Solanum nigrum grown in contaminated soil: effect of arbuscular mycorrhizal fungi on zinc accumulation and histolocalisation

Zn tissue accumulation in Solanum nigrum grown in a non-contaminated and a naturally contaminated Zn matrix and the effect of inoculation with different arbuscular mycorrhizal fungi (AMF) on metal uptake were assessed. S. nigrum grown in the contaminated soil always presented higher Zn accumulation in the tissues, accumulating up to 1622 mg Zn kg(-1). The presence of both Glomus claroideum and Glomus intraradices enhanced the uptake and accumulation of Zn by S. nigrum (up to 83 and 49% higher Zn accumulation, respectively). The main deposits of the metal were found in the intercellular spaces and in the cell walls of the root tissues, as revealed by autometallography, with the inoculation with different AMF species causing no differences in the location of Zn accumulation. These findings indicate that S. nigrum inoculated with selected heavy metal tolerant AMF presents extracting and accumulating capacities, constituting a potentially suitable remediation method for Zn polluted soils.     

Application of manure and compost to contaminated soils and its effect on zinc accumulation by Solanum nigrum inoculated with arbuscular mycorrhizal fungi

Zn accumulation in Solanum nigrum grown in naturally contaminated soil in the presence of different types of organic amendments was assessed. Under the same conditions, the response of the plant to inoculation with two different isolates of arbuscular mycorrhizal fungi (AMF) (Glomus claroideum and Glomus intraradices) was also evaluated. S. nigrum grown in the non-amended soil always presented higher Zn accumulation in the tissues, with the addition of amendments inducing reductions of up to 80 and 40%, for manure and compost, respectively, and enhancing plant biomass yields. The establishment of S. nigrum in the Zn contaminated soil combined with the application of amendments led to a 70-80% reduction in the amount of Zn leached through the soil. The use of S. nigrum in combination with manure appeared as an effective method for reducing the effects of soil contamination, diminishing Zn transfer to other environmental compartments via percolation.     

Zinc accumulation in Solanum nigrum is enhanced by different arbuscular mycorrhizal fungi

Solanum nigrum was found to proliferate in sediments with high levels of metal pollution. The effect of Zn on plant growth and tissue metal accumulation was assessed. The response of the plant to the inoculation with four different isolates of arbuscular mycorrhizal fungi (AMF) (Glomus sp. BEG140, Glomus claroideum, Glomus mosseae and Glomus intraradices) was studied. While the isolates of AMF did not have a significant (P<0.05) influence on mycorrhizal colonisation, increasing Zn concentration to high levels (500 and 1000 mgkg(-1)) induced significant (P<0.05) decrease of the AMF colonisation. In general, the presence of AMF did not affect the growth and biomass of S. nigrum individuals. However, the level of metal in the matrix affected S. nigrum growth; plants grown at 100 mgkg(-1) had significantly (P<0.05) lower leaf, stem, root and total biomass than control ones and plants growing at 500 and 1000 mgkg(-1) had the significantly (P<0.05) lowest biomass. Plants inoculated with the AMF G. claroideum and G. intraradices presented significantly (P<0.05) higher Zn accumulation in all plant tissues. In general, the stem tissues had the higher Zn content while the leaves registered the lowest values, which indicate a high translocation of the metal. AMF inoculation had no significant (P<0.05) influence on the metal translocation within the plant. This study suggests that inoculation with the AMF G. claroideum or G. intraradices, can enhance the Zn accumulation in the tissues of S. nigrum, not affecting the plant translocation capacities.     

