Metals In Shoots Research Articles

Impact of CaO, fly ash, sulfur and Na2S on the (im)mobilization and phytoavailability of Cd, Cu and Pb in contaminated soil

Soil heavy metals pollution is a serious problem worldwide due to its potential human health risks through food chain. Therefore, a sustainable solution is needed to efficiently remediate HMs contaminated soils. Our study aimed to assess the impact of CaO, fly ash, sulfur, and Na2S on the immobilization of Cd, Cu, and Pb and their uptake by Chinese cabbage (Brassica rapa chinensis) in a contaminated soil. The concentration of DTPA-extractable Cd, Cu, and Pb was significantly decreased as compared to control in treated soil. However, the solubility of Cd, Cu, and Pb has increased at greater extent in soil system which favored the uptake of metals in roots and shoots of Chinese cabbage. In general, Cd uptake was significantly increased in shoots followed by roots as compared to control. In addition, Cu has also same trend of increased uptake in shoots as compared to roots. However, the uptake Pb in shoots was considerably increased in Na2S treated samples whereas roots have shown great potential for Pb uptake in CaO treated samples as compared to control. Although, sulfur treatments had efficiently immobilized metals but reduced soil pH to highly acidic level which restricted the growth of Chinese cabbage in sulfur treated samples. We assume that sulfur amendment could be applied for immobilization of metals in alkaline soils rather than acidic soils to achieve better immobilization results. In order to achieve sustainable phytoextraction of Cd, Cu, and Pb using CaO, FA, and Na2S, the non-edible hyperaccumulators species are suggested to be investigated in future studies.

Improving prediction of metal uptake by Chinese cabbage (Brassica pekinensis L.) based on a soil-plant stepwise analysis

It is crucial to develop predictive soil-plant transfer (SPT) models to derive the threshold values of toxic metals in contaminated arable soils. The present study was designed to examine the heavy metal uptake pattern and to improve the prediction of metal uptake by Chinese cabbage grown in agricultural soils with multiple contamination by Cd, Cu, Ni, Pb, and Zn. Pot experiments were performed with 25 historically contaminated soils to determine metal accumulation in different parts of Chinese cabbage. Different soil bioavailable metal fractions were determined using different extractants (0.43M HNO3, 0.01M CaCl2, 0.005M DTPA, and 0.01M LWMOAs), soil moisture samplers, and diffusive gradients in thin films (DGT), and the fractions were compared with shoot metal uptake using both direct and stepwise multiple regression analysis. The stepwise approach significantly improved the prediction of metal uptake by cabbage over the direct approach. Strongly pH dependent or nonlinear relationships were found for the adsorption of root surfaces and in root-shoot uptake processes. Metals were linearly translocated from the root surface to the root. Therefore, the nonlinearity of uptake pattern is an important explanation for the inadequacy of the direct approach in some cases. The stepwise approach offers an alternative and robust method to study the pattern of metal uptake by Chinese cabbage (Brassica pekinensis L.).

Phytoremediation Opportunities with Alimurgic Species in Metal-Contaminated Environments

Alimurgic species are edible wild plants growing spontaneously as invasive weeds in natural grassland and farmed fields. Growing interest in biodiversity conservation projects suggests deeper study of the multifunctional roles they can play in metal uptake for phytoremediation and their food safety when cultivated in polluted land. In this study, the responses of the tap-rooted perennial species Cichorium intybus L., Sonchus oleracerus L., Taraxacum officinale Web., Tragopogon porrifolius L. and Rumex acetosa L. were studied in artificially-highly Cd-Co-Cu-Pb-Zn-contaminated soil in a pot-scale trial, and those of T. officinale and R. acetosa in critical open environments (i.e., landfill, ditch sediments, and sides of highly-trafficked roads). Germination was not inhibited, and all species showed appreciable growth, despite considerable increases in tissue metal rates. Substantial growth impairments were observed in C. intybus, T. officinale and T. porrifolius; R. acetosa and S. oleracerus were only marginally affected. Zn was generally well translocated and reached a high leaf concentration, especially in T. officinale (~600 mg·kg−1·dry weight, DW), a result which can be exploited for phytoremediation purposes. The elevated Cd translocation also suggested applications to phytoextraction, particularly with C. intybus, in which leaf Cd reached ~16 mg·kg−1·DW. The generally high root retention of Pb and Cu may allow their phytostabilisation in the medium-term in no-tillage systems, together with significant reductions in metal leaching compared with bare soil. In open systems, critical soil Pb and Zn were associated with heavily trafficked roadsides, although this was only seldom reflected in shoot metal accumulation. It is concluded that a community of alimurgic species can serve to establish an efficient, long-lasting vegetation cover applied for phytoremediation and reduction of soil metal movements in degraded environments. However, their food use is not recommended, since leaf Cd and Pb may exceed EU safety thresholds.

