Allelopathic Interactions Research Articles

Effect of microplastics on the allelopathic effects of native and invasive plants on co-occurring invaders

IntroductionMicroplastic pollution has emerged as a significant global change factor, with the potential to alter the biological, physicochemical properties of soil and to subsequently affect plant growth. Despite growing recognition of the impacts of microplastic pollution, the mechanisms by which microplastics modify plant leaf chemistry and influence allelopathic interactions among co-existing plant species remain unclear.MethodsWe used the native perennial forb Achyranthes bidentata and the invasive annual forb Amaranthus spinosus as focal species. We grew the two species with and without competition with each other. This setup was further combined with a treatment involving the addition of polyethylene (PE). We then testd the effects of aqueous extract on seed germination and seedling growth for five invasive and five native species. Subsequently, metabolomic analysis was conducted on the aqueous extracts, in which significant allelopathic effects were observed on test species.Results and discussionThe presence of PE microplastics enhanced the biomass of both Achyranthes and Amaranthus under competitive and non-competitive growth conditions. Furthermore, PE microplastics were found to induce a negative allelopathic effect for the native plant Achyranthes on co-occurring plants, which appeared to be mediated through changes in leaf chemistry. Bisdemethoxycurcumin, ethylparaben, salicin 6’-sulfate and 5-hydroxy-3’,4’,7-trimethoxyflavone glucoside were proven important compounds for allelopathic enhancement. Overall, these results suggest that microplastic pollution has the capability to influence the co-existence of invasive and native plants by altering their allelopathic potential. This insight into the interactions between microplastics and plant allelopathy provides a novel perspective on how microplastic pollution could modify plant species interactions and ecosystem dynamics. Future studies could aim to answer how microplastics might affect plant root exudates and whether this process would mediate biological invasion.

Allelopathic Interactions Between the Green-Tide-Forming Ulva prolifera and the Golden-Tide-Forming Sargassum horneri Under Controlled Laboratory Conditions

Harmful algal blooms (HABs) represent a significant global marine ecological disaster. In the Yellow Sea, green and golden tides often occur simultaneously or sequentially, suggesting that interspecific competition involves not only spatial and resource competition but also allelopathy. This study investigated the allelopathic interactions between Ulva prolifera and Sargassum horneri using physiological and biochemical parameters, including relative growth rate (RGR), cell ultrastructure, chlorophyll fluorescence, enzyme activity, and metabolomics analysis. The results showed that S. horneri filtrate significantly inhibited U. prolifera growth, while U. prolifera filtrate had no significant effect on S. horneri. Both algal filtrates caused cellular damage and affected photosynthesis, enzyme activities, and metabolism. However, their allelopathic responses differed: U. prolifera may rely on internal compensatory mechanisms, while S. horneri may depend on defense strategies. These findings provide insights into the dynamics of green and golden tides and support the scientific control of HABs through allelopathy.

Sole and sequential application of herbicides and botanicals for weed management in summer sesame

Weed infestation poses a significant challenge in sesame cultivation, leading to yield losses and decreased economic returns for farmers. The present study comprehensively analyses various weed control approaches, including allelopathic interaction with integrating herbicides and hand-weeding practices. The experiment was conducted at the Agriculture Farm, SOA, Odisha, during the summer of 2023 with 10 weed management treatments in RBD with 3 replications. The objective was to study different weed management practices, including the sole and sequential application of herbicides and botanicals, to control diverse weeds and enhance summer sesame growth, yield and profitability. The dominance of Digitaria sanguinalis (L.) Scop., Echinochloa colona (L.) Link. and Poa annua L. among grassy weeds and Melochia corchorifolia L., Cleome viscosa L. and Cassia tora L. among the broadleaved weeds were evident in summer sesame. The execution of different treatments showed that integrated use of aqueous leaf extract of Parthenium hysterophorus at 5 % concentration, followed by quizalofop-p-ethyl at 50 g/ha, was found on par with hand-weeding and brought down the weed count and biomass, which in turn increased the growth of summer sesame. The maximum yield of (793 kg seed/ha and 3035 kg stalk/ha) was registered under twice hand weeding. It was comparable with the spraying of aqueous leaf extract of Parthenium hysterophorus at 5 % concentration followed by (fb) quizalofop-p-ethyl at 50 g/ha (772 kg seed/ ha and 2968 kg stalk/ha). Economic analysis of sesame revealed that the maximum return (Rs. 37454/- per ha) and return/rupee (2.28) were recorded with aqueous leaf extract of P. hysterophorus at 5 % concentration fb quizalofop-p-ethyl at 50 g/ha treatment.

