Assessment of the root system of Brassica juncea (L.) czern. and Bidens pilosa L. exposed to lead polluted soils using rhizobox systems

The purpose of this study was to compare the behavior of the root system of one of the most frequently cited species in phytoremediation Indian mustard [Brassica juncea (L.) Czern.] and a representative perennial herb (Bidens pilosa L.) native of Argentina, for different concentrations of lead in soils through chemical and visualization techniques of the rhizosphere. Lead polluted soils from the vicinity of a lead recycling plant in the locality of Bouwer, were used in juxtaposed rhizobox systems planted with seedlings of B. juncea and B. pilosa with homogeneous and heterogeneous soil treatments. Root development, pH changes in the rhizosphere, dry weight biomass, lead content of root and aerial parts and potential extraction of lead by rhizosphere exudates were determined. In both species lead was mainly accumulated in roots. However, although B. juncea accumulated more lead than B. pilosa at elevated concentrations in soils, the latter achieved greater root and aerial development. No changes in the pH of the rhizosphere associated to lead were observed, despite different extractive potentials of lead in the exudates of the species analyzed. Our results indicated that Indian mustard did not behave as a hyperaccumulator in the conditions of the present study.     

Phytoremediation Potential of Plants Growing on the Pb-Contaminated Soil at the Song Tho Pb Mine,Thailand

The contamination of lead (Pb) is one of the main environmental problems on a global scale. This study assessed the potential of native metallophytes growing on the Song Tho Pb mine in Kanchanaburi province, Thailand, by a field survey. Plants and the associated soil samples were collected. Total Pb concentrations were analyzed by a flame atomic absorption spectrophotometer after a microwave-assisted acid digestion. While total Pb concentrations of top soils varied from 4881 to 16,720 mg/kg, those in soil around the roots ranged from 421 to 48,883 mg/kg. A total of 12 species belonging to eight families accumulated Pb concentrations in roots (47–32,633 mg/kg) which were higher than those in shoots (non-detected values – 1489 mg/kg). Bidens pilosa, with Pb accumulation in shoots > 1000 mg/kg and translocation factor (TF) > 1, could be useful in phytoextraction as a hyperaccumulator. Thysanolaena latifolia and Mimosa pudica with bioconcentration factor > 1 and TF < 1 could be useful in phytostabilization as excluders. So far, not many Pb hyperaccumulators are reported. The results from this study proposed a new candidate, B. pilosa, for Pb extraction. The potential use of these three phytoremediators should be further investigated using hydroponic and pot experiments.     

Low Allozymic Variation in the Bidens pilosa L. Complex (Asteraceae)

Bidens alba, B. subalternans, and B. pilosa form a complex group based on their morphological similarities. Bidens pilosa L. and B. subalternans DC. are herbs with a wide distribution in agricultural and disturbed areas. Bidens alba (L.) DC. varies in size from herb to subshrub and has a coastal distribution. Enzyme electrophoresis was used to evaluate genetic diversity in 12 populations of Bidens. All but three loci (Lap-1, Est, and Got) were monomorphic. Est-1 and Got were polymorphic only in B. alba. Lap-1 was polymorphic only in B. pilosa and B. subalternans. The estimates of genetic variability were low for all three taxa and all of the populations studied. Genetic diversity varied from 0.01 to 0.03. Mean genetic identities were high among populations of each species (0.99 for B. alba and 1.00 for B. pilosa and B. subalternans) and among the three species (1.00). Bidens pilosa and B. subalternans could be considered a single species if the taxonomy of the group were based solely on isozyme data.     

不同光照和水分下三叶鬼针草与本地种金盏银盘生长特征的比较研究

为探讨三叶鬼针草(Bidens pilosa)成功入侵机制,利用盆栽试验对不同光照和水分条件下三叶鬼针草与本地种金盏银盘(B.biternata)的生长特征进行了比较研究。结果表明,两物种对光和水的变化均具有较大可塑性,但与金盏银盘相比,在有利环境下三叶鬼针草具有较大的株高、叶面积、生物量;在不利环境下,三叶鬼针草具有较大的比叶面积和叶面积比;除叶面积比和叶生物量比外,三叶鬼针草各生理参数的可塑性指数均高于本地种。这说明三叶鬼针草具有较强的表型可塑性和入侵适应性,这些特性促进了其成功入侵。     

Screen of Chinese Weed Species for Cadmium Tolerance and Accumulation Characteristics

The cadmium (Cd) tolerance and metal-accumulation characteristics of 29 species (18 families) of weed were studied by using outdoor pot-culture experiments. The results of this screening showed that Bidens pilosa and Kalimeris integrifolia (both Asteraceae) expressed some properties that are characteristic of Cd hyperaccumulators. In 10 mg/kg Cd-spiked soil, they accumulated a good deal of Cd in shoots (28 and 25 mg/kg DW, respectively) with high Cd enrichment factors (EFs; concentration in plant/soil). Cd accumulations in shoots were greater than those in roots (translocation factor (TF) >1, concentration in shoot/root) and the shoot biomasses did not decreased significantly compared to the unspiked control. The other weed species showed little accumulation of Cd, Pb, Cu, or Zn. In a concentration-gradient experiment, the Cd accumulation potentials of B. pilosa and K. integrifolia were examined further. Cd concentrations in leaves of B. pilosa growing in soils spiked with 25, 50, and 100 mg/kg Cd were up to 145, 160, and 192 mg/kg, respectively, and the Cd content in stems in the 100 mg/kg Cd-spiked soil was 115 mg/kg, all greater than the 100 mg/kg notional criterion for Cd hyperaccumulation. The Cd EFs and TFs were all greater than 1. The shoot biomasses did not decrease significantly compared to the controls. B. pilosa was thus shown to have some characteristics of a true Cd hyperaccumulator plant.     

鬼针草(Bidens pilosa L.)对镉污染农田的修复潜力

为探究富集植物鬼针草对镉(Cd)污染农田土壤的修复潜力,通过野外调查,原土盆栽试验和田间试验,测定鬼针草及其根系土壤Cd含量,计算鬼针草的富集系数和去除率。结果表明,野外调查中不同铅锌矿区生长的鬼针草叶片中Cd含量最大值为53.3 mg/kg。盆栽试验中,低浓度Cd土壤处理(T1),鬼针草地上部Cd的富集系数为4.70,转运系数1.59,大于1。高浓度Cd土壤处理(T2 13.4 mg/kg),其地上部Cd积累量达到43.1 mg/kg,其地上部Cd富集系数为3.51。鬼针草对Cd表现出稳定的积累特性。田间试验小区中,土壤Cd含量均值为2.66 mg/kg,鬼针草中地上部Cd含量均值为10.9 mg/kg,富集系数为4.16,使用鬼针草修复Cd污染土壤每公顷地种植一茬鬼针草的去除率为4.3%—6.2%。使用富集植物鬼针草修复农田Cd污染具有较好的工程应用前景。     

Dynamics of lead accumulation in mycorrhizal and non-mycorrhizal Norway spruce (Picea abies (L.) Karst.)

Twelve-week-old seedlings of Norway spruce (Picea abies (L.) Karst), non-mycorrhizal or mycorrhizal with Laccaria laccata, Paxillus involutus or Pisolithus tinctorius were exposed to 5 M Pb for either 32 or 42 days in a quartz sand-nutrient solution system. Ultrathin sections of mycorrhizal and non-mycorrhizal short roots were examined by X-ray microanalysis. After 42 days Pb treatment, the Pb content of the cortex cell walls was lower in the non-mycorrhizal short roots and in the P. involutus mycorrhizae than in the mycorrhizae of L. laccata or P. tinctorius. The Pb content of the cell walls of the hyphal mantle was higher in P. involutus than in L. laccata or P. tinctorius. The short term experiment over 32 days showed that the Pb content of the cortex cell walls strongly increased during the first 16 days in the non-mycorrhizal roots and the L. laccata mycorrhizae, whereas it increased more slowly in the P. involutus mycorrhizae. After 32 days Pb treatment, the Pb content in the cortex cell walls in the P. involutus mycorrhizae was similar to that in the non-mycorrhizal roots. P. involutus also decreased Pb translocation from the roots to the stems. Mycorrhizal infection was not affected by Pb but with P. involutus, the amount of extramatrical mycelium was reduced by 50% on day 32 compared to day 16. The extramatrical mycelium of L. laccata was not reduced by Pb. It is concluded that ectomycorrhizal fungi differ in their effect on Pb accumulation in the roots of Norway spruce. The binding capacity of the extramatrical mycelium seems to be an important factor.     

入侵种银胶菊和三叶鬼针草与本地种气体交换特性的比较

以菊科入侵植物银胶菊(Parthenium hysterophorus)和三叶鬼针草(Bidens pilosa)以及与其共生的菊科本地植物小蓟(Cirsium setosum)为对象,比较了3种植物气体交换参数和叶片特性的差异。结果表明,银胶菊和三叶鬼针草的净光合速率(net photosynthetic rate,P_n)、叶绿素含量、比叶面积(specific leaf area,SLA)、叶片单位质量P含量(leaf P content per unit mass,P_(mass))、光合能量利用效率(photosynthetic energy use efficiency,PEUE)和光合氮利用效率(photosynthetic nitrogen use efficiency,PNUE)均显著高于小蓟。植物叶片P_n与水分利用效率(water use efficiency,WUE)、叶片P_(mass)、SLA呈极显著正相关,植物叶片单位质量N含量(leaf P content per unit mass,N_(mass))与叶片SLA、单位质量建成成本(leaf construction cost per unit mass,CC_(mass))、叶绿素含量呈极显著正相关。与本地植物相比,较高的气体交换参数和叶片生化指标有可能是银胶菊和三叶鬼针草成功入侵的原因之一。     

Effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the phytoremediation potential of Catharanthus roseus (L.) in Cu and Pb-contaminated soils

The remediation of heavy metal-contaminated soils has become a critical issue due to toxic effects of these metals on living organisms. The current research was conducted to study the effect of Pseudomonas fluorescens RB4 and Bacillus subtilis 189 on the growth and phytoremediation potential of Catharanthus roseus in Cu- and Pb-contaminated soils. The bacterial strains exhibited significantly higher level of water-extractable Pb and Cu in Pb, Cu, and Cu+Pb-contaminated. The P. fluorescens RB4 inoculated plants, produced 102%, 48%, and 45% higher fresh weight (FW) in soils contaminated with Cu, Pb, and both elements, respectively, as compared to un-inoculated control plants. Similarly, B. subtilis 189 inoculated plants produced 108%, 43%, and 114% more FW in the presence of Cu, Pb, and both elements. The plants co-cultivated with both bacteria exhibited 121%, 102%, and 177% higher FW, in Cu, Pb, and both elements contaminated soils, as compared to respective un-inoculated control. Co-cultivation of P. fluorescens RB4, B. subtilis 189, and P. fluorescens RB4 + B. subtilis 189 resulted in higher accumulation of Cu and Pb in shoots of the C. roseus grown in contaminated soils as compared to un-inoculated control. Bacterial treatments also improved the translocation and metal bioconcentration factors. The growth and phytoextraction capability of C. roseus was improved by inoculation of P. fluorescens RB4 and B. subtilis 189.     

Phytoremediation of lead (Pb) and Arsenic (As) by Melastoma malabathricum L. from Contaminated Soil in Separate Exposure

This study was conducted to investigate the uptake of lead (Pb) and arsenic (As) from contaminated soil using Melastoma malabathricum L. species. The cultivated plants were exposed to As and Pb in separate soils for an observation period of 70 days. From the results of the analysis, M. malabathricum accumulated relatively high range of As concentration in its roots, up to a maximum of 2800 mg/kg. The highest accumulation of As in stems and leaves was 570 mg/kg of plant. For Pb treatment, the highest concentration (13,800 mg/kg) was accumulated in the roots of plants. The maximum accumulation in stems was 880 mg/kg while maximum accumulation in leaves was 2,200 mg/kg. Only small amounts of Pb were translocated from roots to above ground plant parts (TF < 1). However, a wider range of TF values (0.01–23) for As treated plants proved that the translocation of As from root to above ground parts was greater. However, the high capacity of roots to take up Pb and As (BF > 1) is indicative this plants is a good bioaccumulator for these metals. Therefore, phytostabilisation is the mechanism at work in M. malabathricum's uptake of Pb, while phytoextraction is the dominant mechanism with As.     

Ecological comparison between duckweeds in central Italy: The invasive Lemna minuta vs the native L. minor

The American duckweed Lemna minuta shows an invasive behaviour in Europe, causing weed problems in aquatic habitats there. Few studies addressed this species’ ecological requirements for a suitable establishment in a site. In this paper, L. minuta populations were analysed through field surveys so as (1) to define the autoecology of this duckweed as regards the main environmental factors characterizing invaded habitats, and (2) to identify possible overlaps/differences in ecological requirements between the alien L. minuta and the common native L. minor, with which it is often associated and in direct competition. The occurrence/abundance of the two species and environmental data were collected from 41 wetlands in central Italy. Currently, L. minuta is more common and abundant than L. minor in the study-area, despite its recent arrival there (2007). The two species have a partially overlapped autoecology. However, L. minuta differs from L. minor since it occurs in waters which are less alkaline, slightly less warm, and richer in nitrates. It shows tolerance for environmental conditions which are limiting for most of macrophytes, including L. minor, such as high shading and low water oxygenation. This enables L. minuta to increase its invasion potentiality and thus to enlarge its distribution area.     

Influence of an exotic species,Acroptilon repens (L.) DC. on seedling emergence and growth of native grasses

Our objective was to evaluate the effects of an invasive perennial forb, Acroptilon repens (Russian knapweed), on seed emergence and seedling survival of four native grass species that are important in semiarid grasslands of North America. Greenhouse experiments and field studies conducted at three sites in Colorado, USA were used to examine the response by four perennial grasses: Bouteloua gracilis, Koelaria cristata, Sporobolus cryptandrus, and Agropyon smithii to A. repens. In the greenhouse, seeds of each species were sown in pots that contained either live A. repens roots, A. repens litter on the soil surface, or both roots and litter. Field transects were placed inside stands of A. repens with adjacent control transects in the surrounding grass-dominated community. Emergence and initial survival were decreased by the presence of A. repens roots for K. cristata (35%), B. gracilis (31%), and S. cryptandrus (44%) in the greenhouse, and 57, 32, and 36%, respectively, in the field. Root weight was decreased by the presence of A. repens roots for both B. gracilis and K. cristata by more than 55% in the greenhouse. A. smithii survival and growth were unaffected by A. repens in either the greenhouse or the field. These species-specific responses to the presence of A. repens may explain, at least in part, differences in susceptibility and recovery of sites with different native grass species composition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of elemental allelopathy in Acroptilon repens (L.) DC. (Russian Knapweed)

Although Acroptilon repens (L.) DC. (Russian knapweed) is known to concentrate zinc (Zn) in upper soil layers, the question of whether the elevated Zn has an allelopathic effect on restoration species has not been addressed. Experiments were conducted to investigate whether soils collected from within infestations of A. repens (high-Zn) inhibit the germination or growth and development of desirable restoration species, compared to soils collected adjacent to an A. repens infestation (low-Zn). Four bioassay species [Sporobolus airoides (Torrey) Torrey (alkali sacaton), Pseudoroegneria spicata (Pursh) A. Love (bluebunch wheatgrass), Psathyrostachys juncea (Fischer) Nevski (Russian wildrye) and A. repens] were germinated in a growth chamber and grown in a greenhouse in both soils and received treatments for the alleviation of Zn toxicity (P, Fe, Fe-oxide, and soil mixing) to isolate the effects of elevated soil Zn on plant performance. Percent germination, total plant biomass, tiller and stem number, inflorescence number, and tissue metal levels were compared among soil types and treatments for each species. There was no evidence from any of the indicators measured that high-Zn soils reduced plant performance, compared to low-Zn soils. Tissue Zn levels barely approached the lower range of phytotoxic levels established for native grasses. Older plants with longer exposure times may accumulate higher Zn concentrations. S. airoides and A. repens both had higher biomass in the high-Zn soil, most likely due to increased macronutrient (N and P) availability. As the Zn levels in the soils used in this study were much higher than any levels previously reported in soils associated with A. repens, it is unlikely that the elevation of soil Zn by A. repens will hinder germination or growth and development of desirable grasses during establishment.     

Allelopathic interference of sweet potato with cogongrass and relevant species

Cogongrass (Imperata cylindria) is an invasive weed and harmful to ecological systems and agricultural production in many countries. It was found that plant extracts and root exudates of sweet potato (Ipomoea batatas) exhibit allelopathic potential and inhibit the growth of cogongrass to a greater extent than either barnyardgrass (Echinochloa crus-galli), Indian goose-grass (Eleushine indica), or lettuce (Lactuca sativa) in bioassays. Greenhouse trials indicated that sweet potato soil reduced the emergence of the noxious weed by 50 %, yet exhibited either weaker inhibition or the promotion of barnyardgrass, Bidens (Bidens pilosa), and Leucaena (Leucaena leucocephala), while the desired growth of upland rice (Oryza sativa) was not affected. In cogongrass fields, the incorporation of 1–2 tons aboveground parts and cultivation of sweet potato provided 80–85 % weed control. On the other hand, the reduction of congograss in fields may be offset by the alternate invasion of B. pilosa which multiplied its biomass by 2–6 times with sweet potato amended soils. The findings of this study indicate that sweet potato is an effective crop in the biologic management of the invasive cogongrass in agricultural fields, thus the interactive mechanism between sweet potato and the invasive weed demands further investigation. Ecologically, this study highlights the specificity of allelopathic interactions between cogongrass and sweet potato that is helpful to minimize the disturbance from infestation of this invasive weed against native species and crops.     

Needle nematodes (Longidorus spp.) and stubby-root nematodes (Trichodorus spp.) harmful to sugar beet and other field crops in England

Longidorus attenuatus produces galls at the tips of roots of field crops, including sugar beet, growing in alkaline, sandy soils in eastern England. L. elongatus produces similar, but often larger, galls on the roots of sugar beet and other crops in sandy soils in the W. Midlands and in Fen peats. Trichodorus spp. cause ‘stubby root’ of sugar beet and can feed on many field crops. Seven species of Trichodorus were found in sandy soils in eastern England. L. attenuatus, L. elongatus and Trichodorus spp. aggregate around roots and stunt sugar beet and other crop plants. L. attenuatus is commoner below plough depth than in the topsoil, whereas T. cylindricus, T. pachy-dermus and T. anemones are more abundant in the topsoil. These nematodes cause some forms of ‘Docking disorder’.     

Phytoremediation of lead by a wild,non-edible Pb accumulator Coronopus didymus (L.) Brassicaceae

Coronopus didymus was examined in terms of its ability to remediate Pb-contaminated soils. Pot experiments were conducted for 4 and 6 weeks to compare the growth, biomass, photosynthetic efficiency, lead (Pb) uptake, and accumulation by C. didymus plants. The plants grew well having no visible toxic symptoms and 100% survivability, exposed to different Pb-spiked soils 100, 350, 1500, and 2500 mg kg^?1, supplied as lead nitrate. After 4 weeks, root and shoot concentrations reached 1652 and 502 mg Pb kg^?1 DW, while after 6 weeks they increased up to 3091 and 527 mg Pb kg^?1 DW, respectively, at highest Pb concentration. As compared to the 4 week experiments, the plant growth and biomass yield were higher after 6 weeks of Pb exposure. However, the chlorophyll content of leaves decreased but only a slight decline in photosynthetic efficiency was observed on exposure to Pb at both 4 and 6 weeks. The Pb accumulation was higher in roots than in the shoots. The bioconcentration factor of Pb was > 1 in all the plant samples, but the translocation factor was < 1. This suggested C. didymus as a good candidate for phytoremediation of Pb-contaminated soils and can be used for future remediation purposes.     

A field experiment on the use of Pistacia lentiscus L. and Scrophularia canina L. subsp. bicolor (Sibth. et Sm.) Greuter for the phytoremediation of abandoned mining areas

Abstract

A two-year study has been conducted in an abandoned Pb/Zn mining site, with the aim of investigating the feasibility of phytoremediation using two native Mediterranean plants (Pistacia lentiscus and Scrophularia bicolor) and of assessing the performance of amendments able to reduce the toxic effects of heavy metals. The amendments used were compost, chemical fertilizer, and zeolites, used singly or in combination. Depending on the amendments applied, the two species showed different mortality rates in the different plots, but all produced an increase in P. lentiscus survival, while S. bicolor survival improved only when amended with zeolite or zeolite + fertilizer. Scrophularia bicolor proved to be a more efficient accumulator than P. lentiscus, especially for Pb uptake. Pistacia lentiscus accumulated metals mostly in the roots. The effect of amendments was to generally reduce the bioavailable metal fraction, especially lead, in the plots amended with compost. Pistacia lentiscus proved to be the most suitable species for phytostabilization and environmental restoration, both for its resistance to metals and high phytomass production. The experiments demonstrate that the use of compost not only encourages this kind of revegetation in degraded areas, but is also an economical option that uses a by-product of solid municipal waste treatment.     

Origin and taxonomic affinities of Thelypteris (subgen. Stegnogramma) burksiorum (Thelypteridaceae)

This paper examines the ecology, frond and spore morphology, gametophytes, and molecular biology ofThelypteris burksiorum to reveal its taxonomic affinities and phytogeographic origin. The species is endemic to Winston County in northern Alabama (U.S.A.) and only occurs in cave-like rockhouse habitats. A related species,T. pilosa, is widespread in central and southern Mexico, Guatemala, and Honduras.Thelypteris pilosa is extremely variable and our data suggest that current recognition of the varietiesmajor andpilosa is not warranted.Thelypteris pilosa is clearly closely related and likely sister toT. burksiorum. Thelypteris burksiorum exhibits the unusual production of gametophytic propagules. This, in combination with current levels of genetic diversity and reproductive biology, suggests thatT. burksiorum is an ancient Tertiary relict and not an example of recent long distance dispersal. Selection in rockhouse habitats has driven species away from their normal life cycle to partial or complete reliance on the gametophyte generation. The combination of a reduced yet fertile sporophyte and a gametophyte that may rely on gametophytic proliferation placesT. burksiorum in an intermediate evolutionary position relative to other rockhouse pteridophytes.     

印加孔雀草入侵生态风险评估及其管理措施

【目的】印加孔雀草为菊科一年生草本植物,原产南美洲,现已在我国多个地区发现,局部呈现生态危害。分析印加孔雀草生态适应性特点,可以有针对地提出其风险指标体系和判断标准,确定其危险级别。【方法】对印加孔雀草的分布、危害情况及生物学特性进行调查,定性分析其生态适应性特点,定量分析评估其生态风险,确定其危险级别。【结果】根据风险指标体系准则层的赋值,其中入侵性R_1为83,适应性R_2为88,扩散性R_3为65,危害性R_4为84,计算得出印加孔雀草风险值(R)=8061,属于具有危害性和侵入性的物种。【结论】印加孔雀草为具有危害性和侵入性的物种,应严格禁止引入。由于该植物已经传入我国,应采取必要的应急措施,开展检疫、监测和灭除,防止其传入其他还未发生的地区。     

Heavy metal accumulation and distribution in forest understory herb species of Carpathian beech ecosystems

Abstract

This study addresses the issue of heavy metal (HM) accumulation and distribution for three different plant species, Carex pilosa, Dentaria bulbifera, Galium odoratum, in Carpathian beech ecosystems. Data are presented on HM concentrations in forest understory vegetation and a preliminary insight into different HM allocation patterns is provided. Bioaccumulation factors (BCFs) and shoot/root ratios differed considerably among the species and between polluted and unpolluted regions. HMs were accumulated in forest plants as follows: Cu > Zn > Cd >Pb in unpolluted areas and Zn> Cd > Cu >Pb in polluted areas. Zn was preferentially distributed to roots and Cu to shoots. The distribution of Cd and Pb in different plant parts was specific in terms of the species-dependence. Cd and Pb levels in Carex pilosaand Galium odoratumwere more strictly controlled in the transfer zone of root-shoot, compared to Dentaria bulbifera.The highest BCFs were found in Carex pilosafor Cu (5.9) and in Dentaria bulbiferawas found the highest shoot/root ratio for Cd (3.1).