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Potential allelopathic effects of volatile oils from Descurainia sophia (L.) Webb ex Prantl on wheat
Abstract
Allelopathic effect of saturated aqueous solution of the volatile oil from Descurainia sophia on seedling growth of test wheat cultivars and the effect on the microbial populations of the soil underneath wheat cultivars (A: Duokang 1; B: Fengyuan 1; C: Zhongmai 1; D: Baomai 1; E: Huaimai 20; F: Zhou 16; G: Zhou 18; H: Wen 10).Figure optionsView in workspace
Research highlights
► Terpenoids in Descurainia sophia (L.) volatiles inhibited wheat seeds germination. ► Terpenoids in D. sophia volatiles inhibited wheat seedling growth. ► Terpenoids in D. sophia decreased soil microbial counts. ► Responses to the phytotoxicity of D. sophia volatiles were different among cultivars. ► Allelopathic potential of D. sophia volatile compounds can be mediated by soil.
... Plant extracts with allelopathic effects cause an increase in superoxide (O2-), hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals, which results in damage to DNA, proteins, and cell membranes (Duke, 2010). Electrolytic leakage induces endonucleases, proteases and programmed cell death, which inhibit growth (Li et al., 2011) and necrosis in weeds (Travaini et al., 2016). ...
... There are several natural compounds with potential for the use of weeds, such as essential oils from the flora Descurainia sophia (L.) (Li et al., 2011), Lippia menosides (Marco et al., 2012) and Dodonaea viscosa (Rowshan, Farhadi, & Najafian, 2014), which presents as main components or thymol and carvacrol. Kordali et al. (2008) working with Origanum acutidens essential oil associated to the presence of carvacrol and thymol inhibiting seed germination and seedling growth of A. retroflexus, Chenopodium album and Rumex crispus species. ...
Biological herbicides or bioherbicides can reduce the use of synthetic herbicides and minimise the negative environmental impact of them. To be successful, bioherbicides must have a competitive price, efficiency and consistency. In this review, the highest level of development, and the future prospects for herbicides of biological origin are reported and discussed. Application of bioherbicides allows the reduction of fertilisers and environmental contamination and, at the same time, increases the tolerance of plants to biotic and abiotic stresses, as well as, they are used to suppress weeds that are difficult to control and those resistant to herbicides. Another promising line of research in Brazil is the one that deals with bioherbicide based on phytopathogens, combined with adjuvants in a formulation that can increase herbicidal activity. Therefore, the development of new herbicides is of great importance, because the effectiveness of the commercially available ones is decreasing drastically, and the chemical control of weeds still remains the most widespread agronomic practice.
... One of the products of secondary metabolism is essential oils, that are oily and volatile liquids distributed in leaves, fruits, seeds, or roots in several plant species. These oils generally present an intense and pleasant aroma, so they are also called essences, volatile oils, and because they are soluble in apolar solvents, such as ethers, they are also called ethereal oils (Li et al. 2011). The production of essential oils in the plants is involved with their protection against microorganisms, insects, and herbivores. ...
... The essential oils are potent inhibitors of seed germination and interfere in the development of several plant species, considered important and possible alternatives to be used as bioherbicides. The literature presents many works related to the study of essential oils that have proven activity against weed species (Li et al. 2011;Pinheiro et al. 2013;Rowshan et al. 2014;Pinheiro et al. 2015). ...
The use of allelopathic compounds is an alternative for weeds control, since they present low toxicity when compared with the synthetic herbicides, that may cause several damages, as the contamination of the environment. Our objective was to determine the chemical composition and allelopathic properties of the essential oils of Psidium cattleianum, P. myrtoides, P. friedrichsthalianum, and P. gaudichaudianum on the germination and root growth of Lactuca sativa and Sorghum bicolor, and to evaluate their action on the cell cycle of root meristematic cells of L. sativa. The main compound found in all the studied species was (E)-caryophyllene (P. cattleianum—23.4 %; P. myrtoides—19.3%; P. friedrichsthalianum—24.6% and P. gaudichaudianum—17.0%). The different essential oils were tested at different concentrations on L. sativa and S. bicolor, reducing germination, germination speed index, and root and shoot growth of lettuce and sorghum seedlings. The cytotoxicity and aneugenic potential of these oils were evidenced by the reduction of the mitotic index and increase of the frequency of chromosomal alterations in L. sativa. The essential oils of the species of Psidium studied have potential to be used in weeds control.
... On the other hand, the inhibition of the hypocotyl growth varied from 34.6 (at 0.1 mg/ml ; EO2) to 100% (at 1 mg/ml, all oils) and that of the radicle from 22.7 to 100%. The inhibitory activity of the Tunisian T. algeriensis essential oils on T. aestivum seedlings was greater than that of Descurainia sophia (Li et al., 2011) andThymus numidicus (Ben El Hadj Ali et al., 2014). ...
... In line with our findings, few studies reported that some essential oils containing toxic compounds (e.g., limonene, caryophyllene oxide, spatulenol, etc.) also have interesting phytotoxic potentials (Chung et al., 2001;Mabrouk et al., 2013). Furthermore, several authors suggested that monoterpene compounds had shown strong inhibitory effects on seeds germination of many crops and weeds (Li et al., 2011;López et al., 2009). The bioassay results reported here demonstrated that the volatile oils of T. algeriensis possess strong phytotoxic potential and could cause substantial germination reduction and seedling growth inhibition of M. sativa and T. aestivum. ...
... Additionally, the phytotoxic activity of A. tibetica EO could be ascribed to the diversity of chemical constituents in A. tibetica EO, especially the monoterpene compounds (79.05%) compared with sesquiterpenes (10.33%), which were the main class of terpenoids in A. tibetica EO. Some earlier studies reported that monoterpenes, including monoterpene hydrocarbons and oxygenated monoterpenes, suppressed the growth of many crops and weeds (Lopez et al., 2008;Li et al., 2011;Ali et al., 2015); it was also reported that the phytotoxic activity of oxygenated monoterpenes could be much stronger than that of monoterpene hydrocarbons Amri et al., 2017). Moreover, it was confirmed that the monoterpenes camphor (29.76%) and eucalyptol (12.07%), the main compounds of A. tibetica EO, exhibited phytotoxic activity against the tested plants in previous reports (Shao et al., 2018). ...
The chemical profile of Ajania tibetica essential oil (EO) and its phytotoxic, insecticidal, and antimicrobial activities were assessed. Monoterpenes (79.05%) and sesquiterpenes (10.33%) were dominant in the EO, with camphor, (+/-)-lavandulol and eucalyptol being the major constituents, representing 55.06% of the total EO. The EO possessed potent phytotoxicity against Poa annua and Medicago sativa starting from 0.5 mg/mL, and when the concentration rose to 5 mg/mL, seed germination of both tested species was 100% suppressed. Ajania tibetica EO displayed significant pesticidal activity against Aphis gossypii with an LC 50 value of 17.41 μg/mL; meanwhile, the EO also showed antimicrobial activity against Escherichia coli , Bacillus subtilis , Verticillium dahlia and Aspergillus niger using broth microdilution and disc diffusion methods. For the tested bacterial and fungal strains, the EO exhibited a repressing effect, with minimum inhibitory concentrations (MICs) ranging from 0.3125 to 1.25 mg/mL for bacteria and from 1.25 to 2.5 mg/mL for fungi, whereas the minimum microbicidal concentrations (MMCs) were 5 mg/mL for bacteria and 2.5 mg/mL for fungi. Our study is the first report on the chemical profile as well as the phytotoxicity, insecticidal and antimicrobic activity of A. tibetica EO, indicating its potential value as an alternative synthetic pesticide.
... The phytotoxic effect of a particular EO can be mainly ascribed to certain toxic component(s). Monoterpene compounds have been reported to show strong inhibitory effects on the seed germination of many crops and weeds (López et al., 2008;Li et al., 2011;Ali et al., 2015). The outstanding phytotoxic activity of thymol has been previously studied. ...
For several decades, the control of plant diseases and pests were mainly based on the frequent use of pesticides. However, as science advances, the importance of mitigating the exposure of plants, animals, and humans to hazardous chemicals is better understood. Many conventional synthetic pesticides have become of concern, even if they are presumed to have reached the required level of "safety". The repeated and continuous use of pesticides based on the same active ingredient considerably promotes the development of resistant populations of harmful organisms, resulting in an additional need for pesticides.
Plant derivatives represent effective alternatives to synthetic chemicals and provide very promising results. It is now widely recognized that certain fungal, bacterial, nematode, weed, and insect control agents derived from plants can be developed into commercial products suitable for integrated pest management. Plant extracts and essential oil-based pesticide products are selective in their target, while no harm is made to non-target organisms and the environment. These pesticides act differently depending on the types of plant pathogens and pests and can be applied to the plant in the same way as conventional pesticides. Many plant extracts and essential oils are already screened for their effectiveness against a wide range of pathogens and pests, further confirmed by field studies.
... The phytotoxic effect of a particular EO can be mainly ascribed to certain toxic component(s). Monoterpene compounds have been reported to show strong inhibitory effects on the seed germination of many crops and weeds (López et al., 2008;Li et al., 2011;Ali et al., 2015). The outstanding phytotoxic activity of thymol has been previously studied. ...
The chemical profile of Thymus proximus essential oil (EO) and its allelopathic, phytotoxic, and insecticidal activity was evaluated. Carvacrol, p-cymene, and γ-terpinene were detected as the major components of the EO, representing 85.9% of the total oil. About 50 g fresh plant material of T. proximus in a 1.5-L air tight container completely inhibited the seed germination of Amaranthus retroflexus and Poa anuua . Meanwhile, the EO exhibited potent phytotoxic activity, which resulted in 100% germination failure of both the test species when 2 mg/ml (for A. retroflexus ) and 5 mg/ml (for Poa annua ) oil was applied. The EO also triggered a significant insecticidal activity on Aphis gossypii with a LC 50 value of 6.34 ppm. Carvacrol was identified as the main active compound responsible for both the plant suppressing effect and the insecticidal activity of the EO. Our study is the first on the allelopathic, phytotoxic, and insecticidal activity of T. proximus EO, and the determination of the responsible compound, which indicated their potential of being further explored as environment friendly biopesticides.
... Furthermore, several researchers have shown that monoterpene compounds have strong inhibitory effects on seed germination of many crops and weeds. (Lopez, Bonzani, Zygadlo, 2009;Li et al., 2011). The bioassay results, reported here, demonstrated that the volatile oil of R. acaule possesses strong phytotoxic potential and could cause substantial germination reduction and seedling growth inhibition of L. sativa. ...