Single and mixed chelants-assisted phytoextraction of heavy metals in municipal waste dump soil by castor

The phytoextraction of some toxic heavy metals from municipal waste dump soil by castor plant (Ricinus communis) was tested under natural and single or mixed chelant-assisted scenarios in pot microcosms. A sandy loam with total metal contents (mg/kg): Cd (84.5), Cu (114.5), Ni (70.3), Pb (57.8), and Zn (117.5), was sampled from an active dumpsite in Calabar, Nigeria and used for the study. Castor (small seed variety) was grown under natural phytoextraction or single/binary chelant (citric acid, oxalic acid, and EDTA) applications (5-20 mmol/kg soil) for 63 days. Castor exhibited no visual phytotoxic symptoms with typically sigmoid growth profiles at the applied chelant doses. Growth rates, however, decelerated with increase in chelant dose. Post-harvest biomass yields were higher under chelant application than for natural phytoextraction. Both root and shoot metal concentrations (mg/kg) increased quasilinearly and significantly (p

English

Seasonal impact on soil trace metals and phytoaccumulation potentials of Cucurbita pepo, Cucumis sativus and Taliferia occidentalis grown in Ishiagu quarry mining effluent discharge soils were investigated. Soil samples were collected 200 m (sample C), 100 m (sample B) away from discharge point (sample A) in wet and dry seasons. Trace metals were analysed using atomic absorption spectrophotometer. Results reveal a significant decrease in levels of trace metals distance away from discharge points in the order A>B>C. Findings from the study show significant increase in level of soil trace metals in dry season compared to wet season. Phyto-accumulation potentials of the vegetables showed significant increase in level of trace metals in roots and shoots in dry season compared to wet season. Level of these metals were significantly higher compared to control. This is indicative of the potential risk associated with consumption of vegetables grown in these sites especially in dry seasons. The rural dwellers should be discouraged from planting edible vegetables around Ishiagu quarry mining effluent discharge soils in order to reduce excessive build-up of these metals in the human food chain. Key words: Phyto-accumulation, trace metals, quarry mining, discharge soils, seasonal impact.

The Potential of Abelmoschus esculentus in EDTA-Asssisted Phytoextraction of Heavy Metals from Soil of Bashiri Dumpsite, Ado Ekiti, Nigeria

The use of fast-growing tropical plants in planning phytoextraction strategies has been documented by several researchers. The work presented here examines the effect of germination on chelate-assisted phytoextraction of heavy metals by Abelmoschus esculentus cultivated on the Bashiri dumpsite Ado Ekiti. Topsoil (0 – 15 cm) samples were randomly collected from the dumpsite, control samples were collected in similar manner at 200 m away from the dumpsite. The pH, content of organic matter, cation exchange capacity as well as heavy metals concentrations of the soil samples were determined after the soil samples were treated properly. The seedlings of Abelmoschus esculentus was cultivated in different pots (for soil with EDTA) and control pots (for soil without EDTA), these plants were subsequently nurtured maturity by daily irrigation. The plants were harvested into parts at different germination stages, after which heavy metals concentrations (Cd, Cr, Pb, Zn, Co, Cu,Fe, Mn, and Ni) were determined. The result revealed the mean pH, content of organic matter and cation exchange capacity on dumpsite of 7.50 ± 0.12, 7.8 ± 0.12%, 40.10 ± 0.11 mmol/kg, respectively. The values for pH and the organic matter were higher than those obtained from control sites. Though, heavy metals concentrations on the dumpsite were higher than control site, their values reduced considerably to maturity. Early symptoms of phytotoxicity were noticed with an application of 0.2 g/kg EDTA of soil, which only affected the biomass levels of the experimental Abelmoschus esculentus but increased the concentrations of heavy metals in the plant shoot when compared with nonchelate assisted process. However, TF, BF and RR values greater than one measure phtoextraction efficiency, an indication of the possible application Abelmoschus esculentus for phytoextraction strategies. KeywordsEffect; Chelate Assisted; Heavy Metals; Phytoextractio; Basiri Dumpsite

