Effects of EDTA on solubility of cadmium, zinc, and lead and their uptake by rainbow pink and vetiver grass

Rainbow pink (Dianthus chinensis), a potential phytoextraction plant, can accumulate high concentrations of Cd from contaminated soils. Vetiver grass (Vetiver zizanioides) has strong and long root tissues and is a potential phytostabilization plant since it can tolerate and grow well in soils contaminated with multiple heavy metals. Soil was moderately artificially contaminated by cadmium (20 mg/kg), zinc (500 mg/kg), and lead (1000 mg/kg) in pot experiments. Three concentrations of Na2-EDTA solution (0, 5, and 10 mmol/kg soil) were added to the contaminated soils to study the influence of EDTA solution on phytoextraction by rainbow pink or phytostabilization by vetiver grass. The results showed that the concentrations of Cd, Zn, and Pb in a soil solution of rainbow pink significantly increased following the addition of EDTA (p < 0.05). The concentrations of Cd and Pb in the shoots of rainbow pink also significantly increased after EDTA solution was applied (p < 0.05), but the increase for Zn was insignificant. EDTA treatment significantly increased the total uptake of Pb in the shoot, over that obtained with the control treatment (p < 0.001), but it did not significantly increase the total uptake of Cd and Zn. The concentrations of Zn and Pb in the shoots of rainbow pink are significantly correlated with those in the soil solution, but no relationship exists with concentrations in vetiver grass. The toxicity of highly contaminating metals did not affect the growth of vetiver grass, which was found to grow very well in this study. Results of this study indicate that rainbow pink can be considered to be a potential phytoextraction plant for removing Cd or Zn from metal-contaminated soils, and that vetiver grass can be regarded as a potential phytostabilization plant that can be grown in a site contaminated with multiple heavy metals.     

A comparative study of cadmium phytoextraction by accumulator and weed species

Phytoextraction has shown great potential as an alternative technique for the remediation of metal contaminated soils. The objective of this study was to investigate cadmium (Cd) phytoextraction ability of high biomass producing weeds in comparison to indicator plant species. The pot study conducted with 10 to 200 mg Cd kg(-1) soil indicated that Ipomoea carnea was more effective in removing Cd from soil than Brassica juncea. Among the five species, B. juncea accumulated maximum Cd, but I. carnea followed by Dhatura innoxia and Phragmytes karka were the most suitable species for phytoextraction of cadmium from soil, if the whole plant or above ground biomass is harvested. In the relatively short time of this experiment, I. carnea produced more than 5 times more biomass in comparison to B. juncea. There were significant differences (p < 0.05) between the shoot length and shoot mass of control and treated plants.     

Silicon-mediated enhancement of cadmium tolerance in maize (Zea mays L.) grown in cadmium contaminated soil

Pot experiments were performed to study the alleviative effects of exogenous silicon (Si) on cadmium (Cd) phytotoxicity in maize grown in an acid soil experimentally contaminated with Cd. Five treatments were investigated in the first trial consisting of a control (neither Cd nor Si added), Cd added at 20 or 40 mg kg(-1) Cd without or with Si added at 400 mg kg(-1) Si. A following-up trial was conducted with almost the same treatments as in the first trial except that Si was incorporated at 50 mg kg(-1) Si. The results showed that Cd treatment significantly decreased shoot and root dry weight, while addition of Si at both levels significantly enhanced biomass. Addition of Si at 400 mg kg(-1) Si significantly increased soil pH but decreased soil Cd availability, thus reducing Cd concentration in the shoots and roots and total Cd in the shoots. Moreover, more Cd was found to be in the form of specific adsorbed or Fe-Mn oxides-bound fraction in the Si-amended soil. In contrast, soil pH, available Cd and Cd forms were unaffected by addition of Si at 50 mg kg(-1) Si, but shoot Cd concentration in the Si-amended Cd treatments significantly decreased at both Cd levels used compared to the non-Si-amended Cd treatments. Total Cd in the shoots and roots was considerably and significantly higher in the Si-amended Cd treatments than in the non-Si-amended Cd treatments. The xylem sap significantly increased but Cd concentration in the xylem sap significantly decreased in the Si-amended Cd treatments compared with the non-Si-amended Cd treatments irrespective of Cd and Si levels used. The results suggest that Si-enhanced tolerance to Cd can be attributed not only to Cd immobilization caused by silicate-induced pH rise in the soils but also to Si-mediated detoxification of Cd in the plants.     

