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The allelopathic effect of macrophytes to phytoplankton has been widely formalized and accepted, while, less attention has been paid to aquatic vegetable. Herein, we investigated the inhibitory ability of Ipomoea aquatica (I. aquatica) at different concentrations to Microcystis aeruginosa, and verified the inhibition effect of main allelopathic substances. Results showed that, I. aquatica root secretion solution could effectively inhibit the growth of Microcystis aeruginosa (95%), and exhibited a concentration dependent effect. Seven potential allelopathic substances was both detected in root exudates and secretion solution of I. aquatic, they were succinic acid, salicylic acid, cinnamic acid, 3-(4-hydroxyphenyl) propionic acid, trans-cinnamic aldehyde, coumarin, and isophorone. Exogenous addition experiment further verified the inhibition effect, and the inhibition level varied with the types. Succinic acid, salicylic acid and cinnamic acid showed the tendency of promotion in lower concentration and inhibition in high concentration, with the inhibition threshold of 0.8 mmol/L, which was positively correlated with its concentration. 3-(4-hydroxyphenyl) propionic acid, coumarin and isophorone showed strong inhibition on Microcystis aeruginosa when the concentration was higher than 0.2 mmol/L, which was positively correlated with its concentration and co-culture time. Ipomoea aquatica can continuously release allelopathic substances under natural conditions and is expected to contribute to the restoration of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Plantations of exotic trees were proposed as an alternative to restore native forests in degraded lands, because they can attract seed dispersers and modulate the microclimate beneath their canopies. However, the large-scale introduction of exotic tree plantations can negatively affect native species by high competitiveness for soil resources and light, while they can also release allelopathic compounds that inhibit the germination and growth of other plants. In this study, we tested the suitability of Eucalyptus camaldulensis plantations to assist the restoration of degraded lands in central Mexico, which were originally covered with oak forests. For this, we sampled soil seed banks within forest remnants and plantations, which showed that the animal-mediated dispersal of oak propagules from forests inwards plantations is reduced. Additionally, we conducted germination trials that evidenced that the leaves of Eucalyptus trees contain allelopathic compounds that inhibit the germination of oaks seeds, also showing that these compounds accumulate in the soil of plantations. We finally conducted field experiments in which soil form forests and plantations were translocated between these two habitats, and acorns were sowed on both soil types. These field experiments revealed that, besides the accumulation of allelopathic compounds in soils of plantations, oak recruitment in these habitats is also impaired by unfavorable microclimatic conditions. Therefore, we conclude that Eucalyptus plantations are not promoting the recovery of native oak forests in central Mexico and, instead, alternative ecological restoration methods should be applied for reaching this aim. [ABSTRACT FROM AUTHOR]

Allelopathy has a profound impact on the germination and growth of plants, influencing the establishment of plant populations and shaping community ecological patterns. However, the allelopathic potential of many grassland species remains poorly understood. In this study, we prepared aqueous extracts from 17 herbaceous plants to investigate their allelopathic effects on the seed germination and seedling growth of Leymus chinensis, a dominant grassland species. Our results revealed that the response of L. chinensis to allelopathic compounds was dependent on the specific plant species, extract concentration, and target plant organ. Notably, Fabaceae plants exhibited a stronger allelopathic potential than Poaceae, Asteraceae, and other plant families. Moreover, we observed that root growth of L. chinensis was more sensitive to allelopathy than shoot growth, and seed germination was more affected than seedling growth. Generally, the germination of L. chinensis was strongly inhibited as the donor plant extract concentration increased. The leachate of Fabaceae plants inhibited the seedling growth of L. chinensis at concentrations ranging from 0.025 to 0.1 g mL−1. On the other hand, the leachate from other families' plants exhibited either inhibitory or hormetic effects on the early growth of L. chinensis, promoting growth at 0.025 g mL−1 and hindering it at concentrations between 0.05 and 0.1 g mL−1. These findings highlight the significant allelopathic potential of grassland plants, which plays a critical role in establishing plant populations and associated ecological processes. In addition, they shed light on the coexistence of other plants with dominant plants in the community. [ABSTRACT FROM AUTHOR]

In the framework of benthic harmful algal bloom monitoring, the most common sampling strategy is based on the collection of macroalgae, and the abundance of epiphytic microalgae are mainly expressed as cells g−1 macroalgal fresh weight (fw). However, this methodology has some inherent problems, due to (i) the thallus-specific weights that markedly differ among algal species, (ii) the thallus architecture, and (iii) the production of allelopathic compounds that affects the epiphyte abundances among macroalgae, irrespective of the available colonizable surface. This study proposes a method to compare the abundances of Ostreopsis cf. ovata cells on different substrata, using a conversion factor that converts the abundances expressed as cells g−1 fw (or dry weight) to cells cm−2. Expressing abundances in terms of cells cm−2, the abundances can be compared (i) among different macroalgal species and (ii) between macroalgae and other substrata (such as rocks, pebbles, or shellfish shells). We also propose to normalize abundances when different macroalgae are sampled throughout the bloom period, considering the different epiphyte loads of different macroalgal species regardless of the available surface area. [ABSTRACT FROM AUTHOR]

The secondary metabolites of indigenous plants have significant allelopathic inhibitory effects on the growth and development of invasive alien plants. Methyl palmitate (MP) and methyl linolenate (ML) were used as exogenous allelopathic substances. The research investigated the differences of inhibitory effects of MP and ML on the growth of seedlings of Alternantheraphiloxeroides, and calculated their morphological characteristics, biomass, physiological indicators and the response index (RI). The synthetical allelopathic index (SE) of 1 mmol/L MP was the smallest (− 0.26) and the allelopathic inhibition was the strongest; therefore, it was selected as a 13C-labeled allelochemical. The distribution of 1 mmol/L MP in different parts of A.philoxeroides and the correlation between the biomass ratios of roots, stems and leaves and the 13C content were studied by 13C stable isotope tracing experiments. Atom percent excess (APE) between roots, stems and leaves of A.philoxeroides treated with 1 mmol/L MP were significantly different in terms of magnitude, with leaves (0.17%) > roots (0.12%) > stems (0.07%). The root, stem and leaf biomass ratios of invasive weeds had great significant positive correlation with 13C content (p < 0.01, R2 between 0.96 and 0.99). This current research provides a new idea and method for the control of A.philoxeroides, but large-scale popularization remains to be studied. [ABSTRACT FROM AUTHOR]

The sustainable management of the environment and crop production in modern agriculture involves dealing with challenges from climate change, environmental pollution, depletion of natural resources, as well as pressure to cope with dependence on agricultural inputs. Balancing crop productivity with environmental sustainability is one of the main challenges for agriculture worldwide. The emergence of weeds resistant to synthetic herbicides generates huge economic losses, so unconventional weed control strategies, especially those based on ecological principles, are very much needed in modern agriculture. Incorporating a natural eco-friendly approach—allelopathy—as a tool in an integrated weed control plan by growing specific crops or spraying fields with extracts containing allelopathic compounds can significantly reduce the use of herbicides. Allelopathy is considered a multi-dimensional phenomenon occurring constantly in natural and anthropogenic ecosystems, by which one organism produces biochemicals that influence the growth, survival, development, and reproduction of other organisms. The objective of this systematic literature review is to present a comprehensive overview of allelopathy, define this phenomenon, and classify allelochemicals. This paper also discusses and highlights recent advances, ongoing research, and prospects on plant allelopathy management practices applied in agriculture, and the underlying allelopathic mechanisms. The review suggested the holistic view of some allelochemicals as an ecological approach to integrated weed control and is an important contribution to future research directions of multidisciplinary programs, chemoinformatic tools, and novel biotechnology methods to plant breeding. [ABSTRACT FROM AUTHOR]

Background: In the past neutral and ionized, i.e., total, molecules of monoprotic phenolic acids such as cinnamic and benzoic acids were assumed to be the active inhibiting molecules for seedling processes. Re-analyses of data for water utilization, growth, and uptake of nutrient and phenolic acid by seedlings have, however, demonstrated that their inhibition is primarily due to neutral molecules. Thus, past estimates of concentrations for inhibition of seedling processes based on total molecules were with few exceptions incorrect, i.e., too high. Methods: Published data for two monoprotic cinnamic acids and cucumber seedlings as surrogates for sensitive seedlings were utilized in an attempt to identify the relationships between neutral molecule concentrations and inhibition and to identify the inherent limitations for determining such relationships based on changes in treatment solution properties. Results and Conclusions: Results indicate that keeping track of available total monoprotic acid concentrations and solution pH values over time are a step in the right direction when determining the concentrations of neutral molecules required for the inhibition of a seedling process. However, different delay times for the inhibition of different seedling processes, increasing or decreasing inhibition of seedling processes as neutral molecules increase or decrease, respectively, potential changes in seedling tolerances, and the dynamics of treatment solution properties present obstacles for determining precise concentrations for the % inhibition of seedling processes by neutral molecules. [ABSTRACT FROM AUTHOR]