The use of maize and poplar in chelant-enhanced phytoextraction of lead from contaminated agricultural soils

Chelant-enhanced phytoextraction of heavy metals is an emerging technological approach for a non-destructive remediation of contaminated soils. The main objectives of this study were (i) to assess the extraction efficiency of two different synthetic chelating agents (ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS)) for desorbing Pb from two contaminated agricultural soils originating from a mining and smelting district and (ii) to assess the phytoextraction efficiency of maize (Zea mays) and poplar (Populus sp.) after EDTA application. EDTA was more efficient than EDDS in desorbing and complexing Pb from both soils, removing as much as 60% of Pb. Maize exhibited better results than poplar when extracting Pb from the more acidic (pH approximately 4) and more contaminated (up to 1360 mg Pb kg(-1)) agricultural soil originating from the smelting area. On the other hand, poplars proved to be more efficient when grown on the near-neutral (pH approximately 6) and less contaminated (up to 200 mg Pb kg(-1)) agricultural soil originating from the mining area. Furthermore, the addition of EDTA led to a significant increase of Pb content especially in poplar leaves, proving a strong translocation rate within the poplar plants.     

The use of NTA and EDDS for enhanced phytoextraction of metals from a multiply contaminated soil by Brassica carinata

The potential of nine different species to grow in the presence of metals (As, Cd, Cu, Pb and Zn) and to accumulate them in the shoots was assessed for each metal separately by germination and root length tests, and successively by hydroponic experiments. Of the nine species tested, Brassica carinata was the species that accumulated the highest amounts of metals in shoots without suffering a significant biomass reduction. To further evaluate the potential of B. carinata for chelant-enhanced phytoextraction of a natural, multiply metal-polluted soil (As, Cd, Cu, Pb and Zn), both hydroponic and pot experiments were carried out with nitrilotriacetic acid (NTA) or (S,S)-ethylenediamine disuccinic acid (EDDS) as complexing agents. The hydroponic study with solutions containing the five metals together showed that accumulation of Cd, Cu, Pb and Zn in shoots was higher following EDDS addition compared to NTA. EDDS was more effective than NTA in desorbing Cu, Pb and Zn from the soil, whereas As and Cd were poorly extracted. B. carinata plants were grown for 4 weeks in the multiply metal-contaminated soil and then the soil was amended with 5 mmol kg(-1) NTA or EDDS. All plants were harvested 1 week after amendment. In comparison to NTA, EDDS was more effective in enhancing the concentrations of Cu, Pb and Zn in B. carinata shoots (2- to 4-fold increase compared to the control). One week after chelant addition, the DTPA-extractable metal concentrations in the polluted soil were lower in the EDDS treatment in comparison with the NTA amendment. Even though B. carinata showed a reduced growth and a relatively low metal uptake, it demonstrated the ability to survive and tolerate the presence of more metals simultaneously.     

Enhanced phytoextraction of Pb and other metals from artificially contaminated soils through the combined application of EDTA and EDDS

Chemically enhanced phytoextraction is achieved by the application of chelates to soils. Using pot experiments, the effect of the combined application of EDTA and EDDS on the uptake of Cu, Pb, Zn and Cd by Zea mays L. was studied. Among the tested application ratios of 1:1, 1:2, and 2:1 (EDTA/EDDS), 2:1 of EDTA:EDDS was the most efficient ratio for increasing the concentrations of Cu, Pb, Zn and Cd in the shoots. The combined application of 3.33 mmol kg(-1) soil of EDTA+1.67 mmol kg(-1) soil of EDDS produced 650 mg kg(-1) of Pb in the shoots, which was 2.4 and 5.9 times the concentration of Pb in the shoots treated with 5 mmol kg(-1) of EDTA and EDDS alone, respectively. The total phytoextraction of Pb reached 1710 microg kg(-1) soil, which was 2.1 and 6.1 times the total Pb from 5 mmol kg(-1) EDTA and EDDS alone, respectively. The combined application of EDTA and EDDS also significantly increased the translocation of Pb from the roots to the shoots. The mechanism of enhancing the phytoextraction of Pb by the combined application of EDTA+EDDS did not involve a change in the pH of the soil. The increase in the phytoextraction of Pb by the shoots of Z. mays L. was more pronounced than the increase of Pb in the soil solution with the combined application of EDTA and EDDS. It was thought that the major role of EDDS might be to increase the uptake and translocation of Pb from the roots to the shoots of plants.     

