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。     

超富集植物蜈蚣草中砷化学形态的EXAFS研究

采用同步辐射扩展X射线吸收精细结构(SR EXAFS)技术研究了超富集植物蜈蚣草(Pteris vittata L.)中As的化学形态及其在转运过程中的变化.结果表明,蜈蚣草中的As主要以As(Ⅲ)与O配位的形态存在.As(Ⅴ)被植物吸收后,很快转化为As(Ⅲ),其转化过程主要发生在根部.As(Ⅲ)向地上部转运的过程中价态基本不变.在植物的根部和部分叶柄中存在少量与As-GSH相似的As-S结合方式,但是在As含量最高的羽叶中基本上未发现这种结合方式.与需要提取和分离过程的化学方法相比,采用EXAFS方法研究植物中的砷形态不需经过预分离或化学预处理就可以直接测定植物样品中元素的化学形态,因此可以避免样品预处理过程对As形态的干扰,并获得可靠的砷化学形态方面的信息.     

超富集植物蜈蚣草中砷化学形态的EXAFS研究

采用同步辐射扩展X射线吸收精细结构(SREXAFS)技术研究了超富集植物蜈蚣草(PterisvittataL.)中As的化学形态及其在转运过程中的变化。结果表明,蜈蚣草中的As主要以As(Ⅲ)与O配位的形态存在。As(V)被植物吸收后,很快转化为As(Ⅲ),其转化过程主要发生在根部。As(Ⅲ)向地上部转运的过程中价态基本不变。在植物的根部和部分叶柄中存在少量与As-GSH相似的As-S结合方式,但是在As含量最高的羽叶中基本上未发现这种结合方式。与需要提取和分离过程的化学方法相比,采用EXAFS方法研究植物中的砷形态不需经过预分离或化学预处理就可以直接测定植物样品中元素的化学形态,因此可以避免样品预处理过程对As形态的干扰,并获得可靠的砷化学形态方面的信息。     

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--蜈蚣草孢子的无菌培养

1植物名称蜈蚣草(Pteris vittata). 2材料类别成熟的孢子. 3培养条件所用培养基为:(1)MS;(2)1/2MS;(3)1/5MS;(4)1/10MS;(5)蒸馏水;(6)Knop's.1/2MS、1/5MS、1/10MS指大量和微量元素为MS培养基全量的1/2、1/5、1/10,上述培养基均使用MS培养基全量的铁盐和有机成分,1.0%琼脂,3.0%蔗糖,pH 5.8.培养室温度为25℃;日光灯光源,光照度2 000～2 300 lx,光照时间12 h·d-1.     

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。     

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.     

耐砷促生菌对超富集植物蜈蚣草砷吸收及根际微生物群落的调控作用

【目的】分析添加外源促植物生长微生物(plant growth-promoting bacteria,PGPB)对植物生长、砷富集和根际微生物的影响,为植物-微生物联合修复砷污染土壤提供参考。【方法】通过添加外源PGPB,研究蜈蚣草生物量和砷富集量与外源微生物促植物生长特性的关系,采用高通量测序技术分析蜈蚣草根际微生物群落在外源PGPB干预下的变化规律。【结果】2株根际菌(假单胞菌PG12、芽孢杆菌R19)和1株内生菌(恶臭假单胞菌S6)具备典型的促植物生长特性,对蜈蚣草的促生作用顺序为：PG12>S6>R19,与对照组相比,生物量分别提高了234%(P<0.01)、136%(P<0.01)和67%;添加外源PGPB后,蜈蚣草砷含量从对照的18.50 mg提高到了31.25-46.95 mg,增幅高达153%(PG12)和139%(S6),对应的蜈蚣草砷浓度从2616.34mg/kg降至1348.04-2 156.23 mg/kg,呈现出典型的砷“稀释效应”;α多样性指数Sobs、Chao和Ace显示,仅R19处理显著提高了根际微生物的群落多样性,而β多样性指数...     

重金属超富集植物及植物修复技术研究进展

植物修复技术（Phytoremediation)是近年来发展起来的一种主要用于清除土壤重金属污染的绿色生态技术,重金属超富集植物（hyperaccumulator)及植物修复技术是当前学术界研究的热点领域,目前虽已有Cd、Co、Cr、Cu、Mn、Ni、Pb、Zn等超富集植物发现的报道,但尚无一例报道来自于中国,中国具有广袤的国土面积、丰富的植物类型和多种（处）古老的矿山开采与冶炼场所,在中国开展超富集植物的寻找,研究与开发工作,将会有重要突破,并具有重要的理论与实践意义,本文拟就国内外在这一领域的研究进展作一简要综述。     

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.     

Effect of Fluoride on Arsenic Uptake from Arsenic-Contaminated Groundwater using Pteris vittata L.

High-arsenic groundwater in inland basins usually contains high concentrations of fluoride. In the present study, the effects of fluoride on arsenic uptake by Pteris vittata and on arsenic transformation in growth media were investigated under greenhouse conditions. After P. vittata was hydroponically exposed to 66.8 μM As (V) in the presence of 1.05 mM F^? in the form of NaF, KF, or NaF+KF for 10 d, no visible toxicity symptoms were observed, and there were not significant differences in the dry biomass among the four treatments. The results showed that P. vittata tolerated F^? concentrations as high as 1.05 mM but did not accumulate fluoride in their own tissues. Arsenic uptake was inhibited in the presence of 1.05 mM F^?. However, in hydroponic batches with 60 μM As (III) or 65 μM As (V), it was found that 210.6 and 316.0 μM F^? promoted arsenic uptake. As(III) was oxidized to As(V) in the growth media in the presence and absence of plants, and F^? had no effect on the rate of As(III) transformation. These experiments demonstrated that P. vittata was a good candidate to remediate arsenic-contaminated groundwater in the presence of fluoride. Our results can be used to develop strategies to remediate As-F-contaminated water using P. vittata.     

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.     

Elemental allelopathy by an arsenic hyperaccumulating fern,Pteris vittata L.

Aims The functional advantages of arsenic (As) hyperaccumulation by plants are poorly understood. One proposed benefit, termed elemental allelopathy, occurs when hyperaccumulated As is cycled from the plant back into the top layer of soil, allowing As hyperaccumulators to gain an advantage over intolerant species by increasing soil As concentrations ([ As]) underneath their canopy. To date, there are no studies that detail the presence of increased soil [ As] associated with As hyperaccumulators. In this study, we documented variation in the soil [ As] associated with the Chinese brake fern, Pteris vittata L. and also compared the effects of environmentally relevant soil and solution [ As] on competitor plant growth.Methods Four populations of P. vittata were identified in central Florida, USA. P. vittata tissue samples and soil samples were collected at the base of and at 3 m away from ferns in each population (n = 36). Five sample locations were randomly selected from each site, and soils from the base and 3 m away from each fern were collected to examine the effects of naturally occurring soil [ As] on the germination and growth of a potential competitor plant (Oxalis stricta). Solutions with increasing [ As] were also used to examine the threshold for negative effects of [ As] on O. stricta growth. [ As] were measured using inductively coupled plasma mass spectrometry (ICP-MS).Important findings Overall, soil [ As] from the base of ferns was nearly twice that of soil 3 m away indicating that ferns hyperaccumulate As. However, ferns and their associated soil, contained different [ As] depending on their collection site, indicating that these populations accumulate and use [ As] differently. O. stricta growth decreased and germination was delayed as solution and soil [ As] increased. However, the relative distance from the fern that the soil was collected from did not affect growth, which would be expected with elemental allelopathy. Our results show that P. vittata is associated with higher soil [ As] and these concentrations are sufficient to inhibit growth of competitors. However, the absence of a strong inhibitory relationship associated with proximity to the fern across all locations suggests that the possible functional advantages of elemental allelopathy may depend on site specific characteristics.     

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.     

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].…