Effect of heavy metals combined stress on growth and metals accumulation of three Salix species with different cutting position

ABSTRACTThis study aimed to compare growth performance and heavy metal (HM) accumulation at different cutting positions of Salix species grown in multi-metal culture. Three Salix species stems cut at different positions (apical to basal) were grown hydroponically for four weeks. The plants were then treated for three weeks with 0, 5, 10, and 20 μM Cd, Cu, Pb, and Zn, resulting in total metal concentrations of 0, 20, 40, and 80 μM. The growth parameters and HM content in shoots and initial cutting were measured. Results showed that, compared with S. fragilis, S. matsudana grew more poorly in uncontaminated condition but grew better and accumulated lower metal in shoots under mixed HM treatment. In addition, cuttings from apical parent stem position exhibited poorer growth performance before and after treatment, as well as greater metal content in shoots than base parts under the HM treatment. These results suggest that S. matsudana may undergo a special mechanism to hinder metals in the initial cutting, thus mitigating growth damage. The apical portion also showed poor resistance against the invasion of mixed HMs because of the immature structure. Therefore, in the selection of phytoremediation plants, metal accumulation ability is not proportional to growth performance.

Inoculation of ectomycorrhizal fungi contributes to the survival of tree seedlings in a copper mine tailing

To advance our understanding of the effects of inoculation with ectomycorrhizal fungi (EMF) on seedling colonization in mine wastelands, we conducted a field experiment in a copper tailing. Six-month-old seedlings of Japanese red pine (Pinus densiflora) and oak (Quercus variabilis) separately inoculated with three EMF species (Pisolithus sp., Cenococcum geophilum, Laccaria laccata) were transplanted to the copper tailing. The survival rates of tree seedlings were monitored monthly, and growth (biomass and height), contents of nutrients and heavy metals (K, P, Ca, Mg, Cu, Zn), and mycorrhizal infection rates of seedlings were determined 6 months after planting. Oak seedlings exhibited higher survival rates than pine seedlings after 6 months of growth on the tailing. EMF inoculations of pine seedlings significantly enhanced their survival, growth, and nutrient uptake. In contrast, EMF inoculations of oak seedlings improved growth only in terms of biomass. Additionally, EMF inoculation caused pine seedlings to accumulate more Cu and Zn in roots compared to non-inoculated seedlings, whereas inoculation inhibited the accumulation of heavy metals in shoots. However, similar results were not observed in oak seedlings. Observations of roots indicated that the rates of mycorrhizal infection of both tree species had dramatically declined at harvest time. In conclusion, ectomycorrhizal symbioses can improve the survival and performance of pine seedlings in mine tailings. The present study provided direct evidence of the importance of EMF inoculation of seedlings to the reforestation of mine wastelands.

Inoculation methods using Rhodococcus erythropolis strain P30 affects bacterial assisted phytoextraction capacity of Nicotiana tabacum

ABSTRACTIn this study different bacterial inoculation methods were tested for tobacco plants growing in a mine-soil contaminated with Pb, Zn, and Cd. The inoculation methods evaluated were: seed inoculation, soil inoculation, dual soil inoculation event, and seed+soil inoculation. Each inoculum was added at two bacterial densities (106 CFUs mL−1 and 108 CFUs mL−1). The objectives were to evaluate whether or not the mode of inoculation or the number of applied microorganisms influences plant response. The most pronounced bacterial-induced effect was found for biomass production, and the soil inoculation treatment (using 106 CFUs mL−1) led to the highest increase in shoot dry weight yield (up to 45%). Bacterial-induced effects on shoot metal concentrations were less pronounced; although a positive effect was found on shoot Pb concentration when using 108 CFUs mL−1 in the soil inoculation (29% increase) and in the seed+soil inoculation (34% increase). Also shoot Zn concentration increased by 24% after seed inoculation with 106 CFUs mL−1. The best effects on the total metal yield were not correlated with an increasing number of inoculated bacteria. In fact the best results were found after a single soil inoculation using the lower cellular density of 106 CFUs mL−1.

