Showing papers on "Allelopathy published in 2009"
TL;DR: The results suggest that the urease, invertase, dehydrogenase and polyphenoloxidase activities of paddy soils may be positively influenced by allelopathic rice variety through the release of allelochemicals.
196 citations
TL;DR: It is shown that the allelopathic effects of m-tyrosine, which could be seen in sterilized soil with particular plant species were significantly diminished when non-sterile soil was used, which points to an important role for rhizosphere-specific and bulk soil microbial activity in determining the outcome of this allelopathy interaction.
Abstract: Background: Allelopathy (negative, plant-plant chemical interactions) has been largely studied as an autecological process, often assuming simplistic associations between pairs of isolated species. The growth inhibition of a species in filter paper bioassay enriched with a single chemical is commonly interpreted as evidence of an allelopathic interaction, but for some of these putative examples of allelopathy, the results have not been verifiable in more natural settings with plants growing in soil. Methodology/Principal findings: On the basis of filter paper bioassay, a recent study established allelopathic effects of mtyrosine, a component of root exudates of Festuca rubra ssp. commutata. We re-examined the allelopathic effects of mtyrosine to understand its dynamics in soil environment. Allelopathic potential of m-tyrosine with filter paper and soil (nonsterile or sterile) bioassays was studied using Lactuca sativa, Phalaris minor and Bambusa arundinacea as assay species. Experimental application of m-tyrosine to non-sterile and sterile soil revealed the impact of soil microbial communities in determining the soil concentration of m-tyrosine and growth responses. Conclusions/Significance: Here, we show that the allelopathic effects of m-tyrosine, which could be seen in sterilized soil with particular plant species were significantly diminished when non-sterile soil was used, which points to an important role for rhizosphere-specific and bulk soil microbial activity in determining the outcome of this allelopathic interaction. Our data show that the amounts of m-tyrosine required for root growth inhibition were higher than what would normally be found in F. rubra ssp. commutata rhizosphere. We hope that our study will motivate researchers to integrate the role of soil microbial communities in bioassays in allelopathic research so that its importance in plant-plant competitive interactions can be thoroughly evaluated.
160 citations
TL;DR: The results suggest the possible use of these essential oils as natural herbicides in order to determine their activity against Amaranthus hybridus and Portulaca oleracea.
159 citations
TL;DR: The role of allelopathy in cyanobacteria ecology is still not well understood, and its clarification should benefit from carefully designed field studies, chemical characterization of allelochemicals and new methodological approaches at the “omics” level.
Abstract: Freshwater cyanobacteria produce several bioactive secondary metabolites with diverse chemical structure, which may achieve high concentrations in the aquatic medium when cyanobacterial blooms occur. Some of the compounds released by cyanobacteria have allelopathic properties, influencing the biological processes of other phytoplankton or aquatic plants. These kinds of interactions are more easily detectable under laboratory studies; however their ecological relevance is often debated. Recent research has discovered new allelopathic properties in some cyanobacteria species, new allelochemicals and elucidated some of the allelopathic mechanisms. Ecosystem-level approaches have shed some light on the factors that influence allelopathic interactions, as well as how cyanobacteria may be able to modulate their surrounding environment by means of allelochemical release. Nevertheless, the role of allelopathy in cyanobacteria ecology is still not well understood, and its clarification should benefit from carefully designed field studies, chemical characterization of allelochemicals and new methodological approaches at the "omics" level.
134 citations
TL;DR: It is concluded that there is no experimental support for allelopathy at prebloom densities, throwing doubts on allelopathic as a mechanism in bloom formation and it is suggested that the evolution of allelelopathy under field conditions may be unlikely even if based on cell–cell interactions.
Abstract: Many planktonic microalgae produce a range of toxins and may form harmful algal blooms. One hypothesis is that some toxins are allelopathic, suppressing the growth of competitors, and it has been suggested that allelopathy may be one important mechanism causing algal blooms. In a metaanalysis of recent experimental work, we looked for evidence that allelopathy may explain the initiation of algal blooms. With few exceptions, allelopathic effects were only significant at very high cell densities typical of blooms. We conclude that there is no experimental support for allelopathy at prebloom densities, throwing doubts on allelopathy as a mechanism in bloom formation. Most studies tested allelopathy using cell-free manipulations. With simple models we show that cell-free manipulations may underestimate allelopathy at low cell densities if effects are transmitted during cell–cell interactions. However, we suggest that the evolution of allelopathy under field conditions may be unlikely even if based on cell–cell interactions. The spatial dispersion of cells in turbulent flow will make it difficult for an allelopathic cell to receive an exclusive benefit, and a dispersion model shows that dividing cells are rapidly separated constraining clone selection. Instead, we propose that reported allelopathic effects may be nonadaptive side effects of predator–prey or casual parasitic cell–cell interactions.
