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Medicinal plants are rich sources of bioactive phytochemicals. Production of such chemicals usually increased under unfavorable conditions. This study investigated the phytotoxic potential of 105 medicinal plants distributed in arid/semiarid areas along Arabian Sea coast of Pakistan. Total polyphenols, flavonoids, tannins and composition of individual phenolic compounds were also determined in species which showed high phytotoxic potential. Sandwich method was used to determine the phytotoxicity of medicinal plants on the growth of lettuce seedlings. Radicle growth was inhibited more than the hypocotyl growth. In general, halophytes showed higher phytotoxic potential than non-halophytes. Capparis cartilaginea, Indigofera hochstetteri, Parkinsonia aculeata and Prosopis glandulosa showed highest degree of inhibition. Higher amount of total phenols (16.35–25.33 mg GAE g−1), flavonoids (3.32-6.41 mg QE g−1) and tannins (1.54–2.54 mg TAE g−1) were found in these species. Pyrocatechol, quercetin, gallic, hydroxybenzoic and ferulic acids were detected as major phytotoxins, of which, gallic acid, pyrocatechol and quercetin were most abundant. These phytochemicals could be used for the production of natural, safe, healthy and eco-friendly agro-chemicals. Furthermore, these plants can be grown without encroaching agricultural lands, and can convert vast areas of arid/saline lands into economically viable resources, which also helps to halt climate change and desertification. [ABSTRACT FROM AUTHOR]

The physiological and biochemical mechanisms of organogenesis in Equisetum arvense have not been clarified yet. However, high concentrations of nitrogen have been shown to exert an inhibitory effect on in vitro tuber formation in E. arvense. The aim of this study was to clarify the influence of the form of nitrogen in a medium on in vitro organogenesis in E. arvense. Single-node segments of E. arvense rhizomes were cultured in the test medium. The NH4-N and NO3-N concentrations of the test medium, respectively, were adjusted by adding NH4H2PO4 and KNO3 to the basal medium. The basal medium was a nitrogen-free, modified form of White's medium. Vegetative shoots were newly formed in the test tubes for concentrations of NO3-N and NH4-N that exceeded 56 mg L−1. However, no rhizome was formed at NH4-N concentrations exceeding 28 mg L−1. The number of newly formed tubers decreased at an NH4-N concentration of 28 mg L−1 and no tuber was formed at NH4-N concentrations exceeding 56 mg L−1. In summary, although the presence of NO3-N in the medium did not inhibit in vitro rhizome or tuber formation in E. arvense, the presence of NH4-N in the medium exerted a strong inhibitory effect on the in vitro formation of both of these organs. [ABSTRACT FROM AUTHOR]

The article provides a study to establish a tissue culture system for tuber formation in Equisetum arvense. Equisetum arvense tubers were gathered and sterilized for five minutes using a one percent sodium hypochlorite solution. New rhizomes were cut into single node segments. The results of the study are offered in the article.

In order to elucidate the allelopathic effect of leaf litter leachates under laboratory conditions, a modified ‘sandwich method’, which places leaves between two layers of agar, was used. Fifty mg of leaves was used per 10 cm2 cell. Agar concentrations at 0.5–1.0% were the best for gel support in determining radicle and hypocotyl elongation of lettuce. The optimum incubation time for bioassay was three days after imbibition onset. Among 20 typical tree species in Asia, Cymbopogon citratus and Derris scandens showed the strongest inhibitory activity determined by the sandwich method, followed by Piper betle, Tamarindus indica, and Gliricidia sepium. This bioassay seems to be a reliable method for screening allelopathic activity from leaf litter leachates. [ABSTRACT FROM AUTHOR]

Examines the allelopathic activity of medicinal plant species using the sandwich method in Japan. Growth in the radicle and hypocotyl of lettuce seedlings; Inhibitory and promotive responses of the plant species to the radicle growth of lettuce; Significance on the allelopathic activity in Garcinia oblongifolia.

Platycodon is a medicinal plant of considerable pharmacological and dietary value. With the growing demand, agricultural production is increasing. However, the continuous cropping significantly causes negative impacts on its yield and quality. In this study, in order to solve the problem of continuous cropping, we evaluated the allelopathic activity of Platycodon and investigated the potential use of activated carbon for mitigating the negative impacts of allelopathic chemicals produced by Platycodon. The sandwich method (method for assaying the allelopathic activity of each part of a plant) was employed to evaluate the allelopathic activity of different parts (leaves, stems, and roots) of Platycodon. The inhibitory effects of various Platycodon plant parts were assessed based on their effects on lettuce seedling growth. At a concentration of 10 mg parts/10 mL agar, the average inhibition rates of Platycodon leaves on the radicle and hypocotyl growth of lettuce were 79.4% and 61.8%, stems 58.0% and 45.7%, and roots 53.4% and 49.3%, respectively. At a concentration of 50 mg parts/10 mL agar, the inhibitory effects were as follows: leaves (91.9%, 72.2%), stems (79.5%, 60.3%), and roots (71.4%, 65.2%). The effect of activated carbon on the adsorption of allelopathic substances was investigated, and the results of the sandwich method with a concentration of 10 mg parts/10 mL agar showed the following growth-inhibitory effects on lettuce seedlings and hypocotyls—roots (27.8%, 25.7%), leaves (13.3%, 25.7%), and stems (9.1%, 13.6%)—in each case showing a significant decrease in the inhibitory activity. The plant box method (method for assaying the allelopathic activity of plant root exudates) was employed to evaluate the activity of Platycodon root exudate. The growth inhibition rates of lettuce radicle and hypocotyls were 45.5% and 18.9%, respectively. The plant box method with addition of activated carbon revealed average rates of promotion of 16.7% and 4.7% on the growth of lettuce seedlings and hypocotyls, respectively. The results of this study demonstrated that activated carbon has a mitigating effect on allelopathic inhibition associated with the different plant parts and root exudation of Platycodon and provide a potential solution for overcoming problems associated with the continuous cropping of Platycodon. [ABSTRACT FROM AUTHOR]

Weeds pose major constraints in crop production. The use of allelochemicals and allelopathic species can provide an effective alternative for sustainable weed management. In a previous study that evaluated the allelopathic activity of wild and cultivated plants in Turkey, Hibiscus sabdariffa demonstrated the strongest inhibitory potential. This study aimed to estimate the phytotoxic influence of the H. sabdariffa water crude extracts on Lactuca sativa L. in a bioassay experiment. High-performance liquid chromatography (HPLC) analysis was used to identify two major compounds, hydroxycitric acid lactone and hydroxy citric acid, and their plant growth inhibitory activities were evaluated by bioassays. Hydroxycitric acid lactone had a stronger growth inhibitory activity on L. sativa L. and was estimated as a major allelochemical in H. sabdariffa calyx. The high concentration (16.7% of the dry weight of the calyx) and strong inhibitory effect (EC50, 73.7 ppm) of the hydroxycitric acid lactone could demonstrate the growth inhibitory activity of the H. sabdariffa calyx extract. This study showed that hydroxycitric acid lactone, a major compound in the calyx of Hibiscus sabdariffa, is a plant growth inhibitor. [ABSTRACT FROM AUTHOR]

