germination Test (Soil Substrate)

The data reported in Table 7 also confirmed the efficacy of the J. communis and L. decidua EOs in the tests carried out using the soil as a substrate. All the indices, except G for L. multiflorum under the effect of J. communis EO, underwent significant variations (p-values < 0.05), if only due to the action of the highest tested dose. In detail, CVG of L. multiflorum and shoot length decreased by 49.5% and 33%, respectively, while MGT increased by 12.8% with 50 µL of J. communis EO. These values reached −60.8%, −59.4%, and +6.1% in the presence of the 50 µL of L. decidua EO. Regarding S. alba, the same treatments, respectively, reduced G by 26.6% and 43.2%, CVG by 32.4 and 60.2%, and shoot length by 25.5% and 42.6%, and increased MGT to +6.8% and +10.9%. In some cases, lower doses of both EOs were able to significantly affect the germination (e.g., −15% for S. alba at 2 µL of J. communis and −35.5% for L. multiflorum at 20 µL of L. decidua) and development (e.g., −9.9 for L. multiflorum at 2 µL of J. communis and −23.6% for S. alba at 20 µL of L. decidua) of the two target species.
The “interaction species × treatment” (EO doses) was not significant (p-value > 0.05) for G% after the J. communis treatment and for CVG and MGT indices after L. decidua use.

2.5. Effectiveness of EO in Contact Germination Test (Filter Paper Substrate)

The J. communis and L. decidua EOs tested in direct contact with seeds using filter paper as a substrate showed phytotoxic activity against both L. multiflorum and S. alba, influencing most of their germination and growth parameters (Table 8). In this case, the “interaction species × treatment” (EO doses) was not significant only for CVG (p-value > 0.05) after the J. communis treatments.
Both EOs completely inhibited the germination of L. multiflorum (G = 0%) at the 50 µL dose. L. decidua also had the same effect at 20 µL, preventing the calculation of the related indices. At 2 µL, it inhibited G of L. multiflorum by 43.7%, CVG by 63%, SVI by 66.4%, and brought MGT to +5.8%. Its impact on S. alba was comparable (higher for some indices, lower for others) to that of J. communis when used at 50 µL (G, −74.5% vs. −53.2%; CVG, −83.2% vs. −69.6%; MGT, +11.1% vs. +16.3%, SVI, 91.3% vs. −75.4%, root length, −45.6% vs. −56.6%, shoot length, −21.8% vs. −39%), and was generally less effective at the two lower doses.

2.6. Effectiveness of EO Vapor Phase in Contact Germination Test (Soil Substrate)

The data shown in Table 9 corroborated the above results regarding the effectiveness of the J. communis and L. decidua EOs against the two target species, despite the presence of the soil and the resulting interference. In general, they were able to similarly reduce the germination of L. multiflorum (by up to −53.9% and 50.2%, respectively). J. communis EO more influenced its CVG (−21.3% to −76.9%) and MGT (+8.3% to +16.7%) values than L. decidua EO. However, the latter limited the shoot elongation of L. multiflorum to 2.4 times compared to 1.3 times for J. communis EO. A similar trend was observed with respect to S. alba (G, −10.7% to −62.5% vs. −12.6% to −38.9%; CVG, −30.6% to −77.5% vs. −32.8% to −58.2%; MGT, +6.7% to 11.1% vs. +11.1% to +13.3%; shoot length, −0.7% to −35.3% vs. −17% to −40%).
Lastly, the “interaction species × treatment” (EO doses) was not significant for G and CVG after the J. communis EO treatment (p-value > 0.05), whereas it was significant only for the shoot length parameter in the presence of L. decidua EO (p-value = 0.00).

3. Discussion

The chemical composition of the liquid and vapor phases of two EOs obtained from leaves of J. communis var. saxatilis and L. decidua was determined by SPME-GC/MS analyses. Gymnosperms and, in particular, conifers produce EOs characterized by compounds belonging to the family of terpenes such as monoterpenes, sesquiterpenes, and their derivatives [18]. In agreement with previous works [19,20,21,22], our results showed monoterpenes prevail over sesquiterpenes. In particular, the two major components of J. communis and L. decidua EOs were α-pinene or sabinene, which were also found in other Juniperus [23,24] and Larix species [17,25,26]. Nevertheless, qualitative and/or quantitative differences in the chemical composition can be found, especially for minor compounds [27,28,29,30,31]. This is due to the different genotype or species [32,33], environmental conditions and soil composition [34,35], geographical area of origin [36] and harvesting period, in addition to different extraction methods and plant parts [37,38].
It is known that monoterpenes possess phytotoxic effects capable of leading to anatomical and physiological changes in plant seedlings, probably due to the inhibition of DNA synthesis or the rupture of mitochondrial membranes [39,40]. In particular, it was reported that α-pinene strongly inhibited mitochondrial ATP production [41] and root growth, also causing oxidative damage [42]. Furthermore, several monoterpenes, including α-pinene, have been shown to have inhibiting abilities on germination and radicle elongation of Raphanus sativus L. and Lepidium sativum L. [43]. Regarding sabinene, some studies documented the phytotoxicity of different EOs having this compound among the main constituents [44,45,46]. For example, a sabinene chemotype identified for EO from Ravensara aromatica Sonn. showed strong toxicity against Oryza sativa L. and Lepidium sativum L. [44]. Nonetheless, the higher percentage of α-pinene in our L. decidua EO may justify its greater effectiveness compared to the J. communis EO, in which sabinene was the most abundant. However, it is highly probable that the herbicidal activity of both EOs found in this work cannot be exclusively attributed to α-pinene and/or sabinene, but to the combined effect (synergistic or additive) of several molecules, including the minor ones. Indeed, as has been recently confirmed, mixtures of compounds are much more active and trigger different and more drastic responses [47].
EOs from conifer leaves have been reported to have high therapeutic potential [48] and, therefore, they are widely used in the treatment of infections and inflammatory phenomena [49]. Several studies demonstrated their biological properties [20,50,51,52,53,54,55,56,57], including allelopathic effects [10,11]. Nevertheless, EOs obtained from Juniperus and Larix species have been rather neglected from this point of view. Recently, Semerdjieva and co-authors [58] investigated the allelopathic activity of J. sabina L. and J. excelsa Bieb. EOs, reporting different inhibitory actions depending on the target species, the type of used EO, and the relative concentrations. Previously, Mehdizadeh et al. [14] documented the phytotoxic potential of EO obtained from the leaves of J. polycarpos var. turcomanica (B.Fedtsch.) R.P. Adams against three species of weeds, namely, Portulaca oleracea L., Amaranthus retroflexus L., and Datura stramonium L., attributing it to its major group of constituents, namely, monoterpenes hydrocarbons. Herbicidal effects were also reported for J. oxycedrus L. subsp. macrocarpa and J. phoniceae EOs, which were able to strongly reduce the germination and seedling growth of all tested weeds, in a dose-dependent manner [13,59]. In the case of J. phoniceaea, its EO also increased the proline level and caused severe electrolyte leakage from the roots of all target weeds, indicating membrane disruption and loss of integrity [59]. Finally, the J. communis EO exhibited no phytotoxic effect against Ailanthus altissima (Mill.) Swingle, resulting in 0% seedling mortality [23]. Few data are also available on the phytotoxicity of EOs from the genus Larix. The most recent work [17] studied the herbicidal effects of L. kaempferi (Lamb.) Carrière, demonstrating its capacity to inhibit the growth of Brassica napus L. by 50% in a seed bioassay and its inability to stop the development of new shoots after a foliar application of 10% EO in a greenhouse experiment. Previously, the negative effect of volatile substances of L. gmelinii (Rupr.) Kuzen. EO on the growth of Fraxinus mandshurica Rupr. was mainly attributed to α-pinene [15], while the EO from leaves and branches of L. principis-rupprechtii affected its own regeneration with significant inhibitory effects on the germination rate, radicle and hypocotyl length, and fresh mass [16].
In general, our data, in addition to highlighting a greater efficacy of the L. decidua EO, showed the different susceptibility of the two target species. L. multiflorum (monocotyledon) was more sensitive to treatments than S. alba (dicotyledon). Furthermore, the effects of both EOs were reduced by the interaction with the soil, with significant results still being obtained. In this type of substrate, we wanted to check for the possible presence of residual volatile terpenes. As expected, after 7 days, most of them were not detected, with differences between the two tests. Their absence, which may be due to the ability of soil particles to adsorb the volatile terpenes and subsequently release them to penetrate the seeds and exert their possible toxicity, deserves to be further investigated [60].

