Showing papers on "Allelopathy published in 2014"
TL;DR: The present review highlights the role of PGPR strains, specifically referring to allelochemicals produced and molecular mechanisms, and concludes that further research to fine tune combinations of alleLochemicals, plant-microbe-pathogen interaction will ultimately lead to better disease control.
207 citations
TL;DR: The results suggest that pathogenic fungal accumulation at the expense of such beneficial microorganisms as plant growth promoting rhizobacteria, mycorrhizal fungi induced byRoot exudates, rather than direct autotoxicity induced by root exudate, might represent the principal cause underlying the soil sickness associated with peanut plants.
Abstract: The quantity and quality of peanut yields are seriously compromised by consecutive monoculture in the subtropical regions of China. Root exudates, which represent a growth regulator in peanut–soil feedback processes, play a principal role in soil sickness. The growth inhibition of a species in an in vitro bioassay enriched with root exudates and allelochemicals is commonly viewed as evidence of an allelopathic interaction. However, for some of these putative examples of allelopathy, the results have not been verified in more natural settings with plants continuously growing in soil. In this study, the phenolic acids in peanut root exudates, their retention characteristics in an Udic Ferrosol, and their effects on rhizosphere soil microbial communities and peanut seedling growth were studied. Phenolic acids from peanut root exudates were quickly metabolized by soil microorganisms and did not accumulate to high levels. The peanut root exudates selectively inhibited or stimulated certain communal bacterial and fungal species, with decreases in the relative abundance of the bacterial taxa Gelria glutamica, Mitsuaria chitosanitabida, and Burkholderia soli and the fungal taxa Mortierella sp. and Geminibasidium hirsutum and increases in the relative abundance of the bacterial taxon Desulfotomaculum ruminis and the fungal taxa Fusarium oxysporum, Bionectria ochroleuca and Phoma macrostoma. The experimental application of phenolic acids to non-sterile and sterile soil revealed that the poor performance of the peanut plants was attributed to changes in the soil microbial communities promoted by phenolic acids. These results suggest that pathogenic fungal accumulation at the expense of such beneficial microorganisms as plant growth promoting rhizobacteria, mycorrhizal fungi induced by root exudates, rather than direct autotoxicity induced by root exudates, might represent the principal cause underlying the soil sickness associated with peanut plants. We hope that our study will motivate researchers to integrate the role of soil microbial communities in allelopathic research, such that their observed significance in soil sickness during continuous monocropping of fields can be further explored.
138 citations
TL;DR: The results suggest that if invasive species release allelopathic compounds that suppress germination, they do so to a similar degree as the native plant community.
Abstract: The ability of some invasive plant species to produce biochemical compounds toxic to native species, called allelopathy, is thought to be one of the reasons for their success when introduced to a novel range, an idea known as the Novel Weapons Hypothesis. However, support for this hypothesis mainly comes from bioassays and experiments conducted under controlled environments, whereas field evidence is rare. In a field experiment, we investigated whether three plant species invasive in Europe, Solidago gigantea, Impatiens glandulifera and Erigeron annuus, inhibit the germination of native species through allelopathy more than an adjacent native plant community. At three sites for each invasive species, we compared the germination of native species that were sown on invaded and non-invaded plots. Half of these plots were amended with activated carbon to reduce the influence of potential allelopathic compounds. The germination of sown seeds and of seeds from the seedbank was monitored over a period of 9 weeks. Activated carbon generally enhanced seed germination. This effect was equally pronounced in invaded and adjacent non-invaded plots, indicating that invasive species do not suppress germination more than a native plant community. In addition, more seeds germinated from the seedbank on invaded than on non-invaded soil, probably due to previous suppression of germination by the invasive species. Our field study does not provide evidence for the Novel Weapons Hypothesis with respect to the germination success of natives. Instead, our results suggest that if invasive species release allelopathic compounds that suppress germination, they do so to a similar degree as the native plant community.
89 citations
TL;DR: It is concluded that allelopathy in the E. urophylla plantation was selective, which inhibited the growth of the native tree species but had no significant influence on the introduced A. lebbeck species, which is suggested to be a potential choice for the establishment of mixed stands with Eucalyptus.
58 citations
TL;DR: These results are the first experimental evidence for a symbiotic relationship between plants and fungal endophytes affecting allelopathic interactions between competing plants, and provide insight into the mechanisms by which fungalendophytes may increase the competitive ability of their hosts.
Abstract: Endophytic plant symbionts can have powerful effects on the way their hosts interact with pathogens, competitors, and consumers. The presence of endophytes in plants can alter food webs, community composition and ecosystem processes, suggesting that endophyte-plant symbioses may represent unique forms of extended phenotypes. We tested the impact of the fungal endophyte Alternaria alternata (phylotype CID 120) on the allelopathic effect of the invasive forb Centaurea stoebe when in competition with the North American native bunchgrass Koeleria macrantha in a greenhouse competition experiment. The allelopathic effect of C. stoebe on K. macrantha when infected with the fungal endophyte was more than twice that of endophyte-free C. stoebe. However, this allelopathic effect was a small part of the very large competitive effect of C. stoebe on K. macrantha in all treatments, likely because of the priority effects in our experimental design. To our knowledge, these results are the first experimental evidence for a symbiotic relationship between plants and fungal endophytes affecting allelopathic interactions between competing plants, and thus provide insight into the mechanisms by which fungal endophytes may increase the competitive ability of their hosts.
58 citations
TL;DR: The first demonstration of induced allelopathy in a seaweed, or of competitors reducing seaweed chemical defences against herbivores, is demonstrated, suggesting that the chemical ecology of coral–seaweed–herbivore interactions can be complex and nuanced.
Abstract: Many seaweeds and terrestrial plants induce chemical defences in response to herbivory, but whether they induce chemical defences against competitors (allelopathy) remains poorly understood. We evaluated whether two tropical seaweeds induce allelopathy in response to competition with a reef-building coral. We also assessed the effects of competition on seaweed growth and seaweed chemical defence against herbivores. Following 8 days of competition with the coral Porites cylindrica, the chemically rich seaweed Galaxaura filamentosa induced increased allelochemicals and became nearly twice as damaging to the coral. However, it also experienced significantly reduced growth and increased palatability to herbivores (because of reduced chemical defences). Under the same conditions, the seaweed Sargassum polycystum did not induce allelopathy and did not experience a change in growth or palatability. This is the first demonstration of induced allelopathy in a seaweed, or of competitors reducing seaweed chemical defences against herbivores. Our results suggest that the chemical ecology of coral–seaweed–herbivore interactions can be complex and nuanced, highlighting the need to incorporate greater ecological complexity into the study of chemical defence.
57 citations
TL;DR: The spectroscopic data showed that the major compounds were sesquiterpene lactones, Aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth.
Abstract: Cardoon (Cynara cardunculus L.) is a native plant to the Iberian Peninsula and the European Atlantic coast and invasive in American environments. Different solvents were used to perform cardoon extracts that were tested in phytotoxic bioassays. The ethyl acetate extract had the highest inhibitory activity so this was tested on the germination and growth of standard target species (lettuce, watercress, tomato, and onion) and weeds (barnyardgrass and brachiaria). The ethyl acetate extract was very active on root growth in both standard target species and weeds and it was therefore fractionated by chromatography. The spectroscopic data showed that the major compounds were sesquiterpene lactones. Aguerin B, grosheimin, and cynaropicrin were very active on etiolated wheat coleoptile, standard target species, and weed growth. The presence of these compounds explains the bioactivity of the ethyl acetate extract. The strong phytotoxicity of these compounds on important weeds shows the potential of these compounds as natural herbicide models.
55 citations
TL;DR: Findings suggest that the release of 2-MNQ may contribute to the invasion success of I. glandulifera and support the novel weapons hypothesis.
Abstract: Exploring the effects of allelopathic plant chemicals on the growth of native vegetation is essential to understand their ecological roles and importance in exotic plant invasion. Naphthoquinones have been identified as potential growth inhibitors produced by Impatiens glandulifera, an exotic annual plant that recently invaded temperate forests in Europe. However, naphthoquinone release and inhibitory potential have not been examined. We quantified the naphthoquinone content in cotyledons, leaves, stems, and roots from plants of different ages of both the invasive I. glandulifera and native Impatiens noli-tangere as well as in soil extracts and rainwater rinsed from leaves of either plant species by using ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS). We identified the compound 2-methoxy-1,4-naphthoquinone (2-MNQ) exclusively in plant organs of I. glandulifera, in resin bags buried into the soil of patches invaded by I. glandulifera, and in rainwater rinsed from its leaves. This indicates that 2-MNQ is released from the roots of I. glandulifera and leached from its leaves by rain. Specific bioassays using aqueous shoot and root extracts revealed a strong inhibitory effect on the germination of two native forest herbs and on the mycelium growth of three ectomycorrhiza fungi. These findings suggest that the release of 2-MNQ may contribute to the invasion success of I. glandulifera and support the novel weapons hypothesis.
55 citations
TL;DR: The characterization of a complete allelochemical pathway involving benzoxazinones, which are known to participate in allelopathic plant defense interactions of several plants of high agronomic interest, is reported.
Abstract: Allelopathy is a biological phenomenon in which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. Allelopathy has been the subject of a great deal of research in chemical ecology since the 1930s. The characterization of the factors that influence this phenomenon has barely been explored, mainly due to the complexity of this area. The main aim of the research carried out to date has been to shed light on the importance of these interactions in agroecosystems, especially in relation to the interactions between crops and weeds. Herein we report the characterization of a complete allelochemical pathway involving benzoxazinones, which are known to participate in allelopathic plant defense interactions of several plants of high agronomic interest. The production of the defense chemicals by a donor plant (crop), the route and transformations of the chemicals released into the environment, and the uptake and phytotoxic effects on a target plant (weed) were all monitored. The results of this study, which is the first of its kind, allowed a complete dynamic characterization of the allelopathic phenomenon for benzoxazinones.
54 citations
TL;DR: The results indicate that A. scholaris pentacyclic triterpenoids influence the growth of neighboring weeds by inhibiting seed germination, radicle growth, and functioning of photosystem II.
Abstract: Alstonia scholaris is a tropical evergreen tree native to South and Southeast Asia. Alstonia forests frequently lack understory species. However, potential mechanisms—particularly the allelochemicals involved—remain unclear. In the present study, we identified allelochemicals of A. scholaris, and clarified the role of allelopathic substances from A. scholaris in interactions with neighboring plants. We showed that the leaves, litter, and soil from A. scholaris inhibited growth of Bidens pilosa—a weed found growing abundantly near A. scholaris forests. The allelochemicals were identified as pentacyclic triterpenoids, including betulinic acid, oleanolic acid, and ursolic acid by using 1H and 13C-NMR spectroscopy. The half-maximal inhibitory concentration (IC50) for radicle growth of B. pilosa and Lactuca sativa ranged from 78.8 μM to 735.2 μM, and ursolic acid inhibited seed germination of B. pilosa. The triterpenoid concentrations in the leaves, litter, and soil were quantified with liquid chromatography-electrospray ionization/tandem mass spectrometry. Ursolic acid was present in forest soil at a concentration of 3,095 μg/g, i.e., exceeding the IC50. In the field, ursolic acid accumulated abundantly in the soil in A. scholaris forests, and suppressed weed growth during summer and winter. Our results indicate that A. scholaris pentacyclic triterpenoids influence the growth of neighboring weeds by inhibiting seed germination, radicle growth, and functioning of photosystem II.
47 citations
TL;DR: The results suggest that the aqueous extract of S. oleraceus has an allelopathic effect on some weeds, and its usefulness as a bioherbicide therefore merits further study.
Abstract: We assessed the allelopathic effects of the aqueous extract of Sonchus oleraceus dry shoots on the germination and seedling growth of Trifolium alexandrinum, three weed species (Brassica nigra, Chenopodium murale and Melilotus indicus) and S. oleraceus itself. We assayed four different concentrations of the aqueous extract (w v −1 ): 1%, 2%, 3% and 4%. To determine whether the effects of the extract were attributable to the presence of allelopathic compounds, its osmotic potential or both, we prepared concentrations of polyethylene glycol (PEG) with osmotic potentials equivalent to those of the aqueous extract. All concentrations of the plant extract completely inhibited the germination and seedling growth of C. murale. The lowest concentration of the plant extract partially inhibited germination and seedling growth of B. nigra, M. indicus and S. oleraceus, whereas the higher concentrations inhibited those parameters completely. The germination of T. alexandrinum was not affected by the aqueous extract at 1% or 2%. In general, the aqueous extracts were more effective in inhibiting seed germination and seedling growth than were the PEG solutions. Phytochemical analyses revealed that phenols and alkaloids were the most abundant compounds in S. oleraceus dry matter. Our results suggest that the aqueous extract of S. oleraceus has an allelopathic effect on some weeds, and its usefulness as a bioherbicide therefore merits further study.
TL;DR: It is found that soil sterilization significantly increased biomass of native species and did not affect the invasive species’ biomass and that invasive E. adenophora and C. odorata created a belowground feedback that may be a mechanism contributing to their success as invasive species.
Abstract: Successful invasion by exotic plant species can modify the abundance and composition of soil microbial communities. Eupatorium adenophora and Chromolaena odorata are exotics that have become highly invasive plants in China. Several studies have investigated mechanisms of their successful invasions including phenotypic plasticity, genetic differentiation, and allelopathy, but little is known about their effects on soil microorganisms. Moreover, whether soil microbial community changes could cause feedback effects on these plant species is also not known. We seek a belowground microbiological mechanism supporting successful invasions by these exotic plants. In this study, two invasive (E. adenophora and C. odorata) and two native plant species (Eupatorium japonicum and Eupatorium heterophyllum) were used to compare the soil feedback (on plant growth) before and after soil sterilization and from plant-root exudates. Bacterial and fungal biomass and community composition were also examined. We found that soil sterilization significantly increased biomass of native species and did not affect the invasive species’ biomass. After root exudates from these plants had acted on the soil biota for 10 months, soil sterilization significantly decreased the growth of E. adenophora and C. odorata and continued to significantly increase the biomass of two native species. Denaturing gradient gel electrophoresis revealed that these four plant species modified fungal rather than bacterial communities in soil. Higher abundance of Paraglomus sp. in soil with C. odorata is likely to provide C. odorata roots with more soil nutrients. Considered together, these results strongly suggest that invasive E. adenophora and C. odorata created a belowground feedback that may be a mechanism contributing to their success as invasive species.
TL;DR: Analysis of canola germplasm suggests that highly allelopathic canola genotypes can be potential for controlling weeds such as annual ryegrass in integrated weed management programs.
Abstract: The allelopathic activity of canola (Brassica napus) germplasm was investigated using the important Australian weed, annual ryegrass (Lolium rigidum) as the target species. Three different canola plant densities (10, 20, and 30 seedlings/beaker) of each of 70 world-wide genotypes were tested in vitro in close proximity to annual ryegrass seedlings. The allelopathic activity of canola, as measured by reduction in annual ryegrass root and shoot growth, increased with canola crop seedling densities. Density did not consistently influence shoot length of annual ryegrass. Greater shoot length suppression was observed in genotype cv. Rivette and BLN3343CO0402. The Australian genotype cv. Av-opal and the breeding line Pak85388-502 suppressed root length of ryegrass more than other genotypes, even at low densities. At the lowest density, the least allelopathic genotypes were cv. Barossa and cv. Cescaljarni-repka, although they became more allelopathic at higher density. An overall inhibition index was calculated to rank each of the canola genotypes. There were significant differences between canola genotypes in their ability to inhibit root and shoot growth in ryegrass. Considerable genetic variation exists among canola genotypes for their allelopathic effects on annual ryegrass. Further investigation is required to determine the allelopathic mechanisms, particularly to identify the responsible allelochemical(s) and the gene(s) controlling the trait. This research suggests that highly allelopathic canola genotypes can be potential for controlling weeds such as annual ryegrass in integrated weed management programs.
TL;DR: It is found that A-AMF facilitated the invasion of S. canadensis through decreasing competitiveness of the native plant K. striata, and can be used to improve the understanding of an ecosystem-based perspective towards exotic plant invasion.
