Integrated Fertilization Regimes Boost Heavy Metals Accumulation and Biomass of <i>Sedum alfredii</i> Hance

The hyperaccumulator Sedum alfredii Hance (S. alfredii) may be employed for zinc (Zn) and cadmium (Cd)-polluted soil remediation. However, the low phytoremediation efficiency, related to the low biomass production, limits its use with that purpose. In this experiment, nitrogen (N), phosphorus (P), and potassium (K) fertilizers, and organic manure were applied to investigate the phytoremediation ability of S. alfredii. Hydroponic and pot experiments were conducted using Zn-Cd polluted soil. The hydroponic experiment indicated that appropriate fertilizer application could increase (p < 0.05) the amount of accumulated Zn and Cd in S. alfredii. When N supply ranged from 0.5 to 2.5 mmol L⁻¹, it could improve growth and accumulation of Zn and Cd in whole plants of S. alfredii. The 1 mmol L^-1 N was an optimal N dosage for shoot biomass production and Cd accumulation in shoots, while the 2.5 mmol L^-1 was an optimal N dosage for Zn accumulation in shoots. Both low (<0.05 mmol L^-1) and high (>0.8 mmol L^-1) P supply decreased growth, and Zn/Cd accumulation in whole plants of the studied species. The 0.1 mmol L^-1 P was an optimal dosage for S. alfredii biomass production and Zn/Cd accumulation in shoots. The supply levels within the range from 0.3 to 1 mmol L^-1 K could significantly improve the biomass production of S. alfredii and its capability to accumulate Zn and Cd in the biomass. The 0.5 mmol L^-1 K was an optimal dosage for the whole biomass production and Zn accumulation in shoots, while the 1 mmol L^-1 was an optimal K dosage for Zn accumulation in shoots, which was 17.2% higher than the control. Moreover, the soil pot experiment showed that the combination of organic (fermented manure) and inorganic fertilizers made significant effects on the Zn and Cd-polluted soil remediation by S. alfredii. These effects varied, however, with the application of different proportions of N, P, K and organic matter. The Zn accumulation by S. alfredii reached the highest efficiency ability under the highest fertilizer mixing rate (N: 50 mg kg^-1, P: 40 mg kg^-1, K: 100 mg kg^-1, organic matter: 1%). Even more, S. alfredii showed the strongest ability to accumulate Cd with a lower fertilizer mixing rate (N: 25mg kg^-1, P: 20mg kg^-1, K: 50 mg kg^-1, organic matter: 0.5%).

     

Enhanced Cd extraction of oilseed rape (Brassica napus) by plant growth-promoting bacteria isolated from Cd hyperaccumulator Sedum alfredii Hance

Four plant growth-promoting bacteria (PGPB) were used as study materials, among them two heavy metal-tolerant rhizosphere strains SrN1 (Arthrobacter sp.) and SrN9 (Bacillus altitudinis) were isolated from rhizosphere soil, while two endophytic strains SaN1 (Bacillus megaterium) and SaMR12 (Sphingomonas) were identified from roots of the cadmium (Cd)/zinc (Zn) hyperaccumulator Sedum alfredii Hance. A pot experiment was carried out to investigate the effects of these PGPB on plant growth and Cd accumulation of oilseed rape (Brassica napus) plants grown on aged Cd-spiked soil. The results showed that the four PGPB significantly boosted oilseed rape shoot biomass production, improved soil and plant analyzer development (SPAD) value, enhanced Cd uptake of plant and Cd translocation to the leaves. By fluorescent in situ hybridization (FISH) and green fluorescent protein (GFP), we demonstrated the studied S. alfredii endophytic bacterium SaMR12 were able to colonize successfully in the B. napus roots. However, all four PGPB could increase seed Cd accumulation. Due to its potential to enhance Cd uptake by the plant and to restrict Cd accumulation in the seeds, SaMR12 was selected as the most promising microbial partner of B. napus when setting up a plant–microbe fortified remediation system.     

Effects of inoculation of a plant growth promoting rhizobacterium <Emphasis Type="Italic">Burkholderia</Emphasis> sp. D54 on plant growth and metal uptake by a hyperaccumulator <Emphasis Type="Italic">Sedum alfredii</Emphasis> Hance grown on multiple metal contaminated soil

Batch experiments were designed to characterize a multiple metal resistant bacterium Burkholderia sp. D54 isolated from metal contaminated soils in the Dabaoshan Mine in South China, and a follow-up experiment was conducted to investigate the effects of inoculating the isolate on plant growth and metal uptake by Sedum alfredii Hance grown on soils collected from a heavily contaminated paddy field in Daxing County, Guangxi Zhuang Automounous Region, Southwest China. Our experiments showed that strain D54 produced indole acetic acid (IAA), siderophores, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and solubilizing inorganic phosphate and solubilized insoluble metal bearing minerals. Bacterial inoculation significantly enhanced S. alfredii biomass production, and increased both shoot and root Cd concentration, but induced little variation in root/shoot Pb concentration and shoot Zn concentration. Despite this, the total shoot and root uptake of Cd, Pb and Zn in S. alfredii inoculated with D54 increased greatly compared to the non-inoculated controls. It was concluded that inoculation with strain D54 could help S. alfredii grow better on metal contaminated soils, produce more biomass, and remove more metals from soil, which implies improved efficiency of phytoextraction from metal contaminated soil. The knowledge gained from the present experiments constitutes an important advancement in understanding of the interaction between plant growth-promoting bacteria and hyperaccumulators with regard to plant ability to grow and remove the multiple heavy metals from soils.     

Metal accumulation and arbuscular mycorrhizal status in metallicolous and nonmetallicolous populations of <Emphasis Type="Italic">Pteris vittata</Emphasis> L. and <Emphasis Type="Italic">Sedum alfredii</Emphasis> Hance

Although Pteris vittata L. and Sedum alfredii Hance have been identified as an As hyperaccumulator and a Zn/Cd hyperaccumulator, respectively, for a few years, variations in metal accumulation among populations and their arbuscular mycorrhizal (AM) status have not been fully explored. Six populations of P. vittata and four populations of S. alfredii from southeast China were investigated. Up to 1,373 As, 680 Pb, 376 Zn, 4.8 Cd, 169 Cu mg kg⁻¹ in fronds of P. vittata and 358 As, 2,290 Pb, 23,403 Zn, 708 Cd, 342 Cu mg kg⁻¹ in shoots of S. alfredii were detected. Constitutive properties of As and Zn hyperaccumulation in metallicolous populations of P. vittata and S. alfredii, respectively, were confirmed. However, Cd hyperaccumulation in S. alfredii varied among populations. The two hyperaccumulators varied in efficiency in taking up other heavy metals. Different metal tolerance strategies adopted by the two hyperaccumulators varied among plant species and metal species. Low to moderate levels of AM colonization in P. vittata (4.2–12.8%) and S. alfredii (8.5–45.8%) were observed at uncontaminated and metal-contaminated sites. The relationship between metal concentrations and AM colonization in the two hyperacumulators was also examined. The abundance of AM fungal spores ranged from 16 to 190 spores per 25 g soil. Glomus microaggregatum, Glomus mosseae, Glomus brohultii and Glomus geosporum were the most common species associated with both P. vittata and S. alfredii. To our knowledge, this is the first report of AM fungal status in rhizosphere of P. vittata and S. alfredii.     

COLONIZATION AND MODULATION OF HOST GROWTH AND METAL UPTAKE BY ENDOPHYTIC BACTERIA OF SEDUM ALFREDII

Sedum alfredii Hance is a Zn and Cd co-hyperaccumulating plant species found in an old mining area in China. Four bacterial strains, Burkholderia sp. SaZR4, Burkholderia sp. SaMR10, Sphingomonas sp. SaMR12 and Variovorax sp. SaNR1, isolated from surface-sterilized S. alfredii plants were used to investigate their endophytic nature and root colonization patterns and effects on phytoextraction of Zn and Cd. Laser scanning confocal microscopy revealed that gfp-tagged SaZR4, SaMR12, and SaNR1 cells formed biofilms on roots and that SaZR4 and SaMR12 cells could invade root tissues. SaMR10 showed the lowest total population associated with S. alfredii and little effect on plant growth and phytoextraction. SaZR4 significantly promoted Zn-extraction but not Cd-extraction. SaMR12 and SaNR1 significantly promoted plant growth in substrates supplemented with Zn or Cd and phytoextraction of Zn and Cd. Together, this study have shown that the four native endophytic bacteria differently colonize the host plants and modulate metal uptake and growth of host plant, and that SaMR12 and SaNR1 strains are promising assistants of S. alfredii plants for phytoremediation of Zn/Cd-contaminated soil.     

Phytotreatment of Sewage Sludge Contaminated by Heavy Metals and Pahs by Co-Planting Sedum Alfredii and Alocasia Marorrhiza

High concentrations of heavy metals and organic pollutants in municipal sewage sludge are key factors limiting its use in agriculture. The objectives of this study were to decrease the heavy metal and polycyclic aromatic hydrocarbon concentrations in sewage sludge by phytotreatment and to determine, in a field experiment, whether co-planting is more effective than using a mono-crop of Sedum alfredii. Four treatments were used in the plot experiment: no sludge, no plants, S. alfredii and co-planting S. alfredii and Alocasia marorrhiza. The results showed that co-planting produced tubers and shoots of A. marorrhiza that were suitable as a safe animal feed and good organic K fertilizer, respectively. Co-planting was more effective than mono-planting at reducing concentrations of total Zn and diethylenetriaminepentaacetic acid (DTPA)-extractable Zn, Cd, and Cu in the sludge. Co-planting decreased the concentrations of DTPA-extractable heavy metals and benzo[a]pyrene (B[a]P) in the sludge significantly compared with the unplanted sludge. Decreases of 87, 75, 85, 31, and 64% were obtained for B[a]P and DTPA-extractable Zn, Cd, Cu, and Pb, respectively, compared with the fresh sludge. These results indicate that co-planting can reduce significantly the environmental risks associated with heavy metals and B[a]P in sewage sludge for further disposal.     

Phytoextraction of Metals and Rhizoremediation of PAHs in Co-Contaminated Soil by Co-Planting of Sedum Alfredii with Ryegrass (Lolium Perenne) or Castor (Ricinus Communis)

A pot experiment was conducted to investigate the potential for phytoextraction of heavy metals and rhizoremediation of polycyclic aromatic hydrocarbons (PAHs) in co-contaminated soil by co-planting a cadmium/zinc (Cd/Zn) hyperaccumulator and lead (Pb) accumulator Sedum alfredii with ryegrass (Lolium perenne) or castor (Ricinus communis). Co-planting with castor decreased the shoot biomass of S. alfredii as compared to that in monoculture. Cadmium concentration in S. alfredii shoot significantly decreased when grown with ryegrass or castor as compared to that in monoculture. However, no reduction of Zn or Pb concentration in S. alfredii shoot was detected in co-planting treatments. Total removal of either Cd, Zn, or Pb by plants was similar across S. alfredii monoculture or co-planting with ryegrass or castor, except enhanced Pb removal in S. alfredii and ryegrass co-planting treatment. Co-planting of S. alfredii with ryegrass or castor significantly enhanced the pyrene and anthracene dissipation as compared to that in the bare soil or S. alfredii monoculture. This appears to be due to the increased soil microbial population and activities in both co-planting treatments. Co-planting of S. alfredii with ryegrass or castor provides a promising strategy to mitigate both metal and PAH contaminants from co-contaminated soils.     

Cleaning up of heavy metals-polluted water by a terrestrial hyperaccumulator Sedum alfredii Hance

Sedum alfredii Hance is a terrestrial zinc/cadmium （Zn/Cd）-hyperaccumulating and lead （Pb）-accumulating plant. Previous studies on S. alfredii were mostly focused on its physiological mechanism of heavy metal uptake and the application in phytoextraction of metals from contaminated soils. In this study, we evaluated the application potential of S. alfredii in the cleanup of heavy metals from contaminated lake water. Our research revealed that changing pH in lake water would not make particular difference on the final accumulation amount of heavy metals, because the acidic water environment negatively affected plant growth compared with the neutral and alkaline environments, but was more conducive for heavy metal absorption and accumulation. In addition, S. alfredii showed an increase of approximately 2.2-fold in dry weight （DW） when cultured with lake water for 25 d. At the same time, it accumulated approximately 5.0 mg/kg DW of Cd and 41.4 mg/kg DW of Pb. The absorption of heavy metals was highly effective during the first 10 d of culture. Also, the quality of lake water was greatly improved after only 2-d cleanup by S. aifredii. In general, this hyperaccumulator exhibits great potential for application in the cleanup of heavy metals-polluted waters.     

Phytochelatin synthesis plays a similar role in shoots of the cadmium hyperaccumulator Sedum alfredii as in non‐resistant plants

Phytochelatin (PC) synthesis is considered necessary for Cd tolerance in non‐resistant plants, but roles for PCs in hyper‐accumulating species are currently unknown. In the present study, the relationship between PC synthesis and Cd accumulation was investigated in the Cd hyperaccumulator Sedum alfredii Hance. PCs were most abundant in leaves followed by stems, but hardly detected by the reversed‐phase high‐performance liquid chromatography (HPLC) in roots. Both PC synthesis and Cd accumulation were time‐dependent and a linear correlation between the two was established with about 1:15 PCs : Cd stoichiometry in leaves. PCs were found in the elution fractions, which were responsible for Cd peaks in the anion exchange chromatograph assay. About 5% of the total Cd was detected in these elution fractions as PCs were found. Most Cd was observed in the cell wall and intercellular space of leaf vascular cells. These results suggest that PCs do not detoxify Cd in roots of S. alfredii. However, like in non‐resistant plants, PCs might act as the major intracellular Cd detoxification mechanism in shoots of S. alfredii.     

Cadmium Sorption Characteristics of Soil Amendments and its Relationship with the Cadmium Uptake by Hyperaccumulator and Normal Plants in Amended Soils

In order to select appropriate amendments for cropping hyperaccumulator or normal plants on contaminated soils and establish the relationship between Cd sorption characteristics of soil amendments and their capacity to reduce Cd uptake by plants, batch sorption experiments with 11 different clay minerals and organic materials and a pot experiment with the same amendments were carried out. The pot experiment was conducted with Sedum alfredii and maize (Zea mays) in a co-cropping system. The results showed that the highest sorption amount was by montmorillonite at 40.82 mg/g, while mica was the lowest at only 1.83 mg/g. There was a significant negative correlation between the n value of Freundlich equation and Cd uptake by plants, and between the logarithm of the stability constant K of the Langmuir equation and plant uptake. Humic acids (HAs) and mushroom manure increased Cd uptake by S. alfredii, but not maize, thus they are suitable as soil amendments for the co-cropping S. alfredii and maize. The stability constant K in these cases was 0.14–0.16 L/mg and n values were 1.51–2.19. The alkaline zeolite and mica had the best fixation abilities and significantly decreased Cd uptake by the both plants, with K ≥ 1.49 L/mg and n ≥ 3.59.     

Efficiency of Repeated Phytoextraction of Cadmium and Zinc from an Agricultural Soil Contaminated with Sewage Sludge

Long-term application of sewage sludge resulted in soil cadmium (Cd) and zinc (Zn) contamination in a pot experiment conducted to phytoextract Cd/Zn repeatedly using Sedum plumbizincicola and Apium graceolens in monoculture or intercropping mode eight times. Shoot yields and soil physicochemical properties changed markedly with increasing number of remediation crops when the two plant species were intercropped compared with the unplanted control soil and the two monoculture treatments. Changes in soil microbial indices such as average well colour development, soil enzyme activity and soil microbial counts were also significantly affected by the growth of the remediation plants, especially intercropping with S. plumbizincicola and A. graveolens. The higher yields and amounts of Cd taken up indicated that intercropping of the hyperaccumulator and the vegetable species may be suitable for simultaneous agricultural production and soil remediation, with larger crop yields and higher phytoremediation efficiencies than under monoculture conditions.     

古老铅锌矿区生态型东南景天对锌耐性及超积累特性的研究

 植物长期生长在重金属污染的生境中,逐渐进化成不同的生态型。通过调查中国东南部古老Pb/zn矿和非矿山生境中的植物种群,发现生长在古老Pb／Zn矿的东南景天(Sedum alfredii Hance)是一种新的Zn超积累植物。在自然和控制条件下,古老Pb／Zn矿生态型比非矿山生态型植株的茎粗、叶片大、植株高。在矿山土壤Zn有效含量为105.5～325.4mg·kg-1时,矿山生态型东南景天植株地上部Zn含量为4134～5000mg·kg-1;当营养液中Zn浓度为1223.6μmol时,其Zn含量高达2％。在相同Zn浓度下,矿山生态型地上部Zn含量比非矿山生态型高30倍左右。两种生态型体内Zn分布也不同,古老铅锌矿山生态型的不同器官中Zn含量以茎>叶片>根系,而非矿山生态型则以根系>茎>叶片。古老铅锌矿山生态型地上部积累的Zn占植株总积累量的90％以上,其中叶片和茎分别占41.66％±5.46％和54.75％±5.87％;非矿山生态型各器官中积累的Zn远远低于古老铅锌矿山生态型,各器官中积累的Zn以茎>根系>叶片。本研究表明,这两种生态型东南景天的发现,为今后探讨植物耐高Zn胁迫和超积累Zn的微进化过程提供了非常有价值的材料,也为Zn污染土壤的植物修复提供了一种很有潜力的候选材料。     

Root foraging for zinc and cadmium requirement in the Zn/Cd hyperaccumulator plant Sedum alfredii

Positive root response to metals may enhance metal accumulation for greater requirement in hyperaccumulators. The effects of spatially heterogeneous Zn/Cd addition on root allocation, metal accumulation, and growth of the Zn/Cd hyperaccumulator Sedum alfredii were assessed in a pot experiment. Young shoots of S. alfredii were grown with or without supplied Zn/Cd. Two concentrations were used of each metal, and each metal concentration had one homogeneous and two heterogeneous treatments. Growth increased by 1.6–3.2 times with the increasing overall dose of Zn/Cd addition, and shoot biomass was positively correlated with shoot Zn/Cd concentration (P?<?0.001). In all heterogeneous treatments, the plants consistently allocated approximately 90% of root biomass to the metal-enriched patches, and shoot Zn/Cd contents were greater than or similar to those in the homogeneous treatment at each metal concentration. Plants in the control treatment showed symptoms of Zn deficiency, although their shoots had Zn concentrations 100-fold higher than the critical deficiency value for most plants. We conclude that S. alfredii has evolved root foraging mechanisms associated with its greater requirements for Zn/Cd. These results could have important implications both for phytoremediation and for investigation of positive role of Cd in higher plants.     

Effect of Pb on leaf antioxidant enzyme activities and ultrastructure of the two ecotypes of <Emphasis Type="Italic">Sedum alfredii</Emphasis> Hance

Hydroponic experiments were conducted to study the effect of Pb on growth, leaf antioxidant enzyme activities, and ultrastructure of the accumulating ecotype (AE) and non-accumulating ecotype (NAE) of Sedum alfredii Hance. AE was found to be more tolerant to excessive Pb levels in growth medium. Concentrations of Pb in the shoots of the AE were 1.98 times higher than those in the NAE when 0.2 mM Pb was supplied. Both chlorophyll a and b did not decrease significantly in AE plants after Pb treatment, while a significant decrease was noted in chlorophyll a and b of NAE plants treated with Pb concentrations greater than 0.05 mM. The results showed that activities of superoxide dismutase (SOD) and catalase (CAT) were elevated in the leaves of AE under Pb stress. However in NAE, Pb-caused enhancement was noticed only in the activity of SOD while activity of CAT was declined as compared to the control plants. With increased Pb level, malondialdehyde (MDA) content increased significantly in both ecotypes of S. alfredii, indicating that Pb toxicity led to lipid peroxidation and membrane damage, but MDA content in the leaves of NAE was always higher than in AE plants. The ultrastructural analysis of the spongy mesophyll cells revealed that excessive Pb concentrations obviously damaged the cell membrane, chloroplasts, and mitochondria of both the ecotypes but damage was more severe in NAE. Although growth, leaf physiology, and ultrastructure of both the ecotypes were affected by Pb treatment, deleterious effects were more pronounced in NAE. This text was submitted by the authors in English.     

<i>VvAGAMOUS</i> Affect Development of Four Different Grape Species Ovary

Grape pistil has an important influence on fruit size and quality. However, there were few studies on grape ovary, and the development process of the ovary is still unclear. Therefore, in this paper, four different grape varieties with different lengths of small inflorescences, namely ‘Musct Hambourg’ grape (Vitis vinifera), ‘Concord’ grape (Vitis labrusca), ‘ShanPuTao’ grape (Vitis amurensis) and ‘GongNiang2Hao’ grape (Vitis amurensis × Vitis vinifera) were used as test materials. Four varieties ovary were significant differences by means of stereomicroscope, paraffin section. The expression of ovary determining gene VvAGAMOUS (VvAG) and its development related genes VvCRABS CLAW (VvCRC) andVvAGAMOUS-LIKE 11 (VvAGL11) with similar functions during the development of different grape varieties were preliminarily explored using fluorescence quantitative test. The relationship between VvAG and VvCRC, VvAG and VvAGL11 were analyzed using Y1H assay. Our results showed that there were obvious abdominal sutures on the surface of expect for ‘Musct Hambourg’ grape, and existing poly carpels. The ovary development of ‘ShanPuTao’ and ‘GongNiang2Hao’ grape was completed when the inflorescence length was less than 1 cm, while the ‘Concord’ and ‘Musct Hambourg’ grape were fully developed when the length of inflorescence was 3–4 and 4–5 cm, respectively. VvAG and VvCRC began to express in large quantities after the formation of stamen primordia, while VvAGL11 during the forming of ovule primordia. Therefore, VvAG and VvCRC mainly regulated the development of stamens and carpels and also promote the development of ovules, while VvAGL11 major regulated the development of ovules. The promoters of VvCRC and VvAGL11 were bound by VvAG. This study provides an important theoretical basis for further research on the molecular mechanism of grape ovary development.     