Food as a factor determining the physiological state of populations of the phytopagous pests of agricultural crops

Relevance. Trophic relationships along with competition and mutualism are the most basic and significant interactions in ecosystems. To develop, survive, and multiply, insects need to consume a certain amount of nutrients at a certain ratio. Food products are complex mixes of nutrients and non-nutritive substances (sometimes toxic ones): macronutrients (proteins, carbohydrates, and lipids), micronutrients (vitamins and minerals), and water. Some nutrients are essential; insects lack the ability to synthesize them in their bodies and must obtain them from their diet or through symbiosis with beneficial organisms. Identification mechanisms being well developed in the system “phytophagous insect – plant” allow insects to successfully spread, multiply, and feed on certain plant species. The complex of hydrolytic enzymes in the insect intestine is one of the main targets for plant defense responses because these enzymes determine the availability of structural compounds for phytophagous insects. For this reason, enzymes in the insect intestine play a key role in the adaptation of insects to the pest resistance of fodder plants. For instance, when proteinase inhibitors are synthesized in a fodder plant as the result of induced insect resistance the complex of enzymes in an insect intestine might change negating the effect of these inhibitors. The development of co-adaptations due to interactions among species in food chains depends on a complicated constellation of conflicting relationships between consumers and food objects. The mechanisms of this influence may be rooted in the allelochemical interactions in the system “phytophagous insect – plant recipient”. Allelopathic interactions are among the most complex interactions because they are constituted by direct and indirect effects. Plants when damaged by phytophagous insects activate defense responses, which incorporate several mechanisms, including an increase in the concentration of secondary metabolites, many of which are phenolic compounds.The aim of the work is to describe the mechanisms of relationships in the system “phytophage-plant”. Conclusion. Management of processes of intra-water divergence of insect-phytophages in agrobiocoenoses in order to prevent the emergence of races and populations of pests adapted to live on initially resistant to them plant forms is possible in compliance with the transition to a targeted selection of agricultural crops for resistance to a complex of pests.

Interspecific Allelopathic Interaction Primes Direct and Indirect Resistance of Neighbor Plant in Agroforestry System

Agroforestry system with high biodiversity augments ecosystem stability and minimizes its vulnerability to environmental disturbances and disease. Deciphering the underlying mechanisms of interspecies allelopathic interactions in disease suppression in agroforestry offer a sustainable strategy for plant disease management. Here, we utilized Panax ginseng cultivated under Pinus koraiensis forests, where the occurrences of Alternaria leaf spot are low, as a research model to investigate the role of allelochemicals in disease suppression. Our findings demonstrate that foliar application of leachates from the needles of P. koraiensis effectively enhanced the resistance of P. ginseng against Alternaria leaf spot. Through GC-MS analysis, we identified and quantified endo-borneol as a key compound in the leachates of P. koraiensis, and validated its capacity to prime resistance in its neighbor P. ginseng. We discovered that endo-borneol not only directly activates defense-related pathways of P. ginseng to induce resistance, but also indirectly recruits its rhizospheric beneficial microbiota by enhancing the secretion of ginsenosides, thereby triggering induced systemic resistance (ISR). Importantly, the higher concentrations of endo-borneol from 10 to 100 mg/L demonstrated a stronger capacity to induce plant resistance and enhance root secretion to recruit more microbiota compared with the lower concentrations from 0.01 to 1 mg/L. Moreover, endo-borneol exhibited antifungal activity against the growth of the pathogen Alternaria panax when its concentrations exceeding 10 mg/L. These results reveal the multifaceted functions of allelochemical endo-borneol in disease suppression in agroforestry system and highlight its potential as an environmental-friendly compound for sustainable agriculture.

Allelopathic effects of leaves extract of parthenium hysterophorus l. On seed germination of three Rice varieties

This study investigates the allelopathic effects of Parthenium hysterophorus L. leaf and root extracts on the germination and growth of three rice varieties (Hira dhan, BRRI dhan-28, and BRRI dhan-29) in Bangladesh. Leaf and root extracts of P. hysterophorus were prepared at different concentrations and applied to rice seeds in a controlled environment. Results showed that low concentrations of the extracts inhibited seed germination and growth, with significant differences among rice varieties (p < 0.05). Hira dhan exhibited the most sensitivity, with germination rates as low as 42.86% under high extract concentrations. In contrast, BRRI dhan-29 showed a stimulatory effect, particularly at low concentrations. The shoot and root lengths of Hira dhan and BRRI dhan-29 were significantly inhibited at higher concentrations, while BRRI dhan-28 demonstrated growth stimulation. The fresh and dry weights of roots and shoots varied significantly among the varieties with the greatest inhibitory effect observed in BRRI dhan-29. These findings align with previous studies, suggesting that allelochemicals in P. hysterophorus, such as parthenin and phenolic acids, play a critical role in inhibiting rice growth. The study emphasizes the need for further research on allelopathic interactions and suggests that controlling P. hysterophorus at the crop emergence stage could mitigate its suppressive effects on rice growth. Bangladesh J. Bot. 53(3): 411-421, 2024 (September)

Physiological and proteomic responses of Posidonia oceanica to phytotoxins of invasive Caulerpa species

The invasive green algae Caulerpa taxifolia (M. Vahl) C. Agardh, 1817 and Caulerpa cylindracea Sonder, 1845 are widely diffused in the Mediterranean Sea, where they compete for space with the endemic seagrass Posidonia oceanica (Linnaeus) Delile, 1813, a keystone species in Mediterranean marine biodiversity. The present study aims to explore the possible effects of bioactive metabolites from the invasive algae on the seagrass, which may imply an allelopathic action. In particular, the study focuses on the effects of the algal alkaloid caulerpin and the sesquiterpene caulerpenyne. Changes in leaf growth, chlorophyll content, and leaf protein expression of P. oceanica genets under treatments were evaluated after 28 days of cultivation in mesocosms. Caulerpenyne strongly inhibited the growth of adult leaves and the formation of new ones, while inducing the elongation of the intermediate leaves and increased total chlorophyll content; on the contrary, caulerpin did not significantly influence leaf growth and the formation of new ones. A total of 107 differentially accumulated proteins common to the two treatments were also identified using the proteomic approach. Both molecules induced cells to maintain homeostasis, enhancing the amino acid metabolism or fatty acid biosynthesis. Despite these disruptions, P. oceanica demonstrated a more efficient response to stress induced by caulerpin, stimulating the biosynthesis of essential amino acids to maintain cellular homeostasis and mitigate damage caused by reactive oxygen species (ROS). Overall, obtained results supports the possible role of caulerpenyne, and not caulerpin, as an effector in allelopathic interactions among invasive Caulerpa species and P. oceanica in the Mediterranean.

Allelopathic Effect of a Chilean Strain of Karenia selliformis (Gymnodiniales, Dinoflagellata) on Phytoplankton Species.

Blooms of the dinoflagellate Karenia selliformis in Chile, often associated with massive fish kills, have been noted alongside other species from the Kareniaceae family, such as Karenia spp. and Karlodinium spp. However, the potential allelopathy impact of Chilean K. selliformis on other phytoplankton species remains unexplored. Here, we assessed the allelopathic effects of cell-free exudates from a Chilean K. selliformis strain on six phytoplankton strains representing diverse microalgal groups. The findings of these experiments offer valuable insights into the varied responses of both non-toxic and toxic microalgae to allelochemicals produced by a toxic microalga, showcasing the intricate and multifaceted nature of allelopathic interactions in microalgal communities. The study revealed species-dependent effects, with variable response in cell growth, photosynthetic efficiency (i.e., Fv/Fm), and intracellular reactive oxygen species (ROS) production. While certain strains exhibited significant growth inhibition in response to the allelochemicals, others demonstrated no apparent effect on cell proliferation, indicating varying sensitivity to specific allelochemicals or potentially distinct detoxification mechanisms. Similarly, the diverse effects on Fv/Fm highlight the complexity of allelopathic interactions, with some species showing reduced efficiency without alterations in intracellular ROS production, while others displayed increased ROS production alongside impaired photosynthesis.

Biotechnological frontiers in harnessing allelopathy for sustainable crop production.

Allelopathy, the phenomenon in which plants release biochemical compounds that influence the growth and development of neighbouring plants, presents promising opportunities for revolutionizing agriculture towards sustainability. This abstract explores the role of biotechnological advancements in unlocking the potential of allelopathy for sustainable crop production and its applications in agriculture, ecology, and natural resource management. By combining molecular, genetic, biochemical, and bioinformatic tools, researchers can unravel the complexities of allelopathic interactions and their potential for sustainable crop production and environmental stewardship. The development of novel management methods for weed control is getting a lot of attention with the introduction of new genetic technologies such as Gene drive, Transgene technologies, Gene silencing, Marker-assisted selection (MAS), and Clustered regularly interspaced short palindromic repeats (CRISPR-Cas9). By strengthening competitive characteristics these tools hold great promise for boosting crops' ability to compete with weeds. Considering recent literature, this review highlights the genetic, transcriptomics, and metabolomics approaches to allelopathy. Employing allelopathic properties in agriculture offer sustainable benefits like natural weed management, pest management, and reduced chemical pollution, but challenges include environmental factors, toxicity, regulatory hurdles, and limited resources. Effective integration requires continued research, regulatory support, and farmer education​. Also, we aimed to identify the biotechnological domains requiring more investigation and to provide the basis for future advances through this assessment.

Analysis of an intra- and interspecific interference model with allelopathic competition

In this paper, we propose an original model of two-microbial species competing for a single nutrient in the chemostat including general intra- and interspecific density-dependent growth rates with allelopathic interactions. Each species produces a toxin that affects the growth of other species as well as its own growth. The removal rates are distinct and include the specific death rate and the autotoxicity of each species. We establish an in-depth mathematical analysis by determining the multiplicity of all steady states of the three-dimensional system and their necessary and sufficient conditions of existence and local stability according to the operating parameters, which are the dilution rate and the inflowing concentration of the substrate. To describe the asymptotic behavior of the process according to these control parameters, we first determine theoretically the operating diagram. Using MATCONT software, these theoretical results are validated numerically but it reveals the cusp bifurcation that occurs by varying two parameters. The one-parameter bifurcation diagram in the dilution rate shows that there can be either transcritical or saddle-node bifurcations. Finally, we apply our results to a particular model in the literature without intra- and interspecific interference but with only allelopathic effects of the second species on the first species. We show that one of the coexistence steady states is locally exponentially stable when it exists, whereas in the literature they have not been able to demonstrate that the stability condition of this steady state is always fulfilled.

