Arsenic Hyperaccumulator Pteris Vittata Research Articles

First evidence on different transportation modes of arsenic and phosphorus in arsenic hyperaccumulator Pteris vittata

Arsenic (As) reduction and translocation are key processes for As hyperaccumulation by the hyperaccumulator Pteris vittata L. Micro-X-ray adsorption spectroscopy of P. vittata’s rhizoid tissues revealed that As reduction mainly occurred in endodermis during translocation from epidermis to vascular bundle. Prior to reduction, arsenate (As (V)) translocation was an active process requiring energy and employing a phosphate (P) transporter. Use of a synchrotron X-ray microprobe showed that As (V) and P were cotransported and that this process could be enhanced by As (V) exposure or P deficiency but restrained by energy release inhibition caused by 2,4-dinitrophenol or sodium orthovanadate. In contrast, after As reduction, As(III) translocation differed from P translocation and was more efficient, appearing free from the apparent endodermal blockage. The results here revealed the role of the P transporter on As translocation as well as the key role of As reduction in As hyperaccumulation by P. vittata.

Uptake and translocation of arsenite by Pteris vittata L.: Effects of glycerol, antimonite and silver

AsIII uptake in living cells is through aquaglyceroporin transporters, but it is unknown in arsenic-hyperaccumulator Pteris vittata. We investigated the effects of AsIII analogs glycerol and antimonite (SbIII) at 0–100 mM and aquaporin inhibitor AgNO 3 at 0–0.1 mM on the uptake of 0.1 mM AsIII or AsV by P. vittata over 1–2 h. Glycerol or SbIII didn’t impact AsIII or AsV uptake by P. vittata ( p < 0.05), with As concentrations in the fronds and roots being 4.4–6.3 and 3.9–6.2 mg/kg. However, 0.01 mM AgNO 3 reduced As concentrations in the fronds and roots by 64% and 58%. Hence, AsIII uptake in P. vittata might be via an aquaporin transporter different from glycerol and SbIII transporters. Further as AsIII analogs and aquaporin inhibitor had no impact on AsV uptake, AsIII and AsV were likely taken up by different transporters in P. vittata. Our results imply a different AsIII transporter in P. vittata from other plants.

Arsenic-resistant bacteria solubilized arsenic in the growth media and increased growth of arsenic hyperaccumulator Pteris vittata L.

The role of arsenic-resistant bacteria (ARB) in arsenic solubilization from growth media and growth enhancement of arsenic-hyperaccumulator Pteris vittata L. was examined. Seven ARB (tolerant to 10mM arsenate) were isolated from the P. vittata rhizosphere and identified by 16S rRNA sequencing as Pseudomonas sp., Comamonas sp. and Stenotrophomonas sp. During 7-d hydroponic experiments, these bacteria effectively solubilized arsenic from the growth media spiked with insoluble FeAsO4 and AlAsO4 minerals (from <5μgL−1 to 5.04–7.37mgL−1 As) and enhanced plant arsenic uptake (from 18.1–21.9 to 35.3–236mgkg−1 As in the fronds). Production of (1) pyochelin-type siderophores by ARB (fluorescent under ultraviolet illumination and characterized with thin layer chromatography) and (2) root exudate (dissolved organic C) by P. vittata may be responsible for As solubilization. Increase in P. vittata root biomass from 1.5–2.2 to 3.4–4.2g/plant dw by ARB and by arsenic was associated with arsenic-induced plant P uptake. Arsenic resistant bacteria may have potential to enhance phytoremediation of arsenic-contaminated soils by P. vittata.

Arsenate reductase activity in roots from the arsenic hyperaccumulator Pteris vittata utilizes both glutathione and dithiothreitol as reductants

The role of glutathione and dithiothreitol as reductants supporting arsenate reductase activity in root extract from the arsenic hyperaccumulator Pteris vittata was examined. The two reductants in combination enhanced arsenate reduction in vitro more than glutathione alone. The implications of these results for in vivo arsenate reduction are discussed.

