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Alfalfa (Medicago sativa) is known to release allelopathic substances to affect the germination and growth of other plants, which have the potential to be applied in controlling weeds. Green foxtail (Setaria viridis) and barnyardgrass (Echinochloa crus-galli), as malignant weeds worldwide, also pose a serious threat to alfalfa in northern China. In this study, the sensitivity of the two weeds to the extracts from the first, second, and third stubbles of six varieties were investigated to further reveal the allelopathic interference of different varieties of alfalfa on notorious weeds. The germination rate, the length and fresh weight of seedlings, the length and fresh weight of roots were measured to elucidate the allelopathy of alfalfa extracts on the two weeds. The results suggested that: (1) The allelopathy of six alfalfa varieties tested showed obvious intraspecific differences, the inhibition of Zhongmu No.3 on green foxtail and barnyardgrass was weaker than other varieties, with the values of synthetical allelopathic effect (SAE) were -0.55 and -0.29, respectively. (2) The inhibitory effect of alfalfa extracts on green foxtail was enhanced with the increase of stubbles, while the differences between three stubbles on barnyardgrass were not clear, especially between the first and second stubbles. (3) Compared with barnyardgrass (SAE = -0.39 ~ -0.29), green foxtail (SAE = -0.65 ~ -0.52) was generally more susceptible to the extracts. (4) The inhibitory effect of alfalfa extracts on root was stronger than seedling in the same weed. For example, the third stubble extracts of Baoding variety inhibited 88.00% of the roots at the concentration of 0.01 g mL-1, but did not affect the seedlings of green foxtail. The study may help to comprehensively reveal the allelopathic effect of different alfalfa varieties in the first three stubbles on green foxtail and barnyardgrass, providing scientific evidence for weed control based on natural plant extracts in the future. [ABSTRACT FROM AUTHOR]

One-month-old lettuce seedlings were planted in the field with and without prior hairy vetch (Vicia villosa L.) incorporation (HV and Fallow, respectively). The periods between hairy vetch incorporation and lettuce planting were 1 day, 8 days and 15 days. The inorganic nitrogen concentration in the soil was higher after hairy vetch incorporation, as well as the nitrogen concentration in the lettuce leaves from the HV plot compared to the Fallow plot, at any planting period. When lettuce seedlings were planted 8 days after hairy vetch incorporation, the leaf dry weight in the HV plots was 11% lower than that in the Fallow plots 4 days after planting; however, leaf growth recovered and the dry weight was 24% higher 12 days after planting, which could be due to enhanced leaf growth as the result of additional accumulated nitrogen provided by the hairy vetch. In the incubation experiment, it was suggested that the inhibitory effect of hairy vetch decomposition was not due to allelopathic substances. Therefore, in the hairy-vetch-incorporated field, growth suppression in the lettuce plants occurred early and continued for a short period after hairy vetch incorporation, but the damage due to the growth suppression effect was minor. More importantly, nitrogen supplied from the hairy vetch promoted lettuce growth after the inhibition period. [ABSTRACT FROM AUTHOR]

Ageratum conyzoides L. is native to Tropical America, and it has naturalized in many other tropical, subtropical, and temperate countries in South America, Central and Southern Africa, South and East Asia, Eastern Austria, and Europe. The population of the species has increased dramatically as an invasive alien species, and it causes significant problems in agriculture and natural ecosystems. The life history traits of Ageratum conyzoides, such as its short life cycle, early reproductive maturity, prolific seed production, and high adaptive ability to various environmental conditions, may contribute to its naturalization and increasing population. Possible evidence of the molecules involved in the defense of Ageratum conyzoides against its natural enemies, such as herbivore insects and fungal pathogens, and the allelochemicals involved in its competitive ability against neighboring plant species has been accumulated in the literature. The volatiles, essential oils, extracts, residues, and/or rhizosphere soil of Ageratum conyzoides show insecticidal, fungicidal, nematocidal, and allelopathic activity. The pyrrolizidine alkaloids lycopsamine and echinatine, found in the species, are highly toxic and show insecticidal activity. Benzopyran derivatives precocenes I and II show inhibitory activity against insect juvenile hormone biosynthesis and trichothecene mycotoxin biosynthesis. A mixture of volatiles emitted from Ageratum conyzoides, such as β-caryophyllene, β-bisabolene, and β-farnesene, may work as herbivore-induced plant volatiles, which are involved in the indirect defense function against herbivore insects. Flavonoids, such as nobiletin, eupalestin, 5′-methoxynobiletin, 5,6,7,3′,4′,5′-hexamethoxyflavone, and 5,6,8,3,4′,5′-hexamethoxyflavone, show inhibitory activity against the spore germination of pathogenic fungi. The benzoic acid and cinnamic acid derivatives found in the species, such as protocatechuic acid, gallic acid, p-coumaric acid, p-hydroxybenzoic acid, and ferulic acid, may act as allelopathic agents, causing the germination and growth inhibition of competitive plant species. These molecules produced by Ageratum conyzoides may act as defense molecules against its natural enemies and as allelochemicals against neighboring plant species, and they may contribute to the naturalization of the increasing population of Ageratum conyzoides in new habitats as an invasive plant species. This article presents the first review focusing on the defense function and allelopathy of Ageratum conyzoides. [ABSTRACT FROM AUTHOR]

Human population growth constantly requires an increase in the production of food and products from the timber industry. To meet this demand, agriculture and planted forests are advancing over natural areas. In view of this, it is necessary to know the effects of land use for different purposes (grain production, pastures, planted forests, fruit production and among other uses) on the genetic diversity of populations of native species. This knowledge can assist in land use planning as well as in the development of conservation strategies for native species. In this study, we evaluated the effect of land use for agriculture (mainly for cereal production) and planted forests on the genetic diversity of Baccharis crispa Spreng. a herb native to South America. To achieve our goals, we compared population genetic data obtained with three molecular markers (microsatellites, inter-simple sequence repeat and isoenzymes) with data on land use for agriculture and planted forests from 15 different locations. Our results showed that regardless of the molecular marker used, the greater the use of land for agriculture and planted forests, the lower was the genetic diversity of B. crispa populations. Baccharis crispa is a semi-perennial species that needs at least one year to reach its reproductive period, which is prevented in agricultural areas due to the land being turned over or dissected with herbicides every 6 months. In the studied regions, the planted forests are of eucalypt and/or pine, which besides being species with a high production of allelopathic substances, produce strong shading and B. crispa is a species that inhabits open grassland that needs a high incidence of sunlight for development. The data obtained in our study can assist in the decision-making to use land in order to reconcile the production of supplies for humanity and for the conservation of nature. [ABSTRACT FROM AUTHOR]

Digera muricata Mart, a plant having therapeutic characteristics that has been utilised traditionally, belongs to the Amaranthaceae family, and a promising source of specific natural products utilized as antioxidant, prophylactic, antimicrobial, anthelmintic, anti-diabetic, and allelopathic agent. In the present study, a biologically active phytosterol was isolated from Digera muricata Mart. The isolated compound was characterized by 13C, 1H NMR, FTIR, and HRMS. Characterization of the isolate was done by antimicrobial assay, and molecular docking. The antimicrobial potential of the isolated phytosterol (50 µl) against Streptococcus pyogenes was found to be maximum (ZOI-20.0 ± 1.0), followed by Streptococcus agalactiae (ZOI-11.3±1.5), Candida albicans (ZOI-09.0 ± 1.0), Klebsiella pneumonia (ZOI-8.6 ± 1.5) and Escherichia coli (ZOI-8.6 ± 1.5). The molecular docking results indicate that the phytosterol binds to the receptor 1AI9 at the 32th and 58th positions; 1KZN receptor at the 76th position, the 5L3J receptor at the 46th (ASN) and 136th (ARG) position; 7WIJ receptor at the 419th (ARG) and 582th (ASP) and 585th (ASN) positions. [ABSTRACT FROM AUTHOR]

