Hyperaccumulator Pteris Vittata Research Articles

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.

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure.

Interactive effects of pH, arsenic and phosphorus on uptake of As and P and growth of the arsenic hyperaccumulator Pteris vittata L. under hydroponic conditions

Arsenic (As)-contaminated soil and water vary with pH and concentrations of As and P. This study examined the effects and interactions of three factors, pH, As and P, on As hyperaccumulator Pteris vittata L. to optimize plant growth and maximize As removal from contaminated sites, especially water. Two sets of hydroponic experiments were conducted using three-factor, five-level central composite design. Five levels of pH (4.5–8.0), As (0–668 μM), and P (0–1000 μM) were used to understand their individual as well as interactive effects. Plant biomass and uptake of P and As were impacted by all the three factors. Phosphorus inhibited As uptake at all concentrations, whereas As below 334 μM benefited plant growth and P uptake. Enhanced plant biomass was most likely a result of increased P uptake. Low pH enhanced plant uptake of As (pH≤5.21) and P (pH≤6.25). The fern had a relatively high biomass and P uptake at low pH/low As or high pH/high As. The referencing saddle points (turning points) were pH 6.33 and As 359 μM for plant biomass and pH 5.87 and As 331 μM for P uptake based on the response surface plot. The results suggested that optimum plant growth could be achieved by adjusting pH corresponding to As levels in the growth media, and maximum plant As hyperaccumulation by maintaining minimum P concentrations with medium pH≤5.21. Our results should be useful for developing strategies to remediate As-contaminated water using Chinese Brake fern.

Arsenic hyperaccumulator Pteris Vittata L. and its arsenic ac-cumulation

An arsenic hyperaccumulator Pteris vittata L. (Chinese brake) was first discovered in China by means of field survey and greenhouse cultivation. Field survey showed that Chinese brake had large accumulating capacity to arsenic; the orders of arsenic content in different parts of the fern were as follows: leaves>leafstalks>roots, which is totally different from that of ordinary plants; bioaccumulation coefficients of the above ground parts of the fern decreased as a power function of soil arsenic contents. In the control of pot trials with normal unpolluted soil containing 9 mg/kg of arsenic, the bioaccumulation coefficients of the above ground parts and rhizoids of Chinese brake were as high as 71 and 80 respectively. Greenhouse cultivation in the contaminated soil from mining areas has shown that more than 1 times greater arsenic can be accumulated in the leaves of the fern than that of field samples with the largest content of 5070 mg/kg As on a dry matter basis. During greenhouse cultivation, arsenic content in the leaves of the fern increased linearly with time prolonging. Not only has Chinese brake extraordinary tolerance and accumulation to arsenic, but it grew rapidly with great biomass, wide distribution and easy adaptation to different environmental conditions as well. Therefore, it has great potential in future remediation of arsenic contamination. It also demonstrates important value for studies of arsenic physiology and biochemistry such as arsenic absorption, translocation and detoxification mechanisms in plants.