植物铜转运相关蛋白研究进展

环境中过量的铜会损害植物细胞的功能、降低酶的活性并且破坏蛋白质的结构。植物中有一个复杂的金属转运网络,对维持植物体内铜的动态平衡发挥着重要作用。综述了重金属铜对植物的毒害,详细介绍了铜转运相关蛋白及其对铜的转运和调控机制。     

Reevaluating the free-ion activity model of trace metal availability to higher plants

The plant uptake and toxicity of many metals show a marked dependence on the aqueous speciation of the metal, and these responses often correlate best with the activity of the free metal ion. Exceptions to this generalization have been observed, however, and we sought to critically reexamine the theoretical foundation of the free-ion activity model (FIAM) of metal bioavailability to higher plants. Binding by an apoplastic functional group is often envisioned as a requisite step in the absorption or toxicity of a metal, and can be modeled in a variety of ways. Typically, however, speciation of the bulk solution is calculated without regard to such surface binding, even though it could influence the pertinent mass balance expressions. A more thorough treatment considers simultaneous formation of both the metal-ligand complex in solution (ML) and the metal-cell surface complex (M-X). Here, empirical conformity to the FIAM can be expected, but only under pivotal assumptions about the relative sizes of the test solution and the root biomass, and about the relative binding strength of L and -X. Moreover, empirical conformity to the FIAM does not preclude cell-surface binding of the complexed metal followed by ligand exchange (ML + -X M-X + L), so that correlations between biological response and free metal-ion activity imply nothing about the molecular species that actually interacts with the cell surface. Computer simulations of Cu (II) binding by a model apoplastic ligand are used to illustrate these and other key features of the FIAM. Departures from the FIAM seem most likely when (i) the quantity of the metal-complexing ligand is limited (as may be the case in soil solution or in the rhizosphere), and/or (ii) the solution ligand is very weak.     

Influence of sediment organic enrichment and water alkalinity on growth of aquatic isoetid and elodeid plants

1. Lake eutrophication has increased phytoplankton blooms and sediment organic matter. Among higher plants, small, oligotrophic rosette species (isoetids) have disappeared, while a few tall, eutrophic species (elodeids) may have persisted. Despite recent reduction of nutrient loading in restored lakes, the vegetation has rarely regained its former composition and coverage. Patterns of recovery may depend on local alkalinity because HCO₃^? stimulates photosynthesis of elodeids and not of isoetids. In laboratory growth experiments with two isoetids (Lobelia dortmanna and Littorella uniflora) and two elodeids (Potamogeton crispus and P. perfoliatus), we test whether organic enrichment of lake sediments has a long‐lasting influence by: (i) reducing plant growth because of oxygen stress on plant roots and (ii) inhibiting growth more for isoetids than elodeids. We also test whether (iii) increasing alkalinity (from 0.17 to 3.20 meq. L^?1) enhances growth and reduces inhibition of organic sediment enrichment for elodeids but not for isoetids. 2. In low organic sediments, higher oxygen release from roots of isoetids than elodeids generated oxic conditions to greater sediment depth for Lobelia (4.3 cm) and Littorella (3.0 cm) than for Potamogeton species (1.6–2.2 cm). Sediment oxygen penetration depth fell rapidly to 0.4–1.0 cm for all four species at even modest organic enrichment and oxygen consumption in the sediments. Roots became shorter and isoetid roots became thicker to better supply oxygen to apical meristems. 3. Growth of elodeids was strongly inhibited across all levels of organic enrichment of sediments being eight‐fold lower at the highest enrichment compared to the unenriched control. Leaf biomass of isoetids increased three‐fold by moderate organic enrichment presumably because of greater CO₂ supply from sediments being their main CO₂ source. At higher organic enrichment, isoetid biomass was reduced, leaf chlorophyll declined up to 10‐fold, root length declined from 7 to <2 cm and mortality rose (up to 50%) signalling high plant stress. 4. Lobelia was not affected by HCO₃^? addition in accordance with its use of sediment CO₂. Biomass of elodeids increased severalfold by rising alkalinity from 0.17 to 3.20 meq. L^?1 in accordance with their use of HCO₃^? for photosynthesis, while the negative impact of organically enriched sediments remained. 5. Overall, root development of all four species was so strongly restricted in sediments enriched with labile organic matter that plants if growing in situ may lose root anchorage. Other experiments demonstrate that this risk is enhanced by greater water content and reduced consolidation in organically rich sediments. Therefore, formation of more muddy and oxygen‐demanding sediments during eutrophication will impede plant recovery in restored lakes while high local alkalinity will help elodeid recovery.     