The in-vitro antioxidant activity of Rhaponticum acaule essential oil (RaEO) was evaluated using β-carotene/linoleic acid bleaching, chelating activity, and lipid peroxidation inhibition (TBARS) assays. The antimicrobial activity of RaEO was assessed by disc diffusion and microdilution methods against 8 bacteria and 4 yeast. Finally, the allelopathic activity of RaEO on the seed germination and the shoot and root elongation of lettuce (Lactuca sativa L.) seedlings were investigated. According to our results, the RaEO exhibited significant antioxidant activity, similar to those of standards (BHT and ascorbic acid) with IC50 values of 0.042 and 0.045 mg/mL obtained by β-carotene bleaching and TBARS assays, respectively. On the other hand, despite its interesting ferrous chelating activity, RaEO possesses moderate IC50 value (0.35 mg/mL) as compared with that of EDTA (0.015 mg/mL). RaEO exhibited a strong antimicrobial activity against all the tested microorganisms, with IZ, MIC and MBC values being in the range of 7.67 ± 0.58 to 13.33 ± 0.58 mm, 1.25 to 5.00 and 5.00 to 10.00 mg/mL, respectively. The results reveled also that RaEO inhibited the shoot and root growth of Lactuca sativa L. seedlings. Our data suggested that the RaEO had pharmaceutical benefits and could be used as a potential natural herbicide resource.
... These chemicals are products of the secondary metabolism and are non-nutritional primary metabolites [5][6] which are not necessary for development and reproduction of the allelopathic organism. The impact of allelochemicals compounds on germination, growth and development of plants is regulated by their complexity, interaction and concentration [7][8]. ...
The current study evaluate the effect of aqueous extract from the shoot of Alhagi maurorum at different rates
(0.01, 0.05, 0.10, 0.15 %, w/v) on some physiological parameters of pea. The pot experiment revealed that
Alhagi maurorum aqueous extract reduced all growth parameters of pea plant. Also, photosynthesis pigments,
insoluble sugars, total carbohydrate, total protein and total phenolics were markedly reduced in response to
treatment with aqueous Alhagi extract. On other hand, soluble sugars, soluble protein, proline and flavonoids
increased upon treatment with Alhagi maurorum extract.
... Among these secondary metabolites, essential oil stands out, which can perform different biological functions depending on the different constituents produced. For these reasons, the effect of essential oils has been studied in the search for new alternatives that are more sustainable and less toxic to the environment and humans, geared towards management and diversification of agricultural crops (Li et al., 2011;Gusman et al., 2012). ...
Secondary metabolites are produced by certain plant species and may influence the development of some species through the action of allelopathic effects. Thus, the objective of this study was to evaluate the allelopathic effect of Lippia alba essential oil on the germination, emergence and vigor of seedlings of different batches of lettuce seeds. This experiment was conducted in a completely randomized design with a 3x5 factorial scheme consisting of three batches of seeds of the cultivar Grand Rapids® and five doses of L. alba essential oil (0, 0.25, 0.50, 0.75 and 1.00%) diluted in distilled water and homogenized in Tween® 80. Seed germination and vigor, in the laboratory (experiment I), and emergence, in a protected environment (experiment II), were evaluated. The results demonstrated that there was an inhibitory effect with a significant reduction of germination, vigor and seed emergence when L. alba essential oil was added starting at concentrations of 0.25%. The essential oil showed allelopathic potential over different lettuce seed lots, affecting germination, vigor and seed emergence.
... Allelopathy plays an important role in the agro ecosystems may be involved not only in plantÀplant and plant-microorganism's interactions, but also in plantÀinsects or plantÀherbivores communication (Weir et al., 2004). The impact of allelochemical compounds on germination, growth and development of plants is regulated by complexity, interaction and concentration of secondary metabolites (Li et al., 2011;Saleh, 2013). These metabolites are called allelochemicals and are belonging to several chemical classes such as flavonoids, phenolics, alkaloids, terpenoids and cyanogenic glycosides (Mishra, 2015). ...
The present work was conducted to evaluate the effect of aqueous extract of Alhagi maurorum at different rates (1, 5, 10, 15%, w/v) on the growth as well as some physiological parameters of pea (Pisum sativum L.). The pot experiment revealed that Alhagi maurorum aqueous extract reduced all growth parameters of pea plant along with photosynthesis pigments, insoluble sugars, total carbohydrate, total protein and total phenolics. On the other hand, soluble sugars, soluble protein, proline, flavonoids and antioxidant enzymes increased upon treatment with aqueous solution of Alhagi maurorum. The adverse effect of the extract on the growth of treated pea plants especially hydroquinone and sinapyl alcohol that were found in relatively high concentration in the extract were identified and quantified by the GC–MS of the methanolic extract of Alhagi maurorum.
... Some allelochemicals have a crucial role in the inhibition of plant growth and germination (Younesabadi, 2005;Benyas et al., 2011). Complexity, interaction and concentration of allelochemicals are considered cornerstone in understanding how allelochemicals could affect germination, growth, and development of other plants (Inderjit et al., 2002;Mallik and Williams, 2005;Li et al., 2011;Saleh, 2013). It has been Allelopathy, Alhagi graecorum, germination, growth, allelochemicals. ...
... Li et al. (2009) reported that the degree of allelopathic interference and susceptibility can even vary within each species. Such a selective phytotoxicity may reflect a genetic backdrop against the resistance of species to phytotoxicity and their capacities to detoxify the allelochemicals which cause the phytotoxicity (Li et al., 2011). Species-dependent responses to allelochemicals can also play significant roles in preserving ecosystems in their natural states and in designing selective herbicides (Imatomi et al., 2013). ...
In the present study, variations were examined in the content and compositions of Vitex-pseudo-negundo leaf essential oil (EO). These evaluations were carried out at 2 different ontogenetic stages, i.e. before and during flowering. Fresh leaves of vitex were harvested and analyzed at these two stages. The EOs of air-dried samples were extracted by hydrodistillation. The yield of EOs (w/W%) significantly increased (P ≤ 0.05) in the leaves at the flowering stage (0.43%), compared to the stage before it (0.25%). The EOs were analyzed by gas chromatography (GC) and by GC–mass spectrometry (GC–MS). The main EO components in the leaves at these 2 stages were α-pinene (25.4–30.2%), limonene (11.9–12.5%), α-terpinyl acetate (22.6–29.5%) and (E)-caryophyllene (7.6–11.6%). Moreover, α-terpinyl acetate had its strongest presence at the flowering stage (29.5%), while α-pinene, limonene and (E)-caryophyllene showed their highest contents before the flowering stage (30.2, 12.5 and 11.6%, respectively). The phytotoxic activities of EOs were examined at the full flowering stage. These EOs were employed in concentrations of 0, 400, 800, 1200, 1600, 2000 and 2400 μL/L and were used on a crop, Lepidium sativum, and on two weeds, Amaranthus retroflexus and Taraxacum officinale. The EOs of vitex showed inhibitory effects on these species. The efficiency of inhibition depended on the type of species being treated with EO and on the concentration of EO being used.
... The number of their producing seeds are large, and their seed emergence period is uneven, making the prevention of their occurrence difficult. Thus, they have greatly influence the growth and yield of wheat (Reiss et al., 2018;Li et al., 2011;Cui et al., 2011). The grass resistance among different wheat varieties has certain differences. ...
... Although the both genera are distributed around the world, S. irio is originated from southern Europe, Africa and temperate and tropical regions of Asia (National Plant Germplasm System, 2012), whereas D. sophia is from Northern Africa and South of Europe (Zhang, 2003). These annual dicotyledonous plants grow immensely in fodder plains, pasturelands, farms, waysides and disarranged terrains (Mitich 1996;Li et al. 2011). Descurainia genus is designated in memory of F Decourain, a French botanist who lived from 1678 through the mid-18 th century. ...
Descurainia sophia and Sisymbrium irio, both from Brassicaceae family have potential
medicinal effects. Seeds are consumed widely across Iran in sweet drinks. To determine the morphological and molecular diversity, 55 genotypes from these two genera were studied. All 11 ISSR primers detected polymorphism and generated 274 polymorphic loci. The average values of Polymorphism Information Content (PIC), Marker Index (MI) and Resolving Power (Rp) for ISSR primers were 0.278, 6.899 and 11.57, respectively. The AMOVA analysis revealed a high genetic variation (58%) within each genus. The UPGMA clustering based on molecular analysis separated all 55 genotypes into two main groups, correlating with division of plants into two genera. Moreover, seven morphological traits were evaluated to distinguish all 55 genotypes. Among them, rosette figure showed the most significant differentiation between two genera. The highest correlation was observed between two traits of seed color and seed weight at 0.758. The dendrogram obtained from the morphological traits corresponded with the UPGMA clustering. The chemical composition of essential oils of D. sophia and S. irio were identified via gas chromatography mass spectrum (GC-MS). Although GC-MS analysis detected β-pinene as the dominant component in both plants but different compounds were also detected. The present investigation clearly indicates that these morphological traits alone or combined with molecular analysis using 11 ISSR markers is considered as the true reflection of two genera partitioning, and hence the eligibility of both molecular and morphological criterion are proved. These findings could be used for future
breeding programs in fields of seed production and medicinal extracts.
... These bioactive substances (secondary metabolites) are complex molecules with various functional structures (Lahlou 2013) and can be produced in all plant tissues such as leaves, flowers, fruits, roots, rhizomes, stalks, and seeds. The presence of such substances may vary in quantity and quality and from species to species, once their occurrence and synthesis are influenced by genetic and environmental factors (Li et al. 2011;Senica et al. 2017). ...
The purpose of this review is to assist readers in understanding the importance of Lupinus albescens to nature, farmers, and scientists. L. albescens is mostly found in Argentina, Uruguay, Paraguay, and in “Campanha, Litoral and Missões” regions of State of Rio Grande do Sul (Brazil). Therefore, this review presents information and discussion on this plant that can encourage novel studies in a near future for exploring evermore the biological and physicochemical properties of L. albescens. The plant presents adaptive characteristics of soils with low content of nutrients, being an important plant for the recovering of degraded areas. In the last few years, there was an increase in scientific interest for exploring its chemical composition and biological activities. All plant matrices (i.e., roots, leaves, seeds, and stalks) are rich in antioxidant and antifungal compounds, especially stigmasterol. For example, the extracts obtained from the roots are reported with more than 50 wt% stigmasterol and 25 wt% ergosterol. Furthermore, the extracts present remarkable fungicide effects, especially against Fusarium oxysporum and Fusarium verticillioides.
... Allelopathy occurs by the release of chemicals to the environment that can be positive or negative to the target (Inderjit, 2003). Some of the deleterious effects caused by essential oils in plants are the retardation or inhibition of germination and development of seedlings and organs (Dudai et al., 1999;Singh et al., 2003;Li et al., 2011). Kaur et al., (2010) found that the essential oil from Artemisia scoparia had herbicidal effect on Achyranthes aspera, Cassia occidentalis, Parthenium hysterophorus, Echinochloa crus-galli and Ageratum conyzoides. ...
The large production of poultry is in part due to antimicrobials that are used to improve broiler chicken performance, although in recent years this practice has been questioned due to suspected appearance of residues in the meat and resistant microorganisms. Thus, the essential oils emerge as promising substitutes to the usual growth promoters. The aim of this study was to analyze the state of the art concerning the use of essential oils as additives in broiler diets and such data will be used to conduct further studies in the future. The databases used were SciELO, Portal Capes, Science Direct and PubMed. 42 papers published between 2005 and 2014 were selected. 27 plant species were tested, and oregano was the most used. The essential oils act in different ways in the organism of the animals, going beyond the antimicrobial activity and showing effect on several productive parameters of the poultry, with results similar or better than those of antimicrobials.
