Allelopathic Chemicals Research Articles

Stability analysis of allelopathic effects of Panax notoginseng on main crops by AMMI model

This paper is aimed to study the differences of allelopathic effects of Panax notoginseng under different allelopathic chemicals resources and selection of appropriate rotation crops. The additive main effects and multiplicative interaction ( AMMI) model had been used to evaluate the stability of allelopathic effects of P. notoginseng on the varieties of corn, wheat and rice properly. The model could use not only to evaluate the stability of non-regional trial data but also explore the interaction between the rotation crop genotypes and donor substances more efficiently. Meanwhile, correspondence analysis can be used in the AMMI to evaluate genotype stability and donor substances. Ejingza No. 1 (g6) had stronger allelopathic effects with high stability, but Yunrui No. 1 (g9) which was appropriate rotation crop genotype, had weaker allelopathic effects with high stability. These findings will aid in choosing appropriate rotation crops and establishing proper rotation system.

Effect of fibrous root extract of Coptis chinensis on soil microbes and enzyme activities

Coptis chinensis is widely used as Chinese medicine herbs and serious soil problems occur after continual cultivation of this medicinal plant. In the preset experiment, fibrous root extract of C. chinensis (REC) was added into soil to study the effect of REC on microbes and enzyme activity in soil. The results showed that both bacteria and actinomycetes decreased by about 2 times in contrast to fungi, which increased by about 3 folds. Phosphorus bacteria, potassium bacteria, azotobacter, ammonia bacteria, and nitrifying bacteria were also reduced significantly by REC, suggesting the inhibition of nitrogen biofixation and supply, mobilization of phosphorus and potassium, ad plant growth promotion as REC added into soil. There were multiple influences of REC on soil enzyme activities. Invertase activity was stimulated, while urease was inhibited and dehydrogenase unchanged by REC, indicating the interference of biochemical reactions in soil. In addition, type and total content of phosphorus lipid fatty acids (PLFAs) , the signature of microbes, decreased while the ratio of bacterium to fungus PLFAs increased as REC increased in soil, which suggested that fungi increased relatively with bacteria decreased thereby leading to easy occurrence of crop fungus diseases following cultivation of C. chinensis. The decrease in diversity and evenness indexes of microbial community in soil by REC indicated soil ecosystem deterioration and reduction of microbial groups and densities in soil. Therefore, allelopathic chemicals released from the roots of C. chinensis could change microbial community structure and resulted in serious soil problems by continual cropping of this medicinal plant.

Nitric oxide and hydrogen peroxide are important signals mediating the allelopathic response of Arabidopsis to p‐hydroxybenzoic acid

Both nitric oxide (NO) and hydrogen peroxide (H2 O2 ) are important signals that mediate plant response to environmental stimulation. Their role in plants' allelopathic interactions has also been reported, but the underlying mechanism remains little understood. p-Hydroxybenzoic acid (pHBA) has been proposed to be an allelopathic chemical. Here, we found that pHBA at 0.4 mM efficiently suppressed Arabidopsis growth. Meanwhile, pHBA rapidly induced the accumulation of NO and H2 O2 , where such effect could be reversed by NO or H2 O2 metabolism inhibitors or scavengers. Also, pHBA-induced NO and H2 O2 could be compromised in NO synthesis mutants noa1, nia1 and nia2, or H2 O2 metabolism mutant rbohD/F, but suppressing NO accumulation with a NO synthesis inhibitor or using NO synthesis-related mutants did not reduce pHBA-induced H2 O2 accumulation. Furthermore, we found that the effect of pHBA on allelopathic inhibition of growth was aggravated in NO/H2 O2 metabolism-related mutants or reducing NO/H2 O2 by different inhibitors, whereas the addition of an NO/H2 O2 donor could partly relieve the inhibitory effect of pHBA on the growth of wild type. However, adding only an NO donor, but not low concentration of H2 O2 as the donor, could relieve the inhibitory effect of pHBA on root growth in NO metabolism mutants. On the basis of these results, we propose that both NO and H2 O2 are important signals that mediate Arabidopsis response to the allelopathic chemical pHBA, where during this process H2 O2 may work upstream of the NO signal.