The role of root hairs in cadmium acquisition by barley

The role of root hairs in Cd acquisition from soil was investigated in three pot experiments using a root hairless mutant (bald root barley, brb) and its wild-type (WT) cultivar of barley (Hordeum vulgare). brb had significantly lower concentrations and lower total amounts of Cd in shoots than WT. The Cd uptake efficiency based on total root length was 8-45% lower in brb than in WT. The difference between brb and WT increased with increasing extractable Cd in soil under the experimental conditions used. Additions of phosphate to soil decreased Cd extractability. Both soil and foliar additions of phosphate decreased root length, and root hair formation in WT. These effects resulted in decreased Cd uptake with increasing P supply. Cd uptake in WT correlated significantly with root length, root hair length and density, and soil extractable Cd. Root hairs contribute significantly to Cd uptake by barley.     

Growth and trace metal accumulation of two Salix clones on sediment-derived soils with increasing contamination levels

The growth and metal uptake of two willow clones (Salix fragilis 'Belgisch Rood' and Salix viminalis 'Aage') was evaluated in a greenhouse pot experiment with six sediment-derived soils with increasing field Cd levels (0.9-41.4 mg kg-1). Metal concentrations of eight elements were measured in roots, stems and leaves and correlated to total and soil water metal concentrations. Dry weight root biomass, number of leaves and shoot length were measured to identify eventual negative responses of the trees. No growth inhibition was observed for both clones for any of the treatments (max. 41.4 mg kg-1 Cd, 1914 mg kg-1 Cr, 2422 mg kg-1 Zn, 655 mg kg-1 Pb), allowing their use for phytoextraction on a broad range of contaminated sediments. However, dry weight root biomass and total shoot length were significantly lower for S. viminalis compared to S. fragilis for all treatments. Willow foliar Cd concentrations were strongly correlated with soil and soil water Cd concentrations. Both clones exhibited high accumulation levels of Cd and Zn in aboveground plant parts, making them suitable subjects for phytoextraction research. Cu, Cr, Pb, Fe, Mn and Ni were found mainly in the roots. Bioconcentration factors of Cd and Zn in the leaves were highest for the treatments with the lowest soil Cd and Zn concentration.     

The EDTA effect on phytoextraction of single and combined metals-contaminated soils using rainbow pink (Dianthus chinensis)

Rainbow pink (Dianthus chinensis), a potential phytoextraction plant, can accumulate high concentrations of Cd from metal-contaminated soils. The soils used in this study were artificially added with different metals including (1) CK: original soil, (2) Cd-treated soil: 10 mg Cd kg(-1), (3) Zn-treated soil: 100 mg Zn kg(-1), (4) Pb-treated soil: 1000 mg Pb kg(-1), (5) Cd-Zn-treated soil: 10 mg Cd kg(-1) and 100 mg Zn kg(-1), (6) Cd-Pb-treated soil: 10 mg Cd kg(-1) and 1000 mg Pb kg(-1), (7) Zn-Pb-treated soil: 100 mg Zn kg(-1) and 1000 mg Pb kg(-1), and (8) Cd-Zn-Pb-treated soil: 10 mg Cd kg(-1), 100 mg Zn kg(-1), and 1000 mg Pb kg(-1). Three concentrations of 2Na-EDTA solutions (0 (control), 2, and 5 mmol kg(-1) soil) were added to the different metals-treated soils to study the influence of applied EDTA on single and combined metals-contaminated soils phytoextraction using rainbow pink. The results showed that the Cd, Zn, Pb, Fe, or Mn concentrations in different metals-treated soil solutions significantly increased after applying 5 mmol EDTA kg(-1) (p<0.05). The metal concentrations in different metals-treated soils extracted by deionized water also significantly increased after applying 5 mmol EDTA kg(-1) (p<0.05). Because of the high extraction capacity of both 0.005 M DTPA (pH 5.3) and 0.05 M EDTA (pH 7.0), applying EDTA did not significantly increase the Cd, Zn, or Pb concentration in both extracts for most of the treatments. Applying EDTA solutions can significantly increase the Cd and Pb concentrations in the shoots of rainbow pink (p<0.05). However, this was not statistically significant for Zn because of the low Zn concentration added into the contaminated soils. The results from this study indicate that applying 5 mmol EDTA kg(-1) can significantly increase the Cd, Zn, or Pb concentrations both in the soil solution or extracted using deionized water in single or combined metals-contaminated soils, thus increasing the accumulated metals concentrations in rainbow pink shoots. The proposed method worked especially well for Pb (p<0.05). The application of 2 mmol EDTA kg(-1) might too low to enhance the phytoextraction effect when used in silty clay soils.     

Enhanced phytoextraction of Pb and other metals from artificially contaminated soils through the combined application of EDTA and EDDS

Chemically enhanced phytoextraction is achieved by the application of chelates to soils. Using pot experiments, the effect of the combined application of EDTA and EDDS on the uptake of Cu, Pb, Zn and Cd by Zea mays L. was studied. Among the tested application ratios of 1:1, 1:2, and 2:1 (EDTA/EDDS), 2:1 of EDTA:EDDS was the most efficient ratio for increasing the concentrations of Cu, Pb, Zn and Cd in the shoots. The combined application of 3.33 mmol kg(-1) soil of EDTA+1.67 mmol kg(-1) soil of EDDS produced 650 mg kg(-1) of Pb in the shoots, which was 2.4 and 5.9 times the concentration of Pb in the shoots treated with 5 mmol kg(-1) of EDTA and EDDS alone, respectively. The total phytoextraction of Pb reached 1710 microg kg(-1) soil, which was 2.1 and 6.1 times the total Pb from 5 mmol kg(-1) EDTA and EDDS alone, respectively. The combined application of EDTA and EDDS also significantly increased the translocation of Pb from the roots to the shoots. The mechanism of enhancing the phytoextraction of Pb by the combined application of EDTA+EDDS did not involve a change in the pH of the soil. The increase in the phytoextraction of Pb by the shoots of Z. mays L. was more pronounced than the increase of Pb in the soil solution with the combined application of EDTA and EDDS. It was thought that the major role of EDDS might be to increase the uptake and translocation of Pb from the roots to the shoots of plants.     

Genotypic differences in effects of cadmium exposure on plant growth and contents of cadmium and elements in 14 cultivars of bai cai

Fourteen cultivars of bai cai (Brassica campestris L. ssp. chinensis var. communis) were grown in the nutrient solutions containing 0-0.5 microg mL(-1) of cadmium (Cd) to investigate genotypic differences in the effects of Cd exposure on the plant growth and uptake and distribution of Cd in bai cai plants. The Cd exposure significantly reduced the dry and fresh weights of roots and shoots, the dry weight ratio of shoot/root (S/R), total biomass, and chlorophyll content (SPAD value). Cd concentrations in bai cai ranged from 13.3 to 74.9 microg g(-1) DW in shoots and from 163.1 to 574.7 microg g(-1) DW in roots under Cd exposure, respectively. The considerable genotypic differences of Cd concentrations and accumulations in both shoots and roots were observed among 14 bai cai cultivars. Moreover, Cd mainly accumulated in the roots. Cd also caused the changes of uptake and distribution of nutrients in bai cai and under the influence of cadmium, the concentration of potassium (K) decreased in shoot and increased in root. However, the concentrations of magnesium (Mg), phosphorus (P), manganese (Mn), boron (B), and iron (Fe) increased in shoots and decreased in roots. In addition, Cd exposure resulted in an increase in calcium (Ca), sulphur (S), and zinc (Zn) concentrations in both shoots and roots but had no significant effects on the whole uptake of the examined mineral nutrients except for S.     