Abstract: The significance of arbuscular mycorrhizal fungi (AMF) in the process of plant invasion is still poorly understood We hypothesize that invasive plants would change local AMF community structure in a way that would benefit themselves but confer less advantages to native plants, thus influencing the extent of plant interactions An AMF spore community composed of five morphospecies of Glomus with equal density (initial AMF spore community, I-AMF) was constructed to test this hypothesis The results showed that the invasive species, Solidago canadensis , significantly increased the relative abundance of G geosperum and G etunicatum (altered AMF spore community, A-AMF) compared to G mosseae , which was a dominant morphospecies in the monoculture of native Kummerowia striata The shift in AMF spore community composition driven by S canadensis generated functional variation between I-AMF and A-AMF communities For example, I-AMF increased biomass and nutrient uptake of K striata in both monocultures and mixtures of K striata and S canadensis compared to A-AMF In contrast, A-AMF significantly enhanced root nitrogen (N) acquisition of S canadensis grown in mixture Moreover, mycorrhizal-mediated 15 N uptake provided direct evidence that I-AMF and A-AMF differed in their affinities with native and invading species The non-significant effect of A-AMF on K striata did not result from allelopathy as root exudates of S canadensis exhibited positive effects on seed germination and biomass of K striata under naturally occurring concentrations When considered together, we found that A-AMF facilitated the invasion of S canadensis through decreasing competitiveness of the native plant K striata The results supported our hypothesis and can be used to improve our understanding of an ecosystem-based perspective towards exotic plant invasion
TL;DR: Results indicated that some phytotoxic compounds from roots of S. chamaejasme may be involved in the potential allelopathic behavior of this widespread weed.
TL;DR: New lead natural herbicides for the management of parasitic weeds to be identified are identified after the effect of metabolites belonging to different classes of natural compounds on broomrape seed germination and radicle development was assayed in vitro.
Abstract: Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which cause heavy yield losses on important crops. The development of herbicides based on natural metabolites from microbial and plant origin, targeting early stages on parasitic plant development, might contribute to the reduction of broomrape seed bank in agricultural soils. Therefore, the effect of metabolites belonging to different classes of natural compounds on broomrape seed germination and radicle development was assayed in vitro. Among the metabolites tested, epi-sphaeropsidone, cyclopaldic acid, and those belonging to the sesquiterpene class induced broomrape germination in a species-specific manner. epi-Epoformin, sphaeropsidin A, and cytochalasans inhibited germination of GR24-treated broomrape seeds. The growth of broomrape radicle was strongly inhibited by sphaeropsidin A and compounds belonging to cyclohexene epoxide and cytochalasan classes. Broomrape radicles treated with epi-sphaeropsidone developed a l...
TL;DR: It is suggested that hyphal networks increase the effectiveness of allelochemicals in natural systems and play a crucial role in chemical interaction processes and hence influence plant community structure.
Abstract: Summary
Allelopathy is a phenomenon where plants have deleterious effects on growth of surrounding plants through the production of chemical substances. Soil hyphae of arbuscular mycorrhizal fungi may enhance transport processes of allelochemicals by providing ‘highways’ connecting plants below-ground.
In three studies ranging from high ecological realism to experimental control, we showed that the presence of mycorrhizal hyphae may strongly contribute to the transport of allelochemicals. We analysed the accumulation of naturally released juglone in the field in intact or disrupted hyphal connections and determined its growth reducing effects on sensitive target plants in a bioassay. Secondly, we tested the effects of Juglans regia leaf litter addition in the presence or absence of the mycorrhizal fungus Rhizophagus irregularis on target plants, and finally, we added pure juglone to Lycopersicon lycopersicum plants in the presence or absence of Rhizophagus.
Throughout, we found increased juglone transfer if mycorrhizal hyphae were present, resulting in reduced growth of target plants.
Our results point to mycorrhizal hyphae playing an important role in extending the bioactive zone of allelochemicals. We suggest that hyphal networks increase the effectiveness of allelochemicals in natural systems and play a crucial role in chemical interaction processes and hence influence plant community structure.
TL;DR: Results of the study indicate complex mechanism of phytotoxic effect of juglone in lettuce root tips and may indicate mechanism of allelopathic activity of this compound.
TL;DR: It is suggested that hyphal connections, mostly formed by arbuscular mycorrhizal fungi, increase the effectiveness of allelochemicals in natural systems and can play a crucial role in chemical interaction processes in the soil.