... Descurainia sophia extract exhibited antibacterial activity against Gram-positive Streptococcus pyogenes ( Aghaabbasi et al., 2014). Recently, Li et al. (2011) investigated allelopathic influence of D. sophia (one of the most troublesome weeds in wheat fields in China) volatile oils on wheat cultivars. Descurainia sophia has been widely used in folk medicine. ...
Volatile constituents obtained by autolysis of aerial and underground parts of D. sophia and the essential oil obtained by hydrodistillation of whole plant samples were analyzed in detail by GC and GC-MS. In total, 71 constituents were identified, accounting for more than 90% of the total peak areas in the chromatograms. Both aerial and underground autolysates contained considerable amounts of lignan arctigenin and cuticular wax compounds. The essential oil was dominated by glucosinolate breakdown product 4-pentenenitrile. Glucosinolate degradation products identified in the essential oil and autolysates, 3-butenyl isothiocyanate, 4-pentenenitrile and allyl isothiocyanate, suggested the presence of gluconapin and sinigrin in this species as the most likely “mustard oil” precursors.
... The allelopathic activity of aromatic plants have received attention in numerous publications [59][60][61][62]. The complexity of allelopathic actions in natural ecosystems is due to a multitude of events participating in a dynamic process of allelochemicals release [63]. ...
In the present paper, the essential oil and the volatiles emitted in vivo by leaves of A. herba alba, which grows wild in center of Tunisia, were analyzed by GC-MS and SPME, respectively. The essential oil was characterized by the predominance of oxygenated monoterpenes (93.3) with α-thujone as the major compound (45.5) followed by β-thujone (11.4), trans-sabinyl acetate (10.1) and 1,8-cineole (7.4). The SPME analyses showed that oxygenated monoterpenes were the most representative compounds (64.9). The major ones were α-thujone (37.9), germacrene D (16.5), 1,8-cineole (8.4) followed by β-thujone (7.8). Moreover, different activities (antioxidant, antibacterial, allelopathic and insecticidal) of the leaf essential oil were investigated. The antioxidant activity was ascertained by evaluating its inhibitory effect against DPPH and ABTS. The results showed that the essential oil had a strong activity and it was more effective against the DPPH radical (IC50=6μg/mL) than the ABTS radical (IC50=40μg/mL). In antibacterial screening, it inhibited the growth of all bacteria tested except Salmonella anatum and Salmonella salamae which were resistant to this oil type. Staphylococcus aureus and Vibrio cholera were found to be extremely sensitive with the lowest MIC value (0.007mg/mL). In addition, allelopathic activity was evaluated against Lactuca sativa and Raphanus sativus. Data showed that, with essential oil, seed germination was completely inhibited for both of them, suggesting a potent allelopathic potential for the evaluated oil. Insecticidal activity was investigated against Culex pipiens larvae and a weak activity (LC50 241.1ppm) for this A. herba alba essential oil.
... As natural inhibitors of plant germination and growth, essential oils are involved in allelopathic interactions and therefore play an important role in the structure and standardization of plant communities (15). Numerous studies have demonstrated this potential (15,16,18). ...
Elionurus muticus is a native grass from Brazil that has been shown to have large variability in the chemical constituents of its essential oil. However, few studies have evaluated this species. The aims of this study were to chemically characterize four wild populations of E. muticus that were collected in southern Brazil as well as to evaluate the allelopathic effect of the essential oil, which is rich in citral. Chemical analyses were performed using gas chromatography and mass spectrometry. The phytotoxic activity was evaluated with onion and lettuce seeds. The results showed that the studied populations have chemical variability based on their geographic origin, which indicates the possibility of chemotypes. The results obtained with E. muticus essential oil, reveals phytotoxic activity on the germination and growth of lettuce and onion.
... This inhibition may be due to the presence of terpenes in these essential oils. Many studies proved the effect of terpenes from plant volatile oils on wheat species (Li et al., 2011;Zahed et al., 2010;De Feo et al., 2002;Dudai et al., 2004;Djurdjevic et al., 2004). ...
Phytotoxic properties of plants and their compounds against other plants or seeds are being increasingly reported. Moreover, essential oils may provide a new source of phytotoxic agents with possibly novel mechanisms of action. The aim of this study is to determine the chemical composition of the leaves, stems and leaves + stems essential oils by GC/MS and to assess their phytotoxic activities extracted from Haplophyllum tuberculatum A. Juss. (Forssk) as well as of the aromatic water obtained from these parts and of the roots. The phytotoxic activities of the essential oils and hydrosols were evaluated against Triticum aestivum L. and Raphanus sativus L. seeds. The GC–MS analysis revealed the presence of limonene, cis-p-menth-2-en-1-ol, trans-p-menth-2-en-1-ol, cis-piperitol, trans-piperitol, 1-octyl acetate, piperitone and isobornyl acetate as major compounds. Phytotoxic results showed that the assayed stems essential oils were active on the roots inhibition (IC50 = 1.09 mg/mL) for wheat. Leaves + stems essential oils had a significant activity against the tested seeds with IC50 ranged from 0.70 to 1.46 mg/mL for radical and epicotyls/coleoptiles percentage inhibition against T. aestivum L. and R. sativus L. While the hydrosols of leaves, stems and leaves + stems inhibited seeds germination at a higher concentration. The essential oils of this plants cannot be used as biologic herbicide with these cultivated plants.
... It is expected that the world herbal drug market will reach a total of 5 trillion US dollars by 2050 (Joshi et al. 2004). Descurainia sophia L. Webb ex Prantl belongs to Brassicaceae family and is a self-compatible, dicotyledonous plant that grows extensively in forage, rangelands, cultivated crops, disturbed areas, roadsides and waste sites (Mitich 1996;Baskin et al. 2004;Blackshaw et al. 2005;Hernandez Plaza et al. 2011;Li et al. 2011). D. sophia originated in South Europe and North Africa (Zhang 2003). ...
Descurainia sophia is a valuable medicinal plant in family of Brassicaceae. To determine the range of diversity amongst D. sophia in Iran, 32 naturally distributed plants belonging to six natural populations of the Iranian plateau were investigated by inter-simple sequence repeat (ISSR) markers. The average percentage of polymorphism produced by 12 ISSR primers was 86 %. The PIC values for primers ranged from 0.22 to 0.40 and Rp values ranged between 6.5 and 19.9. The relative genetic diversity of the populations was not high (Gst =0.32). However, the value of gene flow revealed by the ISSR marker was high (Nm = 1.03). UPGMA clustering method based on Jaccard similarity coefficient grouped the genotypes into two major clusters. Graph results from Neighbor-Net Network generated after a 1000 bootstrap test using Jaccard coefficient, and STRUCTURE analysis confirmed the UPGMA clustering. The first three PCAs represented 57.31 % of the total variation. The high levels of genetic diversity were observed within populations, which is useful in breeding and conservation programs. ISSR is found to be an eligible marker to study genetic diversity of D. sophia. © 2015 Prof. H.S. Srivastava Foundation for Science and Society
... Li et al. (2009) reported that the degree of allelopathic interference can even vary within species. Such selective toxicity may reflect the differential inherent resistance of receiver plants and their capacities for phytotoxin detoxification (Li et al., 2011). Species-dependent responses to allelochemicals can also play significant roles in composition of natural ecosystems and design selective herbicides (Imatomi et al., 2013). ...
Medicinal and aromatic plants have many useful applications in different aspects. In the present study, the allelopathic potential of essential oil (EO) and water extract (WE) of peppermint (Mentha × piperita L. CV. Mitcham) on seed germination and seedling growth of two horticultural crops, tomato (Lycopersicon esculentum Mill.) and radish (Raphanus sativus L.) and three weeds, field bindweed (Convolvulus arvensis L.), purslane (Portulaca oleracea L.) and jungle rice (Echinochloa colonum L.) were investigated. Different concentrations (0, 300, 600, 900, 1200, 1500 and 1800 μlL−1) of EO and 0, 2, 4, 6, 8, and 10% (v/v) of the plant water extract (WE) were examined. The active ingredients of the EO and the WE were determined by GC–MS and HPLC instruments. The main EO components were menthol (35%), mentone (17.48%), menthofuran (11.7%) and 1,8- cineole (5.9%) and some determined phenolic compounds in the extract were trans-ferulic acid (10.8 mg/g), hesperidin (9.3 mg/g), ellagic acid (6.8 mg/g), and sinapic acid (4.2 mg/g). The measured features for evaluation of allelopathic potency of EO and WE were seed germination percentage, root and shoot lengths, and dry weight of the seedlings. Results showed that different concentrations of EO and WE had significant effects (p ≤ 0.05) on seed germination and seedling growth of most tested plants. By increasing the concentration of EO and WE, all studied traits of the plants were decreased compared with control. However, the crop plants (tomato and radish) were more susceptible to phytotoxic effects of the EO and WE treatments than the weeds. In conclusion, EO and WE of peppermint had remarkable inhibitory effects on the studied plants and might be considered as active ingredients for formulation of natural herbicides in future weed control programs.
... A alelopatia é um mecanismo em que as plantas vivas ou mortas liberam alguns tipos de compostos que podem exercer efeito negativo ou positivo sobre outras plantas, desempenhando papel fundamental nos ecossistemas naturais e administrados. Para descobrir as possibilidades dos efeitos alelopáticos na agricultura, o isolamento de novos compostos é a alternativa mais viável e promissora (LI et al., 2011). ...
In recent years, essential oils have gained commercial interest in the agricultural area, mainly for their allelopathic, insecticidal, antifungal, antimicrobial and antioxidant properties, and, also for their natural compounds, which have generally displayed low toxicity, relatively low cost and rapid degradation in the environment. Medicinal plants have emerged as potential suppliers of essential oils because of their ethnopharmacological utility. The aim of this study was to evaluate the allelopathic potential of essential oils extracted from fresh leaves of lemon grass (Cymbopogon citratus), wild basil (Ocimum gratissimum L.) and sweet basil (Ocimum basilicum L.) with regard to their major constituents (citral, eugenol and cineol, respectively) in different application forms (direct contact and the effect of volatile constituents) on the germination and vigor of lettuce seeds (cultivar Regina SF 3500). The effects of the oils and their major components were evaluated with regard to the variables: first germination count, total germination, GVI (germination velocity index), seedling dry weight and average lengths of shoots and lettuce roots. The essential oils from lemon grass and basil displayed allelopathic potentials on seed germination and vigor of lettuce achenes that can be assigned to their respective major constituents citral and eugenol. On the other hand, the allelopathic effect of the essential oil from basil was a consequence of the combined effect of all the components, regardless the application method.
... Living or dead plants with allelopathic properties release toxic substances, collectively known as allelochemicals, through root exudation, volatilisation, leaching and decomposition of plant materials (Rice, 1984). Volatilization from the aboveground parts of the plant is one of the major releasing modes (Li et al., 2011). The incorporation of plant parts that release allelopathic substances as a part of a weed management program can be exploited for sustainable cropping systems (Chon and Kim, 2004). ...
