Response of higher plants to lead contaminated environment

Photosynthesis, ionomics and metabolomics of the host-hemiparasite association Acacia gerrardii-Viscum schimperi

Viscum schimperi is an evergreen hemiparasitic plant that can grow on stems and branches of several tree species. It penetrates the host tissues and forms a vascular bridge (haustorium) to withdraw the nutritive resources. Its relationships with hosts remain unknown. This study aimed to investigate the physiological and biochemical attributes of the host-hemiparasite association Acacia gerrardii -Viscum schimperi . The hemiparasite exhibited 2.4- and 3.0-fold lower photosynthetic activity and water use efficiency, and 1.2- and 4.1-fold higher transpiration rate and stomatal conductance. Equally, it displayed 4.9- and 2.6-fold greater water potential and osmotic potential, and in least 3.0times more accumulated 39 K, 85 Rb and 51 V, compared to the host. Nevertheless, it had no detrimental effect on photosynthetic activity, water status and multi-element accumulations in the host. Based on metabolome profiling, V. schimperi could use xanthurenic acid and propylparaben to acquire potassium from the host, and N -1-naphthylacetamide and N -Boc-hydroxylamine to weaken or kill the distal part of the infected branch and to receive the total xylem contents. In contrast, A. gerrardii could used N -acetylserotonin, arecoline, acetophenone and 6-methoxymellein to defend against V. schimperi infection.

Lead content in weight loss food supplements

Introduction: The control and prevention of lead exposure are widely discussed topics that seem to be current health concerns for the next decades. Ingestion of lead into the human body can cause toxicity which can be acute or chronic. Possible sources of lead exposure can be, among others, water, food, drugs, and food supplements. The lead content in drugs is a strictly controlled parameter worldwide. The different Pharmacopoeias (European, British, USA) provide information about the limits for lead in every drug substance and also about the tests that should be performed. Regulation of food supplements does not require obligatory analytical control. Often, these products are not monitored to ensure the quality. At the same time, during the last two decades, the global use of dietary supplements has increased manifold.

Aim: This study aimed to analyse the presence of lead in food supplements used for weight control.

Materials and methods: We have analysed 30 different samples of food supplements for lead content. These supplements are all sold as weight loss products. The method of analysis consists of determination the lead concentration in food supplements using inductively coupled plasma mass spectrometry.

Results: We found that 4 of the analysed samples provide a lead intake of between 2.339 and 2.88 μg per day. The lead content in the other 26 samples was not significant.

Conclusions: The regulation of food supplements is rather liberal and loose. Often the exact amount of the main ingredients is not properly labeled and the purity of these products is not controlled. Food supplements are used by consumers of different ages and with different medical conditions. Our recommendation is that the lead content should be obligatorily monitored and indicated on the label of every food supplement. This would be especially useful for the prevention and control of lead exposure worldwide.

Hydrogels and Hydrogel Nanocomposites: Enhancing Healthcare through Human and Environmental Treatment

Humans are constantly exposed to exogenous chemicals throughout their life, which can lead to a multitude of negative health impacts. Advanced materials can play a key role in preventing or mitigating these impacts through a wide variety of applications. The tunable properties of hydrogels and hydrogel nanocomposites (e.g., swelling behavior, biocompatibility, stimuli responsiveness, functionality, etc.) have deemed them ideal platforms for removal of environmental contaminants, detoxification, and reduction of body burden from exogenous chemical exposures for prevention of disease initiation, and advanced treatment of chronic diseases, including cancer, diabetes, and cardiovascular disease. In this review, three main junctures where the use of hydrogel and hydrogel nanocomposite materials can intervene to positively impact human health are highlighted: 1) preventing exposures to environmental contaminants, 2) prophylactic treatments to prevent chronic disease initiation, and 3) treating chronic diseases after they have developed.

Optimization of Phytoremediation of Nickel by Alocasia puber Using Response Surface Methodology

The contamination of water by heavy metals is a worldwide environmental problem. Phytoremediation and constructed wetlands have become increasingly popular as more sustainable and environmentally friendly techniques of removing heavy metals from the wastewater. This study, therefore, investigated the phytoremediation of nickel by Alocasia puber (A. puber) in a constructed wetlands (CW) microcosm. This study identified the optimum conditions for nickel (Ni) removal from wastewater using response surface methodology (RSM) with central composite design (CCD). Two operational variables were assessed: exposure time and initial Ni concentration. The optimum conditions for the maximum removal of Ni from water were an exposure time of 10 days and 99.76 mg/L initial Ni concentration. The results indicated that 95.6% removal was achieved under the optimized conditions, with a high correlation coefficient (R2 = 0.97) between the statistical model and the experimental data. Field emission scanning electron microscopy images showed anatomical changes in the A. puber samples due to Ni exposure, and transmission electron microscopy images revealed some internal damages in the A. puber, but visual Ni toxicity symptoms, such as necrosis and chlorosis, were not observed in the A. puber. This study demonstrated that A. puber planted in a constructed wetland microcosm was able to remediate wastewater contaminated with Ni.

Effect of lead on plant availability of phosphorus and potassium in a vegetable-soil system

Two typical red soils were sequentially cultivated with celery (Apium graveolens L.) and Chinese cabbage (Brassica chinensis L.) in a greenhouse to determine the effect of lead (Pb) on plant availability of phosphorus (P) and potassium (K) in the soils. The concentrations of available P as estimated by the 0.05 mol L^-1 HCl-0.025 mol L^-1 (1/2 H₂SO₄) extraction and available K estimated by the NH₄OAc extraction method in the crop-free soils were not affected by Pb treatment. Plant P concentrations in the above-ground part of celery and Chinese cabbage exposed to Pb were either lower or showed no significant difference to the control.

Macroelements and heavy metals content in energy crops cultivated on contaminated soil under different fertilization-case studies on autumn harvest

Heavy metals (HMs) contamination of soils is a major problem occurring worldwide. Utility of energy crops for biofuel feedstock production systems offers a feasible solution for a commercial exploitation of an arable land contaminated with HMs. Experiments involved field testing of Miscanthus x giganteus and Spartina pectinata cultivated on HMs-contaminated soil with standard NPK fertilizers and commercially available microbial inoculum. Biomass yield, water content, macronutrients (N, P, K, Mg, Ca), and heavy metal (Cd, Pb, Zn) concentrations in plant shoots were assessed at the end of the first and the second growing season. Independently of the applied fertilizers, Miscanthus x giganteus produced higher biomass yield while contrary results were obtained for S. pectinata. Higher HMs content in plants influenced the status of the mineral macronutrients in particular N and K. Occurrence of hasted senescence induced by drought in the second growing season caused reduction in the concentrations of all elements (except Pb), due to earlier rhizomes relocation.

Effects of pH, initial Pb2+ concentration, and polyculture on lead remediation by three duckweed species

Various geographical duckweed isolates have been developed for phytoremediation of lead. The Pb²⁺ removal efficiency of Lemna aequinoctialis, Landoltia punctata, and Spirodela polyrhiza was investigated in monoculture and polyculture at different levels of pH and initial Pb²⁺ concentrations. L. aequinoctialis was not sensitive to the tested pH but significantly affected by initial Pb²⁺ concentration, whereas synergistic effect of pH and initial Pb²⁺ concentration on removal efficiency of L. punctata and S. polyrhiza was found. Although the majority of polycultures showed median removal efficiency as compared to respective monocultures, some of the polycultures achieved higher Pb²⁺ removal efficiencies and can promote population to remove Pb²⁺. Besides, the three duckweed strains could be potential candidates for Pb²⁺ remediation as compared to previous reports. Conclusively, this study provides useful references for future large-scale duckweed phytoremediation.