Herbicides are commonly used to control weed. However, some plants are resistant to such products. To identify less harmful herbicides, it is crucial to search for different mechanisms of action. Thymol is an easily acquired allelopathic compound, capable of producing its respective semisynthetic derivative, thymoxyacetic acid. The aim of this study was to determine the effects of thymol and thymoxyacetic acid molecules as bioherbicides in greenhouse at the concentration of 3 mmol L−1 in pre- and postemergence applications in five species: Amaranthus viridis L., Cucumis sativus L., Lactuca sativa L., Eleusine indica L., and Sorghum bicolor L. The initial seedling development and DNA changes were analyzed. These molecules were contrasting with the solvent, in the negative control, and with the glyphosate, in the positive control, promoting phytogenotoxic activities. The toxic effect of thymoxyacetic acid was more effective in preemergence and thymol's in postemergence. We also observed a reduction in the germination speed index and root growth with a negative correlation to the increase in potassium leaching. Damage to the root and shoot of the seedlings was verified at the DNA level, and the phytotoxicity of the plants treated with the herbicide glyphosate was similar to the plants treated with the natural molecules tested. The bioherbicidal effect of thymol and thymoxyacetic acid exacerbates the reduction of the environmental impact caused by the disordered and increased use of residual pesticides. [ABSTRACT FROM AUTHOR]

Introduction: Compared to synthetic herbicides, natural products with allelochemical properties can inhibit weed germination, aiding agricultural output with less phytotoxic residue in water and soil. Objectives: To identify natural product extracts of three Cassia species; C. javanica, C. roxburghii, and C. fistula and to investigate the possible phytotoxic and allelopathic potential. Methods: Allelopathic activity of three Cassia species extracts was evaluated. To further investigate the active constituents, untergated metabolomics using UPLC-qTOF-MS/MS and ion-identity molecular networking (IIMN) approach was performed to identify and determine the distribution of metabolites in different Cassia species and plant parts. Results: We observed in our study that the plant extracts showed consistent allelopathic activity against seed germination (P < 0.05) and the inhibition of shoot and root development of Chenopodium murale in a dose-dependent manner. Our comprehensive study identified at least 127 compounds comprising flavonoids, coumarins, anthraquinones, phenolic acids, lipids, and fatty acid derivatives. We also report the inhibition of seed germination, shoot growth, and root growth when treated with enriched leaf and flower extracts of C. fistula, and C. javanica, and the leaf extract of C. roxburghii. Conclusion: The present study recommends further evaluation of Cassia extracts as a potential source of allelopathic compounds in agricultural systems. [ABSTRACT FROM AUTHOR]

Studies on plant defense mechanisms in stressful conditions predict that plant cope up with increasing stress for survival. Under environmental stress plants interact with problems like competition and survival under resource constraints or utilization of these resources in production of secondary compounds. In this experiment, we examined the costs of defense by evaluating variation in production of secondary compounds of Brassica nigra grown in the saline (B1 = 100 mM NaCl and B2 = 150 mM NaCl) and control (C = 0 mM) soils and impact of its extracts on weed Anagallis arvensis L. The main allelopathic compounds in Brassica were determined using gas chromatography–mass spectroscopy (GC–MS). The results indicated that A. arvensis was adversely affected by the aqueous extracts of B. nigra. These observations might be related to extracts induced oxidative stress indicated by superoxide (O2−) production through nitroblue tetrazolium, cell integrity by Evans blue staining, malondialdehyde estimation by Schiff reagent, lipid peroxidation, lignin deposition, and antioxidant enzyme activities assay. We observed that soil salinity reduced the phytotoxicity of aqueous extract and decreased its potential. The presence of different bioactive compounds improved the natural herbicidal properties of B. nigra and it can be used in various medicinal and agricultural practices. [ABSTRACT FROM AUTHOR]

Background and aims: Shrubs of the genus Baccharis are considered key nurse plants for the Chilean matorral, but some species have allelopathic compounds in their leaves. These compounds can leach into the soil, casting doubt on their nurse role. We assessed the nurse effect of B. paniculata, a species with allelopathic compounds in their leaves, in a central Chilean matorral site by determining the richness and cover of species growing beneath the shrub canopy and open areas, by quantifying the microclimate beneath the canopy and by experimentally assessing the microclimate versus the soil effect of this species on planted seedlings of tree dominant tree species.Beneath shrubs and in open areas we recorded the number and cover of species as well air and soil temperature, relative humidity of the air, photosynthetic photon flux density (PPFD) and soil water content. We planted seedlings of Lithrea caustica, Quillaja saponaria, and Cryptocarya alba in both habitats using soils from open areas and from beneath Baccharis to distinguish their effects on seedling’s photochemical efficiency and survival.No woody species grew beneath B. paniculata. Air temperature was similar in both habitats, but soil temperature and PPFD were lower, and soil moisture was higher beneath shrubs. Seedling’s photochemical efficiency and survival were generally higher beneath canopies but were negatively affected by soil from beneath Baccharis shrubs.Our findings question the nurse role of B. paniculata in the Chilean matorral, emphasizing the need to consider other shrub species for restoration initiatives for central Chile.Methods: Shrubs of the genus Baccharis are considered key nurse plants for the Chilean matorral, but some species have allelopathic compounds in their leaves. These compounds can leach into the soil, casting doubt on their nurse role. We assessed the nurse effect of B. paniculata, a species with allelopathic compounds in their leaves, in a central Chilean matorral site by determining the richness and cover of species growing beneath the shrub canopy and open areas, by quantifying the microclimate beneath the canopy and by experimentally assessing the microclimate versus the soil effect of this species on planted seedlings of tree dominant tree species.Beneath shrubs and in open areas we recorded the number and cover of species as well air and soil temperature, relative humidity of the air, photosynthetic photon flux density (PPFD) and soil water content. We planted seedlings of Lithrea caustica, Quillaja saponaria, and Cryptocarya alba in both habitats using soils from open areas and from beneath Baccharis to distinguish their effects on seedling’s photochemical efficiency and survival.No woody species grew beneath B. paniculata. Air temperature was similar in both habitats, but soil temperature and PPFD were lower, and soil moisture was higher beneath shrubs. Seedling’s photochemical efficiency and survival were generally higher beneath canopies but were negatively affected by soil from beneath Baccharis shrubs.Our findings question the nurse role of B. paniculata in the Chilean matorral, emphasizing the need to consider other shrub species for restoration initiatives for central Chile.Results: Shrubs of the genus Baccharis are considered key nurse plants for the Chilean matorral, but some species have allelopathic compounds in their leaves. These compounds can leach into the soil, casting doubt on their nurse role. We assessed the nurse effect of B. paniculata, a species with allelopathic compounds in their leaves, in a central Chilean matorral site by determining the richness and cover of species growing beneath the shrub canopy and open areas, by quantifying the microclimate beneath the canopy and by experimentally assessing the microclimate versus the soil effect of this species on planted seedlings of tree dominant tree species.Beneath shrubs and in open areas we recorded the number and cover of species as well air and soil temperature, relative humidity of the air, photosynthetic photon flux density (PPFD) and soil water content. We planted seedlings of Lithrea caustica, Quillaja saponaria, and Cryptocarya alba in both habitats using soils from open areas and from beneath Baccharis to distinguish their effects on seedling’s photochemical efficiency and survival.No woody species grew beneath B. paniculata. Air temperature was similar in both habitats, but soil temperature and PPFD were lower, and soil moisture was higher beneath shrubs. Seedling’s photochemical efficiency and survival were generally higher beneath canopies but were negatively affected by soil from beneath Baccharis shrubs.Our findings question the nurse role of B. paniculata in the Chilean matorral, emphasizing the need to consider other shrub species for restoration initiatives for central Chile.Conclusion: Shrubs of the genus Baccharis are considered key nurse plants for the Chilean matorral, but some species have allelopathic compounds in their leaves. These compounds can leach into the soil, casting doubt on their nurse role. We assessed the nurse effect of B. paniculata, a species with allelopathic compounds in their leaves, in a central Chilean matorral site by determining the richness and cover of species growing beneath the shrub canopy and open areas, by quantifying the microclimate beneath the canopy and by experimentally assessing the microclimate versus the soil effect of this species on planted seedlings of tree dominant tree species.Beneath shrubs and in open areas we recorded the number and cover of species as well air and soil temperature, relative humidity of the air, photosynthetic photon flux density (PPFD) and soil water content. We planted seedlings of Lithrea caustica, Quillaja saponaria, and Cryptocarya alba in both habitats using soils from open areas and from beneath Baccharis to distinguish their effects on seedling’s photochemical efficiency and survival.No woody species grew beneath B. paniculata. Air temperature was similar in both habitats, but soil temperature and PPFD were lower, and soil moisture was higher beneath shrubs. Seedling’s photochemical efficiency and survival were generally higher beneath canopies but were negatively affected by soil from beneath Baccharis shrubs.Our findings question the nurse role of B. paniculata in the Chilean matorral, emphasizing the need to consider other shrub species for restoration initiatives for central Chile. [ABSTRACT FROM AUTHOR]