Zinc and cadmium accumulation and tolerance in populations of Sedum alfredii

To investigate the variation of Zn and Cd accumulation and tolerance of Sedum alfredii (a newly reported Zn/Cd hyperaccumulator), field surveys and hydroponic experiments were conducted among three populations of this species: two originating from old Pb/Zn mines in Zhejiang (ZJ) and Hunan (HN) Provinces and one from a "clean" site in Guangdong (GD) Province, China. Under field conditions, up to 12,524 and 12,253 mg kg(-1) Zn, and 1400 and 97 mg kg(-1) Cd in shoots of ZJ and HN plants were recorded respectively. Under hydroponic conditions, ZJ and HN plants accumulated significantly higher Zn and Cd in their leaves and stems, and possessed significantly higher Zn and Cd tolerance than GD plants. Among the two contaminated populations, ZJ plants showed higher Cd tolerance and accumulation (in leaves) than HN plants. The present results indicate that significant differences in Zn and Cd accumulation and tolerance exist in populations of S. alfredii.     

The influence of EDDS on the uptake of heavy metals in hydroponically grown sunflowers

Phytoextraction is an environmentally friendly in situ technique for cleaning up metal contaminated land. Unfortunately, efficient metal uptake by remediation plants is often limited by low phytoavailability of the targeted metals. Chelant assisted phytoextraction has been proposed to improve the efficiency of phytoextraction. Phytoremediation involves several subsequent steps: transfer of metals from the bulk soil to the root surfaces, uptake into the roots and translocation to the shoots. Nutrient solution experiments address the latter two steps. In this context we investigated the influence of the biodegradable chelating agent SS-EDDS on uptake of essential (Cu and Zn) and non-essential (Pb) metals by sunflowers from nutrient solution. EDDS was detected in shoots and xylem sap for the first time, proving that it is taken up into the above ground biomass of plants. The essential metals Cu and Zn were decreased in shoots in the presence of EDDS whereas uptake of the non-essential Pb was enhanced. We suggest that in the presence of EDDS all three metals were taken up by the non-selective apoplastic pathway as the EDDS complexes, whereas in the absence of EDDS essential metal uptake was primarily selective along the symplastic pathway. This shows that synthetic chelating agents do not necessarily increase uptake of heavy metals, when soluble concentrations are equal in the presence and absence of chelates.     

Zn, Cd and Pb accumulation and arbuscular mycorrhizal colonisation of pennycress Thlaspi praecox Wulf. (Brassicaceae) from the vicinity of a lead mine and smelter in Slovenia

Significant hyperaccumulation of Zn, Cd and Pb in field samples of Thlaspi praecox Wulf. collected from a heavy metal polluted area in Slovenia was found, with maximal shoot concentrations of 14,590 mg kg(-1) Zn, 5960 mg kg(-1) Cd and 3500 mg kg(-1) Pb. Shoot/root ratios of 9.6 for Zn and 5.6 for Cd show that the metals were preferentially transported to the shoots. Shoot bioaccumulation factors exceeded total soil Cd levels 75-fold and total soil Zn levels 20-fold, further supporting the hyperaccumulation of Cd and Zn. Eighty percent of Pb was retained in roots, thus indicating exclusion as a tolerance strategy for Pb. Low level colonisation with arbuscular mycorrhizal fungi (AMF) of a Paris type was observed at the polluted site, whereas at the non-polluted site Arum type colonisation was more common. To our knowledge this is the first report of Cd hyperaccumulation and AMF colonisation in metal hyperaccumulating T. praecox.     