Abstract: Allelopathy is a biological phenomenon where plants have harmful effects on growth of surrounding plants through the production of chemical substances. Here we focus on allelochemical processes which operate belowground, can influence plant interactions and therefore potentially affect plant community structure. Soil hyphae of arbuscular mycorrhizal fungi (AMF) may enhance transport processes in the soil matrix by providing direct connections between plants facilitating infochemical exchange. In a two-component field study we showed that soil hyphae likely play a crucial role in movement of allelochemicals in natural soils and greatly expand bioactive zones by providing effective transport pathways for chemical compounds. First, we tested the effects of Juglans regia leaf litter extract addition in intact or disrupted hyphal networks and simultaneously determined growth reducing effects on sensitive Lycopersicon lycopersicum plants. Second, we analyzed the effect of juglone on tomato by directly adding leaf litter. In both approaches we found an increase of juglone transport if a hyphal network was present, resulting in reduced growth of target plants. Our results, together with previous work, add to the body of evidence for hyphae of soil fungi playing an important role in the transfer of allelochemicals and effectively acting as transport highways in the field. We suggest that hyphal connections, mostly formed by AMF, increase the effectiveness of allelochemicals in natural systems and can play a crucial role in chemical interaction processes in the soil.
TL;DR: The results suggest the existence of allelopathic effects, direct and/or indirect, of F. japonica on the growth of Salicaceae species cuttings, but the three species were not equally affected, suggesting that the choice of resistant species could be crucial for restoration success.
TL;DR: The soil microbial carbon and nitrogen analyses suggested that wheat could create an active microhabitat with high activities of key soil enzymes such as urease, catalase, sucrase, and dehydrogenase and the rhizosphere soil microbes contributed to allelopathic potential of wheat by positive feedback.
Abstract: Soil micro-circumstance and biological stress resistance were studied to validate our hypothesis that the allelopathic potential that was enhanced by breeding resulted partially from rhizophere microbes associated with the different varieties. The rhizosphere soils from four wheat genotypes with different allelopathic potential were collected so as to compare their soil micro-environments and bio-pressure tolerances. The levels of these three categories such as bacteria, fungi, and actinomycetes ranged among 1.54–26.59 × 106, 0.43–4.12 × 104, and 1.36–18.25 × 105 CFU/g soil, respectively. Wheat 22 Xiaoyan with greater allelopathic potential had higher levels of microorganisms than the other three genotypes having weak allelopathy. The soil microbial carbon and nitrogen analyses suggested that wheat could create an active microhabitat with high activities of key soil enzymes such as urease, catalase, sucrase, and dehydrogenase. Using the approximate concentrations detected in wheat rhizosphere soils, the leachates of all four wheat materials significantly inhibited the growth of the weed Descurainia sophia and take-all pathogen Gaeumannomyces graminis var. Tritici.
Wheat exudates provided carbon and nitrogen resources for the relevant microorganism. Meanwhile, the rhizosphere soil microbes contributed to allelopathic potential of wheat by positive feedback.
TL;DR: Reductions in germination of native seeds strongly support direct allelopathic effects of invasive grass species B. ischaemum on native grass germination, growth, and survival, and greater phenolic content in native grass leachates suggest allelelopathic biochemical production may not be unique to non-native species and may be a mechanism for maintenance of plant species biodiversity in native systems.
Abstract: Bothriochloa spp. are non-native warm-season grasses invading native grasslands of the southern and central Great Plains, altering ecological services these grasslands supply. Our study investigated potential allelopathic effects of the invasive grass species B. ischaemum on native grass germination, growth, and survival. Leachate or litter from Andropogon gerardii (native) or B. ischaemum were applied to two native grass species (A. gerardii; Schizachyrium scoparium). Leachate and litter were also added to B. ischaemum and a water control was included. Germination, above- and belowground biomass, and survival were determined. Application of B. ischaemum leachate or litter significantly reduced the germination, growth, and survival of both A. gerardii and S. scoparium but had no conspecific effects, while A. gerardii treatments had no effect on any species. Bothriochloa spp. may gain a competitive advantage through allelopathic biochemicals. It is unclear if these allelopathic effects directly hinder competitors or indirectly hinder them through alterations in soil microbial communities, however, reductions in germination of native seeds strongly support direct allelopathic effects. Greater phenolic content in native grass leachates suggest allelopathic biochemical production may not be unique to non-native species and may be a mechanism for maintenance of plant species biodiversity in native systems.
TL;DR: Leaf extracts showed more phytotoxicity when compared with other organs of boneseed, suggesting a mechanism of allelopathic impact through excessive reactive oxygen species (ROS) production, which helps to explain the mechanism of invasion by boneseed.
TL;DR: Overall, the allelopathic potential of species decreased with life span, roughly following the successional transitions from short-lived to long-lived herbs and to woody species, indicating that allelopathy may be a quite common ecological strategy in plants and is equally common in both native and non-native species.
