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Morphological Responses of Korean Native Plant Hosta longipes to Heavy Metals Cd, Pb, and Zn
Abstract
The aim of this study was to examine the morphological responses of Hosta longipes, an ornamental plants for heavy metal contaminated soils in urban landscaping, to heavy metals Cd, Pb, and Zn. Plants were grown in artificial soil amended with Cd, Pb, and Zn at concentation of 0, 100, 250, and 500 mg/kg. Plant height, leaf length, leaf width, total leaf number, deaf leaf number, new leaf number, chlorophyll contents, and ornamental value were monitored from May to August. At 4 months after planting, the survival and morphological responses of H. longipes grown in soil amended with Cd at concentrations {\geq}100mg/kg were severely affected compared to those grown in the control soil. Relative leaf length rate and relative leaf width rate were significantly decreased when the concentration of Pb was increased. Total leaf number, chlorophyll contents, and ornamental value were the lowest value in plants grown in soil amended with Pb at level of 500 mg/kg. Relative leaf length rate and relative leaf width rate, total leaf number, dead leaf number, new leaf number, and ornamental values had a tendency of decrease when plants were grown in soils amended with Zn. However, no significant difference was found among treatments except for plants were grown in soils amended with 500 mg/kg Zn. Therefore, Hosta longipes might be useful for phytoremediation of Zn contaminated sites as herbaceous ornamental plants.
The present study was conducted for the bioremediation of alkylphenols using rhizosphere microorganisms isolated from the roots of land plant. Three land plants (Hosta undulata, Anemone flaccida, and Aquilegia flabellate var. pumila) were used to analyze the tolerance against petroleum hydrocarbons and alkylphenols. The plant Hosta undulata showed the tolerance against petroleum hydrocarbons (500 mg kg-1) and one of the alkylphenol, i.e., 4-tert-butylphenol (4-t-BP). Hence, thirty bacterial and thirteen fungal strains were isolated from the 4-t-BP contaminated soil collected from the roots of this plant. Biodegradation of alkylphenols was investigated using the isolated bacteria and fungi. Decrement in the alkylphenols was analyzed using high pressure liquid chromatography (HPLC). Fungi showed higher 4-t-BP degradation than bacteria. Strain SB-4 (Penicillium pinophilum) showed 76.8%, and strain SB-7 (Trichoderma asperellum) showed 49.2% degradation of 4-t-BP under shaking and static conditions respectively. Apart from 4-t-BP, strain SB-7 degraded other alkylphenols such as 4-sec-butylphenol, 4-tert-octylphenol, and 4-nonylphenol. The major metabolites produced during alkylphenols degradation with strain SB-7 were determined were determined using Gas chromatography linked with mass spectrometry (GC-MS). The results suggested that the plant Hosta undulata had tolerance against the toxic compounds, and the rhizosphere microorganisms isolated from the roots of this plant might be applied for the bioremediation of alkylphenols contaminated soils.
This study targeted a historical zinc smelting site from southwestern China and investigated the distribution, mobility, and dispersion patterns of trace metals in the surrounding environment. A series of soil, smelting slag, stream sediment, stream water, and groundwater samples were collected from the smelting site and analyzed for Pb, Zn, and Cd. The results showed that the smelting site was seriously polluted with Pb, Zn, and Cd from past smelting fume deposition and smelting slags. Metal fractions and ratios were applied to identify metal dispersion and mobility. During smelting, Cd was preferably volatilized and transported into the surrounding environment, Zn was predominantly recuperated, and Pb was predominantly retained in smelting slags. Metals in contaminated soils were more mobile than those in slags, but slags still posed long-term risk to the surrounding environment with elevated metals. The relative amounts of vertical transport of metals appeared to follow the order of Cd > Zn > Pb, similar to the mobility order by BCR sequential extractions. Sediments and suspended particulate matter (SPM) in the local stream were derived from the contaminated soils and slags. Compared to the local groundwater with little metal pollution, the stream water at the smelting site was heavily polluted with Pb, Zn, and Cd. Elevated metals in the stream water occurred predominantly in SPM due to soil and slag erosion.
The rhizosphere is a key area for the plant metal uptake. We studied heavy metal availability in the rhizosphere and the bulk soil, the interactions between metal ions, and their effects on heavy metal uptake and accumulation by Pelargonium hortorums (geranium). A pot experiment with plants of geranium was conducted in a soil spiked with cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) singly or in combinations. Bulk soils showed higher concentrations of extractable metals than rhizosphere soils, and metals accumulated preferentially in roots relative to aerial biomass. Regression analysis showed that soil extractable Cr, Ni and Pb were related (R2 = 0.90) to their concentration in plants, but there was no correlation between soil and plants for Cd, Cu, and Zn. Larger concentrations of metals were found when they were added in combinations rather than individually, and availability and uptake were directly related to the level of metals applied.
Heavy metals (Cd, Pb, Cu, Zn) absorbed by roots brought about oxidative stress conditions through ROS
production (O2¯˙, H2O2) for pea plants cultivated hydroponically for 96 h on a Hoagland medium with the addition of 50 μM: CdCl2, Pb(NO3)2, CuSO4, and ZnSO4. We shows, using laser ablation ICP MS, that Cd, Cu, Pb,and Zn elements are located along a cross-section through the roots of pea plants. We observed increasing activitiesof antioxidative enzymes (SOD, CAT, GR) in oxidative stress conditions. We have shown changes inredox state (GSH/GSSG) in pea root grown with Pb, Cu, Cd, and Zn.
Positive effect of multiple-PGPR (Plan Growth Promoting Rhizobacteria), isolated from heavy metal contaminated soil, on the germination of Barnyard grass (Echinochloa crus-galli var. frumentacea) was quantitatively estimated in 5 heavy metal (Cd, As, Ni, Cu, and Pb) contaminated liquid medium. The value for respective heavy metal was estimated by TSK (Trimmed Speraman-Karber) model based on germination rate. The results showed overall increase in with PGPR inoculation. The value increased 1.4% from 96.0 mg/L (control) to 97.4 mg/L (PGPR-treated) in As contaminated medium. In Ni contaminated medium, the value increased 31.9% from 148.0 mg/L (control) to 195.2 mg/L (PGPR-treated), while the showed 4.8% increase from 63.4 mg/L (control) to 66.5 mg/L (PGPR-treated) in Cu medium. Overall seedling growth was stronger in the PGPR treated seeds than that in the control, but positive effect on seedling growth was not conspicuous. At effective concentration of 100 mg/L, the average seedling length of the PGPR treatment in As, Cd, Cu, and Ni medium, respectively, was 1.13, 0.14, 0.40, and 0.06 cm longer than that in the control. However, the increase of seedling growth was statistically insignificant (p < 0.05). These results suggest that inoculation of the isolated-PGPR exerts positive effects on seed germination by reducing heavy metal toxicity and can be an effective tool for application of phytoremediation on heavy metal contaminated soils.
Investigations were carried out to evaluate alterations in photosynthetic performance of Salvinia natans (L.) exposed to chromium (Cr) and zinc (Zn) rich wastewater. Accumulation of high levels of Cr and Zn in plants affected photosynthetic electron transport. Photosystem- (PS) II-mediated electron transport was enhanced in plants exposed to Cr rich wastewater while a decline was observed in Zn-exposed plants. Photosystem-I-mediated electron transport increased in plants exposed to Cr and Zn rich wastewater. Efficiency of photosystem II (Fv/Fm) measured by fluorescence did not show any significant change in Cr-exposed plants but a decrease was observed in Zn-exposed plants as compared to the control. The enhancement in PS I-induced cyclic electron transport in Cr and Zn exposed plants led to a build up of the transthylakoidal proton gradient (DpH) which subsequently helped in maintaining the photophosphorylation potential to meet the additional requirement of ATP under stress. The carbon assimilation potential was adversely affected as evident from the decrease in Rubisco (EC 4.1.1.39) activity. The alterations in photosynthetic electron transport affected stromal redox status and induced variations in the level of stromal components such as pyridine nucleotides in plants exposed to Cr and Zn rich wastewater. The present investigations revealed that alteration in the photosynthetic efficiency of Salvinia exposed to Cr could primarily be the result of a decline in carbon assimilation efficiency relative to light-mediated photosynthetic electron transport, though in the case of Zn-exposed plants both these factors were affected equally.
The effects of 50 microM cadmium (Cd) or copper (Cu) ions on the supramolecular conformation of the light-harvesting pigment-protein complex of PSII (LHCII) isolated from rye seedlings were studied. It was found that the action of these two metal ions on the LHCII structure and organization is dissimilar. The Fourier transform infrared (FTIR) measurements indicated inhibition or stimulation of formation of parallel beta-structures and aggregates in the presence of Cd or Cu ions, respectively. The Chl a fluorescence excitation spectra of LHCII extracted from Cd-treated plants showed that the decreased aggregation of complexes was correlated with a decline in efficiency of quenching of excitation energy. From the results of mass spectrometry, changes in LHCII aggregation in the presence of Cd ions might be based on decreases in the molecular mass of Lhcb1 and Lhcb2 proteins. An increase in the content of LHCII aggregates under Cu ion excess was associated with changes in the LHCII xanthophyll pigment pool. In the complexes isolated from Cu-treated plants, all-trans violaxanthin and 9'-cis neoxanthin content declined and the simultaneous appearance of the fraction of 9-cis violaxanthin was observed. 9-cis violaxanthin formation under Cu ion excess might facilitate LHCII inter-trimer interaction and, therefore, aggregation of complexes. RLS (resonance light scattering) spectra indicated that the excitonic interaction between Chl molecules and between Chls and xanthophylls was responsible for the effective dissipation of excitation energy in LHCII isolated from Cu-treated plants. Also, changes in singlet excitation energy transfer between carotenoids and Chls under the action of heavy metals were observed.
This review addresses the global problem of heavymetal pollution originating from increased industrialization and urbanization and its amelioration by using wetland plants both in a microcosm as well as natural/field condition. Heavymetal contamination in aquatic ecosystems due to discharge of industrial effluents may pose a serious threat to human health. Alkaline precipitation, ion exchange columns, electrochemical removal, filtration, and membrane technologies are the currently available technologies for heavy metal removal. These conventional technologies are not economical and may produce adverse impacts on aquatic ecosystems. Phytoremediation of metals is a cost-effective "green" technology based on the use of specially selected metal-accumulating plants to remove toxic metals from soils and water. Wetland plants are important tools for heavy metal removal. The Ramsar convention, one of the earlier modern global conservation treaties, was adopted at Ramsar, Iran, in 1971 and became effective in 1975. This convention emphasized the wise use of wetlands and their resources. This review mentions salient features of wetland ecosystems, their vegetation component, and the pros and cons involved in heavy metal removal. Wetland plants are preferred over other bio-agents due to their low cost, frequent abundance in aquatic ecosystems, and easy handling. The extensive rhizosphere of wetland plants provides an enriched culture zone for the microbes involved in degradation. The wetland sediment zone provides reducing conditions that are conducive to the metal removal pathway. Constructed wetlands proved to be effective for the abatement of heavymetal pollution from acid mine drainage; landfill leachate; thermal power; and municipal, agricultural, refinery, and chlor-alkali effluent. the physicochemical properties of wetlands provide many positive attributes for remediating heavy metals. Typha, Phragmites, Eichhornia, Azolla, Lemna, and other aquatic macrophytes are some of the potent wetland plants for heavy metal removal. Biomass disposal problem and seasonal growth of aquatic macrophytes are some limitations in the transfer of phytoremediation technology from the laboratory to the field. However, the disposed biomass of macrophytes may be used for various fruitful applications. An ecosustainable model has been developed through the author's various works, which may ameliorate some of the limitations. The creation of more areas for phytoremediation may also aid in wetlands conservation. Genetic engineering and biodiversity prospecting of endangered wetland plants are important future prospects in this regard.
This study was conducted to find out the cadmium (Cd) accumulation and tolerance of Iris pseudacorus and Acorus calamus as aquatic plants native to Korea for Cd removal in water. In the range of Cd concentration from 10 mu M to 130 mu M, the Cd lethal dose 50 (LD(50)) was 78.5 mu M in I. pseudacorus and 47.6 mu M in A. calamus. In I. pseudacorus, superoxide dismutase and peroxidase as antioxidants were relatively effective against oxidative stress caused by Cd, while catalase, superoxide dismutase, and polyphenolics were effective in A. calamus. The polyphenolics known as typical antioxidants were not detected in I. pseudacorus. In both species, the Cd accumulation in plants increased with the higher Cd concentration and the longer processing period. Also, the absorbed Cd was accumulated mainly in the roots. The amount of Cd accumulated in the shoot part was maximally 548.1 mg.kg(-1) (82.1% to Cd accumulated in the root part) in I. pseudacorus and 121.4 mg.kg(-1) (13.7%) in A. calamus, which implied that both species all were enough evaluated as Cd hyper-accumulators based on 0.01% or more Cd accumulation in the shoot. Especially I. pseudacorus showed outstanding ability to move well Cd into the shoots from the roots and high tolerance to Cd stress.
Effects of environmental conditions on the distribution of resources between generative and vegetative reproduction were considered in relation to several theories. Our objective was to study the effects of heavy pollution-induced habitat deterioration on the growth and reproduction of Betula pendula Roth trees. The length of vegetative short shoots of the birch, the chlorophyll concentration in leaves, and the reproductive effort were studied for the most polluted site - a zinc-lead dump in Welnowiec (the district of the city of Katowice) and the control site in the village of Smoleń near the town of Pilica. All the plant samples were collected from 10 microhabitats categorized on the basis of different levels of heavy metal concentrations in the topsoil. The length of the vegetative short shoots was greater than that of the trees growing at the control site. The same increasing tendency was observed in chlorophyll concentrations. The somatic cost of reproduction in Betula pendula was higher for the polluted site, presumably owing to both more intensive generative reproduction and resource limitations in the unfavorable environments.
Use of phytotoxicity of metallic compounds dates back to 1896, when the French farmers applied Bordeaux mixture (copper sulphate, lime and water) to control fungal pests (Martin and Woodcock 1983). Currently, global heavy metal (HM) pollution is a serious environmental concern. Photosynthetic functions have been invariably affected either directly or indirectly by HMs (Baszyński and Tukendorf 1984; Clijsters and Van Assche 1985; Baszytńiski 1986; Sheoran et al. 1990; Greger and Ögren 1991; Krupa and Baszyński 1985, 1995; Prasad 1995a, 1997). A critical examination of the literature reveals that HMs react with the photosynthetic apparatus at various levels of organization and architecture i.e. accumulation of metals in leaf (main photosynthetic organ); partitioning in leaf tissues like stomata, mesophyll and bundle sheath; metal interaction with cytosolic enzymes and organics; alteration of the functions of chloroplast membranes; supramolecular level action, particularly on PS II, PS I, membrane acyl lipids, and carrier proteins in vascular tissues; molecular level interactions, particularly with photosynthetic carbon reduction cycle enzymes, xanthophyll cycle and adenylates.
There are U.S. troops with a force about 290,000 strong stationed all around the world, approximately 150 countries. Among the troops, USFK has performed principal part with its stationing for 50 years against the military threat of North Korea. However, as a result of an investigation made into environmental contamination of several bases which were restituted from US to ROK by the Land Partnership Plan in the process of relocation of USFK, it was found that the area was contaminated by not only TPH and BTEX caused by diesel fuel and JP-8 but also various heavy metal over the standard level according to the operations of corps. Among these bases, 4 corps, each of which has different duties and function, were chosen to be analyzed for the characteristics and degrees of soil contamination. Fisrt of all, in armored camp the soil was contaminated by TPH and heavy metal (Zn, Ni, Pb) due to the repairing activities of tracked vehicles and shooting exercises. In army aviation camp, the soil was contaminated by TPH, BTEX and heavy metal (Zn, Cd) due to repairing activities of aircrafts. Also, in engineer camp there was contaminated area polluted by TPH and heavy metal (Zn, Pb) caused by open-air storage of various construction materials and TPH, BTEX and heavy metal (Zn, Pb, Cu) contamination of aircraft shooting area in shooting range camp were detected. Managing environment will be more effective when we identify the contaminative characteristics and take necessary measures in advance.
This study attempted to facilitate various groundcover plants, related to phytoremediation material, and advance shade plants with a heavy metal tolerance to contaminated soil in an urban shade space. Saxifraga stolonifera, which has commonly been used a landscape shade plants, was evaluated to determine its heavy metal tolerance to different concentrations(Control, , and treatment) of Cd, Pb and Zn in soil. The growth of Saxifraga stolonifera showed no significant tendency after the initial transplantation, but showed distinct changes with the respective treatment heavy metal types and concentrations over time. Especially, severe chlorosis, with more yellowish green leaves, was observed, with inhibition at Cd concentrations greater than . Conversely, no external symptoms or growth retardation were observed with Pb and Zn concentrations less than . Therefore, Saxifraga stolonifera can be applied as a long term phytoremediation species in soil contaminated with low concentrations of heavy metal in urban shade spaces.
This study was carried out in the Tropical Plant Resources Research Center of Korea National Arboretum to determine the optimum edaphic environment for the growth of tropical and subtropical plants. The physicochemical properties of artificial substrates and the growth characteristics of tropical and subtropical plants were investigated. Subtropical plants exhibited a high growth rate when cultivated in a substrate of Dry Zone that had physical properties similar to those of arid native soil. Mediterranean plants showed a low growth rate when grown in a substrate of Subtropical Zone that required changes in acidity. The substrate of Tropical Zone had high organic matter and mineral contents and therefore had good physical properties:this substrate has a good environment for the stimulation of the growth of tropical plants. Our results indicate that the chemical properties such as pH and mineral contents of most artificial substrates need to be more urgently improved than their physical properties in order to ensure better growth of tropical and subtropical plants. Initial management strategies for the construction of new tropical greenhouses were formulated, and data from monitoring studies will be continuously gathered and incorporated in the manual to keep it updated.
Inhibition of photosynthesis by heavy metals is well documented. In this review the results are compared between in vitro experiments on isolated systems (chloroplasts, enzymes -.), experiments on excised leaves and intact plants and algae in vivo. In vitro experiments suggest potential sites of heavy metal interaction with photosynthesis at several levels of organisation, which are not necessarily confirmed in vivo. Analytical data on subcellular heavy metal level are generally missing to discuss their mechanism of action in the intact organism. In the field factors such as soil characteristics and air pollution have to be taken into account for assessing the mechanism of action of heavy metals on photosynthesis in plants, growing in a polluted erea.
Creeping bentgrass plants have been grown from seeds obtained from plants subjected to cell selection for resistance to heavy metals and NaCl, and the sensitivity of the plants and seeds to cadmium, copper, zinc and lead in the soil has been assessed. The data obtained demonstrate the conservation of tolerance to the ecological factors studied in the seeds of second-generation plants. Cross-resistance to pollutants was observed in some cases. The plants obtained can be recommended for the remediation of heavy-metal contaminated soils in urban ecosystems.
The effects of cadmium ( Cd), chromium ( Cr), copper ( Cu), nickel ( Ni), lead ( Pb) and zinc ( Zn) on the growth and uptake of 10 fern species was investigated under a controlled environment in order to evaluate their suitability for phytoremediation. Fern species included Adiantum aethiopicum, Blechnum cartilagineum, Blechnum nudum, Calochlaena dubia, Dennstaedtia davallioides, Doodia aspera, Hypolepis muelleri, Nephrolepis cordifolia, Pellaea falcata and the arsenic ( As) hyperaccumulating Pteris vittata. Ferns were exposed to four levels of metals at concentrations of 0, 50, 100 and 500 mg kg(-1) for a period of 20 weeks. The response of ferns significantly varied among species and metals. In general, heavy-metal translocation was limited, with metals being absorbed and held in roots, suggesting an exclusion mechanism as part of the ferns' tolerance to the applied metals. Similar metal-accumulation patterns were observed for all species in that accumulation generally increased with increasing metal treatments; in most cases a sharp increase in metal accumulation was observed between 100 and 500 mg kg-1 treatments, suggesting a breakdown in tolerance mechanisms and unrestricted metal transport. This was corroborated by enhanced visual toxicity symptoms and a reduction in survival rates among ferns when exposed to 500 mg kg(-1) metal treatments; and to a lesser extent 100 mg kg(-1) metal treatments. Of the species investigated, N. cordifolia and H. muelleri were identified as possible candidates in phytostabilisation of Cu, Pb, Ni or Zn contaminated soils. Similarly, D. davallioides appeared favourable for use in phytostabilisation of Cu and Zn contaminated soils. These species had high survival rates and accumulated high levels of the aforementioned metals relative to other ferns investigated. Ferns belonging to the family Blechnaceae ( B. nudum, B. cartilagineum and D. aspera) and C. dubia ( Family Dicksoniaceae) were least tolerant to most metals, had a low survival rate and were classified as being unsuitable for phytoremediation purposes. Metal tolerance was also observed in P. vittata when exposed to Cd, Cr and Cu; however, no hyperaccumulation was observed.
Concentrations of the elements Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, N, Ni, P, Pb and Zn were measured in leaves of Betula pendula from the polluted areas of Wrocław, Poland and from a control site, relatively free from pollution. From the same sampled
trees, lengths of vegetative short shoots were measured to investigate the influence of environmental pollution. Length of
the vegetative short shoots of B. pendula was positively influenced by the traffic intensity and by the concentration of Co, Cu, Fe, Ni and Pb in leaves of this species.
Vegetative short shoots of B. pendula from polluted sites in Wrocław were significantly longer than that of the trees growing in a clean area. Thus, this feature
may be used as a pollution bioindicator.
The interactive effects of light intensity and controlled-release nitrogen fertilizer (CRNF) supply on growth, gas exchange, and chlorophyll (Chl) fluorescence parameters of two species of potted Hosta seedlings, original species of the genus Hosta in China, were studied. N4 (4 g of CRNF per pot), N8 (8 g of CRNF per pot), and sometimes N12 (12 g of CRNF per pot), significantly increased total dry weights, net photosynthetic rate (P
N), stomatal conductance (g
s), transpiration rate (E), the maximum quantum yield of PSII photochemistry (F
v/F
m), the maximum ratio of quantum yields of photochemical and concurrent nonphotochemical processes in PSII (F
v/F
0), actual efficiency of photochemical energy conversion in PSII under light (ΦPSII), and photochemical quenching coefficient (qP), but significantly decreased internal CO2 concentration (C
i) and nonphotochemical Chl fluorescence quenching (NPQ) compared to control plants at different growth stages of the two Hosta species in two levels of light intensities (50% of natural light (L50) and 70% of natural light (L70)). Based on the available data, we concluded that the increments in total dry weights of Hosta clausa var. ensata and Hosta ventricosa by appropriate amount of CRNF supply treatments under L50 and/or L70 light conditions are directly related to the increments in the P
N, which may be due to both stomatal and nonstomatal improvements for a longer growing time. Furthermore, there was an interaction between light intensity and CRNF supply treatments on growth and photosynthetic characteristics of the two Hosta species. The adaptability of Hosta plants with obvious stoloniferous rootstock to stronger light was higher than that of Hosta plants without obvious stoloniferous rootstock.
Plant-based remediation techniques are showing increasing promise for use in soils contaminated with organic and inorganic pollutants. Two contrasting approaches to remediation are being pursued: pollutant-stabilization and containment, where soil conditions and vegetative cover are manipulated to reduce the environmental hazard; and decontamination, where plants and their associated microflora are used to eliminate the contaminant from the soil.
Chromium pollution of freshwater is hazardous for humans and other organisms, and places a limitation on the use of polluted water sources. Phytoremediation, the use of plants to remove pollutants from the environment, is a cost-effective, environmentally friendly approach for water decontamination. To improve the efficiency of the process, it is essential to increase the current knowledge about Cr accumulation in macrophytes. Plants of Iris pseudacorus L. were treated with Cr(III) at 0.75 mM for 5 weeks to investigate Cr localization by means of transmission electron microscopy and energy dispersive X-ray analysis. Chromium induced severe ultrastructural alterations in the rhizodermis (cell wall disorganisation, thickening, plasmolysis, and electron-dense inclusions) and rhizome parenchyma (reduced cell size, cell wall detachment, vacuolation, and opaque granules). The highest Cr contents were found in the cell walls of the cortex in the roots and in the cytoplasm and intercellular spaces of the rhizome. The Cr concentration in root tissues was in the order cortex>rhizodermis>stele, whereas in the rhizome, Cr was evenly distributed. It is proposed that root and rhizome have distinct functions in the response of I. pseudacorus to Cr. The rhizodermis limits Cr uptake by means of Si deposition and cell wall thickening. The rhizome cortex generates vacuoles and granules where Cr co-occurs with S, indicating Cr sequestration by metal-binding proteins.
Pot-culture experiments were conducted to investigate the single effect of benzo[a]pyrene (B[a]P) and the joint effect of metal-B[a]P on the growth of Tagetes patula and its uptake, accumulation and dissipation of heavy metals and B[a]P. Results showed that the low concentration of B[a]P (≤10 mg kg(-1)) could facilitate plant growth and resulted in an increase in biomass at the rate of 10.0-49.7% relative to the control. There were significantly positive correlations between the concentrations of B[a]P accumulated in tissues of the plants and soil B[a]P (P<0.001). However, the occurrence of Cd, Cu and Pb had inhibitive effects on plant growth and B[a]P uptake and accumulation on the whole. T. patula still exhibited a steady feature of Cd-hyperaccumulator under combined contaminated soils. By contrast, the effectiveness of Cu and Pb absorption in the plants was very weak. Plant-promoted biodegradation of B[a]P was the dominant contribution, 79.2-92.4% and 78.2-92.9% of dissipation of B[a]P came from plant-biodegradation under single B[a]P and metal-B[a]P contaminated soils, respectively. Therefore, T. patula might be useful for phytoremediation of B[a]P and B[a]P-Cd contaminated sites.
Pteris vittata plants were grown on twenty-one UK soils contaminated with arsenic (As) from a wide range of natural and anthropogenic sources. Arsenic concentration was measured in fern fronds, soil and soil pore water collected with Rhizon samplers. Isotopically exchangeable soil arsenate was determined by equilibration with (73)As(V). Removal of As from the 21 soils by three sequential crops of P. vittata ranged between 0.1 and 13% of total soil As. Ferns grown on a soil subjected to long-term sewage sludge application showed reduced uptake of As because of high available phosphate concentrations. A combined solubility-uptake model was parameterised to enable prediction of phytoremediation success from estimates of soil As, 'As-lability' and soil pH. The model was used to demonstrate the remediation potential of P. vittata under different soil conditions and with contrasting assumptions regarding re-supply of the labile As pool from unavailable forms.
The ability of individual species to tolerate or accumulate heavy metal pollutants has been investigated widely. Although invasive species may become established more easily in disturbed environments, relatively little is known about how an ability to tolerate pollutants might give invasive species a competitive advantage. This study is part of a series of experiments investigating native and invasive species interactions with chemical pollution and other forms of disturbance. The purpose of this experiment was to investigate the effects of lead on the growth of Lythrum salicaria. We exposed plants to different concentrations of lead and measured different growth parameters, such as biomass, length, leaf number, and biomass allocation to roots. For most measures, plants grown in lead-free conditions were larger than plants exposed to lead. Plants in the low (500 mg/l) and medium (1,000 mg/l) lead treatments did not differ from each other, while plants in the high (2,000 mg/l) lead treatment were significantly smaller. However, the biomass allocation to roots was not significantly different among treatments. Although their growth is affected, individuals of Lythrum salicaria demonstrated tolerance to lead contamination, which may aid in their colonization in lead-polluted wetlands.
Wetland plants such as Typha latifolia and Phragmites australis have been indicated to show a lack of evolution of metal tolerance in metal-contaminated populations. The aim of the present study is to verify whether other common wetland plants such as Alternanthera philoxeroides and Beckmannia syzigachne, also possess the same characteristics. Lead and zinc tolerances in populations of six species collected from contaminated and clean sites were examined by hydroponics. In general, the contaminated populations did not show higher metal tolerance and accumulation than the controls. Similar growth responses and tolerance indices in the same metal treatment solution between contaminated and control populations suggest that metal tolerance in wetland plants are generally not further evolved by contaminated environment. The reasons may be related to the special root anatomy in wetland plants, the alleviated metal toxicity by the reduced rooting conditions and the relatively high innate metal tolerance in some species.
Over the past 200 years emissions of toxic heavy metals have risen tremendously and significantly exceed those from natural sources for practically all metals. Uptake and accumulation by crop plants represents the main entry pathway for potentially health-threatening toxic metals into human and animal food. Of major concern are the metalloids arsenic (As) and selenium (Se), and the metals cadmium (Cd), mercury (Hg), and lead (Pb). This review discusses the molecular mechanisms of toxic metal accumulation in plants and algae, the responses to metal exposure, as well as our understanding of metal tolerance and its evolution. The main emphasis will be on cadmium, which is by far the most widely studied of the non-essential toxic metals/metalloids. Entry via Zn2+, Fe2+, and Ca2+ transporters is the molecular basis of Cd2+ uptake into plant cells. Much less is known about the partitioning of non-essential metals and about the genes underlying the enormous diversity among plants with respect to Cd accumulation in different tissues. Numerous studies have described symptoms and responses of plants upon toxic metal exposure. Mysterious are primary targets of toxicity, the degree of specificity of responses, the sensing and the signaling events that lead to transcriptional activation. All plants apparently possess a basal tolerance of toxic non-essential metals. For Cd and As, this is largely dependent on the phytochelatin pathway. Not understood is the molecular biology of Cd hypertolerance in certain plant species such as the metallophytes Arabidopsis halleri or Thlaspi caerulescens.
Seedlings of Iris lactea var. chinensis (Fisch.) Koidz. and I. tectorum Maxim. were subjected to 0-160 mg l(-1) Cd in hydroponic system and harvested after 42 days to determine effects on root and shoot dry mass. A subset of 16-day-old seedlings was exposed to 1000 mg l(-1) Cd to characterize sub-cellular localization of Cd in root cells. The Cd contents in the shoots of I. lactea var. chinensis reached 529 microg g(-1 )dry weight (dw) at 80 mg l(-1) Cd treatment and in the shoots of I. tectorum reached 232 microg g(-1) dw at 40 mg l(-1) Cd treatment, without showing signs of visible toxicity. The Cd contents in the shoots of both two test species exceeded 100 microg g(-1), the critical value of Cd hyperaccumulator. The indices of tolerance (ITs) of I. lactea var. chinensis were higher than those of I. tectorum under 10-160 mg l(-1)Cd stress. Sub-cellular localization of Cd in root cells was evaluated using transmission electron microscopy (TEM) and Cd deposits were found in the cell walls, in the cytoplasm and on the inner surface of xylem vessels in the root tip of I. lactea var. chinensis and I. tectorum. A few cells in the root tip of I. tectorum were necrotic. The results showed that the tolerance and accumulation of Cd by I. lactea var. chinensis were higher than those of I. tectorum, suggesting that I. lactea var. chinensis has potential application in phytoremediation.
Up to now, there was no document on ornamental plants that had been applied to phytoremediation, which can remedy contaminated environment and beautify it at the same time. Thus, the growth responses and possible phytoremediation ability of three ornamental plants selected from the previous preliminary experiments were further examined under single Cd or combined Cd-Pb stress. The results showed that these tested plants had higher tolerance to Cd and Pb contamination and could effectively accumulate the metals, especially for Calendula officinalis and Althaea rosea. For C. officinalis, it grew normally in soils containing 100 mg kg(-1) Cd without suffering phytotoxicity, and the Cd concentration in the roots was up to 1084 mg kg(-1) while the Cd concentration in the shoots was 284 mg kg(-1). For A. rosea, the Cd accumulation in the shoots was higher than that in the roots when the Cd concentration in soils was <100 mg kg(-1), and reached 100 mg kg(-1) as the criteria of a Cd hyperaccumulator when the Cd concentration in soils was 100 mg kg(-1). Their accumulation and tolerance to Cd and Pb were further demonstrated through the hydroponic-culture method. And A. rosea had a great potential as a possible Cd hyperaccumulator under favorable or induced conditions. Furthermore, the interactive effects of Cd and Pb in the three ornamentals were complicated, not only additive, antagonistic or synergistic, but also related to many factors including concentration combinations of heavy metals, plant species and various parts of plants. Thus, it can be forecasted that this work will provide a new way for phytoremediation of contaminated soils.
The Gardener's Guide to Growing Hostas
- D Grenfell
Grenfell, D., 1996, The Gardener's Guide to Growing
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