东南景天对锌、镉复合污染的反应及其对锌、镉的吸收和积累特性

东南景天(Sedum alfredii Hance)已被鉴定为一种中国原生的新的锌超积累植物。 本文主要研究了锌(Zn)、镉(Cd)复合处理水平对东南景天的生长及其对锌、镉的吸收积累特性的影响。 结果表明,在Zn/Cd复合水平为500/100 祄ol/L时,植物生长最佳。Zn/Cd在东南景天叶片、茎部和根系中含量随着Zn/Cd处理水平的提高而增高。在Zn/Cd 复合水平为50/400 祄ol/L时茎叶中Cd含量达最高,其中叶片Cd含量达12.1 g/kg;在Zn/Cd 复合水平为1 000/50 祄ol/L时茎叶中Zn含量达最高, 其中茎中Zn含量达 23.2 g/kg。 植株各部位Cd含量的分布为:叶片>茎>>根系,而Zn在体内的分布为: 茎>叶片>>根系。 Zn、Cd在地上部和根部的积累量也随着处理水平的提高而增加,分别在Zn/Cd复合水平为250/400和500/100 祄ol/L下达高峰值。 东南景天地上部积累最高Zn和Cd的量分别达11和5 g/plant, 其比根系的积累量分别大10和25余倍。 Zn、Cd对东南景天的生长、吸收积累的相互作用依赖于Zn/Cd复合水平和植物部位。 在适宜Zn/Cd 处理水平范围内,Zn和Cd的吸收和积累具有相互促进作用。 高Zn或高Cd处理均抑制了植物对Zn和Cd的吸收和积累。 本研究结果表明,东南景天不仅具有忍耐高Zn/Cd复合污染,而且具有超量积累Zn和Cd的特异能力。 它为进一步研究植物Zn、Cd     

Lead induced changes in the growth and antioxidant metabolism of the lead accumulating and non-accumulating ecotypes of Sedum alfredii

The phytotoxicity and antioxidative adaptations of lead （Pb） accumulating ecotype （AE） and non-accumulating ecotype （NAE） of Sedum alfredii Hance were investigated under different Pb treatments involving 0, 0.02 mmol/L Pb, 0.1 mmol/L Pb and 0.1 mmol/L Pb/0.1 mmol/L ethylenediaminetetraacetic acid （EDTA） for 6days. With the increasing Pb level, the Pb concentration in the shoots of AE plants enhanced accordingly, and EDTA supply helped 51% of Pb translocation to shoots of AE compared with those treated with 0.1 mmol/L Pb alone. Moreover, the presence of EDTA alleviated Pb phytotoxicity through changes in plant biomass, root morphology and chlorophyll contents. Lead toxicity induced hydrogen peroxide （H2O2） accumulation and lipid peroxidation in both ecotypes of S. alfredii. The activities of superoxide dismutase （SOD）, guaiacol peroxidase （G-POD）, ascorbate peroxidase, and dehydroascorbate reductase elevated in both leaves and roots of AE as well as in leaves of NAE with the increasing Pb levels, but SOD and G-POD declined in roots of NAE. Enhancement in glutathione reductase activity was only detected in roots of NAE while a depression in catalase activity was recorded in the leaves of NAE. A significant enhancement in glutathione and ascorbic acid （AsA） levels occurred in both ecotypes exposed to Pb and Pb/EDTA treatment compared with the control, however, the differences between these two treatments were insignificant. The dehydroascorbate （DHA） contents in roots of both ecotypes were 1.41 to 11.22-fold higher than those in leaves, whereas the ratios of AsA to DHA （1.38 to 6.84） in leaves altering more to the reduced AsA form were much higher than those in roots. These results suggested that antioxidative enzymes and antioxidants play an important role in counteracting Pb stress in S. alfredii.     

