Potential of Sonchus Arvensis for the Phytoremediation of Lead-Contaminated Soil

Sonchus arvensis is one of the pioneer plant species that were found in the abandoned Bo Ngam Pb mine in Thailand. S. arvensis was collected from three sites. The highest Pb shoot concentration was 9317 mg kg^?1 and the highest translocation factor (TF) and bioaccumulation factor (BF) values were 2.5 and 6.0, respectively. To investigate Pb uptake capacity of S. arvensis, a hydroponic experiment was performed for 15 d. S. arvensis exposed to 5 mg L^?1 Pb solution had the highest Pb shoot accumulation (849 mg kg^?1). In a pot study, S. arvensis was grown in Pb mine soils amended with organic and inorganic fertilizers for 2 mo. The addition of organic fertilizer to the soil increased plant dry biomass sharply. All treatments with ethylene-diamine-tetra-acetic acid (EDTA) had Pb accumulation in shoots greater than 1000 mg kg^?1 and the highest Pb shoot accumulation was found in S. arvensis grown in soil amended with organic fertilizer and EDTA (1397 mg kg^?1). In a field trial study, S. arvensis was grown at three sites in the mine area for 6 mo. S. arvensis could tolerate a total Pb of 100,000 mg kg^?1 in the soil and accumulated Pb in the shoots up to 3664 mg kg^?1 with high TF (2.19) and BF (2.38) values. These results suggest that S. arvensis is a good candidate for Pb phytoremediation.     

Comparison of root absorption, translocation and tolerance of arsenic in the hyperaccumulator Pteris vittata and the nonhyperaccumulator Pteris tremula

* Several fern species can hyperaccumulate arsenic, although the mechanisms are not fully understood. Here we investigate the roles of root absorption, translocation and tolerance in As hyperaccumulation by comparing the hyperaccumulator Pteris vittata and the nonhyperaccumulator Pteris tremula. * The two species were grown in a pot experiment with 0-500 mg As kg-1 added as arsenate, and in a short-term (8 h) uptake experiment with 5 microM arsenate under phosphorus-sufficient conditions. * In the pot experiment, P. vittata accumulated up to 2500 mg As kg-1 frond d. wt and suffered no phytotoxicity. P. tremula accumulated<100 mg As kg-1 frond d. wt and suffered severe phytotoxicity with additions of >or=25 mg As kg-1. In the short-term uptake experiment, P. vittata had a 2.2-fold higher rate of arsenate uptake than P. tremula, and distributed more As taken up to the fronds (76%) than did P. tremula (9%). * Our results show that enhanced root uptake, efficient root-to-shoot translocation, and a much elevated tolerance through internal detoxification all contribute to As hyperaccumulation in P. vittata.     

Interaction of arsenic and phosphate on their uptake and accumulation in Chinese brake fern

Interactive effects of arsenate (As (V)) and phosphate (Pi) were investigated under hydroponic culture. Arsenic concentrations in fronds and roots of Chinese brake fern (Pteris vittata L.) significantly (p < 0.05) increased with increasing As (V), but decreased (p < 0.05) with increasing Pi in nutrient solution. Phosphate uptake was significantly (p < 0.05) inhibited by 1000 micromol L(-1) As (V). Under 100 micromol L(-1) As (V), frond phosphorus (P) increased at 100 and 1000 micromol L(-1) Pi, and root P increased at 250 micromol L(-1) Pi exposures. Arsenic and P concentrations in fronds and roots of Chinese brake fern were negatively correlated (p < 0.05). Arsenate treatments enhanced As and P transport to fronds, while increasing Pi inhibited their transportation, with highest frond P and As (%) obtained under 100 micromol L(-1) treatment. pH values in nutrient solution increased with increasing exposure time, but decreased with increasing Pi levels. Dissolved organic carbon (DOC) contents (dry weight) in nutrient solution decreased with increasing Pi levels, both for treatments with and without As (V). Arsenate at 1000 micromol L(-1) significantly (p < 0.05) increased DOC contents, especially for treatment without Pi. Six organic acids were detected in root exudates of Chinese brake fern, with oxalic and malic acids being most dominant.     

