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How nitrogen (N) supply affects the induced defense of plants remains poorly understood. Here, we investigated the impacts of N supply on the defense induced in maize (Zea mays) against the fall armyworm (Spodoptera frugiperda). In the absence of herbivore attack or exogenous jasmonic acid (JA) application, N supply increased plant biomass and enhanced maize nutrient (soluble sugar and amino acid) contents and leaf area fed by S. frugiperda (the feeding leaf area of S. frugiperda larvae in maize supplemented with 52.2 and 156.6 mg/kg of N was 4.08 and 3.83 times that of the control, respectively). When coupled with herbivore attack or JA application, maize supplemented with 52.2 mg/kg of N showed an increased susceptibility to pests, while the maize supplemented with 156.6 mg/kg of N showed an improved defense against pests. The changes in the levels of nutrients, and the emissions of volatile organic compounds (VOCs) caused by N supply could explain the above opposite induced defense in maize. Compared with herbivore attack treatment, JA application enhanced the insect resistance in maize supplemented with 156.6 mg/kg of N more intensely, mainly reflecting a smaller feeding leaf area, which was due to indole emission and two upregulated defensive genes, MPI (maize proteinase inhibitor) and PAL (phenylalanine ammonia-lyase). Hence, the optimal N level and appropriate JA application can enhance plant-induced defense against pests.

Background To enhance discovering efficiency of new herbicidal compounds, a strategy for rapidly screening out strongly herbicidal chemical components from natural resources is necessary. Results Seventeen essential oils selected from 14 Eucalyptus species and hybrids were evaluated for their herbicidal activities on annual ryegrass. A feasible strategy was established for rapidly pinpointing the chemicals contributing to strong herbicidal activities without the process of isolation and purification of individual compounds. This strategy was based on gas chromatography-mass spectrometry (GC-MS) coupled with principal component analysis (PCA) and verified by the bioassay results using several individual compounds. Two strong herbicidal compounds trans-pinocarveol and α-terpineol were screened out using the strategy. The strong herbicidal activity of trans-pinocarveol was discovered for the first time. Conclusion The established strategy of screening herbicidal compounds from natural resources is simple, feasible and reliable. © 2019 Society of Chemical Industry.

Global climate change and decreases in available land are significant challenges that humans are currently facing. Alternative management approaches for sugarcane fields have great potential to help mitigate these problems in China. We hypothesized that soybean intercropping with reduced nitrogen input could increase crop productivity and reduce the carbon footprint (CF) of sugarcane fields in China. Therefore, a long-term field experiment from 2009 to 2017 in the Pearl River Delta of China was chosen to test this hypothesis. The results showed that the energy yields of sugarcane/soybean intercropping systems were 17.8%–39.4% higher than those of sugarcane monocropping systems. The energy yields of the same cropping systems using conventional and reduced N inputs (525 kg ha−1 and 300 kg ha−1) did not show a significant difference. Additionally, the CF values of the unit yield (CFY) for sugarcane/soybean intercropping were 3.2%–30.4% lower than those of the monocropping systems, showing the higher CF efficiency of the intercropping pattern, although the difference was not significant. The CF of the unit area (CFA) and the CFY of all the cropping patterns at the conventional N level were 19.5%–62.0% higher than that at the reduced N level, demonstrating that reducing the nitrogen input could significantly lower the CF of the sugarcane fields. In addition, the high N level cased negative effects in terms of increasing the crop productivity and reducing the CF of the soybean/sugarcane intercropping pattern. In conclusion, sugarcane/soybean intercropping with reduced N input improved crop productivity while lowering the CF of sugarcane fields in China. The sugarcane/soybean (1:2) intercropping with 300 kg N ha−1 system showed the best benefits in the Pearl River Delta of China. These advanced agricultural practices contributed to improved farmland use efficiency and clean production in an agricultural system.

Herein, a facile way to synthesize Cu nanoclusters (CuNCs) has been proposed while insulin played the role as a stabilizer. Specifically, this type of CuNCs existed in tunable diameters of 4–5 nm, and exhibited bright reddish-orange fluorescence with a quantum yield of 7.4 %. Interestingly, the fluorescence intensity of CuNCs could be obviously enhanced and more stable by introducing Eu3+. Moreover, this proposed Eu3+@CuNCs with low toxicity and near-infrared fluorescence may provide potential to broaden avenues for various applications in bioimaging and beyond.

