Plant Allelopathy Research Articles

Kin discrimination in allelopathy and consequences for agricultural weed control.

Among all biotic stress types (i.e. pathogens, pests and weeds), weeds have the largest potential for yield reduction (larger than the other two combined) (Oerke, 2006). Chemical control of weeds is coming under increasing pressure due to concerns about their health- and environmental impacts and increasing herbicide resistance of weeds. As a consequence there is an increased interest in ecological weed control, of which development of weed-suppressive crops can be an important part (Bastiaans, Paolini, & Baumann, 2008). In the current issue, Xu, Cheng, Kong, and Meiners (2021) for the first time, show that kin recognition (the ability of plants to distinguish genetically related individuals from strangers) can make rice plants more competitive against weeds potentially being a new strategy in ecological weed control. This article is protected by copyright. All rights reserved.

Complementing cultural weed control with plant allelopathy: Implications for improved weed management in wheat crop

Wheat (Triticum aestivum L.) is an important cereal crop in Pakistan which is suffering from major grain production loss because of weed infestations. Control of weeds by herbicides is a primary weed management tool in wheat crop which can be detrimental to the environment and grain produce. Development of an efficient and eco-friendly alternate to the herbicidal weed control, testing the effectiveness of cultural weed control (crop row orientation, selected wheat genotypes and hand weeding) and plants water extracts was undertaken for weed control in wheat. An experiment was run under field conditions in winter season in 2016–2017 and in 2017–2018 in Khyber Pakhtunkhwa Province, Pakistan. The repeated experiment was each time undertaken using a randomized complete block design with a double split plot arrangements at the New Developmental Farm, University of Agriculture, Peshawar, Pakistan. The crop row orientations used were assigned to the main plots. The wheat genotypes used were assigned to the sub-plots. The allelopathic water extracts and hand weeding were assigned to the sub-sub plots. The averaged mean values for row orientations of both the years revealed lowest weed density (95.7 weeds m−2), highest grains per spike (47.3), 1000 grains weight (44.7 g) in north to south row orientation. The averaged mean values of weed density (101.6 weeds m−2), grains per spike (48.2), 1000 grains weight (45.9 g), crude protein content (12.793%), crude fat content (1.533%) and ash content (1.586%) were greater for the wheat genotype Pirsabaq-2013 and Atta-Habib-2010. Water extract of S. halepense, P. hysterophorus, H. annuus and hand weeding showed significantly lower weed density (84.0 to 93.3), grains per spike (50.9 to 48.3), 1000 grains weight (48.3 to 46.2 g), grains protein content (12.280 to 12.209%), grains crude fat content (1.471 to 1.464%) and grains ash content (1.523 to 1.515%). Interaction effect of different tested weed control treatments i.e. N-S × Pirsabaq-2013 and Atta-Habib-2010 × water extract of S. halepense, P. hysterophorus and H. annuus were found to show further reduction in weed density and enhance grains per spike and grains nutrition contributing parameters. Our results show that sowing wheat genotypes Pirsabaq-2013 and Atta-Habib-2010 in north-to-south row orientation, and application of water extract of S. halepense, P. hysterophorus, H. annuus can give an effective weed management and increased quality grain yield of wheat.

ALLELOPATHIC INVESTIGATION OF CHENOPODIUM MURALE (L.) ON ZEA MAYS (L.) AND HORDEUM VULGARE (L.)

The aspects of allelopathy, allelochemicals, mechanism of allelopathy of weed plants and their impact on crops are discussed in this review paper. An overview of the mode of action of the weed and different strategies and their direct and indirect impact on the overall agricultural system were analyzed. After the passing of the 20th century, the curiosity of the researchers took a remarkable work in comparison to the last decades of the 19th century that was needed too mainly because there was little awareness to the farmers of farming. They are using old practices and synthetic agrochemicals still now, thus having a long-lasting negative impact on the overall factors that have the ability to keep ecosystem balance. There are advanced agriculture techniques and tools that are exploring day by day with the reference to sustainable problems. Allelochemicals are present in all types of tissues and are released by a variety of mechanisms, including decomposition of residues, volatilization and root exudation into the rhizosphere. Allelochemical its structure and mode of action are different and may offer a potential for the future development of herbicide. In this context, there is the discussion of the invasiveness of Chenopodium murale (L.) on certain selected crop species and the aggressiveness of different plant species on the same.

Research progress on application of biochar in cultivation of agriculture and Chinese materia medica

Biochar is a kind of solid material with high aromatization and rich in carbon, which is formed by pyrolysis of biomass at high temperature(250-700 ℃) under anoxic or hypoxic conditions. It has the characteristics of large specific surface area and rich pores. In recent years, as a good soil conditioner, biochar has gradually improved its advantages in improving soil rhizosphere micro ecological environment, promoting plant growth and development, and enhancing plant resistance, etc. It has been proved that biochar can affect the growth and development of plants by improving soil physical and chemical properties, adjusting microbial community structure, participating in the metabolic process in plants, and inducing plants to enhance resistance. This paper summarized the research progress of biochar application in agriculture and introduced the ecological effects and mechanism of biochar on plant seed germination, seedling growth, crop yield and stress resistance. Combined with the characteristics of Chinese materia medica, this paper expounds the application potential of biochar in improving the content of secondary metabolites of Chinese materia medica and alleviating continuous cropping obstacles of Chinese materia medica, etc. In the future, it is necessary to strengthen the research of biochar in the biosynthesis of secondary metabolites, allelopathy and heavy metal stress of medicinal plants, so as to provide reference for the application of biochar in the cultivation of Chinese materia medica.

Effects of clonal integration on allelopathy of invasive plantWedelia trilobataunder heterogeneous light conditions

AbstractPlant invasion is one of the most serious threats to ecosystems worldwide. When invasive plants with the ability of clonal growth invading or colonizing in new habitat, their interconnected ramets may suffer from heterogeneous light. Effects of clonal integration on allelopathy of invasive plants are poorly understood under heterogeneous light conditions. To investigate the effects of clonal integration on allelopathy of invasive plant Wedelia trilobata under heterogeneous light conditions, a pot experiment was conducted by using its clonal fragments with two successive ramets. The older ramets were exposed to full light, whereas the younger ones were subjected to 20% full light. The younger ramets of each clonal fragment were adjacently grown with a target plant (one tomato seedling) in a pot. Stolon between two successive ramets was either severed or retained intact. In addition, two tomato seedlings (one as target plant) were adjacently grown in a pot as contrast. Compared with severing stolon, biomass accumulation, foliar chlorophyll and nitrogen contents, chlorophyll fluorescence parameters and net photosynthetic rates of the target plants as well as their root length and activity, were significantly decreased when stolon between interconnected ramets of W. trilobata retained intact. Under heterogeneous light conditions, transportation or sharing of carbohydrate between two successive ramets enhanced allelopathy of the young ramets subjected to 20% full light treatment. It is suggested that clonal integration may be important for invasion or colonization of invasive plants with ability of clonal growth under heterogeneous light conditions.

Plant Allelopathy Research and Development: 60 Years (1960-2019)

environment. It is one of the hotspots in Ecology and Agronomy. In this paper, we have retrieved from the Web of Science (WoS) SCI-E database the allelopathy-related studies (1960-2019). The Annual Number of Publications, Authors, Countries, Institutions, Journals and Keywords were analyzed by the bibliometric method to determine the research trends and hotspot changes in this field over the past 6 decades. From 1960-2019, the WoS database included 4,114 studies in the field of plant allelopathy. During this period of 60 years, the number of publications has gone through three stages: (i). Initial Stage (1960-1990), (ii). Growing Stage (1991-2009) and (iii). Stable Stage (2010-2019). The studies were conducted by 9,956 authors at 2,166 institutions across 100 countries. The United States, China, and Japan have the highest number of publications. The top three institutions with the highest number of publications are the Chinese Academy of Sciences, Kagawa University and USDA, USA. The top three authors are H. Kato-Noguchi, F.A. Macias, and C.H. Kong. The major Journals in this field are: (i). Allelopathy Journal, (ii). Journal of Chemical Ecology and (iii). Plant and Soil. The results of keyword clustering showed that the main research directions in this field are: (i). Metabonomics undergoing allelopathy, (ii). Functions of allelopathy substances, (iii). Molecular biology, (iv). Allelopathy of aquatic plants, (v). Alien plants invasion and (vi). Application of plant allelopathy in agroforestry production. Plant allelopathy is a research field that aims to maintain stable development. Future studies should focus on strengthening the cooperation among international scholars in plant allelopathy research and improving the output in frontier and hotspot areas.

Sunn hemp (Crotalaria juncea) weed suppression and allelopathy at different timings

ABSTRACT The utilisation of plant allelopathy is an important tool in a diversified weed management strategy. Allelochemicals are released by some plants, such as sunn hemp (Crotalaria juncea L.), to inhibit the growth of neighbouring plants. This species was tested for use as an allelopathic plant for weed control in cropping systems. The allelopathic properties of sunn hemp were tested under field conditions at different timings of 4, 8, 12 and 16 weeks after planting (WAP). The results showed that sunn hemp at 8, 12 and 16 WAP significantly decreased the total number of weeds compared with the control weedy check. The similar trend of decreasing weed number was observed in grass and broadleaf weeds, as well as sedge. The allelopathic activity of sunn hemp was further investigated in the soil planted with sunn hemp and water extracts on tested plants. Phytotoxicity of the soil, planted with sunn hemp at different timings, did not significantly decrease germination, shoot length, root length and dry weight of tested plants. However, the water extracts caused significantly decreased germination and plant growth, especially the shoot extracts exhibited the inhibitory effects more than the root extracts. Interestingly, the extracts from sunn hemp at 4 WAP had higher inhibitory effects than the extracts from other stages. These results suggest that sunn hemp growth stage is an important consideration for maximising biological weed control in cropping systems.

Transcriptome and degradome sequencing reveals changes in Populus × euramericana ‘Neva’ caused by its allelopathic response to p-hydroxybenzoic acid

Plant species produce different types of allelopathic chemicals in nature; however, little is known about the differential regulation of plant allelopathy. Because allelopathy caused by p-hydroxybenzoic acid (pHBA) is one of the main obstacles to continuous cropping of Populus × euramericana ‘Neva’, we examined gene expression dynamics in Neva leaves induced by pHBA. The expression of genes related to photosynthesis and respiration changed, while mRNA involved in regulating gene expression during allelopathy was degraded. Some miRNAs that are involved in plant allelopathy target crucial genes for regulating reactive oxygen species. Moreover, coexpression regulatory networks were constructed based on profiles of the identified miRNA-target interactions and the differentially expressed miRNA–target pairs. These findings provide a mechanistic framework for understanding allelopathy in plants.

Pioneers of Allelopathy: XVI. Shaolin Peng

Shaolin Peng contributed immensely to restoration ecology research in last 40- years and has published 700 papers. He has made innovative and theoretical breakthroughs in vegetation restoration, ecological restoration of invaded ecosystems, interaction between ecological restoration and global change, etc. One of his key achievements is vegetation restoration in subtropical South China. He has developed new models of vegetation in natural succession, replacement and fluctuation, advanced theory and proved that extremely degraded tropical forests can be restored. He established that allelopathy is one of the driving forces of forest succession and did related studies on systematic sampling and analysis of several forest communities from south to north in China. He has done outstanding research on invasive plants and examined the Novel Weapon Hypothesis (allelopathic inhibition) of invasive alien plants in South China and determined the various aspects of invasive mechanism of alien plants (molecular mechanism of elevated temperature and CO effects in allelopathy of invasive plants). He put forward the ‘Allelopathic resistance hypothesis (native plants resistance to invasive plants)’ and ‘ecological control theory’. In recognition of his contributions to <i>Allelopathy</i> field, he was awarded the <i>Outstanding Achievement Award</i> by the International Allelopathy Foundation. He also did in-depth studies on ecological impacts of invasive plants, specifically focusing on plant-soil feedback and plant-AMF symbiosis. Besides, Peng has mentored 68 Ph.D. and 38 M.Sc graduates, and was recognized as Prominent Teacher by Sun Yat-sen University. He has been the Vice President, Ecological Society of China, Vice Chairman, Nature Conservation and Eco-Environment Teaching Steering Committee, Ministry of Education, Member, Academic Degree Commission of State Council, Awarded ‘Top Ten Outstanding Youth in China’, Young Scientist Award, Chinese Academy of Sciences and National Outstanding Scientific and Technical Worker of China.

Effects of Ozone (O3) on leaf secretory cell characteristics related to allelopathy of woody plants: Modelling allelopathic Interactions

We studied the effects of ozone (O3) on the allelopathic medicinal trees/shrubs that influenced other species growing under their canopy in National Park Sochi, Russia (Caucasus region). Using model reactions, the action of rain leachates from these allelopathic trees/shrubs on the plants growing under their canopy was determined. Depending on the duration and intensity of exposure, the O3 treatment of test woody plants changed their (i) characteristics of leaves and their water extracts, (ii) colour and (iii) autofluorescence of secretory cells. Water extracts from the allelopathic woody donor plants served as model of rain leachates, and their effects were tested on the seeds and pollens germination of acceptor plants (Lavatera trimestris L. var.Rubin and Hippeastrum (Herb.) hybridum ). The effects of water extracts from the ozone treated plants differed from the untreated plants. The allelochemicals in donor plants stimulated, inhibited or had no effects on the recipient plants compared with control. The test-reactions in tropospheric ozone stress should be used in Modelling System of tree/shrub-herbaceous plants interactions, to find the allelopathic interactions in urban conditions.

Field application of allelopathic bacteria to control invasion of little seed canary grass in wheat.

Development of successful biological weed control can help to resolve various environmental challenges created by the chemical and mechanical weed control. The current study is aimed at investigating the potential of allelopathic bacteria (hereinafter as AB) for biological weed control in wheat rather than the traditional areas of plant allelopathy, phyto-pathology, and insect biocontrol agents. Eleven strains of AB were obtained that were inhibitory to little seed canary grass of which 5 also inhibited wheat in our previous studies. The remaining strains indicated the potential for biological control of this weed in wheat. Five efficient strains were selected for this purpose to conduct pot and field trials. Seeds of little seed canary grass were sown together in potted soils with wheat seeds inoculated with AB strains. A subsequent field trial was conducted at a site selected based on chronic infestations of canary grass. Seeds of the weed and inoculated wheat were co-seeded directly in field soil. For inoculation, these strains were formulated in sterilized peat and applied to seeds. In pot trials, the invasion of little seed canary grass in wheat reduced wheat grain yield up to 59.9%. Four strains suppressed the weed which resulted in recovery wheat grain yield losses from 20.1 to 66.9%. The field trial showed that the invasion of little seed canary grass reduced wheat grain yields up to 53.9%. Four strains suppressed the weed which resulted into recovery of grain wheat grain yield losses 34.3 to 64.3%. These findings were consistent with improvement of other agronomic, physiological, and chemical parameters of the crop where the four strains of AB (L9, T42, 7O0, and O010) were applied.

Allelopathic Potency and an Active Substance from Hairy Vetch

Background: Plant allelopathy refers to the release of chemicals from plants or microorganisms into the environment, may have direct or indirect, beneficial or harmful effects on other plants or microorganisms. When plants grow in an unfavorable environment,more allelochemicals will be secreted and the expression of allelopathic effects will increase, giving plants a certain competitive advantage. Hairy vetch is one of the most promising allelopathic crops and the aqueous extract of hairy vetch has an inhibitory effect on the root length and seedling height of grass crops. The current study aimed to study the allelopathic effect of hairy vetch on alfalfa, and exploring an ecological method to remove the root system of alfalfa.Methods: In this experiment, the allelopathic effects of the seeds, stems and leaves, roots extracts and root exudates (0, 3, 6, 9 and 12 mg·mL-1) on the seed germination and seedling growth of alfalfa were evaluated. And the main allelopathic substances from the stem and leaf extract were isolated and identified using high performance liquid chromatography- mass spectrometry (HPLC-MS).Result: The results showed that all of the extracts can inhibit alfalfa seed germination and seedling growth and stem and leaf extract had the strongest inhibitory effect, especially for inhibiting the root growth. A main allelochemical substance, o-coumaric acid, was screened out and the root length of alfalfa was completely inhibited at 1.6 mg·mL-1 of o-coumaric acid. The findings of these experiments show hairy vetch has strong allelopathic effect on alfalfa and o-coumaric acid is a chemical growth inhibitor.

OsPAL2-1 Mediates Allelopathic Interactions Between Rice and Specific Microorganisms in the Rhizosphere Ecosystem.

The use of plant allelopathy to control weeds in the field has been generally recognized as a win-win strategy because it is an environmentally friendly and resource-saving method. The mechanism of this natural weed-control method relies on allelochemicals, the rhizosphere microbiome, and their bio-interaction, and exploring the link between allelochemicals and specific microbes helps accelerate the application of allelopathic characteristics in farming. In this study, we used allelopathic rice PI312777 (PI), its genetically modified OsPAL2-1 repression (PR) or overexpression (PO) lines, and non-allelopathic rice Lemont (Le) as donor plants to reveal the bio-interaction between rice allelochemicals and rhizosphere specific microorganisms. The results showed a higher content of phenolic acid exudation from the roots of PI than those of Le, which resulted in a significantly increased population of Myxococcus in the rhizosphere soil. Transgenic PO lines exhibited increasing exudation of phenolic acid, which led to the population of Myxococcus xanthus in the rhizosphere soil of PO to be significantly increased, while PR showed the opposite result in comparison with wild type PI. Exogenous application of phenolic acid induced the growth of M. xanthus, and the expressions of chemotaxis-related genes were up-regulated in M. xanthus. In addition, quercetin was identified in the culture medium; according to the bioassay determination, a quercetin concentration of 0.53 mM inhibited the root length by 60.59%. Our study indicates that OsPAL2-1 is among the efficient genes that regulate rice allelopathy by controlling the synthesis of phenolic acid allelochemicals, and phenolic acid (ferulic acid, FA) induces the chemotactic aggregation of M. xanthus, which promoted the proliferation and aggregation of this microbe. The potential allelochemical, quercetin was generated from the FA-induced M. xanthus cultured medium.

Biological management of allelopathic plantPartheniumsp.

AbstractGlobally, weeds have been considered as a major threat and act as a hindrance to crop production, even though the farmers put tremendous efforts to eliminate the weeds to get a better yield. Weeds stayed a steady threat to productivity and manageability of soil and environment, regardless of many years of research and advances in management practices.Parthenium hysterophorusis widely studied all around the world including India as a noxious and an unsafe weed responsible for many health risks in humans and animals. Many experts employed different biological methods using insects, beetle, microorganisms, and certain pathogens, which caused a broad dispersal damage toP. hysterophorus.Biorational weed control is also offered by allelopathy through the production of allelochemicals from the leaf, blossoms, grains, nuts, bud, berry, trunk, and organization of living or decaying plant substance. Allelopathy is the most realistic method to control the weeds as well as different plants. Lately, there has been a proliferation of curiosity to research on plant allelopathy to control weeds in agro-ecosystems. The successful management of this weed can only be achieved by an integrated approach with allelochemicals as a crucial aspect.

Bryophytes can recognize their neighbours through volatile organic compounds

Communication between vascular plants through volatile organic compounds (VOCs) impacts on ecosystem functioning. However, nothing is known about that between non-vascular plants. To investigate plant–plant VOCs interaction in bryophytes we exposed rare peatland moss Hamatocaulis vernicosus to VOCs of its common competitor Sphagnum flexuosum in an air-flow system of connected containers under artificial light, supplemented or unsupplemented by far-red (FR) light. When exposed to VOCs of S. flexuosum, shoots of H. vernicosus elongated and emitted six times higher amounts of a compound chemically related to β-cyclocitral, which is employed in stress signalling and allelopathy in vascular plants. The VOCs emission was affected similarly by FR light addition, possibly simulating competition stress. This is the first evidence of plant–plant VOCs interaction in non-vascular plants, analogous to that in vascular plants. The findings open new possibilities for understanding the language and evolution of communication in land plants.

The extract of aquatic macrophyte Carex cinerascens induced colony formation in bloom-forming cyanobacterium Microcystis aeruginosa.

Colony formation in Microcystis aeruginosa played important roles in blooms formation. To study the effects of plant allelopathy on colony formation in M. aruginosa, unicellular M. aeruginosa was cultivated under laboratory conditions treated with various extract concentration of Carex cinerascens. The growth of M. aeruginosa in the treatments with 0.05 and 0.1mgL-1 extract of C. cinerascens was promoted but the growth in the treatments with 1.5, 3.0, and 6.0mgL-1 C. cinerascens extract was inhibited. Obvious colony formation in M. aeruginosa was observed in all treatments while no colony formation was detected in the control. The cell number per colony at the first day was the largest and decreased along with culture time. The cell number per colony in the control ranged from 3.0 to 4.0 during the experiment. However, the values in the five treatments at the first day were 33, 80, 58, 41, and 30, respectively. A positive exponential relationship between cell number per colony of M. aeruginosa and extracellular polysaccharides (EPS) content was found as well. Compared the fold-increase in cell number per colony and the fold-increase in total biomass of M. aeruginosa at various day, it was found that colony formation induced by extract of C. cinerascens was primarily dependent on promotion of cell adhesion during the first 2days. The cell number per colony decreased afterward was due to the increasing proportion of single cells in the culture because single cells had a great higher growth rate than M. aeruginosa colonies under culture condition. Our results suggested that plant allelopathy be one of the major factor contributing to colony formation in M. aeruginosa.

Зависимость дыхания стволов дуба разных классов роста от условий окружающей среды

Зависимость дыхания стволов дуба разных классов роста от условий окружающей среды

First Broad Screening of Allelopathic Potential of Wild and Cultivated Plants in Turkey.

Turkey has one of the richest plant diversities in the Mediterranean region. In the current literature, no broad screening has been conducted on the potential allelopathy of plants from Turkey. This study aimed to evaluate the allelopathic activity of a large number of plants from Turkey for the first time and to determine the species with significant plant growth inhibitory potentials by bioassay. Dried samples of different plant parts were collected from local herbalists. The sandwich method was used to evaluate the potential allelopathy of 126 medicinal plants belonging to 55 families. The results of lettuce radicle and hypocotyl growth for 10 and 50 mg sample treatment conformed to normal distribution. Significant inhibition on lettuce radicle elongation with 10 mg sample was observed in 40 species, out of which 27 species showed over 50% inhibitory activity. The results suggested that these species could contain potential inhibitory compounds against lettuce radicle or hypocotyl growth. The calyxes of Hibiscus sabdariffa (3.2% of control) and the seeds of Prunus dulcis (5.7% of control) showed the most potent growth inhibitory activity on lettuce radicle elongation. The potential plant growth inhibitory effects of these plants, together with the fruits of Rhus coriaria and seeds of Prunus mahaleb, have been reported in this study for the first time. All these plants are medicinal, and the results hereby presented provide essential information about the allelopathic effects of medicinal plants from Turkey.

Resource competition and allelopathy in two peat mosses: implication for niche differentiation

Separating the effect of resource competition from allelopathy in plants is challenging and it has never been attempted in closely related co-occurring bryophytes. In peatlands, peat mosses (Sphagnum spp.) show niche differentiation along water table level (WTL) gradient. Our aim was to evaluate whether the hummock species, S. magellanicum would be a winner at low WTL due to its allelopathic advantage and the hollow species, S. angustifolium would win by virtue of its superior competitive ability but not of allelopathy at high WTL due to dilution of its allelochemicals. We used a nested, field experimental design, with two WTL treatments—low WTL (hummock habitat) and high WTL (hollow habitat)—and three different inter-specific interactions: 1) monoculture; 2) mixed culture without activated charcoal; and 3) mixed culture with activated charcoal added to the neighbor. We measured growth and biochemical traits of the two species and compared the index of relative neighbor effect on each other. We discovered a trade-off between biomass production (competitive outcome) and phenolic content (allelopathy) in these species. At low WTL, allelopathy of the hummock species is the main mechanism to suppress the hollow species, whereas at high WTL, competition is the main driver to suppress the hummock species. Competitive advantage in Sphagnum is mediated by both resource competition and allelopathy of the co-occurring species through niche differentiation along a WTL gradient. Unlike vascular plants, Sphagnum mosses can serve as excellent model organisms in studying allelopathic interaction since they bypass the complexity of plant-soil interactions.

Context‐dependent induction of allelopathy in plants under competition

Some plants use allelopathy to compete against neighbouring plants, and the ability to induce allelopathic compound production in response to competition is hypothesized to be adaptive, as plants can save costs of metabolite production in the absence of competitors. However, whether plants induce allelopathy has rarely been explored so far.We studied the inducibility of polyacetylenes – putative allelopathic compounds in Solidago altissima – in response to competition. Polyacetylenes were found in natural soil surrounding S. altissima patches within the range of concentration known to inhibit competitor growth. Individual S. altissima plants with higher polyacetylene concentration in roots suppressed the growth of the competitor plants more, suggesting that root polyacetylene levels proximate plants’ allelopathic capacity. Competition induced polyacetylenes in a context‐dependent manner: Whereas introduced Japanese and Australian populations of S. altissima had higher constitutive concentration of polyacetylenes than the native North American populations, inducibility was observed only in Australian plants, where the population is still at an early stage of invasion. Also, induction became more prominent under nutrient depletion, where enhanced allelopathy may be particularly beneficial for suppressing a competitor's exploitative capacity. Finally, we found weak evidence for a tradeoff between constitutive and induced polyacetylenes.The observed patterns suggest that allelopathic plants could respond to competition by inducing allelochemical production, but the benefit of such plasticity may vary across time and space. Shifts in competitor communities in introduced range over time may shape plant's plastic responses to competition, while variation in resource availability may alter competitive environment to influence the degree to which plants induce allelopathy.