An arsenic hyperaccumulating fern,Pteris vittata L. (Pteridaceae) broadly affects terrestrial invertebrate abundance

1. The Chinese brake fern (Pteris vittata L.; Pteridaceae) can accumulate up to 27 000 mg kg^?1 dry wt. of arsenic (As) from the soil into its above‐ground biomass. They may use this As to deter invertebrate threats. 2. This study explored how As concentrations [As] in the fern, and in soil associated with the fern, influenced the abundance and composition of various invertebrates. 3. Populations of P. vittata were identified in the field. Soils from the base of the fern and from 3 m away of each plant were collected and pitfall traps were installed. Soil and fern arsenic concentrations ([As]) were measured via inductively coupled plasma mass spectrometry and invertebrates were identified to order and classified by feeding guild. 4. Increased [As] did not affect all feeding guilds and orders equally. For example, individual herbivore abundance did not decrease as [As] increased, but predator abundance did. In many cases, the impact of soil [As] on invertebrates depended on the distance from the fern. Fern [As] also influenced components of the community, but only at 3 m away from the fern. Furthermore, the abundances of many invertebrate groups were higher beneath the fern, where [As] was higher. 5. These results suggest that hyperaccumulated As can impact the invertebrate community, but the defensive benefits of hyperaccumulation are more complex than have been previously described. The authors advocate that future studies examining the potential defensive benefits of hyperaccumulation should do so in a natural setting that incorporates this complexity and invertebrate richness.     

Phytoremediation of arsenic-contaminated groundwater by the arsenic hyperaccumulating fern Pteris vittata L

Arsenic concentrations in a much larger fraction of U.S. groundwater sources will exceed the maximum contaminant limit when the new 10 microg L(-1) EPA standard for drinking water takes effect in 2006. Thus, it is important to develop remediation technologies that can meet this new standard. Phytoremediation of arsenic-contaminated groundwater is a relatively new idea. In this research, an arsenic-hyperaccumulating fern, commonly known as Chinese Brake fern (Pteris vittata L.), was grown hydroponically to examine its effectiveness in arsenic removal from what is believed to be herbicide-contaminated groundwater. One plant grown in 600 mL of groundwater effectively reduced the arsenic concentration from 46 to less than 10 microg L(-1) in 3 days. Re-used plants continued to take up arsenic from the groundwater, albeit at a slower rate (from 46 to 20 microg L(-1) during the same time). Young fern plants were more efficient in removing arsenic than were older fern plants of similar size. The addition of a supplement of phosphate-free Hoagland nutrition to the groundwater had little effect on arsenic removal, but the addition of phosphate nutrition significantly reduced its arsenic affinity and, thus, inhibited the arsenic removal. This study suggested that Chinese Brake has some potential to remove arsenic from groundwater.     

蜈蚣草中砷超富集的分子机制研究进展

砷是一种毒性很强的类金属元素,土壤砷污染可引发一系列食品安全问题,进而威胁人类健康。蜈蚣草具有极强的富集砷的能力,在砷污染土壤的植物修复中具有重要的应用价值。深入阐释蜈蚣草超富集砷的分子机制是植物修复技术的核心理论基础。文中综述了蜈蚣草超富集砷的组学研究进展,以及目前鉴定到的砷富集过程中的重要分子元件,并对未来的研究方向和趋势进行了展望。     

Distributions of arsenic and essential elements in pinna of arsenic hyperaccumulator Pteris vittata L.

The distributions of arsenic and 6 essential elements in the pinna of As hyperaccumulator, Pteris vittata L., were studied using synchrotron radiation X-ray fluorescence (SRXRF). Significant correlation between the distribution and mobility of the elements revealed that SRXRF study on the elemental distribution was feasible to inspect the transportations of elements in plants. The distribution of As in the pinna showed that As had great abilities to be transported in xylem vessels and from xylem to mesophyll. The distribution of K, one of the most mobile elements in plants, was similar to that of As, whereas the distributions of Fe and Ca with less mobility in plants were almost opposite to that of As in the pinna.     

Role of trichome of Pteris vittata L. in arsenic hyperaccu-mulation

Heavy metal pollution of soils, caused by various anthropogenic sources, is a major environmental problem. Due to its cost-effectiveness and environ-mental friendliness, phytoremediation of arsenic-con- taminated soils has attracted more and more attention. An arsenic (As) hyperaccumulator, Chinese brake (Pteris vittata L.) was discovered by Chen et al. in China[1]. The field phytoremediation in Chenzhou City, Hunan Province has been successfully carried out by Chen et al. since 2000[2,3].…     

Phytoremediation of arsenic contaminated soil by Pteris vittata L. I. Influence of phosphatic fertilizers and repeated harvests

A greenhouse experiment was conducted to evaluate the effectiveness of diammonium phosphate (DAP), single superphosphate (SSP) and two growing cycles on arsenic removal by Chinese Brake Fern (Pteris vittata L.) from an arsenic contaminated Typic Haplustept of the Indian state of West Bengal. After harvest of Pteris vittata the total, Olsen's extractable and other five soil arsenic fractions were determined. The total biomass yield of P. vittata ranged from 10.7 to 16.2 g pot(-1) in first growing cycle and from 7.53 to 11.57 g pot(-1) in second growing cycle. The frond arsenic concentrations ranged from 990 to 1374 mg kg(-1) in first growing cycle and from 875 to 1371 mg kg(-1) in second growing cycle. DAP was most efficient in enhancing biomass yield, frond and root arsenic concentrations and total arsenic removal from soil. After first growing cycle, P. vittata reduced soil arsenic by 10 to 20%, while after two growing cycles Pteris reduced it by 18 to 34%. Among the different arsenic fractions, Fe-bound arsenic dominated over other fractions. Two successive harvests with DAP as the phosphate fertilizer emerged as the promising management strategy for amelioration of arsenic contaminated soil of West Bengal through phyotoextraction by P. vittata.     

蜈蚣草砷超富集机制及其在砷污染修复中的应用

蕨类植物蜈蚣草能够从土壤中吸收砷,并储存于地上部分羽叶的液泡中。蜈蚣草具有高效的抗氧化系统,以降低砷的毒害;其砷酸还原系统和液泡区隔化是蜈蚣草进行砷解毒和砷超富集的重要机制。本文综述了目前蜈蚣草砷超富集机制研究的主要进展,并对其在修复砷污染环境的应用中进行了讨论。     

Phytoremediation of an arsenic-contaminated site using Pteris vittata L.: a two-year study

A field study was conducted to determine the efficiency of Chinese brake fern (Pteris vittata L.), an arsenic hyperaccumulator, on removal of arsenic from soil at an arsenic-contaminated site. Chinese brake ferns were planted on a site previously used to treat wood with chromated copper arsenate (CCA). Arsenic concentrations in surface and profile soil samples were determined for 2000, 2001, and 2002. In both 2001 and 2002, senesced and senescing fronds only, as well as all fronds, were harvested. Frond arsenic concentrations were not significantly different between the three harvests. Compared to senesced fronds, live fronds resulted in the greatest amount of arsenic removal. There were no significant differences in soil arsenic concentrations between 2000, 2001, and 2002, primarily due to the extreme variability in soil arsenic concentrations. However, the mean surface soil arsenic was reduced from 190 to 140 mg kg(-1). Approximately 19.3 g of arsenic were removed from the soil by Chinese brake fern. Therefore, this fern is capable of accumulating arsenic from the CCA -contaminated site and may be competitive, in terms of cost, to conventional remediation systems. However, better agronomic practices are needed to enhance plant growth and arsenic uptake to obtain maximum soil arsenic removal and to minimize remediation time.     

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.     

A Critical Review of the Arsenic Uptake Mechanisms and Phytoremediation Potential of Pteris vittata

The discovery of the arsenic hyperaccumulator, Pteris vittata (Chinese brake fern), has contributed to the promotion of its application as a means of phytoremediation for arsenic removal from contaminated soils and water. Understanding the mechanisms involved in arsenic tolerance and accumulation of this plant provides valuable tools to improve the phytoremediation efficiency. In this review, the current knowledge about the physiological and molecular mechanisms of arsenic tolerance and accumulation in P. vittata is summarized, and an attempt has been made to clarify some of the unresolved questions related to these mechanisms. In addition, the capacity of P. vittata for remediation of arsenic-contaminated soils is evaluated under field conditions for the first time, and possible solutions to improve the remediation capacity of Pteris vittata are also discussed.     

Phytoremediation of arsenic contaminated soil by Pteris vittata L. II. Effect on arsenic uptake and rice yield

A greenhouse experiment evaluated the effect of phytoextraction of arsenic from a contaminated soil by Chinese Brake Fern (Pteris vittata L.) and its subsequent effects on growth and uptake of arsenic by rice (Oryza sativa L.) crop. Pteris vittata was grown for one or two growing cycles of four months each with two phosphate sources, using single super phosphate (SSP) and di-ammonium phosphate (DAP). Rice was grown on phytoextracted soils followed by measurements of biomass yield (grain, straw, and root), arsenic concentration and, uptake by individual plant parts. The biomass yield (grain, straw and rice) of rice was highest in soil phytoextracted with Pteris vittata grown for two cycles and fertilized with diammonium phosphate (DAP). Total arsenic uptake in contaminated soil ranged from 8.2 to 16.9 mg pot(-1) in first growing cycle and 5.5 to 12.0 mg pot(-1) in second growing cycle of Pteris vittata. There was thus a mean reduction of 52% in arsenic content of rice grain after two growing cycle of Pteris vittata and 29% after the one growing cycle. The phytoextraction of arsenic contaminated soil by Pteris vittata was beneficial for growing rice resulted in decreased arsenic content in rice grain of <1 ppm. There was a mean improvement in rice grain yield 14% after two growing cycle and 8% after the one growing cycle of brake fern.     

不同生态型摩西球囊霉菌株对蜈蚣草砷吸收的影响

砷超富集植物——蜈蚣草无论是在野外或是在室内均能被丛枝菌根真菌(AM真菌)侵染,但其对蜈蚣草砷吸收及转运的机理尚不清晰.本研究将分离于湖南省郴州市金川塘某铅锌尾矿蜈蚣草根际土壤(Glomus mosseae BGC GD01,简称污染菌株)和云南省未污染土壤(G.mosseae BGC YN05,简称非污染菌株)的2种摩西球囊霉菌株分别接种于非污染生态型和污染生态型蜈蚣草根际,8周后利用菌根化蜈蚣草幼苗在浓度为100 μmol·L-1砷(Na2HAsO4·7H2O)营养液中进行为期24 h的水培试验.结果表明,2种生态型摩西球囊霉菌株分别与蜈蚣草形成中等程度侵染,侵染率为25.2％ ～31.3％.无论是接种污染菌株或是非污染菌株,均明显促进了蜈蚣草根部对磷的吸收.在24 h水培试验期间,接种非污染菌株显著促进了蜈蚣草根部砷的吸收,但接种污染菌株对蜈蚣草根部砷吸收的促进作用有限,说明AM真菌对蜈蚣草砷吸收存在种内差异.     

Root exudates and arsenic accumulation in arsenic hyperaccumulating Pteris vittata and non-hyperaccumulating Nephrolepis exaltata

This study compared the roles of root exudates collected from two fern species, the As hyperaccumulating Chinese Brake fern (Pteris vittata L.) and the As-sensitive Boston fern (Nephrolepis exaltata L.), on As-mobilization of two As minerals (aluminum arsenate and iron arsenate) and a CCA (chromated copper arsenate)-contaminated soil as well as plant As accumulation. Chinese Brake fern exuded 2 times more dissolved organic carbon (DOC) than Boston fern and the difference was more pronounced under As stress. The composition of organic acids in the root exudates for both ferns consisted mainly of phytic acid and oxalic acid. However, Chinese Brake fern produced 0.46 to 1.06 times more phytic acid than Boston fern under As stress, and exuded 3–5 times more oxalic acid than Boston fern in all treatments. Consequently, root exudates from Chinese Brake fern mobilized more As from aluminum arsenate (3–4 times), iron arsenate (4–6 times) and CCA-contaminated soil (6–18 times) than Boston fern. Chinese Brake fern took up more As and translocated more As to the fronds than Boston fern. The molar ratio of P/As in the roots of Chinese Brake fern was greater than in the fronds whereas the reverse was observed in Boston fern. These results suggested that As-mobilization from the soil by the root exudates (enhancing plant uptake), coupled with efficient As translocation to the fronds (keeping a high molar ratio of P/As in the roots), are both important for As hyperaccumulation by Chinese Brake fern.     

Phytofiltration of arsenic-contaminated groundwater using Pteris vittata L.: effect of plant density and nitrogen and phosphorus levels

