Effects of antibiotics on secondary metabolism and oxidative stress in oilseed rape seeds.

Cruciferae brassica oilseed rape is the third largest oilseed crop in the world and the first in China, as well as a fertilizer-dependent crop. With the increased application of organic fertilizers from livestock manure in agricultural production in recent years, the resulting antibiotic pollution and its ecological health effects have attracted widespread attention. In this study, typical tetracycline and sulfonamide antibiotics tetracycline (TC) and sulfamethoxazole (SMZ) were used to investigate the effects of antibiotics on rapeseed quality and oxidative stress at the level of secondary metabolism on the basis of examining the effects of the two drugs on the growth of soil-cultivated rapeseed seedlings. The results showed that both plant height and biomass of rapeseed seedlings were significantly suppressed and ROS were significantly induced in rapeseed by exposure to high concentrations (2.5 mg/kg) of TC and SMZ. Carotenoids, tocopherols, and SOD enzymes were involved in the oxidative stress response to scavenge free radicals in rapeseed, but phenolic acids and flavonoids contents were decreased, which reduced the quality of the seeds to some extent.

Influence of Genotype on High Glucosinolate Synthesis Lines of Brassica rapa.

This study was conducted to investigate doubled haploid (DH) lines produced between high GSL (HGSL) Brassica rapa ssp. trilocularis (yellow sarson) and low GSL (LGSL) B. rapa ssp. chinensis (pak choi) parents. In total, 161 DH lines were generated. GSL content of HGSL DH lines ranged from 44.12 to 57.04 µmol·g-1·dry weight (dw), which is within the level of high GSL B. rapa ssp. trilocularis (47.46 to 59.56 µmol g-1 dw). We resequenced five of the HGSL DH lines and three of the LGSL DH lines. Recombination blocks were formed between the parental and DH lines with 108,328 single-nucleotide polymorphisms in all chromosomes. In the measured GSL, gluconapin occurred as the major substrate in HGSL DH lines. Among the HGSL DH lines, BrYSP_DH005 had glucoraphanin levels approximately 12-fold higher than those of the HGSL mother plant. The hydrolysis capacity of GSL was analyzed in HGSL DH lines with a Korean pak choi cultivar as a control. Bioactive compounds, such as 3-butenyl isothiocyanate, 4-pentenyl isothiocyanate, 2-phenethyl isothiocyanate, and sulforaphane, were present in the HGSL DH lines at 3-fold to 6.3-fold higher levels compared to the commercial cultivar. The selected HGSL DH lines, resequencing data, and SNP identification were utilized for genome-assisted selection to develop elite GSL-enriched cultivars and the industrial production of potential anti-cancerous metabolites such as gluconapin and glucoraphanin.

Characterization of Brassica rapa metallothionein and phytochelatin synthase genes potentially involved in heavy metal detoxification.

Brassica rapa is an important leafy vegetable that can potentially accumulate high concentrations of cadmium (Cd), posing a risk to human health. The aim of the present study was to identify cadmium detoxifying molecular mechanisms in B. rapa using a functional cloning strategy. A cDNA library constructed from roots of B. rapa plants treated with Cd was transformed into the Cd sensitive yeast mutant strain DTY167 that lacks the yeast cadmium factor (YCF1), and resistant yeast clones were selected on Cd containing media. Two hundred genes potentially conferring cadmium resistance were rescued from the surviving yeast clones and sequenced. Sequencing analysis revealed that genes encoding for metallothionein (MT)1, MT2a, MT2b and MT3, and phytochelatin synthase (PCS)1 and PCS2 accounted for 35.5%, 28.5%, 4%, 11.3%, 18.7% and 2%, respectively of the genes identified. MTs and PCSs expressing DTY167 cells showed resistance to Cd as well as to Zn. PCS1 expressing yeast cells were also more resistant to Pb compared to those expressing MTs or PCS2. RT-PCR results showed that Cd treatment strongly induced the expression levels of MTs in the root and shoot. Furthermore, the different MTs and PCSs exhibited tissue specific expression. The results indicate that MTs and PCS genes potentially play a central role in detoxifying Cd and other toxic metals in B. rapa.

The transcriptional response to salicylic acid plays a role in Fusarium yellows resistance in Brassica rapa L.

KEY MESSAGE: Fusarium yellows resistant and susceptible lines in Brassica rapa showed different salicylic acid responses; the resistant line showed a similar response to previous reports, but the susceptible line differed. Fusarium yellows caused by Fusarium oxysporum f. sp. conglutinans (Foc) is an important disease. Previous studies showed that genes related to salicylic acid (SA) response were more highly induced following Foc infection in Brassica rapa Fusarium yellows resistant lines than susceptible lines. However, SA-induced genes have not been identified at the whole genome level and it was unclear whether they were up-regulated by Foc inoculation. Transcriptome analysis with and without SA treatment in the B. rapa Fusarium yellows susceptible line 'Misugi' and the resistant line 'Nanane' was performed to obtain insights into the relationship between SA sensitivity/response and Fusarium yellows resistance. 'Nanane's up-regulated genes were related to SA response and down-regulated genes were related to jasmonic acid (JA) or ethylene (ET) response, but differentially expressed genes in 'Misugi' were not. This result suggests that Fusarium yellows resistant and susceptible lines have a different SA response and that an antagonistic transcription between SA and JA/ET responses was found only in a Fusarium yellows resistant line. SA-responsive genes were induced by Foc inoculation in Fusarium yellows resistant (RJKB-T23) and susceptible lines (RJKB-T24). By contrast, 39 SA-induced genes specific to RJKB-T23 might function in the defense response to Foc. In this study, SA-induced genes were identified at the whole genome level, and the possibility, the defense response to Foc observed in a resistant line could be mediated by SA-induced genes, is suggested. These results will be useful for future research concerning the SA importance in Foc or other diseases resistance in B. rapa.

Hydrogen peroxide modification affects the structure and physicochemical properties of dietary fibers from white turnip (Brassica Rapa L.).

Turnip (Brassica rapa L.) is widely consumed as a vegetable and traditional Chinese medicine with high dietary fiber content. Soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) were obtained from white turnips, and the IDF was modified with alkaline hydrogen peroxide to obtain modified IDF (MIDF) and modified SDF (MSDF). The compositional, structural, and functional properties of the four samples were investigated. After modification, the modified dietary fibers (MDFs) showed smaller particle sizes and lower contents of pectin and polyphenol than those of unmodified dietary fibers (DFs) The results of scanning electron microscopy (SEM), Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) showed that compared to the DFs, the MDFs were smaller and had more exposed hydroxyl groups. Analysis of the microrheological behaviors showed that the MDFs had higher viscosity than that of the DFs, with a looser structure for the MSDF and a stable structure for the MIDF. Therefore, due to structural changes, the physical and functional properties of the MDFs were improved compared to those of the unmodified DFs. Pearson correlation analysis showed that the particle size was positively correlated with the pectin content. The water holding capacity (WHC), oil adsorption capacity (OAC) and water swelling capacity (WSC) showed positive correlations with each other. This work indicated that white turnip could be a potential new source of DFs, which presented desirable functional properties after modification.

Study amino acid contents, plant growth variables and cell ultrastructural changes induced by cadmium stress between two contrasting cadmium accumulating cultivars of Brassica rapa ssp. chinensis L. (pak choi).