Heavy metals pollution of Kotlin Island in the Gulf of Finland

The current environmental state of Kotlin Island and coastal areas reflects the negative impact of industry, transport and urban utilities that has lead to increased heavy metal content in soils, in terrestrial and aquatic vegetation and in the water of the Gulf of Finland. Based on the analysis of pollutant metals in roots and shoots of native plants grown on Kotlin Island, species with high metal-accumulating capacity have been identified. Of these, there were dandelion and coltsfoot demonstrating high mobility in heavy metals Zn especially upward transfer. These could therefore be promising as bioindicators and phytoremediators of polluted areas pointing to origins of contamination. The presence of heavy metal contamination in the coastal waters of the gulf and its variability along the coastline is regarded as dependent on multiple sources of pollution associated with Kotlin Island, namely industrial and municipal waste waters, ship and vehicle traffic, aerosol deposits, contamination by dredging activity in a new port as well as the result of metals leaching from the soils of the island (Zn, Cu, Ni). Metal-accumulating coastal plants such as cane can be a source of secondary pollution of the gulf waters during their seasonal decomposition. The data showed significantly elevated concentrations of Ni, Zn and Cd in the hair of children living in the town of Kronstadt located on Kotlin Island that confirms the adequacy of the proposed indicating methodology and shows the unfavorable environmental situation in the region.

Chemical and plant tests to assess the viability of amendments to reduce metal availability in mine soils and tailings.

The goal of this research was to assess the potential of several industrial wastes to immobilise metals in two polluted soils deriving from an old Pb/Zn mine. Two different approaches were used to assess the performance of different amendments: a chemical one, using extraction by ethylenediaminetetraacetic acid (EDTA), and a biological one, using Lupinus albus as a bio-indicator. Four amendments were used: inorganic sugar production waste (named 'sugar foam', SF), sludge from a drinking water treatment sludge (DWS), organic waste from olive mill waste (OMW) and paper mill sludge (PMS). Amendment to soil ratios ranged from 0.1 to 0.3 (w/w). All the amendments were capable of significantly decreasing (p < 0.05) EDTA-extractable Pb, Zn and Cu concentrations in the two soils used, with decreases in ranges 21-100, 25-100 and 2-100 % for Pb, Zn and Cu, respectively. The amendments tested were also effective in reducing the bioavailability of Pb and Zn for L. albus, which gave rise to a decrease in shoot metal accumulation by the lupine plants compared to that found in the control soil. That decrease reached up to 5.6 and 2.8 times for Pb and Zn, respectively, being statistically significant in most cases. Moreover, application of the OMW, DWS and SF amendments led to higher average values of plant biomass (up to 71%) than those obtained in the control soil. The results obtained showed the technology put forward to be a viable means of remediating mine soils as it led to a decrease in the availability and toxicity of metals and, thus, facilitated the growth of a vegetation layer.

Rhizofiltration of Heavy Metals (Cadmium, Lead and Zinc) From Fly Ash Leachates Using Water Hyacinth (Eichhornia Crassipes)

Fly ashes are usually contaminated with toxic heavy metals. These metals are leaching out aftercontact with water during wet disposal system, thus polluting the soil, surface and groundwater. In the present study, a hydroponics experiment was conducted to examine the removalof heavy metals Cd, Pb and Zn by Eichhornia crassipes grown at various concentration of fly ash ranging from 10, 20 and 40 percent over a period of 30 days.After 30 days, the plants were separately harvested, dried and weighedfor biomass of the roots and shoots. The uptake of each metalwas studied in the root and shoot separately, to determine the bioaccumulation of metals in Eichhornia crasspies.The translocation factor was calculated to study the efficiency of the plants forbioaccumulation of each metal in roots and shoot. The results showed that maximum uptake of metals Cd, Pb and Zn by plantwasfoundat the higher concentration (40%) of fly ash.The metals uptake found was 99.16, 166.52 and 741.04 μg g-1 tissues in the roots, respectively and 33.46, 41.33 and 255.90 μgg-1 tissues in the shoots, respectively and successfullyremoved up to 78% of Cd, 82% of Pb and 70% of Zn.The maximum removal efficiency by plant for Cd, Pb and Zn at lower concentration (10%) of fly ash was 84%, 86% and 75%, respectively.The heavy metals accumulated more in roots than in the shoots by Eichhornia crassipes. The maximum bioconcentration factor and translocation factor value of Eichhornia crappies for Cd, Pb and Zn were calculated as 705.55, 705.55 and 614.51 and 41.86, 47.18 and 34.53 respectively. The high removal efficiencies of heavy metals Cd, Pb and Zn was find without toxic effect by this aquatic macrophyte, thisplant can be recommended for the actual treatment of fly ash leachatesin ash pond to clean up the aquatic environment.DOI: http://dx.doi.org/10.3126/ije.v4i1.12187International Journal of Environment Volume-4, Issue-1, Dec-Feb 2014/15, page : 179-196