Chelate-induced phytoextraction of metal polluted soils with Brachiaria decumbens

Chelate-induced phytoextraction with high biomass plant species has been proposed for the clean-up of heavy metal polluted soils. In the current work, the effect of the application of two different chelating agents, i.e. EDTA and EDDS, on the metal phytoextraction capacity of Brachiaria decumbens was studied. Although EDTA was, in general, more effective in soil metal solubilization, EDDS, a chelate less harmful to the environment, was more efficient inducing metal accumulation in B. decumbens shoots than EDTA. Indeed, in a moderately heavy metal polluted soil, EDDS caused a 2.54, 2.74 and 4.30-fold increase in Cd, Zn, and Pb shoot metal concentration, respectively, as compared to control plants. In this same soil, EDTA caused a 1.77, 1.11 and 1.87-fold increase in Cd, Zn, and Pb shoot metal concentration, respectively, as compared to control plants. EDDS was also more effective than EDTA in stimulating the translocation of metals from roots to shoots. B. decumbens plants were able to grow in the metal polluted soils showing no visible symptoms of phytotoxicity, which suggests their metal tolerance. Finally, B. decumbens, a fast-growing, high biomass, aluminum tolerant plant species, that has a well-established agronomic system, fulfills most of the requirements for chemically-induced phytoextraction.     

Removal of heavy metals from a metaliferous water solution by Typha latifolia plants and sewage sludge compost

Typha latifolia plants, commonly known as cattails, were grown in a mixture of mature sewage sludge compost, commercial compost and perlite (2:1:1 by volume). Four Groups (A, B, C and D) were irrigated (once every two weeks) with a solution containing different concentrations of Cu, Ni, and Zn, where in the fifth (group M) tap water was used. At the end of the 10 weeks experimental period substrate and plants were dried, weighed and analysed for heavy metals. The amounts of all three metals removed from the irrigation solution, were substantial. In the roots and leaves/stems of T. latifolia the mean concentration of Zn reached values of 391.7 and 60.8 mg/kg of dry weight (d.w.), respectively. In the substrate of Group D all three metals recorded their highest mean concentrations of 1156.7 mg/kg d.w. for Cu, 296.7 mg/kg d.w. for Ni and 1231.7 mg/kg d.w. for Zn. Linear correlation analyses suggested that there was a linear relationship between the concentration of metals in the solutions and the concentration of metals in the substrates at the end of the experiment. The percentage removal of the metals in the substrate was large, reaching 100% for Cu and Zn in some groups and almost 96% for Ni in group D. The total amount of metals removed by the plants was considerably smaller than that of the substrate, due mainly to the small biomass development. A single factor ANOVA test (5% level) indicated that the build up in the concentration of metals in the roots and the leaves/stems was due to the use of metaliferous water solution and not from the metals pre-existing in the substrate. The contribution of the plants (both roots and leaves/stems) in the removing ability of the system was less than 1%.     

Growth and trace metal accumulation of two Salix clones on sediment-derived soils with increasing contamination levels

The growth and metal uptake of two willow clones (Salix fragilis 'Belgisch Rood' and Salix viminalis 'Aage') was evaluated in a greenhouse pot experiment with six sediment-derived soils with increasing field Cd levels (0.9-41.4 mg kg-1). Metal concentrations of eight elements were measured in roots, stems and leaves and correlated to total and soil water metal concentrations. Dry weight root biomass, number of leaves and shoot length were measured to identify eventual negative responses of the trees. No growth inhibition was observed for both clones for any of the treatments (max. 41.4 mg kg-1 Cd, 1914 mg kg-1 Cr, 2422 mg kg-1 Zn, 655 mg kg-1 Pb), allowing their use for phytoextraction on a broad range of contaminated sediments. However, dry weight root biomass and total shoot length were significantly lower for S. viminalis compared to S. fragilis for all treatments. Willow foliar Cd concentrations were strongly correlated with soil and soil water Cd concentrations. Both clones exhibited high accumulation levels of Cd and Zn in aboveground plant parts, making them suitable subjects for phytoextraction research. Cu, Cr, Pb, Fe, Mn and Ni were found mainly in the roots. Bioconcentration factors of Cd and Zn in the leaves were highest for the treatments with the lowest soil Cd and Zn concentration.     

Contrasting behaviour of cadmium and zinc in a soil-plant-arthropod system

This study investigates the transfer of Cd and Zn from a soil amended with sewage sludge at rates up to 100 t ha(-1) through a multi-trophic system consisting of barley, the aphid Sitobion avenae and the larvae of the lacewing Chrysoperla carnae. Results show marked differences in the transfer of the two metals. Cadmium was freely accumulated in barley roots, but accumulation in the shoot was restricted to a concentration of around 0.22 mg kg(-1) (dry weight). This limited the transfer of Cd to higher trophic levels and resulted in no significant accumulation of Cd in S. avenae or in C. carnae. Zinc transfer in the system was largely unrestricted, resulting in significant accumulation in roots and shoots, in S. avenae and in C. carnae. Cadmium biomagnification occurred in lacewing pupae, with concentrations up to 3.6 times greater than in aphids. S. avenae biomagnified Zn by a factor of ca. 2.5 at low sludge amendment rates, but biomagnification decreased to a factor of 1.4 at the highest amendment rate. Biomagnification of Zn did not occur in C. carnae, but concentrations were up to 3.5 time higher than in soil. Results are discussed in light of the mechanisms regulating transfer of the two metals in the system.     

Cadmium uptake and translocation in tumbleweed (Salsola kali), a potential Cd-hyperaccumulator desert plant species: ICP/OES and XAS studies

Cadmium is a heavy metal, which, even at low concentrations, can be highly toxic to the growth and development of both plants and animals. Plant species vary extensively in their tolerance to excess cadmium in a growth medium and very few cadmium-tolerant species have been identified. In this study, tumbleweed plants (Salsola kali) grown in an agar-based medium with 20 mgl(-1) of Cd(II) did not show phytotoxicity, and their roots had the most biomass (4.5 mg) (P < 0.05) compared to the control plants (2.7 mg) as well as other treated plants. These plants accumulated 2696, 2075, and 2016 mg Cd kg(-1) of dry roots, stems, and leaves, respectively. The results suggest that there is no restricted cadmium movement in tumbleweed plants. In addition, the amount of Cd found in the dry leaf tissue suggests that tumbleweed could be considered as potential cadmium hyperaccumulating species. X-ray absorption spectroscopy studies demonstrated that in roots, cadmium was bound to oxygen while in stems and leaves, the metal was attached to oxygen and sulfur groups. This might imply that some small organic acids are responsible for Cd transport from roots to stems and leaves. In addition, it might be possible that the plant synthesizes phytochelatins in the stems, later coordinating the absorbed cadmium for transport and storage in cell structures. Thus, it is possible that in the leaves, Cd either exists as a Cd-phytochelatin complex or bound to cell wall structures. Current studies are being performed in order to elucidate the proposed hypothesis.     

Antioxidative responses to arsenic in the arsenic-hyperaccumulator Chinese brake fern (Pteris vittata L.)

This study measured antioxidative responses of Chinese brake fern (Pteris vittata L.) upon exposure to arsenic (As) of different concentrations. Chinese brake fern was grown in an artificially-contaminated soil containing 0 to 200 mg As kg(-1) (Na2HAsO4) for 12 weeks in a greenhouse. Soil As concentrations at < or =20 mg kg(-1) enhanced plant growth, with 12-71% biomass increase compared to the control. Such beneficial effects were not observed at >20 mg As kg(-1). Plant As concentrations increased with soil As concentrations, with more As being accumulated in the fronds (aboveground biomass) than in the roots and with maximum frond As concentration being 4675 mg kg(-1). Arsenic uptake by Chinese brake enhanced uptake of nutrient elements K, P, Fe, Mn, and Zn except Ca and Mg, whose concentrations mostly decreased. The contents of non-enzymatic antioxidants (glutathione, acid-soluble thiol) followed similar trends as plant As concentrations, increasing with soil As concentrations, with greater contents in the fronds than in the roots especially when exposed to high As concentrations (>50 mg kg(-1)). The activities of enzymatic antioxidants (superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase) in Chinese brake followed the same trends as plant biomass, increasing with soil As up to 20 mg kg(-1) and then decreased. The results indicated though both enzymatic and non-enzymatic antioxidants played significant roles in As detoxification and hyperaccumulation in Chinese brake, the former is more important at low As exposure (< or =20 mg kg(-1)), whereas the latter is more critical at high As exposure (50-200 mg kg(-1)).     