Biological invasions by alien and range-expanding native plant species can suppress native plants through allelopathy. However, the homeland security hypothesis suggests that some native plants can resist invasion by producing allelopathic compounds that inhibit the growth of invasive plants. Most research has focused on allelopathic interactions between individual native and invasive plant species, with less emphasis on how allelopathy helps entire native communities resist invasions. Additionally, limited knowledge exists about allelopathic interactions between range-expanding native species and recipient native communities, and their influence on invasion success. To bridge this knowledge gap, we conducted two greenhouse competition experiments to test reciprocal allelopathic effects between a native woody range-expanding species, Betula fruticosa , and a community of four native herbaceous species (Sanguisorba officinalis , Gentiana manshurica , Sium suave and Deyeuxia angustifolia) in China. We assessed whether B. fruticosa and the native community differed in their competitive effects and responses, and whether these were influenced by activated carbon, which neutralizes allelochemicals in the soil. Activated carbon reduced the suppressive effects of the native community on the above-ground biomass of B. fruticosa , which indicates that the native community exerted a strong allelopathic effect on B. fruticosa. In contrast, activated carbon only marginally enhanced the suppressive effects of B. fruticosa on the native community, which indicates that allelopathy is not the primary mechanism by which B. fruticosa exerts its suppression. Overall, these findings support the homeland security hypothesis and suggest that biotic resistance from the native herbaceous community may limit the invasion success of the woody range-expander B. fruticosa. [ABSTRACT FROM AUTHOR]

The document explores the concept of allelopathy, which involves the release of organic molecules by plants and microorganisms to inhibit or stimulate the growth of neighboring plants and microorganisms. It discusses the potential applications of allelopathy in regenerative agriculture, particularly in integrated weed control in organic farming. The document highlights the need for further research to identify new allelopathic plants, study their effects on crop rotations, and understand the interactions between allelochemicals and pathogens. The special issue compiles research articles on various aspects of allelopathy, emphasizing the importance of sustainable agricultural practices and environmental protection. [Extracted from the article]

A suite of plant traits is thought to make weed populations highly invasive, including vigorous growth and reproduction, superior competitive ability, and high dispersal ability. Using a breeding design and a common garden experiment, we tested whether such an "invasion syndrome" has evolved in an invasive range of Solidago altissima, and whether the evolution is likely to be genetically constrained. We found an overall shift in invasive phenotypes between native North American and invasive Japanese populations. The invasive populations were taller and produced more leaves, suggesting a superior ability to exploit limited resources. The populations also produced more allelopathic compounds that can suppress competitor growth. Finally, invasive populations produced more seeds, which are smaller and are released from a greater height, indicating a potential for superior dispersal ability than the native populations. Quantitative genetics analyses found a large amount of additive genetic variation in most focal traits across native and invasive populations, with no systematic differences in its magnitude between the ranges. Genetic covariances among three traits representing invasion strategies (leaf mass, polyacetylene concentration and seed size) were small. The R metric, which measures the effect of genetic covariances on the rate of adaptation, indicated that the covariance neither constrains nor accelerates concerted evolution of these traits. The results suggest that the invasion syndrome in S. altissima has evolved in the novel range due to ample additive genetic variation, and relatively free from genetic trade‐offs. [ABSTRACT FROM AUTHOR]

Simple Summary: The spread of large green algae in oceans causes green tides, particularly in the South Yellow Sea of China, where Ulva prolifera has led to the world's largest green tide events. This review looks at how allelopathy, a process where plants release chemicals to affect the growth and development of other plants, influences green tide dynamics. We focus on four main types of these allelochemicals—fatty acids, aldehydes, phenols, and terpenes—explaining how they influence the algae's growth and behavior. We also discuss new methods for quickly detecting these allelochemicals and how these methods can help monitor green tides. By combining allelochemical detection with advanced technologies like satellite observations and environmental DNA analysis, we can better understand and manage green tides. The proliferation of large green macroalgae in marine environments has led to the occurrence of green tides, particularly in the South Yellow Sea region of China, where Ulva prolifera has been identified as the primary species responsible for the world's largest green tide events. Allelopathy among plants is a critical factor influencing the dynamics of green tides. This review synthesizes previous research on allelopathic interactions within green tides, categorizing four extensively studied allelochemicals: fatty acids, aldehydes, phenols, and terpenes. The mechanisms by which these compounds regulate the physiological processes of green tide algae are examined in depth. Additionally, recent advancements in the rapid detection of allelochemicals are summarized, and their potential applications in monitoring green tide events are discussed. The integration of advanced monitoring technologies, such as satellite observation and environmental DNA (eDNA) analysis, with allelopathic substance detection is also explored. This combined approach addresses gaps in understanding the dynamic processes of green tide formation and provides a more comprehensive insight into the mechanisms driving these phenomena. The findings and new perspectives presented in this review aim to offer valuable insights and inspiration for researchers and policymakers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Education & Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The plant Curcuma longa L. is rich in bioactive compounds. However, there are few available studies that have investigated its allelopathic activity. In this work, we sought to preliminarily investigate the main chemical groups with allelopathic and bioherbicide activity present in the aqueous extract obtained from the rhizomes of C. longa, as well as its effect on the germination and initial growth of lettuce (Lactuca sativa L.) and wheat (Triticum aestivum L.) seedlings. Phytochemical analysis was performed using precipitation and colorimetric techniques. To determine the allelopathic potential of the extract, seven concentrations (1 to 64 g L-1 ) were tested, in addition to two control groups: distilled water (negative control) and glyphosate (positive control). The seeds remained in contact with the different concentrations for 72 hours. The evaluated parameters were: germination percentage (GP), germination speed index (GSI), root and shoot length of the seedlings, and median inhibitory concentration (IC50). Four compounds with allelopathic potential were identified: alkaloids, steroids, flavonoids, and terpenes. The results of the biological assay revealed that the aqueous extract had a limited impact on GP, showing effects only at the highest concentration (64 g L-1 ), causing a reduction of 20.70% in this parameter in both species. Additionally, it was found that the germination speed index (GSI) was significantly influenced by concentrations higher than 4 g L-1 for both species. The length of the root and shoot of the seedlings decreased with increasing doses. Shoot length was the most sensitive parameter, with an IC50 of 3.73 and 7.20 g L-1 required for wheat and lettuce, respectively. The results suggest that the extract of this plant has potential for the production of postemergence bioherbicides. [ABSTRACT FROM AUTHOR]

Plant extracts with allelopathic activity and their related compounds have been investigated for a long time as an eco-friendly approach to sustainable weed management. Croton oblongifolius (Roxb.) is a traditional medicinal plant valued for its diverse source of bioactive compounds that have been used to treat various diseases. C. oblongifolius leaf extract was previously described to involve a number of allelochemicals. Therefore, we conducted this research to explore more of the allelochemicals in the leaves of C. oblongifolius. The leaf extracts showed significant inhibitory activity against two test plants, Lolium multiflorum (monocot) and Medicago sativa (dicot). The bioassay-directed chromatographic purification of the leaf extracts yielded three compounds, including one novel compound, identified using spectral data, as follows: (1) alpinolide peroxide, (2) 6-hydroxy alpinolide, and (3) 3-hydroxy-5-isopropyl-3-methyl-2,3-dihydro-1H-inden-1-one (a novel sesquiterpene). These compounds considerably limited the growth of L. sativum. The compound concentrations affecting a 50% growth limitation (IC50) of L. sativum varied from 0.16 to 0.34 mM. Therefore, these characterized compounds may be allelopathic agents that cause the allelopathy of C. oblongifolius. [ABSTRACT FROM AUTHOR]

A key question in plant invasion biology is why invasive plants are more competitive in their introduced habitat than in their native habitat. Studies show that invasive species exhibit allelopathy, influencing other plants by releasing chemicals. Research on allelopathy uses in vitro tests, investigating effects on seed germination and seedling development. Although soil plays a role in modifying allelopathic effects, observations with soil are rare and almost nothing is known about the root development of test plants developing in soil and the effects of allelopathic compounds on root architecture. Our study evaluates the allelopathic effects of false indigo-bush (Amorpha fruticosa L.) and common milkweed (Asclepias syriaca L.) on oilseed rape growth as a model plant. The rhizotron system was used to study the effect of morphology and root architecture. Leaf–soil mixtures at 0.5%, 1%, and 5% concentrations were used. Shoot and root development was strongly inhibited at 5%. But there was no difference between the allelopathy of the two species, and the application of lower concentrations did not show any effect, demonstrating that soil has a significant modifying effect on their allelopathy. Our results highlight that the development of roots growing in the soil is also worth investigating in connection with allelopathy, which can strengthen the ecological importance of allelochemicals during successful invasions. [ABSTRACT FROM AUTHOR]