Cadmium (Cd) is an inauspicious abiotic traction that not only influences crop productivity and its growth parameters, but also has adverse effects on human health if these crops are consumed. Among crops, leafy vegetables which are the good source of mineral and vitamins accumulate more Cd than other vegetables. It is thus important to study photosynthetic variables, amino acid composition, and ultrastructural localization of Cd differences in response to Cd accumulation between two low and high Cd accumulating Brassica rapa ssp. chinensis L. (pak choi) cultivars, differing in Cd accumulation ability. Elevated Cd concentrations significantly lowered plant growth rate, biomass, leaf gas exchange and concentrations of amino acids collated to respective controls of both cultivars. Electron microscopy indicated that the impact of high Cd level on ultrastructure of leaf cells was associated to affecting cell functionalities, i.e. irregular cell wall, withdrawal of cell membrane, and chloroplast structure which has negative impact on photosynthetic activities, thus causing considerable plant growth suppression. Damage in root cells were observed in the form of enlargement of vacuole. The energy dispersive micro X-ray spectroscopy of both cultivars leaves indicated that cellular structure exhibited exudates of Cd-dense material. Ultrastructural damages and phytotoxicity were more pronounced in high accumulator cultivar as compared to the low accumulator cultivar. These findings are useful in determining the mechanisms of differential Cd-tolerance among cultivars with different Cd tolerance abilities at cellular level.

Cloning and Functional Analysis of BcMYB101 Gene Involved in Leaf Development in Pak Choi (Brassica rapa ssp. Chinensis).

As one of the largest transcription factor families, MYB transcription factors are widely present, and they are involved in a diverse range of physiological activities in plants, such as leaf development. GAMYB genes belong to the R2R3-MYB subfamily, which includes the MYB33/65/101 gene, and these genes are studied well in seed germination and flowering, but their roles in leaf development are poorly understood. In the current study, we isolated a GAMYB transcription factor from pak choi, BcMYB101, and analyzed its characteristics and function. The sequence structure analysis indicated that BcMYB101 has a highly conserved R2R3 DNA-binding domain in the N-terminal region and three GAMYB-specific motifs (Box1, Box2, and Box3). The expression pattern of diverse tissues revealed that BcMYB101 has a higher transcript level in the petiole, leaf, root, and floral organs. Furthermore, the expression level was significantly elevated after GA (gibberellin) treatment, suggesting that the BcMYB101 response was positively regulated by GA. Subcellular localization exhibited that BcMYB101 was only present in the nuclear region, consistent with the characterization of the transcription factor. The overexpression of BcMYB101 elucidated that BcMYB101 increased leaf number and resulted in downward-curling cauline leaves. Moreover, the virus-induced BcMYB101 silencing displayed that BcMYB101 is involved in the regulation of curly leaves. Furthermore, we discovered that BcMYB101 has two trans-activation activities and one interaction protein, BcTCH4, using a trans-activation activity assay and a yeast two-hybrid assay, respectively. In this study, we firstly isolated the BcMYB101 gene and explored its function in leaf development, thereby providing a solid foundation for further research on the regulatory mechanism of leaf shape in Brassica or other species.

Ethylene negatively mediates self-incompatibility response in Brassica rapa.

Self-incompatibility (SI) is a genetic mechanism most flowering plants adopted to reject self-pollen thus avoid inbreeding. In the Brassicaceae, self-pollen recognition triggers downstream signaling pathways to reject self-pollen. However, the downstream signaling pathways are not very clear. Here we show that ethylene negatively mediates self-incompatibility response of Chinese cabbage (Brassica rapa L. ssp. Pekinensis) via PCD in papilla cells. We found that ethylene signaling genes were upregulated after cross-pollination. Treating stigmas with ethylene, or suppressing the expression of a negative regulator of ethylene signaling, CONSTITUTIVE TRIPLE RESPONSE 1 (CTR1), caused PCD in papilla cells and broke down the self-incompatibility. On the other hand, treating stigmas with ethylene inhibitors, or suppressing the expression of ethylene-responsive factors (ERFs), inhibited PCD in papilla cells and the compatible pollination. Our study identified an additional signaling pathway mediating self-incompatibility responses in the Brassicaceae and also developed a new method in overcoming self-incompatibility to improve the efficiency of inbred line propagation in agriculture practice.