4. Materials and Methods

4.1. Plant Material

Bio EOs from leaves of J. nana and L. decidua were directly supplied from Bergila GmbH Srl (Falzes/Issengo-Bolzano, Italy) and stored at 4 °C until use.
Target seeds of L. multiflorum (grass) and S. alba L. (broadleaf) were provided by the organic farm “Terre di Lomellina” (Pavia, Italy) and purchased from the company “Padana Sementi” (Padua, Italy), respectively. Before use, they were sterilized with 1% sodium hypochlorite solution for 10 min, then repeatedly rinsed with distilled water.

4.2. Solid-Phase Microextraction (SPME)

To describe the chemical profile of the headspace from two EOs and of soil samples, a SPME device from Supelco (Bellefonte, PA, USA) was used for the sampling. The soil (~1 g) and the EOs (~2 mL) were individually placed into a 15 mL glass vial with PTFE-coated silicone septum. The chosen fiber was coated with 50/30μm DVB/CAR/PDMS (divinylbenzene/carboxen/polydimethylsiloxane). Before sampling, the fiber was conditioned at 270 °C for 20 min. First, the samples were equilibrated for 30 min at 50 °C prior to analysis. Subsequently, the fiber was exposed to the equilibrated headspace for 10 and 30 min to capture the volatile components from EOs and soil samples, respectively. Later, the fiber was inserted in a GC injector maintained at 250 °C for the desorption of collected components.

4.3. Gas Chromatography/Mass Spectrometry (GC/MS)

All analyses were performed using a Clarus 500 model Perkin Elmer (Waltham, MA, USA) gas chromatograph coupled with a mass spectrometer and equipped with an FID (flame detector ionization). In the GC oven was housed a Varian Factor Four VF-1 capillary column and helium was used as carrier gas at a flow rate of 1 mL/min. The adopted chromatographic conditions followed a previous study [61]. The mass spectra were obtained in the electron impact mode (EI), at 70 eV in scan mode in the range 35–400 m/z. The identification of volatile compounds was performed by matching their mass spectra with those stored in the Wiley 2.2 and Nist 02 mass spectra libraries database and by comparison of their linear retention indices (LRIs), relative to C8–C25 n-alkanes analyzed under the same conditions, with those available in the literature. Relative amounts of compounds, expressed as a percentage, were calculated in relation to the total area of the chromatogram by normalizing the peak area without the use of an internal standard and any factor correction. All analyses were carried out in triplicate.

4.4. Phytotoxic Studies

4.4.1. Non-Contact Germination Test with EOs

Seeds (15) of the target species L. multiflorum and S. alba were sown in 9 cm diameter Petri dishes lined with filter paper (Whatman No. 1) wetted with 4 mL of sterilized water. The EOs of J. communis or L. decidua were pipetted (2, 20, or 50 µL) into a small handmade aluminum container placed in the center of each Petri dish to avoid direct contact with seeds. To evaluate the phytotoxic activity of the EOs using a different substrate, the seeds (15) were also sown in 9 cm diameter Petri dishes filled with 25 g of non-fertilized soil (Vigorplant® SER CA 98 V7, Fombio (Lo), Italy) wetted with 15 mL of sterilized water. Sterile 6 mm diameter disks (1 or 3) impregnated with different amounts (2, 20, or 50 µL) of J. nana or L. decidua EO were placed at the same depth as the seeds and covered with soil. In their respective controls, the EOs were absent and replaced by distilled water (2, 20 or 50 µL). Tests were carried out under a biological hood with vertical laminar flow. Subsequently, the suitably sealed (double layer of Parafilm) and initialed Petri dishes were incubated for 16 h light at 23 °C and 8 h darkness at 18 °C in a climatic chamber for 7 days. The experimental design included 3 quantities of each EO (treated samples) or distilled water (control samples) × 2 target species × 3 replicates × 2 runs.

4.4.2. Contact Germination Test with EOs

Seeds (15) of the target species L. multiflorum and S. alba were sown in 9 cm diameter Petri dishes lined with filter paper (Whatman No. 1) wetted with 4 mL of an oily solution prepared with different concentrations (2, 5, and 10 µL/mL) of J. communis or L. decidua EO and using 0.1% Tween® 20 (Sigma-Aldrich, Milan, Italy) as surfactant. To evaluate the same phytotoxic activity of the EOs using a different substrate, the seeds (15) were also sown in 9 cm diameter Petri dishes filled with 25 g of non-fertilized soil (Vigorplant® SER CA 98 V7 Fombio (Lo), Italy) wetted with 15 mL of the same oily solutions prepared with different concentrations (2, 5, and 10 µL/mL) of J. communis or L. decidua EO and using 0.1% Tween® 20 (Sigma-Aldrich, Milan, Italy) as surfactant. In their respective controls, the EOs were absent and replaced by 0.1% Tween® 20 solution (4 or 15 mL). The test was carried out under a biological hood with vertical laminar flow. Subsequently, the suitably sealed (double layer of Parafilm) and initialed Petri dishes were incubated for 16 h light at 23 °C and 8 h darkness at 18 °C in a climatic chamber for 7 days. The experimental design included 3 quantities of each EO (treated samples) or distilled water (control samples) × 2 target species × 3 replicates × 2 runs.

4.5. Data Analysis

Phytotoxic effects of the J. communis and L. decidua EOs on germination and seedling development of the target species were described using the following indices:
  • Germination percentage (G) = Germinated seed number)/(Seed total number) × 100;
  • Coefficient of Velocity of Germination (CVG) = N1 + N2 + … + Ni/100 × N1T1 + … + NiTi, where N is the number of seeds germinated every day; T is the number of days from seeding corresponding to N [62];
  • Mean Germination Time (MGT) = (∑D × Germinated seed number)/(∑Germinated seed number), where D is the number of days from the beginning of germination, plus the number of seeds germinated on day D [63];
  • Seedling Vigor Index (SVI) = (Mean Root length + Mean Shoot length) × Germination %. [64].
The number of germinated seeds was detected every day for a week, and the measurements on the radicle and shoot of the seedlings were carried out at the end of the test, seven days after sowing.

4.6. Statistical Analysis

The data were evaluated with the support of IBM SPSS software, through the analysis of variance carried out separately for each EO (i.e., from the two species J. communis and L. decidua) and substrate (i.e., filter paper and soil). The germination and growth indices (i.e., G%, CVG, MGT, SVI, root length, shoot length) measured for the two target species (i.e., L. multiflorum and S. alba) under different treatments were taken into account as dependent variables.
The one-way ANOVA and the Turkey’s-b post hoc test were performed in order to establish the significant effect (at α ≤ 0.05) of the treatments with EOs (i.e., the different levels of concentration or quantity in EOs, respectively) on the target species and describe the homogenous subsets.
Moreover, the two-way ANOVA was performed, considering as factors the treatments with EOs and the species, in order to highlight the significant interaction (α ≤ 0.05) between “species × treatments” and then highlighting the species-specific effects of the treatments and the different behavior or susceptibility of L. multiflorum (grass) and S. alba (broadleaf).