Germination Ecology and Ecology-based Management of Fimbristylis miliacea (L.) in Lowland Rice: A Review

Fimbristylis miliacea (L.) Vahl, commonly referred to as globe fringerush, member of the Cyperaceae family, is a significant and widespread sedge weed in rice cultivation. This C4 plant is characterized by its tall, annual or perennial growth, featuring a fibrous root system and smooth stems, often producing vigorous tillers reaching heights of 80-90 cm. Seedlings of F. miliacea typically emerge shortly after rice is planted, with flowering occurring within about a month, capable of producing a second generation within the same growing season. Found extensively throughout tropical regions, especially in lowlands, F. miliacea thrives in environments such as rice fields, shallow water along ditches, and streams, notably prevalent across South and Southeast Asia, as well as Australia. This weed presents enduring challenges across diverse agro-ecosystems due to its various ecotypes, prolific seed production, rapid germination, vigorous growth, strong competitive abilities and allelopathic interactions. Temperature is a critical factor significantly influencing seed germination of F. miliacea which exhibits non-deep physiological dormancy. Light is essential for the germination of this weed showing positive photoblastic behaviour. F. miliacea thrives in saturated soils but fails to emerge from depths greater than one cm, emphasizing the importance of shallow tillage to manage weed emergence effectively. Effective weed management hinges on a deep understanding of the factors that favour its emergence and establishment. Adopting the germination ecology-based practices such as tillage, stale seed bed preparation, optimal planting density, water management and nutrient management can significantly improve the management of F. miliacea.

Review of Allelopathy in Green Tides: The Case of Ulva prolifera in the South Yellow Sea.

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.

A native herbaceous community exerts a strong allelopathic effect on the woody range-expander Betula fruticosa

Abstract 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.

The allelopathic effects of Heterosigma akashiwo on Skeletonema costatum: Insights from gene expression and metabolomics analysis

The globally distributed harmful algal blooms (HAB) species, Heterosigma akashiwo, has been found to exhibit ichthyotoxicity. Previous studies have shown that H. akashiwo achieves a competitive edge during bloom occurrences by inhibiting the growth of a coexisting diatom, Skeletonema costatum, through allelopathy. However, the specific allelopathic mechanisms underlying the allelopathic effects of H. akashiwo on S. costatum remain unknown. To bridge this gap, our study utilized a combination of quantitative real-time PCR and metabolomics to examine the allelopathic processes of H. akashiwo on S. costatum. Our results demonstrate that the growth of S. costatum is hindered when co-cultured with H. akashiwo (initial cell concentration, 2 × 104 cell/mL). Gene expression investigation showed a substantial reduction in the mRNA levels of cytochrome b6, ribulose bisphosphate carboxylase large chain, and silicon transporter in S. costatum when grown in co-culture conditions. Furthermore, metabolic pathway analysis suggested that the allelopathic effects of H. akashiwo disrupted several vital metabolic pathways in S. costatum, including a reduction in purine and pyrimidine metabolism and an increase in fatty acid biosynthesis. Our investigation has revealed the intricate and substantial involvement of allelopathy in the formation of H. akashiwo blooms, demonstrating the complexity of the allelopathic interaction between H. akashiwo and S. costatum. These insights also contribute significantly to our understanding of the dynamics within HAB species.

Evidence of Allelopathy among Selected Moss Species with Lettuce and Radish

There is limited evidence on bryophyte-tracheophyte allelopathic interactions. Even less is known about such relationships among commercially important plants and mosses. With the aim of screening such interactions, various extract concentrations of nine different mosses were tested on the seed germination and seedlings, i.e., hypocotyl elongation and total chlorophyll content of lettuce and radish. The allelopathic effects are documented to be pairwise (moss-vegetable) and species-specific. Based on the results, the extracts of Leucodon sciuroides and Dicranum polysetum are not harmful to lettuce and radish. Lower extract concentrations of Leucodon sciuroides and Ctenidium molluscum have a positive effect on lettuce development, while those of Thuidium delicatulum, Ctenidium molluscum, and Dicranum polysetum showed to be effective on radish. Further, negative effects were noticed when applying higher extract concentration of Abietinella abietina, Isothecium alopecuroides, Dicranum polysetum, and Racomitrium elongatum to lettuce and Isothecium alopecuroides to radish. The dataset presented in this study offers numerous possibilities for further target pest/vegetable type applications since some of the moss extracts are shown to be positive, negative, or indifferent to the tested features in lettuce and radish.

