Toxicity of an Annonin-Based Commercial Bioinsecticide Against Three Primary Pest Species of Stored Products

The effects of a bioinsecticide formulation based on extract of Annona squamosa L. (Annonaceae) containing 10,000 mg L^?1 of acetogenin annonin as the main active ingredient were investigated against three primary pest species of stored grains in Brazil [maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), Mexican bean weevil Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae: Bruchinae), and cowpea weevil Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae: Bruchinae)] by means of residual contact bioassays. In a concentration-dependent manner, the annonin-based commercial bioinsecticide caused significant adult mortality of C. maculatus (LC₅₀ = 6890 μL kg^?1), S. zeamais (LC₅₀ = 2781 μL kg^?1), and Z. subfasciatus (LC₅₀ = 2120 μL kg^?1) after 120 h of residual contact exposure. In addition to acute toxicity, the tested bioinsecticide also promoted a significant reduction of the number of eggs laid by females of C. maculatus (EC₅₀ = 5949.7 μL kg^?1) and Z. subfasciatus (EC₅₀ = 552.7 μL kg^?1). Moreover, the bioinsecticide significantly reduced the number of emerged insects (F₁ generation) of C. maculatus (EC₅₀ = 2763.0 μL kg^?1), S. zeamais (EC₅₀ = 1380.8 μL kg^?1), and Z. subfasciatus (EC₅₀ = 561.5 μL kg^?1). The bioinsecticide also reduced the percentage of damaged grains for the three pest species studied, and its grain-protectant properties are comparable to or superior in efficacy in relation to a diatomaceous earth-based insecticide (Insecto® at 1000 mg kg^?1) used as a positive control. Thus, this standardized formulation has promising bioactivity against stored insect species and can be a useful component for IPM of stored grains in Brazil and elsewhere.     

Effects of Cadmium,Copper, Lead,and Zinc Contamination on Metal Accumulation by Safflower and Wheat

Accumulation of heavy metals (HMs) in cultivated soils is a continuing environmental problem in many parts of the world. An increase in HM concentration can enhance uptake of toxic metals by crops and enter the human food chain. In this study, the uptake behavior of wheat and safflower was evaluated in a calcareous soil by using 12 undisturbed columns in which half were artificially contaminated. Heavy metals in the form of CdCl₂ (15 mg Cd kg^{? 1}), CuSO₄ (585 mg Cu kg^{? 1}), Pb(NO₃)₂ (117 mg Pb kg^{? 1}), and ZnCl₂ (1094 mg Zn kg^{? 1}) were sprayed on the soil surface and completely mixed in the top 10 cm. The background total concentrations of Cd, Cu, Pb and Zn were 1.6, 29.5, 17.5 and 61.2 mg kg^{? 1}, respectively. After metal application, half of the columns (3 contaminated and 3 uncontaminated) were sown with wheat (Triticum aestivum) and the other half with safflower (Carthamus tinctorious) and grown for 74 days until maturity. After harvesting, soil columns were cut into 10-cm sections and analyzed for HNO₃- and DTPA-extractable metal concentrations. Metal concentrations were also measured in different plant tissues. The results showed that artificial contamination of topsoil decreased the transpiration rate of wheat by 12% and that of safflower by 6%. In contaminated columns, Cd, Cu, Pb, and Zn accumulation in wheat shoot was greater by 8.0-, 1.9-, 3.0-, and 2.1-fold than the control, respectively. Accordingly, these numbers were 46.0-, 1.3-, 1.7-, and 1.6-fold in safflower shoot. Soil contamination with HMs resulted in a 55% decrease in shoot dry matter yield of wheat while it had no significant effect on shoot dry matter of safflower. The normalized water consumption for safflower was therefore not affected by metal contamination (≈ 13 mm H₂O g^{? 1} of dry weight for all safflower and uncontaminated wheat treatments), while contaminated wheat was much less water efficient at about 27 mm H₂O g^{? 1} dry weight. It was concluded that although artificial contamination had a negative effect on wheat growth, it did not affect safflower's normal growth and water efficiency.     

Impacts of permethrin contamination on nematode density and diversity: A microcosm study on benthic meiofauna from a Mediterranean coastal lagoon

A microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg⁻¹), P2: medium (25 mg kg⁻¹) and P3: high (250 mg kg⁻¹)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination.     