四种景天属植物对锌吸收和累积差异的研究

采用营养液培养试验,比较研究了4种景天属植物对Zn的吸收、积累和运输特性.结果表明,东南景天(Sedum alfredii Hance)耐Zn毒的能力远强于珠芽景天(S. sarmentosum Bunge)、凹叶景天(S. bulbiferum Makino)和垂盆草(S. emarginatum Migo),其地上部和根系的干物质产量随着Zn浓度的增加而逐渐减少;当浓度≤40 mg*L-1时,东南景天的地上部和根系的干物质产量均随Zn浓度的增加而增加,其地上部Zn含量、积累量及其Zn运输速率均显著高于珠芽景天、凹叶景天和垂盆草;当Zn浓度低于80 mg*L-1时,东南景天地上部Zn含量随着营养液中Zn浓度的增加而增加,在80 mg*L-1浓度,其地上部Zn含量高达19.09 mg*g-1.东南景天的地上部Zn含量/根系Zn含量的比值大于1,而株芽景天、凹叶景天和垂盆草的地上部Zn含量/根系Zn含量比值小于1.东南景天是在我国首次发现的具有生物量大、生长速率快的一种新的Zn超积累植物.     

古老铅锌矿区生态型东南景天对锌耐性及超积累特性的研究

 植物长期生长在重金属污染的生境中,逐渐进化成不同的生态型。通过调查中国东南部古老Pb/zn矿和非矿山生境中的植物种群,发现生长在古老Pb／Zn矿的东南景天(Sedum alfredii Hance)是一种新的Zn超积累植物。在自然和控制条件下,古老Pb／Zn矿生态型比非矿山生态型植株的茎粗、叶片大、植株高。在矿山土壤Zn有效含量为105.5～325.4mg·kg-1时,矿山生态型东南景天植株地上部Zn含量为4134～5000mg·kg-1;当营养液中Zn浓度为1223.6μmol时,其Zn含量高达2％。在相同Zn浓度下,矿山生态型地上部Zn含量比非矿山生态型高30倍左右。两种生态型体内Zn分布也不同,古老铅锌矿山生态型的不同器官中Zn含量以茎>叶片>根系,而非矿山生态型则以根系>茎>叶片。古老铅锌矿山生态型地上部积累的Zn占植株总积累量的90％以上,其中叶片和茎分别占41.66％±5.46％和54.75％±5.87％;非矿山生态型各器官中积累的Zn远远低于古老铅锌矿山生态型,各器官中积累的Zn以茎>根系>叶片。本研究表明,这两种生态型东南景天的发现,为今后探讨植物耐高Zn胁迫和超积累Zn的微进化过程提供了非常有价值的材料,也为Zn污染土壤的植物修复提供了一种很有潜力的候选材料。     

Cleaning up of heavy metals-polluted water by a terrestrial hyperaccumulator Sedum alfredii Hance

Sedum alfredii Hance is a terrestrial zinc/cadmium （Zn/Cd）-hyperaccumulating and lead （Pb）-accumulating plant. Previous studies on S. alfredii were mostly focused on its physiological mechanism of heavy metal uptake and the application in phytoextraction of metals from contaminated soils. In this study, we evaluated the application potential of S. alfredii in the cleanup of heavy metals from contaminated lake water. Our research revealed that changing pH in lake water would not make particular difference on the final accumulation amount of heavy metals, because the acidic water environment negatively affected plant growth compared with the neutral and alkaline environments, but was more conducive for heavy metal absorption and accumulation. In addition, S. alfredii showed an increase of approximately 2.2-fold in dry weight （DW） when cultured with lake water for 25 d. At the same time, it accumulated approximately 5.0 mg/kg DW of Cd and 41.4 mg/kg DW of Pb. The absorption of heavy metals was highly effective during the first 10 d of culture. Also, the quality of lake water was greatly improved after only 2-d cleanup by S. aifredii. In general, this hyperaccumulator exhibits great potential for application in the cleanup of heavy metals-polluted waters.     

四种景天属植物对锌吸收和累积差异的研究

采用营养液培养试验 ,比较研究了 4种景天属植物对Zn的吸收、积累和运输特性。结果表明 ,东南景天(SedumalfrediiHance)耐Zn毒的能力远强于珠芽景天 (S .sarmentosumBunge)、凹叶景天 (S .bulbiferumMakino)和垂盆草 (S .emarginatumMigo) ,其地上部和根系的干物质产量随着Zn浓度的增加而逐渐减少 ;当浓度≤ 40mg·L-1时 ,东南景天的地上部和根系的干物质产量均随Zn浓度的增加而增加 ,其地上部Zn含量、积累量及其Zn运输速率均显著高于珠芽景天、凹叶景天和垂盆草 ;当Zn浓度低于 80mg·L-1时 ,东南景天地上部Zn含量随着营养液中Zn浓度的增加而增加 ,在 80mg·L-1浓度 ,其地上部Zn含量高达 19.0 9mg·g-1。东南景天的地上部Zn含量 /根系Zn含量的比值大于 1,而株芽景天、凹叶景天和垂盆草的地上部Zn含量 /根系Zn含量比值小于 1。东南景天是在我国首次发现的具有生物量大、生长速率快的一种新的Zn超积累植物     

The effects of heavy metal pollution on genetic diversity in zinc/cadmium hyperaccumulator Sedum alfredii populations

The genetic diversity and population structure of seven populations of Sedum alfredii growing in lead/zinc (Pb/Zn) mine spoils or in uncontaminated soils from eastern and southern China were investigated using random amplified polymorphic DNA (RAPD) technology. Four of the sampled sites were heavily contaminated with heavy metals (Zn, Cd, Pb), and extremely high concentrations of Zn, Cd, and Pb were found among these corresponding populations. A significant reduction of genetic diversity was detected in the mining populations. The reduction of genetic diversity could be derived from a bottleneck effect and might also be attributed to the prevalence of vegetative reproduction of the mining populations. Analysis of molecular variance (AMOVA) and the unweighted pair group method with arithmetic mean (UPGMA) tree derived from genetic distances further corroborated that the genetic differentiation between mine populations and uncontaminated populations was significant. Polymorphism with the heavy metal accumulation capability of S. alfredii probably due to the genetic variation among populations and heavy metal contamination could have more impact on the genetic diversity and population structure of S. alfredii populations than geographic distance.     

Phytochelatin synthesis plays a similar role in shoots of the cadmium hyperaccumulator Sedum alfredii as in non‐resistant plants

Phytochelatin (PC) synthesis is considered necessary for Cd tolerance in non‐resistant plants, but roles for PCs in hyper‐accumulating species are currently unknown. In the present study, the relationship between PC synthesis and Cd accumulation was investigated in the Cd hyperaccumulator Sedum alfredii Hance. PCs were most abundant in leaves followed by stems, but hardly detected by the reversed‐phase high‐performance liquid chromatography (HPLC) in roots. Both PC synthesis and Cd accumulation were time‐dependent and a linear correlation between the two was established with about 1:15 PCs : Cd stoichiometry in leaves. PCs were found in the elution fractions, which were responsible for Cd peaks in the anion exchange chromatograph assay. About 5% of the total Cd was detected in these elution fractions as PCs were found. Most Cd was observed in the cell wall and intercellular space of leaf vascular cells. These results suggest that PCs do not detoxify Cd in roots of S. alfredii. However, like in non‐resistant plants, PCs might act as the major intracellular Cd detoxification mechanism in shoots of S. alfredii.     

Effect of simultaneous establishment of Sedum alfredii and Zea mays on heavy metal accumulation in plants

Land application of biosolids to improve agricultural productivity is a cost-effective approach for resource recovery. Unfortunately, municipal biosolids often contain high concentrations of heavy metals, including zinc and copper. In this study, a co-cropping technique was investigated using a known zinc hyperaccumulator, Sedum alfredii with a grain crop, Zea mays. After a 3-mo growth trial, the results indicate that when Z. mays is co-cropped with S. alfredii, heavy metals accumulated in the grains were significantly reduced when compared to monoculture cropping. Co-cropping improved the growth of both plant species. In addition, the biosolids maintained stable pH, N-P-K concentrations, germination potential, and water content after the plant treatment, regardless of the plant species used in the trial. In conclusion, co-cropping with hyperaccumulators may be an effective approach to reducing the risk of contaminant uptake in edible crops.     

