Lead tolerance and accumulation in the gametophytes of the fern Athyrium yokoscense

The fern Athyrium yokoscense is known to be highly tolerant to lead toxicity, and is a lead hyperaccumulator that can accumulate over 1,000 g g^–1 of lead in its dry matter. In this work, we examined whether the gametophytic generation of A. yokoscense also resists lead toxicity like the sporophytic generation. Spore germination in A. yokoscense was more tolerant to Pb²⁺, compared to that in other fern species, such as Pteridium aquilinum, Lygodium japonicum and Pteris vittata. In addition, the early gametophyte development of A. yokoscense was not much affected by 10 M Pb²⁺, as evaluated from the prothallial growth and rhizoid development. We also showed that Athyrium gametophytes could accumulate more than 10,000 g g^–1 of lead, and that the lead was localized in the cytosol and vacuole of rhizoidal cells, as determined by a transmission electron micrograph. These results indicate that Athyrium gametophytes have the ability to accumulate lead in the rhizoids. Furthermore, the gametophytes were found to include a large amount of proanthocyanidins (condensed tannins). Because proanthocyanidins have a latent ability to complex with lead ions, the possible roles of proanthocyanidins in the lead tolerance and accumulation of Athyrium gametophytes are discussed.     

Induction of callus from a metal hypertolerant fern, Athyrium yokoscense, and evaluation of its cadmium tolerance and accumulation capacity

The callus of a metal hypertolerant fern, Athyrium yokoscense, was induced from the spores generated on a small sectioned frond in vitro. The callus grew vigorously with the periodical medium change, especially in a liquid culture. When the callus and regenerated tissues were exposed to Cd, every tissue tolerated at least 1 mM Cd for >1 month. These tissues accumulated high levels of Cd (maximum 3.3 mg g^–1 dry weight in roots) in accordance with the Cd concentration of the medium, and the Cd concentrations of all parts, except roots, were at a similar level. The data suggest that the Cd tolerance of this fern is basically independent of the plant parts and the developmental stages, although the accumulation ability is higher in roots than in the other plant parts.     

The role of the root cell wall in the heavy metal tolerance ofAthyrium yokoscense

Cells of the roots ofA. yokoscense growing on metalliferous habitats were fractionated into their cell wall and cytoplasmic components. About 70–90% of the total copper, zinc and cadmium was located in the cell wall. Copper had a markedly greater affinity for the cell wall than zinc and cadmium, and was prevented from entering the cytoplasm. A large proportion of these heavy metals in the cell wall were exchanged as ions. The capacity of the cell wall for exchanging metal ions inA. yokoscense was higher than in other plants growing on metalliferous habitats. However, compared with different ferns unable to grow on metalliferous habitats, this capacity was not unique toA. yokoscense. Consequetly, the root cell wall ofA. yokoscense is considered to be an important site of metal ion storage and may play the role of an excretory organ for heavy metals. On the other hand, as proportion of the heavy metls was transported to the cytoplasm, where the metal content was much higher than the average for normal ferns. This would suggest thatA. yokoscense has another metabolic mechanism related to metal tolerance.     

Accumulation of heavy metals by aquatic mosses. 2: Rhynchostegium riparioides

A study was made of general ecology and metal accumulation in the widespread aquatic moss Rhynchostegium riparioides, (Hedw.) C. Jens. with a view to developing the use of this species as a monitor of heavy metal pollution. In order to establish a data bank for statistical analysis, samples of water and moss were taken within a 6-week period from 105 sites (10-m reaches) in Northern England from streams and rivers of diverse physical and chemical types. Analyses were made of 14 metals (Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba, Pb) in both 2-cm tips and whole plants. The same 14 metals were also measured in both total and filtrable water, together with 12 other variables. Samples of tips were easier to prepare for analysis, but had significantly (p < 0.001) lower concentrations of all metals except Na and K. Significant correlations (p < 0.001) between metal in moss and aqueous metal were found for ten metals (Na, K, Mg, Ca, Mn, Cu, Zn, Cd, Ba, Pb). Correlations between metals in moss and in water were in general similar for tips and whole plants, but much higher for tips with Na, Zn and Cd; the relationship was quite similar whether total or filtrable water was considered, with the exception of Ba where the correlation was much higher with the latter. A multiple regression was used to suggest which variables in water and/ or moss may influence accumulation of Co, Ni, Cu, Zn, Cd, Ba and Pb in the moss. For instance, the variables which had a very highly significant effect on Pb in tips were Pb, filtrable reactive phosphate and Zn in the water. A discussion is included of how the data may be used for monitoring purposes.     