When facilitating other species and sustaining plant community structures and biodiversity, alpine cushion plants simultaneously experience negative feedback effects from surrounding vegetation. However, the impact of surrounding vegetation on cushion dynamics remains poorly understood, particularly in terms of allelopathic potentials. To investigate the allelopathic potentials of surrounding vegetation on seedling establishment of the typical cushion plant Arenaria polytrichoides Edgew. along an elevational gradient, we extracted potential allelopathic compounds and tested their impacts on seed germination and seedling growth of A. polytrichoides. In addition, exclusion experiments using activated carbon were conducted to further elucidate these effects. Our results demonstrate that surrounding vegetation exhibits certain allelopathic potentials on A. polytrichoides seedling establishment, with variations observed based on elevation, source and concentration of allelopathy compounds, as well as growing season. Specifically, low-elevation vegetation exerts pronounced suppression on seedling establishment. Conversely, higher-elevation vegetation generally shows no effect on seed germination but stimulates seedling growth through allelopathy mechanisms. Moreover, aboveground vegetation predominantly inhibits both seed germination and seedling growth in low-elevation communities; however, the effects of belowground vegetation depend on elevation and extract concentration levels. The identified allelopathic potentials of surrounding vegetation significantly influence the population dynamics of cushion A. polytrichoides by potentially accelerating population degeneration in lower-elevation communities while ensuring consistent population recruitment and expansion in higher-elevation communities. [ABSTRACT FROM AUTHOR]

Introduction: Continuous cropping challenges have gradually emerged as pivotal factors limiting the sustainable development of agricultural production. Allelopathicals are considered to be the primary obstacles. However, there is limited information on allelopathic accumulation across various continuous cropping years and its correlation with the associated challenges. Methods: Tobacco was subjected to varying planting durations: 1 year (CR), 5 years (CC5), 10 years (CC10), and 15 years (CC15). Results: Our findings unveiled discernible disparities in tobacco growth patterns across diverse continuous cropping periods. Notably, the most pronounced challenges were observed in the CC5 category, characterized by yield reduction, tobacco black shank outbreaks, and a decline in beneficial flora. Conversely, CC15 exhibited a substantial reduction in challenges as the continuous cropping persisted with no significant differences when compared to CR. Within the tobacco rhizosphere, we identified 14 distinct allelopathic compounds, with 10 of these compounds displaying noteworthy variations among the four treatments. Redundancy analysis (RDA) revealed that eight allelopathic compounds exhibited autotoxic effects on tobacco growth, with MA, heptadecanoic acid, and VA ranking as the most potent inhibitors. Interaction network highlighted the pivotal roles of VA and EA in promoting pathogen proliferation and impeding the enrichment of 13 beneficial bacterial genera. Furthermore, a structural equation model elucidated that MA and EA primarily exert direct toxic effects on tobacco, whereas VA fosters pathogen proliferation, inhibits the enrichment of beneficial bacteria, and synergistically exacerbates the challenges associated with continuous cropping alongside EA. Discussion: These findings suggested discernible disparities in tobacco growth patterns across the various continuous cropping periods. The most pronounced challenges were observed in CC5, whereas CC15 exhibited a substantial reduction in challenges as continuous cropping persisted. VA may play a pivotal role in this phenomenon by interacting with pathogens, beneficial bacterial genera, and EA. [ABSTRACT FROM AUTHOR]

Due to the aging of trees, aged apple and cherry orchards need to be rebuilt urgently. However, due to the limitation of land resources, it is inevitable to rebuild the apple orchard by taking the aged cherry orchard as a replacement, which will lead to replant disease and seriously affect the sustainable development of the horticulture industry. This study investigated the effect of aged cherry orchard soil on the growth of M. hupehensis seedlings grown in pots, and it was further verified that allelochemicals in soil were one of the reasons for this effect. Three treatments were implemented: aged apple orchard soil (ppl), aged cherry orchard soil (pyl), and aged cherry orchard soil after fumigation with methyl bromide (pyz). Compared with pyz, pyl treatment significantly decreased the biomass, root growth, and antioxidant enzyme activity of M. hupehensis seedlings, and increased the content of MDA. Compared with ppl, pyl contains a smaller number of fungi and bacteria, but the abundance of the four disease-causing Fusarium remained high. In addition, the levels of allelochemicals found in the soil of aged cherry orchards can inhibit the normal growth and development of M. hupehensis seedlings. Amygdalin most strongly inhibited these seedlings. In summary, directly planting M. hupehensis seedlings in the soil of the aged cherry orchards still inhibits their normal growth and development, although the seedlings grow better than in aged apple orchard soil. Therefore, it is not feasible to directly plant M. hupehensis seedlings in the soil of aged cherry orchards, and measures should be taken to eliminate allelochemicals such as amygdalin and harmful microorganisms. [ABSTRACT FROM AUTHOR]

The fruit of Forsythia suspensa (Thunb.) Vahl has been used in traditional Chinese medicine as "Forsythiae fructus". The species is also grown in parks and gardens, and on streets and building lots, as an ornamental plant, but it requires pruning. In this study, the allelopathic activity and allelopathic substances in the leaves of pruned branches of F. suspensa were investigated to determine any potential application. The leaf extracts of F. suspensa showed growth inhibitory activity against three weed species; Echinochloa crus-galli, Lolium multiflorum, and Vulpia myuros. Two allelopathic substances in the extracts were isolated through the bioassay-guided purification process, and identified as (-)-matairesinol and (-)-arctigenin. (-)-Matairesinol and (-)-arctigenin, which showed significant growth inhibitory activity at concentrations greater than 0.3 mM in vitro. The inhibitory activity of (-)-arctigenin was greater than that of (-)-matairesinol. However, both compounds were more active than (+)-pinolesinol which is their precursor in the biosynthetic pathway. The investigation suggests that F. suspensa leaves are allelopathic, and (-)-matairesinol and (-)-arctigenin may contribute to the growth inhibitory activities. Therefore, the leaves of the pruned branches can be applied as a weed management strategy in some agricultural practices such as using the leaf extracts in a foliar spray and the leaves in a soil mixture, thereby reducing the dependency on synthetic herbicides in the crop cultivation and contributing to developing eco-friendly agriculture. [ABSTRACT FROM AUTHOR]

Platycodon is a medicinal plant of considerable pharmacological and dietary value. With the growing demand, agricultural production is increasing. However, the continuous cropping significantly causes negative impacts on its yield and quality. In this study, in order to solve the problem of continuous cropping, we evaluated the allelopathic activity of Platycodon and investigated the potential use of activated carbon for mitigating the negative impacts of allelopathic chemicals produced by Platycodon. The sandwich method (method for assaying the allelopathic activity of each part of a plant) was employed to evaluate the allelopathic activity of different parts (leaves, stems, and roots) of Platycodon. The inhibitory effects of various Platycodon plant parts were assessed based on their effects on lettuce seedling growth. At a concentration of 10 mg parts/10 mL agar, the average inhibition rates of Platycodon leaves on the radicle and hypocotyl growth of lettuce were 79.4% and 61.8%, stems 58.0% and 45.7%, and roots 53.4% and 49.3%, respectively. At a concentration of 50 mg parts/10 mL agar, the inhibitory effects were as follows: leaves (91.9%, 72.2%), stems (79.5%, 60.3%), and roots (71.4%, 65.2%). The effect of activated carbon on the adsorption of allelopathic substances was investigated, and the results of the sandwich method with a concentration of 10 mg parts/10 mL agar showed the following growth-inhibitory effects on lettuce seedlings and hypocotyls—roots (27.8%, 25.7%), leaves (13.3%, 25.7%), and stems (9.1%, 13.6%)—in each case showing a significant decrease in the inhibitory activity. The plant box method (method for assaying the allelopathic activity of plant root exudates) was employed to evaluate the activity of Platycodon root exudate. The growth inhibition rates of lettuce radicle and hypocotyls were 45.5% and 18.9%, respectively. The plant box method with addition of activated carbon revealed average rates of promotion of 16.7% and 4.7% on the growth of lettuce seedlings and hypocotyls, respectively. The results of this study demonstrated that activated carbon has a mitigating effect on allelopathic inhibition associated with the different plant parts and root exudation of Platycodon and provide a potential solution for overcoming problems associated with the continuous cropping of Platycodon. [ABSTRACT FROM AUTHOR]

