EuroBionet: a pan-European biomonitoring network for urban air quality assessment

EuroBionet, the 'European Network for the Assessment of Air Quality by the Use of Bioindicator Plants', is an EU-funded cooperative project currently consisting of public authorities and scientific institutes from 12 cities in 8 countries. In 2000, the bioindicator plants tobacco (Nicotiana tabacum Bel W3), poplar (Populus nigra 'Brandaris'), spiderwort (Tradescantia sp. clone 4430), Italian rye grass (Lolium multiflorum italicum) and curly kale (Brassica oleracea acephala) were exposed to ambient air at 90 monitoring sites according to standardised methods. Visible injuries and growth parameters were assessed and the accumulation of toxic substances in leaves determined. The exposure of tobacco resulted in a gradient with low levels of ozone-induced foliar injury in N and NW Europe, and medium to high values in the southern and central regions. The results of heavy metal and sulphur analyses in rye grass samples generally showed low to very low sulphur and low to medium heavy metal concentrations in leaves. In some cities, however, local hot spots of heavy metal contamination were detected. Analyses of the PAH contents in curly kale leaves gave low to medium values, with locally elevated levels at traffic-exposed sites.     

外源钙对镉胁迫下美洲黑杨生长和生理特性的影响

研究外源钙(calcium,Ca)对镉(cadmium,Cd)胁迫下雌雄株美洲黑杨的生长和生理影响,探讨雌雄异株植物对Cd胁迫的响应差异,有助于了解外源钙提高植物Cd抗性的机制,可为土壤重金属污染背景下植物修复提供理论依据.采用大棚盆栽试验,研究了施加外源钙(2 g·kg-1)对土壤Cd(50 mg·kg-1 和 100 mg·kg-1)胁迫下美洲黑杨雌、雄幼苗生长、抗氧化酶活性、光合气体交换参数及叶绿素荧光参数等生理指标的响应差异.结果显示,(1)外源钙显著提高Cd胁迫下美洲黑杨雌雄植株的超氧化物歧化酶(superoxide dismutase,SOD)活性,降低过氧化氢(hydrogen peroxide,H2O2)含量,增强雄株的还原型谷胱甘肽(reduced glutathione,GSH)含量,其中,100 mg·kg-1 Cd浓度下施加外源钙显著提高雌株的GSH含量.此外,在50 mg·kg-1 Cd胁迫下,施加外源钙显著提高雌雄植株的过氧化物酶(peroxidase,POD)活性和雄株的过氧化氢酶(catalase,CAT)活性,使丙二醛含量(malondialdehyde,MDA)下降,说明外源钙能有效缓解Cd对美洲黑杨雌雄植株抗氧化酶系统的伤害;(2)50 mg·kg-1 Cd胁迫下施加外源钙显著提高美洲黑杨雌雄株的PS Ⅱ最大光化学效率(Fv/Fm),降低胞间二氧化碳浓度(Ci),雄株气孔导度(Gs)显著上升,雌株的蒸腾速率(Tr)显著提高,说明外源钙能增强植株叶片对光的捕获能力,有效缓解Cd对美洲黑杨雌雄植株光合结构的伤害;(3)与单独Cd处理相比,钙能够抑制雌雄美洲黑杨根部对Cd的吸收,最高可使根系Cd含量降低19.7％,提高Cd耐受性.综上所述,外源钙能促进光合作用,减轻氧化损伤,增强美洲黑杨幼苗对Cd胁迫的抗性;在施钙条件下,与雌株相比,雄株的抗氧化性较高,表现出较好的抗逆性.     

Persistence of methyl <Emphasis Type="Italic">tertiary</Emphasis> butyl ether (MTBE) against metabolism by Danish vegetation

BACKGROUND: Methyl tertiary butyl ether (MTBE) is the second most highly produced industrial chemical in the US and a frequent groundwater pollutant. At the same time, MTBE is quite persistent to biotic and abiotic decomposition. The goal of this study was to find plant species that could degrade MTBE and might be used in phytoremediation. METHODS: Excised roots and leaves (0.3 g) from more than 24 Danish plant species out of 15 families were kept in glass vessels with 25 ml spiked aqueous solution for 2 to 4 days. MTBE concentrations were 1 to 5 mg/L. Samples were taken directly from the solution with a needle and injected to a purge and trap unit. MTBE and the main metabolite, TBA, were measured by GC/FID. RESULTS AND DISCUSSION: Solutions with roots of poplar (Populus robusta) and a willow hybrid (Salix viminalis x schwerinii) produced TBA in trace amounts, probably stemming from bacteria. Significant MTBE reduction (> 10%) was not observed in any of the tests. Leaves from none of the species (trees, grasses and herbs) reduced the concentration of MTBE in the solution and no TBA, nor any other known metabolite of MTBE, was detected. CONCLUSION: It was not possible to find plants capable of efficiently degrading MTBE. This gives rise to the conclusion that plants probably cannot degrade MTBE at all, or only very slowly. RECOMMENDATIONS AND OUTLOOK: For phytoremediation projects, this has, as consequence, that the volatilization by plants (except with genetically engineered plants) is the only relevant removal process for MTBE. For risk assessment of MTBE, degradation by the plant empire is not a relevant sink process.     

Cd and Zn Concentration in Hybrid Poplar Foliage and Leaf Beetles Grown on Polluted Sediment-Derived Soils

Foliar Cd and Zn concentrations of hybrid poplars commonlyplanted on sediment-derived soils were assessed in field circumstances. Selected sites covered a range of soil types andplantation characteristics. Reference data for foliar concentrations were established from samples taken in a tree-nursery. Even in the reference situation a large variationin foliar Cd and Zn concentrations was observed, with relative standard deviations in the order of 15%. Foliar concentrations of Cd and Zn in poplars growing on sediment-derived soils increased during the growing season. The accumulation rate was markedly higher on polluted sediment-derived soils than in thereference situation. Poplars grown on polluted sedimentderived soils showed elevated and deviating foliar Cd and Znconcentrations (>7.5 mg Cd kg^-1 DW and 320 mg Zn kg^-1 DW). A thin unpolluted covering layer did not influence foliarconcentrations. Regardless of site characteristics, poplarage, species or clone, a significant positive relation wasfound between soil and foliar concentration for Zn and to alesser extent for Cd. Bioconcentration factors for Cd and Znwere higher than one in baseline situations, but mostly lowerthan one on polluted sediment-derived soils. Cd:Zn ratio wason the average twice as high as in the soil. Leaf beetlesshowed normal body concentrations for Zn, but higher Cdconcentrations than in reference situations. BCFs were lowerthan one on sediment-derived soils. Foliar results indicateda possible threat in long-term habitat development of poplarplantations. This conclusion was confirmed by the significanthigher Cd concentrations in leaf beetles grown on poplarswith deviant foliar concentrations. However, litterdecomposition rates were generally evaluated as normal.     

Sodium and chloride accumulation in leaf, woody, and root tissue of Populus after irrigation with landfill leachate

The response of Populus to irrigation sources containing elevated levels of sodium (Na(+)) and chloride (Cl(-)) is poorly understood. We irrigated eight Populus clones with fertilized well water (control) (N, P, K) or municipal solid waste landfill leachate weekly during 2005 and 2006 in Rhinelander, Wisconsin, USA (45.6 degrees N, 89.4 degrees W). During August 2006, we tested for differences in total Na(+) and Cl(-) concentration in preplanting and harvest soils, and in leaf, woody (stems+branches), and root tissue. The leachate-irrigated soils at harvest had the greatest Na(+) and Cl(-) levels. Genotypes exhibited elevated total tree Cl(-) concentration and increased biomass (clones NC14104, NM2, NM6), elevated Cl(-) and decreased biomass (NC14018, NC14106, DM115), or mid levels of Cl(-) and biomass (NC13460, DN5). Leachate tissue concentrations were 17 (Na(+)) and four (Cl(-)) times greater than water. Sodium and Cl(-) levels were greatest in roots and leaves, respectively.     

Vole response to unintentional changes in the chemistry of GM poplars

Summary.  There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available. However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments. The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees.