Ultrasonic-assisted extraction of total flavonoids from Zanthoxylum bungeanum residue and their allelopathic mechanism on Microcystis aeruginosa.

Water eutrophication has emerged as a pressing concern for massive algal blooms, and these harmful blooms can potentially generate harmful toxins, which can detrimentally impact the aquatic environment and human health. Consequently, it is imperative to identify a safe and efficient approach to combat algal blooms to safeguard the ecological safety of water. This study aimed to investigate the procedure for extracting total flavonoids from Z. bungeanum residue and assess its antioxidant properties. The most favorable parameters for extracting total flavonoids from Z. bungeanum residue were a liquid-solid ratio (LSR) of 20 mL/g, a solvent concentration of 60%, an extraction period of 55 min, and an ultrasonic temperature of 80 °C. Meanwhile, the photosynthetic inhibitory mechanism of Z. bungeanum residue extracts against M. aeruginosa was assessed with a particular focus on the concentration-dependent toxicity effect. Z. bungeanum residue extracts damaged the oxygen-evolving complex structure, influenced energy capture and distribution, and inhibited the electron transport of PSII in M. aeruginosa. Furthermore, the enhanced capacity for ROS detoxification enables treated cells to sustain their photosynthetic activity. The findings of this study hold considerable relevance for the ecological management community and offer potential avenues for the practical utilization of resources in controlling algal blooms.

Phytochemical profiling and allelopathic effect of garlic essential oil on barnyard grass (Echinochloa crusgalli L.).

In agriculture, barnyard grass (Echinochloa crusgalli L.) is one of the most harmful weeds in rice fields now. In order to identify active ingredients which had inhibiting effect on barnyard grass (Echinochloa crusgalli L.), we evaluated several possible natural plant essential oils. Essential oils from twelve plant species showed inhibitory activity against barnyard grass seedlings and root length. The garlic essential oil (GEO) had the most significant allelopathic effect (EC50 = 0.0126 g mL-1). Additionally, the enzyme activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) increased during the first 8 hours of treatment at a concentration of 0.1 g mL-1 and then declined. The activities of CAT, SOD and POD increased by 121%, 137% and 110% (0-8h, compared to control), and decreased (8-72h, compared to the maximum value) by 100%, 185% and 183%, respectively. The total chlorophyll content of barnyard grass seedlings decreased by 51% (0-72h) continuously with the same dosage treatment. Twenty constituents of GEO were identified by gas chromatography-mass spectrometry, and the herbicidal activity of two main components (diallyl sulfide and diallyl disulfide) was evaluated. Results showed that both components had herbicidal activity against barnyard grass. GEO had a strong inhibitory effect (~88.34% inhibition) on barnyard grass growth, but safety studies on rice showed it did not have much inhibitory effect on rice seed germination. Allelopathy of GEO provide ideas for the development of new plant-derived herbicides.

The latitudinal and longitudinal allelopathic patterns of an invasive alligator weed (Alternanthera philoxeroides) in China.

Allelopathy has been considered a good explanation for the successful invasion of some invasive plants. However, the real latitudinal and longitudinal allelopathic effects on native species have rarely been documented since many exotics have spread widely. We conducted a Petri dish experiment to determine the latitudinal and longitudinal allelopathic patterns of an invasive alligator weed (Alternanthera philoxeroides) on a common crop (Lactuca sativa) in China, and find what determines the allelopathic intensity. The results showed that the allelopathic effects of A. philoxeroides increased with the latitude while decreased with the longitude. This indicated that A. philoxeroides used its allelopathy to gain competitive advantages more in its recent invaded communities than that in its early invaded ones as A. philoxeroides is expanding from southeast China to northwest China. Furthermore, we found that the allelopathic intensity of A. philoxeroide was negatively correlated to the leaf contents of soluble carbohydrate (SC), carbon (C) and nitrogen (N), but that was positively correlated to the leaf contents of soluble protein (SP), free amino acids (FAA), plant polyphenol (PP), phosphorus (P) and potassium (K). These results suggested that the allelopathic intensity of A. philoxeroide was more determined by the limited P and K nutrients as well as the intermediate allelochemicals (SP, FAA, PP) rather than the unlimited C, N and SC. Thus, we can speculate that the negative or positive effects of plant aqueous extracts are a function of not only the extract concentrations but also the trade-offs between inhibition and promotion of all components in the extracts. Then we could reduce the allelopathic effects of A. philoxeroide by controlling the component contents in the plant tissues, by fertilization or other managements, especially in the plant recent invaded communities.

Phytochemistry, allelopathy and anticancer potentiality of Withania somnifera (L.) Dunal (Solanaceae).

Withania somnifera is a wild plant that shows great activity and safety against several human diseases. The current research explored the plant's chemical composition and allelopathic effects on Rumex dentatus (recipient plant). Moreover, anticancer activity is also tested against four types of human cancer cell lines. Chemical analysis of W. somnifera showed a high percentage of saponins and tannins, while glycosides, alkaloids, and flavonoids occurred in the second order. Results of the allelopathic experiments revealed significant inhibition of the R. dentatus plumule and radicle lengths as well as their relative dry weights. In addition, significant reductions in some primary metabolites of R. dentatus, like non-reducing and total sugar as well as soluble proteins, were determined. Cytotoxic potentiality of W. somnifera was also proved against four different cancer lines, namely; human hepatocellular carcinoma cell line (HepG2), human non-small cell lung cancer cell line (A549), human breast cancer cell line (MCF7), and colon cancer cell line (CaCo2) with IC50 value of about 38, 19, 27, and 24 𝜇g/ml, respectively.

Physiological, biochemical and phytohormone responses of Elymus nutans to α-pinene-induced allelopathy.

The α-pinene is the main allelochemical of many weeds that inhibit the growth of Elymus nutans, an important forage and ecological restoration herbage. However, the response changes of α-pinene-induced allelopathy to E. nutans is still unclear. Here, we investigated the physiological, biochemical and phytohormone changes of E. nutans exposed to different α-pinene concentrations. The α-pinene-stress had no significant effect on height and fresh weight (FW) of seedlings. The water-soluble proteins, the soluble sugars and proline (Pro) strengthened seedlings immunity at 5 and 10 µL L-1 α-pinene. Superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased at 5 µL L-1 α-pinene to resist stress. APX reduced the membrane lipid peroxidation quickly at 10 µL L-1 α-pinene. The high-activity of peroxidase (POD), APX along with the high level of GSH contributed to the cellular redox equilibrium at 15 µL L-1 α-pinene. The POD, glutathione reductase (GR) activity and glutathione (GSH) level remained stable at 20 µL L-1 α-pinene. The changes in antioxidant enzymes and antioxidants indicated that E. nutans was effective in counteracting the harmful effects generated by hydrogen peroxide (H2O2). The α-pinene caused severe phytotoxic effects in E. nutans seedlings at 15 and 20 µL L-1. Endogenous signal nitric oxide (NO) and cell membrane damage product Pro accumulated in leaves of E. nutans seedlings at 15 and 20 µL L-1 α-pinene, while lipid peroxidation product malondialdehyde (MDA) accumulated. The chlorophylls (Chls), chlorophyll a (Chl a), chlorophyll b (Chl b) content decreased, and biomass of seedlings was severely inhibited at 20 µL L-1 α-pinene. The α-pinene caused phytotoxic effects on E. nutans seedlings mainly through breaking the balance of the membrane system rather than with reactive oxygen species (ROS) productionat 15 and 20 µL L-1 α-pinene. Additionally, phytohormone levels were altered by α-pinene-stress. Abscisic acid (ABA) and indole acetic acid (IAA) of E. nutans seedlings were sensitive to α-pinene. As for the degree of α-pinene stress, salicylic acid (SA) and jasmonic acid (JA) played an important role in resisting allelopathic effects at 15 µL L-1 α-pinene. The ABA, Zeatin, SA, gibberellin 7 (GA7), JA and IAA levels increased at 20 µL L-1 α-pinene. The α-pinene had a greatest impact on ABA and IAA levels. Collectively, our results suggest that E. nutans seedlings were effective in counteracting the harmful effects at 5 and 10 µL L-1 α-pinene, and they were severely stressed at 15 and 20 µL L-1 α-pinene. Our findings provided references for understanding the allelopathic mechanism about allelochemicals to plants.

Changes in Toxin Production, Morphology and Viability of Gymnodinium catenatum Associated with Allelopathy of Chattonella marina var. marina and Gymnodinium impudicum.

Allelopathy between phytoplankton organisms is promoted by substances released into the marine environment that limit the presence of the dominating species. We evaluated the allelopathic effects and response of cell-free media of Chattonella marina var. marina and Gymnodinium impudicum in the toxic dinoflagellate Gymnodinium catenatum. Additionally, single- and four-cell chains of G. catenatum isolated from media with allelochemicals were cultured to evaluate the effects of post exposure on growth and cell viability. Cell diagnosis showed growth limitation and an increase in cell volume, which reduced mobility and led to cell lysis. When G. catenatum was exposed to cell-free media of C. marina and G. impudicum, temporary cysts and an increased concentration of paralytic shellfish toxins were observed. After exposure to allelochemicals, the toxin profile of G. catenatum cells in the allelopathy experiments was composed of gonyautoxins 2/3 (GTX2/3), decarcarbamoyl (dcSTX, dcGTX2/3), and the sulfocarbamoyl toxins (B1 and C1/2). A difference in toxicity (pg STXeq cell−1) was observed between G. catenatum cells in the control and those exposed to the filtrates of C. marina var. marina and G. impudicum. Single cells of G. catenatum had a lower growth rate, whereas chain-forming cells had a higher growth rate. We suggest that a low number of G. catenatum cells can survive the allelopathic effect. We hypothesize that the survival strategy of G. catenatum is migration through the chemical cloud, encystment, and increased toxicity.

Overview of Allelopathic Potential of Lemna minor L. Obtained from a Shallow Eutrophic Lake.

Allelopathy is an interaction that releases allelochemicals (chemicals that act allelopathically) from plants into the environment that can limit or stimulate the development, reproduction, and survival of target organisms and alter the environment. Lemna minor L. contains chemicals that are allelopathic, such as phenolic acids. Chemical compounds contained in L. minor may have a significant impact on the development and the rate of multiplication and lead to stronger competition, which may enhance the allelopathic potential. Allelopathic potential may exist between L. minor and C. glomerata (L) Kütz. because they occupy a similar space in the aquatic ecosystem, have a similar preference for the amount of light, and compete for similar habitat resources. L. minor and C. glomerata can form dense populations on the water surface. Allelopathy can be seen as a wish to dominate one of the plants in the aquatic ecosystem. By creating a place for the development of extensive mats, an interspecific interaction is created and one of the species achieves competitive success. It is most effective as a result of the release of chemicals by macrophytes into the aquatic environment. Therefore, allelopathy plays a significant role in the formation, stabilization, and dynamics of the structure of plant communities.

Changes in activities of antioxidant enzymes in radish (Raphanus sativus) seedlings in response to allelopathic effect of safflower (Carthamus tinctorius)

Abstract ROS (Reactive Oxygen Species) production is a usual plant reaction to environmental stresses such as allelopathy. Plants possess antioxidant enzymes to scavenge cells and resist against the ROS. This study was conducted to evaluate changes in antioxidant enzymes (CAT, GPX, APX) in radish seedlings in response to allelopathic effect of safflower root and shoot residues grown under normal irrigation and drought stress. Safflower allelopathic effect led to an increase in antioxidant enzymes activities. GPX activity increased more than CAT and APX. Radish seedlings exposed to safflower residue grown under drought stress showed more antioxidant enzymes activities. Root residues enhanced the activities of antioxidant enzymes greater than shoot. Seedlings exposed to root residues grown under drought stress had the highest level of antioxidant enzymes activities.