Transcriptome Changes in Hirschfeldia incana in Response to Lead Exposure

Hirschfeldia incana, a pseudometallophyte belonging to the Brassicaceae family and widespread in the Mediterranean region, was selected for its ability to grow on soils contaminated by lead (Pb). The global comparison of gene expression using microarrays between a plant susceptible to Pb (Arabidopsis thaliana) and a Pb tolerant plant (H. incana) enabled the identification of a set of specific genes expressed in response to lead exposure. Three groups of genes were particularly over-represented by the Pb exposure in the biological processes categorized as photosynthesis, cell wall, and metal handling. Each of these gene groups was shown to be directly involved in tolerance or in protection mechanisms to the phytotoxicity associated with Pb. Among these genes, we demonstrated that MT2b, a metallothionein gene, was involved in lead accumulation, confirming the important role of metallothioneins in the accumulation and the distribution of Pb in leaves. On the other hand, several genes involved in biosynthesis of ABA were shown to be up-regulated in the roots and shoots of H. incana treated with Pb, suggesting that ABA-mediated signaling is a possible mechanism in response to Pb treatment in H. incana. This latest finding is an important research direction for future studies.

Impact of Funneliformis mosseae on the growth, lead uptake, and localization of Sophora viciifolia

On the basis of a pot experiment under lead (Pb) stress, we investigated the effects of an arbuscular mycorrhizal (AM) fungus (Funneliformis mosseae) on the growth and Pb uptake of Sophora viciifolia L., and explored the Pb localization in AM roots using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that high Pb levels (500 and 1000 μg/g) inhibited the growth of S. viciifolia seedlings. Compared with the noninoculation treatment, F. mosseae inoculation decreased the Pb concentrations above- and belowground by 61.0% and 15.2%, when exposed to Pb at a concentration of 1000 μg/g. The root length, fork number, tip number, surface area, and volume of mycorrhizal S. viciifolia were higher than those of the corresponding nonmycorrhizal plants. These parameters of mycorrhizal plants increased by 220%, 219%, 157%, 225%, and 278% when plants were exposed to Pb at 1000 μg/g compared with nonmycorrhizal plants. The ratio of root length with diameters between 0-0.2 mm to the total root length significantly increased under Pb stress, and F. mosseae inoculation significantly reduced the ratio. Under Pb stress, F. mosseae increased the ratios of root length with 0.61-0.8 and 0.81-1.0 mm diameters to the total root length, indicating that F. mosseae tended to thicken the roots of S. viciifolia under Pb additions. The combined results of TEM and EDS indicated that Pb deposited in not only plant cells but also the cell walls and vacuoles of the AM fungal intracellular hyphae, thus revealing the subcellular-level mechanism of AM fungi in alleviating the Pb toxicity to the host plant.

Molecular, Biochemical and Ultrastructural Changes Induced by Pb Toxicity in Seedlings of Theobroma cacao L

Pb is a metal which is highly toxic to plants and animals, including humans. High concentrations of Pb have been observed in beans of T. cacao, as well as in its products. In this work, we evaluated the molecular, biochemical, and ultrastructural alterations in mature leaves and primary roots of seedlings of two progenies of T. cacao, obtained from seed germination in different concentrations of Pb (0, 0.05, 0.1, 0.2, 0.4, 0.8 g L^-1), in the form of Pb(NO₃)₂. The progenies resulted from self-fertilization of Catongo and a cross of CCN-10 x SCA-6. The Pb, supplied via seminal, caused alterations in the ultrastructures of the mesophyll cells and in the amount of starch grains in the chloroplasts. The dosage of substances reactive to thiobarbituric acid showed that Pb induced lipid peroxidation. The activity of guaiacol peroxidases and the expression of genes associated to synthetase of phytochelatin, SODcyt and PER increased in response to Pb. In addition, there was alteration in the expression of stress-related proteins. The progeny of CCN-10 x SCA-6 was more tolerant to Pb stress when compared to Catongo, since: (i) it accumulated more Pb in the roots, preventing its translocation to the shoot; (ii) it presented higher activity of peroxidases in the roots, which are enzymes involved in the elimination of excess of reactive oxygen species; and (iii) increased expression of the gene in the phytochelatin biosynthesis route. The results of the proteomic analysis were of paramount importance to differentiate the defense mechanisms used by both progenies of T. cacao.

Lead accumulation and tolerance of Moso bamboo (Phyllostachys pubescens) seedlings: applications of phytoremediation

A hydroponics experiment was aimed at identifying the lead (Pb) tolerance and phytoremediation potential of Moso bamboo (Phyllostachys pubescens) seedlings grown under different Pb treatments. Experimental results indicated that at the highest Pb concentration (400 μmol/L), the growth of bamboo seedlings was inhibited and Pb concentrations in leaves, stems, and roots reached the maximum of 148.8, 482.2, and 4282.8 mg/kg, respectively. Scanning electron microscopy revealed that the excessive Pb caused decreased stomatal opening, formation of abundant inclusions in roots, and just a few inclusions in stems. The ultrastructural analysis using transmission electron microscopy revealed that the addition of excessive Pb caused abnormally shaped chloroplasts, disappearance of endoplasmic reticulum, shrinkage of nucleus and nucleolus, and loss of thylakoid membranes. Although ultrastructural analysis revealed some internal damage, even the plants exposed to 400 µmol/L Pb survived and no visual Pb toxicity symptoms such as necrosis and chlorosis were observed in these plants. Even at the highest Pb treatment, no significant difference was observed for the dry weight of stem compared with controls. It is suggested that use of Moso bamboo as an experimental material provides a new perspective for remediation of heavy metal contaminated soil owing to its high metal tolerance and greater biomass.

Mathematical forecasting methods for predicting lead contents in animal organs on the basis of the environmental conditions

The main objective of this study was to determine and describe the lead transfer in the soil-plant-animal system in areas polluted with this metal at varying degrees, with the use of mathematical forecasting methods and data mining tools contained in the Statistica 9.0 software programme. The starting point for the forecasting models comprised results derived from an analysis of different features of soil and plants, collected from 139 locations in an area covering 100km(2) around a lead-zinc ore mining and processing plant ('Boleslaw'), at Bukowno in southern Poland. In addition, the lead content was determined in the tissues and organs of 110 small rodents (mainly mice) caught in the same area. The prediction models, elaborated with the use of classification algorithms, forecasted with high probability the class (range) of pollution in animal tissues and organs with lead, based on various soil and plant properties of the study area. However, prediction models which use multilayer neural networks made it possible to calculate the content of lead (predicted versus measured) in animal tissues and organs with an excellent correlation coefficient.

The role of ferredoxin:thioredoxin reductase/thioredoxin m in seed germination and the connection between this system and copper ion toxicity

Seed germination is highly sensitive to changes in the surrounding environment. This work examined the impact of imbibition with copper solution on the germination rate and behavior of some enzyme capacities involved in stress response. Chickpea (Cicer arietinum L.) seeds were germinated at 25°C in the dark for 7 days of imbibition with distilled water or an aqueous solution of chloride salt of 100 or 500μM CuCl2. The exposure of seeds to copper (Cu(2+)) induced changes in the antioxidant status. In Cu-treated seeds, the non-protein thiols (—SHNP) pool and ferredoxin:thioredoxin reductase (FTR) expression and activity increased. Cysteinyl sulfurs in the thioredoxin (Trx) function as ligands for metal ions. The accumulation of Cu(2+) inhibited seed germination and embryo growth. It appears that the FTR system mediates a novel form of redox signaling in plants under copper excess.

Arbuscular mycorrhizal fungi play a role in protecting roots of Sophora viciifolia Hance. from Pb damage associated with increased phytochelatin synthase gene expression

Understanding the influence of arbuscular mycorrhizal (AM) fungi on the expressions of the dominant plant-related genes under heavy metal (HM) stress is important for developing strategies to reclaim polluted sites. In this study, we cloned full-length cDNAs of phytochelatin synthase gene (PCS1) and Actin of Sophora viciifolia Hance., a predominant plant in Qiandongshan lead and zinc mine, by rapid amplification of cDNA ends. Consequently, we studied the response of SvPCS1 to Funneliformis mosseae inoculation under lead stress (0, 50, and 200 μM Pb(NO3)2) at different durations (1, 3, and 7 days) using quantitative reverse-transcription polymerase chain-reaction (qRT-PCR) technique. The Pb concentrations and chlorophyll fluorescence parameters were also measured to assay Pb toxicity to Sophora viciifolia. We found that Pb concentrations in roots increased with increasing Pb application and the durations; the F v /F m , F v /F o , qP, and Y(II) decreased; NPQ rose with increasing Pb concentrations; mycorrhizal symbiosis alleviated the Pb toxicity to plants; and SvPCS1 was constitutively expressed in the roots. It was also found that F. mosseae inoculation could promote the expression of SvPCS1 with the concentration ≤ 200 μM at the exposure time shorter than 7 days.

Combined effects of lead and acid rain on photosynthesis in soybean seedlings

To explore how lead (Pb) and acid rain simultaneously affect plants, the combined effects of Pb and acid rain on the chlorophyll content, chlorophyll fluorescence reaction, Hill reaction rate, and Mg(2+)-ATPase activity in soybean seedlings were investigated. The results indicated that, when soybean seedlings were treated with Pb or acid rain alone, the chlorophyll content, Hill reaction rate, Mg(2+)-ATPase activity, and maximal photochemical efficiency (F(v)/F(m)) were decreased, while the initial fluorescence (F 0) and maximum quantum yield (Y) were increased, compared with those of the control. The combined treatment with Pb and acid rain decreased the chlorophyll content, Hill reaction rate, Mg(2+)-ATPase activity, F(v)/F(m), and Y and increased F 0 in soybean seedlings. Under the combined treatment with Pb and acid rain, the two factors showed additive effects on the chlorophyll content in soybean seedlings and exhibited antagonistic effects on the Hill reaction rate. Under the combined treatment with high-concentration Pb and acid rain, the two factors exhibited synergistic effects on the Mg(2+)-ATPase activity, F 0, F v/F m, as well as Y. In summary, the inhibition of the photosynthetic process is an important physiological basis for the simultaneous actions of Pb and acid rain in soybean seedlings.

Combined effect and mechanism of acidity and lead ion on soybean biomass

Heavy metal pollution and soil acidification are serious global environmental issues. The combined pollution from acidification and heavy metal has become a new environmental issue in regions where the two issues simultaneously occur. However, studies on combined pollution are still limited. In the current study, we investigated the combined effect and mechanism of acidity and heavy metal [lead ion (Pb(2+))] on soybean biomass as well as on growth, nitrogen nutrition, and antioxidant system in soybean roots. Results showed that the combined treatment with acidity and Pb(2+) decreased the soybean biomass. At pH 4.5, the soybean biomass in the combined treatment with acidity and 0.9 mmol L(-1) Pb(2+) was lower than that in the combined treatment with acidity and Pb(2+) at 0.3 or 1.5 mmol L(-1). This result was also observed at pH 3.5 and 3.0. The combined treatment with acidity and Pb(2+) also resulted in the following consequences: root growth inhibition; decrease in nitrate, ammonium, and malondialdehyde contents; increase in nitrite reductase activity; and decrease in peroxidase activity. The extent at which the test indexes decreased/increased in the combined treatment was higher than that in the single acidity treatment. The correlation analysis results indicated that the decrease in the soybean biomass in the combined treatment with acidity and Pb(2+) resulted from the decrease in the root growth, nitrate-nitrogen assimilation, and peroxidase activity.

The effect of pre-incubation of Allium cepa L. roots in the ATH-rich extract on Pb uptake and localization

The positive influence of anthocyanin (ATH) on toxic metal-treated plant material is well documented; however, it is still not explained if it is caused by changes in element absorption and distribution. Therefore, detailed analysis of the effect of the ATH-rich extract from red cabbage leaves on Pb uptake and localization at morphological, anatomical and ultrastructural level was the goal of this study. Two-day-old adventitious roots of Allium cepa L. (cv. Polanowska) were treated for 2 h with the aqueous solution of Pb(NO3)2 at the concentration of 100 μM with or without preliminary incubation in the anthocyanin-rich extract from Brassica oleracea L. var. capitata rubra leaves (250 μM, 3 h). The red cabbage extract did not change the total Pb uptake but it enhanced the translocation of accumulated metal from roots to shoots. Within the pretreated roots, more Pb was deposited in their basal part and definitely smaller amount of the metal was bound in the apoplast of the outer layers of cortex cells. The ultrastructural analysis (transmission electron microscopy and X-ray microanalysis) revealed that the ATH-rich extract lowered the number of Pb deposits in intracellular spaces, cell wall and cytoplasm of root meristematic cells as well as in such organelles important to cell metabolism as mitochondria, plastids and nucleus. The Pb deposits were preferably localised in those vacuoles where ATH also occurred. This sequestration of Pb in vacuoles is probably responsible for reduction of metal cytotoxicity and consequently could lead to better plant growth.

The response of dark septate endophytes (DSE) to heavy metals in pure culture

Dark septate endophytes (DSE) occur widely in association with plants exposed to heavy metal stress. However, little is known about the response of DSE exposed to heavy metals. In this study, five DSE were isolated from the roots of Astragalus adsurgens Pall. seedlings growing on lead-zinc mine tailings in China. Based on morphological characteristics and DNA sequence analyses, the isolates were identified as Gaeumannomyces cylindrosporus, Paraphoma chrysanthemicola, Phialophora mustea, Exophiala salmonis, and Cladosporium cladosporioides. G. cylindrosporus was selected to explore responses to Pb stress. Scanning electron microscopic observations of G. cylindrosporus grown on solid medium revealed curling of hyphae and formation of hyphal coils in response to Pb. In contrast, in liquid medium, hyphae became thick and swollen with an increase in Pb (II) concentration. We interpret that these changes are related to the variation in cell wall components. We also demonstrated that fungal melanin content increased with the addition of Pb(II). Melanin, as an important component in the cell wall, is known to be an essential antioxidant responsible for decreasing heavy metal toxicity. We also measured the total soluble protein content and glutathione (GSH) concentrations in G. cylindrosporus and found that they initially increased and then decreased with the increase of Pb(II) concentrations. The antioxidant enzyme activities were also examined, and the results showed that superoxide dismutase (SOD) activity was significantly positively correlated with Pb(II) concentrations (r = 0.957, P<0.001). Collectively, our observations indicate that the intracellular antioxidant systems, especially fungal melanin, play an important role in abating the hazards of heavy metals.

