Role of arbuscular mycorrhizal fungi in lead translocation from Bidens pilosa L. plants to soil.

Bidens pilosa frequently forms a symbiotic association with arbuscular mycorrhizal fungi (AMF). This plant species can grow in Pb-polluted soils, accumulating Pb in its tissues. The aims of the study were to determine whether Pb accumulated in the tissues of B. pilosa can be transferred to the soil through AMF and to compare the role of AMF communities that have a history of exposure to the contaminant with those that have never been exposed. The experiment combined plants with and without Pb accumulated in their tissues, and inoculated with AMF collected from the rhizosphere of B. pilosa in soils contaminated and not contaminated with Pb. The results showed that AMF participate in the removal of Pb that had entered the plant and release it into the soil, as evidenced by the presence of Pb in the AMF spores and in the glomalin produced by AMF. We propose that Pb accumulation in AMF spores would be a protection mechanism that interrupts Pb uptake by the plant; however, that mechanism would not be fully exploited in detoxification, whereas the production of Pb-enriched glomalin could be an important detoxification mechanism to eliminate Pb already taken up by plants. AMF with a history of Pb exposure achieved only higher rates of root colonization, while AMF without previous exposure showed higher Pb concentration in the spores and higher glomalin production, and successfully removed Pb from both the roots and aboveground parts of the plant. The use of AMF communities not adapted to Pb may be a more effective option for microbe-mediated phytoremediation methods in which detoxification mechanisms are desirable.

Effects of probiotic and Bidens pilosa on the performance and gut health of chicken during induced Eimeria tenella infection.

AIM: In this study, we have examined the individual and combined protective mechanism of probiotic and Bidens pilosa on the performance and gut health of chickens during Eimeria tenella infection over a 29-day experimental trial. METHODS AND RESULTS: A total of one hundred and fifty 1-day-old chickens were equally distributed into five treatment groups with three biological replicates: two groups were allocated as control groups (control group untreated unchallenged, CG and control positive untreated challenged, CPG) and three groups were fed diets with probiotic (PG), B. pilosa (BPG) and probiotic + B. pilosa (PG + BPG) and challenged with E. tenella. Birds of all groups were assessed for pre and post-infection body weights, oocysts shedding, caecal lesion scores and mRNA expression levels of apoptosis related proteins (Bcl-2, Bax and caspase-3), antioxidant enzymes (CAT and SOD 1), pro-inflammatory cytokines (IL-6 and IL-8) and tight junction proteins (CLDN 1 and ZO 1). Our results revealed that during infection (day 21-29), E. tenella challenged chickens significantly decreased the body weight compared with uninfected control chickens; however, there was no significant effect on body weight of chickens fed with probiotic, B. pilosa and probiotic + B. pilosa was observed. Eimeria tenella challenged untreated birds increased (P < 0·05) oocysts shedding, destructive ratio of caeca and mortality as compared to treated challenged birds. CPG group up-regulated the mRNA expression levels of anti-apoptosis protein Bcl-2 while down-regulated the pro-apoptosis protein Bax relative to PG, BPG and PG + BPG groups. Moreover chickens fed probiotic, B. pilosa and probiotic + B. pilosa diets enhanced the activities of antioxidant enzymes, pro-inflammatory cytokines and tight junction proteins with the comparison of control positive untreated challenged chickens. CONCLUSION: These findings elaborated that feed supplementation of probiotic and B. pilosa (individually or in combination) appeared to be effective in inhibiting the occurrence of disease and decreasing the severity of Eimeria infection in chickens. SIGNIFICANCE AND IMPACT OF THE STUDY: This study explained the underlying anti-coccidial mechanism in which probiotic and B. pilosa (individually and/or in combination) improve the performance of chicken and protect against gut inflammatory responses caused by E. tenella.

Effects of intercropping with Bidens species plants on the growth and cadmium accumulation of Ziziphus acidojujuba seedlings.

To study the effects of intercropping with accumulator plants on heavy metal accumulation of fruit trees, plants of three Bidens species (Bidens pilosa, Bidens biternata, and Bidens parviflora) were intercropped with Ziziphus acidojujuba seedlings under cadmium (Cd)-contaminated conditions (5 mg kg-1). Intercropping with Bidens species increased the biomass and chlorophyll b content of Z. acidojujuba seedlings compared with monoculture, but decreased their carotenoid content. Intercropping with Bidens species also improved the activity of superoxide dismutase, peroxidase, and catalase in Z. acidojujuba seedlings compared with monoculture. Intercropping with Bidens species decreased the Cd content in the roots of Z. acidojujuba seedlings compared with monoculture. Conversely, when intercropped with B. pilosa, B. biternata, and B. parviflora, the Cd content in the shoots of Z. acidojujuba seedlings increased by 62.18%, 60.10%, and 62.18%, respectively, compared with that of those monocultured. When intercropped with Z. acidojujuba seedlings, the Cd accumulation amount of three Bidens species plants were ranked B. parviflora > B. biternata > B. pilosa. Therefore, intercropping with plants of three Bidens species is not suitable for Cd-contaminated jujube orchards.

Effects of co-cropping Bidens pilosa (L.) and Tagetes minuta (L.) on bioaccumulation of Pb in Lactuca sativa (L.) growing in polluted agricultural soils.

Polluted agricultural soils are a serious problem for food safety, with phytoremediation being the most favorable alternative from the environmental perspective. However, this methodology is generally time-consuming and requires the cessation of agriculture. Therefore, the purpose of this study was to evaluate two potential phytoextractor plants (the native species Bidens pilosa and Tagetes minuta) co-cropped with lettuce growing on agricultural lead-polluted soils. The concentrations of Pb, as well as of other metals, were investigated in the phytoextractors, crop species, and in soils, with the potential risk to the health of consumers being estimated. The soil parameters pH, EC, organic matter percentage and bioavailable lead showed a direct relationship with the accumulation of Pb in roots. In addition, the concentration of Pb in roots of native species was closely related to Fe (B. pilosa, r = 0.81; T. minuta r = 0.75), Cu (T. minuta, r = 0.93), Mn (B. pilosa, r = 0.89) and Zn (B. pilosa, r = 0.91; T. minuta, r = 0.91). Our results indicate that the interaction between rhizospheres increased the phytoextraction of lead, which was accompanied by an increase in the biomass of the phytoextractor species. However, the consumption of lettuce still revealed a toxicological risk from Pb in all treatments.

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.

Studies on bioactivity and secondary metabolites of crude extracts of Bidens pilosa L. (Asteraceae): A medicinal plant used in the Transkei region of South Africa.

Whole plant-parts of Bidens pilosa were powdered and extracted in concentrated hexane, acetone, ethanol, methanol and water. The extracts were tested for antimicrobial activity against Escherichia coli (25922), Bacillus subtilis (ATCC 6051), Enterococcus faecalis (51299) Staphylococcus aureus (ATCC 29213) and Pseudomonas aeruginosa (ATCC127853), using standard microbiological techniques. Active crude extracts were macerated in concentrated methanol and tested for secondary metabolites including tannins, saponins, alkaloids, cardiac glycosides, anthraquinones, steroids and flavonoids using standard phytochemical procedures. Hexane and methanol extracts demonstrated similar activity producing 8-17 mm and 11-18 mm inhibition zone-diameter ranges respectively. Further analysis for minimum inhibitory concentrations (MIC(50)) recorded 1.25-20mg/mL and 2.5-20mg/mL for hexane and methanol extracts respectively. The highest zones of inhibition diameters (22-36mm) and lowest MIC(50) values (0.0002-0.0006mg/mL) were recorded for Gentamicin, the positive control. Minimum bactericidal concentration (MBC) ranges were between 10-80mg/mL and 0.001-0.005mg/mL for extracts and control antibiotic respectively. With the exception of anthraquinones, the plant crude extracts tested positive for all secondary metabolites analyzed. These results provide scientific basis for the use of B. pilosa in South African traditional medicine. The antibacterial activity reported herein may be attributed to one or more of the 6 secondary metabolites detected in the plant crude extracts.

The role of pentacyclic triterpenoids in the allelopathic effects of Alstonia scholaris.

Alstonia scholaris is a tropical evergreen tree native to South and Southeast Asia. Alstonia forests frequently lack understory species. However, potential mechanisms-particularly the allelochemicals involved-remain unclear. In the present study, we identified allelochemicals of A. scholaris, and clarified the role of allelopathic substances from A. scholaris in interactions with neighboring plants. We showed that the leaves, litter, and soil from A. scholaris inhibited growth of Bidens pilosa-a weed found growing abundantly near A. scholaris forests. The allelochemicals were identified as pentacyclic triterpenoids, including betulinic acid, oleanolic acid, and ursolic acid by using (1)H and (13)C-NMR spectroscopy. The half-maximal inhibitory concentration (IC50) for radicle growth of B. pilosa and Lactuca sativa ranged from 78.8 µM to 735.2 µM, and ursolic acid inhibited seed germination of B. pilosa. The triterpenoid concentrations in the leaves, litter, and soil were quantified with liquid chromatography-electrospray ionization/tandem mass spectrometry. Ursolic acid was present in forest soil at a concentration of 3,095 µg/g, i.e., exceeding the IC50. In the field, ursolic acid accumulated abundantly in the soil in A. scholaris forests, and suppressed weed growth during summer and winter. Our results indicate that A. scholaris pentacyclic triterpenoids influence the growth of neighboring weeds by inhibiting seed germination, radicle growth, and functioning of photosystem II.

The genomes of Dahlia pinnata, Cosmos bipinnatus, and Bidens alba in tribe Coreopsideae provide insights into polyploid evolution and inulin biosynthesis.

BACKGROUND: The Coreopsideae tribe, a subset of the Asteraceae family, encompasses economically vital genera like Dahlia, Cosmos, and Bidens, which are widely employed in medicine, horticulture, ecology, and food applications. Nevertheless, the lack of reference genomes hinders evolutionary and biological investigations in this tribe. RESULTS: Here, we present 3 haplotype-resolved chromosome-level reference genomes of the tribe Coreopsideae, including 2 popular flowering plants (Dahlia pinnata and Cosmos bipinnatus) and 1 invasive weed plant (Bidens alba), with assembled genome sizes 3.93 G, 1.02 G, and 1.87 G, respectively. We found that Gypsy transposable elements contribute mostly to the larger genome size of D. pinnata, and multiple chromosome rearrangements have occurred in tribe Coreopsideae. Besides the shared whole-genome duplication (WGD-2) in the Heliantheae alliance, our analyses showed that D. pinnata and B. alba each underwent an independent recent WGD-3 event: in D. pinnata, it is more likely to be a self-WGD, while in B. alba, it is from the hybridization of 2 ancestor species. Further, we identified key genes in the inulin metabolic pathway and found that the pseudogenization of 1-FEH1 and 1-FEH2 genes in D. pinnata and the deletion of 3 key residues of 1-FFT proteins in C. bipinnatus and B. alba may probably explain why D. pinnata produces much more inulin than the other 2 plants. CONCLUSIONS: Collectively, the genomic resources for the Coreopsideae tribe will promote phylogenomics in Asteraceae plants, facilitate ornamental molecular breeding improvements and inulin production, and help prevent invasive weeds.

Polyaspartic acid enhances the Cd phytoextraction efficiency of Bidens pilosa by remolding the rhizospheric environment and reprogramming plant metabolism.

The green soil chelator polyaspartic acid (PASP) can enhance heavy metal phytoextraction efficiency, but the potential mechanisms are not clearly understood from the whole soil-plant system. In this study, we explored the effects and potential mechanisms of PASP addition in soils on plant growth and cadmium (Cd) uptake in the Cd hyperaccumulator Bidens pilosa by analysing variations in chemical elements, rhizospheric microbial community, and plant metabolomics. The results showed that PASP significantly promoted the biomass yield and Cd concentration in B. pilosa, leading to an increase in the total accumulated Cd by 46.4% and 76.4% in shoots and 124.7% and 197.3% in roots under 3 and 6 mg kg-1 PASP addition, respectively. The improved soil-available nutrients and enriched plant growth-promoting rhizobacteria (e.g., Sphingopyxis, Sphingomonas, Cupriavidus, Achromobacter, Nocardioides, and Rhizobium) were probably responsible for the enhanced plant growth after PASP addition. The increase in Cd uptake by plants could be due to the improved rhizosphere-available Cd, which was directly activated by PASP and affected by the induced rhizobacteria involved in immobilizing/mobilizing Cd (e.g., Sphingomonas, Cupriavidus, Achromobacter, and Rhizobium). Notably, PASP and/or these potassium (K)-solubilizing rhizobacteria (i.e., Sphingomonas, Cupriavidus, and Rhizobium) highly activated rhizosphere-available K to enhance plant growth and Cd uptake in B. pilosa. Plant physiological and metabolomic results indicated that multiple processes involving antioxidant enzymes, amino acids, organic acids, and lipids contributed to Cd detoxification in B. pilosa. This study provides novel insights into understanding how soil chelators drive heavy metal transfer in soil-plant systems.

Season variations for metallic elements compositions study in plant Bidens pilosa L. var. radiate Sch. in central Taiwan.

The possibility of using Bidens pilosa L. var. radiate Sch leaves as environmental indicators of metallic element pollution has been investigated. Samples were analyzed with respect to the following pollutants: Zn, Mn, Cu, Ni, Pb, Cd, Cr, Fe, Ca, and Mg by using inductively coupled plasma atomic emission spectrometry. The results obtained on the metallic elements had the following average composition order: Ca > Mg > Fe, Mn > Zn > Cu > Ni > Pb > Cr > Cd for plant B. pilosa L. var. radiate Sch. at HK sampling site. In addition, the metallic elements had the following average composition order: Ca > Mg > Fe > Mn, Zn > Cu > Ni > Pb > Cr > Cd for plant B. pilosa L. var. radiate Sch. at TMP sampling site. Finally, the metallic elements had the following average composition order: Ca > Mg > Fe > Zn > Mn > Cu > Pb > Ni > Cr > Cd for plant B. pilosa L. var. radiate Sch. at LH sampling site. The seasonal average composition for metallic elements Mg, Fe, and Pb were ranked highest at HK sampling site in winter. In addition, seasonal average composition for metallic elements Mn, Zn, and Cd were ranked highest at TMP sampling site in winter. Finally, seasonal average composition for metallic elements Mg, Fe, and Cu were ranked highest at LH sampling site in spring.

Cadmium tolerance and accumulation characteristics of Bidens pilosa L. as a potential Cd-hyperaccumulator.

Recently, researchers are becoming interested in using hyperaccumulators for decontamination of heavy metal polluted soils, whereas few species that hyperaccumulate cadmium (Cd) has been identified in the plant kingdom. In this study, the physiological mechanisms at the seedling stage and growth responses and Cd uptake and accumulation at flowering and mature stages of Bidens pilosa L. under Cd treatments were investigated. At the seedling stage, when soil Cd was lower than 16mgkg(-1), the plant did not show obvious symptom of phytoxicity, and the alterations of chlorophyll (CHL), superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), and soluble protein (SP) did not have significant differences when compared with the control. At the flowering and mature stages, under low Cd treatments (

Effects of mutual grafting on cadmium accumulation characteristics of first post-generations of Bidens pilosa L. and Galinsoga parviflora Cav.

We studied the effects of mutual grafting on cadmium (Cd) accumulation characteristics on the first post-generations of the Cd-hyperaccumulator plants Bidens pilosa L. and Galinsoga parviflora Cav. The seeds from scions and rootstocks of B. pilosa and G. parviflora were collected and planted in Cd-contaminated soil in pot and field experiments. In the pot experiment, rootstock treatment increased the shoot biomass of B. pilosa post-grafting generations, compared with ungrafted B. pilosa, but decreased the Cd content in shoots and Cd extraction by shoots of post-grafting generations; scion treatment decreased or had no significant effect. Mutual grafting resulted in no significant differences to the photosynthetic pigment contents in B. pilosa post-grafting generations. Compared with ungrafted G. parviflora, scion treatment increased the shoot biomass, photosynthetic pigment content, and Cd extraction by shoots of G. parviflora post-grafting generations, but rootstock treatment did not lead to significant differences. Mutual grafting resulted in no significant differences to the Cd contents in shoots of G. parviflora post-grafting generations. In the field experiment, only rootstock treatment increased the shoot biomass of B. pilosa post-grafting generations, and only scion treatment increased the shoot biomass and the Cd extraction by shoots of G. parviflora post-grafting generations. Therefore, mutual grafting of scions may enhance the phytoremediation ability of G. parviflora first post-grafting generations.

Nitrogen transfer from one plant to another depends on plant biomass production between conspecific and heterospecific species via a common arbuscular mycorrhizal network.

The formation of a common mycorrhizal network (CMN) between roots of different plant species enables nutrient transfers from one plant to another and their coexistence. However, almost all studies on nutrient transfers between CMN-connected plants have separately, but not simultaneously, been demonstrated under the same experimentation. Both conspecific and heterospecific seedlings of Cinnamomum camphora, Bidens pilosa, and Broussonetia papyrifera native to a karst habitat in southwest China were concurrently grown in a growth microcosm that had seven hollowed compartments (six around one in the center) being covered by 35.0-µm and/or 0.45-µm nylon mesh. The Ci. camphora in the central compartment was supplied with or without Glomus etunicatum and 15N to track N transfers between CMN-connected conspecific and heterospecific seedlings. The results showed as follows: significant greater nitrogen accumulations, biomass productions, 15N content, % Ntransfer, and the Ntransfer amount between receiver plant species ranked as Br. papyrifera≈Bi. pilosa > Ci. camphora under both M+ and M-, and as under M+ than under M- for Ci. camphora but not for both Bi. Pilosa and Br. papyrifera; the CMN transferred more nitrogen (15N content, % Ntransfer, and Ntransfer amount) from the donor Ci. camphora to the heterospecific Br. papyrifera and Bi. pilosa, with a lower percentage of nitrogen derived from transfer (%NDFT). These findings suggest that the CMN may potentially regulate the nitrogen transfer from a donor plant to individual heterospecific receiver plants, where the ratio of nitrogen derived from transfer depends on the biomass strength of the individual plants.

Effects of PASP/NTA and TS on the phytoremediation of pyrene-nickel contaminated soil by Bidens pilosa L.

Bidens pilosa L. (B. pilosa) is considered as an effective phytoremediation plant. In this study, polyaspartic acid (PASP), aminotriacetic acid (NTA) and tea saponin (TS) was combined with B. pilosa. to strengthen the phytoremediation efficiency. The removal rate of pyrene reached 95.8% with B. pilosa alone. The release of Ni in NTA and NTA-TS treatments was 20-30 times than untreated contaminant soil. The Ni concentration in roots of B. pilosa increased by 63.1% and 58.6% in PASP and PASP-TS treatments, respectively. The Ni concentration in leaves of B. pilosa increased by 55.9% and 186% in NTA and NTA-TS treatments, respectively. The growth of B. pilosa was significantly promoted in PASP and PASP-TS treatments. PASP, NTA and TS significantly promoted soil microbial activities. The results showed that B. pilosa was beneficial to pyrene removal. PASP and NTA had positive effects on absorption of Ni by B. pilosa.

A Pyrus communis gene for p-hydroxystyrene biosynthesis, has a role in defense against the pear psylla Cacopsylla biden.

Styrene analogs are known to be naturally synthesized in the leaves of pears and in other plant species, including several trees in the Styracaceae family. Styrene analogs are potential contributors to the aroma of wine, perfumes, pharmaceuticals, and other fermented foods and beverages. In addition, styrene analogs perform important ecological functions such as insecticidal and antifeedant activities against insects. We showed here that exogenous applications of styrene and p-hydroxystyrene caused a dramatic reduction the number of eggs laid by psylla and of subsequent nymph survival. Despite their importance specific reactions that lead to the biosynthesis of the styrene analogs in pear are unknown. To identify genes involved in the synthesis of these metabolites, existing genome databases of the Rosaceae were screened for pear genes with significant sequence similarity to bacterial phenolic acid decarboxylase. Herein described are the isolation and characterization of a pear phenolic acid decarboxylase, designated PyPAD1, which catalyzed the decarboxylation of p-coumaric acid and ferulic acid to p-hydroxystyrene and 3-methoxy-4-hydroxystyrene respectively. Its apparent Km values for p-coumaric acid and ferulic acid were 34.42 and 84.64 µM, respectively. The PyPAD1 preferred p-coumaric acid to ferulic acid as a substrate by a factor of 2.4 when comparing catalytic efficiencies in vitro. Expression analysis of PyPAD1 showed that the gene was transcribed in all five pear genotypes examined. However, transcript abundance was increased in correlation with the presence of p-hydroxystyrene in resistant cultivars Py-701 and Py-760 and in the sensitive cultivar Spadona when grafted on these resistant cultivars. Thus, PyPAD1 appears to be responsible for the decarboxylation of the p-coumaric acid, and for the production of metabolites that are active against pear psylla.

Seed germination ecology of Bidens pilosa and its implications for weed management.

It is now widely recognized that Bidens pilosa has become a problematic broadleaf weed in many ecosystems across the world and, particularly in the light of recent climate change conditions, closer management strategies are required to curtail its impact on agricultural cropping. In this investigation, experiments were conducted to evaluate the effect of environmental factors on the germination and emergence of B. pilosa, and also on the response of this weed to commonly available post-emergence herbicides in Australia. The environmental factors of particular interest to this current work were the effect of light and temperature, salinity, burial depth and moisture on B. pilosa since these are key management issues in Australian agriculture. In addition, the effects of a number of commonly used herbicides were examined, because of concerns regarding emerging herbicide resistance. In the tested light/dark regimes, germination was found to be higher at fluctuating day/night temperatures of 25/15 °C and 30/20 °C (92-93%) than at 35/25 °C (79%), whilst across the different temperature ranges, germination was higher in the light/dark regime (79-93%) than in complete darkness (22-38%). The standard five-minute temperature pretreatment required for 50% inhibition of maximum germination was found to be 160 °C, and it was further shown that no seeds germinated at temperatures higher than 240 °C. With regard to salinity, some B. pilosa seeds germinated (3%) in 200 mM sodium chloride (NaCl) but all failed to germinate at 250 mM NaCl. Germination declined from 89% to 2% as the external osmotic potential decreased from 0 to -0.6 MPa, and germination ceased at -0.8 MPa. Seeding emergence of B. pilosa was maximum (71%) for seeds placed on the soil surface and it was found that no seedlings emerged from a depth of 8 cm or greater. A depth of 3.75 cm was required to inhibit the seeds to 50% of the maximum emergence. In this study, application of glufosinate, glyphosate and paraquat provided commercially acceptable control levels (generally accepted as >90%) when applied at the four-leaf stage of B. pilosa. However, none of the herbicide treatments involved in this study provided this level of control when applied at the six-leaf stage. In summary, B. pilosa germination has been clearly shown to be stimulated by light and thus its emergence was greatest from the soil surface. This suggests that infestation from this weed will remain as a problem in no-till conservation agriculture systems, the use of which is increasing now throughout the world. It is intended that information generated from this study be used to develop more effective integrated management programs for B. pilosa and similar weeds in commercial agricultural environments which are tending toward conservation approaches.

Responses of the weed Bidens pilosa L. to exogenous application of the steroidal saponin protodioscin and plant growth regulators 24-epibrassinolide, indol-3-acetic acid and abscisic acid.

The exogenous application of plant hormones and their analogues has been exploited to improve crop performance in the field. Protodioscin is a saponin whose steroidal moiety has some similarities to plant steroidal hormones, brassinosteroids. To test the possibility that protodioscin acts as an agonist or antagonist of brassinosteroids or other plant growth regulators, we compared responses of the weed species Bidens pilosa L. to treatment with protodioscin, brassinosteroids, auxins (IAA) and abscisic acid (ABA). Seeds were germinated and grown in agar containing protodioscin, dioscin, brassinolides, IAA and ABA. Root apex respiratory activity was measured with an oxygen electrode. Malondialdehyde (MDA) and antioxidant enzymes activities were assessed. Protodioscin at 48-240 µm inhibited growth of B. pilosa seedlings. The steroidal hormone 24-epibrassinolide (0.1-5 µm) also inhibited growth of primary roots, but brassicasterol was inactive. IAA at higher concentrations (0.5-10.0 µm) strongly inhibited primary root length and fresh weight of stems. ABA inhibited all parameters of seedling growth and also seed germination. Respiratory activity of primary roots (KCN-sensitive and KCN-insensitive) was activated by protodioscin. IAA and ABA reduced KCN-insensitive respiration. The content of MDA in primary roots increased only after protodioscin treatment. All assayed compounds increased APx and POD activity, with 24-epibrassinolide being most active. The activity of CAT was stimulated by protodioscin and 24-epibrassinolide. The results revealed that protodioscin was toxic to B. pilosa through a mechanism not related to plant growth regulator signalling. Protodioscin caused a disturbance in mitochondrial respiratory activity, which could be related to overproduction of ROS and consequent cell membrane damage.

Phytotoxicity of volatile oil from Eucalyptus citriodora against some weedy species.

A study was undertaken to explore the phytotoxicity of volatile essential oil from Eucalyptus citriodora Hook. against some weeds viz. Bidens pilosa, Amaranthus viridis, Rumex nepalensis, and Leucaena leucocephala in order to assess its herbicidal activity. Dose-response studies conducted under laboratory conditions revealed that eucalypt oils (in concentration ranging from 0.0012 to 0.06%) greatly suppress the germination and seedling height of test weeds. At 0.06% eucalypt oil concentration, none of the seed of test weeds germinated. Among the weed species tested, A. viridis was found to be the most sensitive and its germination was completed inhibited even at 0.03%. Not only the germination and seedling growth, even the chlorophyll content and respiratory activity in leaves of emerged seedlings were severely affected. In A. viridis chlorophyll content and respiratory activity were reduced by over 51% and 71%, respectively, even at a very low concentration of 0.06%. These results indicated an adverse effect of eucalypt oils on the photosynthetic and energy metabolism of the test weeds. A strong negative correlation was observed between the observed effect and the concentration of eucalypt oil. Based on the study, it can be concluded that oil from E. citriodora possess strong inhibitory potential against weeds that could be exploited for weed management.

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana.

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils. Bidens maximowicziana is a new Pb hyperaccumulator, which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb. The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues. The Pb distribution order in the B. maximowicziana was: leaf > stem > root. The effect of amendments on phytoremediation was also studied. The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application. Compared with CK (control check), EDTA application promoted translocation of Pb to overground parts of the plant. The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg. This research demonstrated that B. maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil, especially, combination with EDTA.

Uptake and decomposition of the herbicide propanil in the plant Bidens pilosa L. dominating in the Yangtze Three Gorges Reservoir (TGR), China.

Propanil (3',4'-dichloropropionanilide) is a selective post emergence herbicide for controlling broad leaf and grass weeds in rice (Oryza sativa L.). After being taken up by plants, the fate of propanil in decomposing plant material is of particular importance to the phytoremediation of the environment. Therefore, we investigated the biotransformation of propanil in the plant Bidens pilosa under conditions close to those present in the Three Gorges Reservoir (TGR), China. Plants pre-treated with 14C-ring-labeled propanil were either (treatment a) directly submerged in TGR water for 90 days or (treatment b) pre-extracted with organic solvents, and subsequently only insoluble materials and non-extractable residues (NER) of the pesticide fractions were similarly incubated. After incubation in TGR water (treatment a), 30 % of applied radioactivity was released into water and simultaneously, amounts of NER in the plant debris appeared to increase with time finally amounting to 40 % of applied 14C. The radioactivity contained in the extractable fractions were identified as propanil, 3,4-dichloroaniline (DCA), and N-ß-D-glucopyranosyl-3,4-dichloroaniline (DCA-Glu). In treatment b, significant 14C amounts were released to the water (6 % of applied 14C) and the solubilized radioactivity fractions were demonstrated to agree with those found in the extractable fractions. Therefore, if residues of the pesticide propanil are taken up by plants, it may enter again the aquatic environment after plant death and submergence. This phenomenon may have a potential impact on aquatic organisms, which to our knowledge has not been reported before. As plant uptake and degradation of xenobiotics are recognized as detoxification, we consider B. pilosa with its high uptake potential, at least for propanil, as suitable species for phytoremediation.