Abstract: Allelopathy, plant–plant interactions mediated through chemical production, is an active area of ecological research. Despite this widespread interest, we still lack community scale information on the prevalence of this interaction and the types of species that may be expected to be allelopathic. To address this research need, the allelopathic potential of 65 plant species from all stages of succession in the Piedmont region of New Jersey, USA, was determined with laboratory bioassays. The strength of each species’ allelopathic activity was then related to life form, origin, and fundamental plant traits. The vast majority of species tested exhibited significant allelopathic effects in the bioassays, with many of these having fairly strong effects. Overall, the allelopathic potential of species decreased with life span, roughly following the successional transitions from short-lived to long-lived herbs and to woody species. Herbaceous species on average were more allelopathic than woody species, but there was no difference between native and non-native species once life form was accounted for. In a principal components analysis, allelopathy was associated with other plant traits, but these relationships differed between woody and herbaceous species. Allelopathic potential was positively associated with plant height in herbaceous species, but negatively associated with height, leaf mass, and seed mass in woody species. These results indicate that allelopathy may be a quite common ecological strategy in plants and is equally common in both native and non-native species. The linkage of allelopathy with other plant functional traits suggests that allelopathy can and should be integrated into the broader suite of plant strategies that are studied.
TL;DR: It can be concluded that both shrubs possess allelopathic potential, with H. psiadioides showing stronger effects and both plants showed a decrease in phytotoxicity in summer.
TL;DR: The results hereby presented provide insight into the allelopathic action of the medicinal and wild plants of Iran and serves as benchmark information for further research on the characterization of the allelochemicals in these plants.
Abstract: Plants have the ability to interfere with other organisms in their immediate environment, a phenomenon called allelopathy. Allelopathy is a common phenomenon in nature (Qian Chemosphere 75(368):375, 2009). The use of allelopathic compounds for the development of new agrochemicals has several benefits as opposed to common synthetic products. Cognizant of reports on the allelopathic action of medicinal and invasive plants, 118 Iranian plants from 104 species which belongs to 34 families have been screened for allelopathic volatiles by the dish pack method. A total of 118 plants (104 species) belonging to 34 families were collected in 2009 from the tropical, subtropical and temperate regions of Iran. The Dish pack method as described by Fujii et al. (Weed Sci Technol 45(80):81, 2000) utilized for screening the presence of allelopathic volatiles released from different parts of the plant specimen. This method can be used to recognize allelopathic properties very easy and quickly. Results of bioassay with lettuce seed (Lactuca sativa cv. Great Lakes 366) revealed that 23 species elicited growth inhibitory action with the greatest (≥96% reduction) observed in the inflorescences of Achillea wilhelmsii and Achillea filipendula. Furthermore, a high suppression (83–95 %) in radicle elongation was observed in lettuce exposed to: flowers of Achillea nobilis, Lavandula vera, and Perovskia abrotanoides; fruit of Ruta graveolens; seeds of Bunium persicum and Trachyspermum copticum; leaves of Achillea biebersteinii, Pulicaria gnaphalodes, Ziziphora clinopodioides, Zataria multiflora; gum of Ferula foetida; and stigma of Crocus sativus. On the other hand, 14 species instead exhibited growth-promoting properties. Of these, the greatest promoting effect were exhibited by the leaves of Cardaria draba, Verbascum speciosum and Urtica dioica eliciting 69 %, 56 %, and 53 %, respectively, which had longer radicles compare to the control. The results hereby presented provide insight into the allelopathic action of the medicinal and wild plants of Iran. Data herein reported serves as benchmark information for further research on the characterization of the allelochemicals in these plants.
TL;DR: The present study characterizes the community of Brassica tournefortii Gouan in reclaimed areas of the Nile Delta of Egypt to determine its ecological amplitude, soil factors controlling its distribution, and its allelopathic control.