Screening of Indigenous Ornamental Species from Different Plant Families for Pb Accumulation Potential Exposed to Metal Gradient in Spiked Soils

Contamination of surface soils with lead (Pb) is a global concern due to the release of hazardous materials containing the metal element. In order to explore ways to remediate contaminated soils with less impact on environment and costs, this study aimed at screening ornamental plant species exposed to Pb gradient in spiked soils for Pb phytoextraction. Twenty-one ornamental plant species that currently grow in Pakistan, were selected to assess their potential for Pb accumulation. Pot experiments were conducted to evaluate the accumulative properties of the different plant species in unspiked control (Pb = 0) and spiked soils with different levels of Pb at 500, 1000, 1500 and 2000 mg Pb kg^?1 of soil. Biotranslocation factor (TF), Enrichment factor (EF) and Bioconcentration factor (CF) were calculated to assess the phytoremediation potential of tested plant species after seven weeks of exposure. Out of 21 plant species, Pelargonium hortorum and Mesembryanthemum criniflorum performed better and accumulated more than 1000 mg Pb kg^?1 of shoot dry biomass when they were grown in 500, 1000 and 1500 mg Pb kg^?1 contaminated soils. Both plants had no significant (P < 0.05) variation in the total dry biomass with increasing soil Pb concentration indicating a high tolerance to Pb. Considering the capacity of Pb accumulation, total dry biomass, TF, EF &; CF indices, Pelargonium hortorum and Mesembryanthemum criniflorum could be considered as Pb hyperaccumulators and could have the potential to be used in phytoremediation.     

Phytoremediation potential of Pityrogramma calomelanos var. austroamericana and Pteris vittata L. grown at a highly variable arsenic contaminated site

This study examined the phytoextraction potential of two arsenic (As) hyperaccumulators, Pteris vittata L. and Pityrogramma calomelanos var. austroamericana at a historical As-contaminated cattle dip site in northern New South Wales (NSW), Australia. Total As concentration in the surface soil (0-20 cm) showed a better spatial structure than phosphate-extractable As in the surface and sub-surface soil at this site. P. calomelanos var. austroamericana produced greater frond dry biomass (mean = 130 g plant(-1)) than P. vittata (mean = 81 g plant(-1)) after 10 months of growth. Arsenic concentration and uptake in fronds were also significantly higher in P. calomelanos var. austroamericana (means = 887 mg kg(-1) and 124 mg plant(-1)) than in P. vittata (means = 674 mg kg(-1) and 57 mg plant(-1)). Our results showed that under the field conditions and highly variable soil As at the site, P. calomelanos var. austroamericana performed better than P. vittata. We predict that P. calomelanos var. austroamericana would take approximately 100 years to reduce the total As to below 20 mg kg(-1) at the site compared to > or =200 years estimated for P. vittata. However, long-term data are required to confirm these observations under field conditions.     

EFFECTS OF NITROGEN AND PHOSPHORUS LEVELS,AND FROND-HARVESTING ON ABSORPTION,TRANSLOCATION AND ACCUMULATION OF ARSENIC BY CHINESE BRAKE FERN (PTERIS VITTATA L.)

This hydroponic experiment was conducted to determine the effects of nitrogen (N) and phosphorus (P) levels and frond-harvesting on the effectiveness of arsenic (As)-hyperaccumulator Chinese brake fern (Pteris vittata L.) to remove As from contaminated groundwater collected from south Florida. Three-month old ferns were grown in 38-L plastic tanks (two ferns per tank) containing 30-L of As-contaminated water (130 μg·L^?1 As), which was amended with modified 0.25 strength Hoagland's solution #2. Two N (26 or 52 mg·L^?1) and two P levels (1.2 and 2.4 mg·L^?1) were tested in one experiment, whereas the effect of frond-harvesting was tested in a separate experiment. Initially, N had little effect on plant As removal whereas low P treatment was more effective than high P and As was reduced to <5 μg·L^?1 in 28 d compared to 35 d. For well-established ferns, N and P levels had little effect. Reused fern, with or without harvesting the As-rich fronds, took up arsenic more rapidly so the As concentration in the groundwater declined faster (130 to ～10 μg·L^?1 in 8 h). Regardless of the treatments, most As (85–93%) was located in the aboveground tissue (rhizomes and fronds). Frond As concentrations were higher for non-harvested ferns than for ferns where fronds were partially harvested prior to treatment. Conversely, rhizomes accumulated more arsenic in ferns where fronds had been partially harvested. Low-P treatment coupled with reuse of more established ferns with or without harvesting fronds can be used to effectively remove arsenic from contaminated water using P. vittata     

Effects of Se on the uptake of essential elements in Pteris vittata L.