Phytotoxicity of plant extracts of Vismia japurensis cultivated in vivo and in vitro / Fitotoxicidade de extratos de plantas de Vismia japurensis cultivadas in vivo e in vitro

Plants that produce secondary metabolites with allelopathic activity or phytotoxicity can be biotechnologically important, serving as sources of allelochemicals, and thus contributing to the agroindustrial sector. Vismia japurensis (Hypericaceae) is an Amazonian species that grows in clumps called vismiais, from which most other plants are absent. Accordingly, the objective of this study was to identify possible phytotoxicity effects of hexane and methanol extracts of Vismia japurensis leaves and branches in vivo and from seedlings grown in vitro on Lactuca sativa. In addition, fresh and dry leaves were assayed by the sandwich method in order to determine their ability to release allelochemicals. The hexanic extract from in vitro seedlings reduced germination by 10%, while the methanol extract produced a 16% reduction in germination speed. Root growth of Lactuca sativa was inhibited by 64.7% when subjected to hexane leaf extract, by 39.3% under the influence of hexane branch extract, and by 96.09% for in vitro seedling hexanic extract. When analysed by thin layer chromatography and 1H nuclear magnetic resonance, extracts showed evidence of terpenes, anthraquinones and flavonoids, with greater intensity of signals in the aromatic region of in vitro seedling hexanic extract. Clearly, Vismia japurensis has a high biotechnological potential in terms of the production of substances of low polarity with capacity to interfere in plant development.

Plantas que produzem metabólitos secundários com atividade alelopática ou fitotóxica podem ser biotecnologicamente importantes, servindo como fontes de aleloquímicos e, assim, contribuindo para o setor agroindustrial. Vismia japurensis (Hypericaceae) é uma espécie amazônica que cresce em grupos, formando vismiais. Assim, o objetivo deste estudo foi identificar possíveis efeitos fitotóxicos de extratos hexânicos e metanólicos de folhas e ramos de Vismia japurensis in vivo e de plântulas cultivadas in vitro sobre Lactuca sativa. Além disso, folhas frescas e secas foram analisadas pelo método sanduíche, a fim de determinar sua capacidade de liberação de aleloquímicos. O extrato hexânico de plântulas in vitro reduziu a germinação em 10% e o extrato metanólico promoveu uma redução de 16% na velocidade de germinação. O crescimento radicular de Lactuca sativa foi inibido em 64,7% quando submetido ao extrato hexânico das folhas, em 39,3% sob influência do extrato hexânico dos galhos e em 96,09% para o extrato de hexânico das plântulas in vitro. Quando analisados por cromatografia em camada delgada e ressonância magnética nuclear de 1H, os extratos mostraram evidências de terpenos, antraquinonas e flavonoides, com maior intensidade de sinais na região aromática do extrato hexânico das plântulas in vitro. Assim, Vismia japurensis possui elevado potencial biotecnológico em termos de produção de substâncias de baixa polaridade com capacidade de interferência no desenvolvimento de plantas.

Short-term changes related to autotetraploidy in essential oil composition of Eucalyptus benthamii Maiden & Cambage and its applications in different bioassays.

Some forest trees have been polyploidized to improve their traits and to supply new germplasms for breeding programs. As trees have a long juvenile stage, the early characterization of the chromosome set doubling effects is crucial for previous selection. Thus, we aimed to characterize the chemical variability of essential oils from diploid and autotetraploid germplasms (autotetraploid A and B) of Eucalyptus benthamii, as well as to evaluate their larvicidal and allelopathic effects. Autotetraploid A showed a higher essential oil yield than diploid and autotetraploid B, which did not differ quantitatively. Aromadendrene, viridiflorol and α-pinene were the major compounds in the diploid essential oil. In contrast, compounds were present in autotetraploids, such as 1,8-cineole, limonene, α-terpineol, and α-terpinyl-acetate. Essential oils from the diploid at 50-200 ppm were twice as larvicidal than those from autotetraploids against Aedes aegypti larvae. Considering the phytotoxicity bioassays using Lactuca sativa, essential oils from both ploidy levels affected root growth. Moreover, the essential oils inhibited shoot growth at all concentrations tested (187.5; 375; 750; 1500; and 3000 ppm). Autotetraploid A and B had the same effect on shoot growth as glyphosate. The essential oils had no cytogenotoxic effect on root meristematic cells of L. sativa, whereas phytotoxic potential was identified mainly in shoot growth. This work demonstrated a dramatic change in secondary metabolism (terpene composition) related to an increase in the ploidy level in Eucalyptus germplasms. In addition, we report the novelty of the chemical composition of essential oils among germplasms and their potential use as larvicidal and post-emergence weed control agents.