133 citations
TL;DR: Because tree species responded divergently to soil conditioning, the endophyte symbiosis has the potential to alter plant succession and the future composition of forest communities.
Abstract: Summary 1. Non-native plants can alter both native microbe communities and ecosystem processes. These changes may indirectly affect native plant communities. We tested whether an invasive plant influences other plant species through above- and below-ground microbial associations. These factors have received less attention than direct competition for resources in research on plant invasions. 2. Previous work in the mid-western US revealed that the above-ground fungal endophyte ( Neotyphodium coenophialum ) in non-native tall fescue grass ( Lolium arundinaceum ) reduced establishment of native tree species, slowing plant succession from grassland to forest relative to communities lacking the symbiont. Here, we examined potential soil-mediated mechanisms underlying these negative impacts on trees. 3. We challenged nine tree species with soil conditioned by tall fescue grass either with (E+) or without (E‐) the symbiotic endophyte. We collected field soil from replicated, experimental E+ and E‐ field plots, sterilized half to eliminate soil microbes, then conditioned the soil in the greenhouse with either E+ or E‐ tall fescue. Individual tree seeds received one of five soil treatments: E‐ live, E‐ sterile, E+ live, E+ sterile, or no tall fescue conditioning (control). Tree survival and biomass were assessed after approximately 80 days. 4. Soil conditioning by E+ tall fescue reduced the biomass of three tree species ( Elaeagnus umbellata , Fraxinus pennsylvanica , Platanus occidentalis ) and the survival of P. occidentalis relative to conditioning by E‐ tall fescue. However, decreased biomass occurred only in live soil, suggesting indirect effects of the endophyte via altered soil microbes. In addition, two species ( F. pennsylvanica , Prunus serotina ) grew larger in both unconditioned soils and E‐ live soil relative to all other soil treatments, and two species ( Ailanthus altissima , P. occidentalis ) performed poorly in all soil treatments relative to unconditioned soil. Finally, three species did not significantly respond to any soil treatment ( Acer negundo , Quercus palustris , Cercis canadensis ). 5. Synthesis . Our results show that negative impacts of a non-native grass on native trees can depend on both above- and below-ground microbial associations. Because tree species responded divergently to soil conditioning, the endophyte symbiosis has the potential to alter plant succession and the future composition of forest communities.
103 citations
TL;DR: Two strategies for establishment of mixed stands of native species and eucalyptus are proposed: (1) direct seed-sowing is effective only for those species (e.g. D. regia) with high germination rates in natural conditions; (2) seedling transplants are more efficient approach for establishing species (E. sylvestris) with low Germination rates.
97 citations
Journal Article•
TL;DR: Mesquite (Prosposis juliflora) aqueous leaf extract, prepared by 25 gm and 50 gm powder of dry leaf dissolved in 500 ml of double distilled water, were tested for their allelopathic effects on seed germination and radicle length of Triticum aestivum var-Lok.
Abstract: Mesquite (Prosposis juliflora) aqueous leaf extract, prepared by 25 gm and 50 gm powder of dry leaf dissolved in 500 ml of double distilled water, were tested for their allelopathic effects on seed germination and radicle length of Triticum aestivum var-Lok Allelopathic effect of leaf extract of different concentrations (25 gm/500 ml (C ) and 50 grm/500ml (C ) of Prosopsis juliflora and its possible allelopathic effect tested in a 1 2 laboratory experiment ( Bundelkhand University, Jhansi The experiment was conducted in sterilizes Petri dish with a 24 h, 48 h, 72 h, 96 h and 120 h time interval for seed germination and 24 h, 48 h and 72 h for radicle length on an average of 25° C The effects of different concentrations of aqueous extract were compared to distilled water (Control C ) Aqueous effect caused pronounced inhibitory effect on seed germination and root length 0 of receptor plant Seed germination and root length results indicated that the inhibitory effect was proportion to the concentration of the extract Inhibitory effect was much pronounced radicle length rather than germination Hence, it could be concluded that the mesquite leaf aqueous extract contain water-soluble allelochemicals Which could inhibit the seed germination and reduce radicle length of wheat It is suggested that wheat should not be planted close to Prosopsis juliflora due to adverse effects on its growth
94 citations
TL;DR: Results from the present experimental results suggest that invasive S. canadensis may acquire spreading advantage in non-native habitat by using “novel weapons” to inhibit not only local plants but also soilborne pathogens.