Tinospora tuberculata Beumee is an aromatic shrub with pharmacological properties and belongs to the Menispermaceae family. We assessed T. tuberculata for its ability to suppress growth of weeds in rice fields. In seedling bioassays, the rate of seed germination and the radicle and hypocotyl lengths of barnyardgrass, rice and weedy rice seedlings were reduced as the concentration of aqueous water extracts and volatile organic compounds increased compared to the control. In a glasshouse experiment, T. tuberculata leaf powder also exhibited effective reduction in the emergence and growth of weeds in rice fields. Applications at rates of 4 t ha− 1 completely suppressed emergence of barnyardgrass, sprangletop and smallflower umbrella. The chemical compositions of extracts and volatiles were analyzed by GC–MS and HS-SPME-GC–MS. The results showed that 7 of 43 components in the leaf aqueous extract, as compared to 5 of 15 compounds in the stem aqueous extract, are known to be toxic compounds. Moreover, eight main volatile organic compounds were identified, which accounted for 97 and 95% of the whole fresh and dry leaf volatiles, respectively. We observed qualitative and quantitative differences in the compounds present in the dry and fresh leaf. Confocal laser scanning microscope images showed that the volatile emissions and aqueous extracts also inhibited the main root diameter, and the number and elongation of root hairs of tested weeds in rice fields. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors. Hence, it can be used as a mulch to suppress weeds in rice fields and for developing new herbicide based on phytotoxic compounds release by this plant.
... Descurainia sophia (L.) Webb ex Prantl (flixweed) is an annual weed (Brassicaceae family), widely distributed in cultivated crops, forage and rangelands throughout the world (Mitich, 1996;Baskin et al., 2004;Blackshaw et al., 2005;Hernandez Plaza et al., 2011;Li et al., 2011). This weed, in particular its seed, is used for food, medicinal and industrial purposes (Mitich, 1996;Peng et al., 1997;Bekker et al., 2005;Sun et al., 2005;Mohamed and Mahrous, 2009;Li et al., 2010;Mosaddegh et al., 2012). ...
Descurainia sophia (flixweed) is an annual weed widely distributed in cultivated crops, forage and rangelands throughout the world. This weed, in particular its seed, is used for food, medicinal and industrial purposes. The objective of this study was to investigate the effects of irrigation management and different application rates of nitrogen on morphological traits and yield components of this weed as a means of enhancing production and economic returns. A two-year field experiment was conducted in a semi-arid region in Iran during the 2009–2010 and 2010–2011 growing seasons. The experiment was a split plot in a randomized complete block design with three replicates, with irrigation treatments as main plots and nitrogen rates as sub plots. The three irrigation regimes consisted of 0.1 maximum allowable depletion or deficiency (MAD) of available soil water (ASW), 0.2 MAD of ASW, 0.4 MAD of ASW in 2010 and 0.2 MAD of ASW, 0.4 MAD of ASW and 0.8 MAD of ASW in 2011. The plants were grown at three nitrogen rates of 0, 200, and 300 kg N ha−1. Generally there were significant increases in seed yield, biomass, straw yield, harvest index, number of siliques (pods) per plant, seed weight, plant height, time to maturity, water use efficiency, protein concentration in seed, straw N concentration, nitrogen uptakes and nitrogen harvest index each growing season by applying nitrogen at all irrigation treatments. There was a decreasing trend in number of plants per m2, nitrogen utilization efficiency and oil concentration with increasing nitrogen application under all the irrigation treatments. Seed yield response to irrigation treatments and N rates seemed to be more related to number of plants per m2 and number of siliques per plant. The highest seed yield was obtained at the plant population of 686 plants per m2. The results obtained here suggest that nitrogen application can improve the seed yield and seed quality of D. sophia grown under different irrigation regimes. Averaged over both years, the application of 300 kg N ha−1 under 0.2 MAD of ASW resulted in the highest revenue; 200 kg N ha−1 was not significantly different to 300 kg N ha−1.
... These metabolites are called allelochemicals and are belonging to several chemical classes such as flavonoids, phenolics, alkaloids, terpenoids and cyanogenic glycosides (Einhellig, 1999;Chou, 2006). The impact of allelochemicals on germination, growth and development of plants is governed by their complexity, interaction and concentration (lnderjit et al., 2002;Mallik and Williams, 2005;Li et al., 2011;Saleh, 2013). They cause alteration in plant metabolism owing to their interactions with vital growth processes and activities of many enzymes. ...
The current study evaluated the allelopathic potential of Alhagi graecorum on germination and seedling growth of two common crop plants; bean (Vicia faba) and corn (Zea mays). Water soluble allelochemicals were extracted from the air dried-powdered shoots of A. graecorum at three different concentrations (2.0, 4.0 and 6.0%, w/v). The germination experiment revealed that seeds of both bean and corn have tolerance to the aqueous extract of A. graecorum, where concentrations up to 6.0% had no significant effect on percent of germination as compared with the untreated seeds. The results showed that the lowest concentration (2.0%) of the aqueous extract stimulated elongation of radicle and plumule as well as seedling biomass of both bean and corn, while the highest concentration (6.0%) was inhibitory. In addition, the growth of corn seedlings was retarded at the modest dose (4%) of the aqueous extract, while that for bean seedlings was promoted at the same concentration. Similarly, water soluble allelochemicals extracted from A. gaecorum shoots influenced accumulation of soluble sugars and proteins in a concentration and species dependent manner.
... The presence of weeds with other crops decreases grain yields owing to competition for light, moisture and minerals [19]. Allelopathic functioning from weeds is another important factor to cause detrimental effect on the growth of the crops by releasing allelochemicals into the ambient environment [20,21]. From the above mentioned introduction, winter wheat confronts not only O 3 stress under global climate change scenarios, but also the threat caused by weeds such as flixweed. ...
To investigate the effects of ozone on winter wheat and flixweed under competition, two species were exposed to ambient, elevated and high [O3] for 30 days, planted singly or in mixculture. Eco-physiological responses were examined at different [O3] and fumigating time. Ozone reduced the contents of chlorophyll, increased the accumulation of H2O2 and malondialdehyde in both wheat and flixweed. The effects of competition on chlorophyll content of wheat emerged at elevated and high [O3], while that of flixweed emerged only at high [O3]. The increase of H2O2 and malondialdehyde of flixweed was less than that of wheat under the same condition. Antioxidant enzyme activities of wheat and flixweed were seriously depressed by perennial and serious treatment using O3. However, short-term and moderate fumigation increased the activities of SOD and POD of wheat, and CAT of flixweed. The expression levels of antioxidant enzymes related genes provided explanation for these results. Furthermore, the increase of CAT expression of flixweed was much higher than that of SOD and POD expression of wheat. Ozone and competition resulted in significant reductions in biomass and grain yield in both winter wheat and flixweed. However, the negative effects on flixweed were less than wheat. Our results demonstrated that winter wheat is more sensitive to O3 and competition than flixweed, providing valuable data for further investigation on responses of winter wheat to ozone pollution, in particular combined with species competition.
The fabrication of carbon materials with low cost and high performance is the main challenge in wide applications of supercapacitors. In this work, facile carbonization and chemical activation processes are developed to convert flixweed seeds to hierarchical porous carbon with large specific surface area and self-doped ample heteroatoms (e.g., nitrogen, sulfur and oxygen). The obtained carbon material demonstrates several advantages in supercapacitors, such as ultrahigh specific capacitance of 662.4 F g⁻¹ at 0.5 A g⁻¹ and long cycling life >12,000 cycles at 20 A g⁻¹. A symmetric supercapacitor based on the resulting carbon delivers a high energy density of 34 W h kg⁻¹ at 1000 W kg⁻¹ in 1 M Na2SO4. Therefore, flixweed seeds can be economically utilized for large-scale production of porous carbon with excellent supercapacitance performance.
Herbicides are agrochemicals applied in the control of weeds. With the frequent and repetitive use of these substances, serious problems have been reported. Compounds of natural origin and their derivatives are attractive options to obtain new compounds with herbicidal properties. By aiming to develop compounds with potentiated herbicidal activity, phenoxyacetic acids were synthesized from eugenol and guaiacol. The synthesized compounds were characterized and the herbicidal potential of phenoxyacetic acids and precursors was evaluated through bioassays regarding the germination and initial development of Lactuca sativa and Sorghum bicolor seedlings, with the induction of DNA damage. The induction of changes in the mitotic cycle of meristematic cells of roots of L. sativa was also analyzed. At the concentration of 3 mmol L-1, phenols and their respective phenoxyacetic acids presented phytotoxic and cytotoxic activities in L. sativa and S. bicolor. Eugenol and guaiacol also presented genotoxic action in L. sativa. The toxic effect of eugenoxyacetic acid was more pronounced in L. sativa than in S. bicolor, similar to the commercial 2,4-D herbicide. Molecular properties of the phenols and their derivatives phenoxyacetic acids were compared with the ones obtained for the herbicide 2,4-D, where it was found a correlation between their molecular properties and bioactivity.
Eragrostis plana (Nees) (Tough Lovegrass) shows ability to interfere with other plants, a phenomenon known as allelopathy. This chemical interaction between plants occurs due to the release of compounds into the environment. Thus, a phytotoxicity study was carried out with E. plana roots collected during each season throughout the year, and the compounds were extracted with solvents of increasing polarity. The data from the bioassays were analyzed by GLM and PCA. In addition, a fingerprint of these extracts was obtained by HPLC-DAD. The extracts in petroleum ether from roots collected in the winter and summer showed greater phytotoxicity on Ipomoea grandifolia germination and growth. The PCA obtained from the chromatogram of the crude extract showed that the extracts in petroleum ether were chemically different from the extracts in ethyl acetate and methanol. Thus, continuing this study in order to develop a new generation of bio-herbicides is essential.
The present study aims to test the Acritopappus confertus (Gardner) R. M. King & H. Rob. essential oil allelopathic potential on the germination and inital development of Cenchrus echinatus L. and Lactuca sativa L. seedlings, in addition to identifying and quantifying chemical constituents. The chemical composition analysis was performed by gas chromatography (GC-FID) and gas chromatography coupled to mass-spectrometry (GC-MS). For the allelopathic assays, the essential oil was emulsified with dimethylsulfoxide (DMSO) in a 1:1 ratio, and diluted in distilled water to obtain 0.001, 0.01, 0.10, 0.25, 0.50, 0.75 and 1% c. The control consisted of 1% aqueous DMSO solution.Treatments were performed in five repetition with 20 seeds each. The pH of the oils were measured and adjusted to a scale of 6 to 7. Assays were conducted in a germination chamber at 25 °C with a 12h photoperiod. Seed germination, Germination Speed Index (GSI), caulicle and radicle length were analyzed. The data were subjected to analysis of variance and the means were compared by Tukey test (p<0.05), through the ASSISTAT. The constituents mycene, β-pinene and limonene stood out the most in chemical analysis. The essential oil did not influence C. echinatus and L. sativa seed germination, however it influenced GSI and seedling development. The effects observed herein may be due to chemical constituents found in the studied species, which may act in an isolated or combined manner.