5. Conclusions

Essential oils extracted from certain species of plants can represent a valid alternative to the use of synthetic chemicals as natural herbicidal agents capable of guaranteeing a phytotoxic effect but, at the same time, respectful of the environment and human health.
In our study, J. communis and L. decidua EOs were investigated in order to evaluate and compare their allelopathic effects, and on the basis of their chemical compositions. The findings showed that both EOs were active in a dose-dependent manner, but with greater efficacy shown in L. decidua EO against Lolium multiflorum and Sinapis alba L.
In conclusion, due to the obtained data, we can confirm that the EOs from gymnosperms, and their main components, may represent an important source for the development of new low-impact natural products against weeds.

Author Contributions

Conceptualization, S.G. and S.V.; investigation, S.G. and S.V.; data curation, M.I., S.G., S.V. and V.V.; writing—original draft preparation, S.G., S.V. and V.V.; writing—review and editing, M.I., S.G. and S.V.; funding acquisition, M.I. and S.G. All the authors critically edited the manuscript before submission. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All generated data are included in this article.

Acknowledgments

The authors are thankful to Bergila, GmbH Srl (Falzes/Issengo-Bolzano) Italy, for providing J. communis var. saxatilis and L. decidua essential oils.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Liebman, M.; Mohler, C.L.; Staver, C.P. (Eds.) Ecological Management of Agricultural Weeds; Cambridge University Press: Cambridge, UK, 2001. [Google Scholar]
  2. Chauhan, B.S. Grand challenges in weed management. Front. Agron. 2020, 1, 3. [Google Scholar] [CrossRef]
  3. Dayan, F.E. Current status and future prospetcs in herbicide discovery. Plants 2019, 8, 341. [Google Scholar] [CrossRef] [PubMed][Green Version]
  4. Tataridas, A.; Kanatas, P.; Chatzigeorgiou, A.; Zannopoulos, S.; Travlos, I. Sustainable crop and weed management in the era of the EU Green Deal: A survival guide. Agronomy 2022, 12, 589. [Google Scholar] [CrossRef]
  5. Ibáñez, M.D.; Blázquez, M.A. Phytotoxic effects of commercial essential oils on selected vegetable crops: Cucumber and tomato. Sustain. Chem. Pharm. 2020, 15, 100209. [Google Scholar] [CrossRef]
  6. Ahuja, N.; Batish, D.R.; Singh, H.P.; Kohli, R.K. Herbicidal activity of eugenol towards some grassy and broad-leaved weeds. J. Pest Sci. 2015, 88, 209–218. [Google Scholar] [CrossRef]
  7. Scognamiglio, M.; D’Abrosca, B.; Esposito, A.; Pacifico, S.; Monaco, P.; Fiorentino, A. Plant growth inhibitors: Allelopathic role or phytotoxic effects? Focus on Mediterranean biomes. Phytochem. Rev. 2013, 12, 803–830. [Google Scholar] [CrossRef]
  8. Ishii-Iwamoto, E.L.; Pergo Coelho, E.M.; Reis, B.; Moscheta, I.S.; Moacir Bonato, C. Effects of monoterpenes on physiological processes during seed germination and seedling growth. Curr. Bioact. Compd. 2012, 8, 50–64. [Google Scholar] [CrossRef]
  9. Raveau, R.; Fontaine, J.; Lounès-Hadj Sahraoui, A. Essential oils as potential alternative biocontrol products against plant pathogens and weeds: A review. Foods 2020, 9, 365. [Google Scholar] [CrossRef][Green Version]
  10. Singh, H.P.; Kohli, R.K.; Batish, D.R.; Kaushal, P.S. Allelopathy of gymnospermous trees. J. For. Res. 1999, 4, 245–254. [Google Scholar] [CrossRef]
  11. Teixeira da Silva, J.A.; Karimi, J.; Mohsenzadeh, S.; Dobránszki, J. Allelopathic potential of select gymnospermous trees. J. For. Sci. 2015, 31, 109–118. [Google Scholar]
  12. Young, G.P.; Bush, J.K. Assessment of the allelopathic potential of Juniperus ashei on germination and growth of Bouteloua curtipendula. J. Chem. Ecol. 2009, 35, 74–80. [Google Scholar] [CrossRef] [PubMed]
  13. Ismail, A.; Lamia, H.; Hanana, M.; Jamoussi, B. Chemical composition of Juniperus oxycedrus L. subsp. macrocarpa essential oil and study of their herbicidal effects on germination and seedling growth of weeds. Asian J. Appl. Sci. 2011, 4, 771–779. [Google Scholar] [CrossRef][Green Version]
  14. Mehdizadeh, L.; Taheri, P.; Ghasemi Pirbalouti, A.; Moghaddam, M. Phytotoxicity and antifungal properties of the essential oil from the Juniperus polycarpos var. turcomanica (B. Fedsch.) R.P. Adams leaves. Physiol. Mol. Biol. Plants 2020, 26, 759–771. [Google Scholar] [CrossRef] [PubMed]
  15. Wu, J.M.; Li, B.N.; Liu, G.P.; Wang, X.S.; Wu, B.G. Effect of volatile substances of larch on the growth of ash in a mixed forest plantation. J. Northeast For. Univ. 2000, 28, 25–28. [Google Scholar]
  16. Fen, H.A.N.; Hui, W.; Yin-Xia, B.; Yong-Bing, L.I. Chemical components and their allelopathic effects of the volatiles from Larix principis-rupprechtii leaves and branches. Chin. J. Appl. Ecol. 2008, 19, 2327–2332. [Google Scholar]
  17. Yun, M.S.; Cho, H.M.; Yeon, B.-R.; Choi, J.S.; Kim, S. Herbicidal activities of essential oils from pine, nut pine, larch and khingan fir in Korea. Weed Turf. Sci. 2013, 2, 30–37. [Google Scholar] [CrossRef][Green Version]
  18. Bhardwaj, K.; Islam, M.T.; Jayasena, V.; Sharma, B.; Sharma, S.; Sharma, P.; Kuča, K.; Bhardwaj, P. Review on essential oils, chemical composition, extraction, and utilization of some conifers in Northwestern Himalayas. Phyther. Res. 2020, 34, 2889–2910. [Google Scholar] [CrossRef]
  19. Bali, A.S.; Batish, D.R.; Singh, H.P. Allelopathic effect of aromatic plants: Role of volatile essential oils. J. Global. Biosci. 2016, 5, 4386–4395. [Google Scholar]
  20. Visan, D.-C.; Oprea, E.; Radulescu, V.; Voiculescu, I.; Biris, I.-A.; Cotar, A.I.; Saviuc, C.; Chifiriuc, M.C.; Marinas, I.C. Original contributions to the chemical composition, microbicidal, virulence-arresting and antibiotic-enhancing activity of essential oils from four coniferous species. Pharmaceuticals 2021, 14, 1159. [Google Scholar] [CrossRef]
