Showing papers on "Allelopathy published in 2010"
TL;DR: The main purpose of this review is to highlight the allelopacthic potential of phenolic compounds to provide methods to solve various ecology problems, especially in regard to the sustainable development of agriculture, forestry, nature resources and environment conservation.
Abstract: Phenolic compounds arise from the shikimic and acetic acid (polyketide) metabolic pathways in plants. They are but one category of the many secondary metabolites implicated in plant allelopathy. Phenolic allelochemicals have been observed in both natural and managed ecosystems, where they cause a number of ecological and economic problems, such as declines in crop yield due to soil sickness, regeneration failure of natural forests, and replanting problems in orchards. Phenolic allelochemical structures and modes of action are diverse and may offer potential lead compounds for the development of future herbicides or pesticides. This article reviews allelopathic effects, analysis methods, and allelopathic mechanisms underlying the activity of plant phenolic compounds. Additionally, the currently debated topic in plant allelopathy of whether catechin and 8-hydroxyquinoline play an important role in Centaurea maculata and Centaurea diffusa invasion success is discussed. Overall, the main purpose of this review is to highlight the allelopacthic potential of phenolic compounds to provide us with methods to solve various ecology problems, especially in regard to the sustainable development of agriculture, forestry, nature resources and environment conservation.
579 citations
TL;DR: The literature indicates that invasive species can alter the biogeochemistry of ecosystems, that secondary metabolites released by invasive species may play important roles in soil chemistry as well as plant-plant and plant-microbe interactions, and that the herbicides used to control invasive speciesCan impact plant chemistry and ecosystems in ways that have yet to be fully explored.
Abstract: Invasive plants have a multitude of impacts on plant communities through their direct and indirect effects on soil chemistry and ecosystem function. For example, plants modify the soil environment through root exudates that affect soil structure, and mobilize and/or chelate nutrients. The long-term impact of litter and root exudates can modify soil nutrient pools, and there is evidence that invasive plant species may alter nutrient cycles differently from native species. The effects of plants on ecosystem biogeochemistry may be caused by differences in leaf tissue nutrient stoichiometry or secondary metabolites, although evidence for the importance of allelochemicals in driving these processes is lacking. Some invasive species may gain a competitive advantage through the release of compounds or combinations of compounds that are unique to the invaded community—the “novel weapons hypothesis.” Invasive plants also can exert profound impact on plant communities indirectly through the herbicides used to control them. Glyphosate, the most widely used herbicide in the world, often is used to help control invasive weeds, and generally is considered to have minimal environmental impacts. Most studies show little to no effect of glyphosate and other herbicides on soil microbial communities. However, herbicide applications can reduce or promote rhizobium nodulation and mycorrhiza formation. Herbicide drift can affect the growth of non-target plants, and glyphosate and other herbicides can impact significantly the secondary chemistry of plants at sublethal doses. In summary, the literature indicates that invasive species can alter the biogeochemistry of ecosystems, that secondary metabolites released by invasive species may play important roles in soil chemistry as well as plant-plant and plant-microbe interactions, and that the herbicides used to control invasive species can impact plant chemistry and ecosystems in ways that have yet to be fully explored.
288 citations
TL;DR: The objective of this article is to review the possibilities for using allelopathy to improve overall potentiality of weeds and crops in natural weed management and to discard use of synthetic herbicides completely.
Abstract: To meet the food requirement of the ever-growing population of the world the introduction of pesticides in agriculture was a welcome move to control obnoxious weeds below the threshold limit and thereby reduce the yield loss. But continuous use of synthetic herbicides in heavy doses creates environment pollution and increases the number of herbicide resistant weeds. Hence, researches should be done to find out some natural way for minimizing the dependency on synthetic herbicides. The objective of this article is to review the possibilities for using allelopathy to improve overall potentiality of weeds and crops in natural weed management. Allelopathy is the favorable or adverse effect of one plant on another due to direct or indirect release of chemicals from live or dead plants (including microorganisms). Although we cannot discard use of synthetic herbicides completely at the present situation but their use can be reduced up to a certain extent by utilizing allelopathic potentiality as an alternative weed management strategy for crop production as well as environmental benefits.
226 citations
TL;DR: It was concluded that the rice root exudates had anti-fungal properties while that from watermelon promoted pathogen growth, which provided a scientific basis for practicing watermelon/aerobic rice intercropping to control Fusarium wilt in watermelon.
Abstract: Root exudates have a key role in communication between plants and microbes in the rhizosphere. Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum (Fusarium oxysporum), drastically reduces watermelon yields in continuous cultivation systems, but it can be significantly alleviated using watermelon/aerobic rice intercropping system as shown by the research carried out in this laboratory. It is important to evaluate the interaction between root exudates from the two crops and the pathogen and thus to clarify the mechanism of disease suppressiveness in the intercropping system. The effects of phenolic acids, sugars and free amino acids in root exudates from watermelon (REW) and rice (RER) on the growth of Fusarium oxysporum were studied. The results obtained are listed as follows: (1) REW significantly increased spore germination and sporulation, whereas RER had inhibitory effects on those two parameters. (2) HPLC analysis showed that salicylic acid, p-hydroxybenzoic acid and phthalic acid were identified in exudates from both plants, but p-coumaric acid was only detected in rice and ferulic acid only in watermelon. Moreover, of the total rice exudates a high proportion (37.9 %) of p-coumaric acid was detected and the total amount of phenolic acids was 1.4-fold as high as that in watermelon. (3) Considerable differences in the components and contents of both sugars and amino acids were found between REW and RER exudates. (4) Exogenously applied alanine (Ala) increased spore germination and sporulation. In contrast, addition of exogenous p-coumaric acid reduced spore germination and sporulation, relative to controls. It was concluded that the rice root exudates had anti-fungal properties while that from watermelon promoted pathogen growth. This discovery provided a scientific basis for practicing watermelon/aerobic rice intercropping to control Fusarium wilt in watermelon.
