Delimiting soil chemistry thresholds for nickel hyperaccumulator plants in Sabah (Malaysia)

Nickel hyperaccumulator plants have been the focus of considerable research because of their unique ecophysiological characteristics that can be exploited in phytomining technology. Comparatively little research has focussed on the soil chemistry of tropical nickel hyperaccumulator plants to date. This study aimed to elucidate whether the soil chemistry associated with nickel hyperaccumulator plants has distinctive characteristics that could be indicative of specific edaphic requirements. The soil chemistry associated with 18 different nickel hyperaccumulator plant species occurring in Sabah (Malaysia) was compared with local ultramafic soils where nickel hyperaccumulator plants were absent. The results showed that nickel hyperaccumulators in the study area were restricted to circum-neutral soils with relatively high phytoavailable calcium, magnesium and nickel concentrations. There appeared to be a ‘threshold response’ for the presence of nickel hyperaccumulator plants at >20 μg g^?1 carboxylic-extractable nickel or >630 μg g^?1 total nickel, and >pH 6.3 thereby delimiting their edaphic range. Two (not mutually exclusive) hypotheses were proposed to explain nickel hyperaccumulation on these soils: (1) hyperaccumulators excrete large amounts of root exudates thereby increasing nickel phytoavailability through intense rhizosphere mineral weathering; and (2) hyperaccumulators have extremely high nickel uptake efficiency thereby severely depleting nickel and stimulating re-supply of Ni from diffusion from labile Ni pools. It was concluded that since there was an association with soils with highly labile nickel pools, the available evidence primarily supports hypothesis (2).     

Spread of metals through an invertebrate food chain as influenced by a plant that hyperaccumulates nickel

Summary. Hyperaccumulation of metals in the shoot system of plants is uncommon, yet taxonomically and geographically widespread. It may have a variety of functions, including defense against herbivores. This study investigated the effects of hyperaccumulation on metal concentrations across trophic levels. We collected plant material, soil, and invertebrates from Portuguese serpentine outcrops whose vegetation is dominated by the nickel hyperaccumulator Alyssum pintodasilvae. Samples were analyzed for nickel, chromium, and cobalt. Grasshoppers, spiders, and other invertebrates collected from sites where A. pintodasilvae was common had significantly elevated concentrations of nickel, compared to nearby sites where this hyperaccumulator was not found. Chromium and cobalt, occurring in high concentrations in the serpentine soil but not accumulated by A. pintodasilvae, were not elevated in the invertebrates. Therefore, it appears likely that a flux of nickel to herbivore and carnivore trophic levels is specifically facilitated by the presence of plants that hyperaccumulate this metal. The results may be relevant to the development of phytoremediation and phytomining technologies, which use plants to extract metals from the soil. Reveived 22 August 2002; accepted 2 April 2003. R1D=" Correspondence to: A. J. Pollard, e-mail:joe.pollard@furman.edu     

植物修复土壤重金属污染中外源物质的影响机制和应用研究进展

重金属进入土壤后难以被降解,并通过食物链在生物体内富集,长此以往会导致中毒、癌症、畸形、突变,严重影响了人类生产活动及地球生态系统的稳定。植物修复技术是一种经济有效的重金属污染修复技术,其依靠超富集植物强大的自身抗性机制,从土壤中提取或稳定重金属,达到污染治理的目的。然而修复土壤重金属污染的超富集植物通常生长缓慢、生物量低,其抗性机制也会受到植物本身对重金属胁迫的阈值限制,当胁迫超过这个阈值,植物修复的效率就会大大降低甚至失去修复功能。文章在解析植物重金属相互作用机制的基础上,综述了添加外源物质对重金属毒害植物的缓解效应以及其在强化植物修复土壤重金属污染中的应用研究进展;介绍了应用外源物质调控植物吸收转运重金属的3种途径,分别为提高土壤重金属生物利用度、促进植物生长以及增强植物耐性。提出了应用外源物质作为强化植物修复措施的潜力及今后的研究方向,其未来的研究应着重于以下方面:明确外源物质的应用浓度、时期、方式与植物吸收转运重金属之间的关系;从植物内源激素及信号分子间的互作、抗逆基因表达、内生及根际微生物等不同层面上揭示外源物质对植物积累重金属的调控机理;开展外源物质与其他植物修复强化技术的联合应用研究。这些研究可为土壤重金属污染的植物修复技术及其强化措施研究提供科学依据,同时也对植物修复工程技术的发展实践具有一定的指导意义。     