In the present study, we aimed to demonstrate that allelopathic compounds from the cyanobacterium Phormidium sp. can induce the collapse of large populations of the cyanobacteria Microcystis aeruginosa Kützing Kützing. We employed several strains of this toxic cyanobacteria, from six different locations, in order to test for adaptive variation in resistance to allelochemicals. As a preliminary test to detect allelopathic effect, we performed bioassays with Phormidium allelochemicals against the different strains of M. aeruginosa at low population abundances. Then, we combined long-term competition experiments and mechanistic modelling with two purposes: (a) demonstrate that the inhibitory effect of Phormidium sp. against M. aeruginosa was due to allelopathy and not resource competition; (b) test the effectiveness of these allelochemicals at inducing the collapse of large populations of M. aeruginosa. Our results showed a strong allelopathic effect of Phormidium, which induced the collapse of large populations of M. aeruginosa, without evidence of differences in sensitivity between strains. We demonstrated that allelopathy (interference competition) can reverse the outcome predicted by resource competition (exploitation competition). These results are encouraging in order to take further steps in the development of a bioremediation method, based in Phormidium allelopathy, against blooms of toxic cyanobacteria. [ABSTRACT FROM AUTHOR]

It is now essential to reduce the negative impacts of weed management and especially herbicide use. Weed-suppressive crop species/varieties hold promise for integrated and sustainable weed regulation. Competition for resources and allelopathy are the two main underlying mechanisms. Unlike competition, which is well studied and established, allelopathy by living crops remains a contentious mechanism. A major difficulty to demonstrate the effects of allelopathy in the field is to dissociate them from those of competition. Here, we systematically and quantitatively review the literature, searching for field-based evidence of the role of allelopathy (by root exudation of living crops) in weed regulation, independently of competition, focusing on studies comparing different varieties of a given crop species. Our critical literature analysis also aims to identify weaknesses and strengths in methodology, providing insights on optimal experimental designs and avenues for future research. Our main conclusions are: (1) in most articles, the role of crop competition is disregarded or not exhaustively studied. Consequently, contrary to authors' conclusions, it cannot be determined whether weed regulation is due to allelopathy and/or to competition. (2) Few articles provided convincing evidence of the presence/absence of allelopathy in the field. (3) To further investigate allelopathy in the field we recommend to (i) finely characterize crop competition by measuring traits in the field, (ii) assess crop allelopathic potential with complementary experiments in controlled conditions or by quantifying allelochemicals in the field, and (iii) quantify the contribution of each studied trait/mechanism in explaining weed regulation in the field with multiple regression models. In conclusion, the consistent use of the suggested guidelines, as well as alternative approaches (e.g., creation of varieties with deactivated allelopathic functions, development of process-based simulation models), may provide a basis for quantifying the role of allelopathy in the field and, subsequently, for designing weed management strategies promoting weed biological regulation. [ABSTRACT FROM AUTHOR]

Background: The increasing demand for food production has led to a tenfold increase in nitrogen (N) fertilizer use since the Green Revolution. Nowadays, agricultural soils have been turned into high-nitrifying environments that increase N pollution. To decrease N losses, synthetic nitrification inhibitors (SNIs) such as 3,4-dimethylpyrazole phosphate (DMPP) have been developed. However, SNIs are not widely adopted by farmers due to their biologically limited stability and soil mobility. On the other hand, allelopathic substances from root exudates from crops such as sorghum are known for their activity as biological nitrification inhibitors (BNIs). These substances are released directly into the rhizosphere. Nevertheless, BNI exudation could be modified or even suppressed if crop development is affected. In this work, we compare the performance of biological (sorghum crop) and synthetic (DMPP) nitrification inhibitors in field conditions. Results: Sorghum crop BNIs and DMPP prevented an increase in the abundance of ammonia-oxidizing bacteria (AOB) without affecting the total bacterial abundance. Both nitrification inhibitors maintained similar soil NH4+ content, but at 30 days post-fertilization (DPF), the sorghum BNIs resulted in higher soil NO3− content than DMPP. Even so, these inhibitors managed to reduce 64% and 96%, respectively, of the NO3−-N/NH4+-N ratio compared to the control treatment. Similar to soil mineral N, there were no differences in leaf δ15N values between the two nitrification inhibitors, yet at 30 DPF, δ15N values from sorghum BNI were more positive than those of DMPP. N2O emissions from DMPP-treated soil were low throughout the experiment. Nevertheless, while sorghum BNIs also maintained low N2O emissions, they were associated with a substantial N2O emission peak at 3 DPF that lasted until 7 DPF. Conclusions: Our results indicate that while sorghum root exudates can reduce nitrification in field soil, even at the same efficiency as DMPP for a certain amount of time, they are not able to prevent the N pollution derived from N fertilization as DMPP does during the entire experiment. [ABSTRACT FROM AUTHOR]

Green tides have been increasing in frequency and severity in coastal areas in recent years, and thus, the adverse effects of green tides on the environment have attracted much research attention. Allelopathy is one of the most significant effects of green tide algae on the surrounding organisms. In this study, a series of experiments were developed to fully investigate the allelopathic effects of the green tide alga Ulva linza on two common coastal phytoplankton species and to isolate and identify the chemical compositions of the allelochemicals. Our results indicated that the fresh tissue, dry powder, and aqueous extracts all inhibited the population growth of the two experimental phytoplankton species, indicating the occurrence of allelopathy; further analysis of the allelochemicals identified multiple kinds of fatty acids as allelopathic compounds, in which the most abundant ones were hexadecanoic acid; 9Z, 12Z, 15Z-octadecatetrienoic acid; and 9E-octadecenoic acid. Our findings enrich the database for research on allelopathy between marine green tide algae and phytoplankton. Both algae and phytoplankton could increase their own competitive abilities during bloom formation, thereby changing the phytoplankton community structure. [ABSTRACT FROM AUTHOR]

Background and objectives: Integrated weed management in commercial wheat production is urgently needed due to increasing herbicide resistance and production costs. Benzoxazinoids (BXs), which include benzoxazinones and benzoxazolinones, are unique bioactive metabolites produced by certain members of the Poaceae including maize, wheat, rye and some dicots. BXs play important roles in plant defence and are causal agents of allelopathic interference. We investigated the role of genetics, environment and crop growth stage on BX abundance in the roots and rhizoplane of selected commercial wheat cultivars, and quantified their microbial transformation products (aminophenoxazinones) in roots and rhizosphere soils. Methods: Cultivar trials of competitive wheat (Triticum aestivum L.) genotypes were conducted in two moderate to low rainfall (449–572 mm) locations in southeastern Australia in 2015 and 2016. Replicated shoot, root, rhizoplane, and rhizosphere soil samples were collected for metabolic profiling at selected crop phenological stages, extracted and further analysed for known benzoxazinoid metabolites by liquid chromatography coupled with high resolution mass spectrometry. Results: Fifteen BXs and related microbially derived aminophenoxazinones were detected in wheat shoots, roots, rhizoplanes and rhizosphere soils in both years and locations. MBOA, HMBOA and HMBOA-Glc were the three most abundant BX metabolites in wheat tissues, with the heritage cultivar Federation producing the highest levels of MBOA. The phytotoxic aminophenoxazinones APO and AMPO were the most abundant BX microbial transformation products and were detected in wheat roots, rhizoplanes and rhizospheres. Abundance varied with cultivar, growth stage, location and year. Conclusions: Microbially-produced aminophenoxazinones generated from both heritage and modern wheat root exudates were detected and quantified in rhizosphere soils, with abundance dependent on cultivar, growth stage, and season. Concentrations of microbial metabolites APO, AMPO, and AAPO were higher in the rhizosphere of young wheat seedlings in contrast to that of mature plants suggesting that phenoxazinone production was upregulated early in the season. Our findings demonstrate that BX metabolites at all life stages of wheat potentially undergo rapid biotransformation to aminophenoxazinones under field conditions, resulting in ecologically relevant concentrations sufficient for weed suppression by certain wheat cultivars. [ABSTRACT FROM AUTHOR]