178 citations
TL;DR: It is observed that maximal allelopathic activity is highest in early growth stages of the cyanobacterium, and this provided sufficient material for isolation and chemical characterization of active compounds that inhibited the growth of C. vulgaris.
Abstract: The ability of cyanobacteria to produce complex secondary metabolites with potent biological activities has gathered considerable attention due to their potential therapeutic and agrochemical applications. However, the precise physiological or ecological roles played by a majority of these metabolites have remained elusive. Several studies have shown that cyanobacteria are able to interfere with other organisms in their communities through the release of compounds into the surrounding medium, a phenomenon usually referred to as allelopathy. Exudates from the freshwater cyanobacterium Oscillatoria sp. had previously been shown to inhibit the green microalga Chlorella vulgaris. In this study, we observed that maximal allelopathic activity is highest in early growth stages of the cyanobacterium, and this provided sufficient material for isolation and chemical characterization of active compounds that inhibited the growth of C. vulgaris. Using a bioassay-guided approach, we isolated and structurally characterized these metabolites as cyclic peptides containing several unusually modified amino acids that are found both in the cells and in the spent media of Oscillatoria sp. cultures. Strikingly, only the mixture of the two most abundant metabolites in the cells was active toward C. vulgaris. Synergism was also observed in a lung cancer cell cytotoxicity assay. The binary mixture inhibited other phytoplanktonic organisms, supporting a natural function of this synergistic mixture of metabolites as allelochemicals.
113 citations
TL;DR: Most species, particularly invasive shrubs, did not exhibit sufficient allelopathic potential to suggest allelopathy would occur in the field and warrant additional study in theField.
Abstract: Invasive plant species are often more successful within introduced areas when compared to their natural ranges. Allelopathy has been suggested as a potential mechanism for this success because invasive plants frequently establish monocultures and may produce allelochemicals evolutionarily novel to the recipient community. However, species are typically tested in isolation making the relative strength of allelopathy difficult to assess. We conducted laboratory bioassays for 10 co-occurring non-native species to determine the relative strength of their allelopathic potential. These species represented a suite of successful invaders within a young forest and were from a variety of plant life forms: trees, lianas, shrubs, and herbs. We determined the germination responses of a target species to a gradient of leaf extract concentrations to assess relative allelopathic potential. The relative strength of germination inhibition was quantified by the slope (β) of the germination response to plant extract...
108 citations
TL;DR: Leaves of Parthenium hysterophorus may be a source of natural weedicide against Ageratina adenophora which will help to control invasive plants and wild Asteraceae.
Abstract: Allelopathic effects of aqueous extract of leaves of Parthenium hysterophorus were studied on seed germination and seedling growth of three cereal crops ( Oryza sativa L ., Zea mays L . and Triticum aestivum L.), three cultivated crucifers ( Raphanus sativus L. , Brassica campestris L. and Brassica oleracea L.) and two wild species of family Asteraceae ( Artemisia dubia Wall ex. Besser and Ageratina adenophora (Spreng) King and HE Robins). Seed germination of all crucifer species was completely inhibited at >2% leaf extract of Parthenium hysterophorus but in other species, except maize, complete failure of seed germination was recorded only at >6% in Triticum aestivum and Ageratina adenophora; at 10% in Oryza sativa and Artemisia dubia . Seed germination of Zea mays was not completely inhibited but it was low at high concentration of the extract. The extract had strong inhibitory effect to root elongation of seedling in cereals and to shoot elongation in crucifers and wild Asteraceae. Leaves of Parthenium hysterophorus may be a source of natural weedicide against Ageratina adenophora which will help to control invasive plants. Key words: Alien invasive; Asteraceae; Cereal crops; Crucifers; Seedling biomass; Weedicide. DOI: 10.3126/sw.v5i5.2653 Scientific World , Vol. 5, No. 5, July 2007 33-39
104 citations
TL;DR: Using three analytical approaches to quantifying allelopathy, this work consistently found allelopathic inhibition only in sterilized soils, suggesting that certain microbial taxa inhibit the process, possibly by degrading the allelochemicals.