Effects of stochastic perturbations on a phytoplankton allelopathy competitive system

In this paper, we investigate stochastic models of two species competitive phytoplankton system with allelopathic interaction. We construct stochastic models from deterministic models by introducing three different stochastic perturbations to the equations. For the first model, we prove that this model is asymptotically stable in probability at three different equilibrium points. It is also shown that the system is positively recurrent under some conditions. For the second model, we study the extinction, existence of positive recurrence and global asymptotic stability under some sufficient conditions. For the last system, almost sufficient and necessary conditions for global asymptotic stability, the existence of positive recurrence and extinction of each population are established. In addition, using a suitable stochastic Lyapunov method, we prove that there is a unique solution to three models, we also discuss the ultimate boundedness of the three stochastic systems. Moreover, some numerical simulations are introduced to illustrate our mathematical results. We show that stochastic models still retain the desirable stability of their deterministic counterparts if stochastic perturbations are relatively small.

Allelopathic Responses of Crop Species to Chromolaena odorata Root Exudate Extracts: A Comprehensive Study

This study investigates the allelopathic effects of root exudate extracts from Chromolaena odorata on the germination and growth of six crop species. The results reveal variable sensitivity among the species, with the control treatment consistently exhibiting superior germination percentages. Initially, some species, including Abelmoschus esculentus (okra), Solanum lycopersicum (tomato), and Cicer arietinum (chickpea), experienced a substantial decline in germination, indicating a potential inhibitory effect of the exudates, although partial recovery was observed in subsequent treatments. Phaseolus vulgaris (common bean) displayed a moderate decrease, while Zea mays (corn) exhibited the most significant drop in germination rates, albeit with slight recovery at higher concentrations of exudates. Conversely, Cucumis sativus (cucumber) appeared least affected by the exudates. Moreover, all species demonstrated reductions in shoot and root lengths with increasing concentrations of exudates. Chlorophyll content analysis revealed a significant reduction across most treatments, highlighting concerns regarding photosynthetic efficiency and overall plant health. The species-specific response to root exudates suggests varying metabolic or adaptive mechanisms among crops. Additionally, malondialdehyde (MDA) levels, indicative of oxidative stress, varied among species, with A. esculentus and P. vulgaris showing a dose-dependent increase, while S. lycopersicum displayed a peak at intermediate treatment levels. Z. mays exhibited marginal elevation in MDA content, potentially indicating the presence of protective compounds within the exudates. Conversely, C. arietinum and C. sativus showed a steady increase in MDA, suggesting limited mitigation of allelopathic effects. These findings feature the complexity of allelopathic interactions and highlight the need for further research into active compounds and their modes of action to develop sustainable weed management strategies while safeguarding crop health. Understanding these dynamics is crucial for maximizing the potential benefits of allelopathy in agriculture.

Physiological and molecular insights into the allelopathic effects on agroecosystems under changing environmental conditions.

Allelopathy is a natural phenomenon of competing and interfering with other plants or microbial growth by synthesizing and releasing the bioactive compounds of plant or microbial origin known as allelochemicals. This is a sub-discipline of chemical ecology concerned with the effects of bioactive compounds produced by plants or microorganisms on the growth, development and distribution of other plants and microorganisms in natural communities or agricultural systems. Allelochemicals have a direct or indirect harmful effect on one plant by others, especially on the development, survivability, growth, and reproduction of species through the production of chemical inhibitors released into the environment. Cultivation systems that take advantage of allelopathic plants' stimulatory/inhibitory effects on plant growth and development while avoiding allelopathic autotoxicity is critical for long-term agricultural development. Allelopathy is one element that defines plant relationships and is involved in weed management, crop protection, and microbial contact. Besides, the allelopathic phenomenon has also been reported in the forest ecosystem; however, its presence depends on the forest type and the surrounding environment. In the present article, major aspects addressed are (1) literature review on the impacts of allelopathy in agroecosystems and underpinning the research gaps, (2) chemical, physiological, and ecological mechanisms of allelopathy, (3) genetic manipulations, plant defense, economic benefits, fate, prospects and challenges of allelopathy. The literature search and consolidation efforts in this article shall pave the way for future research on the potential application of allelopathic interactions across various ecosystems.