The current agricultural scenario faces a range of challenges, with phytosanitary ones being paramount. In most cases, plant diseases are treated with chemicals; however, they cause environmental pollution and face the acquired resistance of pathogens. Alternatively, biochar is a valuable tool for inducing the systemic resistance of plants since it is an effective and widely used resource to improve the physical, chemical, and biological attributes of the soil, consequently providing an adequate environment for healthy plant development. The effectiveness of the application of biochar in the control of plant diseases has been attributed to its alkaline pH, which contributes to the growth of beneficial microorganisms and increases the availability of nutrients, and to its porous structure, which provides a habitat and protection for the development of the soil microbiome. Therefore, the combined effect of improvements to soil attributes through biochar creates its role in controlling pathogens. This review assesses the beneficial and potential effects of biochar in agricultural soils, as well as showing the positive effects of biochar in the management of soil pathogens. Besides, we deeply evaluate twenty papers that used biochar as a strategy to manage plant diseases caused by pathogens inhabiting the soil in different soil-pathogen-plant systems. Among these studies, 70 % validate biochar as a strategy for the management of plant diseases; 10 % of studies showed that the efficiency of biochar as a disease management tool depends on the type of feedstock, and 20 % of studies describes that the biochar is not a management tool for suppressive diseases, caused by Pythium ultimum and Rhizoctonia solani in some host plants. The biochar is a strategy to manage plant diseases caused by pathogens inhabiting the soil, due different mechanisms as fungitoxic effect of biochar, sorption of allelopathic and phytotoxic compounds that can harm the plant, induction of plant resistance, increase of activities and abundance of beneficial microorganism's, changes in soil quality as nutrient availability and abiotic conditions. [ABSTRACT FROM AUTHOR]

Crop allelopathy is a useful tool in integrated weed suppression. Although the abiotic stresses affect the produced secondary metabolites, the impact of soil salinity on crop allelopathic potential under field conditions has not been investigated. So, the effect of soil salinity on the allelopathic activity of 18 allelopathic barley (Hordeum vulgare L.) varieties was investigated. The allelopathy of barley grown on saline and non-saline soils was investigated during a 2-year field experiment using the Perlite-based bioassay with rigid ryegrass (Lolium rigidum L.) as plant indicator. The two main allelopathic substances in barley, gramine and hordenine, were determined using the high-performance liquid chromatography with tandem mass spectrometry. The results indicated that rigid ryegrass germination and root length were adversely affected by the barley aqueous extracts. The secondary metabolite gramine was detected in greater concentrations than those of hordenine. For most barley varieties, soil salinity reduced the phytotoxicity of aqueous extracts, as well as the concentration of gramine. However, gramine and hordenine were not highly correlated with the barley extract phytotoxicity, indicating the possible involvement of other allelopathic substances. In conclusion, the barley allelopathic potential probably decreases in soils with high salinity. [ABSTRACT FROM AUTHOR]

Weeds have been a major threat in agriculture for several generations as they lead to decreases in productivity and cause significant economic losses. Parasitic plants are a specific type of weed causing losses in crops of great relevance. A new strategy has emerged in the fight against parasitic plants, which is called 'suicidal germination' or the 'honey-pot strategy'. Regarding the problem of weed control from an ecological point of view, it is interesting to investigate new natural compounds with allelopathic activity with the aim of developing new natural herbicides that can inhibit the growth of weeds without damaging the environment. Safflower crops have been affected by parasitic plants and weeds and, as a consequence, the secondary metabolites exuded by safflower roots have been studied. The sesquiterpene lactone dehydrocostuslactone was isolated and characterised, and the structurally related costunolide was identified by UHPLC-MS/MS in safflower root exudates. These sesquiterpene lactones have been shown to stimulate germination of Phelipanche ramosa and Orobanche cumana seeds. In addition, these compounds were phytotoxic on three important weeds in agriculture, namely Lolium perenne, Lolium rigidum and Echinochloa crus-galli. The exudation of the strigolactones solanacol and fabacyl acetate have also been confirmed by UHPLC-MS/MS. The study reported here contributes to our knowledge of the ecological role played by some secondary metabolites. Moreover, this knowledge could help identify new models for the development of future agrochemicals based on natural products. [ABSTRACT FROM AUTHOR]

The intensive application of agrochemicals in crops has negatively impacted the environment and other organisms. The use of naturally occurring compounds may be an alternative to mitigate these effects. Plants are secondary metabolite reservoirs and may present allelopathic activity, which is potentially interesting to be used in bioherbicide formulations. In this context, the present work aimed to evaluate the phytotoxic and cytotoxic effects of essential oils extracted from leaves of Sparattanthelium botocudorum and Sparattanthelium tupiniquinorum in bioassays with the plant models Lactuca sativa L. and Sorghum bicolor L. Moench. The essential oils were applied at concentrations of 3,000, 1,500, 750, 375 and 187.5 ppm. Chemical characterization of the oils was performed, and their impact on the percentage of germinated seeds, initial development of L. sativa and S. bicolor seedlings, and changes in the mitotic cycle of meristematic cells from L. sativa roots was evaluated. The major compound of the essential oils was germacrene D, followed by bicyclogermacrene, β-elemene and germacrene A. The phytotoxicity assay showed that the essential oils of both species reduced the root and shoot growth in L. sativa and decreased the germination and shoot growth in S. bicolor. Inhibition was dependent on the tested oil concentration. In the cytotoxicity assay, a decrease in mitotic index and chromosomal and nuclear alterations were observed, which resulted from aneugenic and clastogenic action. [ABSTRACT FROM AUTHOR]

Mikania micrantha and Ipomoea cairica are two invasive plants widely distribute and seriously damage in Hainan island. In this study, the leaves extracts of two weeds were collected and determined for their allelopathic potentials on Chrysanthemum coronarium. The phytotoxicity bioassay showed that when the extract concentration was 50 and 100 mg/ml, the inhibited effects of M. micrantha on growth of C. coronarium were greater than by I. cairica. However, when the extract concertation at 400 mg/ml, the opposite inhibited effects were observed. We speculated this phenomenon was caused by different allelopathic compounds. Therefore, using gas chromatography–mass spectrometry, 19 and 23 compounds were identified respectively, benzoic acid and cinnamic acid were the main components in the two leaves extracts, which were selected to carry out the further bioassays. Subsequent bioassay results showed the effects of two allelochemicals on morphological index and chlorophyll content and POD activity were all negative to C. coronarium, whereas the content of MDA and activity of SOD, CAT represented adverse changes. Moreover, the inhibitions by cinnamic acid were generally greater than those by benzoic acid. Thus, the phenolic acids played the most crucial roles in the allelopathic effccts of M. micrantha and I. cairica leaves extracts. [ABSTRACT FROM AUTHOR]

Under natural conditions, plants compete for environmental resources, including by the release of allelopathic compounds with a various spectrum of activity. Therefore, the effect of aqueous extracts of cock's-foot Dactylis glomerata L. on germination and early growth phases and electrolyte leakages of a red clover Trifolium pratense L. was investigated. The 5, 10, and 15% of the aqueous extracts of cock's-foot separately from shoots and inflorescences were used in two type of treatments tested in parallel. In first treatment the red clover seeds were watered directly with the aqueous extracts by eight days of experiment time, in second the seeds were pretreated with extracts for 24, 48 and 72 h and next they were watered with distilled water during experiment time. The results showed that the germination capacity of red clover seeds decreased with increasing concentrations of cock's-foot aqueous extracts. Regardless of the duration of seed treatment with the extracts, the highest inhibition of germination was found when the 15% cock's-foot shoot extracts was used. For red clover seedlings pretreated with extracts for 72 h, the highest and statistically significant differences in the growth were observed. With the increasing of concentration of cock's-foot extracts significant inhibition of the underground and aboveground organs growth were observed. The increase of fresh and dry masses of red clover seedlings varied depending on the duration of contact with the extracts and their concentrations. The electrolyte leakage, as compared to the control, increased with the concentration of extracts, regardless of types and duration of extracts. The obtained results clearly confirm that leaving biomass of cock's-foot on the field can lead to the release of phytotoxins that may inhibit germination and growth of red clover. [ABSTRACT FROM AUTHOR]