Carbon nanotubes and Cu–Zn nanoparticles synthesis using hyperaccumulator plants

This article reports a novel way to synthesize carbon nanotubes and Cu/ZnO nanoparticles using metal hyperaccumulator plants. Metal hyperaccumulator plants are traditionally used for phytoremediation to clean soil polluted by toxic metals. However, the transfer of toxic metals in plant shoots and leaves is an environmental issue because animals and other living organisms feeding on plants will transfer the metals to the ecosystem. Therefore, we suggest that hyperaccumulator plants could be used to synthesize nanoparticles. Here, Brassica juncea L., a Cu-hyperaccumulator plant, was collected around a copper mine and used as a raw chemical to produce carbon nanotubes and Cu/ZnO nanoparticles. The chlorophyll in shoots of B. juncea plants was ethanol extracted to yield chlorophyllin. Cu and Zn were extracted by HNO₃ to form Cu/Zn(NO₃)₂. The chlorophyllin reacted with Cu/Zn(NO₃)₂ to form Cu/Zn chlorophyllin. Cu/ZnO nanoparticles were synthesized by direct precipitation of Cu/Zn chlorophyllin with NaOH and ethanol. The vascular bundles in B. juncea plants, which have been purified and carbonized by HNO₃, were rapidly heated to about 400°C and then they were cooled to room temperature to obtain carbon nanotubes. Results indicate that the outer diameter of carbon nanotubes was around 80 nm. Cu/ZnO nanoparticles have a Cu_0.05Zn_0.95O composition, and had a diameter of about 97 nm. Our study not only inspires the search for a new strategy on the synthesis of nanostructure from renewable natural products, but also breaks through the traditional and limited ideas about the reuse of metals by hyperaccumulator plants.     

利用美洲商陆修复锰尾渣污染土壤对后茬植物的影响

采用盆栽法研究用锰超富集植物美洲商陆(Phytolacca americana)修复锰尾渣污染土壤对后茬植物大豆(Glycine max)和绿豆(Phaseolus radiatus)的影响.经美洲商陆修复锰尾渣污染土壤后,后茬植物大豆和绿豆的镉、铅、锌和锰含量降低,污染土壤的毒性减弱,有利于这2种植物生长.经美洲商陆修复2～3 a,可显著减弱污染土壤对大豆的毒性.由此可见,在经美洲商陆修复的污染土壤上栽培大豆,可以增加含氮量,促进其他植物生长,从而维持锰尾渣污染区植被持续发展.     

宝山堇菜多金属吸收特征和耐性策略

宝山堇菜Viola baoshanensis Shu,Liu et Lan是一种Cd超富集植物,但它对不同重金属的吸收和转运能力有待进一步研究。从湖南桂阳宝山多金属矿区中筛选4个宝山堇菜优势分布的小生境,分析这些生境中宝山堇菜及其根区土壤的重金属质量分数。化学分析结果显示,宝山堇菜优势分布土壤中Cd、Pb、Zn、Cu、Mn和Fe的平均质量分数（mg/kg）分别为471、15 044、8 273、1 776、4 702和69 054。宝山堇菜地上部Cd、Pb、Zn、Cu、Mn和Fe的平均质量分数（mg/kg）分别为387、1 077、1 037、99、379和1 812,其中Cd、Pb超过超富集植物标准,Zn、Cu的平均质量分数大约是Zn、Cu超富集植物标准的10%,Mn的平均质量分数低于Mn超富集植物标准的5%,Fe的平均质量分数高于1 000 mg/kg。上述结果表明,宝山堇菜可以超富集Cd和Pb,富集Zn、Cu和Fe以及低积累Mn。此外,宝山堇菜对不同重金属差别化吸收模式可能也代表了超富集植物适应重金属复合污染土壤的一种策略。     

