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1.
Non-destructive acetylene reduction assays were successfully performed using small (1.21) incubation chambers and a 1 h incubation at 20°C. The concentration of C2H2 substrate used in the assays reached saturation at a partial pressure of 10 kPa for nodulated subterranean clover and barrel medic grown in a sandy loam. The optimum rates of C2H2 reduction associated with both species occurred within the range of 25–50% of the soil moisture content at field capacity (33 kPa). The ratio of moles N2 fixed to moles C2H2 reduced was calculated to be 1:2.9 for the subterranean clover—Rhizobium symbiosis and 1:3.3 for the barrel medic—Rhizobium symbiosis.  相似文献   

2.
Abstract

Experiments were conducted over 2 years during the dry season of 2002 (June–September) and wet season of 2002–2003 (December–March) at Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India, to study the influence of two colors of polyethylene film mulch (black and white polyethylene film mulch), herbicides (Fluchloralin at 1.0 kg/ha and no herbicide application), and three plant geometries [30×10 cm, 20×20 cm (two seeds/hill), and 20×15 cm] on soil properties, growth, and yield of groundnut. Results indicated that the soil physical properties such as rate of water loss/day was highest with white polyethylene film mulch, the hydraulic conductivity of the soil was significantly more with black polyethylene film mulch, and soil bulk density and percentage of pore space did not differ between the two colors of polyethylene films. The rate of water loss was highest with plots with no herbicide, whereas the hydraulic conductivity of the soil was more with herbicide‐applied treatments. However, the bulk density and pore space did not differ significantly. The plant geometry did not have any significant influence on any of the soil physical properties. With regard to soil microorganisms, the bacterial and fungal population was significantly higher in black polyethylene film mulch at all the three stages of observation, whereas no significant difference between the colors of polyethylene film mulch was observed for actinomycetes at all the stages of observations. Interestingly, no variation in the population of soil microflora was observed between the herbicide and no‐herbicide treatments. The soil‐available nitrogen, phosphorus, and potassium (NPK), at harvest, was significantly higher with white polyethylene film mulch, whereas crop NPK uptake was higher with black polyethylene film mulch. The soil‐available NPK and crop uptake was higher with herbicide application. The evolution of carbon dioxide (CO2; soil respiration) was significantly influenced by polyethylene film mulch and herbicides, and the evolution of CO2 was altered by the plant geometry. The crop dry‐matter production, pegging percentage, pod setting ratio number of matured pods/plant, and pod yield were significantly higher under black polyethylene mulch. Herbicide application significantly improved the majority of the growth and yield attributes and significantly higher pod yield was obtained with herbicide application. However, most of the yield and growth attributes and pod yield were not significantly influenced by the different plant geometries studied.  相似文献   

3.
Nodulation and nitrogen fixation of black locust (Robinia pseudoacacia L.), a legume tree broadly used in Argentina for urban and agricultural afforestation, was studied in hydroponic culture. The development of seedlings inoculated with a local strain of Rhizobium, highly specific for R. pseudoacacia, was also compared with respect to non-inoculated but N-fertilised seedlings. This strain produced fast nodulation and high crop yield and leaf N content. Already nodulated plants with the local Rhizobium strain were assayed for growth in a greenhouse pot experiment with soil from a field where topsoil has been removed for industrial purposes, whilst pots with non-desurfaced soil from the same field were used as control. Non-inoculated plants were also grown in either control or desurfaced soil. Inoculated plants developed better than non-inoculated plants in desurfaced soil, and in control soil as well, suggesting that the symbiosis was able to overcome the nutrient limitation of the desurfaced soil. Non-inoculated plants were nodulated by native soil born Rhizobium, either in control or desurfaced soil, but they showed low final nitrogen leaf content and low nitrogen fixation activity, suggesting that native rhizobia were ineffective.  相似文献   