The composition of aromatic compounds in the liquid culture medium and the cells of the Rhizobium leguminosarum bv. viciae, Pseudomonas syringae pv. pisi, and Clavibacter michiganensis sps. sepedonicus bacteria grown in the presence of the negative allelopathic compound N-phenyl-2-naphthylamine (N-PNA) found in the root exudates of legume plants is analyzed. It is demonstrated that phthalates are the main products of N-PNA degradation. Bacteria can actively secrete them into the environment and convert phthalates of one type into other types by changing the alkyl groups linked to the o-phthalic acid via the ester bond in their molecules. The analyzed bacteria differed in the rate of N-PNA degradation (10 and 100 µM), which exerted different effects on their growth and viability. The proposed mechanisms could potentially be used to control the bacterial composition and number in the rhizosphere of legume plants with N-PNA and phthalates secreted by plant roots into the exudates, as well as the phthalates produced in the course of N-PNA degradation in the bacterial cells. [ABSTRACT FROM AUTHOR]

Background: It is well known that legume and other crops such as pea, faba bean, lentil, chick pea, and several other crops are susceptible to Orobanche crenata (broomrape) infestation. There is a direct relationship between O. crenata infestation and yield losses depending on the severity of infestation, the crop sensitivity, the planting date, and the different prevailing environmental factors. So, the present investigation aims to evaluate the allelopathic potentiality of the seed powder of the Brassicaceae plants (Eruca sativa and Sinapis alba) in controlling O. crenata infesting Pisum sativum plants. Materials/methods: Two greenhouse experiments were held during two consecutive winter seasons to study the allelopathic effect of Eruca sativa (Essp) and Sinapis alba (Sasp) seed powder and compare it with recommended Basamid (Dazomet) herbicide treatment in controlling O. crenata infesting Pisum sativum as well as their effect on P. sativum growth, yield, and yield attributes. The treatments were conducted by mixing the seed powder of E. sativa (Essp) or S. alba (Sasp) to the soil at 12.5, 25.0, 37.5, and 50 g/kg soil as well as Basamid herbicide at 0.2 g/pot. Results: The recorded results show that both Essp and Sasp at successive rates as well as Basamid treatment scored a great inhibition in dry weight of O. crenata tubercles infesting P. sativum plants at 55 days after sowing (DAS) and at harvest. The highest rate (50 g/kg) of both applied seed powder achieved the highest level of controlling O. crenata investigated weed. Growth as well as yield and yield attributes of P. sativum increased by the application of Essp and Sasp especially at the lowest rates in comparison with infected control. Conclusion: The lowest rates (12.5 and 25 g/kg soil) of both Essp and Sasp were the optimum applied treatments that suppressed O. crenata weed with the highest yield of P. sativum as compared with the healthy control. Glucosinolates and phenolic compounds in both seed powder may be the main active allelochemical which could be considered as a natural bioherbicide for controlling the O. crenata parasitic weed that infests P. sativum and reflected in turn on the plant yield by increase. [ABSTRACT FROM AUTHOR]

Background: Allelopathy is an alternative safe strategy for chemical herbicides in controlling weeds. So, two successive greenhouse experiments were conducted to determine the phytotoxicity of pea seed powder on two weeds chard- (broad leaf) and canary grass (grass weed)-infested wheat. Pea seed powder was added to the soil surface at successive rates 20, 40, 60, 80, and 100 g/pot. The pots were cultivated on time (at sowing application) or 1 week after the addition of the pea seed powder. Results: The results indicated that the pea seed powder at 100 g/pot controlled more than 70–80% of both weeds in comparison to the corresponding controls. On the other hand, the inhibitory effect of the pea seed powder on weeds was accompanied by increases in the growth as well as photosynthetic pigments content and consequently wheat yield especially at 80 g/pot. Conclusion: This study suggested that the pea seed powder has allelopathic and phytotoxic effects that controlled investigated weeds in wheat. Analysis of the allelopathic pea seed powder at the applied rates revealed the presence of phenolic compounds and flavonoids. Both allelopathic compounds showed high levels with increasing the pea seed powder rate. The mixing of pea seed powder with the soil surface at 80 g/pot 1 week before sowing was the most efficient treatment in controlling weeds under investigation that consequently achieved the highest wheat yield. [ABSTRACT FROM AUTHOR]

The deep-placement of nutrient-rich organic amendments in poorly-structured subsoils can improve subsoil structure and increase grain yields, but its widespread adoption by farmers is limited by the availability and cost of animal manures, the current choice of amendment. Three glasshouse experiments investigated the effectiveness of dried field pea (Pisum sativum L.) shoots (green chop), as green manure, on wheat growth in three subsoils with contrasting soil chemical and physical properties. The growth of wheat plants was greatly suppressed when the green chop was placed in Sodosol and Chromosol subsoils. In contrast, there was a twofold increase in shoot biomass in response to the addition of green chop to Vertosol. Three allelopathic compounds, pisatin, anhydropisatin, and maackian, were identified at higher concentrations in the extracts of remaining green chop residues in the Sodosol and Chromosol, compared to the Vertosol, directly supporting phytotoxicity as the cause of observed inhibitory effects of green chop in these soils. The persistence of the phytotoxicity in the Sodosol might be attributed to its poor aeration caused by poor structure or compaction. Nevertheless, pre-incubation led to microbial decomposition of the allelochemicals in the Sodosol, though at a much slower rate than in the Vertosol. Further studies are needed to determine the time period required for the disappearance of the phytotoxic effects in soils with different physico-chemical properties. [ABSTRACT FROM AUTHOR]

The use of allelopathic compounds is an alternative for weeds control, since they present low toxicity when compared with the synthetic herbicides, that may cause several damages, as the contamination of the environment. Our objective was to determine the chemical composition and allelopathic properties of the essential oils of Psidium cattleianum, P. myrtoides, P. friedrichsthalianum, and P. gaudichaudianum on the germination and root growth of Lactuca sativa and Sorghum bicolor, and to evaluate their action on the cell cycle of root meristematic cells of L. sativa. The main compound found in all the studied species was (E)-caryophyllene (P. cattleianum—23.4 %; P. myrtoides—19.3%; P. friedrichsthalianum—24.6% and P. gaudichaudianum—17.0%). The different essential oils were tested at different concentrations on L. sativa and S. bicolor, reducing germination, germination speed index, and root and shoot growth of lettuce and sorghum seedlings. The cytotoxicity and aneugenic potential of these oils were evidenced by the reduction of the mitotic index and increase of the frequency of chromosomal alterations in L. sativa. The essential oils of the species of Psidium studied have potential to be used in weeds control. [ABSTRACT FROM AUTHOR]

Allelopathic effects on the seed germination and seedling growth of the natives play a crucial role in the successful invasion of numerous invaders. Meanwhile, soil salinity is an emerging driver of the spread of many invaders, especially in the colonization of saline habitats. Thus, the allelopathic effects of the invaders on the seed germination and seedling growth of the natives may be altered or even reinforced under salt stress. This study aims to address the allelopathic effects of the notorious invader Canada goldenrod (Solidago canadensis L.; goldenrod hereafter) on the seed germination and seedling growth of the native lettuce (Lactuca sativa L.; lettuce hereafter) under a gradient of salt stress. Goldenrod leaf extracts with high concentration significantly decreased root length, leaf shape index, germination percentage, germination potential, germination index, germination vigor index, and germination rate index of lettuce. However, goldenrod leaf extracts with low concentration significantly increased root length and leaf width of lettuce. Goldenrod leaf extracts with high concentration display more serious allelopathic effects on the seed germination and seedling growth of lettuce than those with low concentration. Salt stress regardless of concentration significantly decreased seedling height, root length, leaf shape index, and seedling biomass (fresh weight) of lettuce. The combined goldenrod leaf extracts and salt stress have a synergistic effect on seedling height, root length, leaf shape index, germination percentage, germination potential, germination index, and germination rate index of lettuce. Thus, the allelopathic effects of the invaders on the seed germination and seedling growth of the natives may be reinforced under salt stress. Accordingly, salt stress may be beneficial to the further invasion of the invaders mainly via the reduced growth performance of the natives. [ABSTRACT FROM AUTHOR]

Cyperus alternifolius (C. alternifolius) and Canna generalis (C. generalis) are widely used as artificial floating-bed (AFB) plants for water pollution control. This study evaluated the release of anti-cyanobacterial allelochemicals from both plants in AFB systems. A series of cyanobacterial assays using pure culture solutions and extracts of culture solutions of C. alternifolius and C. generalis demonstrated allelopathic growth inhibition of a cyanobacterium M. aeruginosa. After 45 days of incubation by the culture solutions, both final inhibitory rates of M. aeruginosa were more than 99.6% compared with that of the control groups. GC/MS analyses indicated the presence of a total of 15 kinds of compounds, including fatty acids and phenolic compounds, in both plants' culture solutions, which are are anti-cyanobacterial. These findings provide a basis to apply artificial floating-bed plants for cyanobacterial inhibition using allelopathic effects. [ABSTRACT FROM AUTHOR]