Effect of plant origin and phenological stage on the allelopathic activity of the invasive species Oxalis pes-caprae.

PREMISE: Invasion processes involve several mechanisms, some of which have received little attention. Allelopathy has been invoked as an invasion driver according to the novel weapon hypothesis (NWH), and polyploidization can also be an important factor for invasion success. However, very few studies have addressed both topics together. We analyzed the allelopathic effect of the polyploid Oxalis pes-caprae, an invader in mediterranean-climate areas worldwide, from different origins and ploidy levels (native: South Africa; invaded: Chile, Australia, California, and the Mediterranean Basin) on Lactuca sativa as a model species. METHODS: We measured seed germination, initial plant height, and aboveground and belowground biomass of Lactuca grown in field soil mixed with Oxalis material and with or without activated carbon in a common garden experiment. We performed the experiment twice, when Oxalis was vigorous and when senescent. RESULTS: Vigorous plants of Oxalis tended to reduce Lactuca germination, but both vigorous and senescent Oxalis plants increased Lactuca biomass, probably due to an increase in nutrients provided by plant material. The highest increase in Lactuca traits occurred with Oxalis plants from the Iberian Peninsula. Allelopathy only happened when Oxalis was senescent and was especially strong with plants from Chile. CONCLUSIONS: Although we did not find broad evidence for the NWH considering all areas together, we reported differences in the allelopathic potential of Oxalis plants depending on their origin. These results highlight the independent evolution of invasiveness traits in distant introduced ranges and the importance of the invaders' origin when testing hypotheses about invasion drivers.

Survey of the allelopathic potential of Mediterranean macroalgae: production of long-chain polyunsaturated aldehydes (PUAs).

Chemical interactions between macroalgae and other organisms play an important role in determining species compositions and dominance patterns, and can explain the widespread success of some species in establishing their predominant populations in a specific coastal area. Allelopathy could act as a self-regulatory strategy of the algal community, being not only a succession regulator but also an active mechanism maintaining the species diversity especially in a delimited environment, such as the benthic ecosystem. Polyunsaturated aldehydes (PUAs) are among the most studied allelopathic compounds and are commonly released into the aquatic environment by different phytoplankton species in response to environmental stressors (e.g. wounding, grazing, or competition for nutrients). Diatom-released PUAs were observed to affect phytoplankton community dynamics and structure, and showed inhibitory effects on the reproduction and development of marine invertebrates. As for macroalgae, there are only a few reports that attest to the production of PUAs, and mostly refer to Ulva spp. In this study, the production of PUAs by several Mediterranean macroalgae was investigated at different sampling times, aiming at providing the first evidence of potential allelochemical activity. Results highlighted the potential production by macroalgae of a variety of aldehydes, among which some have never reported so far. Some species (i.e. D. polypodioides and U. cf. rigida) were found to produce higher PUAs amounts than others, and even a wider variety of structures (e.g. length of the carbon chain); these species might exert strong effects on epiphytic species or other organisms of the benthic community, especially considering the differential sensitivities of the various taxa. A high dPUA concentration (order of µM) potentially due to the release of PUAs by algal species was found, and might affect the population dynamics of the epiphytic organisms (e.g. microalgae, meiofauna), of grazers, as well as of the microbial community.

Prevalence of Diterpenes in Essential Oil of Euphorbia mauritanica L.: Detailed Chemical Profile, Antioxidant, Cytotoxic and Phytotoxic Activities.