<i>Taraxacum officinale</i> pollen depresses seed set of montane wildflowers through pollen allelopathy

Plant species that share pollinators can suffer from interspecific pollen deposition. Male reproductive success is inevitably reduced by the loss of pollen to flowers of another species. Female reproductive success can be affected by reduced stigmatic area or, more strongly, through allelopathic effects by which the admixture of some foreign pollen reduces seed or fruit set. We tested for allelopathic effects of Taraxacum officinale (Asteracaeae) pollen on the seed set of montane wildflowers Erythronium grandiflorum (Liliaceae) and Erysimum capitatum (Brassicaceae), by hand-pollinating plants with pollen mixtures. Taraxacum is a common invasive species, which produces allelopathic chemicals in its root and vegetative tissue, making it a likely candidate for pollen allelopathy. Flowers of both species produced fewer well-developed seeds when pollinated with pollen mixtures containing Taraxacum pollen. The pollen-allelopathic potential of weedy dandelion may add to its ability to disrupt communities that it invades.

An investigation of allelopathic effects of Artemisia herba-alba Asso, aqueous extract on common bean (Phaseolus vulgaris L.)

The objective of this study was to investigate the impact of allelopathic potentials of aqueous extract of Artemisia herba-alba aerial parts on germination and secondary metabolites accumulation in common bean seedlings. Quantitative analysis of aqueous extract of Artemisia showed the phenolic compounds and flavonoids that might be concerned as allelo-chemicals agents. After 8 days, the germinated common bean seedlings were significantly inhibited with the increase in concentration of Artemisia extract. However, the phenolic compounds in common bean seedlings increases when the concentration of Artemisia extract increased. Degradation of storage carbohydrates of common bean seedlings was significantly increased with increasing the concentration of Artemisia extract. It seems that the enhance-ment of total carbohydrates was attributed to the inhibition of amylase activity that reduced the contents of reducing and non-reducing sugars. However, the polysaccharides remained at high level when compared with those of the control. Inhibition of protease activity led to accumulation of free amino acids and protein contents in germinated seedlings of common bean. Although, 4% aqueous extract of Artemisia shoots contains allelopathic chemicals and phytotoxic, this effect led to an increase in unsaturated and saturated fatty acids in germinated common bean seedlings.

Operation Allelopathy: An Experiment Investigating an Alternative to Synthetic Agrochemicals

Synthetic herbicides represent a serious problem in modern agriculture because they are not biodegradable and can accumulate in the soil and in the groundwater, a situation that allows them to enter the trophic chain and ultimately leads to human exposure. Allelopathic chemicals offer an effective alternative to the synthetic compounds. The aim of this experiment is to highlight the differences between chemical and biological control of diseases in crops and to demonstrate the use of natural fungicides and herbicides as alternatives to synthetic chemicals. The experiment involves an evaluation by students of the potential of plant extracts as an alternative to synthetic agrochemicals to identify new ecological farming techniques that could be applied in agriculture. In an effort to encourage 1800 students in high school (14 to 16 years old) to have an interest in science, technology, and innovation, the third edition of the Summer Science Campus was organized by the Spanish Foundation for Science and Tech...

Steers Grazing a Rye Cover Crop Influence Growth of Rye and No‐Till Cotton

Small grain cover crops offer grazing opportunities but effects on following row crops are not well understood. From 1999 through 2008, stocker steers (Bos taurus) grazed small grains in a two‐paddock crop rotation of rye (Secale cereale L.), cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.), fallow, and rye. Treatments in 2005, 2007, and 2008 included (i) zero‐grazed rye from 1999; (ii) ungrazed rye in the current year only; (iii) always grazed rye; and (iv) in 2007 and 2008, monoculture cotton (since 1999) with no cover crop. The experiment, on a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustolls), was a randomized complete block design with three blocks. Ungrazed rye was mechanically harvested before planting cotton. Rye excluded from grazing in 1 yr only (Treatment 2) was taller (P < 0.05) and produced more forage mass than zero‐grazed rye (Treatment 1), likely due to higher rye tiller numbers, weight, and basal cover. Cotton planted into grazed rye had more plants m–1 row and was taller until July (P < 0.05), and in 2005 had greater (P < 0.05) lint and seed yield than where grazing was excluded. Continuous cotton with no cover crop (Treatment 4) was shorter (P < 0.01) than cotton grown with a cover crop regardless of grazing. Known allelopathic chemicals were detected in rye and soil where rye grew and appeared to be influenced by grazing. Increased growth and productivity of rye and cotton where grazing occurred may be related to suppressive effects of grazing on allelopathy.