The intensive application of agrochemicals in crops has negatively impacted the environment and other organisms. The use of naturally occurring compounds may be an alternative to mitigate these effects. Plants are secondary metabolite reservoirs and may present allelopathic activity, which is potentially interesting to be used in bioherbicide formulations. In this context, the present work aimed to evaluate the phytotoxic and cytotoxic effects of essential oils extracted from leaves of Sparattanthelium botocudorum and Sparattanthelium tupiniquinorum in bioassays with the plant models Lactuca sativa L. and Sorghum bicolor L. Moench. The essential oils were applied at concentrations of 3,000, 1,500, 750, 375 and 187.5 ppm. Chemical characterization of the oils was performed, and their impact on the percentage of germinated seeds, initial development of L. sativa and S. bicolor seedlings, and changes in the mitotic cycle of meristematic cells from L. sativa roots was evaluated. The major compound of the essential oils was germacrene D, followed by bicyclogermacrene, β-elemene and germacrene A. The phytotoxicity assay showed that the essential oils of both species reduced the root and shoot growth in L. sativa and decreased the germination and shoot growth in S. bicolor. Inhibition was dependent on the tested oil concentration. In the cytotoxicity assay, a decrease in mitotic index and chromosomal and nuclear alterations were observed, which resulted from aneugenic and clastogenic action.
Algumas plantas podem produzir compostos secundários com potencial benéfico no manejo agrícola, como alternativa à utilização no tratamento de sementes, porém, podem apresentar algum tipo de alelopatia inibitória ao desenvolvimento de determinadas culturas de interesse. Logo, o objetivo deste trabalho foi avaliar efeitos alelopáticos do extrato aquoso de manjericão (Ocimum basilicum L.) e babosa (Aloe vera L.) em concentrações na germinação e desenvolvimento inicial de sementes de rúcula (Eruca sativa L.). A concentração para o extrato aquoso foi de 20% (peso/volume) e a partir desta, foram obtidas as demais concentrações. Os tratamentos utilizados foram as concentrações de 25, 50, 75 e 100% dos extratos de babosa e manjericão extraídos pelo método a frio de turbólise, e testemunha com água autoclavada.Os efeitos dos extratos foram avaliados quanto as variáveis: índice de velocidade de germinação, porcentagem de germinação, comprimento de radícula e parte aérea. O experimento foi conduzido em delineamento inteiramente casualizado, com 6 repetições, sendo a unidade experimental composta por uma caixa gerbox com 50 sementes de rúcula. As doses de manjericão e babosa foram testadas em experimentos distintos. Os extratos de manjericão e de babosa apresentam substâncias que favorecem o desenvolvimento da parte aérea, influenciaram negativamente no desenvolvimento da radícula, porém, não apresentaram efeito alelopático na germinação final e velocidade de germinação de sementes de rúcula.
The extracts of Pleioblastus kongosanensis f. aureostriaus were assayed for their effects on seed germination and early seedling growth of V. radiata. All extracts at all concentrations inhibited the seed germination and seedling growth of V. radiata than control, and the degree of inhibition increased with the incremental extracts concentration. Bioassay-guided fractionation of ethyl acetate extract of P. kongosanensis led to the isolation of a phenolic compound named xanthoxyline. The results of this study suggested that P. kongosanensis contain allelochemicals, such as xanthoxyline, which could inhibit the seed germination and seedling growth of V. radiate
A rapid and sensitive LC-MS/MS method with good accuracy and precision was developed and validated for the pharmacokinetic study of quercetin-3-O-β-D-glucopyranosyl-7-O-β-D-gentiobioside (QGG) in Sprague-Dawley rats. Plasma samples were simply precipitated by methanol and then analyzed by LC-MS/MS. A Venusil® ASB C18 column (2.1 × 50 mm, i.d. 5 µm) was used for separation, with methanol-water (50:50, v/v) as the mobile phase at a flow rate of 300 μL/min. The optimized mass transition ion-pairs (m/z) for quantitation were 787.3/301.3 for QGG, and 725.3/293.3 for internal standard. The linear range was 7.32-1830 ng/mL with an average correlation coefficient of 0.9992, and the limit of quantification was 7.32 ng/mL. The intra- and inter-day precision and accuracy were less than ±15%. At low, medium and high QC concentrations, the recovery and matrix effect of the analyte and IS were in the range of 89.06-92.43%, and 88.58-97.62%, respectively. The method was applied for the pharmacokinetic study of QGG in Sprague-Dawley rats. This article is protected by copyright. All rights reserved.
The essential oil of Plectranthus amboinicus and its chemotypes, carvacrol and thymol, were evaluated on the germination, root and aerial growth of Lactuca sativa and Sorghum bicolor, and in acting on cell cycle of meristematic root cells of L. sativa. The main component found in the oil by analysis in gas chromatography-mass spectrometry (GC-MS) and gas chromatography flame ionization detector (GC-FID) was carvacrol (88.61% in area). At a concentration of 0.120% (w v-1), the oil and its chemotypes retarded or inhibited the germination and decreased root and aerial growth in monocot and dicot species used in the bioassays. In addition, all substances caused changes in the cell cycle of the meristematic cells of L. sativa, with chromosomal alterations occurring from the 0.015% (w v-1) concentration. Essential oil from leaves of P. amboinicus, carvacrol and thymol have potential for use as bioherbicides.
Casein polypeptides containing substructures of αs(1)-casein, β-casein, k-casein, αs(2)-casein were used as a lignin-blocker at above critical micelles concentration to improve the bioethanol production of dilute acid, lime, alkali, extrusion and AFEX pretreated corn stover (CS). Application of 0.5g/g glucan of casein was found to effectively increase the glucose yield of CS pretreated with dilute acid, lime, alkali, extrusion and AFEX by 31.9%, 17.0%, 22.7%, 29.5%, and 17.4%, respectively with no positive impact on Avicel. Consequently 96h simultaneous saccharification and fermentation (SSF) of these hydrolysates reduced the fermentation period by up to 48h and increased the theoretical yield of ethanol by 8.48-33.7% compared to control. Application of casein during saccharification reduced the enzyme utilization by 33.0%. Recycling of hydrolysate from casein-treated CS for a 2nd round hydrolysis resulted in average glucose yield of 36.4% compared to 29.0% control.
Osmotic priming of seed was evaluated as a means of improving stand establishment, early seedling growth, and yield of processing tomatoes ( Lycopersicon esculentum Mill. cvs. UC204 and 6203). Seeds were primed in aerated solutions of 3% KNO 3 (w/v) or of polyethylene glycol 8000 (PEG) of equivalent osmotic potential (-1.25 MPa; 314 g-kg ⁻¹ of water) at 20°C for 7 days, rinsed, and dried in forced air at 30°. Under laboratory conditions, seeds primed in either osmoticum germinated more rapidly than untreated seeds at 20° and 30°. At 10°, the PEG treatment was of little benefit for either variety, while the KN0 3 treatment still reduced the time to 50% germination to 60% to 80% of the control value. Priming did not affect the final germination percentage. Seedling emergence in the field was evaluated in March and April planting dates. In both trials, seedlings from primed seeds emerged earlier and more uniformly than seedlings from untreated seeds. Seedlings from primed seeds maintained greater mean plant dry weights, leaf areas, and ground cover percentages than untreated seedlings throughout the preflowering period. This advantage was due entirely to early emergence rather than to an increased relative growth rate. The early growth advantage from seed priming did not improve earliness of maturity, total yield, or soluble solids content of fruit.
Allelopathy has been suggested as a mechanism promoting the monoculture formation of some invasive exotic plants. Previous
studies have shown that hydrophobic extracts of the roots and soil of exotic bitou bush (Chrysanthemoides monilifera spp. rotundata (DC.) T. Norl.) inhibited the seedling growth of five Australian native plants, including the dominant acacia (Acacia longifolia var. sophorae (Labill.) F. Muell.). Based on this finding, we compared the hydrophobic root and soil chemical profiles of bitou bush and
acacia to determine whether bitou bush roots release allelopathic compounds that are novel to the invaded system. We detected
three compounds that were exclusive to the bitou bush root and soil, and seven compounds that were common to the bitou bush
and acacia roots but only present in the bitou bush soil. The compounds unique to the bitou bush invaded soil were all sesqui-
and diterpenes. Several of these compounds were found to inhibit the seedling growth of a native sedge, Isolepis nodosa (Rott.) R. Br. Of particular interest are the sesquiterpenes: β-maaliene, α-isocomene, β-isocomene, δ-cadinene, 5-hydroxycalamenene and 5-methoxycalamenene which were found in high concentrations in the bitou bush root and soil
extracts and exhibited phytotoxic activity. Therefore, we present evidence to suggest that bitou bush exudes low molecular
weight volatile compounds into the soil which inhibit native plant seedling growth. The reduced establishment of native plants
via allelopathy is likely to create space and contribute to the invasion of bitou bush on the eastern Australian coast.
In laboratory studies, water-soluble extracts of the litter of four shrub and three conifer species had variable effects on the growth of four species of ectomycorrhizal fungi. In general, low concentrations (parts per thousand) stimulated fungal growth; while, high concentrations (parts per hundred and parts per ten) either stimulated growth, inhibited growth, or had no effect, depending on both fungal and litter species. In greenhouse studies, litter applied to the surface of a sand-soil mixture reduced the formation ofRhizopogon sp. on Douglas-fir seedlings. Allelochemicals in the litter may inhibit seedling growth and suppress fungai growth and root colonization in the field, thus explaining the failures of reforestation by conifer species in disturbed sites.
Allelopathy and resource competition have often been suggested to explain plant-plant interference. Many studies have attempted
to separate these two mechanisms of interference to demonstrate either as a probable cause of an observed growth pattern.
We, however, are of the opinion that separating allelopathy from resource competition is essentially impossible in natural
systems. Furthermore, any experimental design to separate allelopathy and resource competition will create conditions that
will never occur in nature. In this article, the ecological interaction between allelopathy and resource competition in natural
systems is discussed.
Exhaustive hydro-distillation of Descurainia sophia (L.) Webb ex Prantl (flixweed) collected from two different locations (Cangzhou city-Sample 1 and Beijing city-Sample 2) gave in both cases yellowish colored oils in 0.31 and 0.26% yield, respectively. Detailed chemical composition of the essential oils was analyzed by GC and GC/MS, and forty and thirty-eight compounds were identified. The results indicated that the most abundant component of Sample 1were cis-beta-ocimene (20.1%), menthol (11.27%), neoisomenthyl acetate (3.5%), alloaromadendrene (2.28%) and longicyclene (2.25%). Compared with the constituents of Sample 1, several chemical compounds such as 1,8-cineole, alpha-eudesmol, cis, trans-farnesol and beta-pinene were not detected in Sample 2 although it was similarly dominated by cis-beta-ocimene (17.12%), menthol (10.7%) and neoisomenthyl acetate (2.96%). Final analysis of the chemical constituents in the essential oils of the two samples showed similarity in their chemical composition, but the relative content of all shared chemical constituents in Sample 2 was lower than that in Sample 1.
We compared the potential allelopathic activity of 47 monoterpenoids of different chemical groups, by estimating their effect on seed germination and subsequent growth of Lactuca sativa seedlings. Apart from individual compounds, eleven pairs at different proportions were also tested. As a group, the hydrocarbons, except for (+)-3-carene, were the least inhibitory. Of the oxygenated compounds, the least inhibitory were the acetates; whenever the free hydroxyl group of an alcohol turned into a carboxyl group, the activity of the resulting ester was markedly lower (against both germination and seedling growth). Twenty-four compounds were extremely active against seedling growth (inhibiting it by more than 85%), but only five against seed germination. The compounds that were most active against both processes belonged to the groups of ketones and alcohols; they were terpinen-4-ol, dihydrocarvone, and two carvone stereoisomers. We used a model to investigate whether compounds acted independently when applied in pairs. The combined effect varied. In half of the cases, it followed the pattern expected under the assumption of independence; in the rest, either synergistic or antagonistic interactions were found in both germination and elongation. However, even in cases of synergistic interactions, the level of inhibition was not comparable to that of a single extremely active compound, unless such a compound already participated in the combination. The specific structural factors that operate and determine the activity of monoterpenoids still remain rather obscure. The same holds true for the combined effect; its character cannot in general be predicted on the basis of individual compounds acting alone.