Herein, an innovative and simple method for synthesizing carbon dots (CDs) with satisfactory fluorescence has been successfully established while rose flowers served as carbon source for the first time. Meanwhile, the fluorescence (FL) mechanism of current CDs was elucidated in detail by fluorescence, UV–vis, HR-TEM, and FTIR-based analyses. Subsequently, this type of CDs was employed for detecting tetracycline (TC) on the basis of the interactions between TC and CDs, and allowed quenching their fluorescence. Moreover, the proposed analytical strategy permitted detecting TC in a linear range of 1.0×10−8−1.0×10−4 mol/L with a detection limit of 3.3×10−9 mol/L at a signal-to-noise ratio of 3. Significantly, the CDs described here were further applied for fluorescent coding, demonstrating their promising future towards various applications in analytic science.

L -Cysteine, serving as both a reducing agent and stabilizer, was employed for synthesis of gold nanoclusters (AuNCs) in aqueous solution. The AuNCs existed in sizes of 3-5 nm, and emitted yellow-green fluorescence under UV light. Subsequently, the AuCNs prepared here were applied for detections of Cu2+ on the basis of interactions between Cu2+ and the groups of the AuCNs, which lead to the fluorescence quenching of the AuCNs, and can be used for detection of Cu2+ in the real samples (urine). In addition, the fluorescence of AuNCs-Cu2+ complex will recover while doxycycline(DC) were introduced, mainly due to the more intensive interactions between Cu2+ and DC, thus this complex were employed as a fluorescent probe for assaying DC. Moreover, the optimal conditions for sensing both Cu2+ and DC have also been explored, and the results showed favorable liner relationships and satisfactory recoveries. Significantly, this new fluorescent probe was used for determining DC in milk samples, demonstrating its practical value. Therefore, the current AuCNs implied potential of broadening avenues for analyzing both Cu2+ and DC.

Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while l -cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg 2+ on the basis of the interactions between Hg 2+ and l -cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg 2+ in a linear range of 1.0 × 10 −7 mol L −1 × 10 −3 mol L −1 , with a detection limit of 2.4 × 10 −8 mol L −1 at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications.

An innovative and green strategy to synthesize carbon dots (CDs) with a quantum yield (QY) of nearly 19.8% has been successfully established for the first time. Subsequently, the possible fluorescence (FL) mechanism was elucidated by fluorescence, UV-vis, high resolution transmission electron microscope (HR-TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Significantly, not only the precursor of CDs and whole synthesis procedure was green, but also the CDs obtained here exhibited various advantages including high fluorescent QY, excellent photostability, non-toxicity and satisfactory stability. Additionally, the CDs were employed for assaying Fe(3+) based on direct interactions between Fe(3+) and − COOH, − OH and − NH2 of CDs, resulting in aggregations that facilitate to quench their fluorescence. The decrease of fluorescence intensity permitted detections of Fe(3+) in a linear range of 5.0 × 10(-9)-1.0 × 10(-4)mol/L, with a detection limit of 1.7 × 10(-9)mol/L at a signal-to-noise ratio of 3, suggesting a promising assay for Fe(3+). Eventually, the CDs were applied for cell imaging and coding, demonstrating their potential towards diverse applications.