A Facile Synthesis of (±)-Heliannuol-D

A facile synthesis of (+/-)-heliannuol-D 1, which serves as an allelopathic chemical in nature and a potential lead compound in the search for new herbicides, has been achieved in a linear 11 steps, together with its epimer. The synthesis commenced with 4-methoxy-3-methyl-acetophenone, through the Baeyer-Villiger reaction, lithiation and addition, epoxidation and intramolecular cyclization to give (+/-)-heliannuol-D (1) and its epimer (la) in 32.6% overall yield. Our synthetic approach is cost-effective; this will be helpful in applying this kind of compound for the development of a new generation of agrochemicals.

Response of the Toxic Cyanobacterium Microcystis aeruginosa to Bacteria Signaling Molecules AHLs - Change of Volatile Components Production

N-acyl homoserine-lactones (AHLs) are essential bacteria signaling molecules which regulate many physiological behaviors of Gram-negativebacteria. Previous studies have shown that AHLs can affect the growth and primary physiological processes of the bloom-forming cyanobacteriumMicrocystisaeruginosa. The aim of this study was to examine whether and how the presence of AHLs substances may affect the release of volatile chemicals ofM. aeruginosa. Hydrodistillation and GC-MS were used to extract and analysis the volatile components of cells in exponential and stationary growth stage in normal growth condition and cells in exponential stage with additional AHLs. The results demonstrated that allelopathic chemicals existing in the stationary phase were induced and released when AHLs was added into the culture of cells in exponential phase, which indicated that AHLs may play role in growth state transition and interspecific competition inM. aeruginosavia regulation of production and release of volatile chemicals.

Conditional allelopathic potential of temperate lianas

Allelopathy is often treated as an innate characteristic of a species rather than a phenotypically plastic trait that can vary with environmental conditions. Lianas are a highly competitive, phenotypically plastic life form that typically occur in both shaded and unshaded environments. As such, we hypothesized that temperate lianas may conditionally change allocation to allelopathic chemicals in response to light availability though the expected direction of change is unclear. Shading may reduce resource availability and therefore reduce allocation to allelochemicals, induce allelopathy as a competitive mechanism, or may not be related to allelopathy. To test the conditionality of allelopathy, sun and shade leaves of five common liana species (Toxicodendron radicans, Parthenocissus quinquefolia, Celastrus orbiculatus, Lonicera japonica, and Vitis vulpina) were collected from a young deciduous forest in New Jersey, USA, and tested with laboratory bioassays to detect allelopathic potential. All liana species showed allelopathic potential, and three species exhibited induction of increased allelopathic potential in shaded environments. The two species that were not shade induced are late successional lianas that persist for long periods in forest canopies. In contrast, the inducible lianas were early successional species that typically decline with canopy closure. This research indicates that lianas have the potential to be allelopathic and allelopathic potential conditionally responds to shading only for species that would normally be excluded from the forest canopy. As early successional lianas are present throughout forest regeneration in a range of light environments, allelopathic plasticity may increase their success by differentially allocating resources based on environmental conditions.

