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How do chemically defended animals resist their own toxins? This intriguing question on the concept of autotoxicity is at the heart of how species interactions evolve. In this issue of Molecular Ecology (Molecular Ecology, 2024, 33), Bodawatta and colleagues report on how Papua New Guinean birds coopted deadly neurotoxins to create lethal mantles that protect against predators and parasites. Combining chemical screening of the plumage of a diverse collection of passerine birds with genome sequencing, the researchers unlocked a deeper understanding of how some birds sequester deadly batrachotoxin (BTX) from their food without poisoning themselves. They identified that birds impervious to BTX bear amino acid substitutions in the toxin-binding site of the voltage-gated sodium channel Nav1.4, whose function is essential for proper contraction and relaxation of vertebrate muscles. Comparative genetic and molecular docking analyses show that several of the substitutions associated with insensitivity to BTX may have become prevalent among toxic birds through positive selection. Intriguingly, poison dart frogs that also co-opted BTX in their lethal mantles were found to harbour similar toxin insensitivity substitutions in their Nav1.4 channels. Taken together, this sets up a powerful model system for studying the mechanisms behind convergent molecular evolution and how it may drive biological diversity.

In recycled hydroponics, successive crop cultivation by maintaining electrical conductivity (EC) suffers lower growth performance due to accumulating autotoxic root exudates. In this study, the efficiency of alternate current electro degradation (AC-ED) was evaluated for degrading allelochemicals and recovering retarded lettuce yield cultivated in EC-adjusted repeatedly used nutrient solutions. From benzoic acid (BA)-added nutrient solution, BA was completely degraded after 24 h by applying AC-ED at 551 and 940 Hz frequency with 50 and 80% electrical duty. In lettuce bioassay, fresh mass was negatively affected without the AC-ED-treated solution. Finally, lettuce seedlings were hydroponically grown in a plant factory using a half-strength Enshi nutrient solution. Culture solutions were unchanged in non-renewed solutions. Nutrient elements were supplied based on the EC (1.42 dS m−1) of culture solutions. The fresh weight of lettuce was gradually decreased in subsequent cultures. Nutrient absorption rate was reduced in non-renewed solutions though enough of all nutrient elements were available in the solution. In the final culture, the highest shoot fresh weight (SFW) was recorded in the renewed (83.0 g plant−1) solution which was similar to the AC-ED-treated solution (81.0 g plant−1) and the lowest (58.0 g plant−1) was in the non-renewed solution. By applying AC-ED, 40% lettuce yield was recovered in the EC-adjusted solution without renewing. Therefore, it is recommended that the continuous application of AC-ED with the capacity of 551 Hz and 50% duty would be applied for recovering the retarded lettuce yield cultivated with repeatedly used culture solutions in recycled hydroponics. [ABSTRACT FROM AUTHOR]

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Abstract Modern intensive cropping systems often contribute to the accumulation of phenolic acids in the soil, which promotes the development of soilborne diseases. This can be suppressed by intercropping. This study analyzed the effects of intercropping on Fusarium wilt based on its effect on photosynthesis under stress by the combination of Fusarium commune and cinnamic acid. The control was not inoculated with F. commune, while the faba bean plants (Vicia faba L.) were inoculated with this pathogen in the other treatments. The infected plants were also treated with cinnamic acid. This study examined the development of Fusarium wilt together with its effects on the leaves, absorption of nutrients, chlorophyll fluorescence parameters, contents of photosynthetic pigments, activities of photosynthetic enzymes, gas exchange parameters, and the photosynthetic assimilates of faba bean from monocropping and intercropping systems. Under monocropping conditions, the leaves of the plants inoculated with F. commune grew significantly less, and there was enhanced occurrence of the Fusarium wilt compared with the control. Compared with the plants solely inoculated with F. commune, the exogenous addition of cinnamic acid to the infected plants significantly further reduced the growth of faba bean leaves and increased the occurrence of Fusarium wilt. A comparison of the combination of F. commune and cinnamic acid in intercropped wheat and faba bean compared with monocropping showed that intercropping improved the absorption of nutrients, increased photosynthetic pigments and its contents, electron transport, photosynthetic enzymes, and photosynthetic assimilates. The combination of these factors reduced the occurrence of Fusarium wilt in faba bean and increased the growth of its leaves. These results showed that intercropping improved the photosynthesis, which promoted the growth of faba bean, thus, reducing the development of Fusarium wilt following the stress of infection by F. commune and cinnamic acid. This research should provide more information to enhance sustainable agriculture.

Trianthema portulacastrum L. is an alien naturalized noxious summer weed belonging to Aizoaceae. Our field observations revealed that it was the dominant weed in the fields planted with maize and other summer crops, and on roadsides of wastelands and farmlands. This study was conducted to evaluate the potential allelopathic effects of the aqueous shoot extracts and mulching with different rates of air-dried shoots of T. portulacastrum collected from maize fields on two associating weeds namely, Corchorus olitorius and Euphorbia heterophylla. Seed germination and seedling growth of the test weeds decreased with increasing concentrations of the aqueous extract. The seeds bioassay experiments confirmed the autotoxicity of T. portulacastrum. We have found that the allelopathic effects of the target species on the two weeds, and the autotoxic effects on itself were mainly attributed to the presence of allelochemicals and not to the osmotic potential of the aqueous extracts. Mulching had inhibitory effects on the percentage of dry matter allocations and the growth parameters of the test weed species. The relative growth rate, the net assimilation rate, and the leaf area ratio of the non-mulched weeds were higher than those of mulched ones. The phytochemical screening of the dry shoots of T. portulacastrum indicated the presence of phenolic compounds, flavonoids, tannins, and alkaloids. The high concentration of alkaloids in the shoot deserves further research. The high-performance liquid chromatography confirmed the presence of 14 phenolic substances, which included 12 phenolic compounds, and 2 flavonoids. Evaluation of seed bioassay and mulching experiments revealed that the aqueous extract concentrations of 4 and 6 % of T. portulacastrum inhibited the germination of E. heterophylla, while the mulched plants showed tolerance at the juvenile-flowering stage. We conclude that tolerance to allelopathic stress varied among the tested weed species and the growth stages of the same species. The suitability of using either aqueous shoot extract or mulch of T. portulacastrum as a potential bioherbicide deserves further monitoring under field conditions. [ABSTRACT FROM AUTHOR]

Modern intensive cropping systems often contribute to the accumulation of phenolic acids in the soil, which promotes the development of soilborne diseases. This can be suppressed by intercropping. This study analyzed the effects of intercropping on Fusarium wilt based on its effect on photosynthesis under stress by the combination of Fusarium commune and cinnamic acid. The control was not inoculated with F. commune, while the faba bean plants (Vicia faba L.) were inoculated with this pathogen in the other treatments. The infected plants were also treated with cinnamic acid. This study examined the development of Fusarium wilt together with its effects on the leaves, absorption of nutrients, chlorophyll fluorescence parameters, contents of photosynthetic pigments, activities of photosynthetic enzymes, gas exchange parameters, and the photosynthetic assimilates of faba bean from monocropping and intercropping systems. Under monocropping conditions, the leaves of the plants inoculated with F. commune grew significantly less, and there was enhanced occurrence of the Fusarium wilt compared with the control. Compared with the plants solely inoculated with F. commune, the exogenous addition of cinnamic acid to the infected plants significantly further reduced the growth of faba bean leaves and increased the occurrence of Fusarium wilt. A comparison of the combination of F. commune and cinnamic acid in intercropped wheat and faba bean compared with monocropping showed that intercropping improved the absorption of nutrients, increased photosynthetic pigments and its contents, electron transport, photosynthetic enzymes, and photosynthetic assimilates. The combination of these factors reduced the occurrence of Fusarium wilt in faba bean and increased the growth of its leaves. These results showed that intercropping improved the photosynthesis, which promoted the growth of faba bean, thus, reducing the development of Fusarium wilt following the stress of infection by F. commune and cinnamic acid. This research should provide more information to enhance sustainable agriculture. [ABSTRACT FROM AUTHOR]