Abstract: Allelopathy has been increasingly invoked as a mechanism facilitating exotic plant invasions However, studies even on the same target species often yield varying results concerning the strength and importance of allelopathic inhibition, suggesting that the process may depend on the specific environmental context Here I studied how the allelopathic inhibition of sycamore (Platanus occidentalis) seedlings by garlic mustard (Alliaria petiolata) depended on the presence of a soil microbial community Using three analytical approaches to quantifying allelopathy, I consistently found allelopathic inhibition only in sterilized soils, suggesting that certain microbial taxa inhibit the process, possibly by degrading the allelochemicals Determining the environmental contexts that reduce or eliminate allelopathic inhibition could lead to a greater understanding of the spatial variation in invasion success and potentially lead to new avenues for management
96 citations
TL;DR: The rapid and strong allelopathic effects exhibited by C. polykrikoides suggest allelopathy may facilitate blooms by eliminating com- peting species and these results are consistent with bioassays of fish and shellfish larvae with C.polykriKOides, suggesting that its toxicity to fish andShellfish larvae and its allelopathies are caused by the same agents.
Abstract: The toxic dinoflagellate Cochlodinium polykrikoides forms harmful algal blooms in coastal ecosystems around the world, to the great detriment of fisheries. Here we describe the allelo- pathic effects of C. polykrikoides blooms and strains isolated from east coast estuaries of the United States on natural communities and cultured phytoplankton. The allelopathic effects of C. poly- krikoides cultures and blooms on the target microalgal cells included loss of motility, distortion of cell morphology, and 60 to 100% cell mortality within minutes to 24 h. Allelopathy by C. polykrikoides on target microalgae was dependent on the relative and absolute cell abundance of each species as well as exposure time. The ability of C. polykrikoides cultures to kill target algae connected through a 5 µm mesh nylon membrane indicated that the allelopathic agents were extracellular and that direct cellular contact with target cells was not required for C. polykrikoides to exhibit allelopathy. Freez- ing, heating, sonication, and filtration of C. polykrikoides cells led to the complete loss of their allelo- pathic effect, suggesting that the allelopathic agents were short-lived and dependent on cell viabil- ity. Additions of the reactive oxygen species (ROS)-scavenging enzymes peroxidase and catalase into C. polykrikoides cultures eliminated or lessened their allelopathic effects, suggesting ROS-like chemical(s) were responsible for the allelopathy. These results are consistent with bioassays of fish and shellfish larvae with C. polykrikoides, suggesting that its toxicity to fish and shellfish larvae and its allelopathic effects on algae are caused by the same agents. The rapid and strong allelopathic effects exhibited by C. polykrikoides suggest allelopathy may facilitate blooms by eliminating com- peting species.
87 citations
TL;DR: This work aims to isolate and characterize microbes in the soils containing high contents of phenolics and to dissolve the allelopathic inhibition of plants through microbial degradation.
Abstract: Aims: To isolate and characterize microbes in the soils containing high contents of phenolics and to dissolve the allelopathic inhibition of plants through microbial degradation.
Methods and Results: Four microbes were isolated from plant soils using a screening medium containing p-coumaric acid as sole carbon source. The isolates were identified by biochemical analysis and sequences of their 16S or 18S rDNA, and designated as Pseudomonas putida 4CD1 from rice (Oryza sativa) soil, Ps. putida 4CD3 from pine (Pinus massoniana) soil, Pseudomonas nitroreducens 4CD2 and Rhodotorula glutinis 4CD4 from bamboo (Bambusa chungii) soil. All isolates degraded 1 g l−1 of p-coumaric acid by 70–93% in inorganic and by 99% in Luria-Bertani solutions within 48 h. They also effectively degraded ferulic acid, p-hydroxybenzoic acid and p-hydroxybenzaldehyde. The microbes can degrade p-coumaric acid and reverse its inhibition on seed germination and seedling growth in culture solutions and soils. Low pHs inhibited the growth and phenolic degradation of the three bacteria. High temperature inhibited the R. glutinis. Co2+ completely inhibited the three bacteria, but not the R. glutinis. Cu2+, Al3+, Zn2+, Fe3+, Mn2+, Mg2+ and Ca2+ had varying degrees of inhibition for each of the bacteria.
Conclusions: Phenolics in plant culture solutions and soils can be decomposed through application of soil microbes in laboratory or controlled conditions. However, modification of growth conditions is more important for acidic and ions-contaminated media.
Significance and Impact of the Study: The four microbes were first isolated and characterized from the soils of bamboo, rice or pine. This study provides some evidence and methods for microbial control of phenolic allelochemicals.
83 citations
TL;DR: Granéli, Edna and Paulo S. Salomon, 2010.
Abstract: Graneli, Edna and Paulo S. Salomon, 2010. Factors Influencing Allelopathy and Toxicity in Prymnesium parvum. Journal of the American Water Resources Association (JAWRA) 46(1):108-120.