4.
Summary Chickpea cultivars (Cicer arietinum L.) and their symbiosis with specific strains of Rhizobium spp. were examined under salt stress. The growth of rhizobia declined with NaCl concentrations increasing from 0.01 to 2% (w : v). Two Rhizobium spp. strains (F-75 and KG 31) tolerated 1.5% NaCl. Of the 10 chickpea cultivars examined, only three (Pusa 312, Pusa 212, and Pusa 240) germinated at 1.5% NaCl. The chickpea — Rhizobium spp. symbiosis was examined in the field, with soil varying in salinity from electrical conductivity (EC) 4.5 to EC 5.2 dSm-1, to identify combinations giving satisfactory yields. Significant interactions between strains and cultivars caused differential yields of nodules, dry matter, and grain. Four chickpea — Rhizobium spp. combinations, Pusa 240 and F-75 (660 kg ha-1), Pusa 240 and IC 76 (440 kg ha-1), Pusa 240 and KG 31 (390 kg ha-1), and Pusa 312 and KG 31 (380 kg ha-1), produced significantly higher grain yields in saline soil.  相似文献   

5.
Although herbicides provide effective weed control, some herbicides may pose serious health and environmental threats. Thus the bioefficacy and the persistence of three formulations of a herbicide, anilofos [GR (granules), W/O (water in oil emulsion), and EC (emulsifier concentration)], at 300, 450, and 600 g ha?1 as pre-emergent applications were evaluated in transplanted rice (Oryza sativa L.). All of the formulations enhanced the rice grain yield by 50% over weedy check and the grain yield was greatest in the 30% EC treatment applied at a 450 g ha?1 rate. Phytotoxic symptoms of anilofos were not observed with any of these formulations on the transplanted rice. Terminal residues of anilofos in the soil and mature rice plants were below the maximum residues limit (MRL, 0.05 mg/kg) in the soil, grains, and straw treated with the various formulations of anilofos. Study showed fast degradation of anilofos in the soil and rice plants.  相似文献   

6.
Glyphosate is the most widely used herbicide in the world, but its effects on non-target organisms, such as arbuscular mycorrhizal fungi (AMF), are unclear. No studies have been found that made reference to effects of glyphosate on AMF spore viability despite its importance as a source of propagules for the perpetuation and spread of AMF in the system. The objective of this study was to evaluate the effect of glyphosate application on AMF spore viability, and their ability to colonize roots. Soil samples were collected from a grassland area located in the Flooding Pampa region (Argentina). We evaluated three herbicide rates: 0, 0.26 and 1× recommended field rate, 10 and 30 days after application. Part of the soil from each tray was used to estimate the spore viability, and the remainder was used as substrate for growing Lolium multiflorum Lam. One month after sowing, total root colonization and percentage of arbuscules and vesicles were determined. The spore viability in herbicide untreated soils was between 5.8- and 7.7-fold higher than in treated soils. This reduction was detected even when the lower rate was applied. Root colonization was significantly lower in plants grown in glyphosate treated soil than in untreated ones. A decrease in arbuscular colonization (but not in vesicles) was found in plants grown in soils treated with the highest herbicide rate. That would indicate that symbiosis functionality was affected, given that arbuscules are the main site for host–fungus nutrient exchange. The results indicate that soil residence time of glyphosate and/or its degradation products was enough to reduce AMF spore viability and their ability to colonize roots. This decrease in propagules viability may affect plant diversity, taking into account the different degrees of mycorrhizal dependency between plant species that may coexist in grassland communities.  相似文献   

7.
The use of efficient bio-inoculants in chickpea is the best way to increase crop productivity under rainfed conditions. To assess the combined effect of bio-inoculants on crop yield, field experiments were conducted during Rabi seasons at Research Station, Punjab Agricultural University, Ballowal Saunkhri, Punjab, India. The application of different bio-inoculants significantly improved number of pods, grain and straw yield of chickpea over the un-inoculated treatment. The combined application of Rhizobium + PSB?+?AM fungi?+?azotobactor inoculums as seed treatment with 75% of recommended phosphorus produced highest grain yield. The nodule count, nodule weight, per cent root colonization of AM fungi and different enzymes activities in soil were also highest in combined bio-inoculants treatment. The present study concluded that combined application of bio-inoculants (Rhizobium, PSB, AM fungi and azotobactor) can save 25% of recommended phosphorus by sustaining the crop yield and improving the soil health.  相似文献   