High-level waste activated sludge dewaterability using Fenton-like process based on pretreated zero valent scrap iron as an in-situ cycle iron donator.

A novel, recyclable, and rapid pre-ultrasound-thermal-acid-washed zero valent scrap iron/hydrogen peroxide (UTA-ZVSI/H2O2) method has been developed to effectively enhance waste activated sludge (WAS) dewaterability. The effects of UTA ultrasound densities, UTA temperature, newly generated iron solution, H2O2 concentrations, and WAS conditioning time on the WAS dewaterability were investigated using a bench-scale system. Results indicated that the UTA-ZVSI/H2O2 treatment significantly improved the WAS dewaterability. The water content of the dewatered cake decreased to 44.15 ± 0.98 wt% during optimal operational conditions, which was significantly lower than that achieved using Fenton-based processes. Based on this outcome, a three-step treatment mechanism involving UTA-ZVSI/H2O2 has been developed, including iron flocculation, hydroxyl radical oxidation, and skeleton building. The dewatering efficiencies of three types of representative WAS were consistently effective in the UTA-ZVSI/H2O2 reactor for up to 15 cycles. Efficiencies levels were significantly higher than those achieved with Fenton-based processes. Economic analysis illustrated that the developed UTA-ZVSI/H2O2 system was the most cost-effective among other WAS dewatering treatments. In addition, the treatment system significantly alleviated toxicity of heavy metals and phytotoxicity in the dewatered sludge. This supported subsequent agricultural use. In summary, this study provided a comprehensive and useful basis for improving WAS dewatering and subsequent disposal.

Sensitivity difference between skotomorphogenesis and photomorphogenesis of plants to antibiotics: A call for research.

Seedling establishment consists of the former stage (i.e. skotomorphogenesis) and the latter stage (i.e. photomorphogenesis). Due to specific developmental processes in plants, the two stages may have different sensitivities to antibiotics. Tetracycline (TC), for example, is a major-use antibiotic. Radicle length, the relatively sensitive endpoint in plant skotomorphogenesis, is less sensitive than all of the indices of cotyledon colour and pigments in plant photomorphogenesis to TC stress. In conclusion, we suggest that plant photomorphogenesis may be more sensitive than plant skotomorphogenesis to stresses of antibiotics, but which needs further studies.

Effect of prohydrojasmon on total phenolic content, anthocyanin accumulation and antioxidant activity in komatsuna and lettuce.

Prohydrojasmon has been reported to improve the quality of crops. However, most previous studies have investigated its application on fruits. Here, we evaluated the effect of prohydrojasmon on the growth and total phenolic content, anthocyanin content, and antioxidant activity in komatsuna (Brassica rapa var. periviridis) and lettuce (Lactuca sativa L.). Prohydrojasmon did not show any serious inhibitory effect. Prohydrojasmon applied to komatsuna at a concentration of 0.5 µM significantly increased the total phenolic content and anthocyanin content, and a concentration of 1 µM increased the antioxidant activity. In lettuce, prohydrojasmon at a concentration of 400 µM significantly increased the total phenolic content and anthocyanin content, while a concentration of 0.5 µM significantly increased the antioxidant activity. These results suggest that prohydrojasmon positively affects the phenolic compound and anthocyanin accumulation and antioxidant activity in komatsuna and lettuce without adversely affecting growth.

Modulation of growth performance and coordinated induction of ascorbate-glutathione and methylglyoxal detoxification systems by salicylic acid mitigates salt toxicity in choysum (Brassica parachinensis L.).