Abstract: Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allelopathy. Inhibiting or killing competitors enable these species to monopolize limiting resources, such as nitrogen and phosphorus. Prymnesium parvum is known to produce such allelopathic compounds, substances that seem identical to the ichthyotoxins identified from this species. Biotic and abiotic environmental factors influence not only growth rates but also toxin/allelopathic compounds production by P. parvum cells. Toxin production, as well as allelopathy, including grazer deterrence, increases dramatically in light, temperature, or nutrient stressed P. parvum cells. Correspondingly, toxicity and allelopathy may decrease, or cease completely, if cells are grown with high amounts of N and P in balanced proportions. However, even under nutrient (N and P) sufficient conditions, P. parvum is able to produce toxins/allelopathic compounds, with negative effects on other phytoplankton species or grazers, if cells densities of P. parvum are high relative to other species. This negative effect might shift the plankton community to more toxin resistant species. Filtrates from nutrient-deficient P. parvum cultures have almost the same strong negative effect on grazers and other phytoplankton species as when Prymnesium cells are grown together with the target organisms. Eutrophication, the increased input of N and P to aquatic ecosystems, besides increasing nutrient concentrations, is usually provoking unbalanced N:P condition for the optimal growth of phytoplankton, deviating from the Redfield ratio, i.e., the phytoplankton cellular nitrogen to phosphorus ratio, N:P = 16:1 (by atoms) or 7.2:1 (by weight). Eutrophication thus both enhances P. parvum growth and increases production of toxins and allelopathic compounds. Supplying N-deficient or P-deficient P. parvum cells with the deficient nutrient reduces toxicity to less than half within 24 h after additions. As P. parvum is mixotrophic, uptake of dissolved or particulate organic N (DON or PON) can also reduce toxicity and allelopathy in the same manner as addition of inorganic N to N-starved cells. In conclusion, P. parvum, by increasing its toxicity and allelopathic ability under poor environmental conditions, outcompetes the co-occurring phytoplankton species.
TL;DR: In this paper, the exploitation of crop allelopathy against weeds may be useful to reduce issues related to the use of herbicides, such as environmental pollution, use of unsafe products and human health concerns.
Abstract: The exploitation of crop allelopathy against weeds may be useful to reduce issues related to the use of herbicides. Several crops, such as alfalfa, barley, black mustard, buckwheat, rice, sorghum, sunflower and wheat, demonstrate strong weed suppression ability, either by exuding allelochemical compounds from living plant parts or from decomposing residues. As well as the positive effect on weed reduction, the introduction in agronomic rotations of allelopathic crops, their use as a mulch to smother crops or as a green manure may also be helpful in reduction of other agricultural problems, such as environmental pollution, use of unsafe products and human health concerns, through a reduction in chemical inputs. Knowledge of allelopathic properties of crops may also be advantageous in mitigation of soil sickness. Moreover, information on weed allelopathy may be profitable in preventing serious crop damage if the weed biomass is buried in the soil, and a crop susceptible to allellochemicals is planned for th...
Journal Article•
TL;DR: The study of allelopathy appears to have a bright future, especially if the authors can translate their research into technologies that will reduce their reliance on synthetic herbicides, and knowledge gaps are being filled at an ever increasing pace.
Abstract: The study of allelopathy as a discipline has a long and at times controversial history. Since Hans Molisch coined the term before World War II, allelopathy research has grown from a trickle of papers before 1970 to a burgeoning subdiscipline of chemical ecology represented by hundreds of papers each year. Yet, allelopathy research still suffers from a reputation for papers of poor scientific quality that equate the presence of a phytotoxic phytochemical as proof of an allelochemical function without regard for proving that the compound is bioavailable in soil at sufficient concentrations to affect vegetation either directly or indirectly through effects on soil microbes. Synergism has often been invoked without proof to explain why effects of crude extracts are sometimes greater than even the additive effects of phytotoxins known to be in the extract. Much of this work may be correct, but to be widely accepted more rigorous proof is needed. Much of this literature also makes the assumption that allelochemicals must be highly water soluble, when there are good scientific reasons to hypothesize that the most effective allelochemicals would have very limited water solubility. Very little is known about the mode of action of and mechanisms of resistance to putative allelochemicals. Nevertheless, the quality and quantity of papers on allelopathy has increased steadily over the past several decades and knowledge gaps are being filled at an ever increasing pace. There can be little doubt that allelopathy plays an important role in plant/plant interactions in nature and in agriculture. Translating this growing knowledge to technology to manage weeds in agriculture has been slow. There is only one good case of discovery of an allelochemical (leptospermone) leading to the development of a major class of herbicides (triketones). There are examples of allelopathic cover crops being used for weed management in other crops, as well as other cultural methods to employ allelopathy. However to my knowledge, there are still no cultivars of crops being sold with allelopathic properties as a selling point. Enhancement or impartation of allelopathy in crops through the use of transgenes could eventually be used to produce such a cultivar. Some of the most high profile recent examples of research in our discipline will be discussed. The study of allelopathy appears to have a bright future, especially if we can translate our research into technologies that will reduce our reliance on synthetic herbicides.
TL;DR: Plants revealing strong allelopathic potential can be utilized to derive natural herbicides for weed control, and sorghum however exhibited least suppressive or in some cases stimulatory effects on canary grass.
