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    Effects of natural herbicide from tagetes erecta on echinochloa crus-galli (L.) beauv
    (2018-01-01)
    Wichittrakarn, P.
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    We studied the inhibitory effects of leaves extracts of Tagetes erecta on weed-seed germination and the mechanisms involved. Hydroethanolic crude extract (OR) from Tagetes erecta dried leaves was partitioned into four fractions: hydrolyzed (HY), aqueous (AQ), neutral (NE) and acidic (AE). The inhibitory effects of crude extracts and its fractions were evaluated on germination and seedlings growth of Echinochloa crus-galli (L.) Beauv. The total phenolic and flavonoid contents of each fraction were also determined. Germination and seedling growth were drastically inhibited by HY and AE followed by NE, OR and AQ. The HY and AE fractions had higher concentrations of both phenolics and flavonoids than other fractions. The HY fraction was selected as most potent for development as natural herbicide due to its high yield and strong inhibitory effects. The HY fraction was formulated into a soluble concentrate product (SCT) and its inhibition potential and modes of action were investigated. The SCT drastically inhibited the seed germination of E. crus-galli, inhibiting both imbibition, α-amylase activity and also seedling growth. Cytogenetic bioassays of SCT on root-tip cells of Allium cepa L. showed that it inhibited the mitosis and thereby the cell division. It is likely that a natural herbicide may be developed from the hydrolyzed fraction of a hydroethanolic extract of Mexican marigold leaves.
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    Potential allelopathic effects of Suregada multiflorum and the influence of soil type on its residue's efficacy
    (2010-09-01) ;
    Boonleom, Chaninat
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    Thitavasanta, Sompop
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    This experiment was conducted to determine the potential allelopathic effects of the aqueous extracts and dried leaf powder of Suregada multiflorum and to find the herbicidal effects of its granule on the weed species, barnyardgrass (Echinochloa crus-galli) and slender amaranth (Amaranthus viridis), in various growth media (germination paper, sand, and soil). Observations in this study demonstrated that the potential and magnitude of their inhibitory effects varied among the plant parts. The leaves and branches possessed the strongest inhibition levels, followed by the bark. The aqueous extract from the leaves of S. multiflorum had a remarkably stronger inhibitory effect on the germination and growth of slender amaranth, compared with barnyardgrass; when applied at the concentration of 100-g-L<sup>-1</sup>, it completely inhibited the germination and initial seedling growth of slender amaranth. In addition, all the treatments of the dried leaf powder had stronger inhibition effects than the aqueous extract. Interestingly, the inhibitory effects of the dried leaf granule of S. multiflorum were stronger than the effects of the dried leaf powder at equal rates. The degree of inhibitory effect of the S. multiflorum granule, applied in various growing media, can be classified in order of decreasing inhibition as germination paper = sand > clay soil. The present study indicates that the S. multiflorum granule product that was developed in this research has the potential to provide a powerful organic herbicide for controlling slender amaranth. © 2010 The Authors. Journal compilation © 2010 Weed Science Society of Japan.
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    Inhibitory effects of a variety of aldehydes on Amaranthus tricolor l. And echinochloa crus-galli (L.) beauv.
    Thirty-seven commercial aldehydes containing aliphatic chains and aromatic rings as well as heteroaromatic rings were evaluated for their inhibitory activities against Chinese amaranth (Amaranthus tricolor L.) and barnyardgrass (Echinochloa crus-galli (L.) Beauv). Polysorbate 80 (Tween<sup>fi</sup> 80) was used as a surfactant and the research was preliminarily conducted at 400 µM of all aldehydes. Among these aldehydes, (E)-cinnamaldehyde (7) showed the greatest inhibitory effect on seed germination, shoot and root growth of Chinese amaranth by 54.55%, 75.53%, and 85.13% respectively. Similarly, (E)-crotonaldehyde (5), a related α,β-unsaturated aldehyde, inhibited the germination and seedling growth of the tested species at a high percentage. Apart from these two unsaturated aldehydes, no other aliphatic aldehydes had a harmful effect on Chinese amaranth. In terms of benzaldehyde (6), it had no effect on the tested plant; however, many of its derivatives displayed some inhibitory activity. Furthermore, for the ten common heteroaromatic aldehydes, picolinaldehyde (32) had a high inhibitory effect on Chinese amaranth which closely related to the effect of (E)-crotonaldehyde (5) and (E)-cinnamaldehyde (7), whereas, other heteroaromatic aldehydes showed lower effects. In the case of a monocot plant, barnyardgrass, no tested aldehydes reduced seed germination, however, (E)-cinnamaldehyde (7), 2,4,6-trimethoxybenzaldehyde (16) and 4-(dimethylamino)benzaldehyde (24) could inhibit the seedling growth of the plant with low to moderate levels. The herbicidal effects of the most active aldehydes were then further investigated in order to find the minimum concentration of these aldehydes suppressing the germination and growth of the tested plants. At concentrations as low as 50–100 µM some aldehydes could inhibit the seedling growth of the tested species. The structure-activity relationship (SAR) study reported here demonstrates the chemical clues governing the inhibitory activity of aldehydes which could be utilized in the development of highly effective herbicides in the near future.