87 citations
TL;DR: The allelopathic effects of T.angustifolia on a North American native wetland plant and its production of root biochemicals that appear to differ from those produced by a native congener are consistent with the possibility that T. angust ifolia may use a novel allelochemical in its invasion of North American wetlands.
Abstract: The direct competitive effects of exotic plants on natives are among the leading causes of plant extinctions worldwide. Allelopathy, one type of direct plant competition, has received relatively little research, particularly in aquatic and wetland systems, even though allelopathy can be a potent mechanism through which plant communities are structured. Typha angustifolia (narrow-leaved cattail) is an invasive exotic plant in North America that often forms monocultures in disturbed wetlands and is more invasive than native members of its genus. We tested whether T. angustifolia was allelopathic and whether it produced different biochemicals than a native congener by growing it with the native bulrush Bolboschoenus fluviatilis (river bulrush) in soil with and without activated carbon and by qualitatively and quantitatively comparing soluble phenolics produced in the roots of T. angustifolia and the native Typha latifolia (broad-leaved cattail). T. angustifolia had a strong allelopathic effect on B. fluviatilis, reducing the longest leaf length and root, shoot, and total biomass of B. fluviatilis. When the allelopathy of T. angustifolia was ameliorated by activated carbon, however, longest leaf length, ramet number, root biomass, shoot biomass, and total biomass of T. angustifolia were greatly reduced due to resource competition with B. fluviatilis. Furthermore, T. angustifolia produced different, but not more, soluble phenolics than T. latifolia suggesting that the identity of the phenolics is different between the two species rather than the concentrations. The allelopathic effects of T. angustifolia on a North American native wetland plant and its production of root biochemicals that appear to differ from those produced by a native congener are consistent with the possibility that T. angustifolia may use a novel allelochemical in its invasion of North American wetlands.
86 citations
TL;DR: Soil beneath M. micrantha had inhibitory effects on seed germination and seedling growth of test plant, and had significantly higher C, N, ammonia, net nitrification rate than those of open soil, while under the water control, the soil net mineralization rate was higher under T1, while lower under T2 and T3, but the extracts increased the soil nitrification rates under all the treatments.
Abstract: Allelopathy has been regarded as a mechanism for successful exotic plant invasion. However, it is not clear if and what effects of allelopathic substances may exert on soil nutrient. The exotic plant Mikania micrantha H.B.K. (M. micrantha) has invaded many forests in south China, and recent studies have suggested it has allelopathic potential for other plants and soil microbial community. Thus, we hypothesized that M. micrantha could influence soil nutrients and N transformation through allelopathy. We measured total C and N, NO3−, NH4+ and pH of the soil beneath M. micrantha and the adjacent open soil, and then measured the above soil properties after treating soil with 3 concentrations of aqueous extracts of M. micrantha (T1: 0.005 g ml−1; T2: 0.025 g ml−1; T3: 0.100 g ml−1). In addition, a bioassay was conducted to determine the allelopathic potential of the soil beneath M. micrantha. The results showed that M. micrantha significantly affected soil nutrients and N transformation. Soil beneath M. micrantha had inhibitory effects on seed germination and seedling growth of test plant, and had significantly higher C, N, ammonia, net nitrification rate than those of open soil. The plant extracts decreased soil pH, and T1 decreased it the most, and it increased soil C and N, and T1 represented the greatest increase in both C and N. The extracts also increased both NO3− and NH4+ in soil, whereas no significant difference existed among the 3 extract treatments. Compared to the water control, the soil net mineralization rate was higher under T1, while lower under T2 and T3. However, the extracts increased the soil nitrification rates under all the treatments (T1, T2 and T3). Our results suggest that the water soluble allelochemicals of M. micrantha improve soil nutrient availability, through which the invasive plant M. micrantha may successfully invade and establish in new habitats.
TL;DR: Results show that activated carbon should be handled with great care in ecological experiments on allelopathy because of possible confounding effects on the soil, and not only reduced potential allelopathic effects, but substantially changed the chemistry of the substrate.
TL;DR: AMF does not necessarily stimulate plant growth, direct plant defense by secondary metabolitesdoes not necessarily reduce potential benefits from AMF, and that AMF can enhance concentrations of root chemical defenses, but that these responses are plant genotype-dependent.