Abstract: Environmental contamination, herbicide resistance development among weeds and health concerns due to over and misuse of synthetic herbicides has led the researchers to focus on alternative weed management strategies. Allelochemicals extracted from various plant species can act as natural weed inhibitors. In this study, allelopathic extracts from four plant species sorghum (Sorghum bicolor (L.) Moench), mulberry (Morus alba L.), barnyard grass (Echinochloa crusgalli (L.) Beauv.), winter cherry (Withania somnifera (L.)) were tested for their potential to inhibit the most problematic wheat (Triticum aestivum L.) weeds wild oat (Avena fatua L.) and canary grass (Phalaris minor Ritz.). Data regarding time to start germination, time to 50% germination, mean germination time, final germination percentage, germination energy, root and shoot length, number of roots, number of leaves, and seedling fresh and dry weight was recorded for both the weeds, which showed that mulberry was the most inhibitory plant species while sorghum showed least allelopathic suppression against wild oat. Mulberry extracts resulted in a complete inhibition of the wild oat germination. The allelopathic potential for different plants against wild oat was in the order: mulberry > winter cherry > barnyard grass > sorghum. Mulberry, barnyard grass and winter cherry extracts resulted in a complete inhibition of canary grass. Sorghum however exhibited least suppressive or in some cases stimulatory effects on canary grass. Plants revealing strong allelopathic potential can be utilized to derive natural herbicides for weed control.
TL;DR: The results showed that aqueous extract of E. grandis root suppressed the germination and early seedling growth of the target plants and indicated that the soil might neutralize or dilute allelopathic agents with the increase of plantation age.
Abstract: Allelopathy of the eucalypt has been considered as an important mechanism for the biodiversity reduction in the eucalypt plantation. To understand the allelopathic potential of the eucalypt (Eucalyptus grandis) roots and rhizosphere soil along a chronosequence (2, 4, 6, 8, 10 years), the germination and growth characteristics of three plant species (Raphanus sativus, Phaseolus aureus, and Lolium perenne) growing nearby or beneath the eucalypt plantations were measured. The results showed that aqueous extract of E. grandis root suppressed the germination and early seedling growth of the target plants. The younger E. grandis exhibited a comparatively stronger allelopathic potential. The highest dose root extracts from 4 years old E. grandis showed the strongest inhibitory effects on the germination rates of the target species, the inhibitory rates were about 48, 51.2, and 56.56% for R. sativus, P. aureus, and L. perenne, respectively. However, present biotests of rhizosphere soils from 6, 8, and 10-year-old plantations exhibited a remarkable stimulative effect on L. perenne, which indicated that the soil might neutralize or dilute allelopathic agents with the increase of plantation age. In addition, according to GC–MS analysis, more allelopathic potential compounds were found in the rhizosphere soil and roots of younger E. grandis plantation. Moreover, more allelochemicals were obtained from soil than from roots. The allelopathic compounds in roots and rhizosphere soil may play important roles in allelopathy of E. grandis plantation. More attention should be paid to the younger E. grandis plantations for the relative higher allelopathic effects.
TL;DR: Both essential oils showed a dose-dependent allelopathic activity on wheat germination and radicle elongation with leaf oil being the more phytotoxic with the major constituents being limonene and β-phellendrene.
Abstract: Gas chromatography-flame ionisation detection (GC-FID) and gas chromatography–mass spectrometry (GC–MS) analyses of the essential oils of leaves and fruits of the ornamental Shinus molle L. were reported and their allelopathic effect on wheat (Triticum aestivum L.) was evaluated. Qualitative and quantitative differences between fruit and leaf oils were observed. Both oils were rich in monoterpene hydrocarbons and the major constituents were limonene and β-phellendrene (35.9–65.4%), α-phellendrene (24.3–20.1%), myrcene (12.8–7.7%) and α-pinene (5.9–1.7%) for fruits and leaves, respectively. Both essential oils showed a dose-dependent allelopathic activity on wheat germination and radicle elongation with leaf oil being the more phytotoxic.
Journal Article•
TL;DR: It was observed that an endemic species Seriphidium kurramense, Andrachne cordifolia and Rhazya stricta were the stronger phytotoxic plants as compared to the other test species.
Abstract: Allelopathic screening of 81 medicinal plant species, collected from North West Frontier Province (NWFP) Pakistan, was carried out to identify significantly higher allelopathic species for future phytochemical analyses. For this purpose, sandwich method was used to test allelopathic potentials of leaf leachates of these plant species against lettuce seeds (Lactuca sativa L.). Two different concentrations of 10 mg and 50 mg of leaf leachates were used in the study. The radicle and hypocotyl growths were measured and compared with control treatments. It was observed that an endemic species Seriphidium kurramense, Andrachne cordifolia and Rhazya stricta were the stronger phytotoxic plants as compared to the other test species. Based on the current screening, three potential medicinal plants are recommended for future bioassay guided isolation of allelochemicals and for genetic diversity studies. It would also be interesting to see correlation between genetic markers and isolated allelochemicals.
TL;DR: It is suggested that the reduced biomass of weeds in plots planted with the highly allelopathic wheat lines is related to differences in allelopathy activity and not differences in plant growth.
Abstract: Bertholdsson N-O (2010). Breeding spring wheat for improved allelopathic potential. Weed Research50, 49–57.