Field crops for phytoremediation of metal-contaminated land. A review

The use of higher plants to remediate contaminated land is known as phytoremediation, a term coined 15 years ago. Among green technologies addressed to metal pollution, phytoextraction has received increasing attention starting from the discovery of hyperaccumulator plants, which are able to concentrate high levels of specific metals in the above-ground harvestable biomass. The small shoot and root growth of these plants and the absence of their commercially available seeds have stimulated study on biomass species, including herbaceous field crops. We review here the results of a bibliographical survey from 1995 to 2009 in CAB abstracts on phytoremediation and heavy metals for crop species, citations of which have greatly increased, especially after 2001. Apart from the most frequently cited Brassica juncea (L.) Czern., which is often referred to as an hyperaccumulator of various metals, studies mainly focus on Helianthus annuus L., Zea mays L. and Brassica napus L., the last also having the greatest annual increase in number of citations. Field crops may compensate their low metal concentration by a greater biomass yield, but available data from in situ experiments are currently very few. The use of amendments or chelators is often tested in the field to improve metal recovery, allowing above-normal concentrations to be reached. Values for Zn exceeding 1,000 mg kg⁻¹ are found in Brassica spp., Phaseolus vulgaris L. and Zea mays, and Cu higher than 500 mg kg⁻¹ in Zea mays, Phaseolus vulgaris and Sorghum bicolor (L.) Moench. Lead greater than 1,000 mg kg⁻¹ is measured in Festuca spp. and various Fabaceae. Arsenic has values higher than 200 mg kg⁻¹ in sorghum and soybean, whereas Cd concentrations are generally lower than 50 mg kg⁻¹. Assisted phytoextraction is currently facilitated by the availability of low-toxic and highly degradable chelators, such as EDDS and nitrilotriacetate. Currently, several experimental attempts are being made to improve plant growth and metal uptake, and results are being achieved from the application of organic acids, auxins, humic acids and mycorrhization. The phytoremediation efficiency of field crops is rarely high, but their greater growth potential compared with hyperaccumulators should be considered positively, in that they can establish a dense green canopy in polluted soil, improving the landscape and reducing the mobility of pollutants through water, wind erosion and water percolation.     

A test of elemental defence against slugs by Ni in hyperaccumulator and non-hyperaccumulator Streptanthus species

Summary. Tissues of most plant species contain < 10 μg Ni g⁻¹ but Ni hyperaccumulators contain more than 1000 μg Ni g⁻¹ . Hyperaccumulated Ni can defend plants from some herbivores but the defensive role of lesser Ni concentrations is little explored. We raised five species of Streptanthus (Brassicaceae) native to ultramafic soils, one of which (S. polygaloides) is a Ni hyperaccumulator whereas the others are simply Ni-tolerant, on Ni-amended and unamended green-house soils to create plants differing in Ni concentrations. On high-Ni soil, leaves of the hyperaccumulator contained 3800 μg Ni g⁻¹ whereas leaves of non-hyperaccumulator species contained 41–64 μg Ni g⁻¹. Plants of all species grown on low-Ni soils had < 14 μg Ni g⁻¹. Slugs (Limax maximus) were fed plant material in no-choice tests over a 50-day period and survival and mass changes were recorded. All slugs fed high-Ni leaves of the hyperaccumulator species died within 21 d. Slugs fed high-Ni leaves of the other species did not differ significantly in survival or mass change from those fed low-Ni leaves. In choice tests, slugs (Lehmannia valentiana) offered both high- and low-Ni S. polygaloides leaves did little damage to high-Ni leaves. We conclude that hyperacumulated Ni can defend S. polygaloides from slug herbivory via both toxicity and deterrence, but these defensive effects do not extend to Streptanthus species containing < 70 μg Ni g⁻¹.     

Phytoremediation potential of indigenous plants from Thai Nguyen province, Vietnam

This study was focused on determining Arsenic (As), Lead (Pb), Cadmium (Cd) and Zinc (Zn) in 33 indigenous plants and 12 soil in-situ plant samples in Thai Nguyen Province, Vietnam. The results showed that the soils of surveyed mining areas contained 181.2- 6754.3 mg kg(-1) As, 235.5-4337.2 mg kg(-1) Pb, 0.8- 419 mg kg(-1) Cd and 361.8-17565.1 mg kg(-1) Zn depending on the characteristics of each mining site. These values are much higher than those typical for normal soil. The heavy metal uptake into shoots and roots of 33 indigenous plant species was also determined. Two species of the plants investigated, Pteris vittata L. and Pityrogramma calomelanos L. were As hyperaccumulators, containing more than 0.1% heavy metals in their shoots. Eleusine indica L., Cynodon dactylon L., Cyperus rotundus L. and Equisetum ramosissimum (Vauch) accumulate very high Pb (0.15-0.65%) and Zn (0.22-1.56%) concentration in their roots. Additional experiments to clarify the potential of six these plants as good candidates for phytoremediation of heavy metal pollution soil are being carried out in our laboratory.     