Abstract: Allelochemicals defend plants against herbivore and pathogen attack aboveground and belowground. Whether such plant defenses incur ecological costs by reducing benefits from plant mutualistic symbionts is largely unknown. We explored a potential trade-off between inherent plant chemical defense and belowground mutualism with arbuscular mycorrhizal fungi (AMF) in Plantago lanceolata L., using plant genotypes from lines selected for low and high constitutive levels of the iridoid glycosides (IG) aucubin and catalpol. As selection was based on IG concentrations in leaves, we first examined whether IG concentrations covaried in roots. Root and leaf IG concentrations were strongly positively correlated among genotypes, indicating genetic interdependence of leaf and root defense. We then found that root AMF arbuscule colonization was negatively correlated with root aucubin concentration. This negative correlation was observed both in plants grown with monocultures of Glomus intraradices and in plants colonized from whole-field soil inoculum. Overall, AMF did not affect total biomass of plants; an enhancement of initial shoot biomass was offset by a lower root biomass and reduced regrowth after defoliation. Although the precise effects of AMF on plant biomass varied among genotypes, plants with high IG levels and low AMF arbuscule colonization in roots did not produce less biomass than plants with low IG and high AMF arbuscule colonization. Therefore, although an apparent trade-off was observed between high root chemical defense and AMF arbuscule colonization, this did not negatively affect the growth responses of the plants to AMF. Interestingly, AMF induced an increase in root aucubin concentration in the high root IG genotype of P. lanceolata. We conclude that AMF does not necessarily stimulate plant growth, that direct plant defense by secondary metabolites does not necessarily reduce potential benefits from AMF, and that AMF can enhance concentrations of root chemical defenses, but that these responses are plant genotype-dependent.
TL;DR: The results suggest that allelopathy of root extract on belowground biomass might be greater than that of leaf extract for some species in contrast allelopathic of leaf Extract on below ground biomass might also be greaterthan that ofRoot extract for other species, at least for their effects on root growth of the target species.
Abstract: This study evaluates the relative contributions of leaves and roots to the belowground allelopathic effects of Mikania micrantha. The hypothesis that leaves contribute more to the allelopathic effect than roots was experimentally tested. We assessed the allelopathic effects of aqueous extracts from Mikania leaves and roots on the seed germination and seedling growth of two co-occurring woody plants in southern China, Lagerstroemia indica L. and Robinia pseudoacacia L. The results showed that the aqueous extracts from Mikania leaves and roots had inhibitory effects on the woody species. Allelopathic activity depended on the concentration of the extracts, target species, and the extract sources (i.e., leaves vs. roots of Mikania). Leaf extract showed stronger allelopathic effects than root extract on germination percentage, initial germination time, speed of germination, and shoot height; while root extract had greater allelopathic effects on roots than leaf extract. The latter phenomenon might greatly promote the invasion success of Mikania due to more direct and effective allelopathy of root. Our results suggest that allelopathy of root extract on belowground biomass might be greater than that of leaf extract for some species in contrast allelopathy of leaf extract on belowground biomass might also be greater than that of root extract for other species, at least for their effects on root growth of the target species.
TL;DR: The results demonstrate that the aqueous extracts from N. meyeri have allelopathic potential and should be evaluated as an allelelopathic species, presenting a risk or advantage to seed germination and seedling growth of crop or weed plants.
Abstract: In order to evaluate the allelopathic potential of Nepeta meyeri Benth., the effects of aqueous extracts (0.125, 0.25, 0.5, 1, 2.5 and 5%) prepared from roots and leaves of N. meyeri were studied on the seed germination and seedling growth of several economically important crops (barley, wheat, canola, safflower, and sunflower). Both the root and leaf extracts of N. meyeri caused a general phytotoxic effect on the seed germination and seedling growth of barley and sunflower at all concentrations. However, both the root and leaf extracts significantly increased the seedling growth of wheat, especially at the lower concentrations 0.125, 0.25 and 0.5%, whereas the higher concentrations had a neutral effect. The seed germination and the seedling growth of canola and safflower were also generally improved by both extracts, especially at lower concentrations. However, these advantages were not observed at higher concentrations, at which the extracts mostly had a phytotoxic effect on canola and safflower. The Allelopathic activity of N. meyeri depended on whether the extract was derived from the leaf or root parts of the plant. The maximum allelopathic effect occurred with leaf extracts. The results demonstrate that the aqueous extracts from N. meyeri have allelopathic potential and should be evaluated as an allelopathic species, presenting a risk or advantage to seed germination and seedling growth of crop or weed plants.
TL;DR: Criteria were set that can be adapted to the study of elemental allelopathy that should be included in investigations of elemental alleleopathy to avoid overreaching conclusions.
Abstract: Allelopathic interference between plants has generally been discussed in terms of the production of toxic complex biochemicals; however, complex biochemicals may not be the only substances plants use to interfere with one another. It has also been suggested that inorganic elements may be used in an allelopathic manner. If, through phytoenrichment or root exudates, a plant is able to increase the bioavailable levels of a particular element and tolerate the levels better than its neighbors, it can produce an allelopathic effect. Elemental allelopathy has been implicated as the cause for the success of a number of invasive weeds, including Acroptilon repens, Tamarix spp., Halogeton glomeratus, Salsola iberica, and Mesambryenthemum crystallinum. Phytoenrichment of elements can occur through hyperaccumulation and litter deposition and by altering rhizosphere chemistry. Reported cases of elemental allelopathy have involved three types of elements: heavy metals and soluble salts in terrestrial systems and elemental S in aquatic systems. For the most part, studies that have reported elemental allelopathy have been inconclusive. In order to prevent overreaching conclusions in the study of biochemical allelopathy, criteria were set that can be adapted to the study of elemental allelopathy. Of the studies reviewed, the most common criteria left uninvestigated were whether the plant was actually responsible for changing the concentration of the element and whether the increased levels of an element negatively affected other species. If the study of elemental allelopathy is to avoid the same problems often associated with the study of biochemical allelopathy, these criteria should be included in investigations of elemental allelopathy.
TL;DR: Eleven terpenes were isolated and identified and new structures were established by spectroscopic studies such as 1D- and 2D-NMR and MS analyses, and the potential allelopathic effects of these compounds on the Arabidopsis seeds germination were tested.
Abstract: The invasive plant Eupatorium adenophorum Spreng. (or Ageratina adenophora (Spreng.) King and Robinson) (Compositae) has caused great economic loss in China, especially the southwestern region, and is gravely threatening the native biodiversity. The aerial part of this plant was phytochemically investigated for its allelochemicals. Eleven terpenes (2 monoterpenes and 9 sesquiterpenes) were isolated and identified, which include a new monoterpene, (-)-(1R*,2S,*4R*,5S*)-3,3-dimethyl-5-hydroxybicyclo[2,2,1]hept-2-ylmethanol (1), two new cadinane sesquiterpenes, (-)-(5S*,6S*,7S*,9R*,10S*)-7-hydroxy-5,7-epidioxycadinan-3-ene-2-one (2) and (+)-(5S*,6R*,9R*,10S*)-5,6-dihydroxycadinan-3-ene-2,7-dione (3), and eight known terpene compounds (4, 6-12). The new structures were established by spectroscopic studies such as 1D- and 2D-NMR and MS analyses. Meanwhile, the potential allelopathic effects of these compounds on the Arabidopsis seeds germination were tested. Compounds 3 and 7 retarded the Arabidopsis seeds germination at 0.5 mM and 1.0 mM concentrations, respectively, while other compounds showed no obvious inhibitory effects.
Journal Article•
TL;DR: It was observed that the Asphodelus tenuifolius and Fumaria indica inhibited % germination and germination index of maize.
Abstract: The experiment was designed to determine the allelopathic effects of three different weeds viz., Onion weed (Asphodelus tenuifolius Cavase), pill-bearing spurge/Asthma plant (Euphorbia hirta Linn) and Fumitory (Fumaria indica Haussk H.N.) on the growth of maize. The weed powders toxicity and their inhibitory effects on germination and growth of maize crop were observed. It was demonstrated that different weed species responded differently to the maize. It was observed that the Asphodelus tenuifolius and Fumaria indica inhibited % germination and germination index of maize. The growth parameters of maize did not show consistent effects by these weeds. During the present study, allelopathic effects were not revealed and more experiments are suggested before making any conclusion about the allelopathic characteristic considering these
TL;DR: Parthenium composting with locally available plant materials is suggested as a means to reduce its allelopathic inhibitory effect and as a way of parthenium management by utilization.
Abstract: The present study was conducted to determine allelopathic effects of parthenium compost and to investigate whether ratio of parthenium composted with other plant materials have an influence on allelopathic potential of parthenium. Two emergence and growth experiments were conducted using lettuce as a model plant. Fresh parthenium reduced lettuce emergence percentage and rate and radicle and plumule lengths by 93, 95, 97 and 93%, respectively. Composted parthenium however reduced emergence percentage and rate and radicle and plumule lengths by 0, 33, 35 and 43%, respectively. Composting parthenium with other plant materials reduced allelopathic inhibition effects of parthenium on lettuce emergence rate and radicle and plumule lengths more than composting parthenium alone. Our results clearly showed that composting greatly reduced allelopathic effects of parthenium compared to fresh parthenium. Furthermore, composting parthenium with other plants resulted in lower inhibition of emergence rate and radicle and plumule lengths compared to composting parthenium alone. Hence, we suggest parthenium composting with locally available plant materials as a means to reduce its allelopathic inhibitory effect and as a way of parthenium management by utilization.
Key words: Allelopathy, compost, germination, invasive alien weed, Parthenium hysterophorus, seedling growth.
TL;DR: Both the acacia and bitou bush have the potential to chemically inhibit the establishment of indigenous plants, and it is proposed that both are dominant dominant of the invaded system.
Abstract: Chemical interference is increasingly suggested as a mechanism facilitating exotic plant invasion and plant community composition. In order to explore this further, we employed a comprehensive extract-bioassay technique that facilitated detection and demarcation of phytotoxicity, direct allelopathy and indirect allelopathy of bitou bush (Chrysanthemoides monilifera spp. rotundata) compared to an indigenous dominant of the invaded system, acacia (Acacia longifolia var. sophorae). Extracts of the leaves and roots of both species exhibited phytotoxic effects against five indigenous plant species. Evidence for allelopathy between co-evolved indigenous plants was detected between acacia and Isolepis nodosa. Allelopathy between bitou bush and four indigenous plant species was also detected. Therefore we propose that both the acacia and bitou bush have the potential to chemically inhibit the establishment of indigenous plants. Eventual dominance of bitou bush is predicted, however, based on more ubiquitous effects on seedling growth.
TL;DR: Three diffusive sampling strategies that employ polydimethylsiloxane (PDMS) sorbents are evaluated to map the spatial distribution and temporal dynamics of root-exuded thiophenes from the African marigold, Tagetes erecta to test hypotheses about the role of root exudates in plant-plant and other interactions.
Abstract: The difficulties of monitoring allelochemical concentrations in soil and their dynamics over time have been a major barrier to testing hypotheses of allelopathic effects. Here, we evaluate three diffusive sampling strategies that employ polydimethylsiloxane (PDMS) sorbents to map the spatial distribution and temporal dynamics of root-exuded thiophenes from the African marigold, Tagetes erecta. Solid phase root zone extraction (SPRE) probes constructed by inserting stainless steel wire into PDMS tubing were used to monitor thiophene concentrations at various depths beneath marigolds growing in PVC pipes. PDMS sheets were used to map the distribution of thiophenes beneath marigolds grown in thin glass boxes. Concentrations of the two major marigold thiophenes measured by these two methods were extremely variable in both space and time. Dissection and analysis of roots indicated that distribution of thiophenes in marigold roots also was quite variable. A third approach used 1 m lengths of PDMS microtubing placed in marigold soil for repeated sampling of soil without disturbance of the roots. The two ends of the tubing remained out of the soil so that solvent could be washed through the tubing to collect samples for HPLC analysis. Unlike the other two methods, initial experiments with this approach show more uniformity of response, and suggest that soil concentrations of marigold thiophenes are affected greatly even by minimal disturbance of the soil. Silicone tube microextraction gave a linear response for α-terthienyl when maintained in soils spiked with 0–10 ppm of this thiophene. This method, which is experimentally simple and uses inexpensive materials, should be broadly applicable to the measurement of non-polar root exudates, and thus provides a means to test hypotheses about the role of root exudates in plant-plant and other interactions.
Journal Article•
TL;DR: Combination of allelopathic crop water extracts with lower rate of herbicides may provide lower desired weed control levels there by reducing herbicide usage.
Abstract: Crop allelopathy can be manipulated for achieving sustainable weed management. Less inhibition of weeds is generally achieved through allelopathic interactions than the standard weed control limits. Combination of allelopathic crop water extracts with lower rate of herbicides may provide lower desired weed control levels there by reducing herbicide usage. Two field studies were conducted utilizing water extracts of allelopathic crops sorghum (Sorghum bicolor L.), sunflower (Helianthus annuus L.) and brassica (Brassica napus L.) with reduced glyphosate dosage for controlling purple nutsedge in cotton. In first experiment sorghum and brassica water extracts were tank mixed (at 15 & 18 L ha -1 ) in different combinations with reduced rate of glyphosate by 767 and 575 g a.e. ha -1 and sprayed as directed post emergence at 21 days after sowing (DAS). In second experiment sorghum and sunflower water extracts were mixed with glyphosate at same dose as in experiment 1. Purple nutsedge density and dry weight were suppressed by 78% to 95% and 83% to 95% respectively, when different crop water extracts were used in combination with reduced rate of glyphosate. Seed cotton yield was improved from 15-21% in sorgaab and brassica water extract combinations with reduced rates of glyphosate (67-75%). However, the yield improvement in the combination of sorgaab and sunflower water extracts was comparatively less (13-19%) with similar reduction in herbicides dose.
TL;DR: It is concluded that root exudates and residues of A. conyzoides suppress the growth of rice by releasing phenolic allelochemicals into the soil rhizosphere and not through alteration of soil nutrients, and allelopathy plays a significant role in root-mediated negative interference.
01 Jan 2009
TL;DR: In this article, a review discusses how such an allelochemical role of a phytotoxin can be proven and provides examples of some of the more studied phytochemicals that have been implicated in allelopathy.
Abstract: All plants produce compounds that are phytotoxic to another plant species at some concentration. In some cases, these compounds function, at least in part, in plant/plant interactions, where a phytotoxin donor plant adversely affects a target plant, resulting in an advantage for the donor plant. This review discusses how such an allelochemical role of a phytotoxin can be proven and provides examples of some of the more studied phytochemicals that have been implicated in allelopathy. These include artemisinin, cineoles, β-triketones, catechin, sorgoleone, juglone and related quinones, rice allelochemicals, benzoxazinoids, common phenolic acids, l-DOPA, and m-tyrosine. Mechanisms of avoiding autotoxicity in the donor species are also discussed.
TL;DR: It is suggested that allelochemicals can change soil microbial genetic diversity, biological activity and microbial metabolic activity, which alter soil microbial ecology and accordingly affect the growth of cucumber with accumulation in the soil of alleLochemicals.
TL;DR: Allelopathy may be a less frequent process in cyanobacteria at low cell-densities, as most studies have used high cyanobacterial cell densities, typical of bloom situations.
Abstract: Allelopathic interactions are thought to play an important role in phytoplankton ecology. Many cyanobacterial genera have been shown to produce compounds with allelopathic activity; however, most studies have used high cyanobacterial cell densities, typical of bloom situations. We investigated whether low cell densities of cyanobacteria exhibit allelopathic activity. Twenty-two cyanobacterial strains were cultured in laboratory conditions, and the effects of their exudates were tested on the microalgae Ankistrodesmus falcatus and Chlorella vulgaris. We found that the exudates from one strain of Cylindrospermopsis raciborskii caused an enhancement of A. falcatus growth, followed by a marked decrease in growth rates, and that exudates from one strain of Oscillatoria sp. strongly inhibited C. vulgaris, as confirmed by dose–response assays. After the removal of the stressors, the microalgae grew at normal rates. The responsible compounds showed low sensitivity to heat and proteinase treatments. However, the m...
Journal Article•
TL;DR: The data suggests that sorghum allelopathy can be exploited in different cropping practices to control weeds and inhibition of nitrification and application of its water extracts in fields controls the weeds and enhances the crops productivity.
Abstract: The promising allelopathic potential of sorghum ( Sorghum bicolor L. (Moench)) opens a fruitful area of research to exploit this phenomenon in weed control and regulation of nutrients cycle. The data suggests that sorghum allelopathy can be exploited in different cropping practices (cover crop, smother crop, companion crop, mixing crop and smother crop to control weeds and inhibition of nitrification) and application of its water extracts in fields controls the weeds and enhances the crops productivity. The herbicidal and allelopathic properties of sorgoleone, a compound isolated from root exudates of sorghum and other allelochemicals in sorghum deserve further work to identify the enzymes responsible for the biosynthesis of these compounds and the genes encoding them. Besides there is need to use genetic engineering to manipulate the identified genes in sorghum or in other crops to enhance their ability to suppress the weeds. This review addresses the research on the role of allelopathic potential in different cropping systems and the approaches developed in weeds management.
