Metal Accumulation In Plant Tissues Research Articles

Assessment of arbuscular mycorrhizal fungi status and heavy metal accumulation characteristics of tree species in a lead–zinc mine area: potential applications for phytoremediation

To select suitable tree species associated with arbuscular mycorrhizal fungi (AMF) for phytoremediation of heavy metal (HM) contaminated area, we measured the AMF status and heavy metal accumulation in plant tissues in a lead-zinc mine area, Northwest China. All 15 tree species were colonized by AM fungi in our investigation. The mycorrhizal frequency (F%), mycorrhizal colonization intensity (M%) and spore density (SP) reduced concomitantly with increasing Pb and Zn levels; however, positive correlations were found between arbuscule density (A%) and soil total/DTPA-extractable Pb concentrations. The average concentrations of Pb, Zn, Cu and Cd in plant samples were 168.21, 96.61, 41.06, and 0.79mg/kg, respectively. Populus purdomii Rehd. accumulated the highest concentrations of Zn (432.08mg/kg) and Cu (140.85mg/kg) in its leaves. Considerable amount of Pb (712.37mg/kg) and Cd (3.86mg/kg) were concentrated in the roots of Robinia pseudoacacia Linn. and Populus simonii Carr., respectively. Plants developed different strategies to survive in HM stress environment: translocating more essential metals (Zn and Cu) into the aerial parts, while retaining more toxic heavy metals (Pb and Cd) in the roots to protect the above-ground parts from damage. According to the translocation factor (TF), bioconcentration factor (BCF), growth rate and biomass production, five tree species (Ailanthus altissima (Mill.) Swingle, Cotinus coggygria Scop., P. simonii, P. purdomii, and R. pseudoacacia) were considered to be the most suitable candidates for phytoextraction and/or phytostabilization purposes. Redundancy analysis (RDA) showed that the efficiency of phytoremediation was enhanced by AM symbioses, and soil pH, Pb, Zn, and Cd levels were the main factors influencing the HM accumulation characteristics of plants.

PHYTOSTABILIZATION OF MOSABONI COPPER MINE TAILINGS: A GREEN STEP TOWARDS WASTE MANAGEMENT

Bare metal mine tailings are prone to erosion as the very young top soils develop on unstable materials with low cohesion and also cause environmental pollution through leaching of toxic metals to surroundings. An appropriate vegetation cover may reduce the erosion and immobilize toxic metals through phytostabilization. The abandoned copper mines in Mosaboni (Jharkhand, India) left huge amount of untreated tailings containing high concentration toxic metals and became a source of metal pollutants. So, through a pot scale study an attempt was made to determine the potential of Cymbopogon citratus in phytostabilization of copper tailings with and without amendment. Although, limited plant growth was observed on pure tailings (T); addition of chicken manure (M) or soil-manure mixture (MS) caused manifold increase in plant growth. Application of M caused more accumulation of toxic metals in aerial parts indicating possible threat of entry of toxic metal into the food chain. However, use of MS reduced metal accumulation in plant tissue. So, in the present case, where there is no option for continuous harvesting and disposal of plant biomass in the secured landfill, phytostabilization is more appropriate than phytoextraction, and lemon grass could be used in combination with MS to stabilize bare tailings.

Metal dynamics and tolerance of Typha domingensis exposed to high concentrations of Cr, Ni and Zn

Typha domingensis was exposed to a 100mgL−1 Cr+100mgL−1 Ni+100mgL−1 Zn solution. Metal tolerance and metal accumulation in plant tissues and sediment were studied over time. Although removal rates were different, the three metals were efficiently removed from water. Leaf and root tissues showed high metal concentration. However, the sediment showed the highest accumulation. During the first hours of contact, metals were not only accumulated by sediment and roots but they were also taken up by the leaves in direct contact with the solution. Over time, metals were translocated from roots to leaves and vice versa. Metals caused growth inhibition and a decrease in chlorophyll concentration and affected anatomical parameters. Despite these sub-lethal effects, T. domingensis demonstrated that it could accumulate Cr, Ni and Zn efficiently and survive an accidental dump of high concentrations of contaminants in systems such as natural and constructed wetlands.

Interaction of Heavy Metals and Pyrene on Their Fates in Soil and Tall Fescue (Festuca arundinacea)

90-Day growth chamber experiments were performed to investigate the interactive effect of pyrene and heavy metals (Cu, Cd, and Pb) on the growth of tall fescue and its uptake, accumulation, and dissipation of heavy metals and pyrene. Results show that plant growth and phytomass production were impacted by the interaction of heavy metals and pyrene. They were significantly decreased with heavy metal additions (100-2000 mg/kg), but they were only slightly declined with pyrene spiked up to 100 mg/kg. The addition of a moderate dosage of pyrene (100 mg/kg) lessened heavy metal toxicity to plants, resulting in enhanced plant growth and increased metal accumulation in plant tissues, thus improving heavy metal removal by plants. In contrast, heavy metals always reduced both plant growth and pyrene dissipation in soils. The chemical forms of Cu, Cd, and Pb in plant organs varied with metal species and pyrene addition. The dissipation and mineralization of pyrene tended to decline in both planted soil and unplanted soils with the presence of heavy metals, whereas they were enhanced with planting. The results demonstrate the complex interactive effects of organic pollutants and heavy metals on phytoremediation in soils. It can be concluded that, to a certain extent, tall fescue may be useful for phytoremediation of pyrene-heavy metal-contaminated sites. Further work is needed to enhance methods for phytoremediation of heavy metal-organics co-contaminated soil.