Plants belonging to Euphorbia L. genus are considered very interesting from a medicinal point of view due to their diverse metabolites and bioactivities. The essential oil (EO) of Euphorbia mauritanica L. is not studied up to date. Therefore, the present study aimed to explore the chemical profile of this EO and evaluate its antioxidant, cytotoxic, and allelopathic potentialities. The EO was extracted from the whole plant via hydrodistillation and then, analyzed by gas chromatography/mass spectrometry (GC/MS). The correlation of E. mauritanica with the other Euphorbia plants was established using chemometric analysis. The antioxidant activity was determined based on scavenging of the free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The anti-proliferation of the EO on the Hep G2 and MCF-7 cells was evaluated. Finally the allelopathic activity of the EO was assessed against the two noxious weeds, Dactyloctenium aegyptium and Urospermum picroides. Forty-one compounds were identified using GC/MS analysis, with an abundance of terpenoids (91.54 %) that were categorized into mono- (30.75 %), sesqui- (15.23 %), and diterpenes (45.56 %). Interestingly, the results revealed the preponderance of diterpenoid constituents although they are rarely found in the EOs of the plant kingdom. The major compounds were (3E)-cembrene A (18.66 %), verticiol (17.05 %), limonene (7.91 %), eucalyptol (7.26 %), α-pinene (5.61 %), neo-cembrene A (3.52 %), kaur-16-ene (3.24 %), and cembrene (3.09 %). The EO showed moderate antioxidant activity where it attained IC50 values of 83.34 and 64.21 µg mL-1 for DPPH and ABTS compared to 23.01 and 19.23 µg mL-1 for ascorbic acid as standard, respectively. The EO exhibited very weak cytotoxic effect on MCF-7 and Hep G2 cells. The EO showed significant allelopathic activities against the weeds D. aegyptium and U. picroides in a concentration-dependent manner. EO was found more effective against U. picroides than D. aegyptium with IC50 values of 0.79, 0.45, and 0.67 mg mL-1 and 1.17, 0.55, and 1.08 mg mL-1 for germination, root, and shoot growth, respectively. Due to the high content of diterpenes in E. mauritanica, further study is recommended for more characterization of pure forms of the identified diterpenes as well as evaluating their bioactivity either solely or synergistically.

Chemical composition and phytotoxicity of essential oil from invasive plant, Ambrosia artemisiifolia L.

Essential oils have been evaluated as appropriate phytotoxins with mechanisms of action that are different from those of synthetic herbicides applied in weed management activities, but little is known about the effect of Ambrosia artemisiifolia essential oil (EO) on weeds. Here, the chemical composition of A. artemisiifolia EO was analyzed using a Gas Chromatography-Mass Spectrometry system. and the phytotoxic activities of the EO against monocot (Poa annua, Setaria viridis) and dicot (Amaranthus retroflexus, Medicago sativa) species are evaluated under laboratory and green-house conditions for the first time. The EO was rich in sesquiterpenes (62.51%), with germacrene D (32.92%), ß-pinene (15.14%), limonene (9.90%), and caryophyllene (4.49%) being the major compounds based on Gas Chromatography-Mass Spectrometry analysis results. A. artemisiifolia EO inhibited seed germination and seedling development significantly in the tested species even at low concentrations (0.25 mg mL-1). In addition, bioassay results for the activities of superoxide dismutase (SOD) and peroxidase (POD) increased and then decreased with an increase in EO concentration. Unlike the enzymatic activity, root cell viability declined significantly in the tested weeds in all EO treatments. Besides, a foliar spray experiment resulted in visible injury in leaves and a decrease in chlorophyll content and eventually led to wilting of all tested weeds. The EO (0.25-5.00 mg mL-1) altered Allium cepa root tip cells with a decline in mitotic index and an increase in chromosomal aberrations after 24 h treatment. The cytotoxic evaluation confirmed the mitotic inhibitory effect of EO, although the intensity varied under different concentrations. According to the results, A. artemisiifolia EO has the potential applications as a natural herbicide owing to its phytotoxic activity; which also helps to explain their potential involvement in allelopathic interaction of volatile compounds present in the EO that facilitate the invasion success of the exotic species.

Potential risks of nicotine on the germination, growth, and nutritional properties of broad bean.