  21. Sahin, H.T.; Yalcin, O.U. Chemical Composition and Utilization of Conifer Needles-A Review. J. Appl. Life Sci. Int. 2017, 14, 1–11. [Google Scholar] [CrossRef]
  22. Garcia, G.; Garcia, A.; Gibernau, M.; Bighelli, A.; Tomi, F. Chemical compositions of essential oils of five introduced conifers in Corsica. Nat. Prod. Res. 2017, 31, 1697–1703. [Google Scholar] [CrossRef] [PubMed]
  23. Karalija, E.; Dahija, S.; Parić, A.; Zeljković, S.Ć. Phytotoxic potential of selected essential oils against Ailanthus altissima (Mill.) Swingle, an invasive tree. Sustain. Chem. Pharm. 2020, 15, 100219. [Google Scholar] [CrossRef]
  24. Zheljazkov, V.D.; Cantrell, C.L.; Semerdjieva, I.; Radoukova, T.; Stoyanova, A.; Maneva, V.; Kačániová, M.; Astatkie, T.; Borisova, D.; Dincheva, I.; et al. Essential oil composition and bioactivity of two juniper species from Bulgaria and Slovakia. Molecules 2021, 26, 3659. [Google Scholar] [CrossRef] [PubMed]
  25. Holm, Y.; Laakso, I.; Hiltunen, R. Variation and inheritance of monoterpenes in Larix species. Flavour Fragr. J. 1997, 12, 335–339. [Google Scholar] [CrossRef]
  26. Doi, M.; Toeda, K.; Myoda, T.; Hashidoko, Y.; Fujimori, T. Seasonal fluctuations of aroma components of essential oils from Larix leptolepis. J. Oleo Sci. 2019, 68, 671–677. [Google Scholar] [CrossRef][Green Version]
  27. Loizzo, M.R.; Saab, A.M.; Tundis, R.; Menichini, F.; Bonesi, M.; Statti, G.A.; Menichini, F. Chemical composition and antimicrobial activity of essential oils from Pinus brutia (calabrian pine) growing in Lebanon. Chem. Nat. Compd. 2008, 44, 6. [Google Scholar] [CrossRef]
  28. Thai, T.H.; Hien, N.T.; Cuong, N.; Casanova, J.; Tomi, F.; Paoli, M. Chemical composition of essential oils isolated from leaves, twigs, roots and cones of Vietnamese Keteleeria evelyniana Mast. J. Essent. Oil Res. 2022, 34, 148–154. [Google Scholar] [CrossRef]
  29. Lee, J.H.; Lee, B.K.; Kim, J.H.; Lee, S.H.; Hong, S.K. Comparison of chemical compositions and antimicrobial activities of essential oils from three conifer trees; Pinus densiflora, Cryptomeria japonica, and Chamaecyparis obtusa. J. Microbiol. Biotechnol. 2009, 19, 391–396. [Google Scholar] [CrossRef][Green Version]
  30. Höferl, M.; Stoilova, I.; Schmidt, E.; Wanner, J.; Jirovetz, L.; Trifonova, D.; Krastev, L.; Krastanov, A. Chemical composition and antioxidant properties of juniper berry (Juniperus communis L.) essential oil. Action of the essential oil on the antioxidant protection of Saccharomyces cerevisiae model organism. Antioxidants 2014, 3, 81–98. [Google Scholar] [CrossRef][Green Version]
  31. Cabral, C.; Francisco, V.; Cavaleiro, C.; Gonçalves, M.J.; Cruz, M.T.; Sales, F.; Batista, M.T.; Salguerio, L. Essential oil of Juniperus communis subsp. alpina (Suter) Čelak needles: Chemical composition, antifungal activity and cytotoxicity. Phytother. Res. 2012, 26, 1352–1357. [Google Scholar] [CrossRef]
  32. Zheljazkov, D.; Astatkie, T.; Jeliazkova, E.A.; Heidel, B.; Ciampa, L. Essential oil content, composition and bioactivity of Juniper species in Wyoming, United States. Nat. Prod. Commun. 2017, 12, 201–204. [Google Scholar] [CrossRef] [PubMed][Green Version]
  33. Holubová, V.; Hrdlicka, P.; Kubán, V. Age and space distributions of monoterpenes in fresh needles of Picea abies (L) Karst. determined by gas chromatography-mass spectrometry. Phytochem. Anal. 2001, 12, 243–249. [Google Scholar] [CrossRef] [PubMed]
  34. Kupcinskiene, E.; Stikliene, A.; Judzentiene, A. The essential oil qualitative and quantitative composition in the needles of Pinus sylvestris L. growing along industrial transects. Environ. Pollut. 2008, 155, 481–491. [Google Scholar] [CrossRef] [PubMed]
  35. Arlinda, A.; Kadiasi, N.; Alban, I. Effect of soil composition elements on essential oils content of Juniperus communis L. berries in north populations in Albania. Int. J. Curr. Res. 2021, 13, 19794–19797. [Google Scholar]
  36. Hajdari, A.; Mustafa, B.; Nebija, D.; Miftari, E.; Quave, C.L.; Novak, J. Chemical Composition of Juniperus communis L. Cone Essential Oil and Its Variability among Wild Populations in Kosovo. Chem. Biodivers. 2015, 12, 1706–1717. [Google Scholar] [CrossRef]
  37. Angioni, A.; Barra, A.; Russo, M.T.; Coroneo, V.; Dessi, S.; Cabras, P. Chemical composition of the essential oils of Juniperus from ripe and unripe berries and leaves and their antimicrobial activity. J. Agric. Food Chem. 2003, 7, 3073–3078. [Google Scholar] [CrossRef]
  38. Koukos, P.K.; Papadopoulou, K.I. Essential oil of Juniperus communis L. grown in Northern Greece: Variation of fruit oil yield and composition. J. Essent. Oil Res. 1997, 9, 35–39. [Google Scholar] [CrossRef]
  39. Nishida, N.; Tamotsu, S.; Nagata, N.; Saito, C.; Sakai, A. Allelopathic effects of volatile monoterpenoids produced by Salvia leucophylla: Inhibition of cell proliferation and DNA synthesis in the root apical meristem of Brassica campestris seedlings. J. Chem. Ecol. 2005, 31, 1187–1203. [Google Scholar] [CrossRef]
  40. Dehsheikh, A.B.; Sourestani, M.M.; Dehsheikh, P.B.; Mottaghipisheh, J.; Vitalini, S.; Iriti, M. Monoterpenes: Essential oil components with valuable features. Mini Rev. Med. Chem. 2020, 20, 958–974. [Google Scholar] [CrossRef]
  41. Abrahim, D.; Francischini, A.C.; Pergo, E.M.; Kelmer-Bracht, A.M.; Ishii-Iwamoto, E.L. Effects of α-pinene on the mitochon-drial respiration of maize seedlings. Plant Physiol. Biochem. 2003, 41, 985–991. [Google Scholar] [CrossRef]
  42. Singh, H.P.; Batish, D.R.; Kaur, S.; Arora, K.; Kohli, R.K. alpha-Pinene inhibits growth and induces oxidative stress in roots. Ann. Bot. 2006, 98, 1261–1269. [Google Scholar] [CrossRef] [PubMed][Green Version]
  43. De Martino, L.; Mancini, E.; De Almeda, L.F.R.; De Feo, V. The antigerminative activity of twenty seven monoterpenes. Molecules 2010, 15, 6630–6637. [Google Scholar] [CrossRef] [PubMed][Green Version]