Translocation and Complex Formation of Root-applied 2,4-D and Picloram in Susceptible and Tolerant Species

Translocation and complex formation of ¹⁴C-labelled 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid (picloram) in seedlings of sunflower (Helianthus annuus L. var. uniflorus), rape (Brassica napus L. cv. Nilla), wheat (Triticum aestivum L. cv. Starke), and Norway spruce (Picea abies (L.) H. Karst.) were studied. The herbicides were absorbed through the roots from the nutrient solution, Picloram was well translocated to the shoots of the four species; while the acropetal translocation of 2,4-D was small except in rape. In 2,4-D-susceptible sunflower and rape and in picloramsusceptible sunflower and spruce the herbicides were recovered mainly in the uncomplexed form. In 2,4-D tolerant wheat and spruce most of the absorbed 2,4-D was converted into water-soluble or TCA-insoluble complexes. In picloram-tolerant wheat and in relatively picloram-tolerant rape, the absorbed picloram was also converted into complexes recovered predominantly in the water-soluble fraction. Most of the complexes released free herbicides by hydrolyzing in NaOH or HCI. The results further support the hypothesis that complex formation counteracts herbicide toxicity.     

Metabolism of 2,4-dinitrotoluene (2,4-DNT) by Alcaligenes sp. JS867 under oxygen limited conditions

Transformation of 2,4-dinitrotoluene (2,4-DNT) by Alcaligenes JS867 undervarying degrees of oxygen limitation was examined. Complete 2,4-DNT removalwas observed under oxygen excess with near stoichiometric release (83%) of nitrite.Average kinetic parameters were estimated based on a dual-Monod biokinetic modelwith 2,4-DNT and O₂ as growth limiting substrates. The negative impact of nitrite accumulation on the reaction rate was adequately described by inclusion of a noncompetitive inhibition term for NO₂ ^-. Under aerobic conditions, _max, K_sDNT, andK_iNO were 0.058(0.004) hr^-1, 3.3(±1.3) mg 2,4-DNT/L, and 1.2(±pm0.2) hr^-1, respectively. At increasing oxygen limitation, rates of 2,4-DNT disappearance and nitrite production decreased and incomplete removal of 2,4-DNT commenced. JS867 was able to use NO₂ ^- as a terminal electron acceptor whengrown on glucose or succinate under anaerobic conditions. However, during growthon 2,4-DNT and under O₂-limited conditions, JS867 did not use released nitrite as electron acceptor. The nearly constant molar ratios of DNT removed over NO₂ ^- released under various degrees of oxygen limitation suggested that oxygenolytic denitration pathways continued. No evidence of nitroreduction was obtained under the examined oligotrophic conditions. JS867 displayed a high affinity for oxygen consumption with K_SO2 value of 0.285(±0.198) mg O₂/L. Our results indicate thatunder oligotrophic conditions with 2,4-DNT as dominant carbon source, oxygen availability and nitrite accumulation may limit 2,4-DNT biomineralization, but the accumulation of reduced 2,4-DNT transformation products will be small.     

Germination of grass species in soil affected by crude oil contamination

Many grass species exist in the oil exploration areas of North Dakota. The objective of this study was to evaluate seed germination of 65 grass species affected by crude oil. Germination of all species was reduced by crude oil, ranging from 4.3 to 100%. Twenty-eight species were tolerant, 29 moderately tolerant, 6 moderately sensitive, and 2 sensitive. Based on the tolerance levels, the following were used to further test the dose response to crude oil: strong creeping red fescue (Festuca rubra L. ssp. rubra), perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), buffalograss [Buchloe dactyloides (Nutt.) Engelm.], little bluestem [Schizachyrium scoparium (Michx.) Nash], witchgrass (Panicum capillare L.), sand dropseed [Sporobolus cryptandrus (Torr.) Gray], Johnsongrass [Sorghum halepense (L.) Pers.], and smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.]. The EC₅₀ of germination and biomass was effective in ranking the 9 species. Buffalograss, sand dropseed, and orchardgrass were ranked as the most tolerant species with EC₅₀ values of 0.1, > highest concentration tested, 0.05 m³ m^?3 (P < 0.05), respectively. Smooth crabgrass and little bluestem were ranked as most sensitive with EC₅₀ values of 0.03 and 0.04 m³ m^?3 (P < 0.05), respectively. Buffalograss showed the lowest germination (10.4%) and biomass reduction (25%) (P < 0.05).     