Allelopathy is a process that involves secondary metabolites produced by plants. Sorghum plants can produce allelopathic that can be used as bioherbicides. The source of extracts from different varieties has different bioherbicide potential. This study aims to test the extracts of ratoon organs of sorghum plants grown on inceptisol land against germination. The research was conducted on inceptisol land in Kandang Mas-Bengkulu City, and in the laboratory, January-June 2023. The study used a single factor completely randomized design. The treatments tested were seven-week-old sorghum water extracts derived from different materials and varieties, (control, Numbu variety leaves, Numbu variety stems, Numbu variety roots, Super 1 variety leaves, Super 1 variety stems, Super 1 variety roots, Suri 4 variety leaves, Suri 4 variety stems, and Suri 4 variety roots). The variables observed in this study were normal sprouts percentage, abnormal sprouts percentage, hypocotyl length, radicle length, fresh weight (hypocotyl, radicle, cotyledons, and sprouts), dry weight (hypocotyl, radicle, cotyledons, and sprouts). Observed data were analyzed for variance and treatments with significant effects were further tested using the LSD test 5% level. The results showed that ratoon extract was able to inhibit sorghum seed germination. The aqueous extract derived from the ratoon leaves of the Super 1 variety produced the highest abnormal sprouts, the lowest normal sprouts, the lowest plumula length, and the radicle length. The leaf organs of Super 1 variety ratoon in particular and the organs of Super 1 variety ratoon, in general, are the best allelopathic materials as bioherbicides. [ABSTRACT FROM AUTHOR]

Stunted vegetative growth and delayed or absent flowering are commonly observed in eustoma (Eustoma grandiflorum) when cultivated continuously in the same greenhouse soil. These effects are likely caused by the excessive accumulation of soluble salts and/or phytotoxic organic acids in the soil. This study aimed to clarify the mechanism of continuous cropping obstacles and formulate prevention measures of eustoma. Seedlings of eustoma 'Croma III White' were grown hydroponically with 0%, 25%, 50%, 75%, 100% (full), 125%, 150%, 175%, or 200% strength of Johnson's solution. Plant height, leaf area, and shoot dry weight increased steadily as solution strength increased from 25% to 125% [solution electrical conductivity (EC) of 2.4 dS-m21] and then gradually decreased as solution strength further increased from 125% to 200% (solution EC of 3.8 dS.m-¹). When grown hydroponically in 200% strength Johnson's solution, plant height, leaf area, and root length increased with increasing equimolar mixtures of organic acids, including maleic acid, benzoic acid, malic acid, and hydroxybenzoic acid, up to 1.2 to 1.6 mM and decreased thereafter. Node number and the percentage of flower bud visibility declined beyond 1.6 mM organic acid mixtures. Plants with 2.0 and 2.4 mM organic acid mixtures had the lowest net photosynthetic rate, stomatal conductance, transpiration, and intercellular carbon dioxide concentration. Plants had normal growth and produced flower buds when the continuously cropped soil was preconditioned with 100 °C reverse-osmosis water before planting. [ABSTRACT FROM AUTHOR]

The volatile compounds produced by plants play an important role in plant growth, plant communication, and resistance to biological and abiotic stresses. Astragalus membranaceus var. mongholicus (AM) is a perennial herbaceous plant (Leguminosae) that is widely cultivated in northwest China. The bioactive compounds in its root have shown various pharmacological activities. Root rot disease caused by Fusarium spp. often occurs in AM planting with increasing severity in continuous monoculture. It is currently still unclear what are the effects of the volatile compounds produced by fresh AM on itself, other crops cultivated on the same field after AM, pathogen, and rhizobia. In this study, we found that seed germination and seedling growth of AM, lettuce (Lactuca sativa L.), and wheat (Triticum aestivum L.) could be affected if they were in an enclosed space with fresh AM tissue. Additionally, 90 volatile compounds were identified by SPME-GC-MS from whole AM plant during the vegetative growth, 36 of which were specific to aerial parts of AM (stems and leaves, AMA), 17 to roots (AMR), and 37 were found in both AMA and AMR. To further identify the allelopathic effects of these volatile compounds, five compounds (1-hexanol, (E)-2-hexenal, (E,E)-2,4-decadienal, hexanal, and eugenol) with relatively high content in AM were tested on three receptor plants and two microorganisms. We found that (E,E)-2,4-decadienal and (E)-2-hexenal showed significant inhibitory effects on the growth of AM and lettuce. One-hexanol and hexanal suppressed the growth of wheat, while eugenol showed a similar effect on all three plant species. Moreover, the activities of these compounds were dose dependent. Notably, we discovered that (E)-2-hexenal and eugenol also inhibited the growth of the pathogen Fusarium solani by as high as 100%. Meanwhile, all five compounds tested suppressed the rhizobia Sinorhizobium fredii. In summary, this study furthered our understanding of the comprehensive allelopathic effects of the main volatile components of AM. [ABSTRACT FROM AUTHOR]

Allelopathy is the interaction between donor plants and receiver plants through allelochemicals. According to a great number of publications, allelopathy may be involved in several ecological aspects such as the formation of monospecific stands and sparse understory vegetation for certain plant species. Allelopathy also contributes to the naturalization of invasive plant species in introduced ranges. Autotoxicity is a particular type of allelopathy involving certain compounds. Many medicinal plants have been reported to show relatively high allelopathic activity. We selected plant species that show high allelopathic activity and isolated allelochemicals through the bioassay-guided purification process. More than 100 allelochemicals, including novel compounds have been identified in some medicinal and invasive plants, plants forming monospecific stands, plants with sparse understory vegetation, and plants showing autotoxicity. The allelopathic activity of benzoxazinones and related compounds was also determined. [ABSTRACT FROM AUTHOR]

The prominent problem of continuous cropping obstacle has been frustrating the morel farming. To deepen the understanding on morel continuous cropping obstacle, the allelopathic effects of phenolic acid extracts from morel continuous cropping soils on growth and development of Morchella sextelata, M. eximia, M. importuna, pathogenic fungus Fusarium sp. and soil-dominant fungus Chaetomium sp. were investigated. These effects were expressed as response index (RI). Under actual content of phenolic acids (6.150 μg/g fresh mixed continuous cropping soil), the mycelial growth of all tested morel strains was inhibited (RI < 0), while the allelopathic effect of control phenolic acids (4.252 μg/g fresh mixed control soil) was between promotion and inhibition, which suggested that the phenolic acid extracts from morel continuous cropping soils may exhibit certain extent of autotoxicity for the existence of morel-specific allelochemicals. In addition, the aggravated pigmentation and reduced occurrence of sclerotium in three Morchella fungi at growth inhibitory concentrations of phenolic acids indicated the induction of morel strain aging. Meanwhile, most concentrations of phenolic acids showed stimulatory effects on sporulation of Fusarium sp. and Chaetomium sp. (RI > 0), manifesting the enrichment of soil-borne pathogenic fungi and dominance of certain fungal population in soil ecosystem. Collectively, the allelopathic effects of phenolic acid extracts play an instrumental role in morel continuous cropping obstacle. The study will be beneficial for healthy development of morel artificial cultivation. [ABSTRACT FROM AUTHOR]

Lilium brownii F. E. Brown ex Miellez var. viridulum Baker (Longya lily) is a variety of Lilium brownii F.E. Br. ex Miellez. We used HS-SPME and GC-MS to screened the tissues of L. brownii roots, stems, bulbs, and leaves and obtained 2,4-DTBP as an autotoxic substance for subsequent analysis. 2,4-DTBP was highly autotoxic in some treatment groups. Based on changes in physiological indicators, we carried out transcriptomic analysis to investigate the mechanisms of autotoxicity of substances on L. brownii and obtained 188,505 Unigenes. GO and KEGG enrichment analyses showed that L. brownii responded differently to different concentrations and treatment times of 2,4-DTBP. We observed significant changes in genes associated with ROS, phytohormones, and MAPK signaling cascades. 2,4-DTBP affects chloroplasts, the integrity of the respiratory electron transport chain, and ribosomes, causing L. brownii autotoxicity. Our findings provide a practical genomic resource for future research on L. brownii autotoxicity and evidence for the mechanism of action of autotoxic substances.

Panax notoginseng is a valuable Chinese herb in China, and the root should be harvested between three and seven years after planting it. However, the growth of P. notoginseng is frequently hindered due to replanting failure. There have been numerous studies proving that the accumulation of allelochemicals in the soil is considered to be one of the reasons for the replanting failure of P. notoginseng. Biodegradation of allelochemical in soil has been shown to be an effective measure to alleviate continuous cropping obstacles, so screening allelochemical-degrading bacteria could provide biological resources for soil remediation. Based on this, this study adopted a research strategy of enrichment and domestication to isolate and screen saponin-degrading bacteria from the rhizosphere soil of P. notoginseng, which had been grown continuously for three years and more. Also, the highly active strains were identified by 16S rRNA gene analysis. In addition, the effect of highly active strain SC3 on degrading allelochemicals under different conditions was studied by HPLC. The results were as follows: (1) Eight strains of potentially degrading bacteria were successfully isolated from the rhizosphere soil of P. notoginseng. The results of the initial screening evaluation showed that strain SC3 had the best biodegradation effect on total saponins with 87.42% degradation rate. (2) Strain SC3 was identified as Stenotrophomonas sp. based on 16S rRNA gene analysis coupled with physiological and biochemical analyses. (3) The biodegradation of ginsenoside Rb1 by strain SC3 was stronger than its biodegradation of ginsenoside Rg1 under the same culture conditions. (4) The degradation of ginsenoside Rb1 by SC3 strain under liquid culture conditions was significantly affected by different factors, such as substrate concentration, inoculum amount and culture temperature. All the results indicate that the enrichment and domestication strategy can effectively screen allelochemical-degrading bacteria, and a possible application of strain SC3 in the bioremediation of saponin contamination in agricultural environments. The results provide biological resources for replanting soil remediation and theoretical basis for further study of saponin degradation mechanism.