Plant growth regulators-assisted phytoextraction

Plant growth regulators (PRG)-assisted phytoremediation is a technique that could enhance the yield of heavy metal accumulation in plant tissues. So far, a small number of experiments have helped identify three groups of plant hormones that may be useful for this purpose: auxins, cytokinins, and gibberellins. Studies have shown that these hormones positively affect the degree of accumulation of metallic impurities and improve the growth and stress resistance of plants. This review summarizes the present knowledge about PGRs’ impact on phytoextraction yield.

PHYTOSTABILIZATION OF IRON ORE TAILINGS THROUGH CALOPHYLLUM INOPHYLLUM L.

The phytostabilization of waste material generated during mining and processing of iron ore through Calophyllum inophyllum L. have been investigated. Iron ore tailings and its varying composition with garden soil were taken to study plant growth, chlorophyll content and metal uptake pattern of Calophyllum inophyllum L. These studies indicate that 100% survival of plant species was noted in all the treatments without any toxicity symptoms. The increase in growth parameters and chlorophyll content along with the high metal accumulation in plant tissues suggests that Calophyllum inophyllum L. may be a potential tool for phytoremediation. The accumulation of Pb (1662 μgm/gm) and Fe (2313 μgm/gm) was observed to be maximum in the plant tissues followed by Cu, Zn, Cr, and Ni. The TF values for most of the heavy metals was observed to be > 1 which indicates that the plant can efficiently translocate these toxic metals to its above ground parts. Removal of more than 30% of the most of the heavy metal like Fe, Pb, and Cu & Zn has been observed in all the treatments during one year of observation. The overall study clearly suggests that the plant can be used as an efficient tool for restoration of mining wastes and other similarly contaminated sites.

Fractionation and availability of heavy metals in tannery sludge-amended soil and toxicity assessment on the fully–grown Phaseolus vulgaris cultivars

This study was conducted to assess the effect of tannery sludge on the bush bean (Phaseolus vulgaris) cultivars fully–grown on a culture sandy soil, as tannery sludge is valuable to improve soil fertility but long term studies evaluating the effect on fully grown plants are scarce. Tannery sludge amendments (0, 0.77, 1.54, 3.08 and 6.16 g tannery sludge kg−1 soil) were characterized and the main heavy metals identified (Cr, Mn, Fe, K, and Zn) later on sequentially and singly extracted, for soil fractionation and availability determination, respectively. Metals showed different fractionation and availability patterns, being the most toxic metal (Cr) found to primarily bind to the carbonate fraction in soil, while almost 10% of the total Cr was available for plant uptake. In the green house experiments, bush bean cultivars exposed to increasing tannery sludge amendments were evaluated at different plant stages. Metal accumulation and physiological parameters (chlorophyll, carotenoids, nitrate reductase activity and dry weight) were determined. Toxicity was primarily due to Cr, stimulating or affecting the response of physiological parameters and suppressing seed formation at the highest tannery sludge ratio. Metals were mainly accumulated in the roots of bush beans, diminishing in the upper part of the plants with minimal translocation to seeds, supposing little risk for human consumption. Additionally, important correlations, antagonistic and synergistic relationships were observed between the extracted metals and metal accumulation in plant tissues.

HEAVY METAL ACCUMULATION IN Ipomoea reptans AND Helianthus annuus.

Heavy metals contaminations are among the most hazardous environmental pollution due to its ability to resist disintegration in the natural ecosystem. Thus, they pose risk to living organisms as they are persistent in the environment. Reports on the accumulations of heavy metal in edible plants had alarmed many parties that the general public has become more aware on the seriousness of this issue. Bioaccumulation within the food chain poses potential risks of toxicity effects. Thus, it is crucial to conduct appropriate study to analyze the pathway of the heavy metal elements as a measure to understand the behavior of the heavy metal elements. The aim of this paper is to investigate heavy metal accumulation in plant tissue, particularly the leave, stem and root. Ipomoea reptans and Helianthus annuus were selected as the experimental plant species in the study. Spent dry cell or batteries were utilized as the source of heavy metal contamination of which batteries are commonly discarded in the municipal solid waste stream. Results indicated that the accumulation of heavy metals in the two plants were low and below the limit of European Union Standard for edible plants. However, heavy metal in alkaline batteries exposure was found to promote the growth of longer root in both plants as compared to carbon-zinc batteries and the control. Yet, the accumulation of heavy metal in the plants tissues in this study were only monitored for the period based on the maturation of the plants, longer exposure may result with different outcome, that further investigation is deemed necessary. (Keywords: heavy metal, batteries, edible plants, bioaccumulations)

Improvement of plant growth and nickel uptake by nickel resistant-plant-growth promoting bacteria

In this study, among a collection of Ni-resistant bacterial strains isolated from the rhizosphere of Alyssum serpyllifolium and Phleum phleoides grown on serpentine soil, five plant growth-promoting bacteria (PGPB) were selected based on their ability to utilize 1-aminocyclopropane-1-carboxylate (ACC) as the sole N source and promote seedling growth. All of the strains tested positive for indole-3-acetic acid (IAA) production and phosphate solubilization. In addition, four of the strains exhibited significant levels of siderophores production. Further, the efficiency of PGPB in enhancing Ni solubilization in soils was analyzed. Compared with control treatment, inoculation of PGPB strains significantly increased the concentrations of bioavailable Ni. Furthermore, a pot experiment was conducted to elucidate the effects of inoculating Ni-resistant PGPB on the plant growth and the uptake of Ni by Brassica juncea and B. oxyrrhina in soil contaminated with 450 mg kg −1 Ni. Psychrobacter sp. SRA2 significantly increased the fresh (351%) and dry biomass (285%) of the B. juncea test plants ( p < 0.05), whereas Psychrobacter sp. SRA1 and Bacillus cereus SRA10 significantly increased the accumulation of Ni in the root and shoot tissues of B. juncea compared with non-inoculated controls. This result indicates that the strains SRA1 and SRA10 facilitated the release of Ni from the non-soluble phases in the soil, thus enhancing the availability of Ni to plants. A significant increase, greater than that of the control, was also noted for growth parameters of the B. oxyrrhina test plants when the seeds were treated with strain SRA2. This effect can be attributed to the utilization of ACC, solubilization of phosphate and production of IAA. The results of the study revealed that the inoculation of Ni mobilizing strains Psychrobacter sp. SRA1 and B. cereus SRA10 increases the efficiency of phytoextraction directly by enhancing the metal accumulation in plant tissues and the efficient PGPB, Psychrobacter sp. SRA2 increases indirectly by promoting the growth of B. juncea and B. oxyrrhina.

The content of some macronutrients and heavy metals in aquatic macrophytes of three ecosystems connected to the Danube in Yugoslavia.

In the study of three different aquatic ecosystems connected with the Danube river we determined the concentrations of macronutrients (N, P, K, Ca), Na and heavy metals (Fe, Mn, Ni, Pb and Cd) in the most common submerged, floating and emerged aquatic plants: Ceratophyllum demersum, Myriophyllum spicatum, Vallisneria spiralis, Salvinia natans, Hydrocharis morsus ranae, Trapa longicarpa, Nymphoides flava, Nymphaea alba, and Phragmites communis. Analyses were done during the seasonal biomass peak (June - August) in 1999. Significantly higher macronutrients and heavy metal concentrations in submerged when compared to floating and emerged aquatic plants were found. From the heavy metal concentrations which were measured, iron showed the highest values followed by manganese, nickel and lead, while cadmium exhibited trace concentrations. The degree of metal accumulation in plant tissues (expressed as tissue metal concentration/surrounding water concentration ratio) was locality-dependent. The highest degree was recorded for Mn and Fe. The obtained results indicated an evident chemical pollution of the DTD canal section (near Novi Sad) where V spiralis had the highest bioaccurnulation of lie and Mn.

Long‐term Sludge Applications on Cadmium and Zinc Accumulation in Swiss Chard and Radish

AbstractSwiss chard (Beta vulgare var. Fordhook) and radish (Raphanus sativus var. Cherry Belle) were grown twice annually (spring and fall) on a Ramona sandy loam (fine‐loamy, mixed thermic, Typic Haploxeralfs) soil treated with 0, 22.5, 45, 90, and 180 Mg ha−1 yr−1 of composted sludges from Los Angeles. The soil received two sludge inputs of equal amounts each year and crops were planted shortly after each sludge incorporation. Cadmium and Zn accumulation of the plant tissue from 1976 to 1985 was examined. Results from the analysis of variance indicated that effects due to sludge application rates, seasons plants were grown, number of years of sludge application, and their interactions were all significant. If the data sets were partitioned according to sludge application rates and seasons, metal concentrations of the plant tissue may be expressed as a nonlinear regression model, y = a + b (1 − e−cx), where y is the metal concentration of the plant tissue, x is the cumulative sludge loading, and a, b, and c are constants. All but two nonlinear regressions were significant at p &lt;0.05 with R2 from 0.38 to 0.95. The deviation of the observed values from the predictions of the regression model indicated that other factors might have also affected the metal uptake by plants. Stepwise multiple regression analysis of the partitioned data sets indicated that soil pH, soil salinity, soil temperature, and length of growing season influenced the metal accumulation in plant tissue.