Journal Article•
TL;DR: Allelopathic influence of sunflower plant water extract against weeds and wheat sown after sorghum crop was studied under field conditions at Fodder Research Institute, Sargodha (Pakistan), during 2005-06 and increased the wheat yield significantly over control.
Abstract: Allelopathic influence of sunflower plant water extract (1:10 w/v) against weeds and wheat sown after sorghum crop was studied under field conditions at Fodder Research Institute, Sargodha (Pakistan), during 2005-06. Treatments applied were sunflower plant water extract at pre-emergence, at 25 DAS (days after sowing), pre-emergence + 25 DAS, 25+35 DAS, preemergence + 25 + 35 DAS and control. Wheat variety Inqlab-91 was sown on 13 th November, 2005. The inhibitory effects of pre-emergence application on germination of Phalaris minor were higher, whereas wheat remained unaffected at this stage of application. Application of water extract at pre-emergence + 25 DAS, 25 + 35 DAS and pre-emergence + 25 + 35 DAS suppressed the growth of Phalaris minor Retz., Chenopodium album L., Coronopus didymus L. and Avena fatua L. Inhibitory effects were species specific and increased with increasing the water extract application frequency. All the treatments except preemergence + 25 + 35 DAS increased the wheat yield significantly over control.
TL;DR: The findings serve to illustrate that the precise chemical forms, interactions and effects of catechin in the environment are highly variable and that further examination is warranted to increase the understanding of its role in invasion and allelopathy.
Abstract: Summary 1. Evaluating variation, or ‘conditionality’, in plant interactions is crucial to understanding their ecological importance and predicting where they might be at play. Much is known about conditionality for competition, facilitation and herbivory, but not for allelopathy, which likely contributes to the equivocal nature of reports on this topic. Centaurea maculosa (spotted knapweed) is an invasive species in North America, whose success has been attributed, at least in part, to the allelochemical root exudate (±)-catechin. 2. Understanding the ecological relevance of (±)-catechin necessitates determining how it interacts with various soil components. We found that some metals caused rapid declines in measurable (±)-catechin, while calcium impeded its auto-oxidation, maintaining concentrations higher than for (±)-catechin alone. Certain (±)-catechin–metal complexes were more phytotoxic than (±)-catechin alone, while others showed lower toxicity. 3. The variable phytotoxicity of these complexes suggests that (±)-catechin effects are enhanced, mitigated or otherwise affected by complexation with different metals and perhaps other soil components. 4. Synthesis. These findings serve to illustrate that the precise chemical forms, interactions and effects of catechin in the environment are highly variable and that further examination is warranted to increase our understanding of its role in invasion and allelopathy. The conditional effects observed for catechin detection and phytotoxicity likely extend to related allelopathic compounds, other root exudates and potentially other systems involving chemically complex and spatially heterogeneous environments.
Journal Article•
TL;DR: Juglone index of fourteen invasive woody plant species in Hungary was determined by the method of Szabo (1997), comparing the effects of juglone and substa nce extracted of plant species with unknown allelopathic potential on the germination rate, shoot length and rooth length of white mustard used as receiver species.
Abstract: Allelopathy may play an important role in the invas ion success of adventive plant species. The aim of this study was to determine the allelopa thic potential of invasive woody plant species occu rring in Hungary. Juglone index of fourteen invasive woody plant species in Hungary was determined by the method of Szabo (1997), comparing the effects of juglone and substa nce extracted of plant species with unknown allelopathic potential on the germination r ate, shoot length and rooth length of white mustard (Sinapis alba L.) used as receiver species. Results have proven a more or less expressed allelopathic potential in case of all species. The juglone index at higher concentration extracts (5 g dry plant material extracted with 100 ml distilled water) of almost ev ery studied species approaches to 1 or is above 1, this means the effect of the extracts is similar to jugl one or surpasses it. In terms of juglone index, the allelopathic potential of false indigo ( Amorpha fruticosa L.), tree-of-heaven ( Ailanthus altissima (Mill.) Swingle) and hackberry ( Celtis occidentalis L.) were the highest. Besides these species the tr eatment with the extracts of black walnut ( Juglans nigra L.), black cherry ( Prunus serotina Ehrh.) and green ash (Fraxinus pennsylvanica MARSH . var. subintegerrima (Vahl) Fern .) reduced extremely significantly the germination rate, shoot and root length, compared t o the control. species / allelopathy / juglone index / germination inhibition / growth inhibition