Several volatile allelochemicals were identified and characterized from fresh leaf tissue of three distinct populations of the invasive perennial weed, mugwort (Artemisia vulgaris). A unique bioassay was used to demonstrate the release of volatile allelochemicals from leaf tissues. Leaf volatiles were trapped and analyzed via gas chromatography coupled with mass spectrometry. Some of the components identified were terpenes, including camphor, eucalyptol, alpha-pinene, and beta-pinene. Those commercially available were tested individually to determine their phytotoxicity. Concentrations of detectable volatiles differed in both absolute and relative proportions among the mugwort populations. The three mugwort populations consisted of a taller, highly branched population (ITH-1); a shorter, lesser-branched population (ITH-2) (both grown from rhizome fragments from managed landscapes); and a population grown from seed with lobed leaves (VT). Considerable interspecific variation existed in leaf morphology and leaf surface chemistry. Bioassays revealed that none of the individual monoterpenes could account for the observed phytotoxicity imparted by total leaf volatiles, suggesting a synergistic effect or activity of a component not tested. Despite inability to detect a single dominant phytotoxic compound, decreases in total terpene concentration with increase in leaf age correlated with decreases in phytotoxicity. The presence of bioactive terpenoids in leaf surface chemistry of younger mugwort tissue suggests a potential role for terpenoids in mugwort establishment and proliferation in introduced habitats.
Laboratory, greenhouse, and field studies were conducted to determine the allelopathic potential of lantana and Siam weed on the germination and growth of five crops. Emergence and dry weight of bioassay species were affected when lantana or Siam weed debris was present on the soil surface or incorporated into the soil. However, presence of Siam weed on the soil surface did not affect dry weight of rape. Emergence and dry weight of crops (except emergence of spinach) were not affected when crops were grown in soil samples collected from beneath field-grown lantana. Dry weight of Chinese cabbage and chilli was reduced when these crops were grown in Siam weed-contaminated soil. Germination of Chinese cabbage, chilli, and rape decreased progressively when exposed to increasing concentrations of aqueous lantana extract. However, the lantana extract at full strength (66.7 g L ⁻¹ ) did not reduce germination of spinach and cucumber seed. Siam weed extract, when applied at full strength to seed of spinach, Chinese cabbage, rape, and chilli, reduced germination by 10, 12, 21, and 19% of control, respectively. Full-strength extract of lantana and Siam weed decreased seedling length and fresh weight of all crops.
The extensive spread of Phragmites australis throughout brackish marshes on the East Coast of the United States is a major factor governing management and restoration decisions because it is assumed that biogeochemical functions are altered by the invasion. Microbial activity is important in providing wetland biogeochemical functions such as carbon and nitrogen cycling, but there is little known about sediment microbial communities in Phragmites marshes. Microbial populations associated with invasive Phragmites vegetation and with native salt marsh cordgrass, Spartina alterniflora, may differ in the relative abundance of microbial taxa (community structure) and in the ability of this biota to decompose organic substrates (community biogeochemical function). This study compares sediment microbial communities associated with Phragmites and Spartina vegetation in an undisturbed brackish marsh near Tuckerton, New Jersey (MUL), and in a brackish marsh in the anthropogenically affected Hackensack Meadowlands (SMC). We use phospholipid fatty acid (PLFA) analysis and enzymatic activity to profile sediment microbial communities associated with both plants in each site. Sediment analyses include bulk density, total organic matter, and root biomass. PLFA profiles indicate that the microbial communities differ between sites with the undisturbed site exhibiting greater fatty acid richness (62 PLFA recovered from MUL versus 38 from SMC). Activity of the 5 enzymes analyzed (β-glucosidase, acid phosphatase, chitobiase, and 2 oxidases) was higher in the undisturbed site. Differences between vegetation species as measured by Principal Components Analysis were significantly greater at the undisturbed MUL site than at SMC, and patterns of enzyme activity and PLFAs did not correspond to patterns of root biomass. We suggest that in natural wetland sediments, macrophyte rhizosphere effects influence the community composition of sediment microbial populations. Physical and chemical site disturbances may impose limits on these rhizosphere effects, decreasing sediment microbial diversity and potentially, microbial biogeochemical functions.
Prior generalizations about the ecological roles of monoterpenes may be misleading if based on the presumed insolubility of monoterpenes in water. We determined the aqueous solubility of 31 biologically active monoterpenes by gas chromatography. While hydrocarbons were of low solubility (< 35 ppm), oxygenated monoterpenes exhibited solubilities one or two orders of magnitude higher, with ranges of 155-6990 ppm for ketones and of 183-1360 ppm for alcohols. Many monoterpenes are phytotoxic in concentrations under 100 ppm, well below the saturated aqueous concentrations of oxygenated monoterpenes. Therefore, even dilute, unsaturated solutions of monoterpenes, occurring naturally in plant tissues and soil solutions, may act as potent biological inhibitors.
The hypothesis was tested that allelopathic agents released from fire-sensitive plants of the Florida scrub community deter the invasion of fireprone sandhill grasses. The structures of the constituents of four endemic scrub species,Conradina canescens, Calamintha ashei, Chrysoma pauciflosculosa, andCeratiola ericiodes, were established and their phytotoxic activity against two grasses of the sandhill was examined. Effects of the secondary metabolites from the above scrub species and their degradation products upon the germination and radicle growth of little bluestem (Schizachyrium scoparium) and green sprangletop (Leptochloa dubia), two native grasses of the Florida sandhill community, were determined. The studies included determination of the water solubility and release mechanism of terpenes and other allelopathic agents from the source plants and their aqueous transport to the target species. Some of the natural products were nontoxic until activated by light and/or oxidation after release from the source plant into the environment.
Characteristics of higher plant terpenoids that result in mediation of numerous kinds of ecological interactions are discussed as a framework for this Symposium on Chemical Ecology of Terpenoids. However, the role of terpenoid mixtures, either constitutive or induced, their intraspecific qualitative and quantitative compositional variation, and their dosage-dependent effects are emphasized in subsequent discussions. It is suggested that little previous attention to these characteristics may have contributed to terpenoids having been misrepresented in some chemical defense theories. Selected phytocentric examples of terpenoid interactions are presented: (1) defense against generalist and specialist insect and mammalian herbivores, (2) defense against insect-vectored fungi and potentially pathogenic endophytic fungi, (3) attraction of entomophages and pollinators, (4) allelopathic effects that inhibit seed germination and soil bacteria, and (5) interaction with reactive troposphere gases. The results are integrated by discussing how these terpenoids may be contributing factors in determining some properties of terrestrial plant communities and ecosystems. A terrestrial phytocentric approach is necessitated due to the magnitude and scope of terpenoid interactions. This presentation has a more broadly based ecological perspective than the several excellent recent reviews of the ecological chemistry of terpenoids.
Reports arose From major Chinese wheat production regions that flixweed was not controlled by tribenuron after the herbicide was continuously used For several Years. Flixweed seeds were collected from wheat Fields that had been treated with tribenuron repeatedly over 3 to 15 yr or From road sides and remote hills that had never received tribenuron ill Jiangsu, Hebei, Shanxi, Sichuan, Shandong, Shaanxi, and Henan provinces, and Tianjin and Beijing metropolises in China. The response of various biotypes to tribenuron was determined by whole plant experiments in File greenhouse. The experiments demonstrated that 11 of 32 flixweed biotypes were susceptible to tribenuron. The remaining 21 biotypes expressed moderate to high levels of tribenuron resistance with resistance indices ranging from 4 to > 1,500. DNA sequence analysis of acetolactate synthase (ALS) genes of selected biotypes 6, 7, 27, and 29 revealed a point mutation at position 197 of the ALS gene, as numbered relative to the protein sequence Of Arabidopsis, where proline was substituted by leucine in biotype 7 and by, threonine in biotype 29. These mutations are known to confer resistance to ALS-inhibiting herbicides and are responsible for the high resistance of these biotypes to tribenuron. The results also indicate that tribenuron resistance in flixweed is widespread in China and management programs to control these resistant populations are warranted.
Allelopathy can be defined as an important mechanism of plant interference mediated by the addition of plant-produced secondary products to the soil rhizosphere. Allelochemicals are present in all types of plants and tissues and are released into the soil rhizosphere by a variety of mechanisms, including decomposition of residues, volatilization, and root exudation. Allelochemical structures and modes of action are diverse and may offer potential for the development of future herbicides. We have focused our review on a variety of weed and crop species that establish some form of potent allelopathic interference, either with other crops or weeds, in agricultural settings, in the managed landscape, or in naturalized settings. Recent research suggests that allelopathic properties can render one species more invasive to native species and thus potentially detrimental to both agricultural and naturalized settings. In contrast, allelopathic crops offer strong potential for the development of cultivars that are more highly weed suppressive in managed settings. Both environmental and genotypic effects impact allelochemical production and release over time. A new challenge that exists for future plant scientists is to generate additional information on allelochemical mechanisms of release, selectivity and persistence, mode of action, and genetic regulation. In this manner, we can further protect plant biodiversity and enhance weed management strategies in a variety of ecosystems. Referee: Dr. Steve Weller, Purdue University, Dept. of Horticulture, West Lafayette, IN 47907
The germination and seedling growth of 12 plant
species and 12 cultivars from 2 plant species were tested in the presence of
aqueous extracts of vulpia dry matter residues. Concepts of whole-range
assessment and inhibition index were developed, and used, with principal
component analysis, for assessing results. Species were grouped according to
the inhibition index. Average threshold concentration, average
I50 (the extract concentration required to cause
50% inhibition in plant response) and average root and coleoptile
lengths were used as auxillary indices for each group. Marked differences in
tolerance toward the phytotoxicity of vulpia residue extracts were observed
among species and cultivars. Such differences were widespread among plant
species, with generally cocksfoot, Vulpia spp.,
subterranean clover (cv. Trikkala), phalaris, canola, medics, and oats being
relatively tolerant, while lupins, barley, and wheat (cvv. Janz, Vulcan) were
the most susceptible, and subterranean clover (cvv. Seaton Park, Karridale,
Clare, Woogenellup, Junee), field peas, and wheat (cvv. Ford, Darter,
Dollarbird, Rosella) were relatively susceptible. The findings of this study
suggest that choice of species and cultivar may be a valuable management
option for minimising the negative effects of vulpia residues. The whole-range
assessment developed in this study proved to be a statistically efficient
summary of the plant response profiles. Together with the bioassay techniques
adopted, it provides a simple and rapid screening methodology for assessing
the relative tolerance of plant species to the allelopathic effects of weed
residues.