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    Evaluation of allelopathic, decomposition and cytogenetic activities of Jasminum officinale L. f. var. grandiflorum (L.) Kob. on bioassay plants
    Methanolic extracts prepared from dried leaves of Jasminum officinale f. var. grandiflorum (L.) Kob. (Spanish jasmine) inhibited seed germination and stunted both root and shoot length of the weeds Echinochloa crus-galli (L.) Beauv. and Phaseolus lathyroides L. The main active compound was isolated and determined by spectral data as a secoiridoid glucoside named oleuropein. In addition, a decrease in allelopathic efficacy appeared as the decomposition periods increased. The mitotic index in treated onion root tips decreased with increasing concentrations of the extracts and longer periods of treatment. Likewise, the mitotic phase index was altered in onion incubated with crude extract. Furthermore, crude extract produced mitotic abnormalities resulting from its action on chromatin organization and mitotic spindle. © 2010 Elsevier Ltd. All rights reserved.
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    Effects of Spirulina platensis and C-phycocyanin on seed germination and seedling growth of two monocot and dicot plants
    (2010-01-01) ;
    Chotsaeng, P.
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    In laboratory bioassay the allelopathic effects of Spirulina platensis (nordst) Geitl. were investigated on Chinese amaranth (Amaranthus tricolor L.), Chinese mustard (Brassica campestris var. chinensis), barnyardgrass (Echinochloa crus-galli [L.] Beauv.) and rice (Oryza sativa L.). The seeds were germinated in Petri dishes with aqueous extract (0.625-5% concentrations) and crude organic extract (250-4000 ppm concentrations) distilled water used as control. All aqueous extracts influenced the seed germination and seedling growth of dicotyledons (A. tricolor and B. campestris). The aqueous extract of 1.25% and 2.50% concentration completely inhibited the germination in dicots. In monocots (barnyardgrass and rice), the aqueous extract of 2.50% concentration inhibited the root length, while the 5% concentration completely inhibited their germination and seedling shoot length. The UV-VIS spectra indicated that the aqueous extract contained C-phycocyanin (C-PC), with a purity ratio (A <inf>620</inf>/A<inf>280</inf>) of 1.17. The allelopathic activity of biologically active protein pigment, C-PC, was assayed on seed germination and seedling growth at 62.50-1000 ppm concentrations. At 1000 ppm, this compound was most inhibitory to shoot and root length of A. tricolor and B. campestris, but there was no effect on germination. The crude ethyl acetate extract was most inhibitory to dicots, but all three crude organic extracts were not inhibitory to monocots.
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    Herbicidal Activity of Flavokawains and Related trans-Chalcones against Amaranthus tricolor L. And Echinochloa crus-galli (L.) Beauv.
    Flavokawains have a broad spectrum of biological activities; however, the herbicidal activity of these naturally occurring chalcones has been less investigated. Flavokawains and their analogues were prepared by the Claisen-Schmidt condensation reaction between xanthoxyline (or aromatic ketones) and a variety of aromatic and heteroaromatic aldehydes. These compounds were then evaluated for their inhibitory effect against representative dicot and monocot plants. Among 45 synthetic chalcones, derivatives containing phenoxyacetic acid, 4-(N,N-dimethylamino)phenyl, N-methylpyrrole, or thiophenyl groups inhibited the germination and growth of Chinese amaranth (Amaranthus tricolor L.) with moderate to high degrees compared to commercial butachlor. For barnyardgrass (Echinochloa crus-galli (L.) Beauv.), most of the thiophenyl chalcones interrupted shoot and root emergence. This finding highlighted the importance of functional groups on the herbicidal activity of chalcones. The level of inhibition also depended on the applied concentrations, plant species, and plant organs. (E)-2-(2-(3-Oxo-3-(thiophen-2-yl)prop-1-enyl)phenoxy)acetic acid (14f) was the most active compound among 45 derivatives. This chalcone could be a promising structure for controlling the germination and growth of weeds. The structure-activity relationship results provide useful information about the development of active chalconoids as novel natural product-like herbicides.
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    Physiological and cellular mechanisms of natural herbicide resource from Aglaia odorata Lour. On bioassay plants
    A bioassay-guided fractionation of the allelochemicals of the ethyl acetate fraction extracted from Aglaia odorata led to isolation of a bisamide, odorine. The growth inhibitory effects of odorine and ethyl acetate fraction were studied for comparison on Echinochloa crus-galli. Odorine and ethyl acetate fraction of A. odorata could inhibit the germination and seedling growth of E. crus-galli, with ethyl acetate fraction being more potent. Thus, ethyl acetate fraction was selected for further experiment, E. crus-galli seeds were studied the effects of the ethyl acetate fraction from A. odorata leaves in wet-table powder formulation on imbibition and α-amylase activity. It was found that treated seeds showed lower imbibition and α-amylase activity. The results of cytogenetic bioassay in Allium cepa roots showed that ethyl acetate fraction inhibited cell mitosis and induced mitotic abnormalities resulting from its action on chromatin organization and mitotic spindle in the exposed roots.
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    An allelopathic substance isolated from Zanthoxylum limonella Alston fruit
    Bioassay-guided fractionation of the ethyl acetate extract of the Zanthoxylum limonella Alston fruits led to the isolation of a phenolic compound named xanthoxyline. The allelopathic effects of xanthoxyline were evaluated on Chinese amaranth (Amaranthus tricolor L.) and Barnyardgrass (Echinochloa crus-galli (L.) Beauv.) under laboratory conditions. At a concentration of 2500 μM, xanthoxyline completely inhibited seed germination and growth of Chinese amaranth, while this compound showed a significantly inhibitory effect on seed germination of Barnyardgrass by 43.59% and inhibited shoot and root length by 71.56% and 87.48%, respectively. To determine the mechanism through which xanthoxyline exerts its toxicity, the cytogenetic bioassay was conducted. Roots of Allium cepa L. (onion) were treated with a series of concentrations, ranging from 15.625 to 125 μM for 18 h. Cytogenetic studies of onion roots showed a decrease of the mitotic index in the exposed roots dependent on the concentration of xanthoxyline. Likewise, the mitotic phase index was altered in onion incubated with xanthoxyline. Analyses of the abbreviation types showed spindle disturbances at late prophase, sticky metaphase, c-mitosis, non-oriented chromosome at metaphase, sticky anaphase, delayed anaphase and diagonal at telophase for the onion roots exposed to xanthoxyline. © 2010 Elsevier B.V. All rights reserved.
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    Herbicidal activities of some allelochemicals and their synergistic behaviors toward amaranthus tricolor L.
    Seven allelochemicals, namely R-(+)-limonene (A), vanillin (B), xanthoxyline (C), vanillic acid (D), linoleic acid (E), methyl linoleate (F), and (±)-odorine (G), were investigated for their herbicidal activities on Chinese amaranth (Amaranthus tricolor L.). At 400 μM, xanthoxyline (C) showed the greatest inhibitory activity on seed germination and seedling growth of the tested plant. Both vanillic acid (D) and (±)-odorine (G) inhibited shoot growth, however, apart from xanthoxyline (C), only vanillic acid (D) could inhibit root growth. Interestingly, R-(+)-limonene (A) lightly promoted root length. Other substances had no allelopathic effect on seed germination and seedling growth of the tested plant. To better understand and optimize the inhibitory effects of these natural herbicides, 21 samples of binary mixtures of these seven compounds were tested at 400 μM using 0.25% (v/v) Tween(r) 80 as a control treatment. The results showed that binary mixtures of R-(+)-limonene:xanthoxyline (A:C), vanillin:xanthoxyline (B:C), and xanthoxyline:linoleic acid (C:E) exhibited strong allelopathic activities on germination and seedling growth of the tested plant, and the level of inhibition was close to the effect of xanthoxyline (C) at 400 μM and was better than the effect of xanthoxyline (C) at 200 μM. The inhibition was hypothesized to be from a synergistic interaction of each pair of alleochemicals. Mole ratios of each pair of allelochemicals ((A:C), (B:C), and (C:E)) were then evaluated, and the best ratios of the binary mixtures A:C, B:C and C:E were found to be 2:8, 2:8, and 4:6 respectively. These binary mixtures significantly inhibited germination and shoot and root growth of Chinese amaranth at low concentrations. The results reported here highlight a synergistic behavior of some allelochemicals which could be applied in the development of potential herbicides.
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    Phytotoxic effects of essential oil from Cymbopogon citratus and its physiological mechanisms on barnyardgrass (Echinochloa crus-galli)
    (2013-01-01)
    Poonpaiboonpipat, Tanatson
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    Pangnakorn, Udomporn
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    Suvunnamek, Umporn
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    Lemongrass (Cymbopogon citratus) essential oil was identified by GC-MS for their major compound constituents; six compounds representing 92.59% of the total essential oil were identified. The main constituent was citral (76.00%). In a laboratory bioassay, high concentration of essential oil significantly inhibited germination and seedling growth of Echinochloa crus-galli and affecting α-amylase activity of seeds. In a glass house bioassay, essential oil at concentrations of 1.25, 2.5, 5 and 10% (v/v) was foliar-applied on E. crus-galli at 28 days after sowing at spray volume of 1000Lha <sup>-1</sup>. Observation of leaf wilt symptoms was noted at 6h after treatment. Chlorophyll a, b and carotenoid content was decreased with concentrations of essential oil, indicating that essential oil interferes with photosynthetic metabolism. C. citratus essential oil caused an electrolyte leakage indicating membrane disruption and loss of integrity. Treated leaves exhibited an increase in thiobarbituric acid reactive substances (TBARS), suggesting lipid peroxidation. It is to conclude that essential oil is phytotoxic and could be utilized as a natural herbicide for future weed control. © 2012 Elsevier B.V.