The role of arbuscular mycorrhiza in zinc uptake by red clover growing in a calcareous soil spiked with various quantities of zinc

Three pot experiments were conducted to investigate the role of arbuscular mycorrhiza (AM) in Zn uptake by red clover. Plants inoculated with Glomus mosseae and uninoculated controls were grown in a sterile calcareous soil in 'Plexiglas' (Acrylic) containers with two nylon net partitions (30 microm mesh) to separate the central root zone from the two outer hyphal zones. The effects of mycorrhiza on plant growth and Zn uptake changed dramatically with increasing Zn addition level (range 0-1200 mg kg(-1)) in the root zone. With Zn addition levels <300 mg kg(-1), added Zn did not affect plant yield and above the critical level plant yield gradually decreased but was always higher for mycorrhizal than for controls. Below the critical Zn application rate (50 mg kg(-1)), Zn uptake was enhanced while above this level Zn translocation to the shoots decreased. At all Zn addition levels, mycorrhizal colonization increased Zn absorption and accumulation in the roots, and this may help to explain the alleviation of Zn toxicity at high Zn application rates. As expected, AM colonization enhanced P nutrition and hence yield at all added Zn levels studied. Efforts were made to obtain direct evidence for hyphal contribution to Zn uptake by applying both Zn to the hyphal growth zone and additional P to the root zone to avoid the 'growth dilution effect'. The data demonstrate that mycorrhizal hyphae could absorb Zn directly from the soil and then transfer it to the plant roots. The hyphal contribution to Zn uptake by the host plant reached its maximum value at the Zn addition level of 50 mg kg(-1), in which Zn uptake via the extramatrical hyphae comprised 22% of total uptake, thus confirming the critical Zn application level found previously.     

Influence of early stages of arbuscular mycorrhiza on uptake of zinc and phosphorus by red clover from a low-phosphorus soil amended with zinc and phosphorus

In a pot experiment, red clover (Trifolium pratense) was grown in sterilized Zn-amended low available P soil (0, 50 or 400 mg Zn kg(-1)) with or without 100 mg kg(-1) added P and with or without inoculation with the arbuscular mycorrhizal (AM) fungus G. mosseae. When the plants were harvested after 40 days, AM colonization of the roots was still at an early stage, with only 14-38% of total root length colonized on average. AM colonization was highest in low-P soil, and was lowest in soil amended with 400 mg Zn kg(-1). Shoot yields were highest in AM plants with added P, but root yields were unaffected by AM inoculation. Shoot and root yields were higher with 100 mg added P kg(-1) soil, but lower with 400 mg Zn kg(-1) than 50 mg Zn kg(-1) or controls unamended with Zn. Shoot and root P concentrations were seldom higher in AM plants, but shoot P offtakes were higher in AM plants with added P. Concentrations of Zn and Cu were much higher in the roots than in the shoots. Shoot and root Zn and shoot Cu were lower, but root Cu was higher, in AM plants. Soil residual pH after plant growth was higher in AM treatments, and residual total Zn was also higher, indicating lower Zn uptake by AM plants. Soil solution pH was higher in AM treatments, and soil solution Zn was lower in the presence of mycorrhiza. The results are discussed in terms of AM protection of the plants against excessive shoot Zn uptake.     