Characterization of phytase from three ferns with differing arsenic tolerance

Phytase is involved in many physiological activities in plants including phosphorus metabolism and stress response. The effects of arsenic on phytase activities in arsenic-hyperaccumulator Pteris vittata were determined. Two arsenic-sensitive ferns (Pteris ensiformis and Nephrolepis exaltata) were included for comparison purpose. Fern phytase was extracted with Tris-HCl buffer (pH 7.6) followed by ammonium sulfate partial purification to characterize its properties and arsenic stress responses. The phytase showed an optimum pH of 5.0 and temperature of 40°C except for P. vittata with 40-70°C. Phytase from P. vittata was the first plant-phytase showing high heat resistance with no loss of activity by heating it at 70°C, which may have application in feed industry. Phytase activity was inhibited by arsenate but not by arsenite. The fact that P. vittata phytase was the most heat-tolerant (40-70°C) and had the highest resistance to arsenate among the three ferns suggest that phytase may play a role in arsenic detoxification and arsenic hyperaccumulation in P. vittata.

Sulfate and glutathione enhanced arsenic accumulation by arsenic hyperaccumulator Pteris vittata L.

This experiment examined the effects of sulfate (S) and reduced glutathione (GSH) on arsenic uptake by arsenic hyperaccumulator Pteris vittata after exposing to arsenate (0, 15 or 30 mg As L −1) with sulfate (6.4, 12.8 or 25.6 mg S L −1) or GSH (0, 0.4 or 0.8 mM) for 2-wk. Total arsenic, S and GSH concentrations in plant biomass and arsenic speciation in the growth media and plant biomass were determined. While both S (18–85%) and GSH (77–89%) significantly increased arsenic uptake in P. vittata, GSH also increased arsenic translocation by 61–85% at 0.4 mM ( p < 0.05). Sulfate and GSH did not impact plant biomass or arsenic speciation in the media and biomass. The S-induced arsenic accumulation by P. vittata was partially attributed to increased plant GSH (21–31%), an important non-enzymatic antioxidant countering oxidative stress. This experiment demonstrated that S and GSH can effectively enhance arsenic uptake and translocation by P. vittata.

Uptake and translocation of arsenite and arsenate by Pteris vittata L.: Effects of silicon, boron and mercury

To better understand arsenite (AsIII) uptake via aquaporin channels by arsenic hyperaccumulator Pteris vittata, the effects of silicic and boric acid (AsIII analogues) and HgCl 2 (aquaporin inhibitor) on plant arsenic uptake and translocation were investigated. P. vittata was grown in 0.2-strength Hoagland solution containing (1) 15 μM AsIII or arsenate (AsV) for 1 d with or without 0.5 mM silicic acid (Si experiment) or 0.3 mM boric acid (B experiment), or (2) 15 μM AsIII for 2 d with or without 10 μM HgCl 2 (Hg experiment). Silicic acid and boric acid had no effect on AsIII and AsV uptake by P. vittata, nor did HgCl 2. It is possible that AsIII was taken up by different aquaporins in P. vittata or those aquaporins in P. vittata had high capacity and they were insensitive to Hg. While AsV was stable in the growth media, substantial amount of AsIII was oxidized to AsV, i.e., 16–76%. In the presence of 210 μM P at pH 6, P. vittata was more efficient in taking up and translocating AsIII than AsV as demonstrated by greater arsenic concentrations in the fronds and roots (6.6 and 46 mg kg −1) in the AsIII treatment than those in the AsV treatment (2.3 and 8.2 mg kg −1). However, at 15 μM AsIII, its AsIII translocation rate from the roots to the fronds was slower than its AsIII uptake rate by the roots since the arsenic concentration in the fronds was only ∼14% of that in the roots. Our data also demonstrated that both AsIII oxidation and AsV reduction occurred in the roots of P. vittata. However, how and if AsIII uptake by P. vittata is via aquaporins still need further investigation.

Timing of phosphate application affects arsenic phytoextraction by Pteris vittata L. of different ages

The effects of timing in phosphate application on plant growth and arsenic removal by arsenic hyperaccumulator Pteris vittata L. of different ages were evaluated. The hydroponic experiment consisted of three plant ages (A 45d, A 90d and A 180d) and three P feeding regimens (P 200+0, P 134+66 and P 66+134) growing for 45 d in 0.2-strength Hoagland–Arnon solution containing 145 μg L −1 As. While all plants received 200 μM P, P was added in two phases: during acclimation and after arsenic exposure. High initial P-supply (P 200+0) favored frond biomass production and plant P uptake, while split-P application (P 134+66 and P 66+134) favored plant root production. Single P addition favored arsenic accumulation in the roots while split-P addition increased frond arsenic accumulation. Young ferns (A 45d) in treatment P 134+66 were the most efficient in arsenic removal, reducing arsenic concentration to below 10 μg L −1 in 35 d. The results indicated that the use of young ferns, coupled with feeding of low initial P or split-P application, increased the efficiency of arsenic removal by P. vittata.

Phytoextraction by arsenic hyperaccumulator Pteris vittata L. from six arsenic-contaminated soils: Repeated harvests and arsenic redistribution

This greenhouse experiment evaluated arsenic removal by Pteris vittata and its effects on arsenic redistribution in soils. P. vittata grew in six arsenic-contaminated soils and its fronds were harvested and analyzed for arsenic in October, 2003, April, 2004, and October, 2004. The soil arsenic was separated into five fractions via sequential extraction. The ferns grew well and took up arsenic from all soils. Fern biomass ranged from 24.8 to 33.5 g plant −1 after 4 months of growth but was reduced in the subsequent harvests. The frond arsenic concentrations ranged from 66 to 6,151 mg kg −1, 110 to 3,056 mg kg −1, and 162 to 2,139 mg kg −1 from the first, second and third harvest, respectively. P. vittata reduced soil arsenic by 6.4–13% after three harvests. Arsenic in the soils was primarily associated with amorphous hydrous oxides (40–59%), which contributed the most to arsenic taken up by P. vittata (45–72%). It is possible to use P. vittata to remediate arsenic-contaminated soils by repeatedly harvesting its fronds.

Plant regeneration of the arsenic hyperaccumulator Pteris vittata L. from spores and identification of its tolerance and accumulation of arsenic and copper

An in vitro plant regeneration system was established from the spores of Pteris vittata and identification of its tolerance, and accumulation of gametophytes and callous, to arsenic (As) and copper (Cu) was investigated. The highest frequency (100%) of callus formation was achieved from gametophyte explants treated with 0.5 mg l−1 6-benzylaminopurine (6-BA) + 0.5 mg l−1 gibberellin acid (GA). Furthermore, sporophytes were differentiated from the callus tissue derived from gametophyte explants on MS medium supplemented with 0.5 mg l−1 6-BA, 0.5–1.0 mg l−1 GA and additional 300 mg l−1 lactalbumin hydrolysate (LH) for 4 weeks. The optimum combination of ½ MS + 1.0 mg l−1 GA + 0.5 mg l−1 6-BA + 300 mg l−1 LH promoted sporophyte formation on 75 ± 10% of the callus. Every callus derived from gametophyte explants could achieve 3–4 sporophytes. The in vitro growth of gametophyte and callus was accelerated in the medium containing Na3AsO4 lower than 0.5 mM, but this growth was inhibited with 2 mM Na3AsO4. And with the increase of Na3AsO4 in the culture medium from 0 to 2 mM, the As accumulation in gametophytes and callus increased and achieved a level of 763.3 and 315.4 mg kg−1, respectively. Gametophytes and calluses transplanted to culture medium, supplemented with different concentrations of CuSO4, are similar to those in Na3AsO4, and the Cu accumulation in gametophytes could achieve 7,940 mg kg−1 when gametophytes were subcultured in medium containing 3 mM CuSO4. These results suggested that the high efficiency propagation system could be a useful and rapid means to identify other heavy metal tolerance and accumulation. Further, the regeneration ability of callus made it possible for genetic transformation of this fern.

Effects of nutrients on arsenic accumulation by arsenic hyperaccumulator Pteris vittata L.

This research investigated the effects of various nutrients on arsenic (As) removal by arsenic hyperaccumulator Pteris vittata L. in a Hoagland nutrient solution (HNS). The treatments included different concentrations of Ca and K in 20% strength of HNS, different strengths of HNS (10, 20 and 30%), different strengths of HNS (10 and 20%) with and without CaCO 3, and different concentrations of Ca, K, NO 3, NH 4, and P in 20% strength of HNS. The plants were grown in nutrient solution containing 1 mg As L −1 for 4 weeks except the Ca/K experiment where the plants were grown in nutrient solution containing 10 or 50 mg As L −1 for 1 week. Adding up to 4 mM Ca or 3 mM K to 20% strength HNS significantly ( P < 0.05) increased plant arsenic accumulation when the solution contained 10 mg As L −1. Plant arsenic removal was reduced with increasing Ca and K concentrations at 50 mg As L −1. Lower strength of HNS (10%) resulted in the greatest plant arsenic removal (79%) due to lower competition of P with As for plant uptake. Addition of CaCO 3 to 20% strength of HNS significantly increased arsenic removal by P. vittata. Among the nutrients tested, NO 3 and CaCO 3 were beneficial to plant arsenic removal while NH 4, P and Cl had adverse effects. This experiment demonstrated that it is possible to optimize plant arsenic removal by adjusting nutrients in the growth medium.

Effects of Plant Age on Arsenic Hyperaccumulation by Pteris vittata L.

Plant age affects its elemental uptake and biomass accumulation, which is important for the application of plants in phytoextraction. In this research, we evaluated the effects of plant age on arsenic accumulation by arsenic hyperaccumulator Pteris vittata after growing in an arsenic-contaminated soil for 8 weeks. The study used a completely randomized design consisting of four plant ages (2, 4, 10 and 16 months) with four replications each. While the fronds of the 2 month old plants contained 36% more arsenic than those of the 4 and 16 month old plants, they were lower in roots. After 8 weeks of growth, the final frond biomass increased by 39, 6.9, 2.0 and 1.1 times compared to the initial frond biomass, from youngest to oldest, respectively. Higher phosphorus and iron accumulation in the roots of older plants may have affected the plant’s efficiency to bioconcentrate and transfer arsenic from the roots to the fronds. Greater metabolic activity and higher rate of biomass production lead to higher As accumulation and removal by young plants. This research demonstrated that the use of young plants can be an effective strategy to reduce the time to remediate an As-contaminated site.

Effects of plant arsenic uptake and heavy metals on arsenic distribution in an arsenic-contaminated soil

This study examined the effects of heavy metals and plant arsenic uptake on soil arsenic distribution. Chemical fractionation of an arsenic-contaminated soil spiked with 50 or 200 mg kg −1 Ni, Zn, Cd or Pb was performed before and after growing the arsenic hyperaccumulator Pteris vittata L for 8 weeks using NH 4Cl (water-soluble plus exchangeable, WE-As), NH 4F (Al-As), NaOH (Fe-As), and H 2SO 4 (Ca-As). Arsenic in the soil was present primarily as the recalcitrant forms with Ca-As being the dominant fraction (45%). Arsenic taken up by P. vittata was from all fractions though Ca-As contributed the most (51–71% reduction). After 8 weeks of plant growth, the Al-As and Fe-As fractions were significantly ( p < 0.01) greater in the metal-spiked soils than the control, with changes in the WE-As fraction being significantly ( p = 0.007) correlated with plant arsenic removal. The plant's ability to solubilize soil arsenic from recalcitrant fractions may have enhanced its ability to hyperaccumulate arsenic.

Arsenic resistance in Pteris vittata L.: identification of a cytosolic triosephosphate isomerase based on cDNA expression cloning in Escherichia coli

Arsenic hyperaccumulator Pteris vittata L. (Chinese brake fern) grows well in arsenic-contaminated media, with an extraordinary ability to tolerate high levels of arsenic. An expression cloning strategy was employed to identify cDNAs for the genes involved in arsenic resistance in P. vittata. Excised plasmids from the cDNA library of P. vittata fronds were introduced into Escherichia coli XL-1 Blue and plated on medium containing 4 mM of arsenate, a common form of arsenic in the environment. The deduced amino acid sequence of an arsenate-resistant clone, PV4-8, had cDNA highly homologous to plant cytosolic triosephosphate isomerases (cTPI). Cell-free extracts of PV4-8 had 3-fold higher level of triosephosphate isomerase (TPI) specific activities than that found in E. coli XL-1 Blue and had a 42 kD fusion protein immunoreactive to polyclonal antibodies raised against recombinant Solanum chacoense cTPI. The PV4-8 cDNA complemented a TPI-deficient E. coli mutant. PV4-8 expression improved arsenate resistance in E. coli WC3110, a strain deficient in arsenate reductase but not in AW3110 deficient for the whole ars operon. This is consistent with the hypothesis that PV4-8 TPI increased arsenate resistance in E. coli by directly or indirectly functioning as an arsenate reductase. When E. coli tpi gene was expressed in the same vector, bacterial arsenate resistance was not altered, indicating that arsenate tolerance was specific to P. vittata TPI. Paradoxically, P. vittata TPI activity was not more resistant to inhibition by arsenate in vitro than its bacterial counterpart suggesting that arsenate resistance of conventional TPI reaction was not the basis for the cellular arsenate resistance. P. vittata TPI activity was inhibited by incubation with reduced glutathione while bacterial TPI was unaffected. Consistent with cTPI's role in arsenate reduction, bacterial cells expressing fern TPI had significantly greater per cent of cellular arsenic as arsenite compared to cells expressing E. coli TPI. Excised frond tissue infiltrated with arsenate reduced arsenate significantly more under light than dark. This research highlights a novel role for P. vittata cTPI in arsenate reduction.

Arsenic chemistry in the rhizosphere of Pteris vittata L. and Nephrolepis exaltata L.

This greenhouse experiment evaluated the influence of arsenic uptake by arsenic hyperaccumulator Pteris vittata L. and non-arsenic hyperaccumulator Nephrolepis exaltata L. on arsenic chemistry in bulk and rhizosphere soil. The plants were grown for 8 weeks in a rhizopot with a soil containing 105 mg kg −1 arsenic. The soil arsenic was fractionated into five fractions with decreasing availability: non-specifically bound (N), specifically bound (S), amorphous hydrous-oxide bound (A), crystalline hydrous-oxide bound (C), and residual (R). P. vittata produced larger plant biomass (7.38 vs. 2.32 mg plant −1) and removed more arsenic (2.61 vs. 0.09 mg pot −1 arsenic) than N. exaltata. Plant growth reduced water-soluble arsenic, and increased soil pH ( P. vittata only) in the rhizosphere soil. P. vittata was more efficient than N. exaltata to access arsenic from all fractions (39–64% vs. 5–39% reduction). However, most of the arsenic taken up by both plants was from the A fraction (67–77%) in the rhizosphere soil, the most abundant (61.5%) instead of the most available (N fraction).

Arsenic speciation, and arsenic and phosphate distribution in arsenic hyperaccumulator Pteris vittata L. and non-hyperaccumulator Pteris ensiformis L.

This study examined the roles of arsenic translocation and reduction, and P distribution in arsenic detoxification of Pteris vittata L. (Chinese Brake fern), an arsenic hyperaccumulator and Pteris ensiformis L. (Slender Brake fern), a non-arsenic hyperaccumulator. After growing in 20% Hoagland solution containing 0, 133 or 267 μM of sodium arsenate for 1, 5 or 10 d, the plants were separated into fronds, rhizomes, and roots. They were analyzed for biomass, and concentrations of arsenate (AsV), arsenite (AsIII) and phosphorus. Arsenic in the fronds of P. vittata was up to 20 times greater than that of P. ensiformis, yet showing no toxicity symptoms as did in P. ensiformis. While arsenic was concentrated primarily in the fronds of P. vittata as arsenite it was mainly concentrated in the roots of P. ensiformis as arsenate. Arsenic reduction in the plants took longer than 1-d. P. vittata maintained greater P in the roots while P. ensiformis in the fronds. The high arsenic tolerance of the hyperaccumulator P. vittata may be attributed to its ability to effectively reduce arsenate to arsenite in the fronds, translocate arsenic from the roots to fronds, and maintain a greater ratio of P/As in the roots.

Using phosphate rock to immobilize metals in soil and increase arsenic uptake by hyperaccumulator Pteris vittata

This greenhouse experiment evaluated the effects of phosphate rock (PR) on arsenic and metal uptake by the arsenic hyperaccumulator Pteris vittata in a soil spiked with arsenic and heavy metals Cd, Pb and Zn. Five soil treatments were used, 1) control with no arsenic, 2) spiked with 50 mg kg − 1 As (As) as Na 2H AsO 4, 3) spiked with 50 mg kg − 1 As and P as PR (AsP), 4) spiked with 50 mg kg − 1 As, Pb, Cd, and Zn (AsM), and 5) spiked with 50 mg kg − 1 As, Pb, Cd, Zn and P (AsMP). The plants were harvested after growing in the soil for five weeks. Compared to the As treatment, the presence of heavy metals (AsM) reduced arsenic concentrations in the fronds from 1631 to 608 mg kg − 1 . However, this effect was mitigated by PR (AsMP), with arsenic concentrations in the fronds increased from 608 to 1046 mg kg − 1 . Phosphate rock also significantly reduced Pb (13.5 to 4.10 mg kg − 1 ) and Cd (13.0 to 3.45 mg kg − 1 ) concentrations in the fronds. Most of the arsenic in P. vittata was accumulated in the fronds (89–93%). Compared to the control, P was more concentrated in the roots along with less P being translocated to the fronds in the treatments with arsenic. While in those same treatments higher Ca concentrations in both the fronds and roots were observed. This research shows that PR was effective in increasing arsenic uptake and decreasing metal uptake by P. vittata and thus can be used as a cost-effective amendment for phytoremediation of arsenic and metal polluted soils.

Effects of arsenic on concentration and distribution of nutrients in the fronds of the arsenic hyperaccumulator Pteris vittata L

Pteris vittata was the first terrestrial plant known to hyperaccumulate arsenic (As). However, it is unclear how As hyperaccumulation influences nutrient uptake by this plant. P. vittata fern was grown in soil spiked with 0–500 mg As kg −1 in the greenhouse for 24 weeks. The concentrations of essential macro- (P, K, Ca, and Mg) and micro- (Fe, Mn, Cu, Zn, B and Mo) elements in the fronds of different age were examined. Both macro- and micronutrients in the fronds were found to be within the normal concentration ranges for non-hyperaccumulators. However, As hyperaccumulation did influence the elemental distribution among fronds of different age of P. vittata. Arsenic-induced P and K enhancements in the fronds contributed to the As-induced growth stimulation at low As levels. The frond P/As molar ratios of 1.0 can be used as the threshold value for normal growth of P. vittata. Potassium may function as a counter-cation for As in the fronds as shown by the As-induced K increases in the fronds. The present findings not only demonstrate that P. vittata has the ability to maintain adequate concentrations of essential nutrients while hyperaccumulating As from the soil, but also have implications for soil management (fertilization in particular) of P. vittata in As phytoextraction practice.

Effects of heavy metals on growth and arsenic accumulation in the arsenic hyperaccumulator Pteris vittata L.

The effects of Cd, Ni, Pb, and Zn on arsenic accumulation by the arsenic hyperaccumulator Pteris vittata were investigated in a greenhouse study. P. vittata was grown for 8 weeks in an arsenic-contaminated soil (131 mg As kg −1), which was spiked with 50 or 200 mg kg −1 Cd, Ni, Pb, or Zn (as nitrates). P. vittata was effective in taking up arsenic (up to 4100 mg kg −1) and transporting it to the fronds, but little of the metals. Arsenic bioconcentration factors ranged from 14 to 36 and transfer factors ranged from 16 to 56 in the presence of the metals, both of which were reduced with increasing metal concentration. Fern biomass increased as much as 12 times compared to the original dry weight after 8 weeks of growth (up to 19 g per plant). Greater concentrations of Cd, Ni, and Pb resulted in greater catalase activity in the plant. Most of the arsenic in the plant was present as arsenite, the reduced form, indicating little impact of the metals on plant arsenic reduction. This research demonstrates the capability of P. vittata in hyperaccumulating arsenic from soils in the presence of heavy metals.

Arsenic hyperaccumulation by Pteris vittata from arsenic contaminated soils and the effect of liming and phosphate fertilisation

Pot experiments were carried out to investigate the potential of phytoremediation with the arsenic hyperaccumulator Pteris vittata in a range of soils contaminated with As and other heavy metals, and the influence of phosphate and lime additions on As hyperaccumulation by P. vittata. The fern was grown in 5 soils collected from Cornwall (England) containing 67–4550 mg As kg −1 and different levels of metals. All soils showed a similar distribution pattern of As in different fractions in a sequential extraction, with more than 60% of the total As being associated with the fraction thought to represent amorphous and poorly-crystalline hydrous oxides of Fe and Al. The concentration of As in the fronds ranged from 84 to 3600 mg kg −1, with 0.9–3.1% of the total soil As being taken up by P. vittata. In one soil which contained 5500 mg Cu kg −1 and 1242 mg Zn kg −1, P. vittata suffered from phytotoxicity and accumulated little As (0.002% of total). In a separate experiment, neither phosphate addition (50 mg P kg −1 soil) nor liming (4.6 g CaCO 3 kg −1 soil) was found to affect the As concentration in the fronds of P. vittata, even though phosphate addition increased the As concentration in the soil pore water. Between 4 and 7% of the total soil As was taken up by P. vittata in 4 cuttings in this experiment. The results indicate that P. vittata can hyperaccumulate As from naturally contaminated soils, but may be suitable for phytoremediation only in the moderately contaminated soils.