8.
Nitrogen (N) fixation by legume-Rhizobium symbiosis is important to agricultural productivity and is therefore of great economic interest. Growing evidence indicates that soil beneficial bacteria can positively affect symbiotic performance of rhizobia. The effect of co-inoculation with plant growth-promoting rhizobacteria (PGPR) and Rhizobium, on nodulation, nitrogen fixation, and yield of common bean (Phaseolus vulgaris L.) cultivars was investigated in two consecutive years under field conditions. The PGPR strains Pseudomonas fluorescens P-93 and Azospirillum lipoferum S-21 as well as two highly effective Rhizobium strains were used in this study. Common bean seeds of three cultivars were inoculated with Rhizobium singly or in a combination with PGPR to evaluate their effect on nodulation and nitrogen fixation. A significant variation of plant growth in response to inoculation with Rhizobium strains was observed. Treatment with PGPR significantly increased nodule number and dry weight, shoot dry weight, amount of nitrogen fixed as well as seed yield and protein content. Co-inoculation with Rhizobium and PGPR demonstrated a significant increase in the proportion of nitrogen derived from atmosphere. These results indicate that PGPR strains have potential to enhance the symbiotic potential of rhizobia.  相似文献   

9.
ABSTRACT

Soil fertility and water use are two important aspects that influence rice productivity. This study was conducted to evaluate the performance of in-situ (sesbania and rice bean) and ex-situ (subabul) green manuring along with zinc fertilization on water productivity and soil fertility in rice under rice–wheat cropping system at Indian Agricultural Research Institute, New Delhi, India. Sesbania incorporation recorded higher total water productivity (2.20 and 3.24 kg ha?1 mm?1), available soil nutrients, organic carbon, alkaline phosphatase activity, microbial biomass carbon and increased soil dehydrogenase activity by 39.6 and 26.8% over subabul and rice bean respectively. Among interaction of green manures and zinc fertilization, subabul × foliar application of chelated zinc-ethylenediaminetetraacetic acid at 20, 40, 60 and 80 days after transplanting recorded highest total water productivity (2.56 and 3.79 kg ha?1 mm?1). Foliar application of chelated Zn-EDTA at 20, 40, 60 and 80 days after transplanting recorded significantly higher water productivity than other Zn treatments, however it was statistically similar with foliar application of zinc at active tillering + flowering + grain filling. Sesbania × 5 kg Zn ha?1 through chelated Zn-EDTA, recorded highest available nitrogen, phosphorus, potassium, zinc, manganese, copper and iron than other green manure and Zn fertilization interactions, although it was statistically similar with rice bean × 5 kg Zn ha?1 through chelated Zn-EDTA as soil application. Sesbania × foliar application of 5 kg Zn ha?1 through chelated Zn-EDTA as soil application recorded highest soil enzymatic activities and microbial biomass carbon.  相似文献   

10.
Fluorescence in situ hybridization (FISH) technique and qPCR analyses, targeting atz genes, were applied to detect the presence of simazine-degrading bacteria in an agricultural soil with a history of herbicide application. atzB-targeted bacteria detected by FISH represented 5% of total soil bacteria with potential capability to metabolize the herbicide. The soil natural attenuation capacity was confirmed in soil microcosms by measuring simazine degradation. Moreover, four bacterial strains were isolated from the soil and identified as Acinetobacter lwoffii, Pseudomonas putida, Rhizobium sp. and Pseudomonas sp. The isolates were able to grow using different s-triazine compounds and related metabolites as the sole carbon source. Growth parameters in presence of simazine were calculated using the Gompertz model. Rhizobium sp. showed the highest simazine degradation (71.2%) and mineralization (38.7%) rates, whereas the lowest values were found to A. lwoffii??50.4% of degradation and 22.4% of mineralization. Results from qPCR analyses of atzA, atzB and atzC genes revealed their presence in Rhizobium sp. and A. lwoffii, being atzB and atzC the most abundant functional genes. Rhizobium sp. showed a higher amount of the three biomarkers compared to A. lwoffii: the atzA, atzB and atzC gene copy number per microlitre were, respectively, 101, 102 and 103-fold higher in the former. Therefore the proposed molecular approaches based on the use of atz genes as biomarkers can be considered as useful tools to evaluate the presence and potential capability of degrading-s-triazines soil microorganisms.  相似文献   