Plant growth and metal uptake by a non-hyperaccumulating species (Lolium perenne) and a Cd-Zn hyperaccumulator (Noccaea caerulescens) in contaminated soils amended with biochar

Biochar could be used as a soil amendment in metal contaminated soils, for safe crop production or soil remediation purposes. This work was conducted to study the effects of biochar amendments on metal uptake by two contrasted plants grown on metal-contaminated soils. A non-hyperaccumulating plant (Lolium perenne) and a Cd- and Zn-hyperaccumulator (Noccea caerulescens) were grown in pots on acidic (A) and alkaline (B) soil contaminated by Cd, Pb and Zn, both amended by a wood-derived biochar. Biochar amendments decreased the availability of metals by increasing soil pH, but also decreased Ca, P and N availability. Growth of L. perenne was increased and shoot metal uptake decreased by biochar addition in both soils, although increasing biochar dose above 0.5 % resulted in a progressive decrease of shoot production on soil B. Growth of N. caerulescens was not significantly affected by biochar. But an increase of Cd uptake with 5 % biochar was recorded on both soils, and of Zn uptake on soil B. Beside immobilizing metals, biochar may decrease the availability of nutrients, leading either to plant deficiency or to a decreased competition with cations for metal uptake, thus enhancing extraction of metals by hyperaccumulators.

Impact of biochar and root-induced changes on metal dynamics in the rhizosphere of Agrostis capillaris and Lupinus albus

Rhizosphere interactions are deemed to play a key role in the success of phytoremediation technologies. Here, the effects of biochar and root-induced changes in the rhizosphere of Agrostis capillaris L. and Lupinus albus L. on metal (Cd, Pb and Zn) dynamics were investigated using a biotest on a 2mm soil layer and a sequential extraction procedure (Tessier’s scheme). In the bulk soil, the application of 5% biochar significantly reduced the exchangeable pool of metals primarily due to a liming effect which subsequently promoted the metal shift into the carbonate-bound pool. However, metals were re-mobilized in the rhizosphere of both A. capillaris and L. albus due to root-induced acidification which counteracted the liming effect of biochar. As a result, the concentrations of metals in roots and shoots of both plants were not significantly reduced by the application of biochar. Although the study should be considered a worst-case scenario because experimental conditions induced the intensification of rhizosphere processes, the results highlight that changes in rhizosphere pH can impact the effectiveness of biochar to immobilize metals in soil. Biochar has thus a potential as amendment for reducing metal uptake by plants, provided the acidification of the rhizosphere is minimized.

Chromium and nickel accumulation in the macrophytes of the Kawasi wetland on Obi Island, North Maluku Province, Indonesia

Five macrophytes, namely Crinum asiaticum L. (Amaryllidaceae), Lepironia articulata (Retz.) Domin (Cyperaceae), Machaerina rubiginosa (Spreng.) T. Koyama (Cyperaceae), Pandanus sp. (Pandanaceae) and Nepenthes mirabilis (Lour.) Druce (Nepenthaceae), were identified in the Kawasi wetland, a natural wetland on Obi Island, Indonesia, that overlies ultramafic rocks. The dominant species in this wetland was C. asiaticum, a native of the region. The surface runoff in the catchment of the Kawasi wetland was derived from serpentine soils, areas of which were being mined for nickel and, as a result, the water that flowed to the wetland typically contained dissolved chromium and nickel. In this study we investigated the accumulation of chromium and nickel in the macrophytes of the wetland. The five species of macrophytes under investigation accumulated greater quantities of chromium and nickel in their roots than in their shoots, with Pandanus sp. having the highest translocation factor (as evidenced by the highest shoot : root ratio) for both chromium and nickel. The species with the highest concentrations of the metals in both roots and shoots was C. asiaticum.

