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Chui-hua Kong – One of the best experts on this subject based on the ideXlab platform.

  • Allelochemical mediated soil microbial community in long term monospecific chinese fir forest plantations
    Applied Soil Ecology, 2015
    Co-Authors: Zhichao Xia, Chui-hua Kong, Longchi Chen, Silong Wang

    Abstract:

    Abstract Productivity decline of monospecific forest plantations has remained a serious problem. Despite increasing knowledge of the problem involved in the build-up of soil-borne pathogens and allelopathy, relatively little is known about tree-derived Allelochemicals and their impacts on the soil microbial community and root growth. Therefore, the objective of this study was to examine a novel Allelochemical cyclic dipeptide in relation to the soil microbial community and phytotoxicity to tree roots in 25-year-old monospecific Chinese fir (Cunninghamia lanceolata) forest plantations. We sampled soils and fine roots in situ and quantified soil cyclic dipeptide, microbial and root characteristics along with their correlation analyses. When compared with soil from a plantation established following removal of natural forest vegetation, soil from a replanted plantation contained a greater amount of cyclic dipeptide. Furthermore, increased soil potentially pathogenic fungi and reduced root biomass, root surface area and root length density were observed in the replanted plantations. There were negative relationships among cyclic dipeptide concentration, microbial community composition and root biomass in given plantations. Phospholipid fatty acid profiling showed that the signature lipid biomarkers of soil bacteria and fungi, and soil microbial community structure were affected under cyclic dipeptide application. Soil degradation dynamics indicated that cyclic dipeptide declined rapidly. The results demonstrated that Allelochemical cyclic dipeptide not only had direct phytotoxicity to tree roots but also indirectly altered soil microbial community compositions, suggesting that productivity decline of continuous Chinese fir monocultures may be a negative feedback interaction between Allelochemical-mediated soil microbial community and root phytotoxicity.

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  • autoinhibition and soil Allelochemical cyclic dipeptide levels in replanted chinese fir cunninghamia lanceolata plantations
    Plant and Soil, 2014
    Co-Authors: Longchi Chen, Silong Wang, Peng Wang, Chui-hua Kong

    Abstract:

    Despite increasing knowledge of the role of Allelochemicals in the productivity decline of replanted Chinese fir plantations, relatively little is known about the levels and sources of Allelochemicals in relation to autoinhibition. Allelopathic potential of litter, root exudates, and soils in successive rotations of Chinese fir plantations were detected. An Allelochemical cyclic dipeptide (6-hydroxy-1,3-dimethyl-8-nonadecyl-[1,4]-diazocane-2,5-dione) from litter, root exudates, and soils in successive rotations was quantified. Extracts of leaf litter, fine root, and root exudates significantly inhibited the growth of Chinese fir germinants, and inhibition increased with successive rotations. Similar results were observed in the rhizosphere soil, basal soil, and bulk soil. The largest observed inhibition occurred in the rhizosphere soil. Furthermore, cyclic dipeptide was found in litter, root exudates, and soils, and the concentrations increased with successive rotations. The rhizosphere soil had the highest cyclic dipeptide level, followed by basal soil, while bulk soil contained the lowest concentration. There was a significant positive relationship between the inhibition of radicle growth of Chinese fir germinants and the concentration of cyclic dipeptide. Annual release of cyclic dipeptide through root exudation was 2.08–9.78 mol ha−1 annum, but the annual release of cyclic dipeptide through leaf litter decomposition was lowered to 0.32–1.41 mol ha−1 annum. Cyclic dipeptide which caused autoinhibition of Chinese fir may be released into the soil through litter decomposition and root exudation. Root exudates provided more contributions to soil cyclic dipeptide levels than litter in Chinese fir plantations.

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  • chemical constituents of the essential oils of wild oat and crabgrass and their effects on the growth and Allelochemical production of wheat
    Weed Biology and Management, 2013
    Co-Authors: Bin Zhou, Chui-hua Kong, Peng Wang

    Abstract:

    The interference of allelopathic weeds with crop plants might be mediated by volatile Allelochemicals. In this study, the essential oil constituents of two weeds, wild oat (Avena fatua) and crabgrass (Digitaria sanguinalis), were investigated in relation to their effects on the growth and Allelochemical production of wheat (Triticum aestivum). Subsequently, by means of gas chromatography and gas chromatography-mass spectrometry, 52 compounds were identified from the crabgrass essential oil, particularly a signaling compound called methyl jasmonate, while 28 constituents were detected in the wild oat essential oil. Both essential oils were rich in terpenoids and inhibited the growth of wheat in air, filter paper and soil media but their inhibition varied with the growth medium and the weed species. In both the air and the filter paper media, there were not significant differences in the dry weight of wheat between the wild oat and the crabgrass essential oils. However, there was a greater reduction in the dry weight of the wheat root and plant with the wild oat essential oil than with the crabgrass essential oil in the soil medium. Furthermore, the production of the Allelochemical, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one, in wheat was induced by the essential oils. The results suggest that allelopathic interference with wheat by wild oat and crabgrass affects not only the biomass allocation, but also the Allelochemical production, of wheat.

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Yiwen Zhang – One of the best experts on this subject based on the ideXlab platform.

  • characterization of Allelochemicals of the diatom chaetoceros curvisetus and the effects on the growth of skeletonema costatum
    Science of The Total Environment, 2019
    Co-Authors: Yiwen Zhang, Jiangtao Wang

    Abstract:

    Abstract Allelopathy has been regarded as chemical weapons for marine phytoplankton that enhanced competition ability in stressful conditions, especially during blooms. In a previous study, Chaetoceros curvisetus achieved growth advantage to Skeletonema costatum by producing Allelochemicals. However, C. curvisetus Allelochemicals have never been isolated and characterized until now. In this study the extraction and purification conditions were systematically optimized and C. curvisetus filtrate extracts were used to assess bioactive effects on the growth of S. costatum. The preliminary results showed that filtrates of C. curvisetus in exponential phase extracted under a temperature lower than 50 °C could ensure a stronger activity of Allelochemicals. Ethyl acetate extraction showed significant allelopathic effect and the wavelength of characteristic absorption was 255–260 nm. Then C. curvisetus Allelochemicals were isolated by Si-SPE, Sephadex-25 columns and C18 column and identified by HPLC-electrospray time-of-flight mass spectrometry (ESI TOFMS). It was found that the molecular weight of C. curvisetus Allelochemicals was 314 and the Allelochemical was supposed to be 2- ((2-cyanophenyl) amino)-2-oxoethyl,3-cyclohexyl propanoate.

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  • characterization of Allelochemicals of the diatom chaetoceros curvisetus and the effects on the growth of skeletonema costatum
    Science of The Total Environment, 2019
    Co-Authors: Yiwen Zhang, Jiangtao Wang

    Abstract:

    Abstract Allelopathy has been regarded as chemical weapons for marine phytoplankton that enhanced competition ability in stressful conditions, especially during blooms. In a previous study, Chaetoceros curvisetus achieved growth advantage to Skeletonema costatum by producing Allelochemicals. However, C. curvisetus Allelochemicals have never been isolated and characterized until now. In this study the extraction and purification conditions were systematically optimized and C. curvisetus filtrate extracts were used to assess bioactive effects on the growth of S. costatum. The preliminary results showed that filtrates of C. curvisetus in exponential phase extracted under a temperature lower than 50 °C could ensure a stronger activity of Allelochemicals. Ethyl acetate extraction showed significant allelopathic effect and the wavelength of characteristic absorption was 255–260 nm. Then C. curvisetus Allelochemicals were isolated by Si-SPE, Sephadex-25 columns and C18 column and identified by HPLC-electrospray time-of-flight mass spectrometry (ESI TOFMS). It was found that the molecular weight of C. curvisetus Allelochemicals was 314 and the Allelochemical was supposed to be 2- ((2-cyanophenyl) amino)-2-oxoethyl,3-cyclohexyl propanoate.

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Helene Hegaret – One of the best experts on this subject based on the ideXlab platform.

  • Allelochemicals from Alexandrium minutum induce rapid inhibition of metabolism and modify the membranes from Chaetoceros muelleri
    Algal Research – Biomass Biofuels and Bioproducts, 2018
    Co-Authors: Marc Long, Kevin Tallec, Philippe Soudant, Fabienne Le Grand, Anne Donval, Christophe Lambert, Géraldine Sarthou, Dianne Jolley, Helene Hegaret

    Abstract:

    Allelochemical interactions are likely to be a contributing factor explaining the success of large blooms of the harmful marine dinoflagellate Alexandrium, however, the physiological mechanisms of Allelochemical interactions remain poorly described. Here we investigated the sub-lethal effects (on an hourly scale) of a filtrate containing Allelochemicals from Alexandrium minutum on the physiology of the common diatom Chaetoceros muelleri. The filtrate induced deleterious effects to the diatom physiology within only 30 min of exposure. Esterase activity and photosynthesis were drastically inhibited, with up to 34% of the population being metabolically inactive and up to 30% reduction in photosystem II quantum yield when exposed to the filtrate. In addition, intracellular reactive oxygen species increased by 26% in response to Allelochemical exposure. C. muelleri pigment and lipid analyses indicated that the photosystem II was inhibited, with photoinhibition-like responses (activation of xanthophyll cycles, and changes in associated lipids) upregulated to mitigate the toxic effects of Allelochemicals. Changes in the proportions of membrane lipid classes and increased membrane fatty acids saturation by 9% may be an attempt to maintain membrane integrity and associated enzyme activity, or could be the result of deleterious effects on membranes. An 8% decrease in cellular storage lipids (triglycerides) revealed a mobilization of energy suggesting an energetic cost for the diatom to counteract the Allelochemical effects. We hypothesize that the rapid alteration of physiological functions such as photosynthesis and some enzymatic activities may result from direct damage on external membranes. Overall this study describes the sub-lethal mechanisms and provides useful biomarkers to understand the role of Allelochemical interactions and associated ecological processes in structuring plankton communities.

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  • A rapid quantitative fluorescence-based bioassay to study Allelochemical interactions from Alexandrium minutum
    Environmental Pollution, 2018
    Co-Authors: Marc Long, Kevin Tallec, Philippe Soudant, Fabienne Le Grand, Christophe Lambert, Géraldine Sarthou, Dianne Jolley, Helene Hegaret

    Abstract:

    Harmful microalgal blooms are a threat to aquatic organisms, ecosystems and human health. Toxic dinoflagellates of the genus Alexandrium are known to produce paralytic shellfish toxins and to release bioactive extracellular compounds (BECs) with potent cytotoxic, hemolytic, ichtyotoxic and allelopathic activity. Negative Allelochemical interactions refer to the chemicals that are released by the genus Alexandrium and that induce adverse effects on the physiology of co-occurring protists and predators. Releasing BECs gives the donor a competitive advantage that may help to form dense toxic blooms of phytoplankton. However BECs released by Alexandrium minutum are uncharacterized and it is impossible to quantify them using classical chemical methods. Allelochemical interactions are usually quantified through population growth inhibition or lytic-activity based bioassays using a secondary target organism. However these bioassays require time (for growth or microalgal counts) and/or are based on lethal effects. The use of pulse amplitude modulation (PAM) fluorometry has been widely used to assess the impact of environmental stressors on phytoplankton but rarely for Allelochemical interactions. Here we evaluated the use of PAM and propose a rapid chlorophyll fluorescence based bioassay to quantify Allelochemical BECs released from Alexandrium minutum. We used the ubiquitous diatom Chaetoceros muelleri as a target species. The bioassay, based on sub-lethal effects, quantifies Allelochemical activity from different samples (filtrates, extracts in seawater) within a short period of time (2 h). This rapid bioassay will help investigate the role of Allelochemical interactions in Alexandrium bloom establishment. It will also further our understanding of the potential relationship between Allelochemical activities and other cytotoxic activities from BECs. While this bioassay was developed for the species A. minutum, it may be applicable to other species producing Allelochemicals and may provide further insights into the role and impact of Allelochemical interactions in forming dense algal blooms and structuring marine ecosystems.

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