The present study investigated the allelopathic effects of various black mustard (Brassica nigra L.) plant parts on alfalfa germination and seedling growth. Aqueous extracts of black mustard (Brassica nigra L.) leaf, stem, flower and root plant parts were made to determine their effects on germination and dry weights of hypocotyl, and radicle length of 5-day-old alfalfa seedlings over a range of extract concentrations. All aqueous extracts significantly inhibited alfalfa seed germination and seedling growth when compared with the distilled water control. Increasing the aqueous extract concentrations of separated Brassica nigra plant parts significantly inhibited alfalfa germination, seedling length and weight. Based on significant radicle length reactions to aqueous extracts, the toxicity may be classified in the following order of decreasing inhi-bition: flower, leaf, mixture of all plant parts, root, and stem. Increasing the concentration of aqueous flower extracts significantly inhibited the water uptake by germinated alfalfa seeds. The greatest inhibition in water uptake occurred at a 12 g kg -1 extract concentration for seeds soaked for 8 h.
From the root bark of Eupomatia laurina were isolated four anti-microbial alkaloids; sampangine (I), eupomatine-1 (II), liriodenine and lanuginosine. The isolated alkaloids, the fraction from which I + II were isolated (EI), the dichloromethane fraction of the root bark (RD) and the ethyl acetate fraction of the stem bark (SE) were screened against 13 Gram + and 12 Gram - bacteria, a protozoan and nine fungi. All extracts were found to be active against all the bacteria and protozoan. Antifungal activity was demonstrated by EI, RD and SE fractions only. Compound II and fraction EI were found to be far superior to the standard used, both in broadness and level of activity. MIC was performed on EI and was found to be in most cases 0.5µg while in some case it was 0.1µg. Broad-spectrum antifungal activity was exhibited by fraction EI (10µg disc), RD (4 mg disc) and SE (4 mg disc). MIC was done on EI and was 10µg. The activity of EI, RD and SE was found to be far superior to the standard ketoconozole (20 mg disc) and griseofulvin (25 mg disc).
The effects of tropical weeds on the yield of while yam were studied outdoors in wooden boxes. When the foliage and roots of weeds were in physical contact with the crop until harvest (full interference), tuber yield of yam was reduced by 76–79% of that obtained under weed‐free conditions over 3 years of study. When there was no physical contact between roots of crop and weeds, the leachate from the weed zone caused tuber yield reductions of 42, 40 and 38% in 1978, 1979 and 1980, respectively, when it was applied to the yam zone. This leachate also reduced leaf area index (LAI) in the yam crop but the adverse effects on yam root and shoot biomass were less pronounced. This technique made it possible to separate competitive interference from allelopathic interference of tropical weeds with the yam crop.
Plant roots normally release a complex mixture of chemicals which have important effects in the rhizosphere. Among these different root-emitted compounds, volatile isoprenoids have received very little attention, yet they may play important and diverse roles in the rhizosphere, contributing to the regulation of microbial activity and nutrient availability. It is therefore important to estimate their abundance in the rhizosphere, but so far, there is no reliable sampling method that can be used to measure realistic rates of root emissions from plants growing in field conditions, or even in pots. Here, we measured root content of volatile isoprenoids (specifically monoterpenes) for Pinus pinea, and explored the feasibility of using a dynamic bag enclosure method to measure emissions from roots of intact pot-grown plants with different degrees of root cleaning. We also investigated a passive diffusion method for exploring monoterpenes in soil at incremental distances from mature Pinus sylvestris trees growing in field conditions. Total monoterpene content of P. pinea roots was 415750m gg � 1 fresh wt in an initial screening study, and between 6887103 and 11447208m gg � 1 dry wt in subsequent investigations. Emissions from shaken-clean roots of intact plants and roots of intact plants washed to remove remaining soil after shaken-clean experiments were 119714 and 2675m gg � 1 dry wt h� 1, respectively. Emissions from intact roots in soil-balls were an order of magnitude lower than from shaken-clean roots, and probably reflected the amount of emitted compounds taken up by physical, chemical or biological processes in the soil matrix surrounding the roots. Although monoterpene content was not significantly different in droughted roots, emission rates from droughted roots were generally significantly lower than from well-watered roots. Finally, passive sampling of monoterpenes in the soil at different distances from mature P. sylvestris trees in field conditions showed significantly decreasing sampling rates with increasing distance from the trunk. We conclude that it is feasible to measure volatile isoprenoid emissions from roots but the method of root preparation affects magnitude of measured emissions and therefore must be decided according to the application. We also conclude that the rhizosphere of Pinus species is a strong and previously un-characterized source of volatile isoprenoid emissions and these are likely to impact significantly on rhizosphere function. r 2006 Elsevier Ltd. All rights reserved.
More than 200 species of weeds are infesting main crop fields in China, among which approximately 30 species are major weeds causing great crop yield losses. About 35.8 million hectares of crop fields are heavily infested by weeds and the annual reduction of crop yields is 12.3–16.5% (weighted average). Along with rural economic development, approximately 50% of the main crop fields undergo herbicide application. Chemical weed control has changed cultural practices to save weeding labor in rice, wheat, maize, soybeans and cotton. At the same time, continuous use of the same herbicides has caused weed shift problems and weed resistance to herbicides. Consequently, integrated weed management in main crops is being developed.
The antimicrobial activity of the protoberberine, alkaloid, berberine, isolated fromMahonia aquifolium, was evaluated against 17 microorganisms including two Gram-negative bacteria—Pseudomonas aeruginosa andEscherichia coli (both resistant and sensitive), two Gram-positive bacteria—Bacillus subtilis andStaphylococcus aureus, Zoogloea ramigera, six filamentous fungi—Penicilium chrysogenum, Aspergillus niger, Aureobasidium pullulans (black and white strain),Trichoderma viride (original green strain and brown mutant),Fusarium nivale, Mycrosporum gypseum, and two yeasts—Candida, albicans andSaccharomyces cerevisiae. The IC50, minimum inhibitory concentration (MIC), minimum microbicidal concentration (MMC) and minimum microbistatic concentration
(MMS) varied considerably depending on the microorganism tested, the sensitivity decreasing as follows:S. aureus >P. aeruginosa S (sensitive) >E. coli S>P. aeruginosa R (resistant) >E. coli R>B. subtilis>Z. ramigera>C. albicans>S. cerevisiae>A. pullulans B (black)>A. pullulans W (white)>T. viride Br (brown)>M. gypseum>A niger>F. nivale>P. chrysogenum>T. viride G (green).
The extensive spread ofPhragmites australis throughout brackish marshes on the East Coast of the United States is a major factor governing management and restoration
decisions because it is assumed that biogeochemical functions are altered by the invasion. Microbial activity is important
in providing wetland biogeochemical functions such as carbon and nitrogen cycling, but there is little known about sediment
microbial communities inPhragmites marshes. Microbial populations associated with invasivePhragmites vegetation and with native salt marsh cordgrass,Spartina alterniflora, may differ in the relative abundance of microbial taxa (community structure) and in the ability of this biota to decompose
organic substrates (community biogeochemical function). This study compares sediment microbial communities associated withPhragmites andSpartina vegetation in an undisturbed brackish marsh near Tuckerton, New Jersey (MUL), and in a brackish marsh in the anthropogenically
affected Hackensack meadowlands (SMC). We use phospholipid fatty acid (PLFA) analysis and enzymataic activity to profile sediment
microbial communities associated with both plants in each site. Sediment analyses include bulk density, total organic matter,
and root biomass. PLFA profiles indicate that the microbial communities differ between sites with the undisturbed site exhibiting
greater fatty acid richness (62 PLFA recovered from MUL versus 38 from SMC). Activity of the 5 enzymes analyzed (β-glucosidase,
acid phosphatase, chitobiase, and 2 oxidases) was higher in the undisturbed site. Differences between vegetation species as
measured by Principal Components Analysis were significantly greater at the undisturbed MUL site than at SMC, and patterns
of enzyme activity and PLFAs did not correspond to patterns of root biomass. We suggest that in natural wetland sediments,
macrophyte rhizosphere effects influence the community composition of sediment microbial populations. Physical and chemical
site disturbances may impose limits on these rhizosphere effects, decreasing sediment microbial diversity and potentially,
microbial biogeochemical functions.
The essential oil composition of Lantana camara, Eucalyptus camaldulensis and Eriocephalus africanus was analyzed by means of GC and GC–MS and bioassayed in order to determine their activity against Amaranthus hybridus and Portulaca oleracea. E. camaldulensis essential oil, with spathulenol as the main compound, was the most effective, completely inhibiting germination and seedling growth on both weeds. The essential oil of E. africanus, rich in artemisia ketone, showed activity similar to that of E. camaldulensis on A. hybridus, but it was not so effective against P. oleracea, and L. camara essential oil, with high percentages in sesquiterpene hydrocarbons, also showed higher phytotoxic activity against A. hybridus, inhibiting its germination and seedling length; however, it showed no effect against P. oleracea germination, whereas was effective in significantly reducing its seedling growth at all concentrations assayed. The results suggest the possible use of these essential oils as natural herbicides.
2,4-Dichlorophenoxyacetic acid butyl ester (2,4-D butyl ester) is extensively applied for weed control in cultivation fields in China, but its effect on soil microbial community remains obscure. This study investigated the microbial response to 2,4-D butyl ester application at different concentrations (CK, 10, 100 and 1000 μg g−1) in the soils with two fertility levels, using soil dilution plate method and phospholipid fatty acid (PLFA) analysis. Culturable microorganisms were affected by the herbicide in both soils, particularly at the higher concentration. After treating soil with 100 μg g−1 herbicide, culturable bacteria and actinomycetes were significantly higher, compared to other treatments. Treatment of soil with 1000 μg g−1 2,4-D butyl ester caused a decline in culturable microbial counts, with the exception of fungal numbers, which increased over the incubation time. PLFA profiles showed that fatty acids for Gram-negative (GN) bacteria, Gram-positive (GP) bacteria, total bacteria and total fungi, as well as total PLFAs, varied with herbicide concentration for both soil samples. As herbicide concentration increased, the GN/GP ratio decreased dramatically in the two soils. The higher stress level was in the treatments with high concentrations of herbicide (1000 μg g−1) for both soils. Principal component analysis of PLFAs showed that the addition of 2,4-D butyl ester significantly shifted the microbial community structure in the two soils. These results showed that the herbicide 2,4-D butyl ester might have substantial effects on microbial population and microbial community structure in agricultural soils. In particular, the effects of 2,4-D butyl ester were greater in soil with low organic matter and fertility level than in soil with high organic matter and fertility level.
Invasions of exotic plant species are among the most pervasive and important threats to natural ecosystems, however, the effects of plant invasions on soil processes and the soil biota have rarely been investigated. We grew two exotic and a native under-story plant species in the same mineral soil from a non-invaded forest stand in order to test whether observed differences in the field could be experimentally produced in the greenhouse. We characterized changes in the soil microbial community structure (as indexed by PLFAs) and function (as indexed by enzyme activities and SIR), as well as changes in potential nitrogen mineralization rates. We found that the invasion of two very dissimilar exotic species into the under-story of deciduous forests in eastern North America can rapidly cause changes in most of the studied soil properties. At the end of the three-month incubation, soils under the exotic species had significantly different PLFA, enzyme and SIR profiles than both initial soils and soils where native shrubs had been grown. We also observed a significant increase in pH and nitrification rates under one of the exotic plants. Such changes in the soil are potentially long-term (e.g. changes in soil pH) and are therefore likely to promote the re-invasion of these and other exotics. Both management of exotic plant invasions and the restoration of native communities must take into account exotic species effects on the soil.