Metal partitioning in plant-substrate-water compartments under EDDS-assisted phytoextraction of pyrite waste with Brassica carinata A. Braun.

Soil amendment with chelating agents can increase metal uptake and translocation in biomass species through increased metal bioavailability together with possible increases in metal leaching. In this study, we assessed the efficiency and environmental risk of the fast-degradable [S,S]-EDDS. Cu, Pb and Zn uptake in pot-cultivated Brassica carinata A. Braun, residual substrate metal bioavailability and leaching were investigated after one cycle of EDDS-assisted phytoextraction in mixed metal-contaminated pyrite waste, which is characterised by high Fe content. The chelator was supplied at doses of 2.5 and 5 mmol EDDS kg(-1) waste 1 week before harvest and 1 mmol EDDS kg(-1) waste repeated five times at 5- and 10-day intervals during the growing cycle. Here we demonstrate that EDDS generally increases shoot metal concentrations-especially of Cu-but only seldom improves removals because of markedly impaired growth. Considerable phytotoxicity and Cu leaching occurred under repeated EDDS treatments, although environmental risks may also arise from the single, close-to-harvest applications as Cu bioavailability in waste at plant harvest still remained very high (up to +67 % at 5 mmol EDDS kg(-1) vs. untreated controls). The residual bioavailability of Zn and Pb was instead generally reduced, perhaps due to shifts in cation exchange, whereas Fe mobility was not apparently affected. The amount of metals removed by plants represented a small fraction of the bioavailable pool (<1 %), and mobilised metals quickly reached deep layers in the substrate. We conclude that EDDS assistance can provide only some limited opportunities for improving phytoremediation of pyrite waste, major benefits being achieved by low doses to be traditionally applied shortly before harvest, with due attention to limiting groundwater pollution.

Nickel and zinc accumulation capacities and tolerance to these metals in the excluder Thlaspi arvense and the hyperaccumulator Noccaea caerulescens

Representatives of Brassicaceae species—the hyperaccumulator Noccaea caerulescens F.K. Mey and the metal excluder Thlaspi arvense L.—were compared in terms of their ability to accumulate nickel (Ni) and zinc (Zn) and their tolerance to these metals. Four ecotypes of N. caerulescens were used: the ecotypes La Calamine (LC, Belgium) and Saint Felix de Pallieres (SF, France) grow naturally on calamine soils rich in Zn, Cd, and Pb; the ecotype Monte Prinzera (MP, Italy) originates from serpentine soils rich in Ni, Co, and Cr; and the ecotype Lellingen (LE, Luxembourg) inhabits non-metalliferous soils. The plants of N. caerulescens were grown for 8 weeks in a half-strength Hoagland solution supplemented with 25, 100, 200, 300, and 400 μM Ni(NO3)2 (ecotypes LC, SF, MP, LE) or 100, 200, 400, 800, and 1000 μM Zn(NO3)2 (ecotypes LC, SF, LE); the plants of T. arvense were grown in the presence of 10, 20, 25, and 30 μM Ni(NO3)2 or 40, 50, 60, 70, 80 μM Zn(NO3)2. The toxic effect of Ni and Zn was assessed from changes in dry matter of roots and shoots of treated plants compared to untreated. The content of metals in roots and shoots was determined by means of atomic absorption spectrophotometry. The Ni-accumulating capacity of N. caerulescens ecotypes increased in the order: LC < SF < LE < MP, and the Zn-accumulating capacity increased in the row: LC < SF < LE. In the hyperaccumulating plant N. caerulescens, the increments of biomass started to decrease at a lower metal content in roots than in shoots, whereas the opposite pattern was observed in the metal excluder T. arvense. Since T. arvense plants accumulated Ni and Zn in roots, whereas N. caerulescens accumulated these metals in shoots, one may assume that the greater sensitivity of root growth compared with shoots in N. caerulescens was determined by more effective mechanisms of metal detoxification in shoots. Conversely, the higher sensitivity of shoot growth compared to root growth in T. arvense was determined by more effective mechanisms of metal detoxification in roots. Being more tolerant to Ni and Zn than T. arvense plants, the N. caerulescens ecotypes differed substantially in terms of metal-accumulating capacity and their tolerance to heavy metals. The ecotype originating from non-metalliferous soils (LE) accumulated larger amounts of Zn, but was less tolerant compared with ecotypes growing naturally on calamine soils (SF and LC), whereas the ecotype occurring on serpentine soils (MP) exhibited a markedly greater tolerance to Ni, compared with other ecotypes examined, as well as the largest accumulation of this metal. The results indicate the existence of different mechanisms responsible for plant tolerance to Ni and Zn; the study of these mechanisms is a promising direction for future research.