  44. Andrianjafinandrasana, S.N.; Andrianoelisoa, H.S.; Jeanson, M.L.; Ramonta, I.R.; Danthu, P. Allelopathic effects of volatile compounds of essential oil from Ravensara aromatica Sonnerat chemotypes. Allelopathy J. 2013, 31, 333–344. [Google Scholar]
  45. Wright, C.; Chhetri, B.K.; Setzer, W.N. Chemical composition and phytotoxicity of the essential oil of Encelia farinosa growing in the sonoran desert. Am. J. Essent. Oils Nat. Prod. 2013, 1, 18–22. [Google Scholar]
  46. Verma, R.S.; Joshi, N.; Padalia, R.C.; Singh, V.R.; Goswami, P.; Verma, S.K.; Iqbal, H.; Chanda, D.; Verma, K.; Darokar, M.P.; et al. Chemical composition and antibacterial, antifungal, allelopathic and acetylcholinesterase inhibitory activities of cassumunar-ginger. J. Sci. Food Agric. 2018, 98, 321–327. [Google Scholar] [CrossRef]
  47. Scognamiglio, M.; Schneider, B. Identification of potential allelochemicals from donor plants and their synergistic effects on the metabolome of Aegilops geniculata. Front. Plant Sci. 2020, 11, 1046. [Google Scholar] [CrossRef]
  48. Tahir, A.; Jilani, M.I.; Khera, R.A.; Nadeem, F. Juniperus communis: Biological activities and therapeutic potentials of a medicinal plant—A comprehensive study. Int. J. Chem. Biochem. Sci. 2016, 9, 85–91. [Google Scholar]
  49. Süntar, I.; Tumen, I.; Ustün, O.; Keleş, H.; Küpeli Akkol, E. Appraisal on the wound healing and anti-inflammatory activities of the essential oils obtained from the cones and needles of Pinus species by in vivo and in vitro experimental models. J. Ethnopharmacol. 2012, 139, 533–540. [Google Scholar] [CrossRef] [PubMed]
  50. Garzoli, S.; Masci, V.L.; Caradonna, V.; Tiezzi, A.; Giacomello, P.; Ovidi, E. Liquid and vapor Phase of four conifer-derived essential oils: Comparison of chemical compositions and antimicrobial and antioxidant properties. Pharmaceuticals 2021, 14, 134. [Google Scholar] [CrossRef]
  51. Hong, E.J.; Na, K.J.; Choi, I.G.; Choi, K.C.; Jeung, E.B. Antibacterial and antifungal effects of essential oils from coniferous trees. Biol. Pharm. Bull. 2004, 27, 863–866. [Google Scholar] [CrossRef][Green Version]
  52. Pérez-Rosés, R.; Risco, E.; Vila, R.; Peñalver, P.; Cañigueral, S. Biological and nonbiological antioxidant activity of some essential oils. J. Agric. Food Chem. 2016, 64, 4716–4724. [Google Scholar] [CrossRef] [PubMed]
  53. Emami, S.A.; Javadi, B.; Hassanzadeh, M.K. Antioxidant activity of the essential oils of different parts of Juniperus communis subsp. hemisphaerica. and Juniperus oblonga. Pharm. Biol. 2007, 4, 769–776. [Google Scholar] [CrossRef][Green Version]
  54. Emami, S.A.; Sadeghi-aliabadi, H.; Saeidi, M.; Jafarian, A. Cytotoxic evaluations of Iranian conifers on cancer cells. Pharm. Biol. 2005, 43, 299–304. [Google Scholar] [CrossRef] [PubMed][Green Version]
  55. Thi Hoai, N.; Viet Duc, H.; Thi Thao, D.; Orav, A.; Raa, A. Selectivity of Pinus sylvestris extract and essential oil to estrogen-insensitive breast cancer cells Pinus sylvestris against cancer cells. Pharmacogn. Mag. 2015, 11, S290. [Google Scholar]
  56. Maurya, A.K.; Devi, R.; Kumar, A.; Kundal, R.; Thakur, S.; Sharma, A.; Kumar, R.; Padwad, Y.S.; Chand, G.; Singh, B.; et al. Chemical composition, cytotoxic and antibacterial activities of essential oils of cultivated clones of Juniperus communis and wild Juniperus species. Chem. Biodivers. 2018, 15, e1800183. [Google Scholar] [CrossRef]
  57. Wedge, D.; Tabanca, N.; Sampson, B.; Werle, C.; Demirci, B.; Can Baser, K.H.; Nan, P.; Duan, J.; Liu, Z. Antifungal and insecticidal activity of two Juniperus essential oils. Nat. Prod. Commun. 2009, 4, 123–127. [Google Scholar]
  58. Semerdjieva, I.; Atanasova, D.; Maneva, V.; Zheljazkov, V.; Radoukova, T.; Astatkie, T.; Dincheva, I. Allelopathic effects of Juniper essential oils on seed germination and seedling growth of some weed seeds. Ind. Crops Prod. 2022, 180, 114768. [Google Scholar] [CrossRef]
  59. Ismail, A.; Lamia, H.; Mohsen, H.; Bassem, J. Herbicidal potential of essential oils from three mediterranean trees on different weeds. Curr. Bioact. Compd. 2012, 8, 3–12. [Google Scholar] [CrossRef]
  60. Muller, C.H.; del Moral, R. Soil toxicity induced by terpenes from Salvia leucophylla. Bull. Torrey Bot. Club. 1966, 93, 130–137. [Google Scholar] [CrossRef]
  61. Vitalini, S.; Iriti, M.; Garzoli, S. GC-MS and SPME-GC/MS Analysis and bioactive potential evaluation of essentia oils from two Viola species belonging to the V. calcarata complex. Separations 2022, 9, 39. [Google Scholar] [CrossRef]
  62. Al-Mudaris, M. Notes on various parameters recording the speed of seed germination. Der. Trop. 1998, 99, 147–154. [Google Scholar]
  63. Ellis, R.A.; Roberts, E.H. The quantification of ageing and survival in orthodox seeds. Seed Sci. Technol. 1981, 9, 373–409. [Google Scholar]
  64. Abdul-Baki, A.A.; Anderson, J.D. Vigour determination in soybean seed by multiple criteria. Crop Sci. 1973, 1, 630–633. [Google Scholar] [CrossRef]
Table 1. Chemical composition (percentages mean values ± standard deviation) of EO liquid and vapor phases.
Table 1. Chemical composition (percentages mean values ± standard deviation) of EO liquid and vapor phases.
Component 1LRI 2LRI 3Juniperus communis
EO 4
Juniperus communis
EO 5
Larix decidua
EO 6
Larix decidua
EO 7
1α-thujene8218234.2 ± 0.024.9 ± 0.060.3 ± 0.020.5 ± 0.03
2α-pinene94294319.0 ± 0.0410.3 ± 0.0351.0 ± 0.0563.3 ± 0.03
3camphene9459460.2 ± 0.02-1.4 ± 0.021.2 ± 0.01
4dehydrosabinene960956---0.4 ± 0.02
5sabinene97697237.5 ± 0.0334.5 ± 0.020.8 ± 0.021.0 ± 0.03
6β-pinene9859783.0 ± 0.0412.6 ± 0.032.3 ± 0.027.9 ± 0.02
7β-myrcene9909871.1 ± 0.03-9.7 ± 0.036.2 ± 0.02
8α-phellandrene100710050.7 ± 0.031.4 ± 0.030.3 ± 0.030.2 ± 0.07
93-carene10101008-0.9 ± 0.03--
10α-terpinene101210102.4 ± 0.065.8 ± 0.03--
11p-cymene102010161.2 ± 0.027.5 ± 0.051.1 ± 0.031.1 ± 0.01
12limonene102610235.8 ± 0.0314.0 ± 0.073.9 ± 0.064.5 ± 0.02
13β-ocimene10291024--10.2 ± 0.0410.2 ± 0.02
141,8-cineole10301025--3.2 ± 0.061.9 ± 0.05
15γ-terpinene105310545.0 ± 0.041.0 ± 0.020.5 ± 0.030.3 ± 0.02
16terpinolene108210802.6 ± 0.034.3 ± 0.061.0 ± 0.040.5 ± 0.03
17p-cymenene10931091--0.3 ± 0.020.1 ± 0.01
18α-campholenal11271125--0.3 ± 0.03-
19trans-pinocarveol11371134--1.1 ± 0.020.3 ± 0.03
20pinocarvone11491145--0.2 ± 0.02-
21borneol11601155--0.2 ± 0.03-
22terpinen-4-ol116511604.2 ± 0.022.7 ± 0.020.8 ± 0.020.1 ± 0.02
23α-terpineol118211830.2 ± 0.01-0.4 ± 0.02-
24carveol12021201---0.1 ± 0.02
25cuminal12151211--0.1 ± 0.01-
26phellandral12551249--0.1 ± 0.04-
27bornyl acetate129412900.3 ± 0.02-2.6 ± 0.070.1 ± 0.01
284-terpinenyl acetate130713040.1 ± 0.01-0.8 ± 0.02-
29α-terpinyl acetate133613330.4 ± 0.03---
30α-cubebene135213480.2 ± 0.03---
31copaene139013850.3 ± 0.02-0.1 ± 0.02-
32β-elemene140814061.8 ± 0.05-0.1 ± 0.02-
33longifolene14101408--0.2 ± 0.02tr
34β-caryophyllene142714241.3 ± 0.03-2.2 ± 0.07tr
35cis-thujopsene143814352.1 ± 0.03---
36humulene147114650.8 ± 0.04-0.7 ± 0.03-
37γ-muurolene149014860.5 ± 0.02-0.3 ± 0.02-
38germacrene D15,00115000.1 ± 0.02-0.5 ± 0.05-
39α-muurolene1507*1.0 ± 0.02-0.5 ± 0.02-
40guaia-1(10), 11-diene150915050.3 ± 0.02---
41δ-cadinene153315302.4 ± 0.03---
42α-cadinene1539*--0.1 ± 0.02-
43α-calacorene15411539--0.1 ± 0.02-
44spathulenol157615710.1 ± 0.02---
45caryophyllene oxide161616130.1 ± 0.02-0.2 ± 0.02-
46epicubenol162016180.1 ± 0.02---
47humulene epoxide II1622*--0.1 ± 0.02-
48δ-cadinol1627*--0.2 ± 0.01-
49τ-cadinol16301625--0.1 ± 0.02-
50τ-muurolol164116390.6 ± 0.02---
51α-cadinol167816760.4 ± 0.03---
SUM 100.099.997.999.9
Terpenoids 87.699.989.699.7
Sesquiterpenoids 11.8-5.1-
Others 0.6-3.20.2
1 The components are reported according to their elution order on apolar column; 2 Linear Retention indices measured on apolar column; 3 Linear Retention indices from literature; * LRI not available; 4 Percentage values of J. communis liquid phase components; 5 Percentage values of J. communis vapor phase components; 6 Percentage values of L. decidua liquid phase components; 7 Percentage values of L. decidua vapor phase components; - Not detected; tr: traces (mean value < 0.1%).
Table 2. Chemical composition (percentage mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in non-direct contact with J. communis EO.
Table 2. Chemical composition (percentage mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in non-direct contact with J. communis EO.
Component 1LRI 2LRI 3Soil 4Soil 5Soil 6Soil 7
1α-thujene8218234.2 ± 0.020.1 ± 0.024.0 ± 0.033.7 ± 0.03
2α-pinene94294319.0 ± 0.050.4 ± 0.0220.4 ± 0.021.2 ± 0.02
3Sabinene9769722.5 ± 0.02-3.2 ± 0.023.2 ± 0.02
4α-terpinene101210105.1 ± 0.020.3 ± 0.024.5 ± 0.026.0 ± 0.06
5p-cymene102010169.0 ± 0.020.6 ± 0.034.8 ± 0.046.5 ± 0.03
6Limonene102610234.9 ± 0.020.3 ± 0.022.9 ± 0.024.6 ± 0.02
7γ-terpinene105310546.3 ± 0.020.3 ± 0.046.5 ± 0.027.8 ± 0.02
8Terpinolene108210802.2 ± 0.021.0 ± 0.06--
9α-cubebene13521348-2.3 ± 0.020.5 ± 0.032.1 ± 0.01
10Copaene139013850.3 ± 0.022.8 ± 0.020.9 ± 0.023.2 ± 0.02
11β-elemene140814069.7 ± 0.0212.9 ± 0.027.1 ± 0.0213.7 ± 0.02
12β-caryophyllene142714241.6 ± 0.024.2 ± 0.032.1 ± 0.024.4 ± 0.01
13cis-thujopsene1438143530.2 ± 0.0226.7 ± 0.0440.5 ± 0.0332.2 ± 0.02
14Humulene147114651.5 ± 0.022.1 ± 0.021.0 ± 0.053.0 ± 0.02
15γ-muurolene14901486-4.9 ± 0.04--
17α-muurolene1507*-1.9 ± 0.04--
16δ-cadinene153315300.6 ± 0.0410.6 ± 0.020.3 ± 0.022.6 ± 0.01
18τ-muurolol16411639-0.9 ± 0.02--
19α-cadinol167816762.9 ± 0.0227.7 ± 0.041.2 ± 0.025.6 ± 0.02
SUM 100.0100.099.999.8
Terpenoids 53.23.046.333.0
Sesquiterpenoids 46.594.252.763.6
Others 0.32.80.93.2
1 The components are reported according to their elution order on apolar column 2 Linear Retention indices measured on apolar column; 3 Linear Retention indices from literature; * LRI not available; 4 Percentage mean values of the volatiles from soil with 20 µL of J. communis EO and L. multiflorum seeds; 5 Percentage values of the volatiles from soil with 20 µL of J. communis EO and S. alba seeds; 6 Percentage mean values of the volatiles from soil with 50 µL of J. communis EO and L. multiflorum seeds; 7 Percentage mean values of the volatiles from soil with 50 µL of J. communis EO and S. alba seeds; - Not detected.
Table 3. Chemical composition (percentages mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in non-contact with L. decidua EO.
Table 3. Chemical composition (percentages mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in non-contact with L. decidua EO.
Component 1LRI 2LRI 3Soil 4Soil 5Soil 6Soil 7
1α-pinene94294387.7 ± 0.0537.8 ± 0.0372.5 ± 0.0366.7 ± 0.05
2β-pinene9859784.6 ± 0.023.3 ± 0.022.8 ± 0.037.1 ± 0.02
3β-myrcene9909877.7 ± 0.0210.2 ± 0.0312.6 ± 0.0319.1 ± 0.02
4β-ocimene10291024-13.8 ± 0.037.7 ± 0.024.6 ± 0.02
5β-caryophyllene14271424-34.9 ± 0.044.4 ± 0.022.5 ± 0.03
SUM 100.0100.0100.0100.0
1 The components are reported according to their elution order on apolar column 2 Linear Retention indices measured on apolar column; 3 Linear Retention indices from literature; 4 Percentage mean values of the volatiles from soil with 20 µL of L. decidua EO and L. multiflorum seeds; 5 Percentage mean values of the volatiles from soil with 20 µL of L. decidua EO and S. alba seeds; 6 Percentage mean values of the volatiles from soil with 50 µL of L. decidua EO and L. multiflorum seeds; 7 Percentage mean values of the volatiles from the soil with 50 µL of L. decidua EO and S. alba seeds; - Not detected.
Table 4. Chemical composition (percentages mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in contact with J. communis EO.