11.
Soil-inhabiting fungal pathogen Fusarium oxysporum often causes severe yield losses in many crops. We investigated the effect of a plant growth-promoting fungus, Penicillium sp. EU0013 on Fusarium wilt disease. In dual culture experiments, EU0013 inhibited the growth of Fusarium wilt pathogens by producing an inhibition zone. In experiments using sterile potting medium under controlled conditions, EU0013 significantly reduced the severity of Fusarium wilt on tomato (Solanum lycopersicum L.) and cabbage (Brassica oleracea L. var. capitata). In non-sterile soil, benomyl-resistant mutants of EU0013 were selected by exposing the conidial solution of EU0013 to ultraviolet light. The selected mutant EU0013_90S isolate did not show any distinct differences from EU0013 in colony characteristics, growth rate or antifungal activity against Fusarium wilt pathogens in dual culture. The effect of EU0013_90S on tomato wilt was studied under greenhouse conditions using non-sterile soil. Two-weeks old tomato seedlings were dipped in four different concentrations of EU0013_90S conidial suspension (1?×?103, 1?×?104, 1?×?105, and 1?×?106 conidia mL–1). Seedlings were then planted in soil inoculated with either F. oxysporum f. sp. lycopersici race 1 CU1 or race 2 JCM 12575 (1?×?106 bud-cells g–1). We found the greatest disease suppression occurred when seedlings were dipped in the highest concentration of EU0013_90S conidia. This same inoculum concentration of EU0013_90S also resulted in the highest disease reduction in soil infested with JCM 12575. Higher root colonization with EU0013_90S showed a significant reduction in Fusarium wilt disease, suggesting that colonization by Penicillium sp. EU0013_90S is important for efficient biocontrol of these diseases.  相似文献   

12.
Yield decline in yam may not only be due to soil nutrient depletion but also to the activity of soil microflora. Arbuscular mycorrhizal (AM) symbiosis helps in plant nutrition but may be affected by the application of fertilizer. The effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on the AM colonization, leaf nutrient concentrations, and tuber yields of eleven genotypes of Dioscorea rotundata were investigated at Ibadan, Nigeria. The soil was ferric luvisol. Eleven genotypes were selected from the previously conducted screening of 75 genotypes of D. rotundata for fertilizer response. Four application rates: 0, 200, 400, and 600 kg ha?1 of NPK 15-15-15 were applied in a split plot design with four replications. Fertilizer rate was the main plot and variety was the sub plot. Percentage AM colonization was significantly reduced at 600 kg ha?1 but not at lower rates when compared to zero rate and it was negatively correlated with leaf N, P, and zinc (Zn) concentrations. Leaf N concentrations were significantly increased at 200 kg ha?1 in five genotypes and at 600 kg ha?1 in two genotypes compared to zero application. Leaf P and K concentrations were decreased with the application of fertilizer in most of the genotypes. The NPK fertilizer of 15-15-15 at the rate of 200–400 kg ha?1 gave yield response in eight genotypes of D. rotundata, with minimal or no effect on their AM colonization when compared to zero application. Long term study on the effect of fertilizer application on AM symbiosis in yam is recommended.  相似文献   

13.
The bacteria capable of degrading pentachlorophenol (PCP) were isolated from soil. In the soil perfused with 40 ppm PCP solution, PCP was decomposed and five chlorine atoms of PCP were liberated as chloride ion after about 3 weeks. Re-addition of PCP after its degradation, accelerated the rate of PCP degradation and de-chlorination. After the addition of PCP to the soil three times, bacteria which grew on PCP agar were counted to be about 2 × 107 per gram dry soil. In the liquid medium inoculated with the perfused soil, PCP degradation and complete de-chlorination were found. In this case, multiplication of bacteria capable of growing on PCP agar was found. The bacteria capable of growing on and degrading PCP in the medium with inorganic salts and 40 ppm PCP as a sole source of carbon were isolated from the agar plates for enumeration of the bacteria. From the morphological and physiological properties of the isolated bacteria, the genus of the bacteria was considered to be Pseudomonas or a closely related one. In the culture medium with PCP and inorganic salts, the bacteria degraded PCP and completely de-chlorinated it. The de-chlorination process corresponded approximately to PCP disappearance. Pathways of PCP metabolism are not yet elucidated.  相似文献   