Premise: β‐Cyanoalanine synthase (β‐CAS) and alternative oxidase (AOX) play important roles in the ability of plants to detoxify and tolerate hydrogen cyanide (HCN). These functions are critical for all plants because HCN is produced at low levels during basic metabolic processes, and especially for cyanogenic species, which release high levels of HCN following tissue damage. However, expression of β‐CAS and Aox genes has not been examined in cyanogenic species, nor compared between cyanogenic and acyanogenic genotypes within a species. Methods: We used a natural polymorphism for cyanogenesis in white clover to examine β‐CAS and Aox gene expression in relation to cyanogenesis‐associated HCN exposure. We identified all β‐CAS and Aox gene copies present in the genome, including members of the Aox1, Aox2a, and Aox2d subfamilies previously reported in legumes. Expression levels were compared between cyanogenic and acyanogenic genotypes and between damaged and undamaged leaf tissue. Results: β‐CAS and Aox2a expression was differentially elevated in cyanogenic genotypes, and tissue damage was not required to induce this increased expression. Aox2d, in contrast, appeared to be upregulated as a generalized wounding response. Conclusions: These findings suggest a heightened constitutive role for HCN detoxification (via elevated β‐CAS expression) and HCN‐toxicity mitigation (via elevated Aox2a expression) in plants that are capable of cyanogenesis. As such, freezing‐induced cyanide autotoxicity is unlikely to be the primary selective factor in the evolution of climate‐associated cyanogenesis clines. [ABSTRACT FROM AUTHOR]

Alfalfa is a leguminous plant with strong autotoxicity, which seriously affects regeneration and stability. In order to clarify the relationship between the key autotoxic substances and autotoxicity of alfalfa, this experiment determined the content of phenolic autotoxic substances in different varieties of alfalfa and the effect of different concentrations of alfalfa extracts on seed germination, seedling growth and physiology. The results showed that the content of single autotoxic substances in the eight alfalfa varieties was highest for total coumarin. The variety with the highest total coumarin content was "LZ", and the lowest content was "656". Principal component analysis of the autotoxicity of eight alfalfa varieties revealed that the variety with the strongest autotoxicity was "LZ" and the weakest was "656". After treatment with extracts, the germination potential, germination rate, germination index and vigor index of 656 were higher than those of LZ, and the seeds of LZ and 656 did not germinate when the concentration was higher than C0.025 and C0.05, respectively. Compared with LZ, 656 had stronger osmotic regulation and antioxidant capacity, while the degree of membrane lipid peroxidation and ROS accumulation were lower. Further correlation analysis between the autotoxic substance content and autotoxicity observed that the content of total coumarin and autotoxic substances showed a significant positive association with autotoxicity (p < 0.01), and the total coumarin content showed a significant positive correlation with the content of autotoxic substances (p < 0.05). The total coumarin content is the major contributor to autotoxicity, and the higher the coumarin content, the higher the autotoxic substance content and the stronger the autotoxicity. Eight alfalfa varieties were systematically clustered on the basis of total coumarin content and autotoxicity, and the high-autotoxic alfalfa variety "LZ" and low-autotoxic alfalfa variety "656" were screened. [ABSTRACT FROM AUTHOR]

Widespread autotoxicity is an important obstacle to natural regeneration of many plants. The rare relict plant Metasequoia glyptostroboides is a difficult to natural regeneration and is affected by litter allelopathy. However, little is known about the potential influence of autotoxic substances on different regeneration stages of M. glyptostroboides. We identified multiple chemical compounds of aqueous extracts from fresh (recently accumulated) and natural litter (mixture of litter different phases of decomposition), to evaluate the autotoxic effects of the four most important detected compounds applied individually on seed germination and seedling growth of M. glyptostroboides. Results found that the 28 chemical compounds were identified in the aqueous extracts of M. glyptostroboides litter. The Jaccard similarity coefficient of chemical compounds in aqueous extracts of fresh and natural litter of M. glyptostroboides reached 50%. The number of chemical compounds in fresh litter was 5.56% more than that in natural litter. Catechol, trifluoroacetamide, benzoic acid and D-(+)-arabitol significantly affected seed germination rate, seed germination index, vigor index, shoot length and main root length of M. glyptostroboides. Specifically, benzoic acid had the strongest inhibitory effect, followed by catechol, trifluoroacetamide and D-(+)-arabitol. The autotoxic effect was concentration dependent, low concentrations were positive and neutral, high and extremely high concentrations were negative for all the chemical compounds. Moreover, catechol, trifluoroacetamide, benzoic acid and D-(+)-arabitol were autotoxic substances affecting the natural regeneration of M. glyptostroboides, as well as strongly inhibited at the shoot growth stage. This study confirms that natural regeneration of M. glyptostroboides is restricted by a large amount of litter coverage under the forest, highlighting how the chemical compounds responsible for the autotoxic characteristics of M. glyptostroboides affect the different regeneration stages of M. glyptostroboides. [ABSTRACT FROM AUTHOR]

Abstract Background Allelopathy is closely associated with rhizosphere biological processes, and rhizosphere microbial communities are essential for plant development. However, our understanding of rhizobacterial communities under influence of allelochemicals in licorice remains limited. In the present study, the responses and effects of rhizobacterial communities on licorice allelopathy were investigated using a combination of multi-omics sequencing and pot experiments, under allelochemical addition and rhizobacterial inoculation treatments. Results Here, we demonstrated that exogenous glycyrrhizin inhibits licorice development, and reshapes and enriches specific rhizobacteria and corresponding functions related to glycyrrhizin degradation. Moreover, the Novosphingobium genus accounted for a relatively high proportion of the enriched taxa and appeared in metagenomic assembly genomes. We further characterized the different capacities of single and synthetic inoculants to degrade glycyrrhizin and elucidated their distinct potency for alleviating licorice allelopathy. Notably, the single replenished N (Novosphingobium resinovorum) inoculant had the greatest allelopathy alleviation effects in licorice seedlings. Conclusions Altogether, the findings highlight that exogenous glycyrrhizin simulates the allelopathic autotoxicity effects of licorice, and indigenous single rhizobacteria had greater effects than synthetic inoculants in protecting licorice growth from allelopathy. The results of the present study enhance our understanding of rhizobacterial community dynamics during licorice allelopathy, with potential implications for resolving continuous cropping obstacle in medicinal plant agriculture using rhizobacterial biofertilizers. Video Abstract

Plant-soil negative feedback (NF) is a well-established phenomenon that, by preventing the dominance of a single species, allows species coexistence and promotes the maintenance of biodiversity. At community scale, localized NF may cause the formation of exclusion zones under adult conspecifics leading to Janzen-Connell (JC) distribution. In this study, we explore the connection between adult density, either conspecifics or heterospecifics, on the probability of occurrence of JC distributions. Using an individual-based modelling approach, we simulated the formation of exclusion zones due to the build-up of NF in proximity of conspecific adult plants and assessed the frequency of JC distribution in relation to conspecifics and heterospecifics density ranging from isolated trees to closed forest stands. We found that JC recruitment distribution is very common in the case of an isolated tree when NF was strong and capable to form an exclusion zone under the parent tree. At very low NF intensity, a prevalence of the decreasing pattern was observed because, under such conditions, the inhibitory effect due to the presence of the mother tree was unable to overcome the clustering effect of the seed dispersal kernel. However, if NF is strong the JC frequency suddenly decreases in stands with a continuous conspecific cover likely as a result of progressive expansion of the exclusion zone surrounding all trees in closed forest stands. Finally, our simulations showed that JC distribution should not be frequent in the case of rare species immersed in a matrix of heterospecific adults. Overall, the model shows that a plant suffering from strong NF in monospecific stands can rarely exhibit a recruitment pattern fitting the JC model. Such counterintuitive results would provide the means to reconcile the well-established NF framework with part the forest ecologists' community that is still skeptical towards the JC model. Synthesis: Our model highlights the complex interconnection between NF intensity, stand density, and recruitment patterns explaining where and why the JC distribution occurs. Moreover, predicting the occurrence of JC in relation to stand density we clarify the relevance of this ecological phenomenon for future integration in plant community frameworks. [ABSTRACT FROM AUTHOR]

