Biomedical subjects

Maria Greger

Publications and source records attributed to Maria Greger.

16 recordsLinked to original sources

PubMed2006

Fate of cadmium in Elodea canadensis.

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

Autoradiography↗

PubMed2006

Formation of methyl mercury in an aquatic macrophyte.

In the nature, inorganic forms of mercury (Hg) may be transformed to the organic, very toxic, methyl-Hg. Occasionally methyl-Hg has been detected in plants, also so in the aquatic macrophyte water spinach (Ipomoea aquatica), which is a popular vegetable in tropical regions. The objectives of this study were to investigate if methyl-Hg is formed and/or degraded in water spinach. Water spinach plants were exposed to inorganic Hg via spiked soil or spiked nutrient solution. Tests were performed in a climate chamber and in experimental units, one for each individual plant, that were equipped with separated shoot and root compartments. Plant tissues were analysed for total- and methyl-Hg. The results showed that methyl-Hg was accumulated in water spinach, especially in young metabolically active parts, when exposed to external inorganic Hg, even at sterilized conditions. Results also showed that methyl-Hg was formed in water spinach in the absence of external Hg, i.e., during recovery in a not Hg-spiked medium following after HgCl(2)-exposure. There was however, no sign of demethylation. Summarizing, most of the Hg that is taken up by the plants is bound in the roots, but of the comparatively small amounts of Hg that reach the young growing shoots, a part will be methylated. Since the young shoots of this plant make a delicious and very appreciated vegetable, Hg in I. aquatica may contribute to human health problems.

Ipomoea↗

PubMed2006

Root penetration of sealing layers made of fly ash and sewage sludge.

Fly ash and sewage sludge are suggested materials for constructing sealing layers covering mine tailings impoundments. Little is known, however, of their effect on vegetation or resistance to root penetration. We investigate: (i) the ability of different plant species to grow in sealing layers comprising fly ash and sewage sludge, (ii) the impact on plant growth of freshly hardened fly ash compared to aged and leached ash, and (iii) the plant stress response to fly ashes of different properties. A 6-mo greenhouse study using birch (Betula pendula Roth.), Scots pine (Pinus sylvestris L.), Kentucky bluegrass (Poa pratensis L.), and willow (Salix viminalis L.) demonstrated that no roots could grow into a compacted layer consisting only of ash, while a 6:4, ash-sludge mixture admitted roots into the upper part and a 1:9, ash-sludge mixture was totally penetrated (to 15 cm in depth) by roots of willow and Scots pine. Freshly hardened ash prevented root growth more effectively than aged ash did, as was observed in tests using reed canarygrass (Phalaris arundinacea L.) and pea (Pisum sativum L.). Furthermore, extracts of highly alkaline ash were more toxic to pea in a 48-h toxicity test than less alkaline ash was. However, stress responses to diluted ash extracts of lower pH, measured as enzyme capacities in dwarf bean (Phaseolus vulgaris L.), were more related to the metal and ion contents. Root penetration of sealing layers is most effectively prevented if little sewage sludge is added, and if ash of high alkalinity is chosen.

Betula↗

PubMed2006

Influences of wetland plants on weathered acidic mine tailings.

Establishment of Carex rostrata, Eriophorum angustifolium and Phragmites australis on weathered, acidic mine tailings (pH approximately 3) and their effect on pH in tailings were investigated in a field experiment. The amendments, sewage sludge and an ashes-sewage sludge mixture, were used as plant nutrition and their influence on the metal and As concentrations of plant shoots was analysed. An additional experiment was performed in greenhouse with E. angustifolium and sewage sludge as amendments in both weathered and unweathered tailings. After one year, plants grew better in amendments containing ashes in the field, also in those plants the metal and As shoot concentrations were generally lower than in other treatments. After two years, the only surviving plants were found in sewage sludge mixed with ashes. No effect on pH by plants was found in weathered acidic mine tailings in either field- or greenhouse experiment.

Biodegradation, Environmental↗

PubMed2005

Use of iodide to enhance the phytoextraction of mercury-contaminated soil.

