A multifunctional sensor for detecting tetracycline, 4-nitrophenol, and pesticides.

In recent years, due to the abuse of antibiotics, nitro explosives and pesticides, which have caused great harm to the environment and human health, social concerns have prompted researchers to develop more sensitive detection platforms for these pollutants. In this paper, a novel two-dimensional Zn (II) coordination polymer, [Zn(L)0.5(1,2-bimb)]·DMF (1), [H4L=[1,1':4',1''-terphenyl]-2, 2'',4, 4'' -tetracarboxylic acid, 1,2-bimb = 1,2-bis(imidazol-1-ylmethyl)benzene] was synthesized using a hydro-solvothermal method. Among commonly used organic solvents, 1 exhibits significant stability. Fast and efficient fluorescence response can be achieved for tetracycline (TET), 4-nitrophenol (4-NP), fluazinam (FLU), and abamectin benzoate (AMB) with low detection limits. A binary intelligent logic gate device with FLU and AMB as chemical input signals is successfully constructed, which provides a new idea for biochemical detection. In addition, a portable visual test paper has been prepared, which has high sensitivity, good selectivity, and simple operation. It can be used for rapid detection of pollutants in daily life and has broad application prospects. Finally, a detailed discussion was conducted on the fluorescence sensing mechanism of 1 for detecting TET, 4-NP, AMB and FLU.

Unraveling the role of Mn(V)/Mn(III) in the enhanced permanganate oxidation under Vis-LED radiation.

A novel approach of visible light-emitting diode (Vis-LED) radiation was employed to activate permanganate (Mn(VII)) for efficient organic micropollutant (OMP) removal. The degradation rates of OMPs by Vis-LED/Mn(VII) were 2-5.29 times higher than those by Mn(VII) except for benzoic acid and atrazine. Increasing wavelengths (445-525 nm) suppressed the degradation of diclofenac (DCF) and 4-chlorophenol (4-CP) owing to the decreased quantum yields of Mn(VII). Comparatively, light intensity and Mn(VII) dosage had a positive effect on the degradation of DCF and 4-CP. Experimental data revealed that Mn(V) dominated the DCF degradation whereas Mn(III) was the active oxidant in the 4-CP degradation. Mn(V) and Mn(III) formed from the photo-decomposition of Mn(VII), meanwhile, Mn(III) also formed from the Mn(V) photo-decomposition. The increase in solution pH inhibited DCF degradation but had a positive impact on 4-CP degradation, mainly due to the changing speciation of DCF and 4-CP. Inorganic anions (Cl- and HCO3-) had little impact on DCF and 4-CP degradation, while humic acid (HA) showed a positive impact because of the π-π interaction between HA and DCF/4-CP. The transformation products of DCF and 4-CP were identified and transformation pathways were proposed. Finally, the Vis-LED/Mn(VII) exhibited great degradation performance in various authentic waters. Overall, this study boosts the development of Mn(VII)-based oxidation processes.

Matching periodate peak absorbance by far UVC at 222 nm promotes the degradation of micropollutants and energy efficiency.

Periodate (