Speciation of copper in relation to its bioavailability

Abstract

Copper speciation and bioavailability for Scenedesmus quadricauda has been studied in natural waters and in synthetic culture media. Other elements were studied simultaneously. When phosphorus and nitrogen limitation were excluded by adding these elements, copper was limiting algal growth in some natural waters. In the toxic range, growth inhibition by copper was highly correlated with copper detected by electrochemical methods and with calculated free copper.

Copper was toxic to S. quadricauda when free copper concentrations roughly exceeded 10^?10.5 M, and was limiting for values somewhere lower than 10^?12.5 M. Because we found copper limitation in some natural water samples, free copper concentration in those water samples therefore must have been lower than 10^?12.5 M.

The hypothesis that the free metal concentration rather than the total concentration determines bioavailability was confirmed for copper, cobalt and zinc.     

Estimates of environmental loading from copper alloy materials

Abstract

Metal release rates were measured from four different copper alloy-based materials used by the aquaculture industry: copper sheet machined into a diamond mesh, copper alloy mesh (CAM), silicon bronze welded wire mesh, and copper sheeting, and compared with conventional nylon aquaculture net treated with a cuprous oxide antifouling (AF) coating. Release rates were measured in situ in San Diego Bay using a Navy-developed Dome enclosure system at nine different time points over one year. As expected, copper was the predominant metal released, followed by zinc and nickel, which were fractional components of the materials tested. Release rates followed a temporal trend similar to those observed with copper AF coatings applied to vessel hulls: an initial spike in copper release was followed by a decline to an asymptotic low. Leachate toxicity was consistent with prior studies and was directly related to the metal concentrations, indicating the alloys tested had no additional toxicity above pure metals.     

Effect of hardness on bioavailability and toxicity of cadmium to rainbow trout

Abstract

Water quality characteristics affecting toxicity of metals to aquatic life include pH, inorganic and organic ligands (negatively charged ions and molecules), and water hardness. Ligands control the ability of natural waters to bind metals which could adversely affect aquatic life. Bioavailability of metals in natural waters is primarily controlled by alkalinity. Hardness does not affect metal complexation but can reduce acute toxicity through antagonistic mechanisms. In most natural waters, concentrations of alkalinity and hardness are similar, but they may be very different in some waters.

Most toxicity studies have not distinguished between reduced toxicity resulting from effects of hardness and that resulting from complexation of metals by ligands. A series of acute and long-term experiments were conducted to assess these relationships while exposing rainbow trout (Oncorhynchus mykiss) to cadmium (Cd) in waters of low alkalinity (30 mg L^?1) and hardnesses of 400, 200, and 50 mg L^?1 adjusted with magnesium sulfate (MgSO⁴). These tests did not show a strong antagonistic influence of Mg hardness on Cd toxicity. At Mg hardnesses of 50, 200, and 400 mg L^?1, 96-h LC50s were 3.02, 6.12, and 5.70 μg Cd L^?1, differing by a factor of only 1.8. Similarly, chronic values derived from 100-day experiments in waters with the same range of hardness were 1.47, 3.57, and 3.64 μg L^?1, respectively. With an eight-fold difference in Mg hardness, chronic values differed by a factor of only 2.5. Antagonistic properties of hardness are primarily controlled by Ca with Mg playing a minor role. The long-term role of Ca in reducing metal toxicity will require further investigation.     

Chemical speciation and bioavailability of lead and cadmium in an aquatic system polluted by sewage discharges

Abstract

A physico-chemical scheme encompassing anodic stripping voltammetry (ASV) as an analytical tool, and ultraviolet irradiation techniques, has been applied to determine the species of lead and cadmium in sewage polluted and unpolluted fresh-waters of a major perennial river located downstream of a metropolitan city in India. The physico-chemical and bioavailable species that have been identified and quantified include ASV-labile (bioavailable), particulate bound, total dissolved, non-labile or bound and organically bound metal. For precise and rapid assessment of the toxic bioavailable fraction, the ASV technique has been proposed as an analytical tool.

The river stretch, divided into reference, impact and recovery zones, has been monitored for any alteration in the distribution and partitioning of Pb and Cd amongst various physico-chemical forms. An attempt has been made to assess the impact of effluent discharge upon the receiving river by correlating concentrations of various metal-species with reference to the properties of the stream and drainage basin. Speciation analysis revealed complete association of Cd with particulates and a significant proportion of Pb in labile form, downstream of effluent outfall, thus an immediate toxic impact on the aquatic system may be posed.     

The relative importance of local conditions and regional processes in structuring aquatic plant communities

1. The structure of biological communities reflects the influence of both local environmental conditions and processes such as dispersal that create patterns in species’ distribution across a region. 2. We extend explicit tests of the relative importance of local environmental conditions and regional spatial processes to aquatic plants, a group traditionally thought to be little limited by dispersal. We used partial canonical correspondence analysis and partial Mantel tests to analyse data from 98 lakes and ponds across Connecticut (northeastern United States). 3. We found that aquatic plant community structure reflects the influence of local conditions (pH, conductivity, water clarity, lake area, maximum depth) as well as regional processes. 4. Only 27% of variation in a presence/absence matrix was explained by environmental conditions and spatial processes such as dispersal. Of the total explained, 45% was related to environmental conditions and 40% to spatial processes. 5. Jaccard similarity declined with Euclidean distance between lakes, even after accounting for the increasing difference in environmental conditions, suggesting that dispersal limitation may influence community composition in the region. 6. The distribution of distances among lakes where species occurred was associated with dispersal‐related functional traits, providing additional evidence that dispersal ability varies among species in ways that affect community composition. 7. Although environmental and spatial variables explained a significant amount of variation in community structure, a substantial amount of stochasticity also affects these communities, probably associated with unpredictable colonisation and persistence of the plants.     

Bioavailability of heavy metals in sediments of two coastal lagoons in Rio de Janeiro,Brazil

The distribution and bioavailability of trace metals in two contrasting tropical coastal lagoons were studied. The concentration of trace metals in aquatic macrophytes was compared with those found in sediments under weakly and strongly bound forms. The results showed that total metal concentrations in sediments did not explain the concentration found in plants. The highest concentrations in macrophytes were observed in the lagoon which had a higher fraction of metals weakly bound to sediments, but presented the lower total metal content. Low redox potential was the major variable keeping metals in non-bioavailable forms, possibly as refractory sulfides and metal-organic complexes. Among the macrophytes, rooted species showed lower concentrations of metals as compared to algae.     

Sulphur fractionation in calcareous soils and bioavailability to plants

Sulphur fractionation and availability to plants are poorly understood in calcareous soils. Sixty-four calcareous soils containing varying amounts of CaCO₃ were collected from ten provinces in China and their S fractions determined. Organic S was the predominant fraction of S, accounting for on average 77% of the soil total S. The amounts of adsorbed sulphate were found to be negligible. 1 M HCl extracted substantially more sulphate than either 0.01 M CaCl₂ or 0.016 M KH₂PO₄, indicating the existence of water-insoluble but acid-soluble sulphate, probably in the form of sulphate co-precipitated with CaCO₃. The concentrations of water-insoluble sulphate correlated positively with the contents of CaCO₃ and accounted for 0.03–40.3% (mean 11.7%) of soil total S. To test the bioavailability of water-insoluble sulphate, a sulphate-CaCO₃ co-precipitate labelled with ³⁵S was prepared and added to a calcareous soil in a pot experiment with either NH₄⁺ or NO₃^– as the N source. In 29 days, wheat plants took up 10.6% and 3.0% of the ³⁵S added to the soil in the NH₄⁺ and NO₃^– treatments, respectively. At the end of the pot experiment, the decrease of water-insoluble, acid-soluble, sulphate was more apparent in the NH₄⁺ than in the NO₃^– treatment. The results indicate that sulphate co-precipitated with CaCO₃ in calcareous soils may become partly available for plant uptake, depending on rhizosphere pH, if the field precipitate is similar to the laboratory prepared sample studied.     

The effect of heavy metal speciation in sediment on bioavailability to tubificid worms

The bioavailability of heavy metals in sediment to freshwater tubificid worms was compared with measures of chemical extractability using a sequential extraction procedure. In order to provide a range of test sediments of different quality, various mineral phases were prepared, in which the metals were spiked by adsorption or coprecipitation and these were then mixed with a bulk base sediment in known proportions. Results indicated good correlation between worm metal burden and metal mobilised from the sediments in the first (exchangeable) sequential extraction step for Cd, Cu and Pb. Of the other metals tested, Zn levels in the worms were found to be constant, suggesting regulation, and Ni uptake was too small for accurate measurement. In general, metals spiked to the sediment directly, or adsorbed on the clay mineral phase were found to be much more available than those bound to sewage sludge, carbonate or hydrous ferric oxide phases.     