Summary
It is becoming apparent that allelopathy plays a significant role in the competitive ability of cereals against weeds; barley, wheat and rice cultivars with high allelopathic activity have been identified. However, direct breeding efforts to improve allelopathy have to date only been reported in rice. In this study, a breeding programme in spring wheat (Triticum aestivum) was evaluated to determine the efficiency of selection of allelopathy and the ability of breeding lines to suppress weeds in the field. The material used originated from a cross between a Swedish cultivar with low allelopathic activity and a Tunisian cultivar with high allelopathic activity. Allelopathic activity was measured as growth inhibition of perennial ryegrass (Lolium perenne) roots when grown together with the wheat cultivars on agar. For screening of F2 populations, a single plant bioassay was used for the first time. In the F6 and F7 generations, three breeding lines with an average improved allelopathy of 20% and one line with an unimproved allelopathy activity, but with the same phenotype as the high allelopathic lines, were tested together with the low allelopathic Swedish parent. The main result from the field study was a 19% average reduction of weed biomass for the high allelopathic lines, but no significant reduction of the low allelopathic breeding line. Early shoot length and early crop biomass (stages 37–39, Zadoks scale) and straw length of the high allelopathic lines were not significantly different from the Swedish parent. A negative effect was that grain yield was reduced by 9% in the high allelopathic lines. It is suggested that the reduced biomass of weeds in plots planted with the highly allelopathic wheat lines is related to differences in allelopathic activity and not differences in plant growth.
TL;DR: In this paper, the authors investigated the allelopathy effects of Croton bonplandianum weed on seed germination and seedling growth of crop plants (Triticum aestivum, Brassica oleracea), and weed plants (Melilotus alba, Medicago hispida, Vicia sativa) under laboratory conditions.
Abstract: The present study was conducted to investigate the allelopathic effects of Croton bonplandianum weed on seed germination and seedling growth of crop plants (Triticum aestivum L., Brassica oleracea var. botrytis L. and Brassica rapa L.) and weed plants (Melilotus alba Medik., Vicia sativa L. and Medicago hispida Gaertn). Root, stem and leaf aqueous extracts of Croton at 0.5, 1.0, 2.0 and 4.0% concentrations were applied to determine their effect on seed germination and seedling growth of test plants under laboratory conditions. The aqueous extracts from root, stem and leaf had no effect on seed germination of test plants. The extracts from stem had a stimulatory effect on the shoot length at all concentration levels, as against an inhibitory effect of leaf extracts. Stem extracts at low concentration generally promoted root length but aqueous extracts from leaf and root inhibited root length and dry weight. Root length, shoot length of weed species decreased progressively when plants were exposed to increasing concentration (0.5, 1, 2 and 4%). The pH, osmotic potential and total phenolic contents, the osmotic potential and phenolic content increased with increasing concentrations of aqueous extracts of different parts of C. bonplandianum while pH does not have any major change.
Key words: Allelopathy, aqueous leaf extract, aqueous stem extract, aqueous root extract, Melilotus alba, Medicago hispida, Vicia sativa, Croton bonplandianum.
TL;DR: These findings provide support for the idea that Amur honeysuckle (Lonicera maackii), a problematic invasive shrub, has allelopathic activity, but further work is needed to understand how broad the impact may be across the wide variety of species that are found in its invasion range and substantiate that the allelopathy effect has relevance in field environments.
TL;DR: Allelopathy plays an major role in agricultural management such as weed control, crop protection, and crop re-establishment and the incorporation of allelopathic substances into agricultural management may reduce the use of pesticides and lessen environmental deterioration.
Abstract: Allelopathy plays an major role in agricultural management such as weed control, crop protection, and crop re-establishment. Compositae plants have potent allelopathic activity, and the activity is confirmed through (a) bioassays with aqueous or various solvent extracts and residues, (b) fractionation, identification, and quantification of causative allelochemicals, and (c) mechanism studies on the allelochemicals. Most assessments of allelopathy involve bioassays of plant or soil extracts, leachates, fractions, and residues based on seed germination and seedling growth in laboratory and greenhouse experiments. Plant growth may be stimulated below the allelopathic threshold, but severe growth reductions may be observed above the threshold concentration depending upon the sensitivity of the receiving species. Generally germination is less sensitive than is seedling growth, especially root growth. Some approaches showed that field soil collected under donor plants significantly reduced or somewhat promoted growth of the test plants. Petri-dish bioassays with methanol extracts or fractions and causative phenolic allelochemicals showed significant phytotoxic activities in concentration-dependent manner. Delayed seed germination and slow root growth due to the extracts could be confounded with osmotic effects on rate of imbibition, delayed initiation of germination, and especially cell elongation; the main factor that affects root growth before and after the tip penetrates the seed coat. Light and electron microscopic approaches extract evaluation at the ultrastructural level have been precisely investigated. Many Compositae plants have allelopathic potentials, and the activities and types and amount of causative compounds differ depending on the plant species. The incorporation of allelopathic substances into agricultural management may reduce the use of pesticides and lessen environmental deterioration.
TL;DR: It was found that: water extracts from fresh and dry biomass of A. retroflexus, Ch.
