Dualities in plant tolerance to pollutants and their uptake and translocation to the upper plant parts

There is a duality in plant tolerance to pollutants and its response to the pollutants’ stress.On the one hand some plants, (hyper)tolerant to heavy metals, are able to hyperaccumulate these metals in shoots, which could be beneficial for phytoremediation purposes to clean-up soil and water. On the other hand tolerant food crops, exposed to heavy metals in their growth medium, may be dangerous as carriers of toxic metals in the food chain leading to food toxicity. There is an additional duality in plant tolerance to heavy metals and that is in food crops that are tolerant and/or hyperaccumulators, which could be used on one hand for phytoremediation, under controlled conditions and on the other hand for food fortification with essential metals.Similarly, plants are also exposed to a large number of xenobiotic organic pollutants. Because they generally cannot avoid these compounds, plants take up, translocate, metabolize and detoxify many of them. There is a large variability in tolerance (defence) mechanisms against organic pollutants among plant species. This includes production of reductants but also scavenger molecules like ascorbate and glutathione and expression of the P-450 defence system, and superfamilies of the enzymes glutathione- and glucosyl-transferases. Again, with view to organic pollutants, plant detoxification mechanisms might well protect the plant itself, but produce compounds with some deleterious potential for other organisms.In this review we discuss these dualities on the basis of examples of agricultural and ‘wild’ species exposed to metal contaminants (mainly Cd) and organic pollutants. Differences in uptake and translocation of various pollutants and their consequences will be considered. We will separately outline the effects of the organic and non-organic pollutants on the internal metabolism and the detoxification mechanisms and try to indicate the differences between both types of pollutants. Finally the consequences and solutions of these dualities in plant tolerance to pollutants will be discussed.     

土壤生物与土壤污染研究前沿与展望

随着社会经济发展,人类生产活动对自然环境产生越来越广泛深刻的影响,土壤污染已成为危及生态系统稳定、农产品质量安全和人体健康的突出环境问题之一。重金属、有机污染化合物、病原菌及抗性基因等各类污染物大量进入土壤后,对土壤生物系统造成毒害作用,影响到土壤生态功能;另一方面,土壤生物如细菌、真菌、土壤动物等在一定程度上能够适应土壤污染,深刻影响着污染物在土壤中的迁移转化过程,在土壤污染修复中具有潜在重要作用。从土壤污染的生态毒理效应、土壤生物对土壤污染的响应与适应机制、污染土壤修复原理与技术等三方面综述了土壤生物与土壤污染相关研究前沿,展望了重点研究方向。     

根系分泌物及其在植物修复中的作用

 近年来环境污染日益严重,污染物在土壤植物中的行为引起了人们的高度关注。利用植物去除土壤水体等介质中污染物的植物修复是近10年来兴起的一项安全、廉价的技术,已成为污染生态学和环境生态学的研究热点,它通过植物吸收、根滤、稳定、挥发等方式清除环境中的重金属和有机污染物。国内外有关植物修复的研究报道和概述很多, 但对植物根系分泌物在植物修复中所起的作用及其机理少有述评。 本文从根系分泌物对土壤重金属和土壤有机污染物的去除作用出发,对根系分泌物的种类、数量及其在去除环境污染物中的作用机理和功能地位进行了总结,并借助研究事例对影响植物根系分泌的内外因子,如植物种类、营养胁迫、重金属胁迫、根际环境的理化性质、土壤微生物及其它环境因子进行了讨论。概言之,根系分泌物在修复污染土壤中的重金属途径是多种多样的,主要是通过调节根际pH值、与重金属形成螯合物、络合反应、沉淀、提高土壤微生物数量和活性来改变重金属在根际中的存在形态以及提高重金属的生物有效性,从而减轻它对环境的危害。在清除有机污染物时,根系分泌物中的酶可以对有机污染物进行直接降解,根系分泌物影响下的微生物也可以对有机污染物进行间接降解,且被认为是主要的降解途径。根系分泌物在植物修复过程中确实起着某些重要作用,今后应将这方面的研究重点放在某些特异性根系分泌物植物,尤其是某些重金属超富集植物资源的寻找、筛选上,通过室内实验和野外研究确定其根系分泌物对清除重金属和有机污染物的效率,证实超富集植物根系分泌物的特异性与污染物超富集的内在联系,找到污染土壤生态恢复和治理的有效方法并加以推广应用,如针对性地在被污染地大面积种植此类具特异性根分泌物植物,并辅以营林措施如修剪等,加快生物修复进程,提高修复效率。植物根系分泌物在植物修复过程中所具有的重要生态意义和可能应用前景,为污染生态学和化学生态学之间的联合研究开拓了全新的领域,今后将取得新的突破和重要进展。     

Assessing the applicability of phytoremediation of soils with mixed organic and heavy metal contaminants

Soil pollution is a major environmental problem and many contaminated sites are tainted with a mixture of organic and heavy metal contaminants. Compared to other remedial strategies, phytoremediation is a low cost, environmentally-friendly, sustainable means of remediating the contamination. This review first provides an overview of phytoremediation studies where the soil is contaminated with just one type of pollutant (heavy metals or organics) and then critically evaluates the applicability of phytotechnologies for the remediation of contaminated sites where the soil is polluted by a mixture of organic and heavy metal contaminants. In most of the earlier research studies, mixed contamination was held to be detrimental to plant growth, yet there were instances where plant growth was more successful in soil with mixed contamination than in the soil with only individual contaminants. New effective phytoremediation strategies can be designed for remediation of co-contaminated sites using: (a) plants species especially adapted to grow in the contaminated site (hyperacumulators, local plants, transgenic plants); (b) endophytic bacteria to enhance the degradation in the rizhosphere; (c) soil amendments to increase the contaminants bioavailability [chelating agents and (bio)surfactants]; (d) soil fertilization to enhance the plant growth and microbial activity in the soil; and (e) coupling phytoremediation with other remediation technologies such as electrokinetic remediation or enhanced biodegradation in the rhizosphere.     

土壤重金属生物毒性研究进展

世界范围内土壤重金属污染不断加重,由污染所带来的问题以及如何治理污染已经受到人们越来越多的关注.土壤重金属将对土壤生物产生影响,而土壤生物在重金属的胁迫下也会产生不同的响应.综述了国内外近年来土壤重金属生物毒性的研究进展,介绍了土壤重金属污染对陆地生态系统中植物、动物和微生物生长的影响;土壤重金属生物毒性的影响因素;土壤重金属生物毒性的研究方法;土壤重金属生物毒性的预测模型,最后提出了问题和展望.     

刈割活动对松嫩草原碱化羊草草地土壤线虫群落的影响

应用类群数、个体密度、多样性指数和功能类群指数等多个群落参数, 研究刈割活动对松嫩草原碱化羊草草地土壤线虫群落特征的影响。本研究共捕获土壤线虫8,335条, 分别隶属于线虫动物门2纲7目23科40属。结果表明, 与围栏封育样地相比, 刈割活动样地中线虫个体密度和类群数显著减少, 群落多样性指数(H′)、均匀度指数(J)和丰富度指数(SR)虽低于围栏封育样地, 但两类处理间差异不显著, 表明刈割活动尽管明显降低土壤线虫群落个体密度和类群数, 但对土壤线虫群落多样性的影响有限; 样地间PPI／MI值差异明显, 表明刈割活动在一定程度上确实改变了土壤线虫功能类群组成, 其中受影响的主要是非植物寄生线虫。     

土壤复合污染的联合修复技术研究进展

复合污染是土壤污染的主要存在形式,其中重金属、有机污染物等是主要的污染源。例如,共存于土壤中铅和镉会发生交互作用,从而增强了镉的迁移能力。此前单一的物理、化学、生物等修复手段对复合污染的修复效果并不明显。联合修复技术的使用可以在一定程度上克服使用单一的修复手段存在的缺点,提高修复效率、降低修复成本。最近有研究表明,综合利用化学氧化和超声波方法可以在很短的时间内将土壤中的甲苯和二甲苯完全氧化为CO和CO2。介绍了综合利用物理、化学、生物等方法对土壤复合污染修复的进展,并对研究中需要注意的问题及未来的发展趋势说明。     

Effects of organic and heavy metal pollution on chironomids within a pristine upland catchment

Several studies, particularly in the Northern Hemisphere, have demonstrated that chironomids are responsive to pollution (e.g., heavy metals, organic). In Australia, there is limited evidence that chironomid species have differential sensitivities to water pollution, with several studies reporting high tolerance of heavy metal pollution. We investigated the impact of both zinc-rich mine waste and organic effluent on chironomids within an effectively pristine background using the Chironomid Pupal Exuviae Technique (CPET). Chironomid species assemblages were strongly influenced by both mine drainage and organic pollution. Community composition differed between unpolluted streams and locations downstream of the pollution sources, and between the two different sources of pollution. Thirty seven of the most abundant species exhibited strong responses to water pollution varying from greatly increased abundance to complete absence. Ten species had higher abundance at one of the polluted sites compared to unpolluted sites; six in the presence of zinc pollution and five in the presence of organic pollution. One species responded positively to both pollution types. Our results indicate that contrary to the mixed reports of Australian chironomids for being insensitive to pollution, we found that they displayed a strong pollution response to both organic and heavy metal contamination.     

PHYLOGENETIC VARIATION IN THE TOLERANCE AND UPTAKE OF ORGANIC CONTAMINANTS

An investigation into the phylogenetic variation of plant tolerance and the root and shoot uptake of organic contaminants was undertaken. The aim was to determine if particular families or genera were tolerant of, or accumulated organic pollutants. Data were collected from sixty-nine studies. The variation between experiments was accounted for using a residual maximum likelihood analysis to approximate means for individual taxa. A nested ANOVA was subsequently used to determine differences at a number of differing phylogenetic levels. Significant differences were observed at a number of phylogenetic levels for the tolerance to TPH, the root concentration factor and the shoot concentration factor. There was no correlation between the uptake of organic pollutants and that of heavy metals. The data indicate that plant phylogeny is an important influence on both the plant tolerance and uptake of organic pollutants. If this study can be expanded, such information can be used when designing plantings for phytoremediation or risk reduction during the restoration of contaminated sites.     

Remediation of contaminated soils by biotechnology with nanomaterials: bio-behavior,applications, and perspectives

Soil contamination caused by heavy metals and organic pollutants has drawn world-wide concern. Biotechnology has been applied for many years to the decontamination of soils polluted with organic and inorganic contaminants, and novel nanomaterials (NMs) has attracted much concern due to their high capacity for the removal/stabilization/degradation of pollutants. Recently, developing advanced biotechnology with NMs for the remediation of contaminated soils has become a hot research topic. Some researchers found that bioremediation efficiency of contaminated soils was enhanced by the addition of NMs, while others demonstrated that the toxicity of NMs to the organism negatively influenced the repair capacity of polluted soils. This paper reviews the application of biotechnology and NMs in soil remediation, and further provides a critical view of the effects of NMs on the phytoremediation and micro-remediation of contaminated soils. This review also discusses the future research needs for the combined application of biotechnology and NMs in soil remediation.     

藏东南急尖长苞冷杉林林隙土壤线虫群落特征

为了解西藏东南部急尖长苞冷杉林林隙土壤线虫群落特征,对林隙、非林隙土壤0~30 cm范围内不同深度土层的线虫群落进行调查,并用线虫个体密度、生物多样性指数和营养类群指数等特征值分析了土壤线虫群落的结构及多样性特点.结果表明： 采用浅盘法分离得到土壤线虫26801 条,隶属于2纲5目40科64属;线虫个体密度平均为3552 条·100 g-1干土,表聚性极强.垫咽属、丝垫刃属为林隙土壤线虫优势属;食细菌性线虫为主要营养类群.土壤有机质的分解兼有真菌分解和细菌分解两种途径.线虫的生物多样性及丰富度与林隙面积有关.土壤线虫群落特征表明,林隙具有异于郁闭林分和林间空地的特性,在环境指示方面具有应用潜力.     

大气CO2浓度升高对稻田土壤线虫群落的影响

本试验利用无锡稻 麦轮作FACE系统研究平台 ,开展了稻田土壤线虫群落对大气CO2 浓度升高响应的研究。实验中共观测到线虫 2 7科 4 0属 ,其中短腔属 (Brevibucca)、茎属(Ditylenchus)和垫刃属 (Tylenchus)为优势属。拔节期稻田土壤线虫总数、食细菌线虫和捕食 /杂食线虫对大气CO2 浓度升高表现出正响应。食真菌线虫在拔节期和抽穗期对CO2 浓度升高表现出负响应 ,成熟期捕食 /杂食线虫对CO2 浓度升高表现出负响应。在FACE条件下 ,植物寄生线虫的潜根属 (Hirschmanniella)和散香属 (Boleodorus)线虫数量显著增加 ,对CO2 浓度升高敏感     

江苏省不同种植年限的西/甜瓜农田土壤线虫群落特征

在江苏省主要西/甜瓜产区,采集不同种植年限的西/甜瓜农田土壤,采用线虫形态学的鉴定方法,分析了不同种植年限西/甜瓜农田土壤线虫的数量、群落结构及相关生态指数的变化。结果表明:所有调查样点中,共发现土壤线虫54属,平均682条·100 g^-1干土,其中原杆属线虫、拟丽突属线虫和矮化属线虫在不同种植年限的西/甜瓜农田土壤中均为优势属;随着种植年限的增加,土壤线虫的总数量虽无显著变化,但其中食细菌类线虫和杂食-捕食类线虫数量显著减少,而植物寄生类线虫数量显著增加;植物寄生类线虫中的矮化属、根结属线虫数量不断增加;随着种植年限的增加,土壤线虫的多样性指数(H)、瓦斯乐斯卡指数(WI)、自由生活线虫成熟度指数(MI)显著降低,线虫通道指数(NCR)、植物寄生线虫成熟度指数(PPI)、PPI/MI显著升高,其他指数无显著变化;相关性分析结果显示,土壤线虫数量与土壤pH、速效磷、有效锌和有效硼均呈显著正相关;土壤p H、有机质、全氮、速效钾、有效硼和有效锌对土壤优势属线虫的影响较大;连续种植西/甜瓜会增加土壤植物寄生类线虫数量,进而可能造成西/甜瓜连作障碍的发生;连续种植6～1...     

Does bioturbation by a benthic fish modify the effects of sediment contamination on saltmarsh benthic microalgae and meiofauna?

A microcosm experiment was conducted using a replicated factorial design to determine if a benthic fish modifies the effects of sediment-bound contaminants (diesel fuel and two levels of a Cu, Cr, Pb, Hg and Cd mixture) on saltmarsh benthic primary producers and consumers. The naked goby, Gobiosoma bosc, a burrowing fish that preys on small macrofauna, was added to experimental microcosms. Goby burrowing and foraging significantly increased turbidity and disrupted the sediment surface. Results were typified by complex and varied responses with many statistically significant effects and interactions among treatments. Although G. bosc modified the responses to both diesel and metal pollution in invertebrates (but not microalgae), bioturbation did not increase or decrease the toxic effects of metals or diesel, and diesel-metal interactions did not vary in response to G. bosc. Specifically, G. bosc inhibited a trend toward diesel-induced increases in nematode abundance, and diesel toxicity inhibited increases in ostracod abundance stimulated by G. bosc. Diatoms, nematodes and the copepod Pseudostenhelia wellsi decreased in treatments with G. bosc. However, G. bosc lead to increases in cyanobacteria and ostracods and a trend toward increases in the copepod Pseudobradya sp. Our findings suggest that microcosm experiments are potentially poor mimics of natural systems without bioturbation. Conclusions about the direct and indirect effects of contaminants may differ with and without bioturbation. Finally, our work suggests that the direct effects of toxicants may inhibit or mask bioturbation effects that stimulate population growth of some meiofauna.     

公路源重金属对青藏高原高寒草甸土壤线虫群落的影响

为了解重金属对青藏高原高寒草甸土壤线虫群落的影响,在邦杰塘草原利用公路源重金属含量差异,采用高通量测序技术,分析重金属对高寒草甸土壤线虫群落多样性及群落组成的影响。结果表明：在重金属含量较低样本中,土壤线虫群落Shannon指数、Ace指数、Chao指数比重金属含量较高样本均要小,且整体上Shannon指数、Ace指数、Chao指数与重金属含量较高样本差异显著（P<0.05）。重金属含量升高改变了高寒草甸土壤线虫纲水平和目水平的群落结构,使近自然状况下的色矛纲（Chromadorea）、小杆目（Rhabdtida）优势土壤线虫群落转变为一类未分类线虫纲（unclassified_p_Nematoda）、一类未分类线虫目（unclassified_p_Nematoda）的优势土壤线虫群落。重金属Cu、Pb、Zn、Cd与线虫门（Nematoda）和刺嘴纲（Enoplea）正相关,但与色矛纲（Chromadorea）负相关,且对土壤线虫Chao指数的变异解释比例依次减小。研究表明土壤重金属含量对青藏高原高寒草甸土壤线虫群落多样性及组成产生很大影响,但仍需对高寒草甸区域进行系统的土壤线虫调查,并丰富土壤线虫生物信息数据库。     

Aboveground mammal and invertebrate exclusions cause consistent changes in soil food webs of two subalpine grassland types,but mechanisms are system‐specific

Ungulates, smaller mammals, and invertebrates can each affect soil biota through their influence on vegetation and soil characteristics. However, direct and indirect effects of the aboveground biota on soil food webs remain to be unraveled. We assessed effects of progressively excluding aboveground large‐, medium‐ and small‐sized mammals as well as invertebrates on soil nematode diversity and feeding type abundances in two subalpine grassland types: short‐ and tall‐grass vegetation. We explored pathways that link exclusions of aboveground biota to nematode feeding type abundances via changes in plants, soil environment, soil microbial biomass, and soil nutrients. In both vegetation types, exclusions caused a similar shift toward higher abundance of all nematode feeding types, except plant feeders, lower Shannon diversity, and lower evenness. These effects were strongest when small mammals, or both small mammals and invertebrates were excluded in addition to excluding larger mammals. Exclusions resulted in a changed abiotic soil environment that only affected nematodes in the short‐grass vegetation. In each vegetation type, exclusion effects on nematode abundances were mediated by different drivers related to plant quantity and quality. In the short‐grass vegetation, not all exclusion effects on omni–carnivorous nematodes were mediated by the abundance of lower trophic level nematodes, suggesting that omni–carnivores also depended on other prey than nematodes. We conclude that small aboveground herbivores have major impacts on the soil food web of subalpine short‐ and tall‐grass ecosystems. Excluding aboveground animals caused similar shifts in soil nematode assemblages in both subalpine vegetation types, however, mechanisms turned out to be system‐specific.     

The detritus food-web and the diversity of soil fauna as indicators of disturbance regimes in agro-ecosystems

An ongoing study initiated in August 1990 investigated the effects of disturbances (organic mulching, cultivation, herbicides) on the detritus food-web in annual (maize) and perennial (asparagus) cropping systems. In this paper we attempt to simultaneously assess the functional and taxonomic structure of various components of this food-web. Biota in the perennial system was the most responsive to disturbance. The microflora was strongly influenced by mulching, and through tritrophic effects caused increases in top predatory but not most microbe-feeding nematodes. These effects have become increasingly apparent as the study has progressed and, in the asparagus site, have worked their way down the soil profile over time. Cultivation in the asparagus site caused large increases in bacterial-feeding nematodes, probably due to the high weed levels which developed during the winter months under that treatment. Evidence appears to exist for a cascade effect operating due to top down effects of nematodes on lower trophic levels. Ordination analysis of the nematode data demonstrated that nematode populations were more closely related to the state of environmental factors at earlier samplings than at contemporary samplings, and that the linkages between the nematode and environmental data sets strengthened over time. For both the nematode and soil-associated beetle data distinct assemblages of organisms were found in the mulched plots; distinct assemblages of nematode genera also emerged in the cultivated asparagus plots after two years. The soil-associated macrofauna was usually linked to high weed and surface organic residue levels. Species diversity of soil associated nematodes was not particularly responsive to disturbance while that of the soil-associated beetles was strongly enhanced by mulching and (sometimes) high weed levels. Approaches based on either functional group or species composition data emerged in our study as reasonably sensitive indicators for assessing the response of the soil biota to disturbance.     

Ecology of nematophagous fungi: Effect of the soil nutrients N,P and K,and seven major metals on distribution

The effects of the major soil nutrients and seven common metals on the distribution of nematophagous fungi were evaluated by comparing the concentration of the elements in soils with and without nematophagous fungi. Mineral nutrients, which were all positively correlated with nematode density, were the most important elements determining the presence of such fungi. Endoparasites producing adhesive conidia were independent of all the elements tested, while those species forming ingested conidia were isolated from soils high in nutrients, indicating a strong dependence on nematode density. Knob forming predators which rely on their ability to spontaneously produce traps to obtain nutrients were isolated from soils with low concentrations of mineral nutrients, while species with constricting rings were isolated from richer soils containing a greater density of nematodes. Net-forming species were largely independent of soil fertility, although generally they were isolated from soils with limited nutrientsd, especially K. Like other fungi, nematophagous fungi are generally not found in soils containing elevated concentrations of heavy metals. The results indicate that even concentrations of heavy metals which naturally occur in Irish soils can restrict the distribution of this fungal group. However the endoparasiteMeria coniospora is tolerant to all metals and to Cu in particular.     

Soil free-living nematodes as indicators of both industrial pollution and livestock activity in Central Asia

The effect of industrial pollution on soil free-living nematode communities, trophic groups, and taxon composition was investigated along an 18-km transect that included the Angren power plant, a gold-refinery plant, farm areas, and recreation areas. Soil samples were collected in May 2005 and October 2006 from the upper (0–10 and 10–20 cm) soil layers in downwind directions from the industrial complex emission sources of the Angren industrial sites.Direct and indirect (through soil property changes), separate and integrated effects of industrial pollution and livestock activity on the soil nematode community were found. The total number of nematodes was found to be negatively correlated with the amounts of chemical elements in soil and positively correlated with the calcium concentration in soil. The nematode communities, trophic diversity, and taxon composition were found to be affected by the variety and concentration of chemical elements.The widely used ecological indices applied in the present research were sensitive to environmental disturbances caused by industrial pollution as well as livestock activity. The Wasilewska index, nematode channel ratio, and maturity index were mostly affected by trace metal concentration, while the diversity indices and species richness were mostly affected by soil property changes. The nematode channel ratio indicated that the bacterial-based decomposition process was dominant in soils exposed to both strong industrial pollution and livestock activity. The diversity indices indicated the disappearance of rare species in the industrial area and an increase of the contribution of common nematodes with increasing depth and distance from the unfavorable area. The current study confirmed that the grazing in accompaniment to industrial pollution, intensify a negative effect on soil nematode communities.     

高等植物重金属耐性与超积累特性及其分子机理研究

由于重金属污染日益严重, 重金属在土壤_植物系统中的行为引起了人们的高度重视。高等植物对重金 属的耐性与积累性, 已经成为污染生态学研究的热点。近年来, 由于分子生态学等学科的发展, 有关植物对重金属的解毒和耐性机理、重金属离子富集机制的研究取得了较大进展。高等植物对重金属的耐性和积累在种间和基因型之间存在很大差异。根系是重金 属等土壤污染物进入植物的门户。根系分泌物改变重金属的生物有效性和毒性, 并在植物吸收重金属的过程中发挥重要作用。土壤中的大部分重金属离子都是通过金属转运蛋白进入根细胞, 并在植物体内进一步转运至液泡贮存。在重金属胁迫条件下植物螯合肽 (PC) 的合成是植物对胁迫的一种适应性反应。耐性基因型合成较多的PC, 谷胱甘肽 (GSH) 是合成PC的前体, 重金属与PC螯合并转移至液泡中贮存, 从而达到解毒效果。金属硫蛋白 (MTs) 与PC一样, 可以与重金属离子螯合, 从而降低重金属离子的毒性。该文从分子水平上论述了根系分泌物、金属转运蛋白、MTs、PC、GSH在重金属耐性及超积累性中的作用, 评述了近 10年来这方面的研究进展, 并在此基础上提出存在的问题和今后研究的重点。