Screening different plant species for herbicidal activity and identifying new allelochemicals with novel structures and phytochemical activity could be promising candidates for reducing the negative consequences of chemical herbicides. Our study aims to investigate the allelopathic substance(s) and herbicidal efficacy of Cleome rutidosperma DC. on rice filed weeds in the lab and glasshouse. The phytochemical constituents of the methanol extract of Cleome rutidosperma were analyzed by high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (HPLCESI-QTOF-MS). The allelopathic effect of C. rutidosperma has been further studied on the germination and early development of five common rice field weeds: Echinochloa crus-galli (L.) P. Beauv., Fimbristylis miliacea (L.) Vahl, Oryza sativa f. spontanea Roshev., Leptochloa chinensis (L.) Nees, and Cyperus iria L. The seed germination and growth of tested weeds under lab and glasshouse conditions were compared to three concentrations of C. rutidosperma methanol extract at 2.5, 5, and 10% with the control (only distilled water). The results indicated the presence of 64 and 10 known chemicals using positive and negative ionization techniques, the majority of which were toxic. The inhibitory effect of C. rutidosperma was stronger in the lab than in the glasshouse. No seed germination of the tested species was observed when 10% C. rutidosperma extract was applied. The photosynthesis rate of C. iria exhibited a higher reduction (70.56%) compared to other species at higher doses (10%) of C. rutidosperma. These findings demonstrated that C. rutidosperma is a significant source of phytotoxic components and can be used to develop future bio-herbicides. The outcome of this study can be employed in the organic management of weeds and reduce our heavy reliance on synthetic herbicides. [ABSTRACT FROM AUTHOR]

Weeds present a significant challenge to high crop yield and quality. In our study, we investigated the phytotoxic activity of β-caryophyllene (BCP) and eugenol, which are natural allelopathic chemical compounds, on Arabidopsis seedlings. We found that these compounds inhibited the growth of Arabidopsis thaliana plants. When either BCP or eugenol was applied, it led to decrease in the content of cell wall components such as lignin, cellulose, hemicellulose, and pectin; and increase in the levels of endogenous hormones like ETH, ABA, SA, and JA in the seedlings. Through transcriptome profiling, we identified 7181 differentially expressed genes (DEGs) in the roots and shoots that were induced by BCP or eugenol. The genes involved in the synthesis of lignin, cellulose, hemicellulose, and pectin were down-regulated, whereas genes related to synthesis and signal transduction of ABA, ETH, SA, and JA were up-regulated. However, genes related to IAA synthesis and signal transduction were found to be down-regulated. Furthermore, we characterized 24 hub genes using Weighted Correlation Network Analysis (WGCNA). Among them, the identified 16 genes in response to BCP was primarily associated with hypoxia stress, while 8 genes induced by eugenol were linked to inhibition of cell division. Our results suggested that BCP and eugenol had ability to target multiple genes to inhibit growth and development of Arabidopsis plants. Therefore, they can serve as excellent candidates for natural biological herbicides. [ABSTRACT FROM AUTHOR]

Iris pallida Lam., also known as Sweetie Iris, is a perennial ornamental and medicinal plant that produces a wide range of secondary metabolites. The Sweetie Iris was recently reported to have high allelopathic properties with the potential to be explored in sustainable weed management. This study aimed to identify and evaluate the contributions of compounds involved in the inhibitory effects of the rhizome of Sweetie Iris. High-performance liquid chromatography (HPLC) analysis was used to determine the content of β-ionone in the rhizome of Sweetie Iris. The phytotoxicity of β-ionone was evaluated on lettuce (Lactuca sativa L.) and other test plants. The content of β-ionone in the crude extract of Sweetie Iris rhizome was found to be 20.0 mg g−1 by HPLC analysis. The phytotoxicity bioassay showed that β-ionone had strong inhibitory activity on the growth of lettuce (Lactuca sativa L.) and the other test plants, including Taraxacum officinale, Stellaria media, Eleusine indica, Amaranthus hybridus, Vicia villosa, and Brassica napus. At a concentration of 23.0 µg mL−1, β-ionone inhibited the growth of all test plant species treated. Therefore, β-ionone is an active compound among the other allelopathic substances contained in the rhizome of Sweetie Iris. [ABSTRACT FROM AUTHOR]

Among the factors that affect potato productivity, the interference caused by weeds stands out as they may compete with the crop, release allelopathic substances to soil and host insects and diseases. Therefore, the objective of this work was to assess the competitive ability of white (Aghata) and pink (Asterix) potato cultivars when infested by Alexandergrass (Urochloa plantaginea) or wild poinsettia (Euphorbia heteroplylla). The experiment was carried out into greenhouse in randomized blocks design, with four replications. A single potato plant faced competition by either Alexandergrass or wild poinsettia, ranging from 0 to 64 plants per plot. Fifty days after seedling transplanting, variables related to the morphophysiology of potato cultivars and weeds were assessed. Potatoes have low competitive ability with both weed species, with wild poinsettia being the most aggressive in reducing the accumulation rates of leaf area and aboveground dry mass. Potato photosynthetic rate is negatively influenced by the presence of both weeds. Internal CO2 concentration, stomatal conductance, carboxylation efficiency and transpiration rates of potato varied depending on weed species and density. Morphological parameters are reduced when potato competed with Alexandergrass or wild poinsettia; however the physiological parameters are most sharply affected when under competition with wild poinsettia. [ABSTRACT FROM AUTHOR]

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Root exudates of the invasive Solidago canadensis and the cereal crop Sorghum bicolor (L.) Moench cv. 'Hybridsorgo' were tested for allelopathic interactions against native and invasive plant species in a controlled environment. After the surface was sterilized, the seeds of two invasive species (Bromus sterilis and Veronica persica) and two native species (Youngia japonica and Rumex acetosa) were germinated and transplanted into the soil (1:1 mixture of coco peat and sand) that had been conditioned for one month by the cultivation of Solidago canadensis and Sorghum bicolor, both in combination or as unplanted controls. After an additional eight weeks of growth, morphometric measurements of the shoot and root, including foliar characteristics and above- and below-ground biomass accumulation, were performed. The results revealed significant inhibitory effects of root exudates released by Sorghum bicolor and Solidago canadensis on native species' productivity and physiology. The invasive species exhibited variable growth responses, with Veronica persica showing reduced shoot and root expansion, but Bromus sterilis revealed increased shoot and root biomass allocation and nutrition under the exudate treatments. Exudates from Solidago canadensis and Sorghum bicolor together showed synergistic negative effects on native species, while they promoted growth and nutrition in Veronica persica. Taken together, the differential species responses indicate that the tested native species were more sensitive to the allelopathic compounds than the invasive species, which is in line with the theory of novel weapons. The legacy effects of root exudates of both Sorghum bicolor and Solidago canadensis could promote invasive establishment through imposing allelochemical interference competition against native plant species. Understanding the specific allelopathic mechanisms may help with the development of integrated strategies for managing invasive species. [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]