This field-scale hydroponic experiment investigated the effects of plant density and nutrient levels on arsenic (As) removal by the As-hyperaccumulator Pteris vittata L. (Chinese brake fern). All ferns were grown in plastic tanks containing 30 L of As-contaminated groundwater (130 microg x L(-1) As) collected from South Florida. The treatments consisted of four plant densities (zero, one, two, or four plants per 30 L), two nitrogen (N) concentrations (50% or 100% of 0.25-strength Hoagland solution [HS]), and two phosphorous (P) concentrations (15% and 30% of 0.25 strength HS). While low P was more effective than high P for plant As removal initially, N levels showed little effect. At 15% P, it took 3 wk for the ferns at a plant density of four to reduce As to less than 10 microg L(-1) (USEPA and WHO standard), whereas it took 4-6 wk at plant densities of one or two. For reused ferns, established plants with more extensive roots than "first-time" ferns, a low plant density of one plant/30 L was more effective, reducing As in water to less than 10 microg L(-1) in 8 h. This translates to an As removal rate of 400 microg h(-l) plant(-1), which is the highest rate reported to date. Arsenic-concentration in tanks with no plants as a control remained high throughout the experiment. Using more established ferns supplemented with dilute nutrients (0.25 HS with 25% N and 15% P) with optimized plant density (one plant per 30 L) reduced interplant competition and secondary contamination from nutrients, and can be recommended for phytofiltration of As-contaminated groundwater. This study demonstrated that P. vittata is effective in remediating As-contaminated groundwater to meet recommended standards.     

Development of suitable hydroponics system for phytoremediation of arsenic-contaminated water using an arsenic hyperaccumulator plant Pteris vittata

In this study, we found that high-performance hydroponics of arsenic hyperaccumulator fern Pteris vittata is possible without any mechanical aeration system, if rhizomes of the ferns are kept over the water surface level. It was also found that very low-nutrition condition is better for root elongation of P. vittata that is an important factor of the arsenic removal from contaminated water. By the non-aeration and low-nutrition hydroponics for four months, roots of P. vittata were elongated more than 500 mm. The results of arsenate phytofiltration experiments showed that arsenic concentrations in water declined from the initial concentrations (50?μg/L, 500?μg/L, and 1000?μg/L) to lower than the detection limit (0.1?μg/L) and about 80% of arsenic removed was accumulated in the fern fronds. The improved hydroponics method for P. vittata developed in this study enables low-cost phytoremediation of arsenic-contaminated water and high-affinity removal of arsenic from water.     

刈割对蜈蚣草的砷吸收和植物修复效率的影响

以野生苗移栽的蜈蚣草为试材 ,通过盆栽试验研究了收获次数对蜈蚣草生长、砷吸收和植物修复效率的影响。结果表明 :在 3次收获中 ,随着收获次数的增加 ,不同砷浓度处理之间蜈蚣草生物量的差异逐步缩小 ;不加砷的对照处理中 ,每次收获后的砷吸收速率下降趋势 ,而在 3个加砷处理中 ,第 2次收获和第 3次收获的蜈蚣草的吸砷速率为 6 3～ 75 μg/ (plant· d)、4 4～ 5 5μg/ (plant· d) ,均显著高于第 1次收获时的吸收速率。表明多次收获并没有降低砷的积累速度。由此可见 ,通过适当增加蜈蚣草的收获次数是提高砷修复效率的一种策略     

砷、钙对蜈蚣草中金属元素吸收和转运的影响

蜈蚣草是砷的超富集植物和钙质土壤的指示植物。本试验在砂培条件下,研究砷、钙对蜈蚣草吸收和转运必需金属元素K、Mg、Mn、Fe、Zn和Cu的影响。结果表明。提高营养液中的砷浓度显著降低根部Mg和Zn的吸收。但对根部其它元素的浓度没有明显影响;叶柄中的Mn和地上部的Fe浓度因介质中添加砷而显著减少。其它元素在地上部的分布不受抑制。添加砷限制Fe从地下部向地上部转运,但促进其从叶柄向羽叶中运输;另外,还显著促进Mn由叶柄向羽叶和Zn由根向羽叶的转运。提高钙处理浓度对蜈蚣草吸收Fe、Zn、Cu无显著影响,但显著限制K、Mg和Mn的吸收。Mn是研究的6种金属元素中惟一一种明显向地上部转运富集的元素。从根部到羽叶中。金属元素间的相关性增强,在根部Ca与各种金属元素都无相关性;叶柄中Ca和Fe浓度呈极显著正相关;在羽叶中,Ca与K、Mg、Mn和Zn浓度呈显著负相关。     

砷超富集植物蜈蚣草原生质体的分离及其抗砷性分析

蜈蚣草（Pteris vittata）是一种砷超富集植物,能够通过根从土壤中吸收砷,并将其输送至羽叶中富集.为了探索蜈蚣草单个细胞在砷积累和砷抗性中的特性,本文首次通过酶解方法获得了这一砷超富集蕨类植物的原生质体,并研究了原生质体在不同浓度砷胁迫下的生活力.结果显示,蜈蚣草原生质体的抗砷性远高于烟草原生质体的抗砷性,与其整体植株的抗性一致.这为探索砷抗性和超富集机理提供了一个新的研究体系.