Abstract: Land reclamation causes weedy species to replace wild plant species. The present study characterizes the community of Brassica tournefortii Gouan in reclaimed areas of the Nile Delta of Egypt to determine its ecological amplitude, soil factors controlling its distribution, and its allelopathic control. The plant communities dominated by B. tournefortii were investigated in 60 sites. The importance value of each species based on cover and density was determined. Data were treated by multivariate analyses. Soils representing each community were analyzed. The allelopathic effects of Conyza bonariensis (L.) Cronquist, Trianthema portulacastrum L., and Pulicaria undulata (L.) C.A.Mey. and their mixtures on germination and seedling growth of B. tournefortii were investigated. Total phenolics, tannins, alkaloids, flavonoids, and saponins were estimated. The applications of TWINSPAN classification based on 140 species led to recognition of 4 vegetation clusters; 3 were dominated by B. tournefortii and 1 was codominated by Malva parviflora L. and Senecio glaucus L. Canonical correspondence analysis demonstrated that CaCO3, soil texture, and water holding capacity contributed significantly to the distribution of species. The water extracts of T. portulacastrum, C. bonariensis, and P. undulata could be applied at a concentration of 10 g/L for the management of this weed.
TL;DR: Results suggest that those phytotoxic substances may contribute to the allelopathic effect caused by B. brizantha and may be involved in the invasion of this species.
TL;DR: It can be concluded that the powder and extracts of the tested species have an herbicidal potential against redroot pigweed and could be used as natural herbicides and mulches.
Abstract: The study was conducted to determine the allelopathic effects of Crocus sativus L., Ricinus communis L., Nicotiana tabacum L., Datura inoxia Mill., Nerium oleander L., and Sorghum vulgare L. on the germination and growth of Amaranthus retroflexus (redroot pigweed). Powder and aqueous extracts of these plants were used to run the experiment under laboratory and greenhouse conditions. In the labora- tory, all aqueous extracts showed a significant inhibitory effect on the germination, seedling length and weight of redroot pigweed plants. The most allelopathic against the redroot pigweed were R. communis, N. tabacum, and D. inoxia. In the greenhouse experiment, extracts and the powder of these plants also showed significant inhibitory effects on pigweed dry weight, height, leaf area, number of survivor plants, and amount of chlorophyll. In the germination bioassay and application of powder, the inhibitory effect was dosage dependent - the higher the concentration, the strongest the inhibitory effect. From the obtained results, it can be concluded that the powder and extracts of the tested species have an herbicidal potential against redroot pigweed and could be used as natural herbicides and mulches.
TL;DR: The findings suggest sympatric association may contribute to evolution of species‐specific BR and that seed traits are important in its development, and the underlying mechanism affecting these germination decisions may be simple phytochemical‐induced hormonal regulation.
Abstract: Summary
Allelopathy has traditionally been viewed as a phytotoxic disruption of recipient plant metabolism, and allelopathic effects are generally strongest on species lacking historic exposure to particular phytotoxins (Novel Weapons Hypothesis). However, mounting evidence suggests phytochemical-induced germination inhibition can be an adaptive response to competitive conditions, not the consequence of toxin exposure. That is, selective advantages can exist for seeds to chemically recognize potential competitor presence and defer germination until better establishment conditions occur. This Biochemical Recognition Hypothesis (BRH) contrasts the allelopathy paradigm by predicting greater germination inhibition following phytochemical exposure of sympatric compared to allopatric species.
In a glasshouse, we grew 12 species native to Argentinean and North American grasslands and tested whether phytochemical leachates from co-occurring species reduced seedling emergence more than those having no historic association.
Two species had 13% and 27% emergence reductions following leachate exposure of sympatric relative to allopatric species, supporting species-specific BR. Intraspecific leachates reduced emergence more than those from heterospecifics, suggesting within-species BR may be common. Only the four smallest seeded species exhibited heterospecific BR responses, suggesting that selection for assessing local competition potential may intensify as seed reserves decline. Importantly, leachate origin did not affect seedling biomass nor accelerate germination, indicating a non-toxic biochemical effect on germination reduction but not growth.
Synthesis. Coupling ample theoretical support with empirical evidence here and elsewhere, an ‘eavesdrop-and-wait' competition avoidance strategy could be a common phenomenon. Our findings suggest sympatric association may contribute to evolution of species-specific BR and that seed traits are important in its development. The underlying mechanism affecting these germination decisions may be simple phytochemical-induced hormonal regulation. Factors preclude BR from being ubiquitous but nonetheless, BR provides a potentially powerful mechanism by which some plant populations and the spatiotemporal diversity of some communities are structured. Lastly, allelopathy may be erroneously invoked when phytochemical-induced germination reduction occurs but a toxicity mechanism has not been elucidated. In many cases, this fits more with the BRH than classic allelopathy.