14.
Interactions between Rhizobium and soil rhizosphere microorganisms on agar were examined using the giant-colony and the streak methods. The interactions between microorganisms often varied when the test method was changed. Soil and rhizosphere microorganisms produced greater stimulation or inhibition of Rhizobium when the Rhizobium was suspended within the agar. Giantcolonies of Rhizobium were limited in their effects upon soil microorganisms. When microorganisms were streaked at right angles to each other, interaction occurred only between those streaked 3 days apart and not between those streaked on the same day. Inhibition effects were very pronounced and stimulation was less evident with the streak method. Toxin production was implicated with selfinhibition of rhizobia and soil microorganisms. Stimulatory, inhibitory and lytic activity of soil microorganisms were confirmed with sterile broth extracts of 2 and 5 day old cultures. pH changes in the media as a result of microbial activity were not considered responsible for the interactions observed.  相似文献   

15.
菌剂与肥料配施对矿区复垦土壤白三叶草生长的影响   总被引:2,自引:0,他引:2  
采用盆栽试验研究了矿区复垦土壤菌剂与肥料的不同配施对白三叶草(Trifolium repens Linn)生长的影响。结果表明: 双接种VA 菌根真菌(Glomus mossea)和根瘤菌(Rhizobium)能显著提高白三叶草根瘤数、根瘤鲜重和固氮酶活性, 根瘤数在有机肥双接种与无机肥双接种处理之间差异不显著, 而根瘤鲜重和固氮酶活性差异显著; 肥料与各菌剂组合处理中, 有机肥双接种处理的白三叶草分枝数、干物质重最大; 在白三叶草生长40 d 和150 d 时, 双接种处理的叶片数均为各处理中最大值; 接种VA 菌根真菌、根瘤菌和双接种均可增加白三叶草根系的菌根侵染率和土壤孢子数, 总体表现为双接种处理>接种VA 菌根真菌>接种根瘤菌, 有机肥相应处理>无机肥相应处理>对照; 肥料与菌剂的配合施用可有效提高植物对土壤氮、磷、钾养分的吸收。在矿区复垦土壤上有机肥与VA 菌根真菌和根瘤菌菌剂配施能显著促进白三叶草的生长, 是提高矿区复垦土壤植被恢复中比较适宜的组合方式。  相似文献   

16.
Effects of seed and root exudates obtained from common bean on the proliferation of Rhizobium sp. (Phaseolus) were examined in a combination of three plant cultivars with three Rhizobium strains. In the first experiment, seed or root exudate was mixed with an Andosol soil extract, and bacterial proliferation in the mixture was traced. Seed exudate was prepared from hydroponic solution used in seed imbibition for 24 h, and a series of root exudates was prepared from a hydroponic solution collected every 24 h from the initiation of rooting up to 96 h after rooting. Regardless of the common bean cultivars and Rhizobium strains used, Rhizobium population markedly increased of the 24 h of culture in the mixture containing seed exudates, whereas a negligible increase was detected in the mixture with root exudates. The mixture containing root exudates collected within a period of 72–96 h after initial rooting (96–120 h after seed imbibition) exerted an inhibitory effect on Rhizobium proliferation. The seed exudates contained large amounts of sugars, amino acids, nitrogen, phosphorus, potassium, and magnesium compared to any root exudates. In the second experiment, Rhizobium was inoculated directly to common bean seeds sowed in a vermiculite bed which was sterilized and moistened with a plant nutrient solution. Compared with the control (without seed), a remarkable increase in the number of bacterial cells was observed in all the combinations of plant cultivars and Rhizobium strains 24 h after sowing. These results reveal that seed exudates of common bean have a substantial potential to promote Rhizobium proliferation, and that root exudates in a particular period of culture contain some inhibitory factors.  相似文献   