Panax notoginseng is a valuable Chinese herb in China, and the root should be harvested between three and seven years after planting it. However, the growth of P. notoginseng is frequently hindered due to replanting failure. There have been numerous studies proving that the accumulation of allelochemicals in the soil is considered to be one of the reasons for the replanting failure of P. notoginseng. Biodegradation of allelochemical in soil has been shown to be an effective measure to alleviate continuous cropping obstacles, so screening allelochemical-degrading bacteria could provide biological resources for soil remediation. Based on this, this study adopted a research strategy of enrichment and domestication to isolate and screen saponin-degrading bacteria from the rhizosphere soil of P. notoginseng, which had been grown continuously for 3 years and more. Also, the highly active strains were identified by 16S rRNA gene analysis. In addition, the effect of highly active strain SC3 on degrading allelochemicals under different conditions was studied by HPLC. The results were as follows:(1)Eight strains of potentially degrading bacteria were successfully isolated from the rhizosphere soil of P. notoginseng. The results of the initial screening evaluation showed that strain SC3 had the best biodegradation effect on total saponins with 87.42% degradation rate.(2)Strain SC3 was identified as Stenotrophomonas sp. based on 16S rRNA gene analysis coupled with physiological and biochemical analyses.(3)The biodegradation of ginsenoside Rb1 by strain SC3 was stronger than its degradation of ginsenoside Rg1 under the same culture conditions.(4)The degradation of ginsenoside Rb1 by SC3 strain under liquid culture conditions was significantly affected by different factors, such as substrate concentration, inoculum amount and incubation temperature. This study shows that the enrichment and domestication strategy can effectively screen allelochemical-degrading bacteria, and a possible application of strain SC3 in the bioremediation of saponin contamination in agricultural environments. [ABSTRACT FROM AUTHOR]

Ectomycorrhizas (ECM) are a common symbiotic association between fungi and various plant species in forest ecosystems, affecting community assemblages at the landscape level. ECMs benefit host plants by increasing the surface area for nutrient uptake, defending against pathogens, and decomposing organic matter in the soil. ECM-symbiotic seedlings are also known to perform better in conspecific soils than other species unable to carry the symbiosis, in a process referred to as plant-soil feedback (PSF). In this study, we tested the effects of different leaf litter amendments on ECM and non-ECM seedlings of Quercus ilex inoculated with Pisolithus arrhizus and how they altered the litter-induced PSF. Our experiment showed that the ECM symbiont induced a shift from negative PSF to positive PSF in Q. ilex seedlings by analysing plant and root growth parameters. However, non-ECM seedlings performed better than ECM seedlings in a no-litter condition, indicating an autotoxic effect when litter is present without ECM symbionts. Conversely, ECM seedlings with litter performed better at different decomposition stages, suggesting a possible role of the symbiosis of P. arrhizus and Q. ilex in recycling autotoxic compounds released from conspecific litter, transforming them into nutrients that are transferred to the plant host. [ABSTRACT FROM AUTHOR]

Modelling the inter-relationships between litter accumulation and plant–soil feedback is a major challenge to predict natural and agricultural ecosystem dynamics. At increasing levels of undecomposed plant litter, seedling growth tends to show a multi-faceted response trend, characterised by a peak of positive stimulation at lower dosage followed by inhibition at higher dosage. In this study, a new logistic model was developed to describe such trend and disentangle substrate-specific positive and negative effects of plant litter. The model was tested on 35 litter types applied to the common phytometer Lepidium sativum; all litter types were collected in Mediterranean shrublands of Campania region (southern Italy). Model fitting resulted to be generally higher relative to the widely used linear log response model, although in only half of the cases it also gave more parsimonious results in terms of minimising information loss. Positive and negative effects of plant litter resulted to be uncorrelated, showing that the overall trend is probably the result of the combined action of separate factors rather than the effect of a single factor behaving differently at the different doses. The results of this work provide new tools to finely tune the optimal doses in experiments on hormesis and litter phytotoxicity, through the identification of the most suited doses to centre the range of nearly linear response to litter concentration. A wide screening is also presented on the phytotoxicity profiles of a number of spontaneous plant species widely distributed in the Mediterranean area. [ABSTRACT FROM AUTHOR]

Abstract Background The yield and quality of Pugionium cornutum (L.) Gaertn., a healthy, green vegetable with low sugar and high protein contents and high medicinal value, is severely affected by autotoxicity, which is a leading factor in the formation of plant disease. To help characterize the autotoxicity mechanism of P. cornutum (L.) Gaertn., we performed transcriptomic and metabolic analysis of the roots of P. cornutum (L.) Gaertn. response to phthalic acid, an autotoxin from P. cornutum (L.) Gaertn. Results In this study, high-throughput sequencing of nine RNA-seq libraries generated from the roots.of P. cornutum (L.) Gaertn. under different phthalic acid treatments yielded 37,737 unigenes. In total, 1085 (703 upregulated and 382 downregulated) and 5998 (4385 upregulated and 1613 downregulated) DEGs were identified under 0.1 and 10 mmol·L− 1 phthalic acid treatment, respectively, compared with the control treatment. Glutathione metabolism was among the top five important enriched pathways. In total, 457 and 435 differentially accumulated metabolites were detected under 0.1 and 10 mmol·L− 1 phthalic acid treatment compared with the control, respectively, of which 223 and 253, respectively, increased in abundance. With the increase in phthalic acid concentration, the accumulation of ten metabolites increased significantly, while that of four metabolites decreased significantly, and phthalic acid, dambonitol, 4-hydroxy-butyric acid, homocitrulline, and ethyl β-D-glucopyranoside were 100 times more abundant under the 10 mmol·L− 1 phthalic acid treatment than under the control. Seventeen differentially expressed genes significantly associated with phthalic acid content were identified. In addition, the L-histidinol content was highest under 0.1 mmol·L− 1 phthalic acid, and a total of eleven differentially expressed genes were significantly positively correlated with the L-histidinol content, all of which were annotated to heat shock proteins, aquaporins and cysteine proteases. Conclusions Accumulation of autotoxins altered the metabolic balance in P. cornutum (L.) Gaertn. and influenced water absorption and carbon and nitrogen metabolism. These important results provide insights into the formation mechanisms of autotoxicity and for the subsequent development of new control measures to improve the production and quality of replanted plants.

Background: Allelopathy is closely associated with rhizosphere biological processes, and rhizosphere microbial communities are essential for plant development. However, our understanding of rhizobacterial communities under influence of allelochemicals in licorice remains limited. In the present study, the responses and effects of rhizobacterial communities on licorice allelopathy were investigated using a combination of multi-omics sequencing and pot experiments, under allelochemical addition and rhizobacterial inoculation treatments. Results: Here, we demonstrated that exogenous glycyrrhizin inhibits licorice development, and reshapes and enriches specific rhizobacteria and corresponding functions related to glycyrrhizin degradation. Moreover, the Novosphingobium genus accounted for a relatively high proportion of the enriched taxa and appeared in metagenomic assembly genomes. We further characterized the different capacities of single and synthetic inoculants to degrade glycyrrhizin and elucidated their distinct potency for alleviating licorice allelopathy. Notably, the single replenished N (Novosphingobium resinovorum) inoculant had the greatest allelopathy alleviation effects in licorice seedlings. Conclusions: Altogether, the findings highlight that exogenous glycyrrhizin simulates the allelopathic autotoxicity effects of licorice, and indigenous single rhizobacteria had greater effects than synthetic inoculants in protecting licorice growth from allelopathy. The results of the present study enhance our understanding of rhizobacterial community dynamics during licorice allelopathy, with potential implications for resolving continuous cropping obstacle in medicinal plant agriculture using rhizobacterial biofertilizers. 9UbUWYdP6gv58ro7UNXMiq Video Abstract [ABSTRACT FROM AUTHOR]