Salinity represents a serious environmental threat to crop production and by extension, to world food supply, social and economic prosperity of the developing world. Salicylic acid (SA) is an endogenous plant signal molecule involved in regulating various plant responses to stress. In the present study, we characterized the regulatory role of exogenous SA for their ability to ameliorate deleterious effects of salt stress (0, 100, 150, 200 mM NaCl) in choysum plants through coordinated induction of antioxidants, ascorbate glutathione (AsA-GSH) cycle, and the glyoxalase enzymes. An increase in salt stress dramatically declined root and shoot growth, leaf chlorophyll and relative water content (RWC), subsequently increased electrolyte leakage (EL) and osmolytes accumulation in choysum plants. Salt stress disrupted the antioxidant and glyoxalase defense systems which persuaded oxidative damages and carbonyl toxicity, indicated by increased H2O2 generation, lipid peroxidation, and methylglyoxal (MG) content. However, application of SA had an additive effect on the growth of salt-affected choysum plants, which enhanced root length, plant biomass, chlorophyll contents, leaf area, and RWC. Moreover, SA application effectively eliminated the oxidative and carbonyl stress by improving AsA and GSH pool, upregulating the activities of antioxidant enzymes and the enzymes associated with AsA-GSH cycle and glyoxalase system. Overall, SA application completely counteracted the salinity-induced deleterious effects of 100 and 150 mM NaCl and partially mediated that of 200 mM NaCl stress. Therefore, we concluded that SA application induced tolerance to salinity stress in choysum plants due to the synchronized increase in activities of enzymatic and non-enzymatic antioxidants, enhanced efficiency of AsA-GSH cycle and the MG detoxification systems.

Possible role of HMA4a TILLING mutants of Brassica rapa in cadmium phytoremediation programs.

Cadmium (Cd) is a dangerous transition element that causes environmental and health problems due to its high mobility in the soil-plant system. In plants, Cd causes serious alterations in physiological processes, affecting different vital functions such as photosynthesis. Species such as Brassica juncea and Brassica rapa have been selected as suitable plants for phytoremediation purposes due to their ability to tolerate the toxic effect of heavy metals. In order to improve this strategy, techniques of plant mutagenesis such as TILLING (Targeting Induced Local Lessions in Genomes) have been employed. In the present work we studied the role of the HMA4 gene in the tolerance to Cd toxicity (100 µM CdCl2) using a TILLING mutant of B. rapa (BraA.hma4a-3). These mutant plants presented a lower biomass reduction and a higher Cd concentration in leaves. An increase in the GSH/GSSG ratio, in the content of photosynthetic pigments and a reduction of oxidative stress was observed, as well as a better photosynthetic index, confirming that BraA.hma4a-3 plants showed a higher tolerance to Cd. In conclusion, according to the results obtained in this work, BraA.hma4a-3 plants could be used for phytoremediation purposes of Cd contaminated soils.

Nickel oxide nanoparticles cause substantial physiological, phytochemical, and molecular-level changes in Chinese cabbage seedlings.

Nickel oxide nanoparticles (NiO NPs) are utilized in various industries and their release into the environment may lead to the pollution of agricultural areas. However, assessing the toxicity of NiO NPs in major food crops is difficult due to the limited information available on their toxicity. The present investigation was carried out to evaluate how NiO NPs affect plant growth, photosynthetic efficiency, and phytochemical content, as well as changes at the transcriptional level of these phytochemicals in Chinese cabbage seedlings. Chlorophyll, carotenoid, and sugar contents were reduced, while proline and the anthocyanins were significantly upregulated in NiO NPs-treated seedlings. The levels of malondialdehyde, hydrogen peroxide, and reactive oxygen species, as well as peroxidase (POD) enzyme activity, were all enhanced in seedlings exposed to NiO NPs. The levels of glucosinolates and phenolic compounds were also significantly increased in NiO NPs-treated seedlings compared to control seedlings. The expression of genes related to oxidative stress (CAT, POD, and GST), MYB transcription factors (BrMYB28, BrMYB29, BrMYB34, and BrMYB51), and phenolic compounds (ANS, PAP1, and PAL) were significantly upregulated. We suggest that NiO NPs application stimulates toxic effects and enhances the levels of phytochemicals (glucosinolates and phenolic compounds) in Chinese cabbage seedlings.

A New Model Describing Copper Dose⁻Toxicity to Tomato and Bok Choy Growth in a Wide Range of Soils.

Phytotoxicity thresholds for heavy metals are derived from dose⁻response curves, which show the relationships between exposure dose and toxicity response. However, the results of tests or observations are commonly based on total heavy metal concentration, not the exposure dose that causes phytotoxicity; additionally, the phytotoxicity response differs with plant species. In the present study, the ethylenediaminetetraacetic acid (EDTA)-extractable copper (Cu) concentration was determined in order to evaluate Cu extractability. As two important horticultural food crops in Asia, tomato (Lycopersicon esculentum 'Meifen No. 1') and bok choy (Brassica rapa var. chinensis 'Susheng 28') were used to investigate Cu phytotoxicity in a wide range of Chinese soils with and without leaching treatment, after which relationships between Cu phytotoxicity thresholds based on EDTA-extractions and soil properties were established. The phytotoxicity thresholds showed that biomass of bok choy was more sensitive to Cu than tomato. Multiple linear regression analyses showed that soil factors, including organic carbon (OC), citrate dithionate extractable manganese (CD-Mn), cation exchange capacity (CEC), and CaCO3 explained over 85% of the variance in Cu phytotoxicity thresholds. The EDTA-extractable Cu dose⁻response relationships were further improved by incorporating soil properties. The new phytotoxicity predictive models indicated soil properties (soil pH, OC, CEC, and oxalate-extractable Mn) and EDTA-extractable Cu concentration explained more than 90% of the variance in the phytotoxicity response of tomato and bok choy biomass. The new phytotoxicity predictive models could be used to develop a reasonable remediation strategy for contaminated soils.

Phytoremediation of mixed contaminated soil enhanced with electric current.

Brassica rapa is a plant species that can germinate and grow in mixed contaminated soil with PAH and metals (Cr, Pb and Cd). This plant was selected among 14 plant species for electro-phytoremediation tests because its fast germination and growth in contaminated soil. The influence of type of the electric field (AC, DC) and mode of application (continuous, periodic and polarity inversion) was studied in the electro-phytoremediation tests. The application of 1 ACV/cm potential gradient around B. rapa resulted in the effective elimination of anthracene and phenanthrene, but only minor metal removal. The results of this work suggest that alternating current (AC) may be the most suitable electric field for large scale applications. The spatial configuration of electrodes affects the distribution of the electric field in the soil. Various spatial distribution of electrodes have been tested and it has been identified that parallel anodes and cathodes on the soil surface are the most appropriate configuration for field scale applications. Other configurations can be used to concentrate the contaminant around the growing pant or to transport the contaminants from deep soil layers to the rhizosphere.

Calcium ameliorates the toxicity of sulfate salinity in Brassica rapa.

Salinity stress in Brassica, often only associated with osmotic effects and the toxicity of Na+, was more severe when applied as Na2SO4 than as NaCl, indicating that SO42- ions had toxic effects as well. Application of 10 mM calcium in the form of CaCl2 in the growth medium of plants only slightly ameliorated growth impairment by NaCl and KCl, but almost completely prevented negative effects of Na2SO4 and K2SO4 on plant biomass production. This effect was calcium specific, as MgCl2 ameliorated sulfate toxicity to a much lower extent. This sulfate toxicity coincided with a strong decrease in the plant content of calcium and manganese upon sulfate salinity. Application of CaCl2 largely alleviated this decrease, however, it did not prevent the higher tissue concentration of sulfate. CaCl2 prevented the increase in organic sulfur compounds presumably by reducing of relative gene expression of ATP-sulfurylase (ATPS) and adenosine 5'-phosphosulfate reductase (APR) indicating a possible regulation of sulfate assimilation by calcium. The upregulation of the genes encoding for Group 4 sulfate transporters (Sultr4;1 and 4;2) upon sulfate salinity, was absent in the presence of CaCl2. Therefore, additional calcium may facilitate an increased vacuolar capacity for sulfate accumulation.

Eugenol Confers Cadmium Tolerance via Intensifying Endogenous Hydrogen Sulfide Signaling in Brassica rapa.

Eugenol, a plant-derived small compound, shows great medicinal potential. However, whether and how eugenol regulates crop physiology remains elusive. Here we reported that eugenol induced Cd (cadmium) tolerance in the root of Brassica rapa. Roots were treated with eugenol and CdCl2 simultaneously (eugenol + Cd) or pretreated with eugenol followed by CdCl2 treatment (eugenol → Cd). Eugenol significantly attenuated Cd-induced growth inhibition, ROS accumulation, oxidative injury, and cell death, which were confirmed by in vivo histochemical analysis. Eugenol remarkably decreased free Cd2+ accumulation in root. Eugenol intensified GSH (glutathione) accumulation in roots upon CdCl2 exposure, which explained the decrease in free Cd2+ and attenuation of oxidative injury. Eugenol stimulated endogenous H2S (hydrogen sulfide) generation by upregulating the expression of BrLCD ( l-cysteine desulfhydrase) and BrDCD ( d-cysteine desulfhydrase) as well as their enzymatic activities in CdCl2-treated root. Application of H2S biosynthesis inhibitor or H2S scavenger led to the decrease in endogenous H2S level in Cd-treated root, which further compromised all the above effects of eugenol. These findings suggested that eugenol triggered H2S → GSH signaling cassette in plants to combat Cd stress, which shed new light on eugenol-modulated plant physiology and the interaction between eugenol and H2S.

Hazard assessment of the veterinary pharmaceuticals monensin and nicarbazin using a soil test battery.

Veterinary pharmaceuticals are widely used as food additives in the poultry industry, and the unknown consequences of releasing these compounds into the environment are of concern. The purpose of the present study was to determine the direct impact of 2 veterinary pharmaceuticals (nicarbazin and monensin), commonly used in the poultry industry, on nontarget invertebrates and plant species. Ecotoxicological tests were used to evaluate the acute and chronic toxicity in earthworms (Eisenia andrei), collembolans (Folsomia candida), and 2 plant species (Brassica rapa and Triticum aestivum). Chemical analytical measurements were in good agreement with the nominal concentrations used, although some variability was seen. The results obtained showed no effects of nicarbazin at the highest nominal tested concentration of 1000 mg a.i./kg soil dry weight on any of the organisms, whereas exposure to monensin caused a concentration-specific response pattern. Species sensitivity to monensin decreased in the following rank order: B. rapa > T. aestivum > E. andrei > F. candida, with measured median effect concentrations (based on soil exposure) ranging between approximately 10 and 120 mg/kg. Our results emphasize the importance of using a test battery when assessing ecotoxicological effects by using different ecophysiological endpoints and species from different trophic levels. Environ Toxicol Chem 2018;37:3145-3153. © 2018 SETAC.

Inoculation of plant growth-promoting bacteria Bacillus sp. YM-1 alleviates the toxicity of Pb to pakchoi.

Heavy metal accumulation in plants may imperil human health. Inoculation of plant growth-promoting bacteria can alleviate the toxicity of heavy metal and promote plant growth. In this study, Bacillus sp. YM-1, a heavy metal resistant and plant growth-promoting bacterium, was immobilized with spent substrate of mushroom and applied to alleviate the toxicity of Pb to pakchoi. The results indicated that the biomass of pakchoi in inoculation group was increased by 17.45 to 27.05% compared with that in non-inoculated group (p < 0.05). The root and shoot were lengthened by 13.45% to 39.17% and 20.23% to 42.36%, respectively. The content of Pb in root and shoot obviously reduced and that in edible part (shoot) was less than 0.2 mg kg-1 in the low concentration of Pb. Other indicators such as superoxide dismutase (SOD), peroxidase (POD), chlorophyll, and protein all testified that YM-1 inoculation was conducive to the alleviation of Pb toxicity to pakchoi.