Casparian strip membrane domain protein-like (CASPL) genes are key genes for the formation and regulation of the Casparian strip and play an important role in plant abiotic stress. However, little research has focused on the members, characteristics, and biological functions of the patchouli PatCASPL gene family. In this study, 156 PatCASPL genes were identified at the whole-genome level. Subcellular localization predicted that 75.6% of PatCASPL proteins reside on the cell membrane. A phylogenetic analysis categorized PatCASPL genes into five subclusters alongside Arabidopsis CASPL genes. In a cis-acting element analysis, a total of 16 different cis-elements were identified, among which the photo-responsive element was the most common in the CASPL gene family. A transcriptome analysis showed that p-hydroxybenzoic acid, an allelopathic autotoxic substance, affected the expression pattern of PatCASPLs, including a total of 27 upregulated genes and 30 down-regulated genes, suggesting that these PatCASPLs may play an important role in the regulation of patchouli continuous cropping obstacles by affecting the formation and integrity of Casparian strip bands. These results provided a theoretical basis for exploring and verifying the function of the patchouli PatCASPL gene family and its role in continuous cropping obstacles. [ABSTRACT FROM AUTHOR]

Over the past few decades, nearly 300 known cyanotoxins and more than 2000 cyanobacterial secondary metabolites have been reported from the environment. Traditional studies have focused on the toxic cyanotoxins produced by harmful cyanobacteria, which pose a risk to both human beings and wildlife, causing acute and chronic poisoning, resulting in diarrhea, nerve paralysis, and proliferation of cancer cells. Actually, the biotechnological potential of cyanotoxins is underestimated, as increasing studies have demonstrated their roles as valuable products, including allelopathic agents, insecticides and biomedicines. To promote a comprehensive understanding of cyanotoxins, a critical review is in demand. This review aims to discuss the classifications; biosynthetic pathways, especially heterogenous production; and potential applications of cyanotoxins. In detail, we first discuss the representative cyanotoxins and their toxic effects, followed by an exploration of three representative biosynthetic pathways (non-ribosomal peptide synthetases, polyketide synthetases, and their combinations). In particular, advances toward the heterologous biosynthesis of cyanotoxins in vitro and in vivo are summarized and compared. Finally, we indicate the potential applications and solutions to bottlenecks for cyanotoxins. We believe that this review will promote a comprehensive understanding, synthetic biology studies, and potential applications of cyanotoxins in the future. [ABSTRACT FROM AUTHOR]

Investigation of allelopathic substances from herbal plants may lead to the development of allelochemical-based natural herbicides. Croton oblongifolius (Roxb.) is a well-known herbal plant with a long history of being used for traditional medicines and for being the source of a diverse range of bioactive compounds. This plant has been reported to have allelopathic potential; however, its allelopathic-related substances have not yet been described. Therefore, we conducted this investigation to explore the allelopathic substances from the leaves of C. oblongifolius. Aqueous methanol extracts of C. oblongifolius leaves exhibited significant growth inhibitory potential against four test plants (monocot barnyard grass and timothy, and dicot cress and lettuce). The leaf extracts were purified in various chromatographic steps and yielded four active compounds identified as (3R,6R,7E)-3-hydroxy-4-7-megastigmadien-9-one (I), 2-hydroxy alpinolide (a novel compound) (II), alpinolide (III), and epialpinolide (IV) via an analysis of the spectral data. These identified compounds significantly restricted the seedling growth of cress. The concentration necessary for 50% growth reduction of the cress seedlings varied from 0.15 to 0.24 mM for (3R,6R,7E)-3-hydroxy-4-7-megastigmadien-9-one, 0.04 to 0.11 mM for 2-hydroxy alpinolide, 0.07 to 0.12 mM for alpinolide, and 0.09 to 0.16 mM for epialpinolide. Therefore, the leaf extracts of C. oblongifolius and the characterized compounds have the potential to be used as weed-suppressive resources for natural weed control. [ABSTRACT FROM AUTHOR]

Representative species of the Taxus genus, known since antiquity for their toxicity, have been an essential plant resource for the production of plant extracts with medicinal properties (antiinflammatory, antifungal, and antibacterial) and, more recently, for the study of their allelopathic properties with significant implications in organic agriculture (bioherbicidal potential). With a view to the development of this new direction of research, the present work aims: to present a qualitative evaluation of two types of plant extracts (aqueous and alcoholic) of different concentrations (1% and 5%) obtained from various organs (bark, leaves, arils, and seeds) belonging to three Taxus taxa: a spontaneous taxa - Taxus baccata L. (T1) and two cultivated taxa - Taxus baccata (T2) and Taxus baccata 'Robusta' (T3) at different times of the phenological cycle by determining their absorption spectra (of both types of extracts), total amounts of polyphenols and flavonoids, and by evaluating their antioxidant capacity (alcoholic extracts); to investigate, under experimental conditions of cultivation the possible allelopathic effects induced by the aqueous extracts on the germination, growth, and development of the seedlings in two test plant species: Amaranthus retroflexus L. (ruderal species) and Lycopersicon esculentum Mill, variety Silvia (crop species). The data indicates the presence of phenolic and compounds, alkaloids, and carotenoid pigments in the alcoholic extracts prepared from the different organs of the studied yew taxa, showing higher amounts of polyphenols and flavonoids in the extracts obtained from the leaves of taxon T2 compared to taxon T1. The effect of 1% and 5% aqueous extracts obtained from the bark of the three investigated yew taxa, as well as 1% aqueous extracts prepared from the leaves of taxon T3 on seed germination, seedling growth, and development was more pronounced in the crop species Lycopersicon esculentum Mill, variety Silvia, compared to the ruderal broadleaf weed Amaranthus retroflexus L., both species having rapid germination stimulated by ambient light. Aqueous extracts of 5% concentration obtained from the arils of plants belonging to the three yew taxa stimulated the elongation of the seedlings' hypocotyls of both test species. [ABSTRACT FROM AUTHOR]

Polygonum chinense Linn., belonging to the Polygonaceae family, is distributed mostly in northern temperate climates. This species is a high-risk invasive plant and is thought to possess allelopathic potential. This study aimed to isolate and identify the allelopathic substances from P. chinense. Aqueous methanol extracts of P. chinense significantly inhibited the growth of alfalfa and Italian ryegrass seedlings in a species- and concentration-dependent manner. Activity-guided fractionation led to the isolation of two active compounds: dehydrovomifoliol and loliolide. A cress bioassay was used to determine the biological activity of dehydrovomifoliol, and cress, alfalfa, and Italian ryegrass were used to determine loliolide. Dehydrovomifoliol significantly suppressed the seedling growth of cress at the concentration of 1 mM, and the concentrations necessary for 50% growth inhibition (I50 values) of the roots and shoots were 1.2 and 2 mM, respectively. Loliolide significantly suppressed the shoot growth of cress, alfalfa, and Italian ryegrass at the concentration of 1 mM, and the concentrations necessary for I50 values of the shoots and roots were 0.15 to 2.33 and 0.33 to 2.23 mM, respectively. The findings of our study suggest the extracts of P. chinense might have growth-inhibitory potential and that dehydrovomifoliol and loliolide might contribute as allelopathic agents. [ABSTRACT FROM AUTHOR]

Trewia nudiflora Linn. is a valuable forest resource due to its economic, ethnomedicinal, and ecological properties; however, its allelopathic potential is undocumented. Therefore, this research was designed to investigate the allelopathic impacts of T. nudiflora leaf extracts on alfalfa (Medicago sativa L.) and barnyard grass (Echinochloa crus-galli (L.) P. Beauv.) growth, as well as to isolate and to identify the active allelopathic substances responsible for these effects. A bioassay experiment with eight different treatments (0.1, 0.3, 1, 3, 10, 30, 100, and 300 mg dry weight (DW) equivalents of T. nudiflora extracts in mL−1) was carried out. The results showed that the growth of both plants decreased with increasing contents of T. nudiflora extracts, with the effect depending on the plant species and reaching its peak at a concentration of a 300 mg DW equivalent of T. nudiflora extract in mL−1. Active substances were isolated and identified using an HPLC system, which revealed the presences of methyl gallate and pinoresinol in aqueous methanol extracts of T. nudiflora. The shoot and root lengths of the alfalfa and the barnyard grass decreased significantly when they were treated with the methyl gallate and the pinoresinol. The allelopathic inhibition increased with increasing compound concentrations, with the root growth being more sensitive to the pinoresinol than to the methyl gallate, and it was significantly higher at the concentration of 10 mM. These results indicated that the T. nudiflora leaf extracts limited the growth of the treated plants, and the methyl gallate and pinoresinol in the extracts may have caused the inhibition of the T. nudiflora extracts. Thus, the leaf extracts of T. nudiflora and the substances methyl gallate and pinoresinol could be incorporated into sustainable agricultural practices or used to develop bioherbicides that would promote sustainable weed management practices. [ABSTRACT FROM AUTHOR]