Abstract: SUMMARY During the 2006-2007 period, the allelopathic effect of cold water extracts from Amaranthus retroflexus L., Chenopodium album L., Erigeron canadensis L. and Solanum nigrum L. on seed germination and initial development of Glycine max L., Pisum sativum L. and Vicia sativa L. was studied under laboratory conditions in the Institute of Forage Crops, Pleven. It was found that: water extracts from fresh and dry biomass of A. retroflexus, Ch. album, E. canadensis and S. nigrum had an inhibitory effect on seed germination of G. max, P. sativum and V. sativa, the inhibition rate for the extracts from fresh biomass varying from 28.8 to 81.5% and for the extracts from dry weed biomass it was from 26.8 tо 89.2%; The values of LC50 varied from 13.5 tо 72.2 g l -1 for the extracts from fresh biomass and from 7.0 tо 84.1 g l -1 for the extracts from dry weed biomass and they could be conditionally grouped in the following ascending order: A. retroflexus < S. nigrum < E. canadensis
TL;DR: Kudzu leaves and roots contain higher amounts of total phenolics and soluble phenolics than stems and seeds, consistent with the results of the germination bioassays, and a reduction of water imbibition might be one of the mechanisms of germination retardation.
Abstract: We explored the allelopathic potential of kudzu as a function of its phenolics. Aqueous and methanol extracts of different kudzu organs (leaf, stem, root, and seed) were assayed for allelopathy with the use of lettuce and radish seeds. Both leaf and root extracts significantly inhibited all of the measured germination indices (total germination, speed of germination, and coefficient of the rate of germination) (all P < 0.01). When treated with leaf extract, the total germination of both species was ∼ 20% less than the control. Furthermore, the leaf extract significantly reduced the speed of germination to 38 and 53% that of the lettuce and radish controls, respectively. Lettuce and radish seeds soaked in leaf and root extracts for 24 h imbibed less water (∼ 30% for both species) than those soaked in distilled water (control), suggesting that a reduction of water imbibition might be one of the mechanisms of germination retardation. Stem and seed extracts affected neither the water uptake nor the g...
TL;DR: It is shown that AMF can actually ameliorate allelopathic effects of an invasive plant, and suggest that previously observed allelopathy effects of A. petiolata may be due to direct inhibition of plant and fungal growth before symbiosis formation.
Abstract: The allelopathic potential of the Eurasian invasive plant Alliaria petiolata has been well documented, with the bulk of the effects believed to be mediated by arbuscular mycorrhizal fungi (AMF). We exposed the herbaceous annual Impatiens pallida, which is native to North America, to fractionated A. petiolata extracts at four developmental stages (germination, presymbiosis growth, symbiosis formation, and symbiosis growth) by using exposure levels expected to be similar to field levels. Surprisingly, we found strong direct effects on I. pallida germination and growth, but no indirect effects on I. pallida growth mediated by AMF. We also observed strong synergistic effects with a complete A. petiolata extract that inhibited I. pallida germination and presymbiosis root growth more than either a glucosinolate or flavonoid enriched fraction alone. In fact, the flavonoid enriched fraction tended to stimulate germination and presymbiosis root growth. In contrast to these strong direct effects, I. pallida plant growth during both the symbiosis formation and symbiosis growth phases was unaffected by A. petiolata extracts. We also found no inhibition of AMF colonization of roots or soils by A. petiolata extracts. We show that AMF can actually ameliorate allelopathic effects of an invasive plant, and suggest that previously observed allelopathic effects of A. petiolata may be due to direct inhibition of plant and fungal growth before symbiosis formation.
Journal Article•
TL;DR: The aqueous leaf leachate of E. hierosolymitana was found to inhibit significantly the growth of wheat seedlings and allelochemicals caused significant reduction in decreased root and shoot length, fresh, dry weights and decreased the amount of total chlorophyll and protein contents.
Abstract: 2 Abstract: This study was conducted to investigate the allelopathic potential effect of Euphorbia hierosolymitana in wheat (Triticum durum local var. Hourani 27), in both laboratory and glasshouse. Since E. hierosolymitana is a common weed in filed crops and orchards in Jordan. The effects aqueous leachate of E. hierosolymitana on germination, seedling growth, total chlorophyll and protein contents of wheat were examined. Higher c oncentration of aqueous leachate of E. hierosolymitana reduced the germination rate. On the other hand, the radicle and coleoptile length of the germinated seeds of wheat were significantly inhibited by the leachate. Also, the aqueous leaf leachate of E. hierosolymitana was found to inhibit significantly the growth of wheat seedlings. Allelochemicals caused significant reduction in decreased root and shoot length, fresh, dry weights and decreased the amount of total chlorophyll and protein contents.
Journal Article•
TL;DR: The allelopathic effects of extracts of leaf litter and live roots of three Eucalyptus species and their effects on the following crops were determined were inhibitory or stimulatory to test species.
Abstract: The allelopathic effects of extracts of leaf litter and live roots of three Eucalyptus species [ Eucalyptus urophylla Blake (Myrtaceae), Eucalyptus citriodora Hook. and Eucalyptus camaldulensis Dehnh] were determined on the following crops: radish [ Raphanus raphanistrum var. sativus L. G. Beck, Brassicaceae), cucumber (Cucumis sativus L., Cucurbitaceae), and Chinese cabbage ( Brassica rapa var. glabra Regel, Brassicaceae)]. The extracts of leaf litter and live roots were inhibitory or stimulatory to test species. However, the effects of leaf litter extracts at lower concentrations were similar to natural concentration in fields and were more pronounced than live roots. When litterfall were removed, Chinese cabbage should be a good candidate crop grown under Eucalyptus urophylla and cucumber should be a good candidate crop grown under all tested Eucalyptus species in the tree-crop agroforestry systems .