Allelopathic rice releases allelochemicals from its roots to paddy soils at early growth stages to inhibit neighboring weeds. However, little is currently known about the effects of allelochemicals on soil microbes. In this study, we show that allelopathic rice can have great impact on the population and community structure of soil microbes. Allelopathic rice PI312777 seedlings reduced the culturable microbial population and total PLFA when compared to non-allelopathic rice Liaojing-9. Similar results were observed when, instead of growing seedlings, soils were incubated with plant root exudates. This result demonstrates that the composition of root exudates from the rice varieties tested contributes to the soil microbial community. Further experiments showed that the microbial community was affected by the allelochemical 5,4′-dihydroxy-3′,5′-dimethoxy-7-O-β-glucopyranosylflavone exuded from allelopathic rice roots, through immediately hydrolyzing glucose with stimulation on soil bacteria and aglycone (5,7,4′-trihydroxy-3′,5′-dimethoxyflavone) with inhibition on soil fungi. This result indicates that the flavone O-glycoside can provide carbon and interact with soil microbes. PC analysis of the fatty acid data clearly separated the allelopathic PI312777 and the non-allelopathic Liaojing-9 variety (PC1 = 46.4%, PC2 = 20.3%). Similarly, the first principal component (PC1 = 37.4%) together with the second principal component (PC2 = 17.3%) explained 54.7% of the variation between the allelopathic and non-allelopathic root exudates. Furthermore, the canonical correlation between allelopathic root exudates and the flavone O-glycoside was statistically significant (Canonical R = 0.889, χ2 (25) = 69.72, p = 0.0041). Although the data generated in this study were not completely consistent between culturable microbes and PLFA profile, it is a fact that variation in soil microbial populations and community structures could be distinguished by the allelopathic and non-allelopathic rice varieties tested. Our results suggest that individual components of rice root exudates, such as allelochemicals from allelopathic rice, can modify the soil microbial community.
While allelopathy has been defined as plant-plant chemical interference, there has been much confusion about what the concept encompasses and how important it is in nature. We distinguish between (1) direct plant-plant interference mediated by allelochemicals, and (2) the effects of secondary compounds released by plants on abiotic and biotic soil processes that affect other plants.It very difficult to demonstrate direct effects of chemicals released by a plant on nearby plants. Although soil ecology-mediated effects of secondary plant compounds do not fit the classical concept of allelopathy, we find support in the literature for the hypothesis that the most important effects of compounds released into the soil environment by plants on other plants occur through such indirect effects. The emphasis on, and skepticism of, direct plant-plant allelopathic interference has led some researchers to demand unreasonably high standards of evidence for establishing even the existence of allelopathic interactions, standards that are not demanded for other plant-plant interactions such as resource competition. While the complete elucidation of the mechanisms by which allelochemicals function in the field is many years away, such elucidation is not necessary to establish the existence of allelopathic interactions.We propose that most of the phenomena broadly referred to as allelopathic interference are better conceptualized and investigated in terms of soil chemical ecology. Even when direct plant-plant allelochemical interference occur, the levels of allelochemicals in the environment and their effects on plants are heavily influenced by abiotic and biotic components of the soil ecosystem. Putting allelopathy in the context of soil ecology can further research and reduce some of the less fruitful controversy surrounding the phenomenon.
Plants may favorably or adversely affect other plants through allelochemicals, which may be released directly or indirectly from live or dead plants (including microorganisms). Due to increase in the number of herbicide-resistant weeds and environmental concerns in the use of synthetic herbicides, there have been considerable efforts in designing alternative weed management strategies. The conventional synthetic herbicides are becoming less and less effective against the resistant weed biotypes. The objective of this article is to examine the role of allelopathic cover crops/crop residues, natural compounds, and allelopathic crop cultivars in natural weed management. Numerous examples of employing crop residues, cover crops and allelopathic crop cultivars in weed management are provided. Although we cannot eliminate the use of herbicides, their use can be reduced by exploiting allelopathy as an alternate weed management tool for crop production against weeds and other pests.
Invading exotic plants are thought to succeed primarily because they have escaped their natural enemies, not because of novel interactions with their new neighbors. However, we find that Centaurea diffusa, a noxious weed in North America, has much stronger negative effects on grass species from North America than on closely related grass species from communities to which Centaurea is native. Centaurea's advantage against North American species appears to be due to differences in the effects of its root exudates and how these root exudates affect competition for resources. Our results may help to explain why some exotic species so successfully invade natural plant communities.
Allelochemicals play an important role in explaining plant growth inhibition in interspecies interactions and in structuring the plant community. Five aspects of allelochemicals are discussed from an ecophysiological perspective: (i) biosynthesis, (ii) mode of release, (iii) mode of action, (iv) detoxification and prevention of autotoxicity, and (v) joint action of allelochemicals. A discussion on identifying a compound as an allelochemical is also presented.
Twenty compounds identified in vulpia (Vulpia myuros) residues as allelochemicals were individually and collectively tested for biological activity. Each exhibited characteristic allelochemical behavior toward the test plant, i.e., inhibition at high concentrations and stimulation or no effect at low concentrations, but individual activities varied. Allelopathins present in large quantities, such as syringic, vanillic, and succinic acids, possessed low activity, while those present in small quantities, such as catechol and hydrocinnamic acid, possessed strong inhibitory activity. The concept of a phytotoxic strength index was developed for quantifying the biological properties of each individual allelopathin in a concise, comprehensive, and meaningful format. The individual contribution of each allelopathin, assessed by comparing the phytotoxic strength index to the overall toxicity of vulpia residues, was variable according to structure and was influenced by its relative proportion in the residue. The majority of compounds possessed low or medium biological activity and contributed most of the vulpia phytotoxicity, while compounds with high biological activity were in the minority and only present at low concentration. Artificial mixtures of these pure allelochemicals also produced phytotoxicity. There were additive/synergistic effects evident in the properties of these mixtures. One such mixture, formulated from allelochemicals found in the same proportions as occur in vulpia extract, produced stronger activity than another formulated from the same set of compounds but in equal proportions. These results suggest that the exploration of the relative composition of a cluster of allelopathins may be more important than simply focusing on the identification of one or two compounds with strong biological activity and that synergism is fundamental to the understanding of allelopathy.
Two new lactones (1, 2), descurainolide A and B, and one new aryl-8-oxa-bicyclo[3,2,1]-oct-3-en-2-one (3), descurainin, together with five known compounds (4-8), were isolated from the seeds of Descurainia sophia (L.) WEBB ex PRANTL. The structures of the new compounds were elucidated by extensive studies of their 1D, 2D NMR and HR-MS. Compounds 4 and 5 showed cytotoxicity.
Benzoxazinones 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA) and 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA) have been considered key compounds for understanding allelopathic phenomena in Gramineae crop plants such as corn (Zea mays L.), wheat (Triticum aestivum L.), and rye (Secale cereale L.). The degradation processes in the environment observed for these compounds, in which soil microbes are directly involved, could affect potential allelopathic activity of these plants. We present in this work a complete structure-activity relationships study based on the phytotoxic effects observed for DIMBOA, DIBOA, and their main degradation products, in addition to several synthetic analogues of them. Their effects were evaluated on standard target species (STS), which include Triticum aestivum L. (wheat) and Allium cepa L. (onion) as monocots and Lepidium sativum L. (cress), Lactuca sativa L. (lettuce), and Lycopersicon esculentum Will. (tomato) as dicots. This permitted us to elucidate their ecological role and to propose new herbicide models based on their structures. The best phytotoxicity results were shown by the degradation chemical 2-aminophenoxazin-3-one (APO) and several 2-deoxy derivatives of natural benzoxazinones, including 4-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one (ABOA), 4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIBOA), and 4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIMBOA). They showed high inhibitory activity over almost all species growth. The fact that APO is a degradation product from DIBOA with high phytotoxicity and stability makes it possible to assign an important ecological role regarding plant defense mechanisms. 2-Deoxy derivatives of natural benzoxazinones display a wide range of activities that allow proposing them as new leads for natural herbicide models with a 1,4-benzoxazine skeleton.
Compliance with glucose monitoring by patients with diabetes is poor because of the pain and inconvenience of conventional blood collection using lancets. To improve compliance, and thereby reduce morbidity and mortality associated with poor glucose control, this study sought to develop and test minimally invasive microneedles to extract dermal interstitial fluid (ISF) for glucose monitoring.
We used a thermal puller to fabricate individual or multi-needle arrays of glass microneedles with tip radii of 15-40 microm to penetrate 700-1,500 microm deep into the skin of anesthetized hairless rats or conscious, normal, adult, human subjects. After applying a vacuum of 200-500 mm Hg for 2-10 min, we extracted ISF and measured glucose concentration. These measurements were compared with glucose levels in blood collected from the tail vein of rats or finger stick on humans.
Using this procedure, 1-10 microL of ISF was extracted out of holes punctured in the skin using microneedles. Human subjects generally reported the procedure as painless. ISF glucose concentration correlated well with blood levels based on 140 measurements on 15 rats and six measurements on six human subjects, where 95% of rat data and 100% of human data fell within the clinically acceptable A + B region in Clarke Error Grid analysis. A linear calibration factor was needed to correlate ISF and blood glucose concentrations using our standard procedure. Modifying the procedure to prevent ISF evaporation during extraction provided a one-to-one correlation that eliminated the need for calibration. ISF glucose measurements tracked rapidly changing blood glucose levels following insulin injection with a time lag of less than 20 min.
These results suggest that microneedle devices can be used to extract ISF for painless glucose monitoring.
A new aryldihydronaphthoic acid, descuraic acid (1), was isolated from the seeds of Descurainia sophia (L.) Webb ex Prantl. The structure of 1 was elucidated by means of physico-chemical properties and spectroscopic methods (1D and 2D NMR, MS). 1 was a new nor-lignan.
Phenoxy herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used in agricultural practices. Although its half life in soil is 7-14d, the herbicide itself and its first metabolite 2,4-dichlorophenol (2,4-DCP) could remain in the soil for longer periods, as a consequence of its intensive use. Microcosms assays were conducted to study the influence of indigenous microflora and plants (alfalfa) on the dissipation of 2,4-D from soils of the Humid Pampa region, Argentina, with previous history of phenoxy herbicides application. Results showed that 2,4-D was rapidly degraded, and the permanence of 2,4-DCP in soil depended on the presence of plants and soil microorganisms. Regarding soil microbial community, the presence of 2,4-D degrading bacteria was detected even in basal conditions in this soil, possibly due to the adaptation of the microflora to the herbicide. There was an increment of two orders of magnitude in herbicide degraders after 15d from 2,4-D addition, both in planted and unplanted microcosms. Total heterotrophic bacteria numbers were about 1x10(8) CFUg(-1) dry soil and no significant differences were found between different treatments. Overall, the information provided by this work indicates that the soil under study has an important intrinsic degradation capacity, given by a microbial community adapted to the presence of phenoxy herbicides.