Allelopathic Effects of Ageratum conyzoides Root Exudates on Germinability of Selected Crops: A Comparative Analysis

This study investigates the allelopathic effects of aqueous root exudate extracts of Ageratum conyzoides on the germination, shoot length, and root length of various agricultural crops. The study reveals how different species respond uniquely to varying concentrations, uncovering complex dynamics in crop-allelopathic interactions. The germination analysis reveals distinct sensitivities among the tested crops. C. sativus demonstrates resilience, displaying minimal germination reduction even at higher exudate concentrations. C. arietinum exhibits moderate susceptibility, while Z. mays emerge as the most sensitive crop, displaying a profound reduction in germination. L. esculentum and P. vulgaris also exhibit sensitivity, with adverse impacts on germination rates. A. esculentus consistently shows reduced germination rates with increasing exudate concentrations. Shoot length dynamics show that all crops experience greatest elongation without A. conyzoides root exudates, suggesting inhibition of growth by these exudates. Shoot growth declines with higher exudate concentrations across most crops, with varying sensitivities. C. sativus consistently decreases, while C. arietinum, Z. mays, and P. vulgaris show concentration-dependent inhibition. S. lycopersicum significantly reduces shoot elongation, and A. esculentus remains consistently sensitive. Root length patterns further elucidate the allelopathic effects. Responses vary across species and concentrations. A. esculentus roots thrive at lower concentrations but decline at higher ones. S. lycopersicum shows initial reduction, significant decline, followed by recovery. Z. mays and C. arietinum exhibit fluctuating responses. P. vulgaris consistently grows, while C. sativus persistently displays reduced root elongation. These findings highlight the complex and species-specific allelopathic interactions between A. conyzoides and agricultural crops, emphasizing the need for a comprehensive understanding of these dynamics for effective crop management in A. conyzoides-infested areas.

Effect of Euphorbia hirta Leaf and Root Extracts on the Early Growth of Cucurbit Crops

The research investigates the allelopathic influence of Euphorbia hirta extracts on the germination and seedling development of various cucurbit species, including Bottle gourd (Sp. A), Winter melon (Sp. B), Ridged gourd (Sp. C), Sponge gourd (Sp. D), Bitter gourd (Sp. E), Snake gourd (Sp. F), Muskmelon (Sp. G), and Pumpkin (Sp. H). The experimental design incorporated the use of both aqueous and methanol extracts of E. hirta, applied at different concentrations, with distilled water employed as the control. The findings reveal that the methanolic extract of E. hirta significantly impedes both the germination process and the subsequent growth of seedlings for all cucurbit species tested. For instance, at 12 days post-treatment, control groups exhibited high germination percentages (78%, 90.67%, 95.33% and 90% for Sp. A, Sp. C, Sp. D and Sp. E, respectively), which drastically declined with a 20% methanol extract concentration (23.33%, 18.33%, and 17.67% and 18.33% for the same species, respectively). Similarly, shoot and root length measurements indicated that higher concentrations of both extracts suppressed growth, with methanol extract showing a stronger inhibitory effect compared to the aqueous extract. Interestingly, Lower extract concentrations occasionally boosted shoot growth, revealing a hormetic effect. This two-fold response, notably in Pumpkin and Snake Gourd, illuminates the complexity of allelopathic interactions. The study suggests E. hirta extracts could serve as eco-friendly herbicides, urging further research to isolate their active components. This could lessen synthetic herbicide use, promoting sustainable agriculture and environmental protection.