Heavy metals,occurrence and toxicity for plants: a review

Metal contamination issues are becoming increasingly common in India and elsewhere, with many documented cases of metal toxicity in mining industries, foundries, smelters, coal-burning power plants and agriculture. Heavy metals, such as cadmium, copper, lead, chromium and mercury are major environmental pollutants, particularly in areas with high anthropogenic pressure. Heavy metal accumulation in soils is of concern in agricultural production due to the adverse effects on food safety and marketability, crop growth due to phytotoxicity, and environmental health of soil organisms. The influence of plants and their metabolic activities affects the geological and biological redistribution of heavy metals through pollution of the air, water and soil. This article details the range of heavy metals, their occurrence and toxicity for plants. Metal toxicity has high impact and relevance to plants and consequently it affects the ecosystem, where the plants form an integral component. Plants growing in metal-polluted sites exhibit altered metabolism, growth reduction, lower biomass production and metal accumulation. Various physiological and biochemical processes in plants are affected by metals. The contemporary investigations into toxicity and tolerance in metal-stressed plants are prompted by the growing metal pollution in the environment. A few metals, including copper, manganese, cobalt, zinc and chromium are, however, essential to plant metabolism in trace amounts. It is only when metals are present in bioavailable forms and at excessive levels, they have the potential to become toxic to plants. This review focuses mainly on zinc, cadmium, copper, mercury, chromium, lead, arsenic, cobalt, nickel, manganese and iron.     

Soil nitrogen availability and herbivore attack influence the chemical defenses of an invasive plant (Linaria dalmatica; Plantaginaceae)

Chemical defenses are thought to contribute to the invasion success and impacts of many introduced plants; however, for most of these species, little is known about these compounds and how they vary in natural environments. Plant allelochemical concentrations may be affected by a variety of abiotic and biotic factors, including soil nutrients and herbivores. Moreover, such quantitative variation is likely to play an important role in species interactions involving these invasive plants. The purpose of this study was to examine patterns of variation in iridoid glycoside concentrations of the invasive plant Linaria dalmatica (Plantaginaceae). We conducted a greenhouse experiment to investigate the effect of soil nitrogen availability on iridoid glycoside concentrations. Results from this experiment showed that plant iridoid glycoside concentrations decreased with increased nitrogen availability. Additionally, plants were collected from multiple field sites in order to characterize the influence of population, soil nitrogen availability, and herbivore attack on iridoid glycoside variation. Results from field studies indicated that plants demonstrated considerable seasonal variation, as well as variation within and among populations, with iridoid glycoside concentrations ranging from approximately 1 to 15% dry weight. The relationship between soil nitrogen and plant iridoid glycosides varied among populations, with a strong negative correlation in one population, a marginally significant negative relationship in a second population, and no relationship in the remaining two populations. Additionally, we found a negative relationship between iridoid glycoside concentrations and plant injury by an introduced biocontrol agent, the stem-mining weevil Mecinus janthinus (Cucurlionidae). These results show that plant allelochemical concentrations can vary widely in natural environments and suggest that levels of plant defense may be reduced by increased soil nitrogen availability and herbivore attack in this invasive plant species.     

植物吸收修复对土壤镍及其主要化学性质的影响

采用室内盆栽试验方法,研究了外源镍污染土壤的植物吸收修复对土壤镍形态和土壤主要化学性质的影响。试验用水稻土添加NiSO4·6H2O(100～1600mgkg-1)经过12周的驯化培养后,种植了镍超累积植物Alyssu mmurale,110 d后收获植物并进行了试验土壤镍的形态和主要化学性质的分析,采用再分配系数和结合强度系数对植物修复效果进行了定量分析。结果表明,根区土壤中DTPA提取态镍的数量明显减少,根区土壤DTPA-Ni与非根区土壤DTPA-Ni之比的范围在0.33～0.61之间。每盆植物提取镍量为6.61～31.18mg,植物提取量随着添加镍量增加而增加,地上部分最大镍含量达到12454.1mgkg-1。根区的再分配系数在2.17～4.19之间,而非根区的再分配系数在6.87～15.91之间,再分配系数随着镍添加量的增加而增大;根区的结合强度系数为0.84～0.39,而非根区的则为0.88～0.26,随着土壤中镍添加量的增加,结合强度系数逐渐减小。植物吸收修复后,根区土壤镍的再分配系数降低、结合强度系数增大,表明土壤镍各形态之间的稳定性增加,因此植物修复可以加快外源镍在土壤中的稳定。试验结果也表明,根区土壤中pH随着镍添加量的增加呈下降趋势、但较非根区土壤的高;根区土壤有机碳亦较非根区的高。     