Table 4. Chemical composition (percentages mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in contact with J. communis EO.
Component 1LRI 2LRI 3Soil 4Soil 5Soil 6Soil 7
1α-thujene821823-100.0 ± 0.0242.2 ± 0.0387.9 ± 0.03
2β-elemene14081406--17.4 ± 0.0212.1 ± 0.02
3cis-thujopsene14381435--40.4 ± 0.03-
SUM 100.0100.0100.0
1 The components are reported according to their elution order on apolar column 2 Linear Retention indices measured on apolar column; 3 Linear Retention indices from literature; 4 Percentage mean values of the volatiles from soil with 5 µL of J. communis EO and L. multiflorum seeds; 5 Percentage mean values of the volatiles from soil with 5 µL of J. communis EO and S. alba seeds; 6 Percentage mean values of the volatiles from soil with 10 µL of J. communis EO and L. multiflorum seeds; 7 Percentage mean values of the volatile from soil with 10 µL of J. communis EO and S. alba seeds; - Not detected.
Table 5. Chemical composition (percentages mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in direct contact with L. decidua EO.
Table 5. Chemical composition (percentages mean values ± standard deviation) of soil samples with L. multiflorum and S. alba seeds in direct contact with L. decidua EO.
Component 1LRI 2LRI 3Soil 4Soil 5Soil 6Soil 7
1α-pinene94294396.4 ± 0.0593.7 ± 0.0388.9 ± 0.0381.8 ± 0.05
2β-pinene9859783.6 ± 0.024.7 ± 0.0211.1 ± 0.0318.2 ± 0.02
3β-myrcene990987-1.6 ± 0.03--
SUM 100.0100.0100.0100.0
1 The components are reported according to their elution order on apolar column 2 Linear Retention indices measured on apolar column; 3 Linear Retention indices from literature; 4 Percentage mean values of the volatiles from soil with 5 µL of L. decidua EO and L. multiflorum seeds; 5 Percentage mean values of the volatiles from soil with 5 µL of L. decidua EO and S. alba seeds; 6 Percentage mean values of the volatiles from soil with 10 µL of L. decidua EO and L. multiflorum seeds; 7 Percentage mean values of the volatiles from soil with 10 µL of L. decidua EO and S. alba seeds; - Not detected.
Table 6. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using filter paper as a substrate.
Table 6. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using filter paper as a substrate.
Target SpeciesEO
(µL)
G
(%)
CVGMGTSVIRoot
(mm)
Shoot
(mm)
Juniperus communisvar. saxatilis
Lolium
multiflorum
093.3 ± 5.3 a89.8 ± 9.0 a5.1 ± 0.1 a11,064 ± 306 a72.3 ± 6.5 a46.6 ± 2.0 a
280.3 ± 9.4 b67.7 ± 6.6 b5.1 ± 0.1 a5129 ± 720 b41.5 ± 4.5 b22.3 ± 3.2 b
2035.0 ± 8.5 c21.5 ± 7.0 c5.4 ± 0.2 b772 ± 314 c15.7 ± 3.6 c5.8 ± 0.7 c
500.0 ± 0.0 dn.d.n.d.n.d.n.d.n.d.
F154.856157.2881721.960580.626214.413476.953
p-value0.000 *0.000 *0.000 *0.000 *0.000 *0.000 *
Sinapis
alba
083.3 ± 8.7 a102.6 ± 13.9 a4.3 ± 0.1 a4522 ± 301 a30.9 ± 2.5 a23.6 ± 1.6 a
278.5 ± 8.3 a89.9 ± 13.1 a4.3 ± 0.1 a3711 ± 354 b29.3 ± 3.2 a18.1 ± 1.6 b
2070.0 ± 8.5 a85.7 ± 15.8 a4.4 ± 0.1 a2195 ± 120 c18.6 ± 3.3 b13.0 ± 0.9 c
5035.0 ± 6.3 b26.8 ± 3.0 b4.8 ± 0.2 b349 ± 99 d3.0 ± 0.6 c6.8 ± 0.9 d
F29.70228.9039.183225.38696.659121.614
p-value0.0000.0000.0020.0000.0000.000
Interaction species × treatment
F20.39810.168749.786209.78268.815150.270
p-value0.000 *0.000 *0.000 *0.000 *0.000 *0.000 *
Larix decidua
090.0 ± 3.5 a92.0 ± 3.2 a 5.0 ± 0.2 a10,450 ± 116 a68.6 ± 1.4 a47.5 ± 3.4 a
Lolium
multiflorum
263.0 ± 8.2 b46.8 ± 6.9 b5.2 ± 0.1 ab2662 ± 590 b20.0 ± 1.6 b21.9 ± 3.1 b
2054.0 ± 15.4 b28.3 ± 9.9 c5.5 ± 0.3 b907 ± 366 c3.6 ± 1.3 c13.0 ± 1.5 c
500.0 ± 0.0 cn.d.n.d.n.d.n.d.n.d.
F71.962151.869814.006731.6392514.839275.249
p-value0.000 *0.000 *0.000 *0.000 *0.000 *0.000 *
Sinapis
alba
083.3 ± 11.6 a106.0 ± 17.6 a4.3 ± 0.1 a3440 ± 891 a20.0 ± 4.3 a20.9 ± 3.5 a
281.8 ± 6.7 a101.0 ± 13.9 a4.4 ± 0.0 b2734 ± 537 a18.2 ± 5.4 a15.5 ± 2.2 b
2071.8 ± 11.5 a72.3 ± 16.1 b4.8 ± 0.0 c2444 ± 525 a17.5 ± 0.9 a16.4 ± 2.3 b
500.0 ± 0.0 bn.d.n.d.n.d.n.d.n.d.
F81.15950.0676953.42926.37728.49559.168
p-value0.000 *0.000 *0.000 *0.000 *0.000 *0.000 *
Interaction species × treatment
F4.16411.15915.836127.252215.13963.298
p-value0.017 *0.000 *0.000 *0.000 *0.000 *0.000 *
Values are mean ± standard deviation; asterisk and different letters indicate statistically significant differences at p-value ≤ 0.05 among treatments in each species. F-value and p-value of the ANOVA test. Abbreviations: G%, Germination percentage; CVG, Coefficient of Velocity of Germination; MGT, Mean Germination Time, SVI, Seedling Vigor Index.
Table 7. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using soil as a substrate.
Table 7. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using soil as a substrate.
Target SpeciesEO
(µL)
G
(%)
CVGMGTShoot
(mm)
Juniperus communisvar. saxatilis
Lolium
multiflorum
086.8 ± 5.392.0 ± 5.8 a4.7 ± 0.1 a73.1 ± 2.2 a
278.3 ± 6.782.0 ± 11.6 a4.8 ± 0.1 a66.6 ± 2.8 b
2076.5 ± 4.071.5 ± 5.3 a5.0 ± 0.2 b65.6 ± 3.6 b
5063.3 ± 20.146.5 ± 19.2 b5.3 ± 0.0 c49.0 ± 4.9 c
F3.07310.65219.88634.017
p-value0.0690.001 *0.000 *0.000 *
Sinapis
alba
088.5 ± 3.0 a101.5 ± 6.5 a4.4 ± 0.1 a29.8 ± 1.1 a
275.3 ± 9.9 b75.2 ± 11.2 b4.4 ± 0.1 ab29.4 ± 1.3 a
2065.0 ± 6.3 b72.5 ± 1.9 b4.6 ± 0.1 ab24.5 ± 1.6 b
5065.0 ± 6.3 b68.6 ± 5.5 b4.7 ± 0.1 b22.2 ± 1.4 b
F10.64918.2795.74230.647
p-value0.001 *0.000 *0.011 *0.000 *
Interaction species × treatment
F0.9213.1654.78715.100
p-value0.4460.043 *0.009 *0.000 *
Larix decidua
Lolium
multiflorum
088.0 ± 10.0 a93.3 ± 12.4 a4.9 ± 0.1 a72.1 ± 2.8 a
286.5 ± 7.5 a82.3 ± 16.1 a5.0 ± 0.1 a69.3 ± 2.8 a
2056.8 ± 8.7 b55.2 ± 8.1 b4.9 ± 0.0 a44.4 ± 3.6 b
5048.3 ± 5.5 b36.6 ± 6.0 b5.2 ± 0.2 b29.3 ± 3.2 c
F25.38820.4685.965176.381
p-value0.000 *0.000 *0.010 *0.000 *
Sinapis
alba
076.5 ± 7.0 a80.5 ± 11.3 a4.6 ± 0.1 a30.5 ± 1.1 a
276.8 ± 8.7 a77.8 ± 10.5 a4.6 ± 0.0 a31.3 ± 0.7 a
2068.5 ± 3.0 a68.5 ± 6.2 a4.7 ± 0.1 a23.3 ± 2.0 b
5043.5 ± 7.0 b32.0 ± 4.9 b5.1 ± 0.1 b17.5 ± 2.0 c
F21.63427.27330.00069.892
p-value0.000 *0.000 *0.000 *0.000 *
Interaction species × treatment
F4.0552.3570.58366.368
p-value0.018 *0.0970.6320.000 *
Values are mean ± standard deviation; asterisk and different letters indicate statistically significant differences at p-value ≤ 0.05 among treatments in each species. F-value and p-value of the ANOVA test. Abbreviations: G%, Germination percentage; CVG, Coefficient of Velocity of Germination; MGT, Mean Germination Time.
Table 8. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using filter paper as a substrate.
Table 8. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using filter paper as a substrate.
Target
Species
EO
(µL/mL)
G
(%)
CVGMGTSVIRoot
(mm)
Shoot
(mm)
Juniperus communisvar. saxatilis
Lolium
multiflorum
090.0 ± 3.5 a84.8 ± 4.6 a5.0 ± 0.1 a7037 ± 568 a42.9 ± 3.3 a35.2 ± 0.5 a
253.5 ± 13.0 b37.1 ± 14.7 b5.4 ± 0.1 b2632 ± 678 b34.9 ± 2.9 b14.4 ± 3.8 b
531.8 ± 13.9 c17.8 ± 8.9 c5.4 ± 0.2 b1020 ± 660 c20.4 ± 6.7 c9.3 ± 2.0 c
100.0 ± 0.0 dn.d.n.d.n.d.n.d.n.d.
F61.33068.4392630.647126.72788.602187.572
p-value0.000 *0.000 *0.000 *0.000 *0.000 *0.000 *
Sinapis
alba
081.8 ± 6.7 a103.8 ± 9.4 a4.3 ± 0.1 a2780 ± 361 a16.8 ± 1.9 a17.2 ± 1.7 a
249.8 ± 8.3 b41.9 ± 9.9 b4.5 ± 0.2 ab1686 ± 326 b20.6 ± 1.9 b13.2 ± 0.7 b
539.8 ± 13.5 b35.2 ± 3.7 b4.9 ± 0.3 b705 ± 165 c7.7 ± 1.2 c10.4 ± 2.1 b
1038.3 ± 3.5 b31.6 ± 16.9 b5.0 ± 0.2 b683 ± 155 c7.3 ± 2.3 c10.5 ± 1.1 b
F21.25337.0247.72855.02951.47017.225
p-value0.000 *0.000 *0.004 *0.000 *0.000 *0.000 *
Interaction species × treatment
F10.2972.403460.77848.70639.57279.502
p-value0.000 *0.0920.000 *0.000 *0.000 *0.000 *
Larix decidua
091.5 ± 3.0 a84.0 ± 8.3 a5.2 ± 0.1 a8338 ± 714 a49.4 ± 3.6 a41.7 ± 3.9 a
Lolium
multiflorum
251.5 ± 12.8 b31.2 ± 8.9 b5.5 ± 0.1 b2227 ± 824 b16.6 ± 5.7 b36.2 ± 8.2 b
50.0 ± 0.0 cn.d.n.d.n.d.n.d.n.d.
100.0 ± 0.0 cn.d.n.d.n.d.n.d.n.d.
F183.326169.51315,155.667208.653191.104214.739
p-value0.000 *0.000 *0.000 *0.000 *0.000 *0.000 *
Sinapis
alba
071.8 ± 6.2 a76.3 ± 6.6 a4.5 ± 0.2 a2892 ± 288 a16.9 ± 1.3 a23.4 ± 1.8 a
266.5 ± 12.2 a62.4 ± 21.3 a4.9 ± 0.2 b2029 ± 461 b14.0 ± 2.5 a16.3 ± 1.3 ab
564.8 ± 9.9 a56.3 ± 11.1 a5.0 ± 0.1 b1610 ± 315 b9.7 ± 2.4 b15.3 ± 2.1 b
1018.3 ± 6.7 b12.8 ± 5.5 b5.0 ± 0.2 b252 ± 108 c9.2 ± 1.9 b18.3 ± 6.7 ab
F29.87118.4097.44647.66612.2023.851
p-value0.000 *0.000 *0.004 *0.000 *0.001 *0.038 *
Interaction species × treatment
F38.21914.8911426.05696.10899.85660.698
p-value0.000*0.000 *0.000 *0.000 *0.000 *0.000 *
Values are mean ± standard deviation; asterisk and different letters indicate statistically significant differences at p-value ≤ 0.05 among treatments in each species. F-value and p-value of the ANOVA test. Abbreviations: G%, Germination percentage; CVG, Coefficient of Velocity of Germination; MGT, Mean Germination Time, SVI, Seedling Vigor Index.
Table 9. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using soil as a substrate.
Table 9. Germination and growth values of two target species (Lolium multiflorum and Sinapis alba) under the phytotoxic effects of different doses of Juniperus communis var. saxatilis and Larix decidua EOs using soil as a substrate.
Target
Species
EO
(µL/mL)
G
(%)
CVGMGTShoot
(mm)
Juniperus communisvar. saxatilis
Lolium
multiflorum
098.3 ± 3.5 a112.8 ± 11.5 a4.8 ± 0.1 a71.7 ± 3.2 a
283.5 ± 4.0 b88.8 ± 9.4 b4.8 ± 0.1 a69.6 ± 3.6 a
556.5 ± 13.8 c47.5 ± 18.3 c5.2 ± 0.0 a66.9 ± 1.3 a
1045.3 ± 3.5 c26.0 ± 9.2 c5.6 ± 0.4 b43.0 ± 8.7 b
F41.00238.91314.51028.223
p-value0.000 * 0.000 * 0.000 * 0.000 *
Sinapis
alba
093.3 ± 5.5 a115.2 ± 13.7 a4.5 ± 0.1 a28.3 ± 0.5 a
283.5 ± 4.0 ab80.0 ± 4.7 b4.8 ± 0.1 b28.1 ± 3.6 a
570.0 ± 14.1 b63.2 ± 13.6 b5.0 ± 0.0 c22.4 ± 1.9 b
1035.0 ± 12.3 c25.7 ± 11.0 c5.0 ± 0.1 c18.3 ± 1.4 c
F26.27343.25025.82619.860
p-value0.000 * 0.000 * 0.000 * 0.000 *
Interaction species × treatment
F2.6551.4364.68811.654
p-value0.0710.2570.010 * 0.000 *
Larix decidua
Lolium
multiflorum
090.0 ± 8.5 a102.3 ± 19.0 a4.7 ± 0.0 a72.1 ± 3.4 a
271.8 ± 9.9 b68.0 ± 3.3 b4.9 ± 0.0 ab59.6 ± 2.8 b
2071.5 ± 3.0 b57.1 ± 16.0 bc5.2 ± 0.5 ab57.0 ± 2.8 b
5044.8 ± 9.9 c35.0 ± 14.6 c5.4 ± 0.1 c29.5 ± 11.2 c
F19.88115.1004.69633.525
p-value0.000 * 0.000 * 0.022 * 0.000 *
Sinapis
alba
081.8 ± 3.5 a96.0 ± 9.5 a4.5 ± 0.1 a31.2 ± 2.1 a
271.5 ± 8.3 ab64.5 ± 11.1 ab5.1 ± 0.1 b25.9 ± 2.2 b
2058.3 ± 17.3 ab48.5 ± 25.2 b5.1 ± 0.3 b20.4 ± 0.7 c
5050.0 ± 16.7 c40.1 ± 19.1 b5.0 ± 0.1 b18.7 ± 2.1 c
F4.7998.0608.89236.371
p-value0.020 * 0.003 * 0.002 * 0.000 *
Interaction species × treatment
F1.1551.1401.38717.195
p-value0.3470.3530.2710.000 *
Values are mean ± standard deviation; asterisk and different letters indicate statistically significant differences at p-value ≤ 0.05 among treatments in each species. F-value and p-value of the ANOVA test. Abbreviations: G%, Germination percentage; CVG, Coefficient of Velocity of Germination; MGT, Mean Germination Time.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Vitalini, S.; Iriti, M.; Vaglia, V.; Garzoli, S. Chemical Investigation and Dose-Response Phytotoxic Effect of Essential Oils from Two Gymnosperm Species (Juniperus communis var. saxatilis Pall. and Larix decidua Mill.). Plants 2022, 11, 1510. https://doi.org/10.3390/plants11111510

AMA Style

Vitalini S, Iriti M, Vaglia V, Garzoli S. Chemical Investigation and Dose-Response Phytotoxic Effect of Essential Oils from Two Gymnosperm Species (Juniperus communis var. saxatilis Pall. and Larix decidua Mill.). Plants. 2022; 11(11):1510. https://doi.org/10.3390/plants11111510

Chicago/Turabian Style

Vitalini, Sara, Marcello Iriti, Valentina Vaglia, and Stefania Garzoli. 2022. "Chemical Investigation and Dose-Response Phytotoxic Effect of Essential Oils from Two Gymnosperm Species (Juniperus communis var. saxatilis Pall. and Larix decidua Mill.)" Plants 11, no. 11: 1510. https://doi.org/10.3390/plants11111510

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop