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A fern that hyperaccumulates arsenic(一种高效富集砷的蕨类植物)

 2006-06-21    153  

A hardy, versatile, fast-growing plant helps to remove arsenic from contaminated soils.Contamination of soils with arsenic,which is both toxic and carcinogenic,is widespread . We have discovered that the fern Pteris vittata (brake fern) is extremely efficient in extracting arsenic from soils and translocating it into its above-ground biomass. This plant — which, to our knowledge, is the first known arsenic hyperaccumulator as well as the first fern found to function as a hyperaccumulator — has many attributes that recommend it for use in the remediation of arsenic-contaminated soils.

一种高效的、多效能的、快速生长的植物被用来去除被污染土壤里的砷。土壤中的砷污染物分布广泛,并且有剧毒能致癌。我们发现这种蕨类植物“蜈蚣草”在富集土壤中的砷,并将其转移到它们的地上部分植物体的方面是极其有效的。这种植物是我们所知的范围内最早知道的湿生铬超积累植物,也是第一种作为湿生积累植物的蕨类植物,在修复土壤的砷污染等方面有着很多的特质。

We found brake fern growing on a site in Central Florida contaminated with chromated copper arsenate (Fig. 1a). We analysed the fronds of plants growing at the site for total arsenic by graphite furnace atomic absorption spectroscopy. Of 14 plant species studied, only brake fern contained large amounts of arsenic (As;3,280–4,980 p.p.m.). We collected additional samples of the plant and soil from the contaminated site (18.8–1,603 p.p.m. As) and from an uncontaminated site (0.47–7.56 p.p.m. As). Brake fern extracted arsenic efficiently from these soils into its fronds: plants growing in the contaminated site contained 1,442–7,526 p.p.m. arsenic and those from the uncontaminated site contained 11.8–64.0 p.p.m.These values are much higher than those typical for plants growing in normal soil, which contain less than 3.6 p.p.m. of arsenic .

我们发现蜈蚣草生长在佛罗里达中部的一个被铬酸铜砷盐污染了的地方(图 1a),并用石墨炉原子分光光度法分析生长在这块地上的所有类型植株体内的总砷量。在分析的14种植株里,只有蜈蚣草内含有大量的砷(As;3,280–4,980 p.p.m.)。我们从这块被污染的位点(18.8–1,603 p.p.m. As)和一块没被污染的位点(0.47–7.56 p.p.m. As)处收集了这种植物和土壤另外的一些样品。蜈蚣草有效地从这些土壤中提取了砷,并转化为它的生物量:生长在被污染地方的植株含有1,442–7,526 p.p.m.的砷,而那些生长在未被污染地方的植株含有11.8–64.0 p.p.m.的砷。这些值要远高于生长于普通土壤里的植物类型,那些植物只含有少于3.6 p.p.m.的砷。

As well as being tolerant of soils containing as much as 1,500 p.p.m. arsenic, brake fern can take up large amounts of arsenic into its fronds in a short time (Table 1).Arsenic concentration in fern fronds growing in soil spiked with 1,500 p.p.m. arsenic increased from 29.4 to 15,861 p.p.m. in two weeks. Furthermore, in the same period,ferns growing in soil containing just 6 p.p.m. arsenic accumulated 755 p.p.m. of arsenic in their fronds, a 126-fold enrichment. Arsenic concentrations in brake fern roots were less than 303 p.p.m., where as those in the fronds reached 7,234 p.p.m.(Fig. 1b). Addition of 100 p.p.m. arsenic significantly stimulated fern growth, resulting in a 40% increase in biomass compared with the control (data not shown).

作为能耐受土壤中含有差不多1,500 p.p.m.量砷的植物,蜈蚣草可以在短时间内去除大量的砷并转化为它的生物量(表 1)。含1,500 p.p.m.砷的土壤中生长的蕨类植物所含的砷浓度在两周内从29.4 上升到15,861 p.p.m.。进一步而言,土壤中只含6 p.p.m.砷的蕨类植物在它们的体内积聚了755 p.p.m.的砷,是原来丰度的126倍。同时,在蜈蚣草根部的砷浓度少于303 p.p.m.,而其植物体内的砷浓度却高达7,234 p.p.m.(图 1b)。与对照组相比(没有标明时间),增加100 p.p.m.的砷显著地刺激了它的生长,并导致了生物量上40%的增长。

After 20 weeks of growth, the plant was extracted using a solution of 1:1 methanol:water to speciate arsenic with high-performance liquid chromatography–inductively coupled plasma mass spectrometry. Almost all arsenic was present as relatively toxic inorganic forms, with little detectable organoarsenic species . The concentration of As(III) was greater in the fronds (47–80%) than in the roots (8.3%), indicating that As(V) was converted to As(III) during translocation from roots to fronds.

在20个星期的生长之后,用1:1甲醇水溶液提取这种植物中的砷,采用高效液相色谱与感应耦合等离子体质谱联用来分析砷的形态。几乎所有的砷都是以有毒的无机形态存在的,只有少数种类是有机砷。在植物体内(47–80%)三价砷的浓度要高于根部(8.3%),说明在从根部转运到植物体内的过程中五价砷转化为了三价砷。

As well as removing arsenic from soils containing different concentrations of arsenic (Table 1), brake fern also removed arsenic from soils containing different arsenic species (Fig. 1c). Again, up to 93% of the arsenic was concentrated in the fronds.Although both FeAsO4 and AlAsO4 are relatively insoluble in soils , brake fern hyperaccumulated arsenic derived from these compounds into its fronds (136–315 p.p.m.) at levels 3–6 times greater than soil arsenic.

与转运土壤中不同浓度的砷的过程一样(Table 1),蜈蚣草也转运土壤中不同形态的砷(图 1c)。此外,93%的砷被浓缩到植物体内。尽管FeAsO4 和AlAsO4在土壤中都难溶,但是蜈蚣草仍能积聚这些混合物中的砷,并转移到它的体内,而且是土壤中砷浓度的3~6倍。

Brake fern is mesophytic and is widely cultivated and naturalized in many areas with a mild climate. In the United States,it grows in the southeast and in southern California . The fern is versatile and hardy,and prefers sunny (unusual for a fern) and alkaline environments (where arsenic is more available). It has considerable biomass, and is fast growing, easy to propagate,and perennial.

蜈蚣草是一种中生植物,广泛地种植或移栽在许多中温气候的地方。在美国,它生长在加里佛尼亚州东南部和南部地区。蜈蚣草是多效用且生命力顽强的,喜好阳光(对一般的蕨类植物都是这样)和碱性环境(砷更易存在),有着可观的生物量,而且生长迅速,繁殖力强,多年生。

We believe this is the first report of significant arsenic hyperaccumulation by an unmanipulated plant. Brake fern has great potential to remediate arsenic-contaminated soils cheaply and could also aid studies of arsenic uptake,translocation,speciation,distribution and detoxification in plants.

我们相信这是首次关于湿生铬超积累植物的报道。蜈蚣草有巨大的潜力用来廉价地修复砷污染土壤,也可以用来学习砷在植物中提取、迁移、转化、分配和解毒的过程。

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