Microbial community diversity analysis of <i>Panax ginseng</i>rhizosphere and non-rhizosphere soil using randomly amplified polymorphic DNA method

DNA sequence diversities of soil microbial communities in rhizosphere and non-rhizosphere of 1 - 6 years Panax ginseng were evaluated by random amplified polymorphic DNA (RAPD). Total genomic DNA of soil samples were amplified by twenty-four out of two hundred random primers. The products were separated in agarose gel, and 359 and 181 reliable fragments were generated, of which, 324 and 123 were polymorphic. The gene diversity index, Shannon’s information index, and similarity coefficient were calculated, and results showed that, diversity of soil microbial community at DNA level was present. Furthermore, with the increasing of P. ginseng growing at one site, deference on soil microbial community DNA sequence between rhizosphere and non-rhizosphere tend to be more and more significant. In addition, RAPD technique was proved to be an effective tool to assess the diversity of soil microbial communities. From results we deduced that, the ecological function that performed by soil microbes may changed following the change of microbial community in rhizospheric and non-rhizospheric soils, and finally broke the balance of soil nutrition and energy cycle, soil spatial structure, microbial ecology etc.

Morphological Characterization of Arbuscular Mycorrhizal Fungi Associated with the Rhizosphere According to the Age of Xanthosoma sagittifolium L. Schott Plants in the Field

The objective of this work was to carry out a morphological characterization of arbuscular mycorrhizal fungi in the rhizosphere of Xanthosoma sagittifolium L. Schott plants. The plant material used was the white and red cultivars of X. sagittifolium, belonging to age intervals of 3 - 6, 6 - 9, and 9 - 12 months. Three harvest sites were chosen in the Central Region of Cameroon. In each site, soil from the rhizosphere and plant roots was collected in a randomized manner. In the field, the agronomic parameters were evaluated. The physicochemical characteristics of the soils, the mycorrhization index, and the morphological characterization of the mycorrhizal types of each site were carried out. The results obtained show that the agronomic growth parameters varied significantly using the Student Newman and Keuls Test depending on the harvest sites. The soils’ pH in all sites was acidic and ranged between 4.6 and 5.8. The Nkometou site has a loamy texture while the Olembe and Soa sites have loam-clay-sandy and loam-clay textures respectively. The highest mycorrhization frequencies appeared at the Nkometou site, with 75 and 87.33% of the white and red cultivars plant roots at 6 - 9 and 3 - 6 months. The relative abundance of AMF arbuscular mycorrhizal fungal spores in the rhizosphere of X. sagittifolium plants varied with age and cultivar. There were 673 spores between 9 - 12 months in Nkometou in the red cultivar. Six AMF genera were identified in all the different soils collected: Acaulospora sp., Funneliformis sp., Gigaspora sp., Glomus sp., Scutellospora sp., and Septoglomus sp. The genus Glomus sp. was the most present at all age intervals in both cultivars.

Synergistic mechanisms of AMF and biochar driving rhizosphere fungal community in shallot in barren soil

The addition of biochar(BC)or Arbuscular mycorrhizal fungi(AMF)alone has been reported to promote plant growth,while their synergistic effects on Allium schoenoprasum root morphology and rhizosphere fungal community in barren soil is still unclear.In this study,we investigated the effects of BC and AMF(Funneliformis mosseae)on plant growth and root morphology in barren soil and revealed the structure of soil fungal communities Therefore,a greenhouse pot trial consisting of five treatments was enforced.The results showed that the combination of biochar and AMF significantly improved plant biomass,nutrient uptake,mycorrhizal colonization rates and soil properties and significantly impacted rhizosphere fungal community composition and structure.Biochar significantly increased the fungal community stability and enhanced their positive correlation with plants.Our findings indicated that the combination of AMF and biochar play synergic role for plant growth and rhizosphere fungal community in barren soil.

Soybean(Glycine max)rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorusmineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus(P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean(Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase(AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the ɑ-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoCharboring bacteria, such as Cupriavidus.

Analysis of Microbial Community Structure and Diversity in Crop Rhizosphere Soil Based on Illumina NovaSeq Sequencing Platform

[Objectives]To make full use of crop rhizosphere microbial resources.[Methods]Illumina NovaSeq sequencing platform was used to analyze the richness and diversity of microbial community structure in rhizosphere soil of rice and maize crops in Baitu Town,Gaoyao District,Zhaoqing City.[Results]A total of 14936 OTUs of bacteria and 1905 OTUs of fungi were obtained from three samples of rice rhizosphere soil,and 13437 OTUs of bacteria and 1413 OTUs of fungi were obtained from three samples of maize rhizosphere soil.The diversity and richness of bacterial communities were higher than those of fungi.There are differences in soil bacterial and fungal communities among different crop samples.The analysis of species with bacteria difference at genus level among crop rhizosphere soil samples showed that 18 genera with significant differences were obtained from 6 samples;species analysis of fungi at the genus level showed that 3 genera with significant differences were obtained from 6 samples.[Conclusions]The research results of this paper have positive significance for the development and utilization of soil resources in Zhaoqing City and the full exploitation of rice and maize rhizosphere microbial resources.

Effect of root derived organic acids on the activation of nutrients in the rhizosphere soil

Four types of soils, including brown coniferous forest soil, dark brown soil, black soil, and black calic soil, sampled from three different places in northeast China were used in this test. The functions of two root-derived organic acids and water were simulated and compared in the activation of mineral nutrients from the rhizosphere soil. The results showed that the organic acids could activate the nutrients and the activated degree of the nutrient elements highly depended on the amount and types of the organic acid excreted and on the physiochemical and biochemical properties of the soil tested. The activation effect of the citric acid was obviously higher than that of malic acid in extracting Fe, Mn, Cu, and Zn for all the tested soil types. However, the activation efficiencies of P, K, Ca, and Mg extracting by the citric acid were not much higher, sometimes even lower, than those by malic acid. The solution concentration of all elements increased with increase of amount of the citric acid added.

Effects of Concentration of NO_3^--N on Root Vigor and Rhizosphere pH of Winter Wheat Seedlings

[Objective] The aim was to research the effect of concentration of NO-3-N on root vigor and rhizosphere pH of winter wheat seedlings under water culture.[Method]By selecting Hoagland's nutritional solution as cultural medium and winter wheat as material of experiment,on the basis,testing root vigor,nutrient solution NO-3 and change of pH values under the different level of disposal,such as high(containing NO-3-N 15 mmol/L),medium(containing NO-3-N 7.5 mmol/L)and lower(containing NO-3-N 2.5 mmol/L).[Result]The results of this research showed that the effect of different nitrogen level on the wastage of nutrient solution NO-3,the changes of pH values and root vigor is obvious under the hydroponics condition.[Conclusion]Though NO-3 is a safe nitrogen sources when it was supplied to plants too more,it would restrain assimilation on nitrate nitrogen farther,but when it was supplied to plants too little,it would lead to deficiency of NO-3 that plants uptake and decrease of root activity,so it isn't useful to wheat young seedling to absorb nitrogen nutrition.

Nutrient characteristics in rhizosphere of pure and mixed plantations of Manchur ian walnut and Dahurian larch

A comparison study was made for the characteristics of pH value, orga nic matter content, nutrient element N, P and K contents in rhizosphere soils of pure and mixed plantations of Manchurian walnut and Dahurian larch and in bulk soils. The results show that the pH values of rhizosphere soil for all the plant ations except the pure walnut stand, which was slightly higher, were lower than those of bulk soils, while the organic matter contents in the rhizosphere soil f or all the plantations except the mixed plantation, which was slightly lower, we re higher than that in bulk soil. There exists a relative nitrogen accumulation in the rhizosphere and the extent to which the nitrogen accumulates is closely r elated to tree species and mixed pattern. As far as the total P and K contents a re considered, there exists a deficient tendency in rhizosphere in comparison wi th bulk soil. The element N, P and K are all mobilized in the rhizosphere of the pure or mixed plantation, characterized by the higher contents of the available N, P and K in the rhizosphere. The available N content in the rhizosphere of th e larch in mixed plantation was obviously higher than that of its pure plantatio n, whereas the available P and K contents in the rhizosphere of walnut in the mi xed plantation, on the other hand, were significantly higher than those of its p ure plantation.

Studies on the Microbial Community in the Rhizosphere Soil of Dongxiang Wild Rice

[Objective] The aim was to study the characteristics of microbial community in the rhizosphere soil of Dongxiang wild rice（Oryza rufipogon Griff.）.[Method] The microbial biomass carbon and nitrogen was estimated by the chloroform fumigation extraction method;the microbial community composition and Nitrogen cycling microbial functional groups were investigated by the Dilution plate culture method and the most probable number methods respectively.[Result] The microbial biomass carbon and nitrogen,in rhizosphere soil of Dongxiang Wild Rice was 83.02±18.23 mg/kg soil and 16.98±2.54 mg/kg soil,which was lower than that of ordinary cultivated rice;The relationship between the number of culturable microbial groups was bacteriaactinomycetesfungi,and the Nitrogen cycling microbial physiological groups was as the following：ammonifying bacteriaaerobic azotobacteriadenitrobacteriaanaerobic azotobacterianitrobacterianitrosobacteria.[Conclusion] The microbial community in the rhizosphere soil of Dongxiang Wild Rice was different from that of the ordinary cultivated rice.

The variation of nutrient concentration in the rhizosphere of larch and ash in mixed and monoculture stands

Soil samples were taken from rhizosphere zone and off-rhizosphere zone of ash (Fraxinus mandshurica Rupr.) and larch (Larix olgensis Henry) in mixed and monoculture stands, and the nutrient concentration of N, P, and K was analyzed to study the effect of nutrients variation on yield improvement in the mixed stand. The result showed that: 1) The stand level total soil N concentration and available N in the mixed stand was similar to that in the monoculture stand of ash, but higher than that in monoculture stand of larch. The total N and available N concentration in rhizosphere soil of ash in the mixed stand was similar to that in the monoculture stand of ash, but the available N concentration in rhizosphere of larch in mixed stand was much higher than in its monoculture. 2) The stand level total P, total K concentration in the mixed stand was similar to that in monocul-ture stands of both species, but available P and K was more concentrated in the mixed stand than in the monoculture stands of ash. The rhizosphere available P and K of ash in the mixed stand was 44.1% and 13.5% (for the 9-yr-old stands) and 79.6% and 25.6% (for the 21-yr-old stands) higher than that in its monoculture. The improvement of soil P and K availability in the mixed stand is concluded.

Effects of Arbuscular Mycorrhizal Fungi (AMF) on Distribution of Pb Forms in Rhizosphere of Upland Rice

[Objective] The aim was to study the effects of AMF on distribution of Pb in different chemical forms in rhizosphere soil of upland rice. [Method] A pot experiment was conducted to explore effects of AMF inoculation on distribution of Pb in different forms in rhizosphere of rice (Oryzal sativa L.) with Pb in different concentrations (0, 300 and 600 mg/kg). [Result] With inoculation adopted, mycorrzhial colonization rate of upland rice under Pb pdlution root declined substantially with Pb increasing in soils (P<0.05). Compared with non-inoculation, rhizosphere pH significantly enhanced by inoculation; when Pb was at 300 mg/kg, glomalin content in soils improved significantly by inoculation; when Pb was at 600 mg/kg, glomalin content in soils declined substantially (P<0.05). In addition, inoculation significantly improved contents of Pb in exchangeable and organic forms, but lowered Pb in carbonate bound and Fe-Mn oxides bound forms (P<0.05). [Conclusion] The research indicated that AMF inoculation would change distribution of Pb in different forms in rhizosphere soils of upland rice.

The rhizosphere pH change of Pinus koraiensis seedlings as affected by N sources of different levels and its effect on the availability and uptake of Fe, Mn, Cu and Zn

Dark brown forest soil was collected from the upper 20 cm soil layer in Changbai Mountain Research Station of Ecosystem, Chinese Academy of Sciences. The soil was amended with two different forms of nitrogen fertilizers: NO3- as Ca(NO3)2, NH4+ as NH4Cl at the concentrations of 50, 100, 200 and 400 mgkg-1 respectively. The experiment was carried out with 2-yr-old Pinus koraiensis seedlings in pot. The pH change of rhizosphere soil and the contents of available Fe, Mn, Cu, and Zn in soil and leaves were analyzed. The result indicated that the addition of NH4--N decreased the rhizosphere pH value, while the addition of NO3--N increased the rhizosphere pH value in contrast with the control treatment. The direction and extent of the pH change mainly depended on N source and its concentrations applied. The rhizosphere pH change had a remarkable influence on the availability of the micronutrients in the rhizosphere, and thereafter affected the nutrient uptake by the seedlings. The contents of available mineral nutrients had a negative correlation with the pH value in the rhizosphere soil. The contents of available mineral nutrients in leaves were positively correlated to the levels of the available nutrients in the rhizosphere soils.

The pH change in rhizosphere of Pinus koraiensis seedlings as af-fected by different nitrogen sources and its effect on phosphorus availability

Root mat method described by Kuchenbuch and Jungk was used to study the rhizosphere processes. The experi-ment was carried out on two years old Pinus koraiensis seedlings. Soil samples collected from the upper 20-cm soil layer in Changbai Mountain were treated with three different forms of nitrogen fertilizers: NO3--N, NH4+-N and NH4NO3. The results showed that the soil pH and available P near the roots were all lower than in the bulk soil in control treatment. NH4+-N applica-tion greatly decreased the soil pH near the roots compared to the control treatment and promoted the absorption of phosphorus, which led to a more remarkable depletion region of available P. On the contrary, the rhizosphere soil pH was higher than in the bulk soil in treatments with NO3--N and retarded the P absorption, which led to a nearly equal available P contents to the bulk soil. In treatment with NH4NO3, the rhizosphere soil pH was only a little lower than that in the control treatment and its effects on P absorption is mediate between the treatments with NH4+-N and NO3--N.

Inuence of oxytetracycline on the structure and activity of microbial community in wheat rhizosphere soil

The microbial community composition in wheat rhizosphere was analyzed by detecting colony forming units （CFUs） in agar plates. The total CFUs in rhizosphere were 1.04×10^9/g soil with 9.0×10^8/g bacteria, 1.37×10^8/g actinomyces and 3.6×10^6/g fungi. The 10 dominant bacteria were isolated from wheat rhizosphere and were grouped into genus Bacillus according to their full length 16S rRNA gene sequences. Although belonging to the same genus, the isolated strains exhibited different sensitivities to oxytetracycline. When a series of the rhizosphere soil was exposed under various concentrations of oxytetracycline, the microbial community structure was highly affected with significant decline of CFUs of bacteria and actinomyces （22.2% and 31.7% at 10 mg/kg antibiotic, respectively）. This inhibition was clearly enhanced with the increase exposure dosage of antibiotic and could not be eliminated during 30 d incubation. There was no obvious influence of this treatment on fungi population. Among the four soil enzymes （alkaline phosphatase, acidic phosphatase, dehydrogenase and urease）, only alkaline phospbatase was sensitive to oxytetracycline exposure with 41.3% decline of the enzyme activity at 10 mg/kg antibiotic and further decrease of 64.3%-80.8% when the dosage over 30 mg/kg.

Changes in fungal community and diversity in strawberry rhizosphere soil after 12 years in the greenhouse

Soil fungi play a very important role in the soil ecological environment. In agricultural production, long-term monoculture and continuous cropping lead to changes in fungal community diversity. However, the effects of long-term monoculture and continuous cropping on strawberry plant health and fungal community diversity have not been elucidated. In this study, using high-throughput sequencing(HTS), we compared the fungal community and diversity of strawberry rhizosphere soil after various durations of continuous cropping(0, 2, 4, 6, 8, 10 and 12 years). The results showed that soil fungal diversity increased with consecutive cropping years. Specifically, the soil-borne disease pathogens Fusarium and Guehomyces were significantly increased after strawberry continuous cropping, and the abundance of nematicidal(Arthrobotrys) fungi decreased from the fourth year of continuous cropping. The results of correlation analysis suggest that these three genera might be key fungi that contribute to the changes in soil properties that occur during continuous cropping. In addition, physicochemical property analysis showed that the soil nutrient content began to decline after the fourth year of continuous cropping. Spearman's correlation analysis showed that soil pH, available potassium(AK) and ammonium nitrogen(NH_4^+-N) were the most important edaphic factors leading to contrasting beneficial and pathogenic associations across consecutive strawberry cropping systems.