The role of macroalgal allelopathy in aquatic systems has received increasing attention as a potential means of controlling cyanobacterial blooms. However, the allelopathic activity of Chara sp. on coexisting and bloom-forming picocyanobacteria is still largely unknown. Therefore, the laboratory experiments were conducted to investigate the allelopathic activity of extracts of Chara aspera, C. baltica, and C. canescens on the growth, the fluorescence parameters: maximum and effective quantum yield of photosystem II (PSII) photochemistry (Fv/Fm and ΦPSII, respectively) and photosynthesis parameters such as the initial slope of photosynthesis-irradiance (P-E) curves (alpha) and photosynthetic capacity (Pm) of the picocyanobacterium Synechococcus sp. Batch cultures of picocyanobacterium were exposed to three concentrations of extracts originating from three charophyte cultures and the effect was followed at three sampling times. Dried specimens of C. aspera, C. baltica, and C. canescens were extracted in the water-based matrix and the initial Synechococcus sp. inoculum, derived from unialgal culture media, was used. We found both negative and positive allelopathic effects of all tested Chara extracts on Synechococcus sp. The strongest adverse impact of picocyanobacterium growth was caused by C. baltica. This study clearly demonstrated that the allelopathic effect depends on the Chara species identity. Our results also suggested that some allelopathic Chara sp. have the potential to mitigate harmful cyanobacterial blooms in systems dominated by Synechococcus sp. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluated the influence of aqueous extracts from Galinsoga parviflora and Oxalis fontana on the germination capacity and energy of Raphanus sativus var. radicula in three cultivars: ‘Krakowianka’, ‘Półdługa’, ‘Rowa’. After eight days of germination, the length of seedlings, the fresh and dry mass, the percentage of water content and the degree of destabilisation of cells membranes by measuring the outflow of electrolytes were determined. The aqueous extracts from fresh mass of aboveground parts of G. parviflora and O. fontana with concentrations of 5, 10 and 15% were used. The control group consisted of seeds watered with distilled water. The germination capacity in all radish varieties decreased with increase in the concentration of G. parviflora and O. fontana aquatic extracts. The length of underground parts of seedlings was significantly shorter on Petri dishes with extracts from O. fontana. With increasing concentration of extracts, the length of aboveground parts of seedlings on O. fontana extracts decreased, and on G. parviflora increased. In the case of fresh and dry mass, the extracts stimulated the growth of seedlings, with the exception of the ‘Krakowianka’ cultivar on substrates with 5% extracts. At the lowest concentrations of the extracts, the smallest percentage of electrolyte leakage was observed. For all three types of radish watered with extracts from O. fontana higher destabilisation of cell membranes was observed. [ABSTRACT FROM AUTHOR]

Allelopathy is very important for the scientific disposition of garden plants. To understand the allelopathic potential of Koelreuteria bipinnata Franch. var. integrifoliola, the germination of Agrostis tenuis Sibth., Festuca arundinacea Schreb. and Lolium perenne L. were determined under laboratory conditions. The results showed that root, stem and leaf aqueous extracts of K. bipinnata var. integrifoliola had allelopathic effects on all three turf grasses, and the allelopathic activity varied according to extract concentrations, test species, and extract sources. Lower extract concentrations did not affect or promoted the germination and initial seedling growth of turf grasses, but the highest concentrations almost had inhibitory effect. The order of allelopathic potentials of the three organs on germination of these receptors was root < stem < leaf. And at the highest concentration of leaf extract, the most strongly inhibition was found in A. tenuis, followed by F. arundinaces and then L. perenne. In addition, according to gas chromatography-mass spectrometry (GC-MS) analysis, the allelopathic potential compounds and their abundance in root, stem and leaf were obviously different. Therefore, the allelopathic compounds may responsible for allelopathy of K. bipinnata var. integrifoliola. These findings suggested that more attention should be paid to the leaf of K. bipinnata var. integrifoliola for the relative higher allelopathic effects. [ABSTRACT FROM AUTHOR]

Eichhornia crassipes is an invasive, floating macrophyte and may have biocontrol functions on harmful cyanobacteria blooms. Eichhornia produces N-phenyl-2-naphthylamine (PNA), a compound which can inhibit algae. However, the impact of PNA on allelopathic effects of the cyanobacterium Microcystis aeruginosa on other phytoplankton species is not clear. In this study, we tested whether PNA can influence the allelopathic effect of M. aeruginosa on the green alga Scenedesmus quadricauda. S. quadricauda was more sensitive to PNA than M. aeruginosa, with 72 h-EC50 values of 0.42 and 3.66 mg L−1, respectively. In addition, PNA significantly enhanced allelopathy by M. aeruginosa on S. quadricauda. Consequently, PNA had a greater impact on the green algae when Microcystis was present. In complex ecosystems with multiple species that release allelopathic substances, unintended interspecific interactions may occur, where allelopathy plays an important role under artificial or even natural contexts. It is hard to predict the competition outcomes among allelopathic organisms in these complex ecosystems, therefore a precautionary approach is required for biological control of algae. [ABSTRACT FROM AUTHOR]

Allelopathic effects on the seed germination and seedling development of co-occurring native plant species (natives hereafter) are regarded as an important driver facilitating invasion of many invasive plant species (invaders hereafter). The release of silver nanoparticles (AgNPs) into the environment may affect the allelopathic effects of the invaders on the seed germination and seedling development of natives. This study aims to assess the allelopathic effects (using leaf extracts) of Canada goldenrod (Solidago canadensis L.) on the seed germination and seedling development of native lettuce (Lactuca sativa L.) treated with AgNPs with different particle sizes. Canada goldenrod leaf extracts with high concentration exhibit stronger allelopathic effects on the seedling height and root length of lettuce than those treated with low concentration. AgNPs of all particle sizes significantly decreased seed germination and seedling development indices of lettuce. AgNPs with larger particle sizes exerted stronger toxicity on leaf length and width of lettuce than those with smaller particle sizes. Thus, nanoparticles with larger particle sizes might mediate the production of increased sizes of cell wall pore size and large absorption of such substances by plant roots can be harmful. AgNPs significantly enhanced the allelopathic effects of Canada goldenrod on the seed germination and seedling development of lettuce. Small particle size AgNPs may play a more essential role in the enhanced allelopathic effects of low concentrations of Canada goldenrod leaf extracts; however, large particle size AgNPs may play a more important role in the enhanced allelopathic effects of high concentrations of Canada goldenrod leaf extracts. [ABSTRACT FROM AUTHOR]

Many plants release allelopathic chemicals that can inhibit germination, growth, and/or survival in neighboring plants. These impacts appear magnified with the invasion of some non-native plants which may produce allelochemicals against which native fauna have not co-evolved resistance. Our objective was to examine the potential allelopathic impact of an invasive non-native shrub/tree on multiple plant species using field observation and experimental allelopathy studies. We surveyed and collected an invasive, non-native tree/shrub ( Rhamnus cathartica) at Tifft Nature Preserve (a 107-ha urban natural area near Lake Erie in Buffalo, NY). We also surveyed understory plant communities in the urban forest to examine correlations between R. cathartica abundance and local plant community abundance and richness. We then used experimental mesocosms to test if patterns observed in the field could be explained by adding increased dosages of R. cathartica to soils containing five plant species, including native and non-native woody and herbaceous species. In the highly invaded urban forest, we found that herbaceous cover, shrubs and woody seedlings negatively covaried with R. cathartica basal area and seedlings density. In the mesocosm experiments, R. cathartica resulted in significant decreases in plant community species richness, abundance, and shifted biomass allocation from roots. Our results provide evidence that R. cathartica is highly allelopathic in its invaded range, that R. cathartica roots have an allelopathic effect and that some plant species appear immune. We suggest that these effects may explain the plant's ability to form dense monocultures and resist competitors, as well as shift community composition with species-specific impacts. [ABSTRACT FROM AUTHOR]

Massive growth of single species of cyanobacteria is a common phenomenon in many eutrophicated waters worldwide. Allelopathic growth control of phytoplankton species is one suggested mechanism, but still controversially discussed. The fact that the synthesis of biological active compounds requires high energy costs and carbon investment for a single cell in contrast to high dilution rates in natural systems questions the universal validity of allelopathic mechanisms, even more as high concentrations of allelopathic substances are often needed in several experiments to cause biological effects. In this study, it was tested, if growth inhibition is induced by chemical signaling alone or via direct cell-cell interaction. As a test system, we used a co-culture of the green algae Oocystis marsonii (Trebouxiophyceae) with the cyanobacterium Microcystis aeruginosa which is known to strongly reduce the growth of the green algal competitor. In this study, direct co-culturing as well as membrane-separated growth chambers were used to test for chemical and contact-mediated interactions. In the membrane-separated chambers, both species can be co-cultivated and a membrane allows the exchange of metabolites. Growth of O. marsonii was only affected in the direct co-cultivation situation, where direct cell-to-cell contact was possible. During direct co-cultivation, deviating cellular traits, namely cell cycle pattern and large cell-aggregate formation of both species, could be detected. These data strongly support the hypothesis of a direct cell-cell-contact necessary for allelopathic growth control in this model system. Such direct contact would allow targeting allelopathic metabolites directly towards the competitor and thereby minimizing dilution effects. [ABSTRACT FROM AUTHOR]