Autotoxicity and soil salinization are the main causes of continuous cropping obstacles of melon, which often occur at the same time and aggravate with the extension of cultivation years. Melatonin (MT) has a broad application prospect in improving plant resistance. The effects of exogenous MT on seed germination of melon (Cucumis melo L.) under autotoxicity and saline-alkali combined stress were observed in this paper. Starch and reactive oxygen species metabolism were determined to analyze the physiological and biochemical basis of MT function. Cinnamic acid was used to simulate melon autotoxicity. The mixed solution of NaCl and NaHCO3 was used to simulate saline-alkali stress. The effect of MT showed a concentration-dependent manner. 16 μM exogenous MT can effectively improve the germination rate, germination potential, and vigor index of melon seeds under combined stress, and increase radicle length and fresh weight. Seed vigor index was the most sensitive index, and MT treatment increased by 102.22% compared with combined stress. However, at high concentration, this stress relief effect can be offset or even reversed. MT can significantly shorten the time of seed breaking through the seed coat and improve the root growth inhibited by stress. MT enhanced α-amylase and β-amylase gene expression, antioxidant enzyme, and amylase activity. The contents of starch and soluble sugar changed accordingly. At the same time, the contents of malondialdehyde and reactive oxygen species were reduced. The expression analysis of 10 MT synthesis genes showed that MT treatment up-regulated eight genes. In general, by up-regulating the expression of amylase and some MT synthesis genes, enhancing the activities of antioxidant enzymes and amylase, reducing the content of malondialdehyde and reactive oxygen species, exogenous MT effectively increased the germination rate and germination potential of melon seeds under autotoxicity and saline-alkali combined stress, and significantly improved the quality of seed germination. [ABSTRACT FROM AUTHOR]

Continuous cultivation of the faba bean will lead to its autotoxicity. Faba bean–wheat intercropping can effectively alleviate the autotoxicity of the faba bean. In order to investigate the autotoxicity of water extracts of various parts of the faba bean, we prepared water extracts of various parts of the faba bean, such as the roots, stems, leaves, and rhizosphere soil. The results showed various parts of the faba bean significantly inhibited the germination of faba bean seeds. The main autotoxins in these parts were analyzed using HPLC. Six autotoxins, namely, p-hydroxybenzoic acid, vanillic acid, salicylic acid, ferulic acid, benzoic acid, and cinnamic acid, were identified. The exogenous addition of these six autotoxins significantly inhibited the germination of faba bean seeds in a concentration-dependent manner. Furthermore, field experiments were conducted to investigate the effects of various levels of nitrogen fertilizer on the autotoxin content and the aboveground dry weight of the faba bean in a faba bean–wheat intercropping system. The application of various levels of nitrogen fertilizer in the faba bean–wheat intercropping system could significantly reduce the content of autotoxins and increase the aboveground dry weight in faba bean, particularly at the N2 level (90 kg/hm2). The above results showed that the water extracts of faba bean roots, stems, leaves, and rhizosphere soil inhibited faba bean seed germination. The autotoxicity in faba bean under continuous cropping could be caused by p-hydroxybenzoic acid, vanillic acid, salicylic acid, ferulic acid, benzoic acid, and cinnamic acid. The autotoxic effects in the faba bean were effectively mitigated by the application of nitrogen fertilizer in a faba bean–wheat intercropping system. [ABSTRACT FROM AUTHOR]

Understanding the evolution of plant defenses against herbivores requires identifying the benefits and costs of defense. Here, we tested the hypothesis that the benefits and costs of hydrogen cyanide (HCN) defense against herbivory on white clover (Trifolium repens) are temperature dependent. We first tested how temperature affected HCN production in vitro, and then examined how temperature influenced the efficacy of HCN defense of T. repens against a generalist slug (Deroceras reticulatum) herbivore using no-choice and choice feeding trial assays. To understand how temperature affected the costs of defense, plants were exposed to freezing, and HCN production, photosynthetic activity, and ATP concentration were quantified. HCN production increased linearly from 5 °C to 50 °C, and cyanogenic plants experienced reduced herbivory compared to acyanogenic plants only at warmer temperatures when fed upon by young slugs. Freezing temperatures induced cyanogenesis in T. repens and decreased chlorophyll fluorescence. Cyanogenic plants experienced lower ATP levels than acyanogenic plants due to freezing. Our study provides evidence that the benefits of HCN defense against herbivores are temperature dependent, and freezing may inhibit ATP production in cyanogenic plants, but the physiological performance of all plants recovered quickly following short-term freezing. These results contribute to understanding how varying environments alter the benefits and costs of defense in a model system for the study of plant chemical defenses against herbivores. [ABSTRACT FROM AUTHOR]

Plants can produce and release allelochemicals to interfere with the establishment and growth of conspecific and interspecific plants. Such allelopathy is an important mediator among plant species in natural and managed ecosystems. This review focuses on allelopathy and allelochemicals in grasslands and forests. Allelopathy drives plant invasion, exacerbates grassland degradation and contributes to natural forest regeneration. Furthermore, autotoxicity (intraspecific allelopathy) frequently occurs in pastures and tree plantations. Various specialized metabolites, including phenolics, terpenoids and nitrogen-containing compounds from herbaceous and woody species are responsible for allelopathy in grasslands and forests. Terpenoids with a diversity of metabolites are qualitative allelochemicals occurring in annual grasslands, while phenolics with a few specialized metabolites are quantitative allelochemicals occurring in perennial forests. Importantly, allelochemicals mediate below-ground ecological interactions and plant–soil feedback, subsequently affecting the biodiversity, productivity and sustainability of grasslands and forests. Interestingly, allelopathic plants can discriminate the identity of neighbors via signaling chemicals, adjusting the production of allelochemicals. Therefore, allelochemicals and signaling chemicals synergistically interact to regulate interspecific and intraspecific interactions in grasslands and forests. Allelopathy and allelochemicals in grasslands and forests have provided fascinating insights into plant–plant interactions and their consequences for biodiversity, productivity and sustainability, contributing to our understanding of terrestrial ecosystems and global changes. [ABSTRACT FROM AUTHOR]

Plant-soil negative feedback (NF) is a well-established phenomenon that, by preventing the dominance of a single species, allows species coexistence and promotes the maintenance of biodiversity. At community scale, localized NF may cause the formation of exclusion zones under adult conspecifics leading to Janzen-Connell (JC) distribution. In this study, we explore the connection between adult density, either conspecifics or heterospecifics, on the probability of occurrence of JC distributions. Using an individual-based modelling approach, we simulated the formation of exclusion zones due to the build-up of NF in proximity of conspecific adult plants and assessed the frequency of JC distribution in relation to conspecifics and heterospecifics density ranging from isolated trees to closed forest stands. We found that JC recruitment distribution is very common in the case of an isolated tree when NF was strong and capable to form an exclusion zone under the parent tree. At very low NF intensity, a prevalence of the decreasing pattern was observed because, under such conditions, the inhibitory effect due to the presence of the mother tree was unable to overcome the clustering effect of the seed dispersal kernel. However, if NF is strong the JC frequency suddenly decreases in stands with a continuous conspecific cover likely as a result of progressive expansion of the exclusion zone surrounding all trees in closed forest stands. Finally, our simulations showed that JC distribution should not be frequent in the case of rare species immersed in a matrix of heterospecific adults. Overall, the model shows that a plant suffering from strong NF in monospecific stands can rarely exhibit a recruitment pattern fitting the JC model. Such counterintuitive results would provide the means to reconcile the well-established NF framework with part the forest ecologists’ community that is still skeptical towards the JC model.SynthesisOur model highlights the complex interconnection between NF intensity, stand density, and recruitment patterns explaining where and why the JC distribution occurs. Moreover, predicting the occurrence of JC in relation to stand density we clarify the relevance of this ecological phenomenon for future integration in plant community frameworks.

The volatile compounds produced by plants play an important role in plant growth, plant communication, and resistance to biological and abiotic stresses. Astragalus membranaceus var. mongholicus (AM) is a perennial herbaceous plant (Leguminosae) that is widely cultivated in northwest China. The bioactive compounds in its root have shown various pharmacological activities. Root rot disease caused by Fusarium spp. often occurs in AM planting with increasing severity in continuous monoculture. It is currently still unclear what are the effects of the volatile compounds produced by fresh AM on itself, other crops cultivated on the same field after AM, pathogen, and rhizobia. In this study, we found that seed germination and seedling growth of AM, lettuce (Lactuca sativa L.), and wheat (Triticum aestivum L.) could be affected if they were in an enclosed space with fresh AM tissue. Additionally, 90 volatile compounds were identified by SPME-GC-MS from whole AM plant during the vegetative growth, 36 of which were specific to aerial parts of AM (stems and leaves, AMA), 17 to roots (AMR), and 37 were found in both AMA and AMR. To further identify the allelopathic effects of these volatile compounds, five compounds (1-hexanol, (E)-2-hexenal, (E,E)-2,4-decadienal, hexanal, and eugenol) with relatively high content in AM were tested on three receptor plants and two microorganisms. We found that (E,E)-2,4-decadienal and (E)-2-hexenal showed significant inhibitory effects on the growth of AM and lettuce. One-hexanol and hexanal suppressed the growth of wheat, while eugenol showed a similar effect on all three plant species. Moreover, the activities of these compounds were dose dependent. Notably, we discovered that (E)-2-hexenal and eugenol also inhibited the growth of the pathogen Fusarium solani by as high as 100%. Meanwhile, all five compounds tested suppressed the rhizobia Sinorhizobium fredii. In summary, this study furthered our understanding of the comprehensive allelopathic effects of the main volatile components of AM.

【Objective】To explore the effect of canola water extract on the growth of the seedlings.【Methods】Using distilled water as the control,three concentrations (0.025,0.050,and 0.100 g/mL) of laboratory prepared canola water extract were set to analyze the effects on canola seed germination,seedling growth,main nutrients,and defense enzyme activity.【Results】Compared with the control,the canola water extract of 0.050 g/mL and 0.100 g/mL significantly (P<0.05) reduced the seed germination rate of canola. At the concentration of 0.025 g/mL there were promotion effects on stem length,while at concentrations of 0.050 and 0.100 g/mL,there were inhibitory effects on stem length. All three concentrations had inhibitory effects on the root length of canola seedlings. As the concentration of canola water extract increased,the allelopathic comprehensive effects of canola were "low promotion and high inhibition". In comparison with the control,concentration of 0.100 g/mL significantly (P<0.05) reduced the canola protein content. At concentration of 0.050 g/mL canola proline content was 115.39% higher than the control. The SOD activity of canola treated with different concentrations of water extract was significantly (P<0.05) lower than the control. At the concentration of 0.025 g/mL,the POD activity of canola seedlings was significantly (P<0.05) higher than the control. Different concentrations of water extract treatment had different effect on the variations in canola malondialdehyde content.【Conclusion】Strong autotoxicity existed in canola. [ABSTRACT FROM AUTHOR]

The growth of Panax notoginseng (Burk.) F. H. Chen is frequently hindered due to replanting failure. In the present study, the objective is to determine whether root exudates from P. notoginseng have autotoxicity and identification of allelochemicals from root exudates or rhizosphere soil. We investigated autotoxicity in P. notoginseng using seedling emergence bioassays and hydroponic culture. The allelochemicals in the soils and root exudates were identified with GC-MS, and the autotoxicity of the identified key allelochemicals was investigated by bioassay. The results showed that the root exudates, and extracts from consecutively cultivated soils also showed significant autotoxicity against seedling emergence and growth. In the nonrenewed culture solution without activated charcoal (AC), the fresh and dry mass of P. notoginseng tubers of roots was reduced by about half compared to the addition with AC. A total of 44 different components from all samples were defined by GC-MS analyses. Furthermore, the results of multiple statistical analysis showed a t the difference among cultivated soil, uncultivated soil and root exudates. Bioassay of the identified allelochemicals revealed that benzoic acid, phthalic acid, palmitic acid, and stearic acid significantly affected the root growth of P. notoginseng. These substances at 100 mM more significantly decreased the number of lateral roots. Our results demonstrated that autotoxicity results in replant failure of P. notoginseng. [ABSTRACT FROM AUTHOR]

The allelopathic theory has garnered considerable attention in the field of agricultural production for its efficient plant protection, rapid crop yield increase, and scientific establishment of the crop rotation system. To study the effects of the main maize allelochemical DIMBOA (2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one) on the growth and development of alfalfa under autotoxic coumarin stress, we treated alfalfa seedlings with DIMBOA under coumarin stress and non-stress conditions in this study. Results show that 0.0342 mM coumarin significantly inhibited alfalfa seed germination percentage(Gp), germination potential(GP), radicle length, germ length, seeding height, and simple viability index (SVI), with decreases of 37.29%, 59.91%, 7.60%, 30.90%, 13.27%, and 45.70%, respectively. An amount of 0.6 mM DIMBOA could promote alfalfa seed Gp, GP, radicle length, germ length, seeding height, dry fresh ratio, and SVI, with increases of 12.38%, 23.91%, 48.69%, 48.65%, 48.68%, 295.12%, and 67.17%, respectively. However, the addition of DIMBOA under conditions of coumarin stress could effectively alleviate coumarin effects on alfalfa seedlings. Coumarin + DIMBOA treatment for 24 h mainly decreased reactive oxygen species (ROSs) and malondialdehyde (MDA) as well as soluble protein and soluble sugar, increasing some antioxidant enzyme activities and antioxidant content to alleviate the oxidative damage of alfalfa caused by coumarin stress. Administration of treatment for 72 h significantly promoted the morphological development of alfalfa seeding roots. Administration of treatment for 96 h significantly enhanced the photosynthetic capacity of alfalfa seedlings. The results of principal component analysis demonstrated that chlorophyll b(Chl b)and net photosynthetic rate(Pn) were the key indicators for coumarin + DIMBOA treatment to promote photosynthesis in alfalfa seedlings. Additionally, root length, mean root diameter, and root volume were the key indicators of root growth and development. Coumarin + DIMBOA treatment primarily increased catalase(CAT), peroxidase (POD), and ascorbate peroxidase (APX) activity and antioxidants(ASA) while reducing MDA and superoxide anion radical(O2•−). This study strongly suggested that DIMBOA can effectively improve the tolerance of alfalfa seedlings to coumarin stress through a combination of effects on root morphology, photosynthesis, and physiological indicators. [ABSTRACT FROM AUTHOR]

The goals of this study were to evaluate the role of salicylic acid (SA) in causing autotoxic stress in the faba bean root system and explore how the co‐culture of faba bean (Vicia faba) with wheat (Triticum aestivum) alleviates this stress. We designed a hydroponic pot experiment to study the effects of exogenous SA on the occurrence of Fusarium wilt, seedling growth, physiological resistance of faba bean and pathogenicity of Fusarium oxysporum f. sp. fabae (FOF). The results showed that SA significantly increased the incidence and disease index of faba bean Fusarium wilt, inhibited the growth of seedlings and reduced the physiological resistance of faba bean. An in vitro study of FOF found that SA increased the ability of the organism to produce fusaric acid, cellulase and pectinase, which increased the susceptibility of faba bean to Fusarium wilt. Interestingly, co‐cultivation with wheat significantly reduced the content of SA in exudates from the faba bean roots, which directly reduced the deleterious effects of SA. In addition, co‐cultivation could increase the activity of peroxidase and catalase, reduce the content of malondialdehyde, thus improving the ability of faba bean to defend itself. In conclusion, we found that SA, as an autotoxic substance, aggravates the occurrence of Fusarium wilt on faba bean and affects the growth of this crop. However, co‐cultivation of faba bean with wheat could alleviate this autotoxicity. This study has discovered a possible mechanism that could explain how co‐cultivation can alleviate the obstacles in cropping systems and control Fusarium wilt. [ABSTRACT FROM AUTHOR]

Recycled hydroponic solutions used for growing crops can accumulate allelochemicals that inhibit plant growth. We applied alternating current electrodegradation (AC-ED) to fresh nonrenewed nutrient solutions (i.e. solutions remaining unchanged throughout the culture period) and once-used nonrenewed solutions (i.e. solutions that had been used for a previous culture) for detoxifying autotoxic chemicals. Four experiments were conducted in which lettuce plants were grown in different nonrenewed solutions treated with AC-ED and in renewed solution that was not treated with AC-ED. Renewed solution (50% 'Enshi' solution) was changed at 14-day intervals. In fresh starting solutions, no substantial difference was found in shoot fresh weight (SFW) between renewed and AC-ED-treated nonrenewed solutions at different intervals (experiment I) and frequencies (experiment III), but notably, the lowest yield was recorded in non-renewed solution. In contrast, in the case of once-used nonrenewed solution, weekly (experiment II) and thrice-weekly and continuous (experiment IV) AC-ED application showed significantly higher SFW compared to values for other solutions, and the lowest value was also found in nonrenewed once-used culture solution. Therefore, we recommend the application of AC-ED to non-renewed solution either thrice weekly or continuously for efficient detoxification of accumulated allelochemicals to improve the growth, yield and quality of lettuce under two or more successive cultivations in recycled hydroponics. [ABSTRACT FROM AUTHOR]

Alfalfa is a leguminous plant with strong autotoxicity, which seriously affects regeneration and stability. In order to clarify the relationship between the key autotoxic substances and autotoxicity of alfalfa, this experiment determined the content of phenolic autotoxic substances in different varieties of alfalfa and the effect of different concentrations of alfalfa extracts on seed germination, seedling growth and physiology. The results showed that the content of single autotoxic substances in the eight alfalfa varieties was highest for total coumarin. The variety with the highest total coumarin content was “LZ”, and the lowest content was “656”. Principal component analysis of the autotoxicity of eight alfalfa varieties revealed that the variety with the strongest autotoxicity was “LZ” and the weakest was “656”. After treatment with extracts, the germination potential, germination rate, germination index and vigor index of 656 were higher than those of LZ, and the seeds of LZ and 656 did not germinate when the concentration was higher than C0.025 and C0.05, respectively. Compared with LZ, 656 had stronger osmotic regulation and antioxidant capacity, while the degree of membrane lipid peroxidation and ROS accumulation were lower. Further correlation analysis between the autotoxic substance content and autotoxicity observed that the content of total coumarin and autotoxic substances showed a significant positive association with autotoxicity (p < 0.01), and the total coumarin content showed a significant positive correlation with the content of autotoxic substances (p < 0.05). The total coumarin content is the major contributor to autotoxicity, and the higher the coumarin content, the higher the autotoxic substance content and the stronger the autotoxicity. Eight alfalfa varieties were systematically clustered on the basis of total coumarin content and autotoxicity, and the high-autotoxic alfalfa variety “LZ” and low-autotoxic alfalfa variety “656” were screened.

Plant invasive success is attributed to invaders’ ecological advantages over their native neighbors. However, increasing evidence suggests that these advantages are expected to attenuate over time because of natural enemy accumulation, ecological evolution of native species and autotoxicity. We determined how an invasive Ageratina adenophora could remain its competitive advantages over time by avoiding its autotoxicity. Our results highlighted that the autotoxicity of A. adenophora in its invaded soil was reduced by some microbes. Moreover, an autotoxic allelochemical, 2-coumaric acid glucoside, detected in the invaded soil, demonstrated distinctly autotoxic effects on its seed germination and seedling growth. However, the autotoxic effects were greatly alleviated by a bacterium Bacillus cereus, accumulated by A. adenophora. Furthermore, the allelochemical could be almost completely degraded by B. cereus within 96 h. Accordingly, we speculate that A. adenophora could aggregate B. cereus to release its autotoxicity maintaining its competitive advantages over time.

Background: The yield and quality of Pugionium cornutum (L.) Gaertn., a healthy, green vegetable with low sugar and high protein contents and high medicinal value, is severely affected by autotoxicity, which is a leading factor in the formation of plant disease. To help characterize the autotoxicity mechanism of P. cornutum (L.) Gaertn., we performed transcriptomic and metabolic analysis of the roots of P. cornutum (L.) Gaertn. response to phthalic acid, an autotoxin from P. cornutum (L.) Gaertn. Results: In this study, high-throughput sequencing of nine RNA-seq libraries generated from the roots.of P. cornutum (L.) Gaertn. under different phthalic acid treatments yielded 37,737 unigenes. In total, 1085 (703 upregulated and 382 downregulated) and 5998 (4385 upregulated and 1613 downregulated) DEGs were identified under 0.1 and 10 mmol·L− 1 phthalic acid treatment, respectively, compared with the control treatment. Glutathione metabolism was among the top five important enriched pathways. In total, 457 and 435 differentially accumulated metabolites were detected under 0.1 and 10 mmol·L− 1 phthalic acid treatment compared with the control, respectively, of which 223 and 253, respectively, increased in abundance. With the increase in phthalic acid concentration, the accumulation of ten metabolites increased significantly, while that of four metabolites decreased significantly, and phthalic acid, dambonitol, 4-hydroxy-butyric acid, homocitrulline, and ethyl β-D-glucopyranoside were 100 times more abundant under the 10 mmol·L− 1 phthalic acid treatment than under the control. Seventeen differentially expressed genes significantly associated with phthalic acid content were identified. In addition, the L-histidinol content was highest under 0.1 mmol·L− 1 phthalic acid, and a total of eleven differentially expressed genes were significantly positively correlated with the L-histidinol content, all of which were annotated to heat shock proteins, aquaporins and cysteine proteases. Conclusions: Accumulation of autotoxins altered the metabolic balance in P. cornutum (L.) Gaertn. and influenced water absorption and carbon and nitrogen metabolism. These important results provide insights into the formation mechanisms of autotoxicity and for the subsequent development of new control measures to improve the production and quality of replanted plants. [ABSTRACT FROM AUTHOR]

Background: Alfalfa crops are subject to intercalation when grown continuously on the same field, and autotoxicity appears to be another factor in this thinning. Alfalfa fields are often thinned out and have lower yields during consecutive production, and autotoxicity is increasingly found to be a major reason. Hence, Therefore, understanding the seed germination and seedling growth and physiological mechanisms of the alfalfa under continuous cropping system becomes important for sustainable the use of alfalfa grassland. Methods: The leaves, stem, root and rhizosphere soil of alfalfa (Medicago sativa L. cv ZhongMu No.1) were collected to determine the seedling growth germination index (GI) and vigor index (VI), physiological characters malondialdehyde (MDA), proline, soluble sugar (SS), soluble protein (SP), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Result: The germination rate, germination potential, germination index (GI) and vigor index decreased with the increasing extract contents, particularly in leaf extracts. In the extract of plant and soil, the concentration of malondialdehyde altered indistinctly, while the contents of osmo-regulatory substances and the activities of anti-oxidative enzymes generally decreased. Furthermore, the extract increased the seedling length of alfalfa and GI was negatively correlated with seedling growth characteristics. [ABSTRACT FROM AUTHOR]

To explore whether the allelopathy of Metasequoia glyptostroboides litter is an obstacle to its natural regeneration, eight concentrations (200, 100, 50, 20, 10, 5, 2, 1 g·L-1 and CK) of aqueous extracts from fresh and natural litter of M. glyptostroboides were set to analyze the allelopathic effects of aqueous extracts of different types and concentrations on seed germination and growth of M. glyptostroboides. The results were as follows:(1)The aqueous extract of the fresh M. glyptostroboides litter had no significant effects on seed germination rate and germination energy (P>0.05), but had significant effects on germination index (P<0.05), and seed germination was significantly inhibited by 1, 100, 200 g·L-1 treatments. The effects of aqueous extracts of the natural M. glyptostroboides litter on three indexes of seed germination were not significant (P>0.05), but the inhibitory effect was reflected in 5, 10, 50, 200 g·L-1. (2)The shoot length, hypocotyl length and main root length of M. glyptostroboides seeds were significantly different between different concentrations of fresh and natural litter aqueous extracts (P<0.05), and decreased gradually with the increase of aqueous extract concentrations (≥10 g·L-1), especially in the range from 50 to 200 g·L-1. (3)Compared with seed germination, the aqueous extracts of fresh and natural M. glyptostroboides litters had stronger inhibitory effect on the growth of seeds after germination, and the allelopathic effect of fresh litter was stronger than that of natural litter. (4)The main root length was the most sensitive to allelochemicals among seeds germination and growth indexes. (5)The dynamic change of shoot length growth of M. glyptostroboides seeds accords with the “S” type growth curve (R²≥0.988). In summary, the litter of M. glyptostroboides has a certain allelopathic inhibitory effect on its own seed germination and growth, which affects the natural regeneration of its population. It is suggested that the litter under the forest should be properly cleaned to promote the natural renewal of the M. glyptostroboides population in the management of M. glyptostroboides populations. [ABSTRACT FROM AUTHOR]

Ganoderma lucidum has been used as a rare medical mushroom for centuries in China, due to its health-promoting properties. Successive cropping obstacles are common in the cultivation of G. lucidum, although the remaining nutrients in the germ substrate are sufficient for a second fruiting. Here, we aimed to study the metabolite profile of G. lucidum via nontargeted metabonomic technology. Metabonomic data revealed that organic acids played an important role in the cropping obstacles of G. lucidum, which is accordance with the pH decrease in the germ substrate. A Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis indicated that most differential acids participated in the metabolic pathways. Five acids were all significantly upregulated by two MS with high energy (MSE) modes in two cultivars, among which 5-hydroxy-2-oxo-4-ureido-2,5-dihydro-1H-imidazole-5-carboxylic acid is also involved in purine metabolism regulation and microbial metabolism in diverse environments. Taken together, this work illustrated the organic acid stress generated by G. lucidum, which formed the autotoxicity feedback, and resulted in cropping obstacles. Determining the cause of the cropping obstacles in G. lucidum will promote the utilization rate of fungus substrate to realize the sustainable use of this resource. [ABSTRACT FROM AUTHOR]