Low bioavailability of mercury (Hg) in soil is a restricting factor in phytoextraction of Hg-contaminated soil. Iodide is known to mobilize Hg in soil and, therefore, the aim of this study was to investigate the possibility to use iodide to increase phytoextraction of Hg. The sensitivity of willow to iodide was investigated in both hydroponics with 0-10 mM KI and in soil with 0.2 and 1 mM KI addition. The capacity to accumulate HgI(2) was compared with that of Hg(NO(3))(2) in hydroponics. Soil extractions with 0-2 mM KI were used to study mobilization of Hg in aged Hg-spiked soil. Additions of KI (0.2-1 mM) were used in pot tests with aged Hg-spiked soil as well as in field trials in an industrial Hg-contaminated soil to study whether iodide addition increased the accumulation of Hg from contaminated soil and the translocation of Hg to the shoots. The total Hg contents in plants, soils and extracts were analyzed by CVAAS. The results showed that too high KI concentration was toxic to plants. Moreover, KI was toxic to plants at lower concentrations in hydroponics than in soil additions. KI (85 microM) in hydroponics gave 50% growth decrease in terms of dry weight of shoot biomass, whereas 0.2 mM KI in soil addition could be tolerated by the plant without growth disturbance. Willow accumulated Hg from HgI(2) solution slower than that from Hg(NO(3))(2) solution. KI mobilized Hg in contaminated soil and thereby increased the bioavailability of Hg in soil. Up to 1 mM KI addition increased the Hg concentrations to about 5, 3 and 8 times, respectively, in the leaves, branches and roots. However, the Hg translocation to the shoots did not show an increase with KI addition. Only less than 1% of the total Hg accumulated in the plant was distributed in the shoots. We may conclude that iodide addition enhances the phytoextraction of Hg, however, the translocation of Hg to the shoots is still too low and therefore it will not be realistic to use this method for phytoextraction of Hg-contaminated soil in practice.

Biodegradation, Environmental↗

PubMed2005

Uptake and distribution of Zn, Cu, Cd, and Pb in an aquatic plant Potamogeton natans.

A better understanding of metal uptake and translocation by aquatic plants can be used to enhance the performance of constructed wetland systems for stormwater treatment. Specifically, this study examines whether the uptake of Zn, Cu, Cd, and Pb by Potamogeton natans is via the leaves, stems, or roots, and whether there is translocation from organs of uptake to other plant parts. Competition between the metals at uptake and at the level of the cell wall-bound part of the metals accumulated in stem and leaf tissue was also examined. The results show that Zn, Cu, Cd, and Pb were taken up by the leaves, stems, and roots, with the highest accumulation found in the roots. At the elevated metal concentrations common in stormwater the uptake of Cu, but not of Zn, Cd, or Pb, by the roots was somewhat limited at uptake due to competition with other metals. Between 24% and 59% of the metal content was bound to the cell walls of the plant. Except in the case of Pb, the cell wall-bound fraction was generally smaller in stems than in leaves. No translocation of the metals to other parts of the plant was found, except for Cd which was translocated from leaf to stem and vice versa. Dispersion of metals from sediment to water through P. natans is therefore unlikely.

Biodegradation, Environmental↗

PubMed2005

Absence of Hg transpiration by shoot after Hg uptake by roots of six terrestrial plant species.

In this paper we investigated if, and to what extent, six different plant species accumulate, translocate and emit mercury (Hg) into the air. The Hg uptake by roots, distribution of Hg to the shoot and release of Hg via shoots of garden pea, spring wheat, sugar beet, oil-seed rape, white clover and willow were investigated in a transpiration chamber. The airborne Hg was trapped in a Hopcalite trap or a gold trap. Traps and plant materials were analysed for content of Hg by CVAAS. The results show that all plant species were able to take up Hg to a large extent from a nutrient solution containing 200 microg L(-1) Hg. However, the Hg translocation to the shoot was low (0.17-2.5%) and the Hg that reached the leaves was trapped and no release of the absorbed Hg to the air was detected.

Beta vulgaris↗

PubMed2004

A new method to detect cadmium uptake in protoplasts.

The mechanism for cadmium (Cd2+) uptake into the cytosol of protoplasts from 5- to 7-day-old wheat seedlings (Triticum aestivum L. cv. Kadett) was investigated by a new method, using fluorescence microscopy and the heavy metal-specific fluorescent dye, 5-nitrobenzothiazole coumarin, BTC-5N. Cadmium fluorescence gradually increased in the cytosol of shoot and root protoplasts upon repeated additions of CdCl2 to the external medium, reflecting an uptake of Cd2+. The uptake was inhibited by calcium and potassium chloride, as well as by Verapamil and tetraethylammonium (TEA), inhibitors of calcium and potassium channels, respectively. Calcium competitively inhibited the cadmium uptake. The metabolic inhibitors vanadate and dinitrophenol partly inhibited the uptake, suggesting it was dependent on membrane potential. The results indicate that cadmium is taken up by channels permeable to both calcium and potassium. The total uptake of cadmium into the protoplasts was also detected by unidirectional flux analyses using 109Cd2+, and showed approximately the same maximal concentration of Cd2+ as the fluorescence measurements. By combining the two methods it is possible to detect both uptake into the cytosol and into the vacuole.

Biological Transport, Active↗

PubMed2004

Differences in structure of adventitious roots in Salix clones with contrasting characteristics of cadmium accumulation and sensitivity.

Various clones of Salix spp. have contrasting characteristics of accumulation, translocation to shoots and of sensitivity to cadmium (Cd). The aim was to investigate the structure of adventitious roots and find out if differences between groups of clones in root anatomy accounted for differences in relation to Cd. Stem cuttings of eight clones of Salix spp. with different combinations of high or low Cd accumulation, translocation of Cd to shoots and sensitivity to Cd, were cultivated for 3 weeks in hydroponics containing 100 micro M Ca(NO(3))(2). No Cd was added in this experiment. Equal-sized roots were selected for hand-sectioning and fluorescence staining to detect the beginning of Casparian band formation and suberin lamellae deposition in endodermis. In addition, root apices were fixed, embedded, sectioned longitudinally and transversally, and stained. The image analysis system LUCIA was used for quantitative evaluation of tissue differences. The structure of adventitious root apices showed an intermediate-open type of root apical meristem and the clones differed in organization of root apices. Clones with low accumulation of Cd and high Cd tolerance had smaller meristematic zones and more extensive vacuolation of cells in the root apices than clones characterized by high accumulation of, and high sensitivity to, Cd. The apoplastic barriers, exo- and endodermis, were developed relatively close to the apex. In both layers the first ontogenetic stage, the Casparian band development, was followed by the second stage, the suberin lamellae deposition. This process started in the endodermis, preferentially against phloem poles, which is a common phenomenon also in other plant species. However, preferential development of exodermis in the sectors against phloem poles was observed in this study for the first time in plants. Development of endodermal Casparian bands in clones characterized by high accumulation of Cd occurred more distant from the root tip than in clones with low accumulation. Furthermore, the suberin lamellae were more distant from the root tip in clones with high translocation of Cd compared with those with low translocation. This indicates that apoplastic movement of Cd into the stele and the upward translocation may vary due to the endodermal anatomy. The proportion of root apoplastic barriers, exodermis and endodermis as well as epidermis to other root tissues was significantly increased in clones with higher tolerance to Cd ions, indicating the importance of these tissues in protection of the root against toxic effects of Cd.

Journal Article↗

PubMed2003

Effects of environmental biomass-producing factors on Cd uptake in two Swedish ecotypes of Pinus sylvestris.

A factorial design was used to study direct effects of external biomass-producing factors such as light, temperature and photoperiod on cadmium (Cd) uptake and indirect effects, via change in biomass production in two ecotypes of Scots pine (Pinus silvestris). The aim was to find out if the external factors affect the Cd uptake directly or via change in biomass production, and if the effect differs between ecotypes. Seedlings were grown under 10 combinations of external factors, i.e. temperature (15 and 20 degrees C), light intensity (50 and 200 micromol photons m(-2) S(-1)), photoperiod (18 h light/8 h darkness and continuous light) and external Cd concentration (totally 1.88 and 7.50 micromol). The treatment lasted for 18 days and Cd concentrations in roots and shoots were determined by AAS. The results showed that an increased biomass production increased the total Cd uptake but had a dilution effect on the Cd concentration, especially in the root tissues. The external factors tested did not have any direct effects on the Cd untake, only in the case of Cd translocation to the shoot did the higher temperature show a direct increase, but only in the southern ecotype. The two ecotypes reacted differently in Cd uptake and translocation to the external factors studied. The relative Cd uptake creased with increasing photoperiod in the northern but not in the southern ecotype. The southern ecotype decreased the Cd concentration in the shoot with increased light intensity caused by a dilution effect due to extensive shoot growth of this ecotype. The conclusion is that the uptake in pine seedlings is mainly regulated via biomass production, and not directly by light and temperature and that resulting plant Cd contents to a certain extent depend on plant origin.

Biomass↗

PubMed2003

Aquatic and terrestrial plant species with potential to remove heavy metals from storm-water.

Remediation of storm-water polluted with heavy metals should be possible in percolation systems, ponds, or wetlands. The aim of this work was to find plant species for such systems that are efficient in the uptake of Zn, Cu, Cd, and Pb. Plants were collected from percolation and wetland areas and analyzed for heavy metal concentrations. Results showed that submersed and free-floating plants had the capacity to take up high levels of Cu, Zn, and Pb into their shoots. With roots having a concentration factor above 1, the terrestrial plants show efficient stabilization of Cd and Zn and emergent plants show corresponding stabilisation of Zn. In addition, Potamogeton natans, Alisma plantago-aquatica, and Filipendula ulmaria were used in a controlled experiment. The shoots of P. natans and the roots of A. plantago-aquatica were found to accumulate even higher concentrations of Zn, Cu, and Pb than found in the field-harvested plants. Similar results were found for Cd in shoots and Pb in roots of F. ulmaria. Our conclusion is that submersed plant species seem to be the most efficient for removal of heavy metals from storm-water.

Ecosystem↗

PubMed2002

Accumulation of heavy metals in water spinach (Ipomoea aquatica) cultivated in the Bangkok region, Thailand.

The aquatic plant water spinach (Ipomoea aquatica), either wild or cultivated, is found throughout Southeast Asia and is a widely consumed vegetable in the region. Many of the waters where I. aquatica grows serve as recipients for domestic and other types of wastewater. Because these waters contain not only nutrients, but often also a wide variety of pollutants such as heavy metals from various human activities, many people risk intoxication. To estimate the accumulation of lead (Pb), cadmium (Cd), total mercury (total Hg), and methylmercury in I. aquatica and the potential hazard to human health via consumption, nine sites for cultivation of I. aquatica in the greater Bangkok region of Thailand were sampled. At seven of the sites, I. aquatica was cultivated for the local food market. The concentrations of methylmercury, total Hg, Pb, and Cd in I. aquatica were 0.8 to 221, 12 to 2,590, 40 to 530, and < or = 10 to 123 microg/kg dry weight, respectively. At all sites at least one element showed relatively high concentrations and no reference site could be established. From threshold values for highest tolerable intake of these metals by humans and information about consumption of I. aquatica among local people, Pb and Cd concentrations in I. aquatica do not seem to be a direct threat to human health. However, concentrations of Hg were very high at some sites, and were higher in leaves (highest mean value: 1,440 microg/kg dry wt) than in stems (highest mean value: 422 microg/kg dry wt). This might be a threat, especially to children and fetuses, because Hg in I. aquatica was composed of methylmercury, partly or totally, at most sites to 11% or less and at one site from 50 to 100%. At the latter site, I. aquatica was not cultivated for the food market. Because other food sources, such as fish, may have high concentrations of methylmercury, these results indicate a need for monitoring of Hg, especially methylmercury, in different foodstuffs in the region.

Animals↗

PubMed2002

Interclonal variation of heavy metal interactions in Salix viminalis.

In the complex chemistry of soil, interactions between metals can be expected and these affect the uptake of the metals by the plants. The role of the metal-metal interaction may vary between different plants. This study was performed to investigate if variations exist in the interactions between Cd, Cu, and Zn on toxicity and accumulation of these metals in different clones of Salix viminalis. Two studies were performed. First, to study interaction at uptake, 10 clones with high or low accumulation capacity of Cd, Cu, and Zn, respectively, were treated with 0.3 microM Cd, 0.1 microM Cu, and 3 microM Zn (all three metals at the same time or separately). Second, to study the effect of one of the metals on the sensitivity of the plant to the other metals, three clones with high or low sensitivity to each of the three metals were used in a modified Weibull analysis. Examination of the results shows that interclonal variation exists in effects of metal interaction on metal accumulation and sensitivity exists. The uptake experiment showed that accumulation of Cu was decreased by the other metals, but only in clones with high Cu-accumulating properties because of decreased net uptake of Cu. The accumulation of Zn in roots was increased two- to threefold in all clones in the presence of the other metals because of a decreased translocation of Zn to the shoot. The accumulation of Cd was not changed by the presence of the other metals in any of the clones. The second experiment showed that the effect of interactions between the different metals on metal toxicity was present in all clones but appeared most frequently in the clone with high Zn resistance. Synergistic effects between Cu and Zn in the Zn-resistant clone suggested that this clone had evolved an additional site of toxic action that was absent in the other clones.

Cadmium↗

PubMedDate not supplied

Cottongrass effects on trace elements in submersed mine tailings.

Phytostabilization may limit the leakage of metals and As from submersed mine tailings, thus treatment of acid mine drainage with lime could be reduced. Tall cottongrass (Eriophorum angustifolium Honckeny) and white cottongrass (E. scheuchzeri Hoppe) were planted in pots with unlimed (pH 5.0) and limed (pH 10.9) tailings (containing sulfides) amended with sewage sludge (SS) or a bioashsewage sludge mixture (ASM). Effects of the amendments on plant growth and plant element uptake were studied. Also, effects of plant growth on elements (Cd, Cu, Pb, Zn, and As), pH, electrical conductivity (EC), and concentrations of SO4(2-), in the drainage water as well as dissolved oxygen in tailings, were measured. Both plant species grew better and the shoot element concentrations of white cottongrass were lower in SS than in ASM. Metal concentrations were lowest in drainage water from limed tailings, and plant establishment had little effect on metal release, except for an increase in Zn levels, even though SO4(2-) levels were increased. In unlimed tailings, plant growth increased SO4(2-) levels slightly; however, pH was increased and metal concentrations were low. Thus, metals were stabilized by plant uptake and high pH. Amendments or plants did not affect As levels in the drainage water from unlimed tailings. Thus, to reduce the use of lime for stabilizing metals, phytostabilization with tall cottongrass and white cottongrass on tailings is a sound possibility.

Arsenic↗

PubMedDate not supplied

Influence of nutrient levels on uptake and effects of mercury, cadmium, and lead in water spinach.

In Southeast Asia the aquatic macrophyte water spinach (Ipomoea aquatica Forsk.) is a popular vegetable that is cultivated in freshwater courses. These often serve as recipients for domestic and other sorts of wastewater that often contain a variety of pollutants, such as heavy metals. In addition, fertilizers are frequently used where water spinach is cultivated commercially for the food market. To estimate the importance of ambient nutrient concentrations for accumulation of mercury (Hg), cadmium (Cd), and lead (Pb) in water spinach, plants were exposed to nutrient solutions of different strength and with varying metal concentrations. Metal-induced toxic effects, which might possibly affect the yield of the plants, were also studied. The lower the nutrient strength in the medium was, the higher the metal concentrations that accumulated in the different plant parts and the lower the metal concentration in the medium at which metal-induced toxic effects occurred. Accordingly, internal metal concentrations in the plants were correlated to toxic effects. Plants exposed to metals retained a major proportion of the metals in the roots, which had a higher tolerance than shoots for high internal metal concentrations.

Cadmium↗

PubMedDate not supplied

Clonal differences in mercury tolerance, accumulation, and distribution in willow.

This study was performed to investigate mercury (Hg) tolerance, accumulation, and translocation within the genus Salix for the potential use of this plant to remediate Hg-contaminated sites. Six clones of willow (Salix spp.) were tested on tolerance to Hg by treating plants grown in solution culture with 0 to 15 microM HgCl(2). Results showed that willow had a large variation in its sensitivity to Hg. However, the accumulation and translocation of Hg to shoots was similar in the eight tested willow clones as shown by cold vapor atomic absorption spectrometry analysis when plants were treated with 0.5 microM HgCl(2) in a nutrient solution. The majority of total Hg accumulated was localized to the roots, whereas only 0.45 to 0.62% of the total Hg accumulated via roots was translocated to the shoots. Thus, the root system is the main tissue of willow that accumulates Hg and the majority of the Hg in the root system (80%) was bound in the cell wall.

Adaptation, Physiological↗