In spite of growing concerns about the invasion of the sun-coral Tubastraea coccinea along the tropical Southwestern Atlantic, the biological interactions mediating this species' establishment and spread are largely unknown. Here, we identified species associations with T. coccinea by comparing community structure between invaded and non-invaded areas at Búzios Island, SP, Brazil. We also investigated effects of chemical cues from representative benthic species on sun-coral larval performance in the laboratory and quantified the density of sun-coral recruits across different microhabitats in the field. Field surveys showed that the invasion of the sun-coral is more intense at reef areas of higher species richness and diversity, putting at risk a higher number of native species than anticipated and suggesting that local richness offers little resistance to invasion. Highest density of T. coccinea recruits observed on the least bioactive encrusting corallines suggests this taxonomic group may constitute doorways to the establishment of this coral. In contrast, field patterns of sun-coral colonies and recruits, as well as laboratory trials, suggest that cnidarian-dominated habitats represent obstacles to the sun-coral invasion. Thus, while areas dominated by the snowflake coral Carijoa riisei-which showed the greatest negative allelopathic effect on T. coccinea-likely provide resistance to the invader spreading, areas covered by encrusting coralline algae and 'barren substrates' probably facilitate its establishment. Because these latter, less-structured microhabitats often prevail after disturbance, damage assessment following human-mediated impacts should include detection and control of sun-coral populations. [ABSTRACT FROM AUTHOR]

Ailanthus altissima and Robinia pseudoacacia are two aggressive exotic tree species invading riparian ecosystems in Central Spain. We explored their allelopathic potentials as a possible mechanism explaining their success in these ecosystems. Specifically, we aimed (1) to compare the phytotoxic effects of the exotic and native ( Fraxinus angustifolia and Populus alba) trees on the fitness of several understory plants coexisting in riparian ecosystems, and (2) to assess the capacity of the riparian soil to modulate the phytotoxic effects. In laboratory bioassays, aqueous leaf litter extracts from the donor tree species at field-realistic concentrations were tested on different fitness indicators of 13 understory target species, using germination paper and soil as substrates in petri dishes. Using germination paper, we found species-specific effects between donor and target species, but the phytotoxicity of the exotic trees as a group was not greater than that of the natives. Nevertheless, the exotic R. pseudoacacia was the most effective donor species reducing the radicle growth of the target species. Over riparian soil substrate, the aqueous leaf litter extracts did not produce any phytotoxic effect on the target species, except in one case. Altogether, our results highlight the importance of using both a native control when assessing the phytotoxicity of nonnative plants and also the natural soil in the modulation of phytotoxic effects. Ignoring both factors in laboratory bioassays would have led to the overestimation of the phytotoxicity of the exotic species as a mechanism contributing to their invasion success. [ABSTRACT FROM AUTHOR]

While both plant-soil feedbacks and allelochemical interactions are key drivers of plant community dynamics, the potential for these two drivers to interact with each other remains largely unexplored. If soil microbes influence allelochemical production, this would represent a novel dimension of heterogeneity in plant-soil feedbacks. To explore the linkage between soil microbial communities and plant chemistry, we experimentally generated soil microbial communities and evaluated their impact on leaf chemical composition and allelopathic potential. Four native perennial old-field species (two each of Aster and Solidago) were grown in pairwise combination with each species' soil microbial community as well as a sterilized inoculum. We demonstrated unequivocally that variation in soil microbial communities altered leaf chemical fingerprints for all focal plant species and also changed their allelopathic potential. Soil microbes reduced allelopathic potential in bioassays by increasing germination 25-54% relative to sterile control soils in all four species. Plants grown with their own microbial communities had the lowest allelopathic potential, suggesting that allelochemical production may be lessened when growing with microbes from conspecifics. The allelopathic potential of plants grown in congener and confamilial soils was indistinguishable from each other, indicating an equivalent response to all non-conspecific microbial communities within these closely related genera. Our results clearly demonstrated that soil microbial communities cause changes in leaf tissue chemistry that altered their allelopathic properties. These findings represent a new mechanism of plant-soil feedbacks that may structure perennial plant communities over very small spatial scales that must be explored in much more detail. [ABSTRACT FROM AUTHOR]

The increased occurrence of harmful cyanobacterial species and, with this, higher frequency of cyanobacteria blooms, closely associated with eutrophication and climate change, have attracted increasing attention worldwide. However, competition mechanisms between the different bloom-forming cyanobacteria species remain to be elucidated. In this paper, for the first time, the allelopathic effect of the cyanobacterium Chrysosporum ovalisporum on the cyanobacterium Microcystis panniformis is reported. The results of our study conducted in a Chinese shallow coastal water body demonstrated that the biomass of M. panniformis was relatively low during the C. ovalisporum blooming period. Co-cultivation of a C. ovalisporum strain with a M. panniformis strain showed strong inhibition of the growth of M. panniformis but stimulation of C. ovalisporum. Thus, filtrate of C. ovalisporum culture had a strong inhibitory effect on the performance of M. panniformis by decreasing the maximum optical quantum yield ( F / F ), the electron transport rate (ETR) of PS II and the onset of light saturation ( I ) and by increasing the alkaline phosphatase (ALP) activity and superoxide dismutase (SOD) activity of M. panniformis. Our results suggest that the inter-specific allelopathic effect plays an important role in the competition between different cyanobacteria species. We foresee the importance of C. ovalisporum to intensify in a future warmer world, not least in small- to medium-sized, warm and high conductivity coastal water bodies. [ABSTRACT FROM AUTHOR]

An effective, environmentally friendly, and eco-sustainable approach for removing harmful microalgae is exploiting the allelopathic potential of aquatic macrophytes. In this study, we simulated field pollution conditions in the laboratory to investigate algal inhibition by allelochemicals, thereby providing insights into field practices. We tested five allelochemicals, i.e., coumarin, ρ-hydroxybenzoic acid, protocatechuic acid, stearic acid, and ρ-aminobenzenesulfonic acid, and a typical green alga, Chlorella pyrenoidosa, under two conditions. In the unpolluted treatment, individual allelochemicals had strong algal inhibition effects, where coumarin and ρ-hydroxybenzoic acid had greater potential for algal inhibition than protocatechuic acid, stearic acid, and ρ-aminobenzenesulfonic acid based on the 50 % inhibitory concentration. However, when two or three allelochemicals were mixed in specific proportions, the algal inhibition rate exceeded 80 %, thereby indicating allelopathic synergistic interactions. Mixtures of four or five allelochemicals had weak effects on algal inhibition, which indicated antagonistic interactions. Furthermore, the presence of low lead pollution significantly reduced the antialgal potential of individual allelochemicals, whereas the allelopathic synergistic interactions with mixtures between two or three allelochemicals were changed into antagonistic effects by low pollution. In particular, the allelopathic antagonistic interactions between four or five allelochemicals were increased by pollution. The allelopathic performance of these five allelochemicals may depend on various factors, such as the chemical species, mixture parameters, and algal strain. Thus, we found that low level pollution reduced the allelopathic inhibition of microalgae by allelochemicals. Therefore, the control of algae by the direct addition of allelochemicals should consider various environmental factors. [ABSTRACT FROM AUTHOR]

Background and aims: Belowground competition and allelopathic interference of neighbouring plants play important roles in shaping plant performance. We assessed the effect of belowground interactions involving root competition, root exudates and ectomycorrhizal (ECM) association between Kalmia and black spruce on above- and belowground biomass increment and foliar nutrient content of black spruce seedlings. We predicted that root competition and root exudates of Kalmia would exert a negative impact on black spruce performance, while ECM in black spruce would exert positive impacts on its performance. Methods: In a greenhouse experiment, using the neutral growth medium of peat-vermiculite, we planted Kalmia and black spruce seedling in pairs. We controlled root competition by placing fine wire mesh between the seedlings and applied benomyl fungicide to control ectomycorrhizae. We used activated charcoal to neutralize the potential allelopathic effects associated with root exudates. After 8 months, we evaluated the performance of black spruce seedlings in terms of biomass, abundance of ectomycorrhizal short roots and foliar nutrient concentrations. To determine treatment effects on soil processes, we also analysed soil pH, total phenols, C:N ratio and bioavailable nitrogen (NO− and NH+) at the end of the experiment. Results: We found a significant effect of root competition on root-shoot ratio and biomass increment in black spruce seedlings, which achieved the highest root-shoot ratio and biomass increment when major root competition was controlled. Kalmia produced twice the root biomass than black spruce. Surprisingly, charcoal and benomyl treatments-which remove the effects of Kalmia allelopathy on black spruce and suppress ECM growth, respectively-had little or no significant effect on overall biomass of black spruce. In contrast, Kalmia biomass increment and root-shoot ratio were maximized in benomyl treatment. Soil pH and C:N ratio were significantly higher in free competition than root exclusion and benomyl treatments and with activated charcoal. Conclusions: Kalmia root competition mediated by high root biomass is the predominant driver shaping neighbourhood interactions between Kalmia and black spruce, which in turn shape the performance of black spruce seedlings. Root exudates of Kalmia have a very weak effect on black spruce seedling growth. [ABSTRACT FROM AUTHOR]