Dynamics of zinc uptake and accumulation in the hyperaccumulating and non-hyperaccumulating ecotypes of Sedum alfredii Hance

Sedum alfredii Hance has been identified as a Zn-hyperaccumulating plant species native to China. The characteristics of Zn uptake and accumulation in the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii were investigated under nutrient solution and soil culture conditions. The growth of HE was normal up to 1000 μM Zn in nutrient solution, and 1600 mg Zn kg⁻¹ soil in a Zn-amended soil. Growth of the NHE was inhibited at Zn levels ≥250 μM in nutrient solution. Zinc concentrations in the leaves and stems increased with increasing Zn supply levels, peaking at 500 and 250 μM Zn in nutrient solution for the HE and the NHE, respectively, and then gradually decreased or leveled off with further increase in solution Zn. Minimal increases in root Zn were noted at Zn levels up to 50 μM; root Zn sharply increased at higher Zn supply. The maximum Zn concentration in the shoots of the HE reached 20,000 and 29,000 mg kg⁻¹ in the nutrient solution and soil experiments, respectively, approximately 20 times greater than those of the NHE. Root Zn concentrations were higher in the NHE than in the HE when plants were grown at Zn levels ≥50 μM. The time-course of Zn uptake and accumulation exhibited a hyperbolic saturation curve: a rapid linear increase during the first 6 days in the long-term and 60 min in the short-term studies; followed by a slower increase or leveling off with time. More than 80% of Zn accumulated in the shoots of the HE at half time (day 16) of the long-term uptake in 500 μM Zn, and also at half time (120 min) of the short-term uptake in 10 μM ⁶⁵Zn²⁺. These results indicate that Zn uptake and accumulation in the shoots of S. alfredii exhibited a down-regulation by internal Zn accumulated in roots or leaves under both nutrient solution and soil conditions. An altered Zn transport system and increased metal sequestration capacity in the shoot tissues, especially in the stems, may be the factors that allow increased Zn accumulation in the hyperaccumulating ecotype of S. alfredii. Section Editor: F. J. Zhao     

镉对超积累和非超积累生态型东南景天内生细菌多样性的影响

重金属胁迫对植物内生细菌群落结构的影响在很大程度上是未知的,目前也很少有研究超积累植物内生细菌的群落结构与多样性对根际土壤中重金属的响应。【目的】探索在不同镉污染水平下,超积累(HE)和非超积累生态型(NHE)东南景天的根系、茎和叶片中内生细菌的群落结构与多样性的变化及其差异性,试图从植物-内生菌之间的相互关系的角度补充解释2种生态型东南景天对有效态镉忍耐和积累能力的差异。【方法】采用Illumina新一代测序方法分析了在不同Cd~(2+)浓度土壤上生长的2种生态型东南景天根、茎和叶中的内生细菌群落结构。【结果】高浓度Cd~(2+)抑制NHE东南景天的生长,内生细菌的丰富度和多样性也降低;然而,高浓度Cd~(2+)促进HE东南景天的生长,茎和根系内生细菌的丰富度增加。在3种土壤上,2种生态型东南景天叶片、茎和根系内生细菌均以变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria)占优势。随着土壤中Cd~(2+)浓度的增加,HE东南景天叶片中Gammaproteobacteria纲、Negativicutes纲和Clostridia纲的相对丰度显著增加,茎中Alphaproteobacteria纲的相对丰度显著增加,Clostridia纲的相对丰度显著减少;NHE东南景天叶片中Alphaproteobacteria纲、Gammaproteobacteria纲和Clostridia纲的相对丰度没有显著变化,茎中Negativicutes纲的相对丰度显著减少,根系中Betaproteobacteria纲和Clostridia纲的相对丰度显著减少,Negativicutes纲却显著增加。在高Cd~(2+)污染土壤(50mg/kg)上,HE东南景天叶片中Sphingomonas属和茎中Veillonella属的相对丰度均大于NHE,且HE东南景天根系内生细菌的第一、第二、第三优势菌Veillonella、Sphingomonas、Prevotella属细菌均没有出现在NHE东南景天根系。【结论】土壤Cd~(2+)污染水平对2种生态型东南景天叶、茎、根中的内生菌群落结构有显著影响。