This study evaluated the allelopathy, uptake and accumulation, and potential agricultural and food safety risks of nicotine in broad bean (Vicia faba L.) during seed germination and seedling growth. Nicotine stress has an allelopathic inhibitory effect on seeds and a hormesis effect on germinated seeds and seedlings, which has an enhancement effect (<50 mg kg-1) and an inhibition effect (>100 mg kg-1) on the germinated seeds and an enhancement effect (<100 mg kg-1) and an inhibition effect (>200 mg kg-1) on the seedlings. Exogenous nicotine can be absorbed by broad bean roots from nicotine-contaminated soil and accumulated in the main organs of the seedlings, especially the leaves, which exceeded the maximum residue level (0.03 mg kg-1 DW) at 50 mg kg-1. Moreover, nicotine resulted in a bitter taste in the edible broad bean leaves, disrupting the balance of basic nutritional properties, decreasing sucrose, and increasing bitter substances such as choline and procyanidin. These results demonstrated that residual nicotine in the soil not only poses potential risks to sustainable agricultural development but also a food safety risk for consumers. The present study provides insight into the potential risks of nicotine in agroecosystems.

Chemical composition of the volatile oil of Croton glandulosus Linnaeus and its allelopathic activity.

Several essential oils have allelochemicals with phytotoxic effects. Croton species are producers of secondary metabolites with biological potential. In the present study, chemical composition of the essential oil extracted from aerial parts of Croton glandulosus Linnaeus was evaluated by gas chromatography and the phytotoxicity of the oil on Lactuca sativa seeds was evaluated for the first time. The yield of the essential oil was 0.12% (v/w). Chromatographic analysis allowed the identification of 97.49% of the total compounds present in the oil. Sesquiterpenes were found to be the predominant constituents of the volatile oil, with ß-caryophyllene (53.24%) being the major compound. Treatment with 0.1%-1% (v/v) of the essential oil inhibited the development of the hypocotyl and radicle of L. sativa to a greater extent compared to the inhibition of seed germination, demonstrating the phytotoxic effect of the oil.

Allelopathy of uncomposted and composted invasive aster (Ageratina adenophora) on ryegrass.

In many areas invaded by Ageratina adenophora, the piles of A. adenophora residue need to be safely treated and economically utilized. To explore a new potential use for these residues, on-site aerobic composting, seed germination test and greenhouse experiment were conducted to compare the phytotoxic allelochemicals in uncomposted and composted A. adenophora plants (UA and CA, respectively) and their influence on ryegrass seed germination and seedling growth. The phytotoxicants 4,7-dimethyl-1-(propan-2-ylidene)-1,4,4a,8a-tetrahydronaphthalene-2,6(1H,7H)-dione (DTD) and 6-hydroxy-5-isopropyl-3,8-dimethyl-4a,5,6,7,8,8a-hexahydronaphthalen-2(1 H)-one (HHO) in UA decreased by 10.09 and 11.01 times in CA on average, respectively. Aqueous extracts of CA increased the seed germination rate, root dehydrogenase activity, leaf chlorophyll content and nitrate reductase activity; those of UA behaved oppositely. Compared with chemical fertilizers (CF), CF + CA promoted plant growth, increased plant nutrient uptake, and resulted in higher soil available nutrients, enzyme activity and microbial biodiversity, whereas CA alone had similar or better influences on plants and soils than CF. The predominant bacterial and fungal composition was the same in the soils supplied with CA and CF + CA. Therefore, on-site aerobic composting eliminated the phytotoxicity of CA and provided a new, simple and economical approach for the potential use of A. adenophora biomass as a plant- and soil-friendly organic fertilizer.

Growth of Microcystisstrains isolated from environments with the presence and absence of submerged macrophytes in coexistence with Ceratophyllum demersum

Cyanobacterial blooms can cause severe ecological and health problems in drinking water reservoirs. To alleviate this problem, allelopathically active submerged macrophytes can be used to reduce cyanobacterial growth. Accordingly, this study aimed to evaluate the sensitivity of strains of the Microcystis aeruginosacomplex isolated from reservoirs with the presence and absence of submerged macrophytes to the allelochemicals of Ceratophyllum demersum.A coexistence experiment was carried out between the submerged macrophyte C. demersum and four Microcystisstrains, with two treatments for each strain, one in coexistence with the submerged macrophyte (7 g L-1) and control (in the absence of the macrophyte). Two strains of M. aeruginosa(BMIUFRPE-06 and BMIUFRPE-07) and two of M. panniformis(BMIUFRPE-08 and BMIUFRPE-09) were used, which were isolated from Cajueiro (with submerged macrophytes) and Tapacurá (without submerged macrophytes) reservoirs, respectively. The biomass of Microcystisstrains from the reservoir without macrophytes (BMIUFRPE-08 and BMIUFRPE-09) was significantly inhibited in 96% (T-test: p 0.05; growth rate -ANOVA: p > 0.05). These results suggest that strains isolated from environments with submerged macrophytes are less sensitive to allelochemicals of these plants,as these strains may be adapted to the coexistence with submerged macrophytes.