A large number of human diseases are caused by nonsense mutations. These mutations result in premature protein termination and the expression of truncated, usually nonfunctional products. A promising therapeutic strategy for patients suffering from premature termination codon (PTC)-mediated disorders is to suppress the nonsense mutation and restore the expression of the affected protein. Such a suppression approach using specific antibiotics and other read-through promoting agents has been shown to suppress PTCs and restore the production of several important proteins. Here, we report the establishment of a novel, rapid, and very efficient method for screening stop-codon read-through agents. We also show that, in both mammalian cells and in a transgenic mouse model, distinct members of the macrolide antibiotic family can induce read-through of disease-causing stop codons leading to re-expression of several key proteins and to reduced disease phenotypes. Taken together, our results may help in the identification and characterization of well-needed customized pharmaceutical PTC suppression agents. Key messages: [ABSTRACT FROM AUTHOR]

Little research has been conducted on the occurrence of pharmaceuticals and personal care products (PPCPs) in the marine environment despite being increasingly impacted by these contaminants. This article reviews data on the occurrence of PPCPs in seawater, sediment, and organisms in the marine environment. Data pertaining to 196 pharmaceuticals and 37 personal care products reported from more than 50 marine sites are analyzed while taking sampling strategies and analytical methods into account. Particular attention is focused on the most frequently detected substances at highest concentrations. A snapshot of the most impacted marine sites is provided by comparing the highest concentrations reported for quantified substances. The present review reveals that: (i) PPCPs are widespread in seawater, particularly at sites impacted by anthropogenic activities, and (ii) the most frequently investigated and detected molecules in seawater and sediments are antibiotics, such as erythromycin. Moreover, this review points out other PPCPs of concern, such as ultraviolet filters, and underlines the scarcity of data on those substances despite recent evidence on their occurrence in marine organisms. The exposure of marine organisms in regard to these insufficient data is discussed. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) in wastewater can be characterized using fluorescence excitation-emission matrix and parallel factor (EEM-PARAFAC) analysis. Wastewater from animal farms or pharmaceutical plants usually contains high concentration of antibiotics. In this study, the quenching effect of antibiotics on the typical components of DOM was explored using fluorescence EEM-PARAFAC analysis. Four antibiotics (roxarsone, sulfaquinoxaline sodium, oxytetracycline, and erythromycin) at the concentration of 0.5∼4.0 mg/L and three typical components of DOM (tyrosine, tryptophan, and humic acid) were selected. Fluorescence quenching effects were observed with the addition of antibiotics. Among these four antibiotics, roxarsone (2.9∼20.2 %), sulfaquinoxaline sodium (0∼32.0 %), and oxytetracycline (0∼41.8 %) led to a stronger quenching effect than erythromycin (0∼8.0 %). From the side of DOM, tyrosine and tryptophan (0.5∼41.8 %) exhibited a similar quenching effect, but they were higher than humic acids (0∼20.2 %) at the same concentration of antibiotics. For humic acid, a significant quenching effect was observed only with the addition of roxarsone. This might be the first report about the fluorescence quenching effect caused by antibiotics. The results from this study confirmed the interference of antibiotics on the fluorescence intensity of the main components of DOM and highlighted the importance of correcting fluorescence data in the wastewater containing antibiotics. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) is an abundantly produced low-molecular-weight (LMW) thiol in many organisms. However, a number of Gram-positive bacteria do not produce GSH, but instead produce bacillithiol (BSH) as one of the major LMW thiols. Similar to GSH, studies have found that BSH has various roles in the cell, including protection against hydrogen peroxide, hypochlorite and disulfide stress. BSH also participates in the detoxification of thiol-reactive antibiotics and the electrophilic metabolite methylglyoxal. Recently, a number of studies have highlighted additional roles for BSH in the processing of intracellular metals. Herein, we examine the potential functions of BSH in the biogenesis of Fe-S clusters, cytosolic metal buffering and the prevention of metal intoxication. [ABSTRACT FROM AUTHOR]

This study aims to establish molecular modeling methods for predicting the liver and kidney uptakes of Tc-99m labeled quinolone antibiotics. Some three-dimensional quantitative-activity relationships (3D-QSAR) models were developed using comparative molecular field analysis and grid-independent descriptors procedures. As a first report on 3D-QSAR modeling, the predicted liver and kidney uptakes for quinolone antibiotics were in good agreement with the experimental values. The obtained results confirm the importance of hydrophobic interactions, size and steric hindrance of antibiotic molecules in their liver uptakes, while the electrostatic interactions and hydrogen bonding ability have impressive effects on their kidney uptakes. [ABSTRACT FROM AUTHOR]

Background: Controlling weeds through allelopathy is one strategy to reduce dependency on synthetic herbicides. The plant shoots of the grass Brachiaria brizantha incorporated into the field soil were found to inhibit the growth of several plant species. We investigated the variations of allelopathic activity and allelopathic substances in B. brizantha harvested in June, October and January. Results: All extracts of B. brizantha obtained from June, October and January inhibited the root and shoot growth of cress, lettuce, Phleum pretense and Lolium multiflorum in a concentration dependent manner. However, the inhibitory activity of B. brizantha of June and October was greater than that of B. brizantha of January. Concentrations of three potent allelopathic active substances, ( 6R,9S)-3-oxo-α-ionol, ( 6R,9R)-3-oxo-α-ionol and 4-ketopinoresinol were also greater in B. brizantha of June and October than those in B. brizantha of January. Conclusion: The results suggest that the allelopathic activity and the levels of those allelopathic active substances are greater in B. brizantha of June and October than those in B. brizantha of January. It is possible that B. brizantha could be useful for a weed suppressive residue or soil additive materials in the variety of agricultural settings to develop sustainable agriculture options. The effectiveness of B. brizantha of June and October as a weed suppressive agent may be greater than that of January. [ABSTRACT FROM AUTHOR]

Algae control by using allelochemicals secreted from plants is a safe and novel biological algal inhibiting technology. In this work, Hydrilla verticillata was cultivated with algae in coexisting systems, and its possible inhibitory effect and mechanism on planktonic algae were studied in eutrophic water. The results showed that 12 g L H. verticillata under nutrient sufficient conditions had an allelopathic inhibitory effect on planktonic algae at initial concentrations of 10, 10 and 10 cells mL, with an inhibitory ratio of 25.75, 38.49, and 58.17, respectively. H. verticillata played a role of 'promoting with low biomass while inhibiting with high biomass' on planktonic algae. The optimal biomass of H. verticillata for the growth inhibition of planktonic algae at initial concentration of 10 cells mL was 12 g L. H. verticillata produced possible inhibitory effects on Ankistrodesmus spirali, Closterium sp. , Ankistrodesmus angustus, Dactylococcopsis sp. and Microcystis aeruginosa of planktonic algae. The possible inhibitory effects shown in descending order were as A. spirali > Closterium sp. > A. angustus > Dactylococcopsis sp. > M. aeruginosa. However, little effect could be observed on Ankistrodesmus falcatus and Tetrasporales sp. It is predicted that allelochemicals of H. verticillata with algal inhibiting effect were as follows: compounds of lipid, acid, hexanol, amide and ketone. [ABSTRACT FROM AUTHOR]

Potentiometric sensors based on ion associates of Cefalexin, Cefuroxime, and Cefixime with tetraalkylammonium cations are developed. The sensors ensure the determination of cephalosporin antibiotics in a wide analytical range of 1 × 10 (1 × 10) to 1 × 10 (0.1) M; the values of c ∼ n × 10 (10) M. The sensors can be used for the determination of cephalosporins in biological fluids for the adjustment and optimization of treatment and for determining the main substance in pharmaceuticals. [ABSTRACT FROM AUTHOR]