Use ofCladophora glomerata to monitor heavy metals in rivers

Methods were developed for the use ofCladophora glomerata to monitor heavy metal concentrations in flowing waters. At least under conditions without marked fluctuations in ambient metal concentration, there was no detectable difference in the metal concentrations of young plants between terminal 2-cm lengths of filament and whole plants. In order to establish the relationship between metal concentration in plant and that in water, 60 algal and water samples were analyzed from sites in northern England for Fe, Cu, Zn, Cd and Pb. Other environmental variables were measured at the time in order to assess their influence on metal accumulation. There were highly significant correlations for each of the five metals between concentrations in alga and water. The regression equations relating metal in alga to metal in water permit an unknown environmental metal concentration to be estimated from the algal concentration. Multiple stepwise regression analyses were used to indicate environmental factors which may influence metal accumulation; for instance, Fe appears to have a positive influence on Cu accumulation. In generalCladophora accumulates much less metal than bryophytes, but the slope relating metal in alga to metal in water is steeper, particularly for Pb. This means thatCladophora is especially useful where there is a need for a sensitive indicator of differences between sites or sampling occasions.     

Biosystematic investigations on the lady fern(Athyrium filix-femina)

In EuropeAthyrium filix-femina has a constant chromosome number (2n = 80) and is sexual. The normal type of reproduction is intergametophytic crossing. In the gametophyte phase there is a hormone system which induces dark germination of spores and antheridium formation. Sporophytes originating from single prothalli show that a genetic load is present in all population examined. It appears not to be a simple allelic load but a complicated balanced system. Morphological variability can be interpreted as the expression of the genetic heterogeneity of populations. There are no crossing barriers, not even between insular populations hundreds of kilometers apart.     

Enteromorpha as a monitor of heavy metals in estuaries

An account is given of the use of Enteromorpha to monitor zinc, cadmium, mercury and lead pollution in six estuaries and the British North Sea coast. The ranges for each element were: Zn, 19–437 µg g^–1; µg g^–1 Cd, 0.07–4.8 µg g^–1; Hg, 0.02–0.23 µg g^–1. It is suggested that tissue analysis of Enteromorpha is one of the most useful biological techniques available in estuaries for pin-pointing aqueous (as opposed to sediment) metal contamination, and also for providing data suitable for world-wide comparisons. Provisional values are given for concentrations corresponding to moderate and high pollution.Deceased     

矿区道路两侧雪岭云杉叶片重金属富集效应

采矿及矿产品运输过程会对环境造成重金属污染进而对生物体产生危害。为定量描述艾维尔沟矿区道路两侧重金属污染程度、明确雪岭云杉叶片对重金属的吸收富集效应,通过采集雪岭云杉叶片和土壤样品,测试其铅(Pb)、锌(Zn)、镉(Cd)、砷(As)、铜(Cu)、铬(Cr)的含量,分析重金属的富集效应和空间分异特征。结果表明:(1)雪岭云杉叶片和土壤中各重金属含量差异显著(P0.05),叶片中Pb的含量显著高于其余重金属(P0.05),平均达86.28μg/g,土壤中Zn、Cu超过了国家土壤质量标准的一级限制值,而As比三级限制值大41%;(2)以背景区(板房沟林场)的土壤和雪岭云杉叶片重金属为评价标准,研究区雪岭云杉叶片重金属综合污染指数为2.05,属中度污染,其中As和Pb单项污染指数较高,达3.65和2.57。研究区土壤重金属综合污染指数为1.69,属轻度污染;(3)随距离增加,除土壤和叶片中Pb含量表现为负线性递减外,As和Cu均表现为先升高后降低,土壤中Cr、Zn逐渐升高,但叶片中Cr逐渐降低,Zn变化不大;(4)冗余分析(RDA)结果显示土壤中Cu、As、Pb与雪岭云杉死树胸径和树高呈正相关关系,而Cr、Zn与其呈负相关。采矿及运输已对土壤和雪岭云杉的生长造成影响,本文对天山雪岭云杉森林的生态修复与保育具有一定的借鉴作用。     

Accumulation, depuration and distribution of cadmium and zinc in the green-lipped mussel Perna viridis (Linnaeus) under laboratory conditions

Ecotoxicological tests were conducted in the green-lipped mussel Perna viridis under laboratory conditions. Different rates of accumulation and depuration in soft tissues are found and this might be due to different mechanisms of metal binding and regulation. At the end of depuration, Cd levels in soft tissues of P. viridis were 10–30 times higher than before exposure, while Zn levels in soft tissues were almost similar to levels before exposure. These results indicate that P. viridis is a good biomonitoring organism for Cd but Zn levels might be actively regulated. It remains uncertain whether P. viridis is a good biomonitoring organism of environmental Zn contamination. However, the positive patterns, although different rates, of accumulation and depuration for Cd and Zn support the use of P. viridis as a biomonitoring agent for such metals.     

Avoidance response of Midge Larvae (Chironomus Tentans) to sediments containing heavy metals

Avoidance reactions of chironomid larvae to contaminated sediment taken from a heavy metal impacted lake were studied. Heavy metal levels in the test sediment ranged from background of 0.6 parts per million (ppm) cadmium, 77 ppm zinc and 17 ppm chromium to a maximum of 1,029 ppm cadmium, 17,262 ppm zinc and 2,106 ppm chromium. A linear relationship was established between cadmium and zinc levels in the sediment and avoidance by chironomids.An approximate threshold avoidance of metals in the sediment was determined to be between 213–422 ppm cadmium, 4385–8330 ppm zinc and 799–1513 ppm chromium.Supported by NIH Training Grant Number 5T01-ES00071 from National Institute of Environmental Health Sciences and in part by an NSF (RANN) Grant Number GI-35106.Purdue University Agricultural Experiment Station, Jour. No. 6474.     

Interactions of lichens with heavy metals

Recent developments in knowledge about the interactions between lichens and heavy metals at different levels, from populations to cells and from ecology to molecular biology are reviewed. Sources of heavy metals, mechanisms of heavy metal accumulation and detoxification by lichens are discussed. Special emphasis is placed on ultrastructural changes as well as physiological parameters such as membrane integrity, pigment composition, chlorophyll a fluorescence, photosynthesis, respiration, contents of ATP, amino acids, ergosterol, ethylene, non-protein thiols, activity of antioxidant enzymes and expression of stress proteins.     

The influence of heavy metal stress on the level of some flavonols in the primary leaves of Phaseolus coccineus

Qualitative and quantitative analysis of flavonols was carried out in young and older primary leaves of runner bean plants (Phaseolus coccineus L.) treated with Cd²⁺ (25 μM) and Cu²⁺ excess (25 and 300 μM) for 12 days. The presence of quercetin-3-O-D-rhamnoside, kaempferol-3-O-D-rhamnoside, quercetin-3-O-D-glucuronide and kaempferol-3-O-D-glucuronide was found in the plant. Quercetin-3-O-D-rhamnoside predominated in the control and heavy metal-stressed plants. The content of individual flavonols increased under heavy metal treatment, particularly in young plants. The flavonol level depended on the metal and its concentration. A protective role of flavonols in plants under heavy metal stress is discussed.     

施氮对镉胁迫下山杨幼苗叶片氮磷钾吸收及镉积累量的影响

为探究山杨在重金属镉胁迫与增施外源氮复合处理条件下的生长及元素积累差异,该研究以山杨幼苗为材料,通过盆栽实验研究在重金属镉(Cd)胁迫下增施外源氮(N)对其形态、叶绿素、淀粉和可溶性糖含量、叶片中全氮(N)、全磷(P)、全钾(K)以及Cd含量的影响。结果表明：(1)单独Cd处理显著抑制山杨幼苗的叶片宽度和茎粗;施加外源N能够缓解Cd胁迫对植株的毒害,其叶长、叶宽和茎粗较单独Cd处理显著增加。(2)单独Cd处理后山杨叶片的叶绿素含量和淀粉含量均比对照显著下降,而其可溶性糖含量显著增加;与单独Cd处理相比,Cd+N复合处理后山杨的叶绿素含量显著增加,淀粉含量却显著下降,而可溶性糖含量略有降低。(3)与对照相比,单独Cd处理后,山杨叶片全N含量显著下降,全P含量显著增加;单独N和Cd+N复合处理后叶片全N含量均显著增加,全P含量均显著下降;全K含量在各处理下均无显著差异。(4)在Cd胁迫下山杨幼苗叶片的Cd含量比对照极显著增加,且Cd+N复合处理后叶片的Cd含量约是单独Cd处理的2倍。研究认为,增施氮素处理可显著提高山杨幼苗对镉胁迫环境的适应能力以及叶片对镉的富集能力。     