Barley (Hordeum vulgare) is one of the most widely cultivated crops for feedstock and beer production, whereas lupins (Lupinus spp.) are grown as fodder and their seeds are a source of protein. Both species produce the allelopathic alkaloids gramine and hordenine. These plant-specialized metabolites may be of economic interest for crop protection, depending on their tissue distribution. However, in high concentrations they pose a health risk to humans and animals that feed on them. This study was carried out to develop and validate a new method for monitoring these alkaloids and their related metabolites using fluorescence detection. Separation was performed on an HSS T3 column using slightly acidified water-acetonitrile eluents. Calibration plots expressed linearity over the range 0.09–100 pmol/µL for gramine. The accuracy and precision ranged from 97.8 to 123.4%, <7% RSD. The method was successfully applied in a study of the natural range of abundance of gramine, hordenine and their related metabolites, AMI, tryptophan and tyramine, in 22 barley accessions and 10 lupin species. This method provides accurate and highly sensitive chromatographic separation and detection of tryptophan- and tyrosine-derived allelochemicals and is an accessible alternative to LC-MS techniques for routine screening. [ABSTRACT FROM AUTHOR]

Improvements in agricultural productivity are required to meet the demand of a growing world population. Phytopathogens, weeds, and insects are challenges to agricultural production. The toxicity and widespread application of persistent synthetic pesticides poses a major threat to human and ecosystem health. Therefore, sustainable strategies to control pests are essential for agricultural systems to enhance productivity within a green paradigm. Allelochemicals are a less persistent, safer, and friendly alternative to efficient pest management, as they tend to be less toxic to non-target organisms and more easily degradable. Microalgae produce a great variety of allelopathic substances whose biocontrol potential against weeds, insects, and phytopathogenic fungi and bacteria has received much attention. This review provides up-to-date information and a critical perspective on allelochemicals from microalgae and their potential as biopesticides. [ABSTRACT FROM AUTHOR]

Plant parts and extracts that are rich in bioactive substances with allelopathic potential can be explored as a possible alternative to herbicides for natural weed control in sustainable agriculture. In the present study, we investigated the allelopathic potential of Marsdenia tenacissima leaves and its active substances. Aqueous methanol extracts of M. tenacissima showed significant inhibitory activities against the growth of lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), and barnyard grass (Echinochloa crusgalli (L.) Beauv.). The extracts were purified through various chromatography steps, and one active substance was isolated and determined by spectral data to be a novel compound, assigned as steroidal glycoside 3 (8-dehydroxy-11β-O-acetyl-12β-O-tigloyl-17β-marsdenin). Steroidal glycoside 3 significantly inhibited the seedling growth of cress at a concentration of 0.03 mM. The concentrations needed for 50% growth inhibition of the cress shoots and roots were 0.25 and 0.03 mM, respectively. These results suggest that steroidal glycoside 3 may be responsible for the allelopathy of M. tenacissima leaves. [ABSTRACT FROM AUTHOR]

Allelopathy, that is, plant–plant inhibition via the release of secondary metabolites into the environment, has potential for the management of weeds by circumventing herbicide resistance. However, mechanisms underpinning allelopathy are notoriously difficult to elucidate, hindering real‐world application either in the form of commercial bioherbicides or allelopathic crops. Such limited application is exemplified by evidence of limited knowledge of the potential benefits of allelopathy among end users. Here, we examine potential applications of this phenomenon, paying attention to novel approaches and influential factors requiring greater consideration, with the intention of improving the reputation and uptake of allelopathy. Avenues to facilitate more effective allelochemical discovery are also considered, with a view to stimulating the identification of new compounds and allelopathic species. Synthesis and Applications: We conclude that tackling increasing weed pressure on agricultural productivity would benefit from greater integration of the phenomenon of allelopathy, which in turn would be greatly served by a multi‐disciplinary and exhaustive approach, not just through more effective isolation of the interactions involved, but also through greater consideration of factors which may influence them in the field, facilitating optimization of their benefits for weed management. [ABSTRACT FROM AUTHOR]

Metasequoia glyptostroboides Hu et W.C. Cheng, known as a living fossil species, is planted in parks, gardens, and streets in many temperate regions worldwide. Adequate branch pruning is necessary to grow the plants in these locations, and pruning generates a large amount of waste. In this study, allelopathic activity of pruned-branch waste was investigated to search for beneficial applications of the waste. The leaves of M. glyptostroboides obtained from pruned branches were extracted, and the extracts showed growth-inhibitory activity on four weed species, namely, Vulpia myuros, Lolium multiflorum, Echinochloa crus-galli, and Phleum pretense. The inhibition was extract-concentration dependent. The roots of P. pretense were the most sensitive, and the coleoptiles of E. crus-galli were the least sensitive to the extracts among all roots and coleoptiles of these weed species. Two allelopathic substances in the extracts were isolated and identified as umbelliferone and (+)-rhododendrol. Both compounds showed inhibitory activity on the growth of V. myuros, although the inhibitory activity of (+)-rhododendrol was much greater than that of umbelliferone. The leaves may also contain some other allelopathic substances. These allelopathic substances, including umbelliferone and (+)-rhododendrol, may work as growth-inhibitory substances of leaf extracts. Therefore, the leaves of M. glyptostroboides obtained from pruned branches are allelopathic and potentially useful for weed control in certain agricultural settings such as foliar spray and soil additive, to decrease synthetic herbicide application in crop production pursuant to developing ecofriendly agriculture. [ABSTRACT FROM AUTHOR]

This study investigated the use of fall cover crops and spring buckwheat monoculture to suppress weeds and improve yields in sweet potato cultivation. Buckwheat emerged as a highly effective summer cover crop, providing robust weed suppression throughout the growing season. Its ability to shade weeds, compete for resources, and release allelopathic compounds contributed to its effectiveness. The selection of fall cover crops influenced weed suppression, with rye mixed with clover showing limited differences in weed densities, while rye mixed with hairy vetch reduced Palmer amaranth coverage. Sweet potato cultivars demonstrated varying levels of weed competition, with Beauregard exhibiting higher weed coverage compared to Heart-O-Gold and 529. These findings highlight the importance of selecting suitable cover crops and cultivars based on their competitive abilities and weed tolerance for effective weed management. Overall, incorporating appropriate cover crops and cultivars holds promise for suppressing weeds and improving sweet potato yields. [ABSTRACT FROM AUTHOR]

Polygonum chinense Linn. is a medicinal and invasive plant that belongs to the family Polygonaceae. The pharmacological activities and phytochemical constituents of Polygonum chinense are well reported, but the allelopathic effects and potent allelopathic substances of P. chinense remain to be investigated. Hence, this experiment was conducted to separate and characterize potentially allelopathic substances from an extract of the Polygonum chinense plant. The Polygonum chinense plant extracts highly suppressed the growth of cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crusgalli (L.) P. Beauv.), and timothy grass (Phleum pratense L.) seedlings in a species- and concentration-dependent way. Two active substances were separated using a series of purification procedures and determined through spectral analysis as (−)-3-hydroxy-β-ionone and (−)-3-hydroxy-7,8-dihydro-β-ionone. These two compounds significantly suppressed the seedling growth of Lepidium sativum (cress) at concentrations of 0.01 and 1 mM, respectively. The extract concentrations necessary for 50% growth inhibition (I50 values) of the cress hypocotyls and roots were 0.05 and 0.07 mM for (−)-3-hydroxy-β-ionone, respectively, and 0.42 and 1.29 mM for (−)-3-hydroxy-7,8-β-ionone, respectively. These findings suggest that these two compounds are in charge of the inhibitory effects of the Polygonum chinense extract and may serve as weed control agents. [ABSTRACT FROM AUTHOR]