Evaluation of Copper Bioaccumulation and Translocation in Jatropha curcas Grown in a Contaminated Soil

Contamination of soils with copper (Cu) has become a serious problem in the environment. Phytoremediation is an emerging green technology that uses green plants to remediate heavy metal contaminated areas. This study was conducted to evaluate the potential of Jatropha curcas for remediation of soils contaminated with Cu. Seedlings were planted in soils spiked with Cu in amount of 0, 50, 100, 200, 300, and 400 mg kg^–1 (Cu_0, Cu₅₀,Cu₁₀₀,Cu₂₀₀,Cu_300, and Cu₄₀₀) for a period of five months. The maximum height and number of leaves were recorded in control (Cu₀) whereas the highest basal stem diameter was found in seedlings exposed to Cu₅₀. Copper concentrations among plant parts were in the following trend: roots > stems > leaves. The highest total Cu concentration (665 ± 1 mg kg^?1) and total Cu removal (1.2 ± 0.2%) based on total plant dry biomass were found in Cu₄₀₀ and Cu₅₀ treatments, respectively. J. curcas exhibited high root concentration factor (RCF > 1) and low translocation factor (TF < 1). Although Cu accumulation by the plant didn't reach the criteria of Cu hyperaccumulators, this species showed a potential to be used in phytostabilization of mildly Cu contaminated areas. However, the plant cannot be used for phytoextraction of Cu-contaminated soils.     

Transgenic tobacco plants overexpressing a cold-adaptive nitroreductase gene exhibited enhanced 2,4-dinitrotoluene detoxification rate at low temperature

Abstract

Plants encounter many environmental factors such as low and high temperatures during phytoremediation processes. In this study, our aim was to produce the transgenic tobacco plants by using a newly characterized bacterial nitroreductase, Ntr, which was active at a broad range temperature in order to detoxify 2,4-dinitrotoluene (2,4-DNT) at lower temperature. The presence of Ntr and its heterologous expression was verified in T1 transgenic plants and their growing ability were determined under toxic amount of 2,4-DNT (35?µM). Fresh weight and dry weight of transgenic plants were significantly higher than wild type (WT) under toxic 2,4-DNT at 22?°C, indicating higher growth capacity of the transgenics. Transgenic plants also showed a higher tolerance than WT when exposed to 2,4-DNT at 15?°C. Moreover, transformation rate of 2,4-DNT was gradually decreased through decreasing temperatures in WT media, however, it was increased through decreasing temperatures in transgenic plant TR3-25 media and it had the highest transformation rate (54%) of 2,4-DNT at 4?°C. Correlatively, 2,4-DNT treatment at 4?°C led to a significant decrease in H₂O₂ level in transgenic plants. Thus, transgenic plants overexpressing nitroreductase might have an important advantage for phytoremediation of toxic nitroaromatic compounds in field applications at low temperatures.     

Mycobiota and mycotoxins in malted barley and brewer's spent grain from Argentinean breweries

Aims: To evaluate mycobiota and aflatoxins B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁), G₂ (AFG₂) and fumonisin B₁ (FB₁) contamination in different malted barley types and brands and brewer’s grain collected from a major Argentinean brewery. Methods and Results: Total fungal counts were performed using the plate count method. Aflatoxin B₁, AFB₂, AFG₁, AFG₂ and Zearalenone (ZEA) analyses were performed by thin‐layer chromatography (TLC). Fumonisin B₁ was determined by HPLC. Eighty‐three percentage of the malted barley (100% M1, 50% M2 and 100% M3) and 61% of brewer’s grain samples had a count >1 × 10⁴ CFU g^?1. Yeasts were isolated from all malt and brewer’s grain samples. Genera containing some of the most important mycotoxin producer species –Fusarium ssp., Aspergillus ssp., Penicillium ssp. and Alternaria ssp. – were isolated from the analysed samples, along with other environmental saprophytic fungi such as Geotrichum ssp., Mucorales and Cladosporium ssp. All samples were contaminated with 104–145 μg kg^?1 FB₁. Eighteen per cent of brewer’s grain samples were contaminated with 19–44·52 μg kg^?1 AFB₁. Aflatoxin B₂, AFG₁, AFG₂ and ZEA were not detected in any of the analysed samples. Conclusions: Fungal and mycotoxin contamination in malt and brewer’s grain is an actual risk for animal and human health. Significance and Impact of the Study: This study may be useful for assessing the risk of mycotoxins in Argentinean beers and especially in animal feeds.     

Long-Term Explosive Contamination in Soil: Effects on Soil Microbial Community and Bioremediation

Explosive contamination in soil is a great concern for environmental health. Following 50 years of munitions manufacturing and loading, soils from two different sites contained ≥ 6,435 mg 2,4,6-trinitrotoluene (TNT), 2,933 mg hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,135 mg octahydrol-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) kg^{? 1} soil. Extractable nitrate-N was as high as 315 and ammonium-N reached 150 mg N kg^{? 1} soil. Water leachates in the highly contaminated soils showed near saturation levels of TNT and RDX, suggesting great risk to water quality. The long-term contamination resulted in undetectable fungal populations and as low as 180 bacterial colony forming units (CFU) g^–1 soil. In the most severely contaminated soil, dehydrogenase activity was undetectable and microbial biomass carbon was very low (< 3.4 mg C _mic kg^–1 soil). The diminished biological activity was a consequence of long-term contamination because short-term (14 d) contamination of TNT at up to 5000 mg TNT kg^–1 soil did not cause a decline in the culturable bacterial population. Natural attenuation may not be a feasible remediation strategy in soils with long-term contamination by high concentrations of explosives.     

l-Glutamate Uptake Inhibitors May Stimulate Phosphoinositide Hydrolysis in Baby Hamster Kidney Cells Expressing mGluR1a via Heteroexchange with l-Glutamate Without Direct Activation of mGluR1a

Abstract: The functional efficacies of inhibitors of l -glutamate uptake for altering second messenger formation in baby hamster kidney cells expressing subtypes mGluR1a, mGluR2, and mGluR4 of the metabotropic glutamate receptor family were examined. l -Serine-O-sulfate was an agonist at mGluR1a (EC₅₀ = 70 µM), mGluR2 (EC₅₀ = 25 µM), and mGluR4 (EC₅₀ = 324 µM). l -Cysteine sulfinate, 1-aminocyclobutane-trans-1,3-dicarboxylate, l -cysteine, and dl -threo-3-methylaspartate stimulated phosphoinositide hydrolysis in mGluR1a cells with EC₅₀ values of 43, 64, 463, and 488 µM, respectively, and displaced l -[³H]glutamate binding from membranes prepared from these cells with respective IC₅₀ values of 48, 44, 79, and 139 µM. However, d -aspartate,l -trans-pyrrolidine-2,4-dicarboxylate, l -threo-3-hydroxyaspartate, and l -aspartate-β-hydroxamate stimulated phosphoinositide hydrolysis in mGluR1a cells (respective EC₅₀ values of 73, 54, 57, and 430 µM) but did not displace l -[³H]glutamate binding. These compounds inhibited Na⁺-dependent l -glutamate uptake into baby hamster kidney cells with IC₅₀ values similar to those for stimulation of phosphoinositide hydrolysis in mGluR1a cells. Phosphoinositide hydrolysis in mGluR1a cells, as stimulated by inhibitors of (or substrates for) this l -glutamate transporter, was significantly attenuated in the presence of l -glutamate decarboxylase (EC 4.1.1.15) or l -alanine aminotransferase (EC 2.6.1.2). Furthermore, incubation with 1 mMl -trans-pyrrolidine-2,4-dicarboxylate for 30 min increased the basal levels of free glutamate (1.5 ± 0.2 µM) in the assay buffer four- to fivefold as measured by HPLC analysis. Thus, heteroexchange with endogenous l -glutamate may lead to erroneous estimations of the functional efficacies at mGluR1a.     

Emission of hydrogen sulfide by twigs of coniferes — acomparison of Norway spruce (Picea abies (L.) Karst.), Scotch pine (Pinus sylvestris L.) and Blue spruce (Picea pungens Engelm.)

The emission of reduced volatile sulfur compounds from twigs of Norway spruce (Picea abies (L.) Karst.) was measured in the field by cryosampling and gaschromatographic analysis. Trees were growing in the Erzgebirge (E-Germany) at Oberbärenburg and at the Kahleberg and at a third stand in NW-Bavaria (S-Germany). Emission rates were also measured for Scotch pine (Pinus sylvestris L.) and Blue spruce (Picea pungens Engelm.) at the Kahleberg. Twigs still attached to the trees were enclosed in a flow-through gas exchange cuvette. H₂S was detected as the predominant reduced sulfur compound emitted from the twigs. The mean H₂S emission rate from twigs of Norway spruce varied between 0.04 pmol kg^-1 dw s^-1 at Würzburg and 6.21 pmol kg^-1 dw s^-1 at the Kahleberg. Comparing different species at the Kahleberg, the mean H₂S emission rate was almost the same from twigs of Norway spruce (6.2 pmol kg^-1 dw s^-1) and Blue Spruce trees (5.9 pmol kg^-1 dw s^-1) but it was approximately 18 times higher for Scotch pine (110 pmol kg^-1 dw s^-1). The percentage of SO₂-exclusion via H₂S-emission of the tree species investigated at the Kahleberg is calculated on the basis of data on SO₂ fluxes. It is very small for Norway spruce and Blue spruce. However, for Scotch pine, H₂S emission contributes about 10% to the detoxification of SO₂.     

Comparative growth inhibitory and antifeedant effects of plant extracts and pure allelochemicals on four phytophagous insect species

Antifeedant and growth inhibitory effects of crude plant extracts (Melia volkensii and Origanum vulgare) and pure allelochemicals (digitoxin, cymarin, xanthotoxin, toosendanin, thymol and trans‐anethole) were investigated in the cabbage looper (Trichoplusia ni), and in the armyworm (Pseudaletia unipuncta) using different bioassays. Antifeedant effects of M. volkensii, O. vulgare and thymol were investigated in larvae of the diamondback moth (Plutella xylostella), and of O. vulgare and thymol in the Mexican bean beetle (Epilachna varivestis), using leaf disc choice bioassays. M. volkensii was the most potent growth inhibitor for T. ni and P. unipuncta (dietary EC₅₀ = 7.6 and 12.5 p.p.m., respectively) of all the test substances. Cymarin was the second most potent growth inhibitor (EC₅₀ = 132.0 p.p.m.) for T. ni. The most effective feeding deterrents for third instar T. ni larvae were xanthotoxin andM. volkensii (DC₅₀ = 0.9 and 8.3 μg/cm², respectively). M. volkensii was also the most potent feeding deterrent for third instar P. unipuncta, P. xylostella and adult E. varivestis (DC₅₀ = 10.5, 20.7 and 2.3 μg/cm², respectively). Because of interspecific differences in response to feeding deterrents and the lack of a strong relationship between EC₅₀ and DC₅₀ values, we recommend testing a battery of bioassay species with candidate compounds and the use of more than one bioassay. Based on their growth inhibitory and feeding deterrent properties, some of these plant extracts and pure allelochemicals have potential for use as alternative crop protectants against a number of pest species.     

A comparison of arsenic mobility in Phaseolus vulgaris, Mentha aquatica, and Pteris cretica rhizosphere

The ability of Phaseolus vulgaris, Mentha aquatica, and Pteris cretica to release arsenic (As) species from contaminated soil was tested in rhizobox experiments in three soils differing in their physicochemical parameters and total and mobile As concentration. Relatively low uptake of arsenic by P. vulgaris and M. aquatica resulted in very low and ambiguous changes in rhizosphere soil compared to bulk soil. However, there were observed differences in the distribution of the mobile As portion in soil to individual As species as affected by plant species and/or plantation conditions of these plants. Higher percentage of mobile arsenite in mint rhizosphere seems to be related to more reducing conditions during cultivation of these wetland plants. P. cretica planted in the soils containing between 36 and 1436 mg As kg⁻¹ was able to accumulate between 80 and 500 mg As kg⁻¹ in aboveground biomass. The extractable concentrations of As compounds in rhizosphere soil of P. cretica showed a clear depletion of arsenate (representing more than 90% of extractable arsenic) with the distance from plant roots. However, the As uptake mechanisms, as well as As transformation within hyperaccumulating fern plants, differ substantially from those in higher plants. Therefore the finding of suitable higher plant tolerant to the As soil contamination with good ability to accumulate As in aboveground biomass remains for the further research.     

Biotransformation of 2,4-dinitrotoluene in a phototrophic co-culture of engineered Synechococcus elongatus and Pseudomonas putida

In contrast to the current paradigm of using microbial mono-cultures in most biotechnological applications, increasing efforts are being directed towards engineering mixed-species consortia to perform functions that are difficult to programme into individual strains. In this work, we developed a synthetic microbial consortium composed of two genetically engineered microbes, a cyanobacterium (Synechococcus elongatus PCC 7942) and a heterotrophic bacterium (Pseudomonas putida EM173). These microbial species specialize in the co-culture: cyanobacteria fix CO₂ through photosynthetic metabolism and secrete sufficient carbohydrates to support the growth and active metabolism of P. putida, which has been engineered to consume sucrose and to degrade the environmental pollutant 2,4-dinitrotoluene (2,4-DNT). By encapsulating S. elongatus within a barium–alginate hydrogel, cyanobacterial cells were protected from the toxic effects of 2,4-DNT, enhancing the performance of the co-culture. The synthetic consortium was able to convert 2,4-DNT with light and CO₂ as key inputs, and its catalytic performance was stable over time. Furthermore, cycling this synthetic consortium through low nitrogen medium promoted the sucrose-dependent accumulation of polyhydroxyalkanoate, an added-value biopolymer, in the engineered P. putida strain. Altogether, the synthetic consortium displayed the capacity to remediate the industrial pollutant 2,4-DNT while simultaneously synthesizing biopolymers using light and CO₂ as the primary inputs.     

Effect of bacterial inoculation of strains of pseudomonas aeruginosa,alcaligenes feacalis and bacillus subtilis on germination,growth and heavy metal (cd,cr, and ni) uptake of brassica juncea

Bacterial inoculation may influence Brassica juncea growth and heavy metal (Ni, Cr, and Cd) accumulation. Three metal tolerant bacterial isolates (BCr3, BCd33, and BNi11) recovered from mine tailings, identified as Pseudomonas aeruginosa KP717554, Alcaligenes feacalis KP717561, and Bacillus subtilis KP717559 were used. The isolates exhibited multiple plant growth beneficial characteristics including the production of indole-3-acetic acid, hydrogen cyanide, ammonia, insoluble phosphate solubilization together with the potential to protect plants against fungal pathogens. Bacterial inoculation improved seeds germination of B. juncea plant in the presence of 0.1 mM Cr, Cd, and Ni, as compared to the control treatment. Compared with control treatment, soil inoculation with bacterial isolates significantly increased the amount of soluble heavy metals in soil by 51% (Cr), 50% (Cd), and 44% (Ni) respectively. Pot experiment of B. juncea grown in soil spiked with 100 mg kg^?1 of NiCl₂, 100 mg kg^?1 of CdCl₂, and 150 mg kg^?1 of K₂Cr₂O₇, revealed that inoculation with metal tolerant bacteria not only protected plants against the toxic effects of heavy metals, but also increased growth and metal accumulation of plants significantly. These findings suggest that such metal tolerant, plant growth promoting bacteria are valuable tools which could be used to develop bio-inoculants for enhancing the efficiency of phytoextraction.     

Microbial Transformation of Nitroaromatics in Surface Soils and Aquifer Materials

Microorganisms indigenous to surface soils and aquifer materials collected at a munitions-contaminated site transformed 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) to amino-nitro intermediates within 20 to 70 days. Carbon mineralization studies with both unlabeled (TNT, 2,4-DNT, and 2,6-DNT) and radiolabeled ([¹⁴C]TNT) substrates indicated that a significant fraction of these source compounds was degraded to CO₂.     

土壤铅胁迫对苘麻光合特性及生物量的影响

为明确不同浓度铅污染对苘麻(Abutilon theophrasti)光合特性及生长的影响程度,揭示苘麻对铅胁迫的光合适应能力,在铅污染土壤区域提供潜在物种。该研究设置五个铅浓度梯度(0、500、1 000、1 500、2 000 mg·kg~(-1)),分析了在不同浓度铅污染胁迫下,苘麻的铅积累、气体交换参数、叶绿素荧光特性及生物量的变化。结果表明:当铅浓度在1 000 mg·kg~(-1)以下时,净光合速率(P_n)和气孔导度(G_s)、光化学效率(F_v/F_m)、电子传递速率(ETR)的值分别与空白组的P_n、G_s、F_v/F_m、ETR值相比均不显著(P0.05),表明铅浓度小于1 000 mg·kg~(-1)时,苘麻的光合活性未受到损伤,有很强的光合适应能力。苘麻生物量在500、1 000 mg·kg~(-1)铅胁迫下为空白组的88.6%、106%,苘麻能够正常生长,说明苘麻能够适应铅污染的胁迫。当铅浓度低于1 000 mg·kg~(-1)时,苘麻地上部与地下部对铅富集与转移的效果较好,表明在铅污染区苘麻也具有较强的铅积累能力。根据铅污染土壤区域的实际情况,结合苘麻在低浓度铅污染修复效率高的特点,认为苘麻可以作为铅污染地区修复的潜在物种。     

Evaluation of the electro-ultrafiltration technique (EUF) as a measure of the K supplying power of Quebec soils

The electro-ultrafiltration (EUF) method has been used to evaluate the short-term and long-term supplying power of soils for many essential plant nutrients. The objective of this study was to compare the capacity of EUF with other extraction techniques to predict the plant availability of soil K and K fertilizer responsiveness by 10 cuts of alfalfa (Medicago sativa L.) growing over a 366-day period. Increasingly higher average concentrations of soil K were extracted by EUF at 50 V and 20°C (29 mg kg^-1), EUF at 200 V and 20°C (48 mg kg^-1), 0.002 M SrCl₂ (55 mg kg^-1), EUF at 200 V and 80°C (85 mg kg^-1), 0.1 M HCl (105 mg kg^-1), Mehlich 3 (119 mg kg^-1), 1 M NH₄OAc (120 mg kg^-1) and boiling 1 M HNO₃ (601 mg kg^-1). The large content of vermiculitic minerals in the silt and clay fractions is responsible for EUF desorbing more K in 55 minutes than NH₄OAc in 29 out of 30 soils. The total amount of K desorbed by EUF at 80°C was as effective as Mehlich 3-extractable K in predicting K uptake for the first three cuts and was best among the extracting procedures after boiling 1 M HNO₃ in predicting the long-term K supply, the uptake of K from non-exchangeable sources and the relative yield of alfalfa over 10 cuts. The desorption of soil K with EUF provides a better evaluation of the K-supplying power of Quebec soils than the extractants currently used, especially on a long-term basis.Contribution no. 396.     

Accumulation of arsenic and heavy metals in some Viola species from an abandoned mine,Alchar, Republic of Macedonia (FYROM)

Abstract

The uptake and distribution of arsenic (As) and some heavy metals was determined in three Viola endemic species from As‐overloaded soil in an abandoned mine at Alchar, Republic of Macedonia (FYROM – The Former Yugoslav Republic of Macedonia). Some essential elements were also analyzed in order to characterize the common geochemical properties of this site. Total As content in soil ranged from 3347 to 14,467 mg kg^?1, and plant available As from 23 to 1589 mg kg^?1. The concentration of As in roots ranged from 783 mg kg^?1 in Viola macedonica to 2124 mg kg^?1 in Viola arsenica. Only a small amount of As accumulated in the aboveground parts of these species (<100 mg kg^?1), while in shoots of Viola allchariensis, As accumulated in the range 187–439 mg kg^?1. Arsenic accumulation in the roots of these Viola species may make these plants valuable tools for the bioindication and phytoremediation (phytostabilization) of As in naturally loaded and anthropogenically contaminated soils.