Selenium has been proven to be an antioxidant in plants at low dosages. To understand better the mechanisms of Se toxicity and benefit to plants, more investigations about effects of Se on the uptake of essential elements in plants would be desirable. In this study, hydroponic (nutrient solution culture) and pot (soil culture) experiments were simultaneously conducted to investigate the effects of Se on the uptake and distribution of essential elements in Pteris vittata. L (Chinese brake fern), an arsenic (As)-hyperaccumulator and a selenium (Se)-accumulator. Chinese brake fern took up much more Se in nutrient solution culture than in soil culture, with the highest Se content recorded as 1,573 mg kg^?1 in the roots, demonstrating remarkable tolerance to Se. In soil culture, Chinese brake fern also accumulated high content of Se, with the highest content measured as 81 mg kg^?1 and 233 mg kg^?1, in the fronds and roots, respectively. In soil culture, the addition of Se suppressed the uptake of most measured elements, including magnesium (Mg), potassium (K), phosphorus (P), iron (Fe), copper (Cu) and zinc (Zn). In nutrient solution culture, when the Se content in the tissues of Chinese brake fern was relatively low, the supplementation of Se suppressed the uptake of most essential elements; however, with the increase of Se content, stimulation effects of Se on the uptake of Ca, Mg, K were observed. An initial decrease followed by a rapid increase of Fe content in the fronds of Chinese brake fern was found with Se addition and tissue Se content increasing in nutrient solution culture, suggesting antagonistic and synergic roles of Se on these elements under low and high Se exposure, respectively. We suggest that Ca, Mg, K may be involved in the tolerance mechanism of Se, and that the regulation of Fe accumulation by Se in the fronds might be partially due to the dual effects of Se on Chinese brake fern.     

Antimony accumulation and antioxidative responses in four fern plants

Antimony (Sb) toxicity and contamination has become a growing concern in recent years. Remediation of Sb contamination using plants may be an effective approach. This study aimed to investigate the potential of antimony (Sb) tolerance and accumulation by plants, as well as to understand the antioxidative responses to Sb. One set of hydroponic trials was set up using four species of fern plants, including Pteris cretica (PCA), Microlepia hancei (MH), Cyrtomium fortunei (CYF) and Cyclosorus dentatus (CYD). Ferns were grown for 2 weeks in nutrient solution containing a medium (5 mg L^?1) and a high (20 mg L^?1) rate of Sb, with no Sb added as the control. The biomass of fern PCA remained constant with Sb addition, whereas the biomass of ferns CYF, MH and CYD at the high Sb rate exposure decreased by 12.5%, 35.0% and 38.3%, respectively as compared with their controls. This suggests a high to low Sb tolerance order for these four fern plants. For all of these fern plants, more Sb was accumulated in the roots than in the fronds. Antimony concentration in the roots at the high rate of Sb addition was recorded, on average, as 358 mg kg^?1 for fern PCA, 224 mg kg^?1 for fern CYF, 124 mg kg^?1 for fern CYD and 123 mg kg^?1 for fern MH. A high rate of addition of Sb increased the contents of malondialdehyde (MDA) by 41.3% and 171.6% for ferns MH and CYD, respectively, as compared with their controls. No changes for MDA contents were observed in ferns PCA and CYF with Sb addition, indicating no lipid peroxidation reaction in these two plants. At a medium rate of Sb addition, the activities of peroxidase, catalase and ascorbate peroxidase in fern PCA were much higher than those in ferns CYF, CYD and MH, demonstrating the important role of these three enzymes in resisting Sb toxicity. The consistency in unchanged biomass, high accumulation of Sb in roots, lower MDA contents, as well as high enzyme production in fronds, indicated that fern PCA was more tolerant to Sb than the other three fern plants. Antioxidative enzymes (peroxidase, catalase and ascorbate peroxidase) might be involved in Sb toxicity resistance of fern PCA.     

Cd AND Zn TOLERANCE AND ACCUMULATION BY SEDUM JINIANUM IN EAST CHINA

Field survey, hydroponic culture, and pot experiments were carried out to examine and characterize cadmium (Cd) and zinc (Zn) uptake and accumulation by Sedum jinianum, a plant species native to China. Shoot Cd and Zn concentrations in S. jinianum growing on a lead/Zn mine area reached 103–478 and 4165–8349 mg kg^?1 (DM), respectively. The shoot Cd concentration increased with the increasing Cd supply, peaking at 5083 mg kg^?1 (DM) when grown in nutrient at a concentration of 100 μmol L^?1 for 32 d, and decreased as the solution concentration increased from 200 to 400 μmol L^?1. The shoot-to-root ratio of plant Cd concentrations was > 1 when grown in solution Cd concentrations ≤ 200 μmol L^?1. Foliar, stem, and root Zn concentrations increased linearly with the increasing Zn level from 1 to 9600 μmol L^?1. The Zn concentrations in various plant parts decreased in the order roots > stem > leaves, with maximum concentrations of 19.3, 33.8, and 46.1 g kg^?1 (DM), respectively, when plants were grown at 9600 μmol Zn L^?1 for 32 d. Shoot Cd concentrations reached 16.4 and 79.8 mg kg^?1 (DM) when plants were grown in the pots of soil with Cd levels of 2.4 mg kg^?1 and 9.2 mg kg^?1, respectively. At soil Zn levels of 619 and 4082 mg kg^?1, shoot Zn concentrations reached 1560 and 15,558 mg kg^?1 (DM), respectively. The results indicate that S. jinianum is a Cd hyperaccumulator with a high capacity to accumulate Zn in the shoots.     

Antioxidant responses of hyper-accumulator and sensitive fern species to arsenic

Plant species capable of hyper-accumulating heavy metals are of considerable interest for phytoremediation, and differ in their ability to accumulate metals from the environment. This work aims to examine (i) arsenic accumulation in three fern species [Chinese brake fern (Pteris vittata L.), slender brake fern (Pteris ensiformis Burm. f.), and Boston fern (Nephrolepis exaltata L.)], which were exposed to 0, 150, or 300 muM of arsenic (Na(2)HAsO(4).7H(2)O), and (ii) the role of anti-oxidative metabolism in arsenic tolerance in these fern species. Arsenic accumulation increased with an increase in arsenic concentration in the growth medium, the most being found in P. vittata fronds showing no toxicity symptoms. In addition, accumulation was highest in the fronds, followed by the rhizome, and finally the roots, in all three fern species. Thiobarbituric acid-reacting substances, indicators of stress in plants, were found to be lowest in P. vittata, which corresponds with its observed tolerance to arsenic. All three ferns responded differentially to arsenic exposure in terms of anti-oxidative defence. Higher levels of superoxide dismutase, catalase, and ascorbate peroxidase were observed in P. vittata than in P. ensiformis and N. exaltata, showing their active involvement in the arsenic detoxification mechanism. However, no significant increase was observed in either guaiacol peroxides or glutathione reductase in arsenic-treated P. vittata. Higher activity of anti-oxidative enzymes and lower thiobarbituric acid-reacting substances in arsenic-treated P. vittata correspond with its arsenic hyper-accumulation and no symptoms of toxicity.     

Phytoremediative potential of salt-tolerant grass species for cadmium and lead under contaminated nutrient solution

Abstract

Phytoremediation of heavy metal contaminated soils represents a promising technique and salt-tolerant hyperaccumulators for multiple metals are the need of time. Therefore, phytoremediation potential of four salt-tolerant grass species [Dhab (Desmostachya bipinnata), Kallar (Leptochloa fusca), Para (Brachiaria mutica) and Sporobolus (Sporobolus arabicus Boiss)] was evaluated for cadmium (Cd) and lead (Pb) in a hydroponic study. The plants were harvested after a growth period of 3 months in a nutrient solution containing different levels of Cd (0, 5, and 25?mg?L^?1) and Pb (0, 25, and 125?mg L^?1). Results indicated that Dhab grass showed the highest root and shoot dry matter yield followed by Para, Kallar and Sporobolus grass irrespective of metal or its level under which they were grown. All the grass species showed considerable Cd-accumulating potential with an accumulation of >150?mg kg^?1of shoot dry matter at a higher level of Cd-contamination (25?mg?L^?1). While in case of shoot Pb-accumulation only Para grass performed well and accumulated Pb >1000?mg kg^?1 of shoot dry matter at the higher level of Pb-contamination (125?mg?L^?1). Moreover, Para and Dhab grasses performed better for shoot Cd-uptake, while only Para grass showed promising shoot Pb uptake potential. In conclusion, these grass species could be penitentially used for phytoremediation of salt-affected Cd and Pb contaminated soils.     

Using elevated carbon dioxide to enhance copper accumulation in Pteridium revolutum, a copper-tolerant plant, under experimental conditions

In our survey in the copper (Cu) mining area of China, a sun fern (Pteridium revolutum) was found to accumulate 30-567 mg Cu kg(-1) DW (33 samples) in its fronds with a large frond biomass. Cu translocation factors in the plants varied from 0.09 to 3.88. In a greenhouse pot experiment, the effect of an elevated CO2 concentration (700 microL L(-1)) on Cu accumulation in plants was studied using three fern species (P. revolutum, Pteridium aquilinum, and Pteris vittata) grown in the Cu-contaminated soil. P. revolutum showed a higher Cu tolerance but its Cu translocation factor was lower than 1. At the elevated CO2 concentration, frond biomass of all species was significantly increased, as was the total Cu content in the fronds of P. revolutum and P. aquilinum. Our study suggests that P. revolutum could serve as a good candidate for phytoextraction of Cu-contaminated soils and that doubling the ambient CO2 concentration will facilitate its use in phytoextraction.     

The effect of iron plaque on lead translocation in soil-Carex cinerascens kukenth. system

A pot experiment was conducted to investigate the effect of iron plaque on Pb uptake by and translocation in Carex cinerascens Kukenth. grown under open-air conditions. Using Scanning Electron Microscopy and Energy Dispersive X-Ray Spectrometry, iron plaque was present as an amorphous coating on root surfaces with uneven distribution. The amount of iron plaque increased significantly with increasing Fe additions regardless of Pb additions. The presence of iron plaque on the root surface of Carex cinerascens Kukenth. increased the concentrations of Pb adsorbed by iron plaque. The Pb percentage in whole roots increased by 14.52% at 500 mg kg^?1 Fe treatment than at 0 mg kg^?1 Fe, and the distribution coefficient (DC) of Pb and translocation factor (TF) root increased with Fe additions, but translocation factor (TF) shoot decreased with Fe additions. The results suggested that iron plaque could promote the translocation of Pb from soil to roots to some extent, and it played a role to reduce heavy metals pollution of Poyang Lake wetland.     

EDTA-assisted phytoextraction of lead and cadmium by Pelargonium cultivars grown on spiked soil

The aim of this study was to assess EDTA-assisted Pb and Cd phytoextraction potential of locally grown Pelargonium hortorum and Pelargonium zonale. Plants were exposed to different levels of Pb (0–1500?mg kg^?1) and Cd (0–150?mg kg^?1) in the absence or presence of EDTA (0–5?mmol kg^?1). P. hortorum and P. zonale accumulated 50.9% and 42.2% higher amount of Pb in shoots at 1500?mg kg^?1 Pb upon addition of 5?mmol kg^?1 EDTA. Plant dry biomass decreased 46.8% and 64.3% for P. hortorum and P. zonale, respectively at the combination of 1500?mg kg^?1 Pb and 5?mmol kg^?1 EDTA. In Cd and EDTA-treated groups, P. hortorum and P. zonale accumulated 2.7 and 1.6-folds more Cd in shoots at 4 and 2?mmol kg^?1 EDTA, respectively, in 150?mg Cd kg^?1 treatment. Plant dry biomass of P. hortorum and P. zonale was reduced by 46.3% and 71.3%, respectively, in soil having 150?mg Cd kg^?1 combined with 5?mmol kg^?1 EDTA. Translocation factor and enrichment factor of both plant cultivars at all treatment levels were >1. Overall, the performance of P. hortorum was better than that of P. zonale for EDTA-assisted phytoextraction of Pb and Cd.     

Evaluation of lead and chromium tolerance and accumulation level in Gomphrena celosoides: a novel metal accumulator from lead acid battery waste contaminated site in Nigeria

Abstract

Biology, tolerance, and metal (Pb and Cr) accumulating ability of Gomphrena celosoides were studied under hydroponic conditions. The seedlings were raised in Hoagland’s solution containing different concentrations of Pb (0, 500, 1000, 1500, 2000, 3000, 4000, and 5000?mg l^?1) and Cr (0, 50, 100, 150, 200, 300, and 400?mg l^?1). Biomass and metal accumulation in different plant parts were determined at seven (7) and fourteen (14) days after stress. Antioxidant enzyme activities, protein, and proline contents were estimated in stressed and unstressed plants. Gomphrena celosoides was able to tolerate Pb and Cr concentrations up to 4000 and 100?mg l^?1, respectively in hydroponic solution. Metal accumulation was concentration and duration dependent with the highest Pb (21,127.90 and 117,985.29?mg kg^?1) and Cr (3130.85 and 2428.90?mg kg^?1) in shoot and root, respectively found in the plants exposed to 5000?mg l^?1 Pb and 400?mg l^?1 Cr for 14?days. Proline, antioxidant enzyme activities, and protein contents were the highest in plant exposed to higher Pb and Cr concentrations for 7 and 14?days. Gomphrena celosoides could be considered as Pb and Cr accumulator with proline and increase in antioxidant enzyme activities being the tolerance mechanisms.     

Effects of arsenic species and concentrations on arsenic accumulation by different fern species in a hydroponic system

Two hydroponic experiments were conducted to evaluate factors affecting plant arsenic (As) hyperaccumulation. In the first experiment; two As hyperaccumulators (Pteris vittata and P. cretica mayii) were exposed to 1 and 10 mg L(-1) arsenite (AsIII) and monomethyl arsenic acid (MMA) for 4 wk. Total As concentrations in plants (fronds and roots) and solution were determined In the second experiment P. vittata and Nephrolepis exaltata (a non-As hyperaccumulator) were exposed to 5 mgL(-1) arsenate (AsV) and 20 mgL(-1) AsIIIfor 1 and 15 d. Total As and AsIII concentrations in plants were determined Compared to P. cretica mayii, P. vittata was more efficient in arsenic accumulation (1075-1666 vs. 249-627mg kg(-1) As in the fronds) partially because it is more efficient in As translocation. As translocation factor (As concentration ratio in fronds to roots) was 3.0-5.6 for P. vittata compared to 0.1 to 4.8 for P. cretica. Compared to N. exaltata, P. vittata was significantly more efficient in arsenic accumulation (38-542 vs. 4.8-71 mg kg(-1) As in thefronds) as well asAs translocation (1.3-5.6 vs. 0.2-0.5). In addition, P. vittata was much more efficient in As reduction from AsV to AsIII (83-84 vs. 13-24% AsIII in the fronds). Little As reduction occurred after 1-d exposure to AsV in both species indicates that As reduction was not instantaneous even in an As hyperaccumulator. Our data were consistent with the hypothesis that both As translocation and As reduction are important for plant As hyperaccumulation.     

Phytoremediation Potential of Plants Growing on the Pb-Contaminated Soil at the Song Tho Pb Mine,Thailand

The contamination of lead (Pb) is one of the main environmental problems on a global scale. This study assessed the potential of native metallophytes growing on the Song Tho Pb mine in Kanchanaburi province, Thailand, by a field survey. Plants and the associated soil samples were collected. Total Pb concentrations were analyzed by a flame atomic absorption spectrophotometer after a microwave-assisted acid digestion. While total Pb concentrations of top soils varied from 4881 to 16,720 mg/kg, those in soil around the roots ranged from 421 to 48,883 mg/kg. A total of 12 species belonging to eight families accumulated Pb concentrations in roots (47–32,633 mg/kg) which were higher than those in shoots (non-detected values – 1489 mg/kg). Bidens pilosa, with Pb accumulation in shoots > 1000 mg/kg and translocation factor (TF) > 1, could be useful in phytoextraction as a hyperaccumulator. Thysanolaena latifolia and Mimosa pudica with bioconcentration factor > 1 and TF < 1 could be useful in phytostabilization as excluders. So far, not many Pb hyperaccumulators are reported. The results from this study proposed a new candidate, B. pilosa, for Pb extraction. The potential use of these three phytoremediators should be further investigated using hydroponic and pot experiments.     