In this study, the allelopathic properties of Medicago sativa L. (alfalfa) seedling exudates on the germination of seeds of various species were investigated. The compounds responsible for the allelopathic effects of alfalfa were identified and characterized by employing liquid chromatography ion mobility high-resolution mass spectrometry. Crude exudates inhibited the germination of seeds of all various plant species tested. Overall, nine compounds in alfalfa were identified and quantified. The most predominant compounds were a hyperoside representing a flavonoid glucoside, the non-proteinogenic amino acid canavanine, and two dipeptides, identified as H-Glu-Tyr-OH and H-Phe-Glu-OH. The latter corresponds to the first finding that dipeptides are exuded from alfalfa seedlings. In addition, the antibacterial and antibiofilm activities of alfalfa exudate and its identified compounds were elucidated. Both hyperoside and canavanine revealed the best antibacterial activity with minimum inhibitory concentration (MIC) values that ranged from 8 to 32 and 32 to 256 µg/mL, respectively. Regarding the antibiofilm action, hyperoside and canavanine caused a decline in the percentage of E. coli isolates that possessed a strong and moderate biofilm-forming potential from 68.42% to 21.05% and 31.58%, respectively. Studies on their inhibiting effects exhibit that these major substances are predominantly responsible for the allelopathic and antimicrobial effects of the crude exudates. [ABSTRACT FROM AUTHOR]

Trewia nudiflora Linn. is a woody plant of the Euphorbiaceae family. It is well known for its use as a folk remedy, but its potential for phytotoxicity has not been explored. Therefore, this study investigated the allelopathic potential and the allelopathic substances in T. nudiflora leaves. The aqueous methanol extract of T. nudiflora was found to have a toxic effect on the plants used in the experiment. The shoot and root development of lettuce (Lactuca sativa L.) and foxtail fescue (Vulpia myuros L.) were significantly (p ≤ 0.05) reduced by the T. nudiflora extracts. The growth inhibition by the T. nudiflora extracts was proportional to the extract concentration and varied with the test plant species. The chromatographic separation of the extracts resulted in the isolation of two substances, identified as loliolide and 6,7,8-trimethoxycoumarin based on their respective spectral analyses. Both substances significantly inhibited lettuce growth at a concentration of 0.01 mM. To inhibit 50% of the growth of the lettuce, the required concentration of loliolide was 0.043 to 0.128 mM, while that of 6,7,8-trimethoxycoumarin was 0.028 to 0.032 mM. Comparing these values, the lettuce growth was more sensitive to 6,7,8-trimethoxycoumarin than loliolide, suggesting that 6,7,8-trimethoxycoumarin was more effective than loliolide. Therefore, the inhibition of the growth of the lettuce and foxtail fescue suggests that loliolide and 6,7,8-trimethoxycoumarin are responsible for the phytotoxicity of the T. nudiflora leaf extracts. Thus, the growth-inhibitory effectiveness of the T. nudiflora extracts and the identified loliolide and 6,7,8-trimethoxycoumarin may be used to develop bioherbicides that restrict the growth of weeds. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi traditionally form symbioses with most plant species. Although AM fungi have critical effects on microbial communities, the pathways showing how AM fungi shape rhizosphere bacterial communities and their functions are rarely explored.Here, through three systematic experiments, AM fungi–bacteria interactions were first investigated in the rhizosphere of Lotus japonicus, then the interactions were confirmed by a second experiment with wild‐type and a mycorrhiza‐defective mutant ljcbx of L. japonicus. The mechanisms were presented by adding core bacteria and AM fungi to the plant rhizosphere in the third experiment.We found that AM fungi–bacteria interactions enhanced host plant growth and identified a core bacterial group that uniquely enhanced host plant growth. Adding core bacteria and AM fungi promoted host growth and nutrient acquisition compared to adding AM fungi or core bacteria independently.Allelopathic substances secreted by AM fungal colonizing host roots to recruit the rhizosphere bacteria were detected by the multi‐omics joint analysis, showing that arachidonic acid was the main allelopathic substance that affected AM fungi–bacteria interactions.Our findings provide direct evidence that mycorrhizal infection simulated root exudation, such as arachidonic acid, recruited a beneficial microbiome to the host rhizosphere, increasing plant growth and soil nutrient turnover. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Cyanobacteria are photosynthetic prokaryotes and one of dominant species in eutrophicated waters, which easily burst blooms in summer with high irradiance and temperature conditions. In response to high irradiance, high temperature, and nutrient conditions, cyanobacteria release abundant of volatile organic compounds (VOCs) by up-regulating related gene expression and oxidatively degrading b-carotene. These VOCs not only increase offensive odor in waters, but also transfer allelopathic signals to algae and aquatic plants, resulting in cyanobacteria dominating eutrophicated waters. Among these VOCs, b-cyclocitral, a-ionone, b-ionone, limonene, longifolene, and eucalyptol have been identified as the main allelopathic agents, which even directly kill algae by inducing programmed cell death (PCD). The VOCs released from cyanobacteria, especially the ruptured cells, exhibit repelling effects on the herbivores, which is beneficial to survival of the population. Cyanobacterial VOCs might transfer aggregating information among homogeneous species, so the acceptors initiate aggregation to resist the coming stresses. It can be speculated that the adverse conditions can promote VOC emission from cyanobacteria, which play important roles in cyanobacteria dominating eutrophicated waters and even bursting blooms. [ABSTRACT FROM AUTHOR]

Many studies have focused on how leaf litter depth affects seed germination and seedling growth because the seedling stage is the most vulnerable portion of a plant's life cycle. Invasive plants with the most severe ecological consequences are those that modify ecosystems, and this can occur through the formation of thick litter layers which can suppress the emergence, survival, and recruitment of native plant seedlings; in addition, in some cases, these litter layers can suppress invasive plant seedling recruitment. Prosopis juliflora is a thorny shrub that is native to arid and semi-arid portions of North America, parts of South America, and the Caribbean. It has invaded millions of hectares around the world, including Saudi Arabia. The objective of this study is to evaluate whether P. juliflora leaf litter reduces the recruitment of its own seedlings under greenhouse and field conditions in Saudi Arabia. In both the greenhouse and the field, the number of days to first emergence increased and germination percentage decreased with increasing litter depth. With the 1, 2, and 4 cm litter depth treatments, the number of viable seeds generally decreased, with no emergence, germination, or viable seeds detected for the 8 cm litter depth treatment. Results of this study reveal that increasing the depth of P. juliflora leaf litter suppresses the survival and recruitment of its own seedlings. Future search should assess the actual mechanisms through which P. juliflora seeds are suppressed, the role of allelopathic compounds in this process, and whether viable seeds are dormant and will persist in the soil seed bank. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that monocropping of flue-cured tobacco can lead to various issues, including nutrient deficiencies, accumulation of allelopathic substances, and disturbance in soil microbial flora. While diversification in cropping systems has proven effective in alleviating monocropping barriers, however, further exploration is needed to understand the potential microbial mechanisms involved in this process. In our study, we set five cropping systems (RR: rice monocropping; TR: tobacco-rice rotation over 20 years; TRA: tobacco-rice-astragalus rotation; TRW: tobacco-rice-wheat rotation; TRO: tobacco-rice-oilseed rape rotation) to explore the impact on crop yield and quality, soil chemical properties, and microbial diversity. The results showed that the yield and gross margin were significantly decreased. Following diversification in cropping systems, particularly after implementing the TRA treatment, the yield and gross margin increased by 27.35% and 38.67%, respectively, compared to the TR treatment. Additionally, the presence of tobacco in the soil resulted in acidification, reduced soil fertility, and suppression of soil microorganism diversity and metabolite abundance. With diversification in cropping systems, there was an increase in soil pH, carbon and nitrogen cycle enzyme activities, and the relative abundance of beneficial microorganisms (acidobacteria, nitrospirillum, and ascomycota) and soil metabolites. Diversification in cropping systems has the potential to increase crop biomass, soil fertility, and soil microbial environment. Our results suggest a scientific foundation for implementing effective nutrient management practices and rational crop rotation systems. [Display omitted] • Continuous cropping obstacles reduced pH, soil fertility, and reduced microbial diversity. • Diversified planting enhanced soil fertility and promoting the growth of beneficial microorganisms and metabolites. • Tobacco-astragalus-rice was the best rotation system in Wannan tobacco area. [ABSTRACT FROM AUTHOR]