The use of NTA and EDDS for enhanced phytoextraction of metals from a multiply contaminated soil by Brassica carinata

The potential of nine different species to grow in the presence of metals (As, Cd, Cu, Pb and Zn) and to accumulate them in the shoots was assessed for each metal separately by germination and root length tests, and successively by hydroponic experiments. Of the nine species tested, Brassica carinata was the species that accumulated the highest amounts of metals in shoots without suffering a significant biomass reduction. To further evaluate the potential of B. carinata for chelant-enhanced phytoextraction of a natural, multiply metal-polluted soil (As, Cd, Cu, Pb and Zn), both hydroponic and pot experiments were carried out with nitrilotriacetic acid (NTA) or (S,S)-ethylenediamine disuccinic acid (EDDS) as complexing agents. The hydroponic study with solutions containing the five metals together showed that accumulation of Cd, Cu, Pb and Zn in shoots was higher following EDDS addition compared to NTA. EDDS was more effective than NTA in desorbing Cu, Pb and Zn from the soil, whereas As and Cd were poorly extracted. B. carinata plants were grown for 4 weeks in the multiply metal-contaminated soil and then the soil was amended with 5 mmol kg(-1) NTA or EDDS. All plants were harvested 1 week after amendment. In comparison to NTA, EDDS was more effective in enhancing the concentrations of Cu, Pb and Zn in B. carinata shoots (2- to 4-fold increase compared to the control). One week after chelant addition, the DTPA-extractable metal concentrations in the polluted soil were lower in the EDDS treatment in comparison with the NTA amendment. Even though B. carinata showed a reduced growth and a relatively low metal uptake, it demonstrated the ability to survive and tolerate the presence of more metals simultaneously.     

Assessment of the phytoextraction potential of high biomass crop plants

A hydroponic screening method was used to identify high biomass crop plants with the ability to accumulate metals. Highest values of shoot accumulation were found in maize cv. Ranchero, rapeseed cv. Karat, and cardoon cv. Peralta for Pb (18 753 mg kg(-1)), Zn (10 916 mg kg(-1)), and Cd (242 mg kg(-1)), respectively. Subsequently, we tested the potential of these three cultivars for the phytoextraction of a metal spiked compost, finding out that, in cardoon and maize plants, increasing Zn and Cd concentrations led to lower values of root and shoot DW. By contrast, rapeseed shoot growth was not significantly affected by Cd concentration. Finally, a metal polluted soil was used to check these cultivars' phytoextraction capacity. Although the soil was phytotoxic enough to prevent the growth of cardoon and rapeseed plants, maize plants phytoextracted 3.7 mg Zn pot(-1). We concluded that the phytoextraction performance of cultivars varies depending on the screening method used.     

Nitrilotriacetate- and citric acid-assisted phytoextraction of cadmium by Indian mustard (Brassica juncea (L.) Czernj, Brassicaceae)

In a pot experiment the effects of nitrilotriacetate (NTA) and citric acid applications on Cd extractibility from soil as well as on its uptake and accumulation by Indian mustard (Brassica juncea) were investigated. Plants were grown in a sandy soil with added CdS at four levels ranging from 50 to 200 mg Cd kg(-1) soil. After 30 days of growth, pots were amended with NTA or citric acid at 10 and 20 mmol kg(-1). Control pots were not treated with chelates. Harvest of plants was performed immediately before and one week after chelate addition. Soil water-, NH(4)NO(3)- and EDTA-extractable Cd fractions increased constantly with both increasing soil metal application and chelate concentration. Shoot dry weights did not suffer significant reductions with increasing Cd addition to the soil except for both NTA treatments in which at 200 mg Cd kg(-1) a 30% decrease in dry matter was observed. Generally, following NTA and citric acid amendments, Cd concentration in shoots increased with soil Cd level. However, due to Cd toxicity, at the highest metal application rate both NTA treatments lowered Cd concentration in the above-ground parts. Compared to the control, at 10 mmol kg(-1) citric acid did not change Cd concentration in shoots, whereas NTA-treated plants showed an about 2-fold increase. The addition of chelates at 20 mmol kg(-1) further enhanced Cd concentration in shoots up to 718 and 560 microg g(-1) dry weight in the NTA and citrate treatments, respectively.     

New insights into the sorption mechanism of cadmium on red mud

Effectiveness and mechanism of cadmium (Cd) sorption on original, acidified and ball milling nano-particle red muds were investigated using batch sorption experiments, sequential extraction analysis and X-ray absorption near edge structure (XANES) spectroscopy. The maximum sorption capacity of Cd was 0.16, 0.19, and 0.21 mol/kg for the original, acidified, and nano-particle red muds at pH 6.5, respectively. Both acidification and ball-milling treatments significantly enhanced Cd sorption and facilitated transformation of Cd into less extractable fractions. The Cd L_III-edge XANES analysis indicated the formation of inner-sphere complexes of Cd similar to XCdOH (X represents surface groups on red mud) on the red mud surfaces although outer-sphere complexes of Cd were the primary species. This work shed light on the potential application of red mud to remediate Cd-contaminated soils and illustrated the promising tool of XANES spectroscopy for speciation of multicomponent systems of environmental relevance.     

Fate of cadmium in Elodea canadensis

Elodea canadensis is a submersed macrophytes, widely distributed in stormwater treatment ponds and able to remove heavy metals from water. This study examines the Cd uptake, translocation, and efflux patterns in Elodea. Several experiments were set up in a climate chamber. To study the root and shoot Cd uptake, living and dead roots and shoots were treated with (109)Cd in one- and two-compartment systems. Furthermore, to examine Cd translocation and distribution, either roots or shoots were treated with (109)Cd. Finally, the efflux of Cd from roots and shoots, respectively, to the external solution was studied after loading whole plants with (109)Cd. Results from the two compartment studies show that Cd is accumulated via direct uptake by both roots and shoots of Elodea. The Cd accumulation proved not to be metabolically dependent in Elodea, and the apoplastic uptake in particular was decreased by Cd pretreatment. In one week, up to 23% of the root uptake was translocated to the shoots, while about 2% of the Cd accumulated by shoots was translocated to the roots. Thus, slight dispersion of Cd is possible, while metal immobilization will not be directly mediated via the Elodea plant. The efflux experiment proved that both shoots of dead plants and roots of living plants had a faster efflux than did shoots of living plants. This information is relevant for an understanding of the fate of Cd in stormwater treatment ponds with Elodea.     

Enhanced phytoextraction of an agricultural Cr- and Pb-contaminated soil by bioaugmentation with siderophore-producing bacteria

Bioaugmentation-assisted phytoextraction may enhance the phytoextraction efficiency thanks to larger metal mobilization by microbial metabolites. Green fluorescent protein-tagged cells of Pseudomonas aeruginosa, Pseudomonas fluorescens or Ralstonia metallidurans, able to produce siderophores, were inoculated in an agricultural soil containing Cr (488 mg kg(-1)) and Pb (382 mg kg(-1)) and maize was cultivated. Bacteria were inoculated as free or immobilized cells in Ca-alginate beads, with skim milk in the aim at improving both the bacterial survival and the in situ siderophore production. Skim milk addition increased inoculated Pseudomonads concentration in soil. Soil inoculation with free cells of R. metallidurans supplied with skim milk increased Cr accumulation in maize shoots by a factor of 5.2 and inoculation with immobilized P. aeruginosa cells supplied with skim milk increased Cr and Pb uptake by maize shoots by a factor of 5.4 and 3.8, respectively. However total metal taken up by the whole plant decreases almost always with bioaugmentation. Translocation factor also increased with P. aeruginosa or R. metallidurans by a factor of 6 up to 7. Inoculated bacteria concentration in soil was correlated with metals in the exchangeable fraction. Cr and Pb concentrations in the exchangeable fraction were correlated with metal contents in shoots or roots. Our results suggest that bioaugmentation-assisted phytoextraction is a relevant method in the aim at increasing the phytoextraction rate which usually limits the use of phytoremediation technologies.     