Evidence of iron cyanides as supplementary nitrogen source to rice seedlings

The effect of iron cyanides on activities of nitrate reductase (NR) and glutamine synthetase (GS) of plants was investigated. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in the nutrient solutions containing KNO(3) or NH(4)Cl and treated with ferro-cyanide [K(4)Fe(CN)(6)] or ferri-cyanide [K(3)Fe(CN)(6)]. Total cyanide and free cyanide in solutions and in plant materials were analyzed. Activities of NR and GS in different parts of plants were assayed in vivo. Results indicated that all rice seedlings exposed to either ferro- or ferri-cyanide showed positive growth. The phyto-assimilation rates of both iron cyanide species by rice seedlings were positively correlated to the doses supplied. Seedlings grown on NO(3)(-) showed significantly higher assimilatory potential for both ferro- and ferri-cyanide than those on NH(4)(+). Rice seedlings grown on NH(4)(+)-containing nutrient solution accumulated more cyanide in plant materials, majority being in roots rather than shoots, than these grown on NO(3)(-)-containing nutrient solution, suggesting that the presence of ammonium (NH(4)(+)) in the nutrient solution caused a negative impact on botanical assimilation of both iron cyanides. Sensitivity of NR and GS in rice seedlings exposed to ferro- and ferri-cyanide was identical, where conspicuous effects were only observed at the highest concentration supplied. The evidence offered here suggests that both iron cyanides can be a supplementary source of nitrogen to plant nutrition.

Activities of nitrate reductase and glutamine synthetase in rice seedlings during cyanide metabolism

A study was conducted to investigate activities of nitrate reductase (NR) and glutamine synthetase (GS) in plants during cyanide metabolism. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in the nutrient solutions containing KNO(3) or NH(4)Cl and treated with free cyanide (KCN). Cyanide in solutions and in plant materials was analyzed to estimate the phyto-assimilation potential. Activities of NR and GS in different parts of rice seedlings were assayed in vivo. Seedlings grown on NH(4)(+) showed significantly higher relative growth rate than those on NO(3)(-) (p<0.05) in the presence of exogenous cyanide. The metabolic rates of cyanide by seedlings were all positively correlated to the concentrations supplied. A negligible difference was observed between the two treatments with nitrate and ammonium (p>0.05). Enzymatic assays showed that cyanide (≥0.97mg CN L(-1)) impaired NR activity significantly in both roots and shoots (p<0.05). The effect of cyanide on GS activity in roots was more evident at 1.93mg CN L(-1), suggesting that NR activity was more susceptible to change from cyanide application than GS activity. The results observed here suggest that the exogenous cyanide, which to a certain level has a beneficial role in plant nutrition.

Phytoremediation of the coalmine effluent

Coal mine effluent was subjected to detoxification by phytoremediation using two macrophytes Azolla pinnata and Lemna minor. Both plants were kept separately in the effluents for 7 day. The initial concentration (mg L⁻¹) of eight metals: Fe, Mn, Cu, Zn, Ni, Pb, Cr and Cd investigated in the effluent were 22.91±0.02, 9.61±1.6, 2.04±0.23, 1.03±0.15, 0.86±0.19, 0.69±0.11, 0.18±0.007 and 0.06±0.008 respectively. The initial fresh biomass of each plant was 100g. After one week, metals removed in A. pinnata-phytoremediated effluent were in the order: Mn (98%)>Fe (95.4%)>Zn (95%)>Cu (93%)>Pb (86.9%)>Cd (85%)>Cr (77.7%)>Ni (66.2%) and metal decrease in L. minor-phytoremediated effluent were: Mn (99.5%)>Cu (98.8%)>Zn (96.7%)>Ni (94.5%)>Fe (93.1%)>Cd (86.7%)>Pb (84%)>Cr (76%). Due to metal toxicity the total chlorophyll and protein contents of L. minor decreased by 29.3% and 38.55% respectively. The decrease of these macromolecules in A. pinnata was 27% and 15.56% respectively. Also, the reduction in biomass of L. minor was greater than that for A. pinnata. Based on the finding we could suggest that both the plants are suitable for bioremediation of mine effluent at the contaminated sites. However, attention for quick disposal of these metal loaded plants is urgently required.

Physiological responses and tolerance mechanisms to Pb in two xerophils: Salsola passerina Bunge and Chenopodium album L

Lead (Pb) has great toxicity to human beings and other livings. Although there are varied ways to rehabilitate the Pb contaminated area, phytoremediation of Pb pollution in arid lands is still a difficult task, it is therefore urgent to find and identify Pb tolerant plants in arid areas. The physiological responses and tolerance mechanisms to Pb stress (expressed as the Pb concentration, e.g., 0, 50, 150, 300, 600, 800, 1000 mg/L) were investigated for the xerophils Salsola passerina Bunge and Chenopodium album L. Results indicated that S. passerina exhibited higher Pb tolerance than Ch. album in terms of the seed germination rate, bio-activities of SOD and POD, and lower MDA production. There were two ways for S. passerina to reduce Pb toxicity in organism level, e.g., cell wall precipitation and state transfer of free Pb into anchorage. These findings demonstrate that S. passerina is a Pb tolerant species and may have potential application in phytoremediation of Pb contaminated arid lands.

Evaluation of lead toxicity in Erica andevalensis as an alternative species for revegetation of contaminated soils

Although revegetation using native flora is a low cost way to stabilize soil and restore the landscape contaminated with metals, little is known regarding the Pb-tolerance of many of these species. For this purpose, we evaluated the tolerance of Erica andevalensis to Pb by growing plants in nutrient solutions with increasing concentrations of Pb (up to 100 microM). Plant growth and different physiological parameters were determined to ascertain tolerance to metal stress. Additionally, an electron microscopy study coupled with EDX-analysis was performed to get clues on the Pb uptake and translocation from roots into stem and leaves. The LOEC (the lowest observed effect concentration) of Pb was 40 microM while the IC50 (inhibition concentration) was 80 microM Pb. Chemical analysis revealed a root > stem > leaf accumulation pattern. There was a severe reduction in fresh biomass and chlorophyll concentration at the highest Pb dose. The SEM-EDX study indicated that Pb was mostly located in root epidermal tissues. The blockage of Pb on the root probably avoided its toxic effects by limiting Pb transport to other tissues.