Effects of invasive macrophytes on freshwater fish and macroinvertebrate communities: the role of invasive plant traits

Biological invasions of aquatic plants (i.e., macrophytes) are a worldwide phenomenon, and within the last 15 years researchers have started to focus on the influence of these species on aquatic communities and ecosystem dynamics. We reviewed current literature to identify how invasive macrophyte species impact fishes and macroinvertebrates, explore how these mechanisms deviate (or not) from the accepted model of plant–fish interactions, and assess how traits that enable macrophytes to invade are linked to effects on fish and macroinvertebrate communities. We found that in certain instances, invasive macrophytes increased habitat complexity, hypoxia, allelopathic chemicals, facilitation of other exotic species, and inferior food quality leading to a decrease in abundance of native fish and macroinvertebrate species. However, mechanisms underlying invasive macrophyte impacts on fish and macroinvertebrate communities (i.e., biomass production, photosynthesis, decomposition, and substrate stabilization) were not fundamentally different than those of native macrophytes. We identified three invasive traits largely responsible for negative effects on fish and macroinvertebrate communities: increased growth rate, allelopathic chemical production, and phenotypic plasticity allowing for greater adaptation to environmental conditions than native species. We suggest that information on invasive macrophytes (including invasive traits) along with environmental data could be used to create models to better predict impacts of macrophyte invasion. However, effects of invasive macrophytes on trophic dynamics are less well-known and more research is essential to define system level processes.

Effects of methanol extracts from Ophiopogon japonicus on rice blast fungus

Previous studies showed that dwarf lilyturf ( Ophiopogon japonicus Ker-Gawl.) (Izawa 1967, ishima 1963) contains allelopathic chemicals, which inhibited the germination and initial growth of three weeds — barnyardgrass ( Echinochloa crusgalli L.), monochoria ( Monochoria vaginalis Presl), and small flower umbrella ( Cyperus difformis L.) (Lin 2001). This study determined whether methanol extracts of dwarf lilyturf have inhibitory effects on rice blast fungus Pyricularia grisea .

Not novel, just better: competition between native and non-native plants in California grasslands that share species traits

Invasive plants have often been shown to possess novel traits such as the ability to fix nitrogen, access unused resource pools, or the ability to exude allelopathic chemicals. We describe a case of a successful invasion where the native and non-native species are very similar in most life-history characteristics including their growth forms, lifespan, and degree of summertime activity. Data from permanent transects suggest that exotic perennial grass invaders can establish into intact native-dominated grasslands, achieving cover values from 6 to 71% over several years. We also established a 4-year competition experiment to test the effect of each group—the native and non-native perennial grasses—on the other. Competitive interactions were found to consistently favor the non-native grasses: native perennial grass productivity was significantly lower in plots with exotic perennial grasses as compared to plots without exotic perennial grasses. By contrast, productivity of the exotic perennial grasses was not reduced by the presence of the native perennial grasses. These results suggest that competitive ability, rather than a unique trait, has contributed to the success of the exotic perennial grasses in our system. Management tools to control exotic perennial grass invasions are likely to negatively influence native perennial grass populations, as strategies that succeed against the invasive species may kill or reduce the native species as well.

Current Status of Mathematical Models for Population Dynamics of Prymnesium parvum in a Texas Reservoir1

Grover, James P., Jason W. Baker, Daniel L. Roelke, and Bryan W. Brooks, 2010. Current Status of Mathematical Models for Population Dynamics of Prymnesium parvum in a Texas Reservoir. Journal of the American Water Resources Association (JAWRA) 46(1):92‐107. DOI: 10.1111/j.1752‐1688.2009.00393.xAbstract: Blooms of the harmful alga Prymnesium parvum have apparently increased in frequency in inland waters of the United States, especially in western Texas. A suite of mathematical models was developed based on a chemostat (or continuously stirred tank reactor) framework, and calibrated with data from Lake Granbury, Texas. Inputs included data on flows, salinity, irradiance, temperature, zooplankton grazing, and nutrients. Parameterization incorporated recent laboratory studies relating the specific growth rate of P. parvum to such factors. Models differed in the number of algal populations competing with P. parvum, and whether competition occurred only by consumption of shared nutrients, or additionally through production of an allelopathic chemical by one of the populations, parameterized as cyanobacteria. Uncalibrated models did not reproduce the observed seasonal dynamics of P. parvum in Lake Granbury, which displayed a maximum population in late February during a prolonged bloom in cooler weather, and reduced abundance in summer. Sensitivity analyses suggested two modifications leading to predictions that better resembled observations. The first modification greatly reduces the optimal temperature for growth of P. parvum, an approach that disagrees with laboratory experiments indicating a strong potential for growth at temperatures above 20°C. The second modification increases the growth rate of P. parvum at all temperatures, in models including cyanobacterial allelopathy. Despite these adjustments, calibrated models did not faithfully simulate all features of the seasonal dynamics of P. parvum.