Cultivation of genetically modified maize (Zea mays L.) expressing the Cry1Ab protein from Bacillus thuringiensis (Bt) has increased worldwide since Bt maize was first commercialised. However, the cultivation and return of Bt maize has been shown to affect nontarget symbiotic soil-borne microbes such as arbuscular mycorrhizal fungi (AMF). In this study, we compared the diversity and composition of the AMF communities between two Bt maize plants (5422Bt1 [event Bt 11] and 5422CBCL [event MON 810]) and their conventional (non-Bt) isoline (5422) after cultivation for five seasons and return of straws by using molecular approaches, including terminal restriction fragment length polymorphism and DNA sequencing. Our data revealed that the diversities of AMF communities did not consistently differ significantly in soils and roots of subsequently planted conventional maize (SCM 5422) grown with Bt maize straw at three sampling stages (seedling, large bell, and maturity stages). DNA sequencing showed that typical AMF communities included Glomus, Paraglomus, Diversispora, Acaulospora, and Rhizophagus, of which Glomus was the most abundant. Funneliformis was detected only in bulk and rhizospheric soils and in roots of maize at the seedling stage. Rhizophagus was detected only in rhizospheric soils and only at the maturity stage. No significant effects related to the presence of Bt maize straw (5422Bt1 or 5422CBCL) were found by general linear analysis. However, plant growth stage had a greater influence on AMF diversity than Bt traits. In conclusion, cultivation of non-Bt maize on soils previously cultivated with Bt maize for five seasons had minor effects on AMF communities.

Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) in combination with sequencing of amplified partial 18S ribosomal DNA was used to assess the effects of transgenic Bt corn 5422Bt1 (event Bt 11) and 5422CBCL (event MON810) on the community structure of a non-target microorganism, namely the arbuscular mycorrhizal fungi (AMF) Glomus in corn roots and rhizosphere soils, relative to their non-Bt isolines 5422 (conventional parent) and 5422wx (conventional hybrid). AMF colonization in roots of different corn genotypes was also assessed using microscopic visualization. No adverse effect was detected on the indigenous AMF colonization of the roots of Bt hybrids 5422Bt1 and 5422CBCL. Two-way indicator species analysis (TWINSPAN®) and detrended correspondence analysis (DCA) of the DGGE data from corn roots presented differences between Bt and non-Bt corn isolines (5422Bt1 vs. 5422wx, and 5422CBCL vs. 5422wx). However, differences were also recognized between the two non-Bt corn cultivars (5422 vs. 5422wx), and between the two Bt corn lines (5422Bt1 vs. 5422CBCL) in roots. Our results suggest that corn genotypes may have a greater influence on the AMF community structure of plant roots and rhizosphere soils than other factors, such as the age of the growing plants.

Earthworms Eisenia fetida, bred in substances with stover of two genetically-engineered Bacillus thuringiensis (Bt) corns (5422Bt1 (Event Bt11) and 5422CBCL (MON810)) expressing Cry1Ab and their near-isogenic non-Bt corn (5422), were used to investigate the non-target effects of Bt corn on soil-dwelling organisms. Cry1Ab concentrations in substances, casts and guts of E. fetida were also investigated by Enzyme-linked immunosorbent assay (ELISA). More than 90% individuals of E. fetida survived over a period of 30 d, irrespective of whether they received Bt corn or non-Bt corn. Compared to 5422 treatments, significantly higher relative growth rate and more number of new offspring and cocoons of E. fetida were found in 5422Bt1 and 5422CBCL treatments. These results were unlikely to be directly caused by Cry1Ab released from Bt corns but rather by differences in other factors of plants such as plant components (soluble sugar, total organic carbon, total protein and available phosphorus of Bt corns were more than 5422). ELISA results indicated immunoreactive Cry1Ab was detectable in substances, and the casts, guts of E. fetida from Bt corns treatments, of which the highest levels were detected in substances under the corresponding experimental conditions. With the increase of treated time, a strong decline was observed in Cry1Ab from substances and casts of E. fetida, whereas Cry1Ab in guts of E. fetida from 5422Bt1 treatments gradually increased and that from 5422CBCL treatments increased between 14 and 30 d. Therefore, the presence of Cry1Ab in E. fetida had no deleterious effects on their growth and reproduction.