Factors affecting tissue distribution of heavy metals

Metal distribution in an organism at any one time is a resultant of many extrinsic and intrinsic factors. Improved analytic methodology has made it feasible to obtain highly sensitive determinations for many metals in a single sample. Thus, it is now feasible to examine patterns of metal distribution. We report on a study of the effect of age on metal patterns in the common tern,Sterna hirundo, a fisheating seabird. We contrast the levels of nine metals in the liver of adult and young terns and compared these with levels in tern eggs. Unlike many previous studies, adults did not have significantly higher levels of metals, although for most metals, levels in eggs were significantly lower than liver levels of young and adults. The intermetal correlations showed more significant positive correlations for adults and eggs than for chicks, the latter showing instead a correlational chaos, probably reflecting the immaturity of their physiologic defense mechanisms and the absence of dynamic equilibrium.     

Characterization of a heavy metal-tolerant endomycorrhizal fungus from the surroundings of a zinc refinery

An arbuscular mycorrhizal fungus was isolated from the rhizosphere of Agrostis capillaris growing in the contaminated surroundings of a zinc refinery in The Netherlands. After examination of the infection pattern and the spores, it was characterized as Scutellospora dipurpurescens, which was first isolated from a reclaimed coal mine area in West Virginia.     

The recovery of heavy metals using encapsulated microbial cells

We prepared capsules containingSaccharomyces cerevisiae andZoogloea ramigera cells for the removal of lead (II) and cadmium ions. Microbial cells were encapsulated and cultured in the growth medium. TheS. cerevisiae cells grown in the capsule did not leak through the capsule membrane. The dried cell density reached to 250 g/l on the basis of the inner volume of the 2.0 mm diameter capsule after 36 hour cultivation. The dry whole cell exopolymer density of encapsulatedZ. ramigera reached to 200 g/L. The capsule was crosslinked with triethylene tetramine and glutaric dialdehyde solutions. The cadmium uptake of encapsulated whole cell exopolymer ofZ. ramigera was 55 mg Cd/g biosorbent. The adsorption line followed well Langmuir isotherm. The lead uptake of the encapsulatedS. cerevisiae was about 30 mg Pb/g biomass. The optimum pH of the lead uptake using encapsulatedS. cerevisiae was found to be 6. Freundlich model showed a little better fit to the adsorption data than Langmuir model. 95 percent of the lead adsorbed on the encapsulated biosorbents was desorbed by the 1 M HCl solution. The capsule was reused 50 batches without loosing the metal uptake capacity. And the mechanical strength of the crosslinked capsule was retained after 50 trials.     

Characterizing the accumulation of various heavy metals in native plants growing around an old antimony mine

The objective of this study was to explore potential plant candidates to act as phytoremediators around the Xikuangshan mine, Hunan Province, China. Native plants including Imperata cylindrical (L), Rumex patientia L., Fagopyrum dibotrys (D.Don), Fagopyrum dibotrys (D.Don), Phytolacca americana L., Dryopteris erytbrosora, Pteriduum aquilinum var. latiusculum (Desv), Nephrolepiscordifolia (L) Presl, Oplismenus undulatifolius (A) Bea, Erigeron annuus (L) Pers, and soils samples were collected. As, Sb, Hg, Cd, Cr, Pb, and Zn levels were measured in soil and plant samples. The concentrations of As, Sb, Hg, and Cd in soils were above the corresponding background values for Hunan province. R. Patienti, P. aquilinum, and P. americana had large bioconcentration factors (BAFs) and high translocation factors (TFs) for Sb; and the same showed in D. erytbrosora for Hg, P. vittata for Cd, I. cylindrical for Cr, and D. erytbrosora for Pb and Zn. In general, perennial plants showed high heavy metal contents in roots, and TFs greater than 1 were only observed for Sb in E. annuus and Cr in O. undulatifolius. These results demonstrate that several native plants growing around Xikuangshan are potential phytoremediators for metal and metalloid contaminated soils.     