Essential Oil of Calotropis procera: Comparative Chemical Profiles, Antimicrobial Activity, and Allelopathic Potential on Weeds.

Plants are considered green resources for thousands of bioactive compounds. Essential oils (EOs) are an important class of secondary compounds with various biological activities, including allelopathic and antimicrobial activities. Herein, the present study aimed to compare the chemical profiles of the EOs of the widely distributed medicinal plant Calotropis procera collected from Saudi Arabia and Egypt. In addition, this study also aimed to assess their allelopathic and antimicrobial activities. The EOs from Egyptian and Saudi ecospecies were extracted by hydrodistillation and analyzed via GC-MS. The correlation between the analyzed EOs and those published from Egypt, India, and Nigeria was assessed by principal component analysis (PCA) and agglomerative hierarchical clustering (AHC). The allelopathic activity of the extracted EOs was tested against two weeds (Bidens pilosa and Dactyloctenium aegyptium). Moreover, the EOs were tested for antimicrobial activity against seven bacterial and two fungal strains. Ninety compounds were identified from both ecospecies, where 76 compounds were recorded in Saudi ecospecies and 33 in the Egyptian one. Terpenes were recorded as the main components along with hydrocarbons, aromatics, and carotenoids. The sesquiterpenes (54.07%) were the most abundant component of EO of the Saudi sample, while the diterpenes (44.82%) represented the mains of the Egyptian one. Hinesol (13.50%), trans-chrysanthenyl acetate (12.33%), 1,4-trans-1,7-cis-acorenone (7.62%), phytol (8.73%), and myristicin (6.13%) were found as the major constituents of EO of the Saudi sample, while phytol (38.02%), n-docosane (6.86%), linoleic acid (6.36%), n-pentacosane (6.31%), and bicyclogermacrene (4.37%) represented the main compounds of the Egyptian one. It was evident that the EOs of both ecospecies had potent phytotoxic activity against the two tested weeds, while the EO of the Egyptian ecospecies was more effective, particularly on the weed D. aegyptium. Moreover, the EOs showed substantial antibacterial and antifungal activities. The present study revealed that the EOs of Egyptian and Saudi ecospecies were different in quality and quantity, which could be attributed to the variant environmental and climatic conditions. The EOs of both ecospecies showed significant allelopathic and antimicrobial activity; therefore, these EOs could be considered as potential green eco-friendly resources for weed and microbe control, considering that this plant is widely grown in arid habitats.

Invasive plants exert disproportionately negative allelopathic effects on the growth and physiology of the earthworm Eisenia fetida.

Exotic invasive plants possess the capacity to disrupt and extirpate populations of native species. Native plants' increased sensitivity to invaders' allelochemicals is a mechanism by which this can occur. However, it is not clear whether and how the allelopathic effects of invasive plants affect members of the soil faunal community - particularly the important functional guild of earthworms. We used the model earthworm Eisenia fetida to investigate the responses to extracts from the widely invasive Asterids (Ageratina adenophora, Bidens pilosa, Erigeron annuus) and closely-related native species in a greenhouse experiment. We observed declines in body mass and respiration, and increases in oxidative and DNA damage biomarkers in the native earthworm E. fetida when grown under root and leaf extracts from these invasive plants. These effects were concentration-dependent, and worm growth and physiology was most negatively affected under the highest concentrations of leaf extracts. Most importantly, extracts from invasive plants caused significantly more negative effects on E. fetida than did extracts from native plant species, indicating allelopathy from invasive plants may inhibit earthworm physiological functioning. These results expand the domain of the novel weapons hypothesis to the earthworm guild and demonstrate the utility of E. fetida as a bioindicator for plant allelochemicals.