Genome-Wide Identification of Transition Metal Ion Transporters in Oryza sativa

Transition metals are essential minerals required for normal growth and development of plants which are taken in correct proportions from the soil and distributed throughout the plant. The concentrations of transition metals in roots, shoots and grains were analyzed in Oryza sativa indica cultivars viz., Sona Masuri (BPT 5204), Swarna (MTU 7029) and Vijetha (MTU1001). In roots the concentration of iron was highest in Sona masuri variety, followed by manganese and zinc. In shoots and grains, iron was highest followed by zinc suggesting specific transport mechanisms in all the parts. A total of 55 genes for transition metal ion transport were identified using insilico tools of which 18 involved in zinc/iron transport, 13 for copper, 7 for manganese, 3 for cobalt, 4 for cadmium and 10 transport metal ions belonging to Nramp family. Research carried out on these metal transporters mainly provides insights into the field of rice metal biology.

Comparative analysis of Cd and Zn impacts on root distribution and morphology of Lolium perenne and Trifolium repens: implications for phytostabilization

Backgrounds and aims The phytostabilization potential of plants is a direct function of their root systems. An experimental design was developed to investigate the impact of Cd and Zn on the root distribution and morphology of Lolium perenne and Trifolium repens. Methods Seedlings were transplanted into columns filled with washed quartz and irrigated daily with Cdor Zn-containing nutrient solutions during 1 month. Root biomass, root length density (RLD) and diameter were subsequently quantified as a function of depth. Pot experiments were also performed to quantify metal, lignin and structural polysaccharides concentrations as well as cell viability. Results Lolium perenne accumulated Cd and Zn in the roots whereas T. repens was unable to restrict heavy metal translocation. Cadmium and Zn reduced rooting depth and RLDbut induced thick shoot-borne roots in L. perenne. Cd-induced root swelling was related to lignification occurring in the exodermis and parenchyma of central cylinder. Hemicelluloses and lignin did not play a key role in root metal retention. Cadmium slightly reduced mean root cell viability whereas Zn increased this parameter in comparison to Cd. Conclusions Even though plant species like Lolium perenne and Trifolium repens may appear suitable for a phytostabilization scheme based on their shoot metal tolerance, exposure to toxic heavy metals drastically impairs their root distribution. This could jeopardize the setting up of phytostabilization trials. The metal-induced alterations of root system properties are clearly metal- and speciesspecific. At sites polluted with multiple metals, it is therefore recommended to first test their impact on the root system of multiple plant species so as to select the most appropriate species for each site.

Heavy metal accumulation and phytostabilization potential of dominant plant species growing on manganese mine tailings

Screening plants that are hypertolerant to and excluders of certain heavy metals plays a fundamental role in a remediation strategy for metalliferous mine tailings. A field survey of terrestrial higher plants growing on Mn mine tailings at Huayuan, Hunan Province, China was conducted to identify candidate species for application in phytostabilization of the tailings in this region. In total, 51 species belonging to 21 families were recorded and the 12 dominant plants were investigated for their potential in phytostabilization of heavy metals. Eight plant species, Alternanthera philoxeroides, Artemisia princeps, Bidens frondosa, Bidens pilosa, Cynodon dactylon, Digitaria sanguinalis, Erigeron canadensis, and Setaria plicata accumulated much lower concentrations of heavy metals in shoots and roots than the associated soils and bioconcentration factors (BFs) for Cd, Mn, Pb and Zn were all < 1, demonstrating a high tolerance to heavy metals and poor metals translocation ability. The field investigation also found that these species grew fast, accumulated biomass rapidly and developed a vegetation cover in a relatively short time. Therefore, they are good candidates for phytostabilization purposes and could be used as pioneer species in phytoremediation of Mn mine tailings in this region of South China.