Herein, we describe a highly potent gravitropic bending inhibitor with no concomitant growth inhibition. Previously, we reported that (2Z,4E)-5-phenylpenta-2,4-dienoic acid (ku-76) selectively inhibits root gravitropic bending of lettuce radicles at 5 μM. Based on the structure–activity relationship study of ku-76 as a lead compound, we designed and synthesized various C4-substituted analogs of ku-76. Among the analogs, 4-phenylethynyl analog exhibited the highest potency for gravitropic bending inhibition, which was effective at only 0.01 μM. Remarkably, 4-phenylethynyl analog is much more potent than the known inhibitor, NPA. Substitution in the para position on the aromatic ring of 4-phenylethynyl group was tolerated without diminished activity. In addition, evaluation using Arabidopsis indicated that 4-phenylethynyl analog inhibits gravitropism by affecting auxin distribution in the root tips. Based on the effects on Arabidopsis phenotypes, 4-phenylethynyl analog may be a novel inhibitor that differs in action from the previously reported auxin transport inhibitors. [ABSTRACT FROM AUTHOR]

Blueberry production in the field faces several challenges, including competition from weeds and soil suitability. Different mulch types are widely used in blueberry cultivation to control weeds, conserve moisture, and mitigate soil erosion. However, the comparative effects of loose and compressed wood chips on fruit quality and weed control in blueberry production systems have not been studied. Many farmers use expensive imported peat moss as soil covers, while others apply organic mulches such as chips or chaff, which can be easily washed away by runoff. This study aimed to evaluate the effects of compressed mulching boards (MB) fabricated without the use of chemical adhesives using pressurized steam and compression technologies in blueberry cultivation. During the two growing seasons, the effectiveness of compressed MB on soil moisture retention, fruit quality, and weed biomass was compared to that of wood chip (WC) and control treatments in a blueberry field. Although a significant difference was observed in the fruit fresh weight, no significant differences were observed in the other fruit growth parameters for all the treatments. Generally, the compressed MB significantly improved soil moisture retention capacity compared to WC and control during the two-year study. The compressed MB showed effective weed suppression ability by significantly reducing the weed biomass at all sampling times. [ABSTRACT FROM AUTHOR]

Allelopathy is a physiological process with an ecological concept and application. Allelopathy is the result of the production of biologically active molecules by growing plants or their remains, which may have a direct effect on the growth and development of individuals of the same species or other species after changing their shape and entering the environment. As regards, the use of natural compounds in the control of weeds and pests is a priority. In this research, the allelopathic activity of 123 specimens of medicinal and aromatic plants were investigated individually by the dish-pack method using lettuce seeds as a model. Then, the strongest inhibitory ones were selected and their allelopathic interaction effects were investigated for the first time by interacting them together. Two methods were used to evaluate allelopathic interaction effects: calculating Fractional Inhibitory Concentration (FIC) and drawing Isobologram diagrams. Lettuce hypocotyl length, root length, germination percentage, and germination rate were investigated. Pelargonium graveolens (leaf) had the greatest inhibitory effect on lettuce radicle growth (EC50 = 5.31 mg/well) and Echinophora platyloba (stem) had the greatest effect on hypocotyl growth inhibition (EC50 = 7.91 mg/well). Also, the lowest lettuce germination percentages were observed in the treatments Lavandula officinalis (flower) and Nepeta binaloudensis (leaf), respectively (23.61, 22.85%). The highest inhibitory effect by considering lettuce germination rate was detected in Salvia ceratophylla (leaf), (12.86 seed/day) and the lowest belonged to Nepeta binaloudensis (leaf) and Lavandula officinalis (flower), respectively (3.60, 3.32 seed/day). According to FIC calculations and isobolograms, two types of interaction, including synergist (Nepeta binaloudensis (leaf) with Trachyspermum ammi (fruit) and Nepeta binaloudensis (leaf) with Lavandula officinalis (flower) and antagonist (Pelargonium graveolens (leaf) with Lavandula officinalis (flower)), were observed significantly among the plants tested in this research. These interactions can be used to prepare more effective natural herbicides and decrease the use of herbicides. [ABSTRACT FROM AUTHOR]

Aflatoxins (AFs), a class of toxins produced by certain species of the genus Aspergillus, occasionally contaminate food and cause serious damage to human health and the economy. AFs contamination is a global problem, and there is a need to develop effective strategies to control aflatoxigenic fungi. In this study, we focused on isothiocyanates (ITCs) as potential chemical agents for the control of aflatoxigenic fungi. We quantitatively evaluated the effects of four ITCs (allyl ITC (AITC), benzyl ITC (BITC), and methyl and phenylethyl ITCs) in dissolved and gaseous states on the growth and aflatoxin B1 production of Aspergillus flavus. In experiments using dissolved ITCs, BITC was found to be the strongest inhibitor of growth and aflatoxin B1 production by A. flavus. Meanwhile, in the gaseous state, AITC strongly inhibited the A. flavus growth. When the concentration of ITCs in the liquid medium was quantified over time, AITC levels decreased to below the detection limit within 24 h, whereas BITC levels remained stable even after 48 h. These results suggested that when ITCs are utilized to control aflatoxigenic fungi, it is necessary to use them in a dissolved or gaseous state, depending on their volatility. [ABSTRACT FROM AUTHOR]

As one of the largest genera of the Lamiaceae family, Salvia has a wide distribution worldwide. Despite their great importance and medicinal use, most Salvia species are collected from their natural habitats, and some of them are endangered and vulnerable. This study aimed to evaluate the domestication process of eight Iranian native Salvia species. The studied species were cultivated and adapted to the cultivation area after two years, and then some of their important biochemical properties were investigated. According to some significant results, the root architecture was closely correlated with the climatic conditions of the species origins. The distribution of total dry matter varied widely among species; accordingly, S. sclarea and S. officinalis had 65.6% and 55.9% dry weights in their leaves, respectively. Moreover, S. nemorosa had a 24.3% dry weight in its flowers, while S. frigida (Jahrom), S. frigida (Targavar), S. virgata (Eghled), and S. macrosiphon had 44.6%, 43.3%, 46.0%, and 44.3% dry weights in their roots. The most potent antioxidant activity (IC50) was observed in the roots of S. macrosiphon (10.9 μg/mL) and S. sclarea (14.9 μg/mL), the stem of S. nemorosa (14.3 μg/mL), and the leaves of S. atropatana (14.0 μg/mL). Rosmarinic acid, a key phenolic substance in Salvia species, was present in the range of 0.24–0.47 mg/g dry weight. The essential oil content ranged from 0.35% in S. atropatana to 1.45% (w/w) in S. officinalis. β-caryophyllene, caryophyllene oxide, and germacrene D were the major ingredients of the essential oils. The cluster analysis based on the essential oil data revealed the most similarities between S. sclarea and S. macrosiphon, and a clear separation of S. virgate, S. syriaca, and S. officinalis from other species. Salvia spp. contain a wide variety of compounds of interest under cultivation, with S. sclarea having the greatest potential to profit from the production of medicinal compounds, such as phenolic compounds, flavonoids, and essential oils. Furthermore, S. officinalis, S. nemorosa, and S. sclarea are the best species for producing raw medicinal materials. [ABSTRACT FROM AUTHOR]