几种有机添加剂对遏蓝菜和东南景天吸收提取Zn的效应

通过盆栽试验,比较研究乙二胺四乙酸二钠盐(EDTA)、味精废液、柠檬酸、乙酸、草酸和混合试剂(柠檬酸∶味精废液∶EDTA∶KC l=10∶1∶2∶3)对Zn超累积植物遏蓝菜(T h lasp i caeru lescens)和东南景天(S edum a lf red ii)吸收提取Zn的影响。结果表明:各种添加剂均提高土壤中的水提取态和NH4NO3提取态Zn的含量,其顺序为EDTA混合试剂>味精废液>有机酸。除乙酸和味精废液外,其余添加剂都显著促进遏蓝菜的生长,以混合试剂的增产效果最好;但只有EDTA和混合试剂在浓度为10mm o l/kg土时提高了东南景天的生物量。混合试剂在浓度为6~10 mm o l/kg土时促进遏蓝菜对Zn的吸收和向地上部转移;EDTA和浓度为10mm o l/kg的混合试剂能显著促进东南景天对Zn的吸收和向地上部的转移。因此东南景天配合环境风险较小、用量为10mm o l/kg土的混合试剂较适合我国南方的Zn污染土壤。     

Root Morphology and Zn^2＋ Uptake Kinetics of the Zn Hyperaccumulator of Sedum alfredii Hance

Root morphology and Zn^2＋ uptake kinetics of the hyperaccumulating ecotype （HE） and nonhyperaccumulating ecotype （NHE） of Sedum alfredii Hance were investigated using hydroponic methods and the radiotracer flux technique. The results indicate that root length, root surface area, and root volume of NHE decreased significantly with increasing Zn^2＋ concentration in growth media, whereas the root growth of HE was not adversely affected, and was even promoted, by 500μmol/L Zn^2＋. The concentrations of Zn^2＋ in both ecotypes of S. alfredii were positively correlated with root length, root surface area and root volumes, but no such correlation was found for root diameter. The uptake kinetics for ^65Zn^2＋ in roots of both ecotypes of S. alfredii were characterized by a rapid linear phase during the first 6 h and a slower linear phase during the subsequent period of investigation. The concentration-dependent uptake kinetics of the two ecotypes of S. alfredii could be characterized by the Michaelis-Menten equation, with the Vmax for ^65Zn^2＋ influx being threefold greater in HE compared with NHE, indicating that enhanced absorption into the root was one of the mechanisms involved in Zn hyperaccumulation. A significantly larger Vmax value suggested that there was a higher density of Zn transporters per unit membrane area in HE roots.     

Root Morphology and Zn2+ Uptake Kinetics of the Zn Hyperaccumulator of Sedum alfredii Hance

Root morphology and Zn2 uptake kinetics of the hyperaccumulating ecotype (HE) and nonhyperaccumulating ecotype (NHE) of Sedum alfredii Hance were investigated using hydroponic methods and the radiotracer flux technique. The results indicate that root length, root surface area, and root volume of NHE decreased significantly with increasing Zn2 concentration in growth media, whereas the root growth of HE was not adversely affected, and was even promoted, by 500 μmol/L Zn2 . The concentrations of Zn2 in both ecotypes of S. alfredii were positively correlated with root length, root surface area and root volumes, but no such correlation was found for root diameter. The uptake kinetics for 65Zn2 in roots of both ecotypes of S. alfredii were characterized by a rapid linear phase during the first 6 h and a slower linear phase during the subsequent period of investigation. The concentration-dependent uptake kinetics of the two ecotypes of S. alfredii could be characterized by the Michaelis-Menten equation, with the Vmax for 65Zn2 influx being threefold greater in HE compared with NHE, indicating that enhanced absorption into the root was one of the mechanisms involved in Zn hyperaccumulation. A significantly larger Vmax value suggested that there was a higher density of Zn transporters per unit membrane area in HE roots.     