Heavy metal (Pb,Zn) uptake and chemical changes in rhizosphere soils of four wetland plants with different radial oxygen loss

Lead and Zn uptake and chemical changes in rhizosphere soils of four emergent-rooted wetland plants;Aneilema bracteatum,Cyperus alternifolius,Ludwigia hyssopifolia and Veronica serpyllifolia were investigated by two experiments：（1） rhizobag filled with ＂clean＂ or metal-contaminated soil for analysis of Pb and Zn in plants and rhizosphere soils;and （2） applied deoxygenated solution for analyzing their rates of radial oxygen loss （ROL）.The results showed that the wetland plants with different ROL rates had significant effects on the mobility and chemical forms of Pb and Zn in rhizosphere under flooded conditions.These effects were varied with different metal elements and metal concentrations in the soils.Lead mobility in rhizosphere of the four plants both in the ＂clean＂ and contaminated soils was decreased,while Zn mobility was increased in the rhizosphere of the ＂clean＂ soil,but decreased in the contaminated soil.Among the four plants,V.serpyllifolia,with the highest ROL,formed the highest degree of Fe plaque on the root surface,immobilized more Zn in Fe plaque,and has the highest effects on the changes of Zn form （EXC-Zn） in rhizosphere under both ＂clean＂ and contaminated soil conditions.These results suggested that ROL of wetland plants could play an important role in Fe plaque formation and mobility and chemical changes of metals in rhizosphere soil under flood conditions.

Dynamics of Microbial Communities in Bulk and Developing CucumberRhizosphere Soil

The microbial population dynamics in bulk and developing cucumber rhizospheres were studiedby cultivation and cultivation-independent approach based on directly extracted DNA toprovide baseline data. Soil and rhizosphere samples were taken from tested field 2, 4, 7 and10 weeks after the seeds were planted, which was positively related to the corresponding dateof cucumber growth stages. The plate culture amount showed that total number of bacteria,fungi and actinomyces began to rise when cucumber planted and quickly reached peak at seedlingor blossom period, but decreased slightly later. Bacterial population in rhizosphere washigher by comparison with that of counterpart except for seedling and flowering stages, butthe shift trend of them were quite similar all the time. Nitrogen fixating, nitrobacter andammonifying bacteria showed the same change tendency in population as bacteria and actinomycesdid, however, cellulose-decomposing bacteria had the contrary rhizosphere effect as cucumberdeveloped. Data revealed that positive relevance existed between the dominant rhizospheremicrobe population and cucumber development. PCR was employed to amplify the V3 region of 16SrDNA, then the products were subjected to denaturing gradient gel electrophoresis(DGGE). DGGEprofile indicated that a few microbe species lived stable in farmland soil, but some wereinfluenced by population due to cucumber roots growth. Significant difference was observed inbulk and rhizosphere soils especially for the seedling and flowering samples. Few prominentbands in DGGE patterns, which displayed stronger or less illumination, means the representativebacteria had great population variation in that period. These phenomena indicated thatflowering cucumber heavily affected rhizosphere bacteria, or the bacteria, most probably theuncultured bacteria, functioned specially to cucumber blossom. Most detected bands with noillumination change in DGGE quite possibly represent the indigenous microbes that wereessential for constructing and stabilizing farmland microecological environment.

Effects of reduced nitrogen and suitable soil moisture on wheat(Triticum aestivum L.) rhizosphere soil microbiological,biochemical properties and yield in the Huanghuai Plain,China