土壤水溶解态有机物质与重金属的络合作用

水溶解态有机物质与重金属离子的络合反应对土壤重金属化学行为的影响十分显著。文章综述了土壤水溶解态有机物质与重金属离子之间相互作用的研究进展,讨论了水溶解态有机物质与络合反应有关的性质,以及水溶态有机物质与重金属的络合作用的问题。     

Additive effects of aboveground polyphagous herbivores and soil feedback in native and range-expanding exotic plants

Plant biomass and plant abundance can be controlled by aboveground and belowground natural enemies. However, little is known about how the aboveground and belowground enemy effects may add up. We exposed 15 plant species to aboveground polyphagous insect herbivores and feedback effects from the soil community alone, as well as in combination. We envisaged three possibilities: additive, synergistic, or antagonistic effects of the aboveground and belowground enemies on plant biomass. In our analysis, we included native and phylogenetically related range-expanding exotic plant species, because exotic plants on average are less sensitive to aboveground herbivores and soil feedback than related natives. Thus, we examined if lower sensitivity of exotic plant species to enemies also alters aboveground-belowground interactions. In a greenhouse experiment, we exposed six exotic and nine native plant species to feedback from their own soil communities, aboveground herbivory by polyphagous insects, or a combination of soil feedback and aboveground insects and compared shoot and root biomass to control plants without aboveground and belowground enemies. We observed that for both native and range-expanding exotic plant species effects of insect herbivory aboveground and soil feedback added up linearly, instead of enforcing or counteracting each other. However, there was no correlation between the strength of aboveground herbivory and soil feedback. We conclude that effects of polyphagous aboveground herbivorous insects and soil feedback add up both in the case of native and related range-expanding exotic plant species, but that aboveground herbivory effects may not necessarily predict the strengths of soil feedback effects.     

Assessing the Potential to Restore Historic Grazing Ecosystems with Tortoise Ecological Replacements

The extinction of large herbivores, often keystone species, can dramatically modify plant communities and impose key biotic thresholds that may prevent an ecosystem returning to its previous state and threaten native biodiversity. A potentially innovative, yet controversial, landscape‐based long‐term restoration approach is to replace missing plant‐herbivore interactions with non‐native herbivores. Aldabran giant (Aldabrachelys gigantea) and Madagascan radiated (Astrochelys radiata) tortoises, taxonomically and functionally similar to the extinct Mauritian giant tortoises (Cylindraspis spp.), were introduced to Round Island, Mauritius, in 2007 to control the non‐native plants that were threatening persistence of native species. We monitored the response of the plant community to tortoise grazing for 11 months in enclosures before the tortoises were released and, compared the cost of using tortoises as weeders with the cost of using manual labor. At the end of this period, plant biomass; vegetation height and cover; and adult, seedling, flower, and seed abundance were 3–136 times greater in adjacent control plots than in the tortoise enclosures. After their release, the free‐roaming tortoises grazed on most non‐native plants and significantly reduced vegetation cover, height, and seed production, reflecting findings from the enclosure study. The tortoises generally did not eat native species, although they consumed those native species that increased in abundance following the eradication of mammalian herbivores. Our results suggest that introduced non‐native tortoises are a more cost‐effective approach to control non‐native vegetation than manual weeding. Numerous long‐term outcomes (e.g., change in species composition and soil seed bank) are possible following tortoise releases. Monitoring and adaptive management are needed to ensure that the replacement herbivores promote the recovery of native plants. Estudiando el Potencial para Restaurar Ecosistemas Históricos de Forrajeo con Reemplazos Ecológicos de Tortugas Terrestres     

Aphids are unaffected by the elemental defence of the nickel hyperaccumulator Streptanthus polygaloides (Brassicaceae)

Summary. Nickel hyperaccumulation, resulting in plant Ni contents of >1000 mg kg^у dry mass, has been shown to defend plants against folivorous herbivores. We determined whether this elemental defence tactic protected hyperaccumulating plants from attack by a phloem-feeding herbivore. We used the pea aphid, Acyrthosiphon pisum, and the Ni-hyperaccumulating plant Streptanthus polygaloides. Aphids were allowed to colonize mixed arrays of S. polygaloides in which plants either were hyperaccumulating Ni, not hyperaccumulating Ni and treated with a systemic insecticide, or not hyperaccumulating Ni. Aphid numbers g^у dry mass of plant biomass were lowest for the insecticide treatment, intermediate for low-Ni plants, and highest for plants hyperaccumulating Ni. Artificial liquid aphid diet, amended with varying levels of Ni, resulted in decreased aphid survival at 2500 mg kg^у Ni dry mass (or 5.03 mM Ni). We concluded that Ni levels in the phloem of hyperaccumulating plants of S. polygaloides were < 5.03 mM and, as a result, were not effective in defending plants against aphid attack.     