Osmanthus fragrans Lour. has been cultivated for more than 2500 years because of the fragrance and color of the flowers. The flowers and roots have been used in tea, liquors, foods, and traditional Chinese medicine. The species contains more than 180 compounds including terpenoids, phenylpropanoids, polyphenols, flavonoids, and sterols. However, there has been limited information available on the allelopathic properties and allelopathic substances of O. fragrans. We investigated the allelopathy and allelopathic substances of O. fragrans and Osmanthus heterophyllus (G.Don) P.S. Green, as well as Osmanthus × fortunei Carrière, which is the hybrid species between O. fragrans and O. heterophyllus. The leaf extracts of O. fragrans, O. heterophyllus, and O. × fortunei suppressed the growth of cress (Lepidium sativum L.), alfalfa (Medicago sativa L.), Lolium multiflorum Lam., and Vulpia myuros (L.) C.C.Gmel with the extract concentration dependently. The extract of the hybrid species O. × fortune was the most active among the extracts. The main allelopathic substances of O. × fortunei and O. fragrans were isolated and identified as (+)-pinoresinol and 10-acetoxyligustroside, respectively. (+)-Pinoresinol was also found in the fallen leaves of O. × fortunei. Both compounds showed an allelopathic activity on the growth of cress and L. multiflorum. On the other hand, several allelopathic substances including (+)-pinoresinol may be involved in the allelopathy of O. heterophyllus. O. fragrans, O. heterophyllus, and O. × fortunei are evergreen trees. but their senescent leaves fall and cover the soil under the trees. It is possible that those allelopathic substances are liberated through the decomposition process of the leaves into their rhizosphere soil, and that they accumulate in the soil and provide a competitive advantage to the species through the inhibition of the growth of the neighboring competing plants. Therefore, the leaves of these Osmanthus species are allelopathic and potentially useful for weed management options in some agriculture settings to reduce commercial herbicide dependency for the developing sustainable agriculture systems. [ABSTRACT FROM AUTHOR]

Invasive species control management involves a large amount of plant material. The present work evaluated the allelopathic potential of the invasive species Ulex europaeus L. (Fabaceae) or 'Gorse' and its possible use as a bioherbicide, taking advantage of the extracted plant material after control measures, particularly needed in invaded areas. Specifically, we investigated the efficacy of dried plant material from U. europaeus in the control of the adventitious plants, Lolium multiflorum Lam. and Lolium rigidum Gaud., using the Avena sativa L. crop as a case study. We only used vegetative plant parts because it is essential to avoid the dispersion of U. europaeus with its use, especially in invaded areas. A greenhouse pot experiment was conducted, using activated carbon (AC). The target species (L. multiflorum, L. rigidum and A. sativa) were subjected to a mixture of organic substrate with U. europaeus mulch applied pre-emergence and a subsequent application of aqueous extracts from the mulch. Emergence, height and biomass of the target species were determined. After 2 months, we also tested a possible legacy effect of the substrate on the germination of the target species. We noticed a negative effect of U. europaeus mulch on the emergence of L. rigidum, which can be attributable to the allelopathic compounds released from U. europaeus mulch because the effect was non-significant in presence of AC. Conversely, no effect on L. multiflorum or A. sativa was produced by mulch treatments. Nevertheless, the combination of U. europaeus mulch and its extracts demonstrated a phytotoxic effect on the biomass of the crop species A. sativa, and a fertilizing effect on the weeds L. multiflorum and L. rigidum, which is why this use is discouraged. With our results we cannot recommend the use of U. europaeus as a bioherbicide in oat crops, but this study emphasizes the capability of U. europaeus to structure plant communities through the chemic- and bio-properties of its tissues that modifies the soil environment. [ABSTRACT FROM AUTHOR]

Climate change is a driver of biodiversity loss, often favouring invasive species such as in the case of Pittosporum undulatum in Eucalyptus forests of south-eastern Australia. We tested whether the invasiveness of P. undulatum is due to the release of secondary metabolites with allelopathic action inhibiting other species germination or to the content of antioxidant secondary metabolites. We compared the germination of P. undulatum and Eucalyptus ovata seeds on different substrates watered with different leachates. Polyphenolic compounds, saponins and tannins of Eucalyptus spp. and P. undulatum leaf extracts were quantified. Biogenic Volatile Organic Compounds were collected in the field and analyzed to compare the emissions in eucalypt forests with and without P. undulatum. Eucalyptus germination rates were not affected by different leachates and no allelopathic compounds were identified in P. undulatum leachate. Flavonoids and tannins characterized Eucalyptus leachates, while P. undulatum leachates showed high hydroxycinnamic acids content. The forests invaded by P. undulatum were characterized by high levels of monoterpenes, whereas the forest lacking P. undulatum were dominated by sesquiterpenes. Our results suggest that the invasiveness of P. undulatum may be due to the high content in secondary metabolites that play a protective role against abiotic stresses rather than the release of allelopathic compounds. [ABSTRACT FROM AUTHOR]

The article describes the fine mapping of a quantitative trait locus (QTL) qPA7-1 for low hydrocyanic acid (HCN) content in sorghum-sudangrass hybrid. The study determined the HCN content in sorghum-sudangrass hybrid population and screened simple sequence repeats (SSR) polymorphic primers. A high-resolution genetic linkage group of QTL qPA7-1 of the low HCN trait was constructed and candidate genes responsible for the low HCN trait were identified.

Agricultural production depends heavily on the application of synthetic herbicides. Using these herbicides results in the development of herbicide-resistant weeds, poses hazards to human and animal health, and pollutes the environment. To solve these problems, developing and using bioherbicides must be increased. Although different uses of Albizia procera have been well reported, its allelopathic activity against weeds and crop species has not. Hence, we evaluated the allelopathic activity of the A. procera plant and isolated its allelopathic compounds. Extracts of A. procera significantly suppressed the seedling growth of the tested species (cabbage, alfalfa, lettuce, barnyard grass, timothy, and Italian ryegrass). The seedling growth decreased with increasing extract concentrations. The concentrations required for 50% growth inhibition (I50 value) of the tested plants were 0.0225–0.4935 mg/mL. The A. procera extracts were separated using different column chromatography, and two active fractions (AP-5 and AP-7) were isolated. Cress seedling growth was completely restricted by fraction AP-5, and fraction AP-7 restricted the cress shoots to 83.10% and roots to 85.65% of the control treatment. The findings of this study indicate that A. procera extracts have allelopathic activity and these fractions might contribute to the activity. [ABSTRACT FROM AUTHOR]

Summary: Litter decomposition releases nutrients beneficial to plants but also induces phytotoxicity. Phytotoxicity can result from either labile allelopathic compounds or species specific and caused by conspecific DNA. Aquatic plants in flowing water generally do not suffer phytotoxicity because litter is regularly removed. In stagnant water or in litter packs an impact on root functionality can occur. So far, studies on water plant roots have been carried out in laboratory and never in field conditions.The effect of conspecific vs heterospecific litter and purified DNA were assessed on aquatic roots of the riparian woody species Alnus glutinosa L. using a novel method, using closed and open plastic tubes fixed to single roots in the field with closed tubes analogous to stagnant water. Four fresh and four decomposed litter types were used and analysed on extractable C, cellulose, lignin, N content and using 13C‐CPMAS NMR spectroscopy.Inhibitory effects were observed with fresh litter in closed systems, with a positive correlation with extractable C and negative with lignin and lignin : N ratio. Alnus self‐DNA, but not heterologous one, caused acute toxic effects in the closed system.Our results demonstrate the first field‐based evidence for self‐DNA inhibition as causal factor of negative feedback between plants and substrate. [ABSTRACT FROM AUTHOR]