Effects of lead on the growth, lead accumulation and physiological responses of Pluchea sagittalis

This work aimed to study the process of stress adaptation in root and leaves of different developmental stages (apex, middle and basal regions) of Pluchea sagittalis (Lam.) Cabrera plants grown under exposure to five Pb levels (0, 200, 400, 600 and 1000 μM) for 30 days. Pb concentration and content in roots, stems, and leaves of different developmental stages increased with external Pb level. Consumption of nutrient solution, transpiration ratio, leaf fresh weight, leaf area, and shoot length decreased upon addition of Pb treatments. However, dry weight of shoot parts and roots did not decrease upon addition of Pb treatments. Based on index of tolerance, the roots were much more tolerant to Pb than shoots. δ-aminolevulinic acid dehydratase activity was decreased by Pb treatments, whereas carotenoid and chlorophyll concentrations were not affected. Lipid peroxidation and hydrogen peroxide concentration both in roots and leaves increased with increasing Pb levels. Pb treatments increased ascorbate peroxidase activity in all plant parts, while superoxide dismutase activity increased in leaves and did not change in roots. Catalase activity in leaves from the apex shoot was not affected by Pb, but in other plant parts it was increased. Pb toxicity caused increase in non-protein thiol groups concentration in shoot parts, whereas no significant difference was observed in roots. Both root and shoot ascorbic acid concentration increased with increasing Pb level. Therefore, it seems that Pb stress triggered an efficient defense mechanism against oxidative stress in P. sagittalis but its magnitude was depending on the plant organ and of their physiological status. In addition, these results suggest that P. sagittalis is Pb-tolerant. In conclusion, P. sagittalis is able to accumulate on average 6730 and 550 μg Pb g(-1) dry weight, respectively, in the roots and shoot, a physiological trait which may be exploited for the phytoremediation of contaminated soils and waters.

Lead induced responses of Pfaffia glomerata, an economically important Brazilian medicinal plant, under in vitro culture conditions

Plantlets of Pfaffia glomerata (Spreng.) were exposed in vitro for 30 days to five lead levels (0-400 μM) to analyze the effects on growth and oxidative stress and responses of various antioxidants vis-à-vis lead accumulation. The plantlets showed significant lead accumulation in roots (1,532 μg g(-1) DW) with a low root to shoot lead translocation (ca. 3.6%). The growth of plantlets was negatively affected by various lead treatments, although the level of photosynthetic pigments did not alter significantly in response to any lead treatment. However, plantlets suffered from oxidative stress as suggested by the significant increase in malondialdehyde levels in root (8.48 μmol g(-1) FW) and shoot (3.20 μmol g(-1) FW) tissues with increasing lead treatments. In response to the imposed toxicity, increases in the activities of catalase in root (4.14 ∆E min(-1) mg(-1) protein) and shoot (3.46 ∆E min(-1) mg(-1) protein) and superoxide dismutase in root (345.32 units mg(-1) protein) and shoot (75.26 units mg(-1) protein), respectively, were observed, while the levels of non-protein thiols and ascorbic acid were not affected significantly in either roots or shoots.

Comparative effects of native filamentous and arbuscular mycorrhizal fungi in the establishment of an autochthonous, leguminous shrub growing in a metal-contaminated soil

The aim of this study was to assess the effectiveness of inoculation with a native arbuscular mycorrhizal (AM) fungus, Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe, or a filamentous fungus, Penicillium aurantiogriseum Dierckx 1901, on the establishment of Coronilla juncea L. seedlings grown in a polluted, semiarid soil. For that, root and shoot biomass, nutrient uptake, mycorrhizal colonisation and nitrate reductase (NR) and phosphatase activities were analysed. Six months after planting, the shoot biomass of C. juncea was increased only by the inoculation with G. mosseae (by about 62% compared with non-mycorrhizal plants). The shoot NR and root acid phosphatase activities were increased more by inoculation with G. mosseae than with P. aurantiogriseum inoculation. The root NR activity and foliar nutrient contents were increased only by the inoculation with the AM fungus. The root Zn and Cu decreased with the AM fungus. In conclusion, the autochthonous AM fungus was an effective inoculant with regard to stimulating growth and alleviating heavy metal toxicity for plants growing on a soil contaminated by multiple heavy metals. Inoculation with an autochthonous, filamentous fungus does not seem to be a good strategy for phytoremediation of such problematic sites.

Lead phytotoxicity on wheat (Triticum aestivum L.) seed germination and seedlings growth

Lead (Pb) is an environmental pollutant extremely toxic to plants and other living organisms including humans. To assess Pb phytotoxicity, experiments focusing on germination of wheat seeds were germinated in a solution containing Pb (NO(3))(2) (0.05; 0.1; 0.5; 1g/L) during 6 days. Lead accumulation in seedlings was positively correlated with the external concentrations, and negatively correlated with morphological parameters of plant growth. Lead increased lipid peroxidation, enhanced soluble protein concentrations and induced a significant accumulation of proline in roots. Esterase activity was enhanced in the presence of lead, whereas α-amylase activity was significantly inhibited. Antioxidant enzymes activities, such as, ascorbate peroxidase, peroxidase, superoxide dismutase, catalase and glutathione S-transferase were generally significantly increased in the presence of lead in a dose-dependent manner. The present results thus provide a model system to screen for natural compounds able to counteract the deleterious effects of lead.

Protective effects of epigallocatechin-3-gallate against lead-induced oxidative damage

A positive association of lead exposure with clinical cardiovascular outcomes has been identified. Epigallocatechin-3-gallate (EGCG) is one of the active polyphenols in green tea, it has not been reported as an antioxidant against lead toxicity. This study was carried out to investigate whether EGCG could protect the ventricular myocytes of rats against lead-induced oxidative damage. Isolated ventricular myocytes were exposed to lead and/or EGCG, then activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) and the levels of hydroxyl radical (OH(·)), hydrogen peroxide (H(2)O(2)), and superoxide anion (O(2) (·-)) were measured. The results showed that lead induced a significant decrease of SOD and CAT activities, while the levels of MDA increased significantly. Increases in intracellular OH(·), O(2) (·-), and H(2)O(2) were found as well. These processes were concentration-dependent and statistically significant different when compared to 2.0 µM lead exposure. The activity of SOD and CAT increased while the levels of MDA and reactive oxygen species (ROS) decreased after treatment with EGCG. While there were progressive benefits with increasing EGCG concentrations, there was no statistical significance at a 30 µg/mL dose when compared with the control. These results will provide more evidence for lead toxicity to tissue, cell, and biological macromolecule.

Influences of major nutrient elements on Pb accumulation of two crops from a Pb-contaminated soil

To know about the effect of major nutrient elements on various forms of Pb and metal extraction, a greenhouse experiment was conducted to assess the effects of various major nutrient elements on Pb accumulation in two crops (Spinacia oleracea, SO and Sonchus arvensis, SA) in Changchun, China. Results indicated that, for SO, the Pb concentrations in both shoots and roots had no difference with increasing nutrients except for low nutrient treatment (1/2H). For SA, high nutrient treatments (2H and 3H) resulted in higher Pb concentrations in roots than low and standard nutrient treatments (1/2H and C), but high Pb concentration in shoot appeared in low and highest nutrient treatments (1/2H and 3H). The nitrogenous nutrient treatment (2N) had the most effect of increasing Pb concentrations in roots of SO and SA. The potassic and phosphorus nutrient treatments (2K and 2P) had little effect on the Pb concentrations in plant tissues for SO. Pb concentration in SO was lower than SA. Because of the higher total biomass in SO than SA, the ability to Pb accumulation in SO was better than SA. Sequential extraction results indicated that the addition of soil amendments transform soil Pb from bioavailable fractions to non-bioavailable fraction substantially. The results suggest that nitrogen fertilizer for SO and phosphorus fertilizer for SA are the most effective materials for the remediation of Pb-contaminated soils, and increase the tolerance of crops to Pb contamination.

Sunflower Plants as Bioindicators of Environmental Pollution with Lead (II) Ions

In this study, the influence of lead (II) ions on sunflower growth and biochemistry was investigated from various points of view. Sunflower plants were treated with 0, 10, 50, 100 and/or 500 μM Pb-EDTA for eight days. We observed alterations in growth in all experimental groups compared with non-treated control plants. Further we determined total content of proteins by a Bradford protein assay. By the eighth day of the experiment, total protein contents in all treated plants were much lower compared to control. Particularly noticeable was the loss of approx. 8 μg/mL or 15 μg/mL in shoots or roots of plants treated with 100 mM Pb-EDTA. We also focused our attention on the activity of alanine transaminase (ALT), aspartate transaminase (AST) and urease. Activity of the enzymes increased with increasing length of the treatment and applied concentration of lead (II) ions. This increase corresponds well with a higher metabolic activity of treated plants. Contents of cysteine, reduced glutathione (GSH), oxidized glutathione (GSSG) and phytochelatin 2 (PC2) were determined by high performance liquid chromatography with electrochemical detection. Cysteine content declined in roots of plants with the increasing time of treatment of plants with Pb-EDTA and the concentration of toxic substance. Moreover, we observed ten times higher content of cysteine in roots in comparison with shoots. The observed reduction of cysteine content probably relates with its utilization for biosynthesis of GSH and phytochelatins, because the content of GSH and PC2 was similar in roots and shoots and increased with increased treatment time and concentration of Pb-EDTA. Moreover, we observed oxidative stress caused by Pb-EDTA in roots where the GSSG/GSH ratio was about 0.66. In shoots, the oxidative stress was less distinctive, with a GSSG/GSH ratio 0.14. We also estimated the rate of phytochelatin biosynthesis from the slope of linear equations plotted with data measured in the particular experimental group. The highest rate was detected in roots treated with 100 μM of Pb-EDTA. To determine heavy metal ions many analytical instruments can be used, however, most of them are only able to quantify total content of the metals. This problem can be overcome using laser induced breakdown spectroscopy, because it is able to provide a high spatial-distribution of metal ions in different types of materials, including plant tissues. Data obtained were used to assemble 3D maps of Pb and Mg distribution. Distribution of these elements is concentrated around main vascular bundle of leaf, which means around midrib.

Long-term consequences of non-intentional flows of substances: modelling non-intentional flows of lead in the Dutch economic system and evaluating their environmental consequences

Substances may enter the economy and the environment through both intentional and non-intentional flows. These non-intentional flows, including the occurrence of substances as pollutants in mixed primary resources (metal ores, phosphate ores and fossil fuels) and their presence in re-used waste streams from intentional use may have environmental and economic consequences in terms of pollution and resource availability. On the one hand, these non-intentional flows may cause pollution problems. On the other hand, these flows have the potential to be a secondary source of substances. This article aims to quantify and model the non-intentional flows of lead, to evaluate their long-term environmental consequences, and compare these consequences to those of the intentional flows of lead. To meet this goal, the model combines all the sources of non-intentional flows of lead within one model, which also includes the intentional flows. Application of the model shows that the non-intentional flows of lead related to waste streams associated with intentional use are decreasing over time, due to the increased attention given to waste management. However, as contaminants in mixed primary resources application, lead flows are increasing as demand for these applications is increasing.

The Pb-hyperaccumulator aquatic fern Salvinia minima Baker, responds to Pb(2+) by increasing phytochelatins via changes in SmPCS expression and in phytochelatin synthase activity

The relationship between accumulation of Pb(2+) and the activation of chelation and metal sequestration mechanisms mediated by phytochelatins (PC) was analyzed in the Pb(2+) hyperaccumulator aquatic fern Salvinia minima, after exposure to 40microM Pb(NO(3))(2). The tissue accumulation pattern of lead and the phytochelatin biosynthesis responses were analyzed in both, S. minima submerged root-like modified fronds (here named "roots"), and in its aerial leaf-like fronds ("leaves"). S. minima roots accumulated a significantly higher concentrations of Pb(+2) than leaves did. Accumulation of Pb(2+) in roots was bi-phasic with a first uptake phase reached after 3h exposure and a second higher uptake phase reached after 24h exposure. In leaves, a single delayed, smaller uptake phase was attained only after 9h of exposure. In roots lead accumulation correlated with an increased phytochelatin synthase (PCS) activity and an enhanced PC production. A higher proportion of polymerized PC(4) was observed in both tissues of exposed S. minima plants relative to unexposed ones, although a higher concentration of PC(4) was found in roots than in leaves. PCS activity and Pb(2+) accumulation was also higher in roots than in leaves. The expression levels of the S. minima PCS gene (SmPCS), in response to Pb(2+) treatment, were also evaluated. In S. minima leaves, the accumulation of Pb(2+) correlated with a marked increase in expression of SmPCS, suggesting a transcriptional regulation in the PCS activation and PC accumulation in this S. minima tissue. However, in roots, the basal expression of SmPCS was down-regulated after Pb(2+) treatment. This fact did not correlate with the later but strong increase in both, PCS activity and PC production; suggesting that the PC biosynthesis activation in S. minima roots occurs only by post-translational activation of PCS. Taken together, our data suggest that the accumulation of PC in S. minima is a direct response to Pb(2+) accumulation, and phytochelatins do participate as one of the mechanism to cope with Pb(2+) of this Pb-hyperaccumulator aquatic fern.

Role of compost, bentonite and calcium oxide in restricting the effect of soil contamination with petrol and diesel oil on plants

The studies have been initiated to find a way to use compost, bentonite and calcium oxide in order to reduce the effect of contaminated soil with a small amount of petrol or diesel oil on the yield and nitrogen content in crop plants--spring rape and oats cultivated as the main and aftercrop. Petrol and diesel oil had a toxic effect on the growth of the plants and modified nitrogen content, with the intensity of the effect depending upon their type and dose and on the type of applied substance reducing the effect of oil derivatives. Spring rape (main crop), was more sensitive, and oats (aftercrop) was less so. Petroleum-derived substances reduced the yield of spring rape by a maximum of 73% for petrol and by as much as 99% for diesel oil. Nitrogen content was higher for spring rape than for oats and larger for petrol than for diesel oil. Adding bentonite, calcium oxide or compost to the soil contaminated with oil derivatives usually reduced the negative effect of petrol and diesel oil on plant growth and reduced the protein nitrogen content and increased the total nitrogen content in plants. Bentonite proved to be the most effective, with calcium oxide and compost slightly less so. The most positive results were obtained for spring rape as the main crop. An addition of compost, bentonite and calcium oxide to soil had a stronger modifying effect on nitrogen content in plants on soils contaminated by diesel oil than petrol.

Response mechanisms of antioxidants in bryophyte (Hypnum plumaeforme) under the stress of single or combined Pb and/or Ni

The short-term responses and mechanisms of antioxidants in moss Hypnum plumaeforme subjected to single or combined Pb and/or Ni stress has been revealed in this study, in order to clarify (1) the relationship between the stress intensity and antioxidant fluctuation, (2) the difference between single and combined stress, and (3) the possibility of biomonitoring by the application of antioxidant fluctuation under stress. The results showed that the stress induced dose dependent formation of reactive oxygen species (ROS) and subsequent lipid peroxidation. Total chlorophyll (Chl) content and superoxide dismutase (SOD) activity were initiated under lower stress but were inhibited under higher stress. Both single and combined stress decreased catalase (CAT) activity but increased peroxidase (POD) activity, indicating POD in the moss played an important role in resisting the oxidative stress induced by Pb and Ni. The accumulation of (.)O2(-) and H2O2 in H. plumaeforme was respectively related to the low activity of SOD and the decreased activity of CAT. The study indicated that Pb and Ni had synergistic effect in inducing the oxidative stress in moss H. plumaeforme, especially under the combination of high concentration of Ni (0.1, 1.0 mM) and Pb. POD and CAT activity, as well as H2O2 and MDA content, which increased or decreased regularly with a dose dependent under Pb and Ni stress, could be used as an effective indicator in moss biomonitoring, especially in the case of light pollution caused by heavy metals without the changes in the appearance of mosses.

Response of Cucumis sativus L. seedlings to Pb exposure

In this study, the effects of lead (Pb) on growth, photosynthetic pigments concentration, lipid peroxidation, electrolyte leakage percentage (ELP), protein oxidation, aminolevulinate dehydratase (ALA-D; E.C. 4.2.1.24), ascorbate peroxidase (APX; E.C. 1.11.1.11), catalase (CAT; E.C. 1.11.1.6) and superoxide dismutase (SOD; E.C. 1.15.1.1) activities, and ascorbic acid (AsA), non-protein thiol groups (NPSH) and total soluble protein concentrations in cucumber seedlings (Cucumis sativus L.) were investigated. Seedlings were grown in vitro in an agar-solidified substrate containing three Pb levels as (C2H3O2)Pb.3H2O (0, 100, 400, and 1000 µmol L-1) for 10 d. Increasing Pb concentrations in substrate enhanced Pb concentration in both roots and shoot. Pb accumulated at a higher amount in roots. Root length and total fresh weight were decreased at the two highest Pb concentrations. Cucumber showed no reduction in shoot length and total dry weight at any Pb level. The highest Pb concentration decreased water content and ALA-D activity as well as increased malondialdehyde, carbonyls and total soluble protein concentrations. Carotenoids concentration enhanced at 100 and 400 µmol Pb L-1, while chlorophyll concentration and ELP were not affected by Pb stress. Activity of APX was inhibited while the activities of CAT and SOD were increased at all Pb concentrations. AsA was enhanced at 400 and 1000 µmol Pb L-1 whereas NPSH were increased only at the highest Pb concentration. Therefore, high Pb-exposure caused oxidative stress, and the antioxidant system of the cucumber seedlings was not sufficient to revert it, contributing for growth reduction.

Can phosphate compounds be used to reduce the plant uptake of Pb and resist the Pb stress in Pb-contaminated soils?

The effects of different phosphate-amendments on lead (Pb) uptake, the activities of superoxide dismutase (SOD) and the level of malondialdehyde (MDA) in cauliflower (Brassica oleracea L.) in contaminated soils with 2500, or 5000 mg P20s/kg soil of hydroxyapatite (HA), phosphate rock (PR), single-superphosphate (SSP) and the mix of HA/SSP (HASSP) were evaluated in pot experiments. Results showed that the Pb concentrations in shoots and roots decreased by 18.3%-51.6% and 16.8%-57.3% among the treatments respectively compared to the control samples. The efficiency order of these phosphate-amendments in reducing Pb uptake was as follows: HASSP approximately equal HA > SSP approximately equal PR. With the addition of SSP, HA and the mix of HA/SSP, the SOD activity in shoot was reduced markedly (P < 0.05) compared with that in the control group. For example, the SOD activities in shoot by the treatments of HASSP, SSP, and HA in 5000 mg P2O5/kg were found to be only 51.3%, 56.2%, and 56.7%, respectively. Similar effects were also observed on the level of MDA in the shoots with a decrease in 24.5%-56.3%. The results verified the inference that phosphate compounds could be used to reduce the plant uptake of Pb and resist the Pb stress in the plant vegetated in Pb-contaminated soils.

Effect of Pb toxicity on leaf growth, physiology and ultrastructure in the two ecotypes of Elsholtzia argyi

Hydroponics experiments were conducted to study the effects of Pb on mined ecotype (ME) and non-mined ecotype (NME) of Elsholtzia argyi from Pb/Cu mining and the non-contaminated agricultural areas, respectively. The results showed that at 200 microM Pb treatment, although concentrations of Pb in leaves and stem of the ME were 2.6 and 4.5 times higher than those of the NME, these plants exhibited higher tolerance to excessive levels of Pb in the growth medium. In both the ecotypes, Pb caused inhibition of leaf growth and photosynthesis, and induced the membrane damage which was more obvious in the NME. Pb treatment decreased the activities of superoxide dismutase (SOD) and guaiacol peroxidase (G-POD) while activity of catalase (CAT) and levels of total soluble proteins (TSP), ascorbic acid (AsA) and glutathione (GSH) were significantly induced after Pb exposure, however, increase was sharp in the ME plants. Leaf ultrastructural analysis of the spongy mesophyll cells revealed that the excessive Pb concentrations caused adverse effects on chloroplast ultrastructure of both ecotypes whereby internal damage was more severe in NME. The higher tolerance to Pb displayed by ME is mainly attributed to maintenance of its leaf growth and physiology, induction of GSH and integrity of cell organelles especially chloroplast ultrastructure.

Promising role of plant hormones in translocation of lead in Sesbania drummondii shoots

Lead (Pb) accumulation in Sesbania drummondii shoots was enhanced by 654 and 415% in the presence of 100 microM IAA and 100 microM NAA, respectively, compared to control plants (Pb alone). However, when IAA or NAA was added along with EDTA, Pb accumulation further increased in shoots by 1349% and 1252%, respectively. Scanning electron microscopic observations revealed that Pb particles in both leaf and stem of Pb+EDTA+IAA and Pb+EDTA+NAA treated plants were concentrated in the region of vascular bundles. In root tissue, Pb particles were present between epidermis to stele region. Plant growth in both treatments (Pb+100 microM IAA and Pb+100 microM NAA) was comparable to control plants; however, it was significantly inhibited in the treatments containing Pb+EDTA and EDTA at concentrations of 10 microM of IAA or NAA. Moreover, the photosynthetic efficiency and strength of the treated plants were not affected in the presence of IAA or NAA and EDTA.

Potential role of NADPH-oxidase in early steps of lead-induced oxidative burst in Vicia faba roots

The mechanism of oxidative burst induced by lead in Vicia faba excised roots was investigated by luminol-dependent chemiluminescence. Results showed that lead triggered a rapid and dose-dependent increase in chemiluminescence production. In this study, specific inhibitors of putative reactive oxygen species (ROS) sources were used to determine the mechanism of lead-induced ROS generation. This generation was sensitive to dephenylene iodonium (DPI), quinacrine and imidazole, some inhibitors of the NADPH-oxidase and not inhibited by other putative ROS sources inhibitors. Data reported in this work clearly demonstrated the pivotal role of NADPH-oxidase-like enzyme in early steps of lead-induced oxidative burst. To investigate the respective implication of calmodulin and protein kinase (PK) in lead-induced NADPH-oxidase activation, excised roots were treated with the calmodulin inhibitor W7 or with the PK inhibitor staurosporine. The chemiluminescence generation inhibition by these inhibitors illustrated the role of PK in lead-induced NADPH-oxidase activation and revealed a calmodulin-dependent step. Using the calcium entry blocker La(3+) or different concentrations of calcium in the extra-cellular medium, our data highlighted the implication of Ca(2+) channel in lead-induced oxidative burst.

Effect of Pb toxicity on root morphology, physiology and ultrastructure in the two ecotypes of Elsholtzia argyi

Seed germination and hydroponics experiments were conducted to underpin the effects of Pb on mined ecotype (ME) and non-mined ecotype (NME) of Elsholtzia argyi from Pb/Cu mining areas and the non-contaminated agricultural areas, respectively. In both experiments, ME exhibited higher tolerance to excessive levels of Pb in the growth medium. Various Pb treatments caused a stimulatory effect on seed germination of both the ecotypes. Concentrations of Pb in the leaves and the stem of the ME were 2.6 and 4.5 times respectively higher than those of the NME when plants were supplied with Pb level of 200microM. Pb posed adverse effects on root morphological organization and root activity of both the ecotypes but decrease was not sharp and root activity was recovered in ME plants. Root ultrastructural studies revealed that in ME, Pb was detected as fine particles dispersed throughout the cell membrane and cell wall fraction, whereas most of the Pb was found as large aggregates deposited in the cell walls of NME plants. Comparatively better growth, higher tolerance and accumulation of Pb expressed by ME plants is mainly attributed to the maintenance of its root growth and activity as well as integrity of cell organelles.

Development of New Cd2+ and Pb2+ Lennard-Jones Parameters for Liquid Simulations

We present new Lennard-Jones parameters for Cd2+ and Pb2+ ion-water interactions and describe a general methodology to obtain these parameters for any ion. Our strategy is based on the adjustment of ion parameters to reproduce simultaneously experimental absolute hydration free energy and structural properties, namely, g(r) and coordination numbers, obtained from X-ray liquid scattering and quantum mechanical/molecular mechanical (QM/MM) calculations. The validation of the obtained parameters is made by the calculation of dynamical properties and comparing them with experimental values and theoretical results from the literature. The transferability of parameters is checked by the calculation of thermodynamic, structural, and dynamical properties cited above with four different water models. The results obtained for Cd2+ and Pb2+ show an overall agreement with reference values. The absolute hydration free energy calculated with the TIP3P, SPC/E, SPC, and TIP4P water models presents, respectively, percent differences of 3.8, 3.0, 4.3, and 7.2% for lead(II) and 9.8, 8.4, 10.2, and 14.1% for cadmium(II) when compared with experimental values. Ion-water mean distance and coordination numbers for the first coordination shell are in good agreement with experimental and QM/MM results for both ions. Cd2+ shows a lesser diffusion coefficient compared to that of Pb2+ despite its smaller atomic radius, indicating a more persistent first coordination shell for the cadmium(II) ion, a result confirmed with calculations of the mean residence time of water molecules in the first coordination shell.

Lead detoxification by coontail (Ceratophyllum demersum L.) involves induction of phytochelatins and antioxidant system in response to its accumulation

Coontail (Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1-100microM) for 1-7days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748mugPbg(-1) dw after 7d which reflected its metal accumulation ability, however most of the metal (1222microgg(-1) dw, 70%) was accumulated after 1d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC(2) and PC(3)) were synthesized to significant levels at 10 and 50microM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.

Lead contamination of an old shooting range affecting the local ecosystem--A case study with a holistic approach

The aim of this case study was to uncover the consequences of lead pellet-derived heavy lead contamination at a cast-off shooting range in southern Finland, covering aspects from soil chemistry and biology up to ecosystem level. The observed changes in the soil properties of the most contaminated areas suggest that the contamination may be disturbing processes of decomposition and nutrient mineralisation. Also two functionally important groups of soil organisms, microbes (as analysed using the PLFA analysis) and enchytraeid worms, were negatively affected by the contamination. Furthermore, there was an indication of reduced pine litter production at the contaminated areas. On the other hand, lead contamination appears not to have affected pine growth or soil-dwelling nematodes and microarthropods, and the general outlook of the whole ecosystem is that of a healthy forest. Thus, the boreal forest ecosystem studied as a whole appears to bear strong resistance to contamination, despite negative effects of lead on many of its components. This resistance may result from e.g. low bioavailability of lead, avoidance of the most contaminated soil horizons and microsites by the organisms, and functional redundancy and development of lead-tolerant populations amongst the organisms. The relative importance of these factors and the mechanisms behind them will be investigated in forthcoming studies.

Lead toxicity in Brassica pekinensis Rupr.: effect on nitrate assimilation and growth

Lead is a major heavy-metal contaminant in the environment that has various anthropogenic and natural sources. To study the phytotoxic effects of Pb on the popular vegetable Chinese cabbage (Brassica pekinensis Rupr.) via depression of nitrogen assimilation, pot culture experiments with three concentrations of treatment with Pb (0, 4, and 8 mmol/kg dry soil) were carried out. Our results demonstrated adverse effects of Pb on nitrogen assimilation and plant growth. The addition of Pb in the soil resulted in elevated accumulation of Pb in the shoots of the plants: Pb concentrations of 14.3, 202.3, and 418.2 mg/kg (DW) in the shoots were detected with the 0, 4, and 8 mmol/kg treatments, respectively. Compared to the control, Pb exposure (4 and 8 mmol/kg) significantly decreased shoot nitrate content (71% and 80% of the control), nitrate reductase activity (104% and 49% of the control), and free amino acid content (81% and 82% of the control), indicating decreased nitrogen assimilation in the plants. The effect of Pb also was shown by the progressive decline in shoot biomass with increasing Pb concentration in plant shoots and in the soil. However, at the treatment levels used in this study, lead did not induce visible toxic symptoms. The lowest-concentration Pb treatment (4 mmol/kg) stimulated chlorophyll b content but did not influence chlorophyll a content. The results suggested that the toxicity of Pb to the plants occurred at least partly via depression of nitrogen assimilation.

Assessment of comparative toxicities of lead and copper using plant assay

The acute toxicities of lead (Pb) and copper (Cu) to important crop plants Sorghum bicolor, Cucumis sativus, Triticum aestivum, and Zea mays were compared. The EC50 values (the concentration of metals in the soil that reduces the growth of shoots and roots by 50%) were derived using the Trimmed Spearman-Karber method. The EC50s-shoot (root) in mg Pb kg-1 dry soil and mg Cu kg-1 dry soil were in the range of 519 to >1280 (285-445), and 48-232 (<40-110), respectively. Those concentrations are likely to occur in some abandoned mine areas in Korea. The figures indicate that Cu is more toxic than Pb to the plants in this study, and that root growth is more sensitive to the toxicity endpoint than shoot growth in Cu- or Pb-amended soils. On the other hand, seed germination is insensitive to both Pb and Cu toxicities. The Pb- and Cu-sensitive plants were also identified. Among the plants tested, T. aestivum and S. bicolor were most sensitive to Pb and Cu, respectively. Z. mays was most resistant to both Pb and Cu. The combined effects of Pb and Cu depend on the plant species, and no general phenomenon was observed. Bioaccumulations of Pb and Cu were observed in all test species, and they are concentration-dependent. These differences in the toxicities of Pb and Cu in plant species should be taken into account in biomonitoring and ecological risk assessment.