Soil management practices affect rhizosphere microorganisms and enzyme activities, which in turn influence soil ecosystem processes. The objective of this study was to explore the effects of different nitrogen application rates on wheat(Triticum aestivum L.) rhizosphere soil microorganisms and enzyme activities, and their temporal variations in relation to soil fertility under supplemental irrigation conditions in a fluvo-aquic region. For this, we established a split-plot experiment for two consecutive years(2014–2015 and 2015–2016) in the field with three levels of soil moisture: water deficit to no irrigation(W1), medium irrigation to(70±5)% of soil relative moisture after jointing stage(W2), and adequate irrigation to(80±5)% of soil relative moisture after jointing stage(W3);and three levels of nitrogen: 0 kg ha^–1(N1), 195 kg ha^–1(N2) and 270 kg ha^–1(N3). Results showed that irrigation and nitrogen application significantly increased rhizosphere microorganisms and enzyme activities. Soil microbiological properties showed different trends in response to N level;the highest values of bacteria, protease, catalase and phosphatase appeared in N2, while the highest levels of actinobacteria, fungi and urease were observed in N3. In addition, these items performed best under medium irrigation(W2) relative to W1 and W3;particularly the maximum microorganism(bacteria, actinobacteria and fungi) amounts appeared at W2, 5.37×10^7 and 6.35×10^7 CFUs g^–1 higher than those at W3 in 2014–2015 and 2015–2016, respectively;and these changes were similar in both growing seasons. Microbe-related parameters fluctuated over time but their seasonality did not hamper the irrigation and fertilization-induced effects. Further, the highest grain yields of 13 309.2 and 12 885.7 kg ha^–1 were both obtained at W2 N2 in 2014–2015 and 2015–2016, respectively. The selected properties, soil microorganisms and enzymes, were significantly correlated with wheat yield and proved to be valuable indicators of soil quality. These results clearly demonstrated that the combined treatment(W2 N2) significantly improved soil microbiological properties, soil fertility and wheat yield on the Huanghuai Plain, China.

Influence of Indian mustard (Brassica juncea) on rhizosphere soil solution chemistry in long-term contaminated soils:A rhizobox study

This study investigated the influence of Indian mustard （Brassicajuncea） root exudation on soil solution properties （pH, dissolved organic carbon （DOC）, metal solubility） in the rhizosphere using a rhizobox. Measurement was conducted following the cultivation of Indian mustard in the rhizobox filled four different types of heavy metal contaminated soils （two alkaline soils and two acidic soils）. The growth of Indian mustard resulted in a significant increase （by 0.6 pH units） in rhizosphere soil solution pH of acidic soils and only a slight increase （〈 0.1 pH units） in alkaline soils. Furthermore, the DOC concentration increased by 17-156 mg/L in the rhizosphere regardless of soil type and the extent of contamination, demonstrating the exudation of DOC from root. Ion chromatographic determination showed a marked increase in the total dissolved organic acids （OAs） in rhizosphere. While root exudates were observed in all soils, the amount of DOC and OAs in soil solution varied considerably amongst different soils, resulting in significant changes to soil solution metals in the rhizosphere. For example, the soil solution Cd, Cu, Pb, and Zn concentrations increased in the rhizosphere of alkaline soils compared to bulk soil following plant cultivation. In contrast, the soluble concentrations of Cd, Pb, and Zn in acidic soils decreased in rhizosphere soil when compared to bulk soils. Besides the influence of pH and DOC on metal solubility, the increase of heavy metal concentration having high stability constant such as Cu and Pb resulted in a release of Cd and Zn from solid phase to liquid phase.

The role of arbuscular mycorrhiza on change of heavy metal speciation in rhizosphere of maize in wastewater irrigated agriculture soil

To understand the roles of mycorrhiza in metal speciation in the rhizosphere and the impact on increasing host plant tolerance against excessive heavy metals in soil, maize(Zea mays L.) inoculated with arbuscular mycorrhizal fungus(Glomus mosseae) was cultivated in heavy metal contaminated soil. Speciations of copper, zinc and lead in the soil were analyzed with the technique of sequential extraction. The results showed that,in comparison to the bolked soil, the exchangeable copper increased from 26% to 43% in non-infected and AM-infected rhizoshpere respectively; while other speciation (organic, carbonate and Fe-Mn oxide copper) remained constant and the organic bound zinc and lead also increased but the exchangeable zinc and lead were undetectable. The organic bound copper, zinc and lead were higher by 15%, 40% and 20%, respectively, in the rhizosphere of arbuscular mycorrhiza infected maize in comparison to the non-infected maize. The results might indicate that mycorrhiza could protect its host plants from the phytotoxicity of excessive copper, zinc and lead by changing the speciation from bio-available to the non-bio-available form. The fact that copper and zinc accumulation in the roots and shoots of mycorrhia infected plants were significantly lower than those in the non-infected plants might also suggest that mycorrhiza efficiently restricted excessive copper and zinc absorptions into the host plants. Compared to the non-infected seedlings, the lead content of infected seedlings was 60% higher in shoots. This might illustrate that mycorrhiza have a different mechanism for protecting its host from excessive lead phytotoxicity by chelating lead in the shoots.