EFFECT OF INDOLE-3-ACETIC ACID,KINETIN, AND ETHYLENEDIAMINETETRAACETIC ACID ON PLANT GROWTH AND UPTAKE AND TRANSLOCATION OF LEAD,MICRONUTRIENTS, AND MACRONUTRIENTS IN ALFALFA PLANTS

Alfalfa plants germinated and grown for 15 d in soil containing 80 mg Pb kg^?1 were treated with ethylenediaminetetraacetic acid (EDTA) at 0.8 mM and indole-3-acetic acid-kinetin (IAA-KN) at 100 μM. Fifteen days after the treatment application, the concentration of lead (Pb), macronutrients, and micronutrients was determined using inductively coupled plasma/optical emission spectroscopy. The chlorophyll content and plant growth were also measured. Roots of plants exposed to Pb alone, Pb–EDTA, and Pb–EDTA-IAA-KN had 160, 140, and 150 mg Pb kg^?1 DW, respectively. Pb was not detected in the stems of plants exposed to Pb alone; however, stems of plants treated with EDTA and EDTA–IAA-KN had 78 and 142 mg Pb kg^?1 DW, respectively. While the Pb concentration in leaves of plants treated with EDTA and EDTA–IAA-KN was 92 and 127 mg kg^?1 DW, respectively. In addition, EDTA and EDTA–IAA-KN significantly increased the translocation of zinc and manganese to leaves. The x-ray absorption spectroscopic studies demonstrated that Pb(II) was transported from roots to leaves without a change in the oxidation state.     

Soil Nitrogen Fertilization Effects on Phytoextraction of Cadmium and Lead by Tobacco (Nicotiana tabacum L.)

A greenhouse experiment using 24 plastic pots filled with 6 kg of Pb- and Cd-contaminated soil was carried out. In all 24 pots, soils were heavy metal–contaminated with 10 mg Cd kg^?1 soil and 500 mg of Pb kg^?1 soil by using CdCl and PbNO₃. Two-month-old tobacco (Nicotiana tabacum L.) plants were used to extract these heavy metals. Results showed that tobacco is able to remove Cd and Pb from contaminated soils and concentrate them in its harvestable part, that is, it could be very useful in phytoextraction of these heavy metals. Increasing additions of ammonium nitrate to soil (50, 100, and 150 mg N kg^?1 soil) significantly (p ≤ .05) increased aboveground Cd and Pb accumulation during a 50-day experimental period, whereas increasing additions of urea to soil (50 and 100 mg N kg^?1 soil) did not show these effects at the same significance levels. Increasing additions of ammonium nitrate to soil shows as dry matter increases, both accumulated Cd and accumulated Pb also increase when tobacco plants are growing under Pb- and Cd-contaminated soil conditions. Higher Pb concentrations depress Cd/Pb ratios for concentrations and accumulations, suggesting that Pb negatively affects Cd concentration and/or accumulation.     

Mycorrhizal Limonium Sinuatum (l.) Mill. Enhances Accumulation of Lead and Cadmium

Heavy metals accumulation in soils poses a potential threat to ecosystems, which, in turn, threat human health through food chains. Therefore, remediating polluted sites is important to environment and humanity. In this investigation, statice (L. sinuatum) was exposed to Cd (0, 15, 30, 60 mg kg^?1 soil) or Pb (0, 100, 150, 300 mg kg^?1 soil) in a pot experiment to assess its tolerance to each metal and study its phytoaccumulation capability. The benefits of mycorrhization (mixture of Glomus mosseae and G. intraradices) were also studied simultaneously. Single exposure to Cd or Pb reduced the plant growth, but statice was still relatively tolerant to both metals. The plants accumulated both metals in their roots; little was translocated to the shoots. Total Pb and total Cd accumulated by the roots was approximately 2 and 3 times higher in mycorrhizal than non-mycorrhizal plants (49 versus 147 and 595 versus 956 μg plant^?1) respectively; however, mycorrhization alleviated metal phytotoxicity. The results suggest that statice is a potential candidate to be used as an ornamental plant in lead and cadmium polluted sites, mainly inoculated with arbuscular mycorrhizae. Besides that, it would be useful as a Pb or Cd controlling agent by means of phytostabilization.