17.
Summary The Rhizobium-legume symbiosis in arid ecosystems is particularly important for locations where the area of saline soils is increasing and becoming a threat to plant productivity. Legumes, which are usually present in arid ecosystems, may be adapted to fix more N2 under saline conditions than legumes grown in other habitats.Legumes are known to be either sensitive or moderately resistant to salinity. The salt sensitivity can be attributed to toxic ion accumulations in different plant tissues, which disturb some enzyme activities.Among the basic selection criteria for salt-tolerant legumes and rhizobia are genetic variability within species with respect to salt tolerance, correlation between accumulations of organic solutes (e. g., glycine betaine, proline betaine, and proline) and salt tolerance, and good relationships between ion distribution and compartmentation, and structural adaptations in the legumes.Salt stress reduces the nodulation of legumes by inhibiting the very early symbiotic events. Levels of salinity that inhibit the symbiosis between legumes and rhizobia are different from those that inhibit the growth of the individual symbionts. The poor symbiotic performance of some legumes under saline conditions is not due to salt limitations on the growth of rhizobia.Prerequisites for a successful Rhizobium-legume symbiosis in saline environments include rhizobial colonization and invasion of the rhizosphere, root-hair infection, and the formation of effective salt-tolerant nodules.The possibility of exploring the Rhizobium-legume symbiosis to improve the productivity of saline soils is reviewed in this paper.  相似文献   

18.
The possible interaction of herbicides Bromoxynil and Afalon S with Azospirillumspp. and growth of maize was investigated in a greenhouse experiment. Neither inoculation nor herbicide application with or without inoculation had significant effect on the major groups of soil microflora (bacteria, actinomycetes, and fungi). The highest values of nitrogenase as well as dehydrogenase activity were recorded in treatment received only Azospirillum. Incorporation in soil of either Bromoxynil or Afalon S at the recommended field dose seemed to have no significant effect on the enzymatic activities, while application of these herbicides with Azospirillum had stimulatory effects in some cases. The application of either Bromoxynil or Afalon S significantly increased the dry weight of roots and shoots at 45 days period. The effect of herbicide on plant growth was more pronounced when applied with Azospirillum and the highest stimulatory effect was observed when Afalon S was applied with the N2-fixing microorganism.  相似文献   

19.
The study evaluated the effects of phosphorus (0, 20, 30, and 40 kg P2O5 ha?1) and biofertilizers [Rhizobium (Rhizobium leguminosarum bv viciae), plant growth promoting rhizobacteria (PGPR) (Pseudomonas fluorescens), Rhizobium + PGPR, and uninoculated control] in lentil. Application of 40 kg P2O5 ha?1 resulted in the highest number of nodules, nodule dry weight, leghemoglobin content in nodules, chlorophyll content, yield attributes, and grain yield. Coinoculated treatment performed better than uninoculated control, and individual inoculations of Rhizobium and PGPR in terms of all above mentioned parameters. Application of 20 kg P2O5 ha?1 + Rhizobium inoculation gave statistically similar and 20 kg P2O5 ha?1 + Rhizobium + PGPR inoculation gave significantly higher grain yield than that by 40 kg P2O5 ha?1 alone. The use of Rhizobium alone and Rhizobium + PGPR consortium can save not only 20 kg P2O5 ha?1 but also increase the grain yield of lentil.  相似文献   

20.
Glyphosate is a widely used nonselective herbicide for the control of agricultural weeds. It is being increasingly used in glyphosate resistant genetically modified plants. However, there are few studies on its effects on the nutritional status of soybean, particularly on the uptake of zinc (Zn). Two experiments were conducted under field conditions in a Typic Quartzipsamment and an Orthic Ferralsol to investigate the effect of glyphosate application × Zn interaction on soil fertility, yield components, seed yield (SY), shoot dry weight (SDW) yield, and nutritional status of soybean. The five Zn rates 0, 3, 6, 9, and 12 kg ha?1 were used in two soybean varieties [BRS 133 (conventional—NGM) and its essentially derived transgenic line BRS 245RR (GM), which was divided into: with (+Gly) and without (–Gly) glyphosate application. Only the P (phosphorus) and Zn available concentrations in the soil were impacted by Zn rates. However, the available P concentration only decreased in the soil planted with GM soybean. Mehlich 1 and diethylenetriaminepenta acetic acid–triethanolamine (DTPA–TEA), 7.3 extractants were effective to determine the available Zn. In the two crop sites, the number of pods per plant (NPP) and the SDW yield were affected by the interaction varieties × Zn. SY was influenced by the application of the herbicide, reducing a potential phytotoxic effect with the use of high rates. Regarding the nutrients, only the foliar calcium (Ca), boron (B), iron (Fe), and manganese (Mn) concentrations were negatively affected by glyphosate, and in the case of Zn, the difference occurred only between the varieties BRS 133 and BRS 245RR.  相似文献   

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