吊兰和蝴蝶梅对污泥中重金属的去除效果

采用盆栽土培方法,将剩余污泥与供试土壤按质量比为0∶3,1∶2,2∶1和3∶0配比,吊兰和蝴蝶梅栽培幼苗,定期测定植物的株高、根长、干重、鲜重等生物量和叶绿素与根活力变化,以及植物体内Cu、Zn、Cd、Pb和Cr等的重金属含量变化;测定种植前后植物根系旁污泥中的重金属含量和重金属的EDTA提取含量等结果表明,吊兰对多种重金属具有很好的耐性,受重金属影响不大.吊兰对Cr和Zn的富集效果较好,对Cr的富集系数在某个特定的生长期是大于1,且它对Zn的富集效果较稳定,不易受重金属浓度的影响.由于吊兰具有生物量大、根系发达、生物量增长迅速等优点,其有利于被重金属污染的土壤改良.而蝴蝶梅因为根系不发达和生物量较小等原因,对重金属的耐性不强,生长中易受重金属影响,因此不宜用于修复污染土壤的植物.图9,表5,参7.     

Uptake of seven metals by two macrophytes species: potential for phytoaccumulation and phytoremediation

Aquatic macrophytes can be used in the studies of quality of water ecosystems and in monitoring of metals and other pollutants. The aim of this study was to assess concentration levels, accumulation and distribution of seven metals in selected plant parts of Typha angustifolia L. and Iris pseudacorus L., in comparison with sediment and water samples of a reservoir. Metal content in the samples was determined by optical emission spectrometry (ICP-OES iCAP 6500). The concentrations of all examined metals were higher in the sediment than in the water samples. In plants, metal concentrations depended on plant species and organs. The roots/rhizomes were primary organs for metal concentration and accumulation. T. angustifolia L. accumulated Mn and Cu, and I. pseudacorus L. accumulated Cd and Cu in the fruits. T. angustifolia L. hyperaccumulated As. The values of enrichment coefficients and translocation factors were: 0 to 3.31 and 0 to 2.39, respectively. The plant species investigated absorb, translocate and accumulate metals in their organs differently, which provides advantages in combining them for remediation of wasted aquatic ecosystems.     

Intraspecific variation of sesquiterpene lactones associated to a latitudinal gradient in <Emphasis Type="Italic">Smallanthus macroscyphus</Emphasis> (Heliantheae: Asteraceae)

According to theory, variation in plant secondary metabolism against herbivores is driven by variation in biotic and abiotic conditions interacting with plants genotype to determine the expression of resistance traits. Particularly, it has been long postulated that plants growing along latitudinal gradients experience changes in biotic and abiotic interactions, specifically leading to a decrease of plant toxicity towards the poles. We tested this hypothesis using the asteraceous species Smallanthus macroscyphus. Smallanthus species are known to contain sesquiterpene lactones (STLs), bitter compounds with a broad spectrum of biological activities, including deterrence to herbivores. S. macroscyphus showed a decrease in chemical diversity of STLs when investigating populations growing from the tropical regions to less tropical ones. Populations from lower latitudes were found to be more chemically diverse with enhydrin, uvedalin and fluctuanin as main components, while populations southward were chemically fairly uniform, with polymatin A as the main and largely dominant STL. The STL chemistry of S. macroscyphus is in agreement with the hypothesis that plants of tropical forests have a greater diversity of secondary metabolites when compared to their temperate counterparts.     

铅锌冶炼厂土壤污染及重金属富集植物的研究

对株洲市铅锌冶炼厂生产区进行了植被和土壤调查。结果表明，该厂土壤污染以镉铅锌(Cd、Pb、Zn)最为严重，尤其是重金属镉在土壤中含量超过背景值高达208倍，分析原因主要是由于大气尘降和雨水淋洗等使得污染加重。实验采集并分析测定了9种植物中重金属富集量，首次报道了土荆芥是一种铅超富集植物，其体内Pb质量分数高达3888mg／kg。另一种植物商陆能大量富集镉，具有地下部向地上部转运能力强、生物量大、富集总量高的特点，有很大研究价值和应用潜力。另外，荨麻对Zn有较强富集能力，这3种植物可分别用于铅、镉和锌等3种重金属污染土壤的植物修复。