Enhanced fitness due to higher fecundity, increased defence against a specialist and tolerance towards a generalist herbivore in an invasive annual plant

Aims: The superior performance of many non-indigenous species in a new range can be attributed to different factors such as pre-adaptation to environmental conditions in new areas or to factors inherent to dis- placement mechanisms such as loss of co-evolved pathogens and herbivores that increase the speed of evolutionary change towards a shift in allocation from defence to growth and reproduction. To as- sess the importance of the different mechanisms governing the suc- cess of Conyza canadensis, a globally successful invader, we simultaneously tested several recent hypotheses potentially explain- ing the factors leading to biological invasion. Methods: We tested (i) whether plants from the non-native range showed a higher fitness than plants from the native North American range, (ii) whether they differed in resistance against an invasive generalist herbivore, the slug Arion lusitanicus and against a recently estab- lished specialist aphid herbivore, Uroleucon erigeronense and (iii) experimentally assessed whether C. canadensis releases allelopathic chemicals that have harmful effects on competing species in the non- native range. We compared populations along a similar latitudinal gradient both in the native North American and invasive European range and analysed patterns of adaptive clinal variation in biomass production.

Do phytoplankton communities evolve through a self-regulatory abundance–diversity relationship?

A small group of phytoplankton species that produce toxic or allelopathic chemicals has a significant effect on plankton dynamics in marine ecosystems. The species of non-toxic phytoplankton, which are large in number, are affected by the toxin-allelopathy of those species. By analysis of the abundance data of marine phytoplankton collected from the North-West coast of the Bay of Bengal, an empirical relationship between the abundance of the potential toxin-producing species and the species diversity of the non-toxic phytoplankton is formulated. A change-point analysis demonstrates that the diversity of non-toxic phytoplankton increases with the increase of toxic species up to a certain level. However, for a massive increase of the toxin-producing species the diversity of phytoplankton at species level reduces gradually. Following the results, a deterministic relationship between the abundance of toxic phytoplankton and the diversity of non-toxic phytoplankton is developed. The abundance–diversity relationship develops a unimodal pathway through which the abundance of toxic species regulates the diversity of phytoplankton. These results contribute to the current understanding of the coexistence and biodiversity of phytoplankton, the top-down vs. bottom-up debate, and to that of abundance–diversity relationship in marine ecosystems.

Attack is not the best form of defense: Lessons from harmful algal bloom dynamics

The potential roles that allelopathic, grazing deterrence and predator-killing chemicals have in shaping planktonic food webs are considered making use of models in which variable prey selection and stoichiometry are described. Allelopathy does not aid the growth of a poor competitor for resources unless some other factors initially elevate the biomass of the producer and hence increase the levels of allelopathic chemicals to exceed a critical level. Killing a predator is only of use for a strong resource competitor; otherwise removal of a predator that also controls the growth of competitors is disadvantageous. Killing a predator that also controls the biomass and activity of another predator (e.g. the toxic action of diatom-originating polyunsaturated aldehydes on copepods, thus releasing grazing pressure by copepods upon microzooplankton) also appears disadvantageous. The best recourse for a moderate-to-poor resource competitor appears to be predator deterrence; low-level growths of such organisms probably provide little natural selective stimulation for the evolution of counter-measures by predators. Factors that disturb the natural balance of the system, such as disproportionate N:P(:Si) eutrophication, may provide deterrence-producing algae with a window of opportunity from which they may then form HABs. However, the failings of non-HAB species to bloom are just as important in dictating the success of a HAB species under any given set of conditions. The simulation of such events thus requires inclusion of non-HAB as well as HAB descriptions, and also of their predators, in a modeling framework capable of capturing the dynamics of prey selection and rejection.

Allelopathic effects of fruits of the Brazilian pepper Schinus terebinthifolius on growth, leaf production and biomass of seedlings of the red mangrove Rhizophora mangle and the black mangrove Avicennia germinans

Exotic plant species can negatively affect native flora and fauna by changing the diversity and productivity of the system and altering successional processes. The novel weapons hypothesis has been suggested as one mechanism for invasion and spread of exotic plant species. It states that exotic species with “new weapons”, such as allelopathic chemicals, may have greater impacts on species in the invaded range without co-evolved defense strategies against the exotic chemicals. In Florida, one successful exotic species, Schinus terebinthifolius (Brazilian pepper), has invaded nearly every habitat throughout the state. Past studies have documented allelopathic properties of S. terebinthifolius negatively impacting the growth of native terrestrial flora. Here we document the effect of S. terebinthifolius for the first time on mangrove systems. We examined growth and survival of Rhizophora mangle (red mangrove) and Avicennia germinans (black mangrove) seedlings when exposed to a range of densities of intact and crushed S. terebinthifolius fruits (0, 25, 50) at two different salinities (15, 30 ppt). We also documented the natural density of S. terebinthifolius fruits beneath the tree canopy after fruit production in mangrove habitat. Growth and biomass were significantly reduced in A. germinans when exposed to the highest density of intact S. terebinthifolius fruits growing in 30 ppt saltwater. Trials with intact fruits had no significant effects on R. mangle; however, crushed fruits significantly decreased growth, and leaf production. The ecological importance of the different effects of crushed and intact fruits is supported by field observations which found equal or greater numbers of crushed fruits compared to intact fruits beneath the tree canopy of female S. terebinthifolius. In addition, abiotic factors, such as salinity, may interact with allelopathic chemicals in natural systems and needs to be addressed when planning future allelopathic studies.

Assessing potential biological control of the invasive plant, tree-of-heaven, Ailanthus altissima

Tree-of-heaven, Ailanthus altissima, is a deciduous tree indigenous to China and introduced into North America and Europe. It is a serious threat to ecosystems in introduced areas, as the plant is very competitive, and also contains allelopathic chemicals that may inhibit growth of surrounding native plants. In addition, the plant contains secondary chemicals that make it unpalatable to some insects. In this paper we assess potential biological control of this plant by reviewing literature associated with natural enemies of the plant from both its native and introduced regions in the world. Our literature surveys revealed that 46 phytophagous arthropods, 16 fungi, and one potyvirus were reported attacking tree-of-heaven, some apparently causing significant damage in China. Two weevils, Eucryptorrhynchus brandti and E. chinensis, are major pests of the plant in China and are reportedly restricted to tree-of-heaven, showing promise as potential biological control agents. Nymphs and adults of a homopteran insect, Lycorma delicatula and larvae of two lepidopteran species, Samia cynthia and Eligma narcissus, may also cause severe damage, but they are not host specific. Two rust fungi, Aecidium ailanthi J. Y. Zhuan sp. nov. and Coleosporium sp. have been reported on tree-of-heaven in China and are also promising potential candidates for biological control of the plant. Nine insect herbivores and 68 fungi are associated with tree-of-heaven in its introduced range in North America, Europe, and Asia. An oligophagous insect native to North America, the ailanthus webworm, Atteva punctella, may be a potential biocontrol agent for the plant. Among the fungal species, Fusarium osysporum f. sp. perniciosum, caused wilt of tree-of-heaven in North America and may have the potential to control the plant, but its non-target effect should be carefully evaluated. Our review indicates that there is potential for using insects or pathogens to control tree-of-heaven.

Antialgal, antibacterial and antifungal activity of two metabolites produced and excreted by cyanobacteria during growth

The antimicrobial activity of two cyanobacterial exometabolites, norharmane (9H-pyrido(3,4-b)indole) and 4,4'-dihydroxybiphenyl, was determined in suspension assays. Good anticyanobacterial activities (concentrations of 8-80 microg ml(-1)) and moderate antibacterial (16-160 microg ml(-1)) and antifungal (32-40 microg ml(-1)) activities were found for both compounds. The natural function as allelopathic chemicals and a possible applicability as antifouling agents or leads for the development of new antifouling chemicals are discussed.