Effect of EDTA and NTA on cadmium distribution and translocation in Pennisetum purpureum Schum cv. Mott

The primary objective of this research was to investigate the cadmium (Cd) distribution in Pennisetum purpurem (Napier grass) in the presence of 30 mg/L of Cd and different types and concentrations of chelating agents (ethylenediaminetetraacetic acid disodium dihydrate (EDTA), nitrilotriacetic acid (NTA), and EDTA-NTA mixtures). Plant samples were collected every 15 d during a 105-d experimental period. Accumulation of Cd in each part of the plant was determined using atomic absorption spectrometer (AAS), and the distribution of Cd was determined by laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) and synchrotron radiation micro X-ray fluorescence (SR-micro-XRF). The highest concentrations of Cd accumulation of 889?±?53 mg kg^?1 in the underground part (roots) and 265?±?26 mg kg^?1 in the aboveground part (stems and leaves) in the presence of 1:1 M ratio of Cd:EDTA after 30 d of exposure were observed. Plants grown in the presence of either NTA or EDTA-NTA mixtures showed significant lower Cd accumulation levels. The LA-ICP-MS analysis showed that Cd was primarily accumulated in the aboveground part (stems and leaves), especially in the xylem and intercalary meristem. In addition, translocation factor was very low. Thus, P. purpurem could be considered as a candidate plant for cadmium phytostabilization.

     

Trace element accumulation in woody plants of the Guadiamar Valley, SW Spain: a large-scale phytomanagement case study

Phytomanagement employs vegetation and soil amendments to reduce the environmental risk posed by contaminated sites. We investigated the distribution of trace elements in soils and woody plants from a large phytomanaged site, the Guadiamar Valley (SW Spain), 7 years after a mine spill, which contaminated the area in 1998. At spill-affected sites, topsoils (0-25 cm) had elevated concentrations of As (129 mg kg(-1)), Bi (1.64 mg kg(-1)), Cd (1.44 mg kg(-1)), Cu (115 mg kg(-1)), Pb (210 mg kg(-1)), Sb (13.8 mg kg(-1)), Tl (1.17 mg kg(-1)) and Zn (457 mg kg(-1)). Trace element concentrations in the studied species were, on average, within the normal ranges for higher plants. An exception was white poplar (Populus alba), which accumulated Cd and Zn in leaves up to 3 and 410 mg kg(-1) respectively. We discuss the results with regard to the phytomanagement of trace element contaminated sites.     

Effects of arbuscular mycorrhizal inoculation on uranium and arsenic accumulation by Chinese brake fern (Pteris vittata L.) from a uranium mining-impacted soil

A glasshouse experiment was conducted to investigate U and As accumulation by Chinese brake fern, Pteris vittata L., in association with different arbuscular mycorrhizal fungi (AMF) from a U and As contaminated soil. The soil used contains 111 mg U kg(-1) and 106 mg As kg(-1). P. vittata L. was inoculated with each of three AMF, Glomus mosseae, Glomus caledonium and Glomus intraradices. Two harvests were made during plant growth (two and three months after transplanting). Mycorrhizal colonization depressed plant growth particularly at the early stages. TF (transfer factor) values for As from soil to fronds were higher than 1.0, while those for roots were much lower. Despite the growth depressions, AM colonization had no effect on tissue As concentrations. Conversely, TF values for U were much higher for roots than for fronds, indicating that only very small fraction of U was translocated to fronds (less than 2%), regardless of mycorrhizal colonization. Mycorrhizal colonization significantly increased root U concentrations at both harvests. Root colonization with G. mosseae or G. intraradices led to an increase in TF values for U from 7 (non-inoculation control) to 14 at the first harvest. The highest U concentration of 1574 mg kg(-1) was recorded in roots colonized by G. mosseae at the second harvest. The results suggested that P. vittata in combination with appropriate AMF would play very important roles in bioremediation of contaminated environments characterized by a multi-pollution.