We investigated the effects of soil temperature (15 °C, 25 °C, 35 °C), water content (20%, 33%, 50%) and pH (4.5, 7.0, 9.0) on the degradation of Cry1Ab protein released from the straw of Bt corn varieties 34B24 and 1246 × 1482 both expressing Cry1Ab protein. Our results showed that Cry1Ab protein released from both 34B24 and 1246 × 1482 straw was degraded in a similar way in all treatments, which demonstrated a rapid decline in the early stage but a slow decline in the middle and late stages. In the late stage (180 days after the experiment commenced) 0.03%–1.51% and 0.02%–0.91% of initial Cry1Ab protein released from 34B24 and 1246 × 1482 straw was detected in soil. In addition, degradation dynamics of Cry1Ab protein under different environmental conditions was well described by the shift-log model. DT 50 of Cry1Ab protein released from 34B24 and 1246 × 1482 straw was 0.97–9.97 d and 0.75–10.89 d, respectively, and DT 90 was 4.66–162.45 d and 6.44–57.46 d, respectively. The results suggested that soil temperature had significant effects on the degradation of Cry1Ab protein, with a higher degradation rate at higher temperature, but soil water content and pH had no obvious effects on the degradation of Cry1Ab protein.

Polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) and sequences of the 16S and 18S rRNA genes were used to access the effects of actively growing Bacillus thuringiensis (Bt) corn Pioneer 34B24 and Nongda 1246*1482, and plant straw (leaves plus stalks) of Bt hybrid Pioneer 34B24 and Nongda 61 on soil bacterial and fungal communities. Two-way indicator species analysis (TWINSPAN®), and detrended correspondence analysis (DCA) of the DGGE data indicated that neither the actively growing Bt corn nor its straw had any constant apparent effect on the soil bacteria and fungi community structure. The age of the growing plants, or the timing of plant straw decomposition may have more effect on the microbial community than other factors, i.e., the presence of Cry protein, plant hybrid and variety.

Bt corn is one of the top three large-scale commercialized transgenic crops around the world. It is increasingly clear that the complementary durable approaches for pest control, which combine the endogenous defense of the crop with the introduced foreign genes, are promising alternative strategies for pest resistance management and the next generation of insect-resistant transgenic crops. In the present study, we tested the inducible effects of exogenous jasmonic acid (JA) on direct-defense chemical content, Bt protein concentration, and related gene expression in the leaves of Bt corn cultivar 34B24 and non-Bt cultivar 34B23 by chemical analysis, ELISA, and RT-PCR. The results show that the expression of LOX, PR-2α, MPI, and PR-1 genes in the treated leaf (the first leaf) was promoted by exogenous JA both in 34B24 and 34B23. As compared with the control, the concentration of DIMBOA in the treated leaf was significantly increased by 63 and 18% for 34B24 and 34B23, respectively. The total phenolic acid was also increased by 24 and 12% for both 34B24 and 34B23. The Bt protein content of 34B24 in the treated leaf was increased by 13% but decreased significantly by 27% in the second leaf. The induced response of 34B24 was in a systemic way and was much stronger than that of 34B23. Those findings indicated that there is a synergistic interaction between Bt gene and internally induced chemical defense system triggered by externally applied JA in Bt corn.

By employing attractive performance of fluorescent carbon dots, we herein successfully established an assay for analyzing bacteria firstly. Specifically, carbon dots with blue fluorescence were initially synthesized according to a previous report, and modified with vancomycin on their surfaces. Subsequently, the prepared carbon dots were applied to detect Staphylococcus aureus accompanied with a linear range of 3.18×105–1.59×108 cfu/mL as well as a detection limit of 9.40×104 cfu/mL. Compared with other regular methods, our method is more rapid and convenient in term of methodology. Meanwhile, the current strategy was applied for detection of other bacteria including Bacillus subtilis, Listeria monocytogenes, Salmonella, Pseudomonas aeruginosa and Escherichia coli, and the modified carbon dots showed obvious affinity with Gram-positive bacteria owing to the ligand–receptor interactions between vancomycin and the cell walls, suggesting its value for detecting Gram-positive bacteria. Additionally, the practicability of this sensing approach was validated by recovery experiments conducted in orange juice, confirming its potential to broaden avenues for detection of Gram-positive bacteria.

Herein, a novel strategy for synthesizing fluorescent carbon nanoparticles (CPs) with a quantum yield of approximately 7.1% has been well established by mixing l-cysteine, diphosphorus pentoxide and water. Compared with other current protocols, the method described here displayed various advantages including friendly manipulations, low cost, and rapid reactions. Subsequently, we applied the CPs prepared here for detections of tetracyclines (TCs). Briefly, the fluorescence intensity of CPs was quenched once TCs were introduced. Based on this phenomenon, TCs were analyzed respectively accompanyed with satisfactory detection limits and linear ranges. Significantly, the practicability of this sensing method was further validated by assaying TC in human urine samples and pharmaceutical preparations, confirming its potential to broaden avenues for detecting TCs. Additionally, the CPs could serve as fluorescent powder and ink followed by a simple post-treatment, suggesting their promising applications.