TL;DR: It is found that physiological state and cell concentration of competitors were important determinants of allelopathy, with early-stage (lag phase) cells more vulnerable to allelopathic effects than later growth stages for the diatom Skeletonema grethae.
Abstract: The use of chemical compounds to suppress the growth of competitors is a competitive strategy known as allelopathy that can be readily observed with many phytoplankton species in lab- oratory studies. However, it is unclear how these allelopathic interactions are altered when the com- plexity of the system is increased to more closely mimic natural conditions. In the present study, we conducted laboratory experiments to decipher how the identity, abundance, and growth stage of competitors affect the outcome of allelopathic interactions with the red tide dinoflagellate Karenia brevis. Multiple chemical compounds produced by K. brevis were found to inhibit the growth of 4 phytoplankton competitors, although these competitors were susceptible to different combinations of compounds. We found that physiological state and cell concentration of competitors were important determinants of allelopathy, with early-stage (lag phase) cells more vulnerable to allelopathic effects than later growth stages for the diatom Skeletonema grethae. Despite being allelopathic to multiple competitors in the laboratory, in a microcosm experiment using plankton field assemblages, extracel- lular extracts of 2 strains of K. brevis had no effects on some taxa although they stimulated the growth of some diatoms. This suggests that in a species-rich ecological community under oligotrophic condi- tions, the relative importance of K. brevis allelopathy may not be as high as most laboratory studies predict.
TL;DR: The allelopathic activity of itchgrass (Rottboellia cochinchinensis), which can inhibit the seed germination and growth of weeds, is described, which suggests that itchgrass has a strong competitive ability and possible allelopathy activity to other plant species.
Abstract: Herbicides produce a wide range of toxic side-effects that pose a potential hazard to the environment. The development of natural allelochemicals is one method of addressing these issues. Here, we describe the allelopathic activity of itchgrass (Rottboellia cochinchinensis), which can inhibit the seed germination and growth of weeds. Farmers in Lampang, northern Thailand, have been cultivating itchgrass and using it as a mulching material to control other weeds in vegetable fields. It has long been observed that itchgrass interferes with the growth of other plants. This study showed that the density of weed species in the itchgrass-infested areas was lower than that in the itchgrass-uninfested areas. The shoot and root growth of Bidens pilosa, Mimosa pudica, Ageratum conyzoides, Echinochloa crus-galli, Oryza sativa var. RD 6, and Lactuca sativa var. OP were significantly reduced in soil previously planted with itchgrass. Water-soluble extracts from all parts of itchgrass had inhibitory effects on the growth of some test plants. Allelochemicals from itchgrass can inhibit seed germination and plant growth better at a 1 cm distance than at a 3 cm and 5 cm distance from itchgrass. Our results suggest that itchgrass has a strong competitive ability and possible allelopathic activity to other plant species. The allelopathic activity of itchgrass in the soil can influence the germination of adjacent species, causing reduced growth of seedlings.
TL;DR: Analysis of the constituents of the roots of P. cuspidatum from China revealed that stilbenes as piceatannol glucoside, resveratroloside and proanthocyanidins as catechin, epicatechin from this plant were comparatively stronger allelochemicals than the reported allelopathy (−-catechin), which may partly explain the invasive behavior of this plant in Europe.
Abstract: Polygonum cuspidatum Sieb. and Zucc., a traditional Chinese medicine is now a wide-spread invasive neophyte in Europe and America. The novel weapon hypothesis states that some invasive weed species owe part of their success as invaders to allelopathy mediated by some allelochemicals. Previous HPLC/UV/ESI-MS analysis showed that the constituents of the roots of P. cuspidatum from China were obviously different from the species collected in Switzerland (present as an invasive neophyte) with respect to piceatannol glucoside, resveratroloside and some proanthocyanidin. This work isolated these special constituents from the invasive plant and studied their allelopathy effect, as well as the related structures by the seedling and growing model of Lepidium sativum (garden cress, Brassicaceae). The results revealed that stilbenes as piceatannol glucoside, resveratroloside and proanthocyanidins as catechin, epicatechin from this plant were comparatively stronger allelochemicals than the reported allelochemical (−)-catechin, which may partly explain the invasive behavior of this plant in Europe.
TL;DR: The results showed that the aglycone flavonoids degrade very slowly in the soil, remaining a very long time with no further external input, providing a possible explanation for the phytotoxic activity attributed to C. ladanifer.
Abstract: A lower herb richness and diversity in the presence of Cistus ladanifer is attributed to the allelochemicals exudate from its leaves and stem. The objective of the present study was to determine allelopathic activities of C. ladanifer exudates and the persistence of potential allelochemicals in soil environment. The results showed that the aglycone flavonoids degrade very slowly in the soil, remaining a very long time with no further external input. Although the amounts of aglycone flavonoids in soils are low (of the order of μg/g soil), their high persistence may facilitate inhibition of the germination and growth of other species or an indirect effect by altering the soil’s characteristics, providing a possible explanation for the phytotoxic activity attributed to C. ladanifer.