Enhancing phytoextraction of Cd by combining poplar (clone “I-214”) with Pseudomonas fluorescens and microbial consortia

The plant–microorganism combinations may contribute to the success of phytoextraction of heavy metal-polluted soil. The purpose of this study was to investigate the effects of cadmium (Cd) soil concentration on selected physiological parameters of the poplar clone “I-214” inoculated at root level with a strain (BT4) of Pseudomonas fluorescens and a commercial product based on microbial consortia (Micosat F Fito®). Plants were subjected to Cd treatment of 40 mg kg^?1 in greenhouse. The effects of plant–microbe interactions, plant growth, leaf physiology, and microbial activity were periodically monitored. Metal concentration and translocation factors in plant tissues proved enhanced Cd uptake in roots of plants inoculated with P. fluorescens and transfer to shoots in plants inoculated with Micosat F Fito®, suggesting a promising strategy for using microbes in support of Cd uptake. Plant–microbe integration increased total removal of Cd, without interfering with plant growth, while improving the photosynthetic capacity. Two major mechanisms of metal phytoextraction inducted by microbial inoculation may be suggested: improved Cd accumulation in roots inoculated with P. fluorescens, implying phytostabilization prospective and high Cd transfer to shoots of inoculated plants, outlining enhanced metal translocation.     

Ecotoxicological effects of cadmium on three ornamental plants

Ecotoxicological effects of cadmium (Cd) on three ornamental plants African marigold (Tagetes erecta), scarlet sage (Salvia splendens) and sweet hibiscus (Abelmoschus manihot) were investigated. Seeds of these plants were exposed to five different concentrations of Cd (0-50 mgl(-1)). Ecotoxicological indexes based on inhibition rate (IC) of seed germination, root and shoot elongation, biomass (fresh weight and dry weight), as well as IC50 (Cd concentration when 50% plants show inhibition) and tolerance indexes (the ratio of maximum root length in an experimental group to that in a control group) were determined. The results indicated that Cd had little effects (p>0.05) on seed germination of the three plants and shoot elongation of scarlet sage (S. splendens). Cadmium had significant (p<0.05) inhibitory effects on root elongation of the three plants and shoot elongation of African marigold (T. erecta). The fresh weight biomass of scarlet sage (S. splendens) was most sensitive to Cd, while that of sweet hibiscus (A. manihot) was least sensitive. On a dry weight basis, African marigold (T. erecta) was the least sensitive, and scarlet sage (S. splendens) was the most sensitive to Cd. Based on IC50 of seed germination, sweet hibiscus (A. manihot) was the most insensitive plant with an IC50 value as high as 428.0 gl(-1). According to Cd-tolerance indexes under the same Cd concentration, sweet hibiscus (A. manihot) was the most tolerant plant whereas scarlet sage (S. splendens) was the most sensitive one.     

Phosphorus and cadmium interactions in Kandelia obovata (S. L.) in relation to cadmium tolerance

This study focused on the cadmium (Cd) tolerance of mangroves with application of phosphate (P) in order to explore whether exogenous P can alleviate Cd stress on these intertidal species. Kandelia obovata (S. L.) seedlings were cultivated in rhizoboxes under different levels of Cd and P concentrations. The speciation distributions of Cd in the rhizosphere and non-rhizosphere sediments were examined by sequential extraction procedures; organic acid in plant tissues and soil solution was measured by high-performance liquid chromatography; Cd and P accumulation in the plants was also determined. Results showed that considerable differences existed in Cd speciation distributions between rhizosphere and non-rhizosphere sediments. Root activity influenced the dynamics of Cd, P application increased the organic acid content in root tissues, P also increased Cd accumulation in roots whilst lowering Cd translocation from root to the above-ground tissues, and a significant positive correlation was found between Cd and P in roots (r?=?0.905). It is postulated that Cd detoxification of K. obovata (S. L.) is associated with higher Cd immobilization in the presence of higher P and organic acid contents in root tissue.     

Trichoderma atroviride F6 improves phytoextraction efficiency of mustard (Brassica juncea (L.) Coss. var. foliosa Bailey) in Cd, Ni contaminated soils

Trichoderma atroviride F6, isolated from decaying feather and resistant to 100 mg l(-1) Cd2+ and 250 mg l(-1) Ni2+, was applied for rhizoremediation of Cd, Ni and Cd-Ni combination contaminated soils through association with Brassica juncea (L.) Coss. var. foliosa. The strain significantly alleviated the cellular toxicity of cadmium and nickel to plants. Inoculation of B. juncea (L.) Coss. var. foliosa with T. atroviride F6 resulted a 110%, 40% and 170% increase in fresh weight in Cd, Ni and Cd-Ni contaminated soils, respectively (P<0.05). The translocation factors and metal bioconcentration factors calculated for the inoculated plant were increased compared to the noninoculated plants. The results indicated that the efficiency of phytoextraction for B. juncea (L.) Coss. var. foliosa enhanced after inoculating with T. atroviride F6. The fungal treated plants grown in Cd-Ni combination contaminated soils showed higher phytoextraction efficiency than those in Cd or Ni contaminated soils. Thus, it is suggested that the fungus T. atroviride F6 endowed with organic-degrading capabilities could be exploited for fungi-assisted phytoremediation of mixed organic-metal contaminated soils.     

Phytoextraction of cadmium by rice (Oryza sativa L.), soybean (Glycine max (L.) Merr.), and maize (Zea mays L.)

Selecting a phytoextraction plant with high Cd-accumulating ability based on the plant's compatibility with mechanized cultivation techniques may yield more immediately practical results than selection based on high tolerance to Cd. Rice (Oryza sativa L., cv. Nipponbare and Milyang 23), soybean (Glycine max [L.] Merr., cv. Enrei and Suzuyutaka), and maize (Zea mays L., cv. Gold Dent) were grown on one Andosol and two Fluvisols with low concentration of Cd contamination ranging from 0.83 to 4.29 mg Cd kg(-1), during 60 days in pots (550 mL) placed in a greenhouse. Shoot Cd uptake was as follows: Gold Dent相似文献   

Role of microbial inoculation and chitosan in phytoextraction of Cu, Zn, Pb and Cd by Elsholtzia splendens--a field case

A field experiment was carried out to study the effect of microbial inoculation on heavy metal phytoextraction by Elsholtzia splendens and whether chitosan could have a synergistic effect with the microbial inocula. The microbial inocula consisted of a consortium of arbuscular mycorrhizal fungi and two Penicillium fungi. Three treatments were included: the control, inoculation with microbial inocula, and the inoculation combined with chitosan. Microbial inoculation increased plant biomass especially shoot dry weight, enhanced shoot Cu, Zn and Pb concentrations but did not affect Cd, leading to higher shoot Cu, Zn, Pb and Cd uptake. Compared with microbial inoculation alone, chitosan application did not affect plant growth but increased shoot Zn, Pb and Cd concentrations except Cu, which led to higher phytoextraction efficiencies and partitioning to shoots of Zn, Pb and Cd. These results indicated synergistic effects between microbial inocula and chitosan on Zn, Pb and Cd phytoextraction.