镉在东南景天中的亚细胞分配

采用差速离心技术,比较研究了Cd在矿山生态型东南景天(Sedum alfredii Hance)根、茎、叶中的亚细胞分布.结果表明:矿山生态型东南景天对Cd具有很好的忍受耐和累积能力,非矿山生态型东南景天则不具有这种能力.Cd在矿山生态型东南景天根、茎、叶各部分的亚细胞分配满足F1(细胞壁部分)>F3(可溶部分)>F2(细胞器及膜)规律,且Cd在细胞壁部分的分配占绝对优势;同时矿山生态型东南景天地上部有很好的Cd累积能力.与众多超累积植物相似的Cd亚细胞分配规律和地上部的良好的Cd累积能力.对此植物的Cd亚细胞分布完全不同于非矿山生态型东南景天的情况作了比较分析,结果显示矿山生态型东南景天很可能是一种新的镉超累积种质资源.     

东南景天对锌、镉复合污染的反应及其对锌、镉的吸收和积累特性

Sedum alfredii Hance has been identified as a new Zn-hyperaccumulator native to China. In this study, responses and metal accumulation of S. alfredii were examined under Zn/Cd complex polluted conditions. The results showed that optimal growth of S. alfredii in terms of the maximum dry matter yield was observed at Zn/Cd complex level of 500/100 祄ol/L. Plant cadmium (Cd) or zinc (Zn) concentrations increased with increasing Cd or Zn supply. During the 20 d treatment, the highest Cd concentration in the leaves reached 12.1 g/kg at Zn /Cd level of 50/400 祄ol/L and that of Zn in the stems was 23.2 g/kg at Zn/Cd level of 1 000/50 祄ol/L. The distribution of Cd in different plant parts decreased in the order: leaf ＞ stem≥ root, whereas that of Zn was: stem ＞ leaf ≥ root. The accumulation of Cd and Zn in the shoots and roots of S. afredii increased with the increasing of Zn/Cd supply levels, peaked at Zn/Cd levels of 250/400 and 500/100 祄ol/L, respectively. The highest Cd and Zn uptake by the shoots was approximately 5 and 11 mg/plant, and was over 20 and 10 times higher than those in the roots, respectively. Zn supply at levels ≤ 500 祄ol/L increased plant Cd concentrations, whereas high Zn supply decreased root Cd but did not affect leaf Cd concentrations in S. alfredii. Low Cd supply increased Zn concentration in the leaves, but Cd supply higher than 50 祄ol/L considerably reduced root Zn concentrations, especially at low Zn level. These results indicate that S. alfredii can tolerate high Zn/Cd complex levels and has an extraordinary ability to hyperaccumulate not only Zn but also Cd. It could provide a new valuable plant material for understanding the mechanisms responsible for co-hyperaccumulation of Zn and Cd as well as for phytoremediation of the Cd/Zn complex polluted soils.     

镉在东南景天中的亚细胞分配

采用差速离心技术,比较研究了Cd在矿山生态型东南景天(Sedum alfredii Hance)根、茎、叶中的亚细胞分布。结果表明:矿山生态型东南景天对Cd具有很好的忍受耐和累积能力,非矿山生态型东南景天则不具有这种能力。Cd在矿山生态型东南景天根、茎、叶各部分的亚细胞分配满足F1(细胞壁部分)>F3(可溶部分)>F2(细胞器及膜)规律,且Cd在细胞壁部分的分配占绝对优势;同时矿山生态型东南景天地上部有很好的Cd累积能力。与众多超累积植物相似的Cd亚细胞分配规律和地上部的良好的Cd累积能力。对此植物的Cd亚细胞分布完全不同于非矿山生态型东南景天的情况作了比较分析,结果显示矿山生态型东南景天很可能是一种新的镉超累积种质资源。     

Detection of phytochelatins in the hyperaccumulator Sedum alfredii exposed to cadmium and lead

Phytochelatins (PCs) are known to play an essential role in the heavy metal detoxification of some higher plants and fungi by chelating heavy metals. However, three recent papers reported that no PCs could be detected in the hyperaccumulator Sedum alfredii Hance upon cadmium, lead or zinc treatment, respectively. In this paper, PC synthesis was assayed again in the mine population of S. alfredii with the help of reversed phase high-performance liquid chromatography (HPLC), HPLC-mass spectrometry, and HPLC-tandem mass spectrometry. Our data showed that PC formation could be induced in the leaf, stem and root tissues of S. alfredii upon exposure to 400 microM cadmium, and only in the stem and root when exposed to 700 microM lead. However, no PCs were found in any part of S. alfredii when it was subjected to exposure to 1600 microM zinc.     

Long-term field phytoextraction of zinc/cadmium contaminated soil by Sedum plumbizincicola under different agronomic strategies

In two long-term field experiments the zinc (Zn)/cadmium (Cd) hyperaccumulator Sedum plumbizincicola (S. plumbizincicola) was examined to optimize the phytoextraction of metal contaminated soil by two agronomic strategies of intercropping with maize (Zea mays) and plant densities. Soil total Zn and Cd concentrations decreased markedly after long-term phytoextraction. But shoot biomass and Cd and Zn concentrations showed no significant difference with increasing remediation time. In the intercropping experiment the phytoremediation efficiency in the treatment “S. plumbizincicola intercropped with maize” was higher than in S. plumbizincicola monocropping, and Cd concentrations of corn were below the maximum national limit. In the plant density experiment the phytoremediation efficiency increased with increasing plant density and 440,000 plants ha^?1 gave the maximum rate. These results indicated that S. plumbizincicola at an appropriate planting density and intercropped with maize can achieve high remediation efficiency to contaminated soil without affecting the cereal crop productivity. This cropping system combines adequate agricultural production with soil heavy metal phytoextraction.     

Dynamics of zinc uptake and accumulation in the hyperaccumulating and non-hyperaccumulating ecotypes of Sedum alfredii Hance

Sedum alfredii Hance has been identified as a Zn-hyperaccumulating plant species native to China. The characteristics of Zn uptake and accumulation in the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii were investigated under nutrient solution and soil culture conditions. The growth of HE was normal up to 1000 μM Zn in nutrient solution, and 1600 mg Zn kg⁻¹ soil in a Zn-amended soil. Growth of the NHE was inhibited at Zn levels ≥250 μM in nutrient solution. Zinc concentrations in the leaves and stems increased with increasing Zn supply levels, peaking at 500 and 250 μM Zn in nutrient solution for the HE and the NHE, respectively, and then gradually decreased or leveled off with further increase in solution Zn. Minimal increases in root Zn were noted at Zn levels up to 50 μM; root Zn sharply increased at higher Zn supply. The maximum Zn concentration in the shoots of the HE reached 20,000 and 29,000 mg kg⁻¹ in the nutrient solution and soil experiments, respectively, approximately 20 times greater than those of the NHE. Root Zn concentrations were higher in the NHE than in the HE when plants were grown at Zn levels ≥50 μM. The time-course of Zn uptake and accumulation exhibited a hyperbolic saturation curve: a rapid linear increase during the first 6 days in the long-term and 60 min in the short-term studies; followed by a slower increase or leveling off with time. More than 80% of Zn accumulated in the shoots of the HE at half time (day 16) of the long-term uptake in 500 μM Zn, and also at half time (120 min) of the short-term uptake in 10 μM ⁶⁵Zn²⁺. These results indicate that Zn uptake and accumulation in the shoots of S. alfredii exhibited a down-regulation by internal Zn accumulated in roots or leaves under both nutrient solution and soil conditions. An altered Zn transport system and increased metal sequestration capacity in the shoot tissues, especially in the stems, may be the factors that allow increased Zn accumulation in the hyperaccumulating ecotype of S. alfredii. Section Editor: F. J. Zhao