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Pogostemon cablin (patchouli) cultivation is challenged by serious soil sickness, of which autotoxins accumulation is a major cause. p-hydroxybenzoic acid (p-HBA) is one of the main autotoxins of patchouli. However, the molecular mechanism underlying the response of patchouli to p-HBA remains unclear. In this study, RNA-sequencing combined with physiological analysis was used to monitor the dynamic transcriptomic and physiological changes in patchouli seedlings 0, 6, 12, 24, 48, and 96 h after p-HBA treatment. p-HBA stress inhibited root biomass accumulation, induced excessive hydrogen peroxide accumulation and lipid peroxidation, and activated most antioxidant enzymes. Compared with that of the control, the osmotic adjustment substance content was elevated with treatment. Subsequently, 15,532, 8,217, 8,946, 2,489, and 5,843 differentially expressed genes (DEGs) at 6, 12, 24, 48, and 96 h after p-HBA treatment, respectively, were identified in patchouli roots. GO functional enrichment analysis showed that the DEGs were enriched mainly in plasma membrane, defense response, response to chitin, DNA-binding transcription factor activity and abscisic acid-activated signaling pathway. The upregulated genes were involved in glycolysis/gluconeogenesis, cysteine and methionine metabolism, starch and sucrose metabolism, biosynthesis of unsaturated fatty acids, and linoleic acid metabolism. Genes associated with MAPK signaling pathway-plant, plantpathogen interaction, plant hormone signal transduction were downregulated with p-HBA treatment. These pathways are related to root browning and rotting, leading to plant death. [ABSTRACT FROM AUTHOR]

This paper summarizes the updated research on continuous cropping problem of Panax ginseng C.A. Meyer. (i). Current status of ginseng cultivation, (ii). Development of continuous cropping problem, (iii). Methods to alleviate the continuous cropping problems and (iv). Suggested future research to prevent development of continuous cropping problem in ginseng. [ABSTRACT FROM AUTHOR]

Allelopathic effect can lead to continuous cropping problem in plants. Mixed sowing of different species/varieties may overcome this problem. Two turfgrass (Festuca arundinacea Schreb.) varieties Millennium2 and Arid3 were studied for their growth potential in mixture and effects on growth of lawns. The results showed that the mixed sowing proportion had significant impact on the growth of turfgrass. The main variety 0 showed improved physiological indices and better growth in mixture ratio of 4:1. The variety Millennium2 was more sensitive to mixture than Arid3. GC-MS analysis showed that the root aqueous extracts of Millennium2 and Arid3 contained 15 and 22 allelopathic compounds, respectively, and the content of 1,1-diethoxy-3-methylbutane was highest. Both varieties shared 9-chemicals (1,1-Diethoxybutane, 2-methylpentanoyl 2-methylpentanoate, 1,1-diethoxy-3-methylbutane, octamethylcyclotetrasiloxan, 6-ethyl-2-methyloctane, 5-methylundecane, 4,6-dimethyldodecane, henicosane and icosane), while Arid3 and Millennium2 individually contained 13 and 6 unique compounds, respectively. Thus, the selection of compatible species/varieties and their suitable proportion is very important for ideal mixture to improve the appearance of lawn and ecological effects. [ABSTRACT FROM AUTHOR]

Microcystis blooms frequently occur in freshwaters worldwide, causing detrimental impacts on the ecosystems and human health. Studying the mechanisms behind the decline of Microcystis blooms can aid in mitigating their harmful effects. However, there is currently a dearth of research in this area. In this study, we examined the dissolved organic matter (DOM) collected during the growth of axenic Microcystis. Axenic Microcystis produces toxic DOM during its growth, which accumulate in the medium. Further, the DOM obtained from decline phase of Microcystis blooms exhibited a strong inhibitory effect on the growth of fresh Microcystis cultures. It is postulated that DOM may contribute to decline of Microcystis blooms. Meanwhile, potential autotoxic components in Microcystis DOM were analyzed by integrating column chromatography fractionation, identification and Microcystis growth inhibition assay. The results showed that the autotoxic components consisted mainly of small molecule hydrophobic base. Moreover, we evaluated the influence of key environmental factors such as nutrient and temperature on the autotoxic DOM in Microcystis cultures. Nutrient deficiency and low temperature may promote the accumulation of autotoxic substances. The study provided a new perspective on the decay process of cyanobacterial bloom, and offered new ideas for the development of natural algicidal agents., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Abstract Elymus nutans has been widely planted together with other perennial grasses for rebuilding degraded alpine meadow atop the Qinghai‐Tibetan Plateau. However, the rebuilt sown pastures begin to decline a few years after establishing. One of the possible causes for the degradation of sown grassland may come from allelopathy of planted grasses. The purpose of this study was to examine allelopathic potential of Elymus nutans. Three types of aqueous extract from Elymus nutans and its root zone soil were prepared, and 5 highland crops and 5 perennial grasses were used as recipient plants. Elymus nutans exhibited strong allelopathic potential on germination and seedling growth of 5 crops, but different crops or perennial grasses respond to the extract differently. The pieces aqueous extract have stronger inhibition than whole plant extract and root zone soil extract. Hordeum vulgar var. nudum, Avena sativa, and Festuca sinensis were the most affected, while Chenopodium quinoa and Elymus sibiricus were the least affected. Elymus nutans presented less influence on Poa pratensis and Poa crymophylla than on Festuca sinensis. It is recommended that the species combination of mixture for restoration should be considered for allopathic effects on the coseeding to decrease the seeding rate ratio of Elymus nutans. The annual dicot crop seeds of Chenopodium quinoa and Brassica napus can be used as alternative subsequent crop for the seed field of Elymus nutans monoculture.

To reveal the allelopathic effects of potato, seven compounds were isolated from the rhizosphere soil: 7-methoxycoumarin (1), palmitic acid (2), caffeic acid (3), chlorogenic acid (4), quercetin dehydrate (5), quercitrin (6), and rutin (7). Bioassays showed that compounds 1, 2, 4, and 6 had inhibitory effects on the growth of L. sativa and tissue culture seedlings of potato. The existence of the allelochemicals was confirmed by HPLC, and their contents were quantified with a total concentration of 9.02 μg/g in the rhizosphere soil of replanted potato. Approaches on the interactions of the allelochemicals and pathogens of potato including A. solani, B. cinerea, F. solani, F. oxysporum, C. coccodes, and V. dahlia revealed that compound 1 had inhibitory effects but compounds 2–4 promoted the colony growth of the pathogens. These findings demonstrated that the autotoxic allelopathy and enhancement of the pathogens caused by the accumulation of the allelochemicals in the continuously cropped soil should be one of the main reasons for the replant problems of potato. [ABSTRACT FROM AUTHOR]

Autotoxicity is a form of intraspecific allelopathy, in which a plant species inhibits the establishment or growth of the same species through the release of toxic chemical compounds into the environment. The phenomenon of autotoxicity in crops is best traced in alfalfa (Medicago sativa). A close relative of alfalfa, M. truncatula, has been developed into an excellent model species for leguminous plants. However, it is not known whether M. truncatula has autotoxicity. In this study, M. truncatula root exudates showed a negative impact on the growth of M. truncatula seedlings, indicating autotoxicity. Detailed analyses with plant extracts from M. truncatula and alfalfa revealed varying degrees of suppression effects in the two species. The extracts negatively affected seed germination potential, germination rate, radicle length, hypocotyl length, synthetic allelopathic effect index, plant height, root growth, fresh weight, dry weight, net photosynthetic rate, transpiration rate, and stomatal conductance in both M. truncatula and alfalfa. The results demonstrated that autotoxicity and allelopathic effects exist in M. truncatula. This opens up a new way to use M. truncatula as a model species to carry out in-depth studies of autotoxicity and allelopathy to elucidate biochemical pathways of allelochemicals and molecular networks controlling biosynthesis of the chemicals. [ABSTRACT FROM AUTHOR]

Soil microbial communities are critical for the productivity of agricultural systems. The effects of phenolic compounds on crops have been extensively studied recently, but less attention has been paid to how these compounds can affect the Pseudomonas and Bacillus communities in the soil, which are potential antagonistic pathogens and promote plant growth. In our microcosm experiment, soils were treated with different concentrations of syringic acid (a phenolic compound toxic to cucumber). Community structures and abundances of Pseudomonas and Bacillus species were estimated by PCR-denaturing gradient gel electrophoresis and quantitative PCR. Results showed that the number of DGGE bands, the Shannon-Wiener and Evenness indices of the Pseudomonas spp. community in all concentrations of syringic acid treatment were significantly higher than control, suggesting that the addition of syringic acid increased the Pseudomonas spp. community diversity. However, syringic acid increased the abundance of Bacillus spp. at 0.02 μmol g-1 and decreased the diversity and abundance of Bacillus spp. community at 0.05-0.2μmol g-1. Overall results showed that Pseudomonas and Bacillus spp. responded differently to SA and their structure and abundance varied with the concentration of SA in soil. [ABSTRACT FROM AUTHOR]