Tetracycline and Eu 3+ , while coexisting, usually appear as a complex by chelating. This complex shows low fluorescence intensity, leading to its limitation of analytical goals. Gold nanoclusters (AuNCs), emerging as novel nano-material, are attracting increasing attentions in multiple fields. Herein, gold nanoclusters first function as a fluorescence-enhanced reagent rather than a conventional fluorescent-probe, and a dramatic enhanced-fluorescence system was built based on Eu 3+ –Tetracycline complex (EuTC) by introducing gold nanoclusters. Simultaneously, three types of gold nanoclusters were employed for exploring various conditions likely affecting the system, which demonstrate that no other gold nanoclusters than DNA-templated gold nanoclusters enormously caused fluorescence-enhancement of EuTC. Moreover, this enhanced-fluorescence system permitted available detection of tetracycline (TC) in a linear range of 0.01–5 μM, with a detection limit of 4 nM at a signal-to-noise ratio of 3. Significantly, the practicality of this method for detection of TC in human urine and milk samples was validated, demonstrating its advantages of simplicity, sensitivity and low cost. Interestingly, this system described here is probably promising for kinds of applications based on its dramatically enhanced-fluorescence.

Allelopathy arises from the release of chemicals by one plant species that affect other species in its vicinity, usually to their detriment. Allelopathic effects have been demonstrated to be limiting factors for species distributions and ecological processes in some natural or agricultural communities. Based on the biphasic hormetic responses of plants to allelochemicals, ecological-limiting-factor models were introduced into the An-Johnson-Lovett hormesis model to improve modelling the phenomenon of allelopathic hormesis and to better reflect the nature of allelopathy as a limiting factor in ecological processes. Outcomes of the models have been compared for several sets of experimental data from the literature and good agreement between the models and data was observed, which indicates that the new models give some insight into the ecological mechanisms involved and may provide more options for modelling the allelopathic phenomenon as well as platforms for further research on plant allelopathic hormesis.

An incubation test with the straws of Bt corn 34B24 and its non-transgenic isogenic line 34B23, Bt corn Nongda 61, and non-transgenic Nongda 3138 was conducted to study the potential effects of Bt corn straw decomposition on soil enzyme activities and soil fertility. No significant difference in soil protease and acid phosphatase activities was found between treatments 34B24 and 34B23; but on day 75 of incubation, soil dehydrogenase activity was significantly higher in treatment 34B24 than in treatment 34B23. The same was true for soil invertase activity on days 15,45, 60 and 75. Soil urease activity in treatment 34B24 was significantly increased on day 30, but decreased on days 45 and 75. A significant difference in several soil enzyme activities was also observed between the treatments of two Bt corn hybrids and their conventional cultivars at some sampling days. After incubation for 90 days, the contents of soil available P and K were significantly lower in treatment 34B24 than in treatment 34B23. The differences mentioned above resulted from the composition of test corn straws, which may be affected by the Bt gene transformation process. In order to accurately assess the effects of Bt corn straw decomposition on soil ecosystem, a standard classification system of soil enzyme activities should be established for different soil types from different regions.

The effects of transgenic crops on the soil ecosystem were reviewed. The activity of Cry I Ab gene and proteinase inhibitor gene in the soil was summarized. The differences of soil microbes' components, soil enzyme activities, and soil fauna between genetic crops and isogenic strain crops were analyzed. According to current progress, the potential impacts of transgenic plant on soil microorganisms depend on the characteristics of the gene transferred into the crops and the soil properties. The change of soil ecosystem affected by many factors, and among them, the complex and stability of the ecosystem are the most important. The ecological effects of transgenic crops on the soil ecosystem need to be evaluated more fully before they are planted over extensive areas. Much effort should be devoted to the development of molecular techniques method to assess the effects of transgenic crops on soil ecosystem.