In a natural ecosystem, endophytic fungi in the internal tissues of plants help to improve the growth of the host plants and to decrease the negative effects of biotic and abiotic stresses without having adverse effects. In Japan, Vicia villosa (hairy vetch), a legume plant with a high capacity to fix nitrogen, is usually used as a cover crop before soybeans to enhance the fertility and structure of the soil. This study aimed to isolate endophytic fungi associated with different tissues of hairy vetch and to evaluate their potential for growth-promoting and biocontrol effects in plants. Thirty-three fungal endophytes belonging to Ascomycota and Basidiomycota were isolated from the leaf, stem, and root tissues of hairy vetch grown under both greenhouse and field conditions. The highest colonization frequency in both the greenhouse and field-grown hairy vetch plants was obtained from the root tissues. All isolates were checked for indole-3-acetic acid (IAA) and siderophore production. The maximum IAA content in the culture filtrate (4.21 μg mL−1) was produced by the isolate hvef7 (Cladosporium cladosporioides), followed by hvef18 (Penicillium simplicissimum) (3.02 μg mL−1) and hvef1 (Cladosporium pseudocladosporioides) (2.32 μg mL−1). Nineteen isolates among a total of thirty-three isolates produced siderophores. Moreover, some of the isolated strains could solubilize phosphate and potassium. Most of the isolates showed antagonistic potential against Calonectria ilicicola. The results of this study show that endophytic fungi isolated from hairy vetch have the potential for application as plant growth promotion fungi (PGPF) to promote plant growth and control disease in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Soil sickness syndrome in Japanese pear (Pyrus pyrifolia (Burm.f.) Nakai) affects the growth of the tree and decreases fruit yield. This study investigated the growth-inhibitory activity in Japanese pear (Pyrus pyrifolia (Burm.f.) Nakai) using the rhizosphere soil assay method to elucidate the characteristics of growth-inhibitory substances in Japanese pears. As a result, the root bark had the highest growth inhibitory activity during the growing season of the Japanese pear. For comparative analysis, the growth-inhibitory activities of Japanese apricots (Prunus mume Sieb. Et Zucc.) and figs (Ficus carica L.) were also investigated. Similar to the Japanese pear, the root bark of Japanese apricots and figs had a higher inhibition rate than the root pith. Like Japanese apricots and figs, it was inferred that the growth inhibitory substances accumulate in the bark of the Japanese pear. Furthermore, soil sickness syndrome in Japanese pear saplings did not occur when a fragment of Japanese pear shoots or thick roots was mixed with non-pear soil (soil with no history of Japanese pear cultivation). Based on these findings, it is considered that the condition of soil sickness in Japanese pear is caused by the accumulation of phenolic compounds such as arbutin, which is accumulated in the bark of the tree, secreted from the roots, and subsequently builds up in the soil. Additionally, the degree of occurrence of soil sickness syndrome depending on the rootstock was clarified. It was observed that the rate of growth inhibition was significantly higher in Pyrus betulifolia (Birchleaf pear) than in Pyrus pyrifolia (Japanese pear). Even when Japanese pear trees were planted in soils with no history of Japanese pear cultivation, the initial growth of P. betulifolia was 1.4 times that of P. pyrifolia. It is suggested that P. betulifolia is weak against soil sickness, but is excellent at initial growth itself. Our findings are important because P. pyrifolia is used for cultivation, in combination with other mitigation measures, such as soil dressing in replanted fields. [ABSTRACT FROM AUTHOR]

Rhazya stricta is an endangered medicinal plant that is under severe human pressure as a result of commercial harvesting. As a model of habitat fragmentation, we selected the Kohat Plateau in the Pakistani Himalaya, where populations are fragmented, with less than 100 individuals per population. We hypothesized that the populations may be threatened by rapid habitat fragmentation and by unsustainable utilization of the plant. We analysed P450-based analogue functional genomic markers and amplified fragment length polymorphism markers from six populations of R. stricta on the Kohat Plateau, and examined their variations both within and among the populations. Both the marker groups revealed lower genetic differentiation among the populations and higher genetic differentiation within the populations as a result of high gene flow. The results confirmed that habitat fragmentation is being caused by severe human pressure, and although signs of genetic erosion are not yet visible, they seem likely to become visible in the future. Therefore, the conservation of R. stricta populations is necessary. [ABSTRACT FROM PUBLISHER]

Buckwheat (Fagopyrum esculentum Moench) is an important annual plant cultivated for grain or as a cover crop in many countries, and it is also used for weed suppression in agro-economic systems through its release of allelochemicals. Little is known, however, concerning the mode of action of allelochemicals or plant defence response against them. Here, microarrays revealed 94, 85, and 28 genes with significantly higher expression after 6 h of exposure to the allelochemicals fagomine, gallic acid, and rutin, respectively, compared with controls. These induced genes fell into different functional categories, mainly: interaction with the environment; subcellular localization; protein with binding function or cofactor requirement; cell rescue; defence and virulence; and metabolism. Consistent with these results, plant response to allelochemicals was similar to that for pathogens (biotic stress) or herbicides (abiotic stress), which increase the concentration of reactive oxygen species (ROS; with consequent oxidative stress) in plant cells. The data indicate that allelochemicals might have relevant functions, at least in part, in the cross-talk between biotic and abiotic stress signalling because they generate ROS, which has been proposed as a key shared process between these two stress mechanisms. [ABSTRACT FROM PUBLISHER]

Structure–activity-relationships of quercetin and its seven derivatives were investigated using a shoot growth test with Arabidopsis thaliana seedlings and conidial germination test with Neurospora crassa. All the tested substances inhibited the shoot growth of A. thaliana. On the other hand, in conidial germination test of N. crassa, some flavonoids did not show any inhibitory activity. Quercetin 3-methyl ether and its glycosides especially showed the highest inhibitory effect among them in the conidial germination test of Neurospora. These results indicate that the presence of methyl group in flavonoid nucleus have some important roles as inhibiting effect to A. thaliana and N. crassa. [Copyright &y& Elsevier]

Laboratory and greenhouse experiments were conducted to evaluate the allelopathic potential of dwarf lily turf ( Ophiopogon japonicus Ker-Gawler) on lettuce, alfalfa, timothy and mustard plant growth. Dry leaf debris, aqueous extract of fresh leaves and O. japonicus grown soil were investigated. Emergence, dry weight, and root and shoot length of all bioassay species were inhibited when grown in soil incorporated with oven-dried leaves of O. japonicus. The inhibitory effects were often dependent on the concentration. However, the degree of inhibition varied among the test plant species. The aqueous leaf extract was highly phytotoxic and it significantly reduced germination, seedling growth, and the fresh weight of all the test species at all rates. The emergence and growth of all four tested plants were severely inhibited when planted in O. japonicus contaminated soil. These results indicate that O. japonicus incorporated leaf debris, leaf aqueous extract and its rhizosphere soil suppress seed germination, radicle growth, seedling emergence and seeding growth of certain weeds and suggest that these responses were attributed to an allelopathic effect. [ABSTRACT FROM AUTHOR]

To assist the development of new therapeutic strategies for several disorders, biologically active peptides/proteins obtained from plant sources can be considered. Current study expected to determine the biological activities of peptide fractions of Mucuna pruriens against hepatocellular carcinoma cell lines (HepG2/ADM, HepG2, SMMC‐7721, and QGY‐7703), as well as normal cell line to prove their selectivity. Moreover, anti‐genotoxicity and antiviral activity against the hepatitis C virus (HCV) were assessed. The methods of this study were to isolate the peptides of M. pruriens and hydrolysate fractionation via fractionated pepsin‐pancreatin hydrolysates by ultrafiltration/high‐performance ultrafiltration cell, identify anti‐hepatoma activity of peptide fractions human liver cancer and normal cells by (3‐(4,5‐dimethylthiazole‐2‐yl)‐2,5‐biphenyl tetrazolium bromide) (MTT) assay, determine anti‐HCV, and assess anti‐genotoxic effect of peptide fractions against damage that induced via alkylating agent methyl methanesulphonate in human mononuclear cells. The results showed that the fraction 5–10 kDa has been reported to exhibit significant cytotoxic activity against HepG2 and QGY‐7703. It was proven that both of 5–10 and >10 kDa fractions are active against HCV. The cytotoxic concentration (CC50) of 5–10 kDa against the cell line was 703.04 ± 5.21 µg/ml. Anti‐genotoxic activities of the peptide fractions were evaluated as mean values for the analyzed comet images. In this regard, the highest activity of protecting DNA damages was observed by the peptide fraction of 5–10 kDa. This study revealed the potential ability of peptide fractions of M. pruriens for the treatment of liver cancer, HCV, and high activities of protecting DNA damages. [ABSTRACT FROM AUTHOR]

The plant root-associated environments such as the rhizosphere, rhizoplane, and endosphere are different from the outer soil region (bulk soil). They establish characteristic conditions including microbiota, metabolites, and minerals, and they can directly affect plant growth and development. However, comprehensive insights into those characteristic environments, especially the rhizosphere, and molecular mechanisms of their formation are not well understood. In the present study, we investigated the spatiotemporal dynamics of the root-associated environment in actual field conditions by multi-omics analyses (mineral, microbiome, and transcriptome) of soybean plants. Mineral and microbiome analyses demonstrated a characteristic rhizosphere environment in which most of the minerals were highly accumulated and bacterial communities were distinct from those in the bulk soil. Mantel's test and co-abundance network analysis revealed that characteristic community structures and dominant bacterial taxa in the rhizosphere significantly interact with mineral contents in the rhizosphere, but not in the bulk soil. Our field multi-omics analysis suggests a rhizosphere-specific close association between the microbiota and mineral environment. [ABSTRACT FROM AUTHOR]

Isophorone (3,5,5‐trimethylcyclohex‐2‐en‐1‐one) is a plant‐derived volatile compound with strong phytotoxic activity. Here, we aimed to elucidate the mechanism of action of isophorone, and to this end, the effects of isophorone on shoot fresh weight, chlorophyll content, electrolyte leakage, and lipid peroxidation of Lactuca sativa L. and photosynthetic electron transport activity in chloroplast isolated from Spinacia oleracea L. were investigated. Isophorone induced light‐independent decreases in shoot fresh weight and light‐dependent chlorosis. In addition, increased electrolyte leakage and lipid peroxidation occurred under light conditions. However, the inhibitory activity on photosynthetic electron transport was unexpectedly low, and electrolyte leakage and lipid peroxidation were induced even under dark conditions. These results suggest that the inhibition of photosynthetic electron transport is not the main mechanism of action of isophorone and that the phytotoxic effects are mainly due to light‐independent oxidative damage and subsequent loss of cell membrane integrity. [ABSTRACT FROM AUTHOR]

Medicinal and aromatic plants have the ability to transmit volatile allelochemicals and affect their surrounding organisms. In this regard, their interaction should also be considered. The inhibitory effects of 112 essential oils on lettuce seed and seedling were investigated by cotton swab method. Germination (G%), Mean germination time (MGT), Lethal of embryo (L%), dormancy (D%), radicle growth (R%), and hypocotyl growth (H%) were measured. Two methods were used for evaluating allelopathic interaction effects: the simplified modified dilution check-board technique (SMCT) and the isobologram. Thymus daenensis had the highest inhibitory effect on G% (IC50 = 2.9 ppm) and the most lethal effect on the embryo (LC50 = 7.2 ppm). Thymus transcaspicus, Dracocephalum moldavica, Artemisia sieberi and Amomum subulatum had the greatest effect on MGT. Ziziphora tenuior, Trachyspermum ammi and Pelargonium graveolens had the highest effect on D%. Origanum vulgare was the strongest growth inhibitor. The highest synergistic effect on G% was in A. subulatum + Mentha suaveolens, on H% was related to Perovskia abrotanoides + T. daenensis, and on R% was observed in Artemisia vulgaris + M. suaveolens. The results of this study can lead to identification of new phytotoxic compounds in EOs and control weeds more effectively. [ABSTRACT FROM AUTHOR]

Strong allelopathic activities of etiolated seedlings of a leguminous plant, Vicia villosa Roth (hairy vetch), were confirmed by a protoplast co-culture method. The combination of 1% Cellulase RS and 1% Driselase 20 in 0.4 M mannitol solution was used for protoplast isolation. The inhibitory effects of V. villosa protoplasts on the growth of recipient Lactuca sativa L. (lettuce) protoplasts were determined using 96-well culture plates with 50 μL of liquid medium consisting of Murashige and Skoog's basal medium containing 1 μM 2,4-dichlorophenoxyacetic acid, 0.1 μM 6-benzyladenine, 3% (w/v) sucrose, and 0.4 M mannitol in each well. The allelopathic activity of V. villosa epicotyl protoplasts (2 × 102 to 105 mL−1), on cell division of lettuce protoplasts (6 × 103 to 5 × 104 mL−1), was stronger than that of roots and was stronger than on cell wall formation. Digital image analysis of co-cultured protoplasts (DIA-PP method) showed the effect of V. villosa protoplasts on the accumulation of a yellow color in lettuce protoplasts. Weaker inhibition was seen than at the cell wall formation and cell division stages. Effects of putative allelochemical, canavanine at 10 μM strongly inhibited division of lettuce protoplasts, whereas putative allelochemical, cyanamide was stimulatory at 10 μM, but inhibitory at 1 mM. A high level of canavanine was found in epicotyl protoplasts using gas chromatography-mass spectrometry. Canavanine was suggested to be the allelochemical in V. villosa epicotyl protoplasts of etiolated seedlings, although its effect differed with the growth stages of lettuce protoplasts. [ABSTRACT FROM AUTHOR]

A bioassay method for allelopathy, the 'protoplast co-culture method' was developed to study the relationship between salt tolerance and allelopathy of three mangrove species, Sonneratia alba, S. caseolaris, and S. ovata. Plants of S. alba grow in the seaward-side high salinity region and plants of the latter two species grow in upstream-side regions of a mangrove forest, respectively. Effects of five sea salts (NaCl, KCl, MgCl, MgSO and CaCl) on the growth of the suspension cells of the latter two species were first investigated by a small-scale method using 24-well culture plates. S. ovata cells showed higher tolerance than S. caseolaris cells to NaCl and other salts, but were not as halophilic as S. alba cells. Protoplasts isolated from suspension cells were co-cultured with lettuce protoplasts in Murashige and Skoog's (MS) basal medium containing 1 μM 2,4-dichlorophenoxyacetic acid, 0.1 μM benzyladenine, 3 % sucrose and 0.6-0.8 M osmoticum. S. caseolaris protoplasts had a higher inhibitory effect on lettuce protoplast cell divisions than S. alba protoplasts at any lettuce protoplast density, and the effect of S. ovata was intermediate between the two. These results were similar to those obtained from a different in vitro bioassay method for allelopathy, the 'sandwich method' with dried leaves. The inverse relationship between allelopathic activity and salt tolerance in suspension cells of Sonneratia mangroves is discussed. [ABSTRACT FROM AUTHOR]

Tamarindus indicaL. is well known for its acidic nature and allelopathic potential, but to date, little is known about its organic acids playing their role as allelochemicals. Hence, in the present study, identification, quantification, and contribution of organic acids present in its leaf extract were conducted using the principle of bioassay-guided procedure. High pressure liquid chromatography identified four organic acids, viz. citric, malic, oxalic, and tartaric acids, in its leaf aqueous extract with the predominance of oxalic acid (7.5 g kg−1leaves fresh weight) followed by tartaric acid (7.3 g kg−1). The allelopathic activity of identified acids and aqueous extract was evaluated on lettuce seedlings growth based on the specific activity (EC50). The crude extract reduced radicle growth more adversely than hypocotyl at the concentration of 2.5 g L−1(EC50). It hindered the normal physiological growth process through weak and curly seedlings, and necrosis of their tips. Among the identified acids, oxalic acid had the highest specific activity (40 mg L−1) and citric acid had the lowest (>1000 mg L−1). As a consequence of its high contents, the total activity, a function of specific activity and concentration, of oxalic acid (188) was found higher followed by tartaric acid (146). The contribution of both acids influencing the specific activity of the crude extract was then turned out to be 74%. To the best of our knowledge, this is the first report identifying the oxalic and tartaric acids as growth inhibitors in tamarind leaves and quantifying their contribution in its allelopathic expression. Based on the total activity, the results suggested that oxalic and tartaric acids are the major allelochemicals in tamarind leaves. The allelopathic potential of these acids might promote the development of natural herbicides as an alternative to the synthetic ones in a most sustainable manner. [ABSTRACT FROM AUTHOR]

Abstract: The grass Brachiaria brizantha, native to eastern Africa, becomes naturalized and dominant quickly in the non-native areas. It was hypothesized that phytotoxic chemical interaction between this plant and native plants may play an important role in the invasion of B. brizantha. However, no potent phytotoxic substance has been reported in this species. Therefore, we investigated possible allelopathic activity and searched for phytotoxic substances with allelopathic activity in B. brizantha. An aqueous methanol extract of B. brizantha inhibited the growth of roots and shoots of garden cress (Lepidium sativum), lettuce (Lactuca sativa), timothy (Phleum pratense) and ryegrass (Lolium multiflorum) seedlings. The extract was purified by several chromatographic runs and three allelopathically active substances were isolated and identified by spectral analysis as (6R,9R)-3-oxo-α-ionol, (6R,9S)-3-oxo-α-ionol and 4-ketopinoresinol. (6R,9R)-3-Oxo-α-ionol and (6R,9S)-3-oxo-α-ionol inhibited root and shoot growth of garden cress at concentrations greater than 30 and 10μM, respectively. The activity of (6R,9S)-3-oxo-α-ionol was 5.3- to 6.2-fold that of (6R,9R)-3-oxo-α-ionol. The stereochemistry of the hydroxyl group at position C-9 may be important for the inhibitory activities of those compounds. 4-Ketopinoresinol inhibited root and shoot growth of garden cress at concentrations greater than 30μM. The growth inhibitory activity of (6R,9S)-3-oxo-α-ionol was the greatest and followed by 4-ketopinoresinol and (6R,9R)-3-oxo-α-ionol. These results suggest that those phytotoxic substances may contribute to the allelopathic effect caused by B. brizantha and may be involved in the invasion of B. brizantha. [Copyright &y& Elsevier]

To establish a rapid high-throughput evaluation system for the enhanced plant growth-inhibitory activity caused by modifications of cis-cinnamic acid's (cis-CA's) chemical structure, a DNA microarray assay was used to analyze the changes in early gene responses of Arabidopsis thaliana seedlings. After a 6-hr exposure to (Z)-3-(3-iodophenyl)acrylic acid, we observed an upregulation in three classes of early auxin-responsive genes, which was similar to the transcriptional response to indole-3-acetic acid (IAA), together with an upregulation of the genes related to environmental stress and toxin detoxification responses. Gene responses to 2-(3,4-dihydronaphthalen-1-yl)acetic acid were similar to those to IAA. In contrast, fewer genes were upregulated in response to its double-bond isomer, (Z)-2-[3,4-dihydronaphthalen-1(2H)-ylidene]acetic acid, than to cis-CA. DNA microarray data suggest that the structurally different cis-CA analogues trigger diverse gene responses. [ABSTRACT FROM AUTHOR]

Highlights: [•] Conformationally constrained cis-cinnamic acid analogues were designed, in which the aromatic ring and the cis-olefin are connected by a carbon bridge. [•] Their inhibitory activities on elongation of lettuce roots was evaluated with inhibitory activities of five- and six-membered bridged compounds being enhanced. [•] The cis-analogue having a five-membered ring exhibited bioactivity ten times higher than cis-cinnamic acid. [Copyright &y& Elsevier]

Highlights: [•] cis-Cinnamic acid analogues was synthesized having substituents on the aromatic ring, and their inhibitory activities on the elongation of lettuce roots were evaluated. [•] Para- and ortho-substitution decreased potency. [•] meta-Substituted cis-cinnamic acid analogues were more likely to be potent. [•] m-Iodo, m-methoxy and m-trifluoromethyl substituents induced higher potency. [Copyright &y& Elsevier]

Abstract: 1-O-cis-cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals isolated from Spiraea thunbergii Sieb. It is suggested that it derives its strong inhibitory activity from cis-cinnamic acid, which is crucial for phytotoxicity. It was synthesized to confirm its structure and bioactivity, and also a series of cis-cinnamic acid analogues were prepared to elucidate the key features of cis-cinnamic acid for lettuce root growth inhibition. The cis-cyclopropyl analogue showed potent inhibitory activity while the saturated and alkyne analogues proved to be inactive, demonstrating the importance of the cis-double bond. Moreover, the aromatic ring could not be replaced with a saturated ring. However, the 1,3-dienylcyclohexene analogue showed strong activity. These results suggest that the geometry of the C–C double bond between the carboxyl group and the aromatic ring is essential for potent inhibitory activity. In addition, using several light sources, the photostability of the cinnamic acid derivatives and the role of the C–C double bond were also investigated. [Copyright &y& Elsevier]

Peru is one of the 20 botanically extremely diverse countries in the world, with >17 000 flowering plants, of which 30% are endemic. So far, no systematic research has been conducted on the screening of the allelopathic plants. In this study, the allelopathic activity of 170 species from 61 families of Peruvian plants that were collected from the three main regions of Peru - the Costa (Pacific coastline), the Sierra (Andean mountains), and the Selva (Amazonian rainforest) - was evaluated. The allelopathic activity was determined by the Sandwich Method, which can evaluate the activity of leaf leachates. The species that were found to be highly inhibitory in this screening, under the criterion of >90% inhibition of the radicle of lettuce ( Lactuca sativa) seedlings, were Aristeguietia ballii and Diplostephium foliosissimum (Asteraceae) and Spondias mombin (Anacardiaceae). All of these species are native plants from Peru. This study gives a strong clue regarding the potential of isolating potent allelochemicals from these plants in the future. [ABSTRACT FROM AUTHOR]

The methanol extract of Bletilla striata, an ornamental orchid in eastern Asia, exhibited plant growth-inhibitory activity. It was purified by continuous chromatography, based on the inhibitory activity against the growth of lettuce seedlings, resulting in two glycosidic compounds, militarine and dactylorhin A. The EC50 values of militarine and dactylorhin A against the radicle elongation of the lettuce seedlings were 0.28 and 0.88 mmol L−1, respectively. The amount of militarine and dactylorhin A in the methanol extract of the aerial part of B. striata was calculated to be 5.6 and 7.5 mg g−1 fresh weight, respectively. The inhibitory activity of militarine and its content in the methanol extract revealed that the plant growth-inhibitory activity of the extract of B. striata was mainly related to militarine. The inhibitory activity of militarine against the growth of Italian ryegrass and timothy were of the same level as that of lettuce. [ABSTRACT FROM AUTHOR]

We isolated an antimicrobial compound from the aerial tissue of Geranium carolinianum and identified it as ethyl 3, 4, 5-trihydroxy benzoate (ethyl gallate) by 1H-NMR and 13C-NMR and gas chromatography–mass spectrometry. The antimicrobial activity of ethyl gallate against three potato pathogens was assayed by the paper disk method. The activity against Ralstonia solanacerum, Streptomyces scabies, and Streptomyces acidiscabies was observed at concentrations >200, >300, and >300 µg disk−1, respectively. These results suggest that the antimicrobial activity of Geranium carolinianum against soil-borne plant disease pathogens is partly related to ethyl gallate. [ABSTRACT FROM AUTHOR]

The continuous planting of Japanese pear leads to a soil sickness syndrome that eventually affects the growth and yield of the plant. In this study, we aimed to elucidate the characteristics of soil sickness syndrome in the Japanese pear and construct countermeasures using the rhizosphere soil assay method that can quantify the risk of soil sickness syndrome by inhibitory chemicals. Water flushing treatment, rainfall treatment, and the incorporation of test soils with different rates of activated carbon were evaluated on the risks of soil sickness. The water flushing treatment under laboratory conditions and exposure of the continuous cropping soil to rainfall in the open field decreased the inhibition rate of the soil. The decrease in soil inhibition rate was presumed to be the result of accumulated growth inhibitory substances in the soil being washed away by water. In addition, activated carbon with the potential to reduce the soil sickness syndrome was selected using the rhizosphere soil assay method. It was clarified that the mixing of the selected activated carbon with the continuous cropping soil reduced the inhibition rate and increased the growth of pear trees increased compared to the untreated soil from the continuous cropping field. The inhibition rate of the soil from the continuous cropping field was reduced to the level of soil with no history of Japanese pear cultivation. In the replanted field, these treatments can promote the growth of trees by reducing the influence of soil sickness syndrome. [ABSTRACT FROM AUTHOR]

Abstract: Cyanamide (NH2CN) has recently been proven to be a natural product, although it has been synthesized for over 100 years for agricultural and industrial purposes. The distribution of natural cyanamide appears to be limited, as indicated by our previous investigation of 101 weed species. In the present study, to investigate the distribution of natural cyanamide in Vicia species, we monitored the cyanamide contents in V. villosa subsp. varia, V. cracca, and V. amoena during their pre-flowering and flowering seasons. It was confirmed that V. cracca was superior to V. villosa subsp. varia in accumulating natural cyanamide, and that V. amoena was unable to biosynthesize this compound under laboratory condition examined. The localization of cyanamide in the leaves of V. villosa subsp. varia seedlings was also clarified. In a screening study to find cyanamide-biosynthesizing plants, only Robinia pseudo-acacia was found to contain cyanamide among 452 species of higher plants. We have investigated 553 species to date, but have so far found the ability to biosynthesize cyanamide in only three species, V. villosa subsp. varia, V. cracca and R. pseudo-acacia. [Copyright &y& Elsevier]

The various organs of the Polish cultivars of buckwheat were evaluated for their flavonoid content (rutin, quercetin, (+)-catechin, and (−)-epicatechin) and for their phenolic acid content (chlorogenic, caffeic, ferulic, and gallic acids) to test their contribution to buckwheat allelopathic activity. The main compound found in the above-ground organs of buckwheat was rutin, followed by chlorogenic acid, and then (−)-epicatechin. The allelopathic activity, based on the specific activity of the identified compounds on lettuce seedling growth, was evaluated. Gallic acid had the highest specific activity and quercetin had the lowest. The specific activity of rutin was at the medium level compared to the other examined compounds, but as a consequence of its high concentration, its total activity was very high. The growth inhibitory effects of the aqueous extracts of the buckwheat leaves and inflorescences were higher than that of the stems. The higher inhibitory activity of the extracts compared to the leaves and inflorescences was explained by the high presence of rutin in them. Therefore, based on the total activity, as calculated by its concentration and its growth inhibitory effect, it seems that rutin, among the other tested compounds, is the major allelochemical in Polish buckwheat. [ABSTRACT FROM AUTHOR]

Lycoris radiata Herb., a common medicinal plant of Far East Asia, was examined for its potential use in paddy weed control. The preliminary screening in greenhouse conditions indicated growth inhibitory activities. The emergence, root and shoot growth, and root dry weight of the bioassay species were reduced when grown in soil mixed with the leaves of L. radiata. Aqueous extracts of the fresh leaves at various concentrations inhibited the root and shoot growth of all tested plant species. To identify the active components, L. radiata ethanolic extract was subjected to bioassay-guided fractionation, purification, and spectroscopic analysis. This process led to the isolation of lycorine as a potential allelochemical. The concentration of lycorine in the dry leaves of L. radiata is estimated to be 0.08%. It is possible that lycorine is exuded from the roots or leaches from the living or decomposing leaves, along with other numerous inhibitors, and inhibits the growth of neighboring or successional plants. These results suggest that L. radiata has the potential to inhibit plant growth and lycorine acts as one of the most important plant growth inhibitors. This plant can be grown as a ground cover plant and its dead leaves could be applied as cover mulch. [ABSTRACT FROM AUTHOR]

Abstract: Cyanamide is a multifunctional agrochemical used, for example, as a pesticide, herbicide, and fertilizer. Recent research has revealed that cyanamide is a natural product biosynthesized in a leguminous plant, hairy vetch (Vicia villosa). In the present study, gas chromatography–mass spectrometry (GC–MS) equipped with a capillary column for amines was used for direct quantitative determination of cyanamide. Quantitative signals for (14N2)cyanamide, (15N2)cyanamide (internal standard for stable isotope dilution method), and m-(trifluoromethyl)benzonitrile (internal standard for correcting errors in GC–MS analysis) were recorded as peak areas on mass chromatograms at m/z 42 (A 42), 44 (A 44), and 171 (A IS), respectively. Total cyanamide content, (14N2)cyanamide plus (15N2)cyanamide, was determined as a function of (A 42 + A 44)/A IS. Contents of (14N2)cyanamide and (15N2)cyanamide were then calculated by multiplying the total cyanamide content by A 42/(A 42 + A 44) and A 44/(A 42 + A 44), respectively. The limit of detection for the total cyanamide content by the GC–MS analysis was around 1ng. The molar ratio of (14N2)cyanamide to (15N2)cyanamide in the injected sample was equal to the observed A 42/A 44 value in the range from 0.1 to 5. It was, therefore, possible to use the stable isotope dilution method to quantify the natural cyanamide content in samples; i.e., the natural cyanamide content was derived by subtracting the A 42/A 44 ratio of the internal standard from the A 42/A 44 ratio of sample spiked with internal standard, and then multiplying the resulting difference by the amount of added (15N2)cyanamide (SID-GC–MS method). This method successfully gave a reasonable value for the natural cyanamide content in hairy vetch, concurring with the value obtained by a conventional method in which cyanamide was derivatized to a photometrically active compound 4-cyanimido-1,2-naphthoquinone and analyzed with reversed-phase HPLC (CNQ-HPLC method). The determination range of cyanamide in the SID-GC–MS method was almost the same as that in the CNQ-HPLC method; however, the SID-GC–MS method was much simpler than the CNQ-HPLC method. [Copyright &y& Elsevier]

Laboratory and field experiments were conducted to evaluate the usefulness of Oxalis spp. as allelopathic ground-cover plants for weed management. Some Oxalis spp. have previously been reported to possess strong allelopathic activities but few studies have been conducted on their activities in fields. This study aimed to investigate allelopathic activities and the possibility of weed suppression in five species of common Oxalis: shamrock oxalis ( Oxalis articulata Savigny), Bowie's woodsorrel ( Oxalis bowiei Lindl.), trefoil ( Oxalis brasiliensis Lodd. ex Knowl. et West.), lucky clover ( Oxalis deppei Lodd. ex Sweet) and Oxalis hirta L. The effects of the leachates from dry leaves and the exudates from living roots of these plant species were tested in laboratory experiments. The leachates from O. articulata, O. bowiei, O. deppei and O. hirta and the exudates from O. deppei caused > 84% inhibition of the radicle elongation of lettuce seedlings, but no effect was observed on the seed germination of lettuce. In the field experiment, O. deppei significantly reduced the weed population in July. A significant relationship was observed between the weed population and the percentage ground coverage of Oxalis spp. In contrast to the weed population, a significant relationship was observed between the weed above-ground biomass and the allelopathic activity of exudates from Oxalis spp. [ABSTRACT FROM AUTHOR]

Spiraea thunbergii Sieb. was found to contain 1-O-cis-cinnamoyl-β-d-glucopyranose and 6-O-(4′-hydroxy-2′-methylene-butyroyl)-1-O-cis-cinnamoyl-β-d-glucopyranose as major plant growth inhibitory constituents along with related compounds of lower phytotoxicity including 6-O-(trans-cinnamoyl)-1-O-(4″-hydroxy-3″-methyl-furan-2″-one)-β-d-glucopyranose, 6-O-(4′-hydroxy-2′-methylene-butyroyl)-1-O-trans-cinnamoyl-β-d-glucopyranose, and 1-O-trans-cinnamoyl-β-d-glucopyranose. The former three compounds were cinnamoyl glucosides. [Copyright &y& Elsevier]

Plant growth inhibitory alkaloids were isolated from the extract of mesquite [Prosopis juliflora (Sw.) DC.] leaves. Their chemical structures were established by ESI-MS, 1H and 13C NMR spectra analysis. The I50 value (concentration required for 50% inhibition of control) for root growth of cress (Lepidium sativum L.) seedlings was 400 μM for 3⁗-oxo-juliprosopine, 500 μM for secojuliprosopinal, and 100 μM for a (1:1) mixture of 3-oxo-juliprosine and 3′-oxo-juliprosine, respectively. On the other hand, the minimum concentration exhibiting inhibitory effect on shoot growth of cress seedlings was 10 μM for 3⁗-oxo-juliprosopine, 100 μM for secojuliprosopinal, and 1 μM for a (1:1) mixture of 3-oxo-juliprosine and 3′-oxo-juliprosine, respectively. Among these compounds, a (1:1) mixture of 3-oxo-juliprosine and 3′-oxo-juliprosine exhibited the strongest inhibitory effect on the growth of cress seedlings. [Copyright &y& Elsevier]

Cladosporium species are active in protecting plants against different biotic and abiotic stresses. Since these species produced a wide range of secondary metabolites responsible for the adaptation to new habitats, plant health and performance, they are of great interest, especially for biostimulants in agriculture. Cladosporium sp. produces protein hydrolysates (PHs), a class of biostimulants, by cultivation on medium with keratin wastes (feathers) as carbon and energy sources. The aim of this study was to select a Cladosporium isolate with potential to be used as plant growth promoting agent. The characteristics of Cladosporium isolates as plants biostimulants were evaluated through several tests, such as: antagonism versus plants pathogens, effect on plant growth of secreted volatiles produced by isolates, secretion of hydrolytic enzymes, production of 3-indole acetic acid, zinc and phosphorous solubilization, capacity to promote tomato seedlings growth (pot experiments). Cladosporium isolate T2 presented positive results to all tests. Encouraging results were obtained treating tomato seedlings with PHs from isolate Cladosporium T2 cultured on medium supplemented with 1% (w/w) chicken feathers, for which growth parameters, such as stem weight, stem height, and root weight were significantly higher by 65%, 32%, and 55%, respectively, compared to those treated with water. [ABSTRACT FROM AUTHOR]

Previously, we found (2Z,4E)-5-phenylpenta-2,4-dienoic acid (ku-76) to be a selective inhibitor of root gravitropic bending of lettuce radicles at 5 μM, with no concomitant growth inhibition, and revealed the structure–activity relationship in this inhibitory activity. The conformation of ku-76 is flexible owing to the open-chain structure of pentan-2,4-dienoic acid with freely rotating single bonds, and the (2 Z) - alkene moiety may be isomerized by external factors. To develop more potent inhibitors and obtain insight into the target biomolecules, various analogues of ku-76 , fixed through conformation and/or configuration, were synthesized and evaluated. Stereochemical fixation was effective in improving the potency of gravitropic bending inhibition. Finally, we found highly potent conformational and/or configurational analogues (ku - 257, ku-294 and ku - 308), that did not inhibit root growth. The inhibition of root curvature by these analogues was comparable to that of naptalam. Image 1 • Design and chemical synthesis of root gravitropism inhibitors bridged analogues of ku-76 have more potent activity. • Highly potent analogues (ku-257 and ku-308) were found. • These analogues showed gravitropic bending inhibition in lettuce roots and did not exhibit concomitant growth inhibition. • The inhibitory activity of the potent analogues was comparable to that of NPA. [ABSTRACT FROM AUTHOR]

Weed management is an important issue since weeds directly compete with crop plants for space, nutrients; serve as habitat for insect pests and diseases, and can create a significant annual reduction in crop productivity. This study focused on evaluating the contribution of the secondary metabolites of the fruit pulp of Couroupita guianensis Aubl. for its potential growth inhibitory effect. Crude extracts of C. guianensis fruit pulp were collected with different solvents and applied to test plants in petri dishes. The crude extracts of methanol and 1% dimethyl sulfoxide (DMSO) showed potential growth inhibitions with the 50% effective concentration (EC50) of 223 and 229 µg/mL in the bioassay experiment. In the greenhouse pot experiment, soil incorporated with oven-dried fruit pulp of C. guianensis was evaluated on cultivated plant species including Lactuca sativa L., Trifolium repens L., Medicago sativa L., Lolium multiflorum Lam., and Phleum pratense L. The incorporation of dried fruit pulp of C. guianensis into soil reduced shoot and root lengths and the germination percentage of test plants. It was observed that the monocot plants were more affected than the dicot plants. The fruit pulp of C. guianensis was subjected to reversed-phase high-performance liquid chromatography (HPLC) analysis to identify the active compounds. Indigo, identified as one of the candidate compounds of the C. guianensis, had high specific activity (i.e., strong inhibitory activity) in a phytotoxicity bioassay and could explain through the total activity concept the growth inhibitory effect of the C. guianensis on test plants. The results suggested that indigo has plant growth inhibitory effect, indicating the allelopathic potential of C. guianensis, which could be exploited in sustainable weed management. [ABSTRACT FROM AUTHOR]

The article presents a simple analytical method for the quantification of cyanamide in plants. It further analyzes the cyanamide contents of the leaves, stems, cotyledons and roots of young seedlings of V. villosa and of the leaves of other Vicia species, Lens culinaris and Robinia pseudoacacia. It reports three advantages of this method over traditional ones which include requirement of less plant material, stable mass chromatogram and reduced risk of enzymatic activity.

Previously, we found (2 Z, 4 E)-5-phenylpenta-2,4-dienoic acid (ku-76) to be a selective inhibitor of root gravitropic bending of lettuce radicles at 5 μM, with no concomitant growth inhibition. Here, we describe a structure-activity relationship study of ku-76 to determine the essential structural features for the inhibitory activity. A series of ku-76 analogues was synthesized and the key features of ku-76 that are necessary for inhibition of lettuce root gravitropic bending were determined. The (2 E, 4 E)-, (2 Z, 4 Z)- (2 E, 4 Z)- analogues were inactive, and 4,5-saturated and 4,5-alkynyl analogues also did not show inhibitory activity, demonstrating the importance of the (2 Z, 4 E) diene unit. The aromatic ring was also crucial and could not be replaced with an alkyl chain. Derivatives in which the carboxylic acid was replaced with amides, alcohols, or esters were much less potent. These results suggest that the (2 Z ,4 E)-diene, the carboxylic acid moiety, and the aromatic ring are essential for potent inhibitory activity against gravitropic bending. Image 1 • ► Ku-76 showed inhibitory activity of gravitropic bending in lettuce roots at 5 μM. • Ku-76 did not exhibit concomitant growth inhibition. • ►A series of ku-76 analogues was synthesized. • ►The (2 Z, 4 E) -configuration, the carboxylate and the benzene ring are essential. [ABSTRACT FROM AUTHOR]

Understanding the community composition and diversity of arbuscular mycorrhizal fungi (AMF) in an agricultural ecosystem is important for exploiting their potential in sustainable crop production. In this study, we described the genetic diversity and community structure of indigenous AMF in rain-fed rice cultivars across six different regions in Ghana. The morphological and molecular analyses revealed a total of 15 different AMF genera isolated from rice roots. Rhizophagus and Glomus were observed to be predominant in all regions except the Ashanti region, which was dominated by the genera Scutellospora and Acaulospora. A comparison of AMF diversity among the agroecological zones revealed that Guinea Savannah had the highest diversity. Permutational Multivariate Analysis of Variance (PERMANOVA) analysis indicated that the available phosphorus (AP) in the soil was the principal determining factor for shaping the AMF community structure (p < 0.05). We report, for the first time, AMF diversity and community structure in rice roots and how communities are affected by the chemical properties of soil from different locations in Ghana. [ABSTRACT FROM AUTHOR]

This study focuses on identifying volatile emissions from plants with potential plant growth inhibitory activity. The aim of this study was to evaluate plant species from the Asian country Bangladesh for new, potential volatile allelopathic species. A total of 103 plant samples from 40 different families were assessed with the dish pack (DP) method. About 25% of the evaluated plant samples influenced (inhibited or stimulated) the growth of lettuce, due to the presence of potentially volatile allelochemicals. The pericarp of Sapindus mukorossi Gaertn. caused the lowest radicle elongation (3% of control) of the lettuce. This was followed by the leaves of Cassia nodosa Roxb. (34.4%) and the root of Kaempferia galangal L. (43.4%), in that order. Therefore, the pericarp of S. mukorossi is reported from this study as a new potential volatile allelopathic species. On the contrary, the leaves of Gynostemma pentaphyllum Thunb. had a stimulatory effect on the hypocotyl elongation of lettuce seedlings (156% of control). The single petri dish (SPD), a new method, was also adapted to justify the potentiality of the growth control of particular allelopathic species. This study revealed that the new potentially volatile allelopathic plant species could be further explored in sustainable weed management. [ABSTRACT FROM AUTHOR]

The article presents a study which investigated the distribution of cyanamide in the plant kingdom using a direct quantitative determination method to detect and measure cyanamide by stable isotope dilution gas chromatography-mass spectrometry. The method proved to be a robust way to quantify cyanamide contents in the extracts of 101 species of herbaceous plants.

The present study aimed to examine the phytotoxic potential of seven Vietnamese tea samples based on the specific and total activity of caffeine and tea extracts on test plants. The sandwich method results indicated that the inhibitory effect of tea samples on the radicle and hypocotyl growth of lettuce seedlings was dependent on the concentration and type of tea samples, and also the presence of agar soluble allelochemicals. Among the seven tea samples, the leachates from Vinatea-green tea showed the highest inhibition on the radicle growth of lettuce seedlings with 50% suppression at 0.12 mg dry leaves/mL of agar. Caffeine concentration in tea samples analyzed by high-performance liquid chromatography (HPLC) varied from 20.7 to 38.2 µg/mL of dry leaves. The specific activity (EC50 value) of pure caffeine was 75 µg/mL, and the highest total activity of caffeine estimated in Vinatea-green tea was 0.51 [no unit]. Caffeine from green and oolong tea may be considered as one of the contributors to the inhibitory activity of the crude extract. Moreover, the phytotoxicity of pure caffeine and aqueous tea extracts was highly selective on the growth of different plant species. The concentration of caffeine detected from tea farm soil ranged from 0.137 to 0.145 µg/g soil. The results indicated that caffeine might be considered as a promising allelochemical from Vietnamese tea and can be a good candidate for weed management. [ABSTRACT FROM AUTHOR]