Response of shape in vitro cultures of shape Nicotiana tabacum L. to copper stress and selection of plants from Cu-tolerant callus

In Nicotiana tabacum L. var. BEL W3 copper (Cu) at concentrations higher than 50 μM significantly inhibited callus growth and shoot regeneration. After 5–6 months of culture only a few morphogenic callus lines survived in the presence of 100 μM Cu. These calluses showed the capacity to grow and regenerate shoots through successive subcultures on medium containing 100 μM Cu. The 100 μM Cu-tolerant shoots, in comparison to regenerated control shoots, formed roots only when cultured in the presence of 100 μM Cu. From five independent Cu-tolerant callus lines in a culture period of 4–5 months more than 50 plants (defined ‘tolerant’) able to grow in presence of 100 μM Cu were obtained. These plants showed normal xylem tissue formation while control regenerated plants growing in normal Cu MS content (0.1 μM) had few xylem elements in the central cylinder. No difference as far chlorophyll content and chloroplast structure was found among Cu-tolerant and control plants. In Cu-tolerant plants, dry matter production was higher than in controls, particularly in roots. This revised version was published online in June 2006 with corrections to the Cover Date.     

Potential of aquatic macrophytes and artificial floating island for removing contaminants

Eutrophication is a major environmental issue that mankind is facing today as a result of rapid development. To reduce the eutrophication problem, we are testing an innovative artificial floating islands (AFIs) approach. AFIs include aquatic plants composed of emergent and floating macrophytes. In this experimental approach, two aquatic plants were selected to compare with the control group in order to evaluate the capacity of AFIs. These two emergent macrophytes were evaluated for a 40-day timeframe to examine their ability to purify waste water. The results showed that an AFI with purple loosestrife (Lythrum salicaria Linn.) and one with yellow-flowered iris (Iris wilsonii) have a strong ability to remove nitrogen, phosphorus, and other pollutants from water bodies. The pollutant removal rates of the AFIs with purple loosestrife and yellow-flowered iris were almost over 50%. The chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) removal rates of the AFI with purple loosestrife were about 75%, 57%, 71%, respectively. At the same time, the COD, TN, and TP removal rates of the AFI with yellow-flowered iris were 60%, 49%, and 68%, respectively. AFIs with aeration are also a good way to remove pollutants. This study reveals that AFIs can be incorporated into wetlands to reduce the effects of water contamination and help strengthen wetland restoration.     

Biosurfactant production by Pseudomonas sp. and its role in aqueous phase partitioning and biodegradation of chlorpyrifos

Aim:  To study the effect of biosurfactant on aqueous phase solubility and biodegradation of chlorpyrifos.
Methods and Results:  A Pseudomonas sp. (ChlD), isolated from agricultural soil by enrichment culture technique in the presence of chlorpyrifos, was capable of producing biosurfactant (rhamnolipids) and degrading chlorpyrifos (0·01 g l⁻¹). The partially purified rhamnolipid biosurfactant preparation, having a CMC of 0·2 g l⁻¹, was evaluated for its ability to enhance aqueous phase partitioning and degradation of chlorpyrifos (0·01 g l⁻¹) by ChlD strain. The best degradation efficiency was observed at 0·1 g l⁻¹ supplement of biosurfactant, as validated by GC and HPLC studies.
Conclusion:  The addition of biosurfactant at 0·1 g l⁻¹ resulted in more than 98% degradation of chlorpyrifos when compared to 84% in the absence of biosurfactant after 120-h incubation.
Significance and Impact of the Study:  This first report, to the best of our knowledge, on enhanced degradation of chlorpyrifos in the presence of biosurfactant(s), would help in developing bioremediation protocols to counter accumulation of organophosphates to toxic/carcinogenic levels in environment.     

Ecological management of aquatic plants: effects in lowland streams

Recently, a significant increase in macrophyte growth has been observed in many lowland rivers in Flanders, mainly due to eutrophication and an improvement of the water quality. This growth strongly influences the channel roughness (Manning-n). The first purpose of the project was a better understanding of the complex relationship between biomass development and discharge capacity in lowland rivers. In order to avoid the backing up of water upstream, the whole vegetation body is usually mowed annually. This project also investigated a lighter ecological management of aquatic plants in which only a part of the vegetation is removed in separate and alternating blocks, seeking a compromise between sufficient discharge and conserving large parts of the macrophyte vegetation with all its functions. Beside laboratory experiments, field survey was undertaken in the Grote Caliebeek, a tributary of the Kleine Nete in Flanders, Belgium. The results indicated that the presence of macrophytes in lowland rivers slowed down the waterflow and resulted in a raised water level. The upstream water level followed biomass development at a certain discharge level. The mowing experiments and the field survey indicated that alternating weed cutting patterns can reduce fall in an effective way. This research emphasizes the possibilities of alternating weed cutting patterns in order to deal with water flow problems. In the long term there will be the need for a better understanding of the ecological relationships in the search for a sustainable integrated method of controlling aquatic vegetation.     

狮子山铜尾矿植物对铜的吸收及土壤特的影响

我国铜矿储藏丰富,铜矿开采带来巨大经济利益的同时,也对生态环境造成极大的破坏,这种恶劣的环境严重阻碍了植物的定居,但是自然界物种繁多,总有一些植物能适应这种环境而生存下来.本文通过对狮子山优势植物吸收和积累铜的分析,发现这些植物均能富集较多的铜,在土壤铜含量很高的情况下,依然生长旺盛,没有出现受害症状,成为尾矿上的优势种,并形成了单优群落或多优小群落.这些植物的存在改变了土壤的理化特性,降低了土壤中的重金属的含量,提高了土壤的全N、全P、全K和有机质含量,一定程度上改善了土壤的不良环境,在尾矿的植被恢复和土壤修复中起着非常重要的作用.     

Copper-induced alteration in sucrose partitioning and its relationship to the root growth of two Elsholtzia haichowensis Sun populations

Hydroponic culture was used to comparatively investigate the copper (Cu)-induced alteration to sucrose metabolism and biomass allocation in two Elsholtzia haichowensis Sun populations with one from a Cu-contaminated site (CS) and the other from a non-contaminated site (NCS). Experimental results revealed that biomass allocation preferred roots over shoots in CS population, and shoots over roots in NCS population under Cu exposure. The difference in biomass allocation was correlated with the difference in sucrose partitioning between the two populations. Cu treatment (45 μM) significantly decreased leaf sucrose content and increased root sucrose content in CS population as a result of the increased activities of leaf sucrose synthesis enzymes (sucrose phosphate synthetase and sucrose synthase) and root sucrose cleavage enzyme (vacuolar invertase), which led to increased sucrose transport from leaves to roots. In contrast, higher Cu treatment increased sucrose content in leaves and decreased sucrose content in roots in NCS population as a result of the decreased activities of root sucrose cleavage enzymes (vacuolar and cell wall invertases) that led to less sucrose transport from leaves to roots. These results provide important insights into carbon resource partitioning and biomass allocation strategies in metallophytes and are beneficial for the implementation of phytoremediation techniques.     

Genes involved in copper resistance influence survival of Pseudomonas aeruginosa on copper surfaces

Aims:  To evaluate the killing of Pseudomonas aeruginosa PAO1 on copper cast alloys and the influence of genes on survival on copper containing medium and surfaces.
Methods and Results:  Different strains of P. aeruginosa were inoculated on copper containing medium or different copper cast alloys and the survival rate determined. The survival rates were compared with rates on copper-free medium and stainless steel as control. In addition, the effect of temperature on survival was examined.
Conclusions:  Copper cast alloys had been previously shown to be bactericidal to various bacteria, but the mechanism of copper-mediated killing is still not known. In this report, we demonstrate that P. aeruginosa PAO1 is rapidly killed on different copper cast alloys and that genes involved in conferring copper resistance in copper-containing medium also influenced survival on copper cast alloys. We also show that the rate of killing is influenced by temperature.
Significance and Impact of the Study:  To use copper surfaces more widely as bactericidal agents in various settings, it is important to understand how genes influence survival on these surfaces. Here we show that genes shown to be involved in copper resistance in P. aeruginosa PAO1 can have an impact on the length of survival time on copper cast alloys under certain conditions. This is an important first step for evaluation of future use of copper surfaces as bactericidal agents.