Genotoxicity assessment in aquatic environments under the influence of heavy metals and organic contaminants

The genotoxicity of river water and sediment including interstitial water was evaluated by microscreen phage-induction and Salmonella/microsome assays. Different processes used to fractionate the sediment sample were compared using solvents with different polarities. The results obtained for mutagenic activity using the Salmonella/microsome test were negative in the water and interstitial water samples analysed using the direct concentration method. The responses in the microscreen phage-induction assay showed the presence of genotoxic or indicative genotoxic activity for at least one water sample of each site analysed using the same concentration method. Similar results were obtained for interstitial water samples, i.e. absence of mutagenic activity in the Salmonella/microsome test and presence of genotoxic activity in the microscreen phage-induction assay. Metal contamination, as evidenced by the concentrations in stream sediments, may also help explain some of these genotoxic results. Stream sediment organic extracts showed frameshift mutagenic activity in the ether extract detected by Salmonella/microsome assay. The concentrates evaluated by microscreen phage-induction assay identified the action of organic compounds in the non-polar, medium polar and polar fractions. Thus, the microscreen phage-induction assay has proven to be a more appropriate methodology than the Salmonella/microsome test to analyse multiple pollutants in this ecosystem where both organic compounds and heavy metals are present.     

Effect of heavy metals on chromatin supraorganization, nuclear phenotypes, and survival ofTriatoma infestans

The nuclear phenotypes and survival of the hemipteran,Triatoma infestans (Hemiptera, Reduviidae), were studied in specimens treated with copper sulfate and methylmercury. The objective was to determine whether changes in chromatin supraorganization and insect survival similar to those promoted by other stressing agents could also be induced by heavy metals. At the concentrations used, copper sulfate and methylmercury were toxic to the cells, mainly inducing nuclear degenrration in the Malpighian tubules and being lethal to a large part of the insect population. Although some individual resistance was found, especially in fasted specimens, heavy metals were found to be much more lethal than was, for instance, a thermal shock at 0°C for 12 h. The nuclear phenotypes detected after heavy metal treatment were similar to those reported under other stressing conditions. However, the frequency at which nuclei exhibited aspects of heterochromatin unraveling was much higher than that found in fasted and thermal-shocked specimens, and was independent of the heavy metal type used. If this phenotype represents an attempt to improve opportunities for extensive cell and insect survival, it was not sufficiently effective. In 5th instar nymphs, the effect of CuSO₄ on chromatin supraorganization was detected at early steps of spermatogenesis but not in the cells which were at late spermiogenesis when the metal was administered. This is probably due to changes in nuclear protein composition and to the tightly packed state of the DNA-protein complexes occurring at spermiogenesis, which may protect chromatin from damages. However, when CuSO₄ was supplied to 4th instar nymphs, it slowed down the spermiogenesis process, possibly due to several factors including Cu²⁺ binding to DNA phosphates.     

Comparative strategies of heavy metal accumulation by crustaceans: zinc,copper and cadmium in a decapod,an amphipod and a barnacle

This study investigates the comparative strategies of accumulation under standardised laboratory conditions of the essential metals zinc and copper, and the non-essential metal cadmium by three crustaceans of different taxa; vizPalaemon elegans Rathke (Malacostraca: Eucarida: Decapoda),Echinogammarus pirloti (Sexton & Spooner) (Malacostraca: Peracarida: Amphipoda) and the barnacleElminius modestus Darwin (Cirripedia: Thoracica).The decapodP. elegans regulates body zinc concentrations to a constant level (ca. 79 µg Zn g^–1) over a wide range of dissolved metal availabilities until regulation breaks down at high Zn availabilities and net accumulation begins. The amphipodE. pirloti accumulates zinc at all dissolved zinc concentrations but at a low net rate such that the accumulation strategy approaches that of regulation. The barnacleE. modestus accumulates zinc to high body concentrations with no significant excretion of accumulated zinc. In the case of copper,P. elegans similarly regulates body copper concentrations to a constant level (ca. 129 µg Cu g^–1) over a range of dissolved copper availabilities until regulation breaks down at high copper concentrations. Both the amphipodE. pirloti and the barnacleE. modestus on the other hand accumulate copper at all dissolved copper exposures with no evidence of regulation. All three crustaceans accumulate the non-essential metal cadmium at all dissolved cadmium concentrations without regulation.Heavy metal accumulation strategies therefore vary between crustacean taxa and between metals. Uptake rates for zinc and cadmium have been estimated for the three crustaceans and can be interpreted in terms of cuticle permeability and way of life of each crustacean. Examination of these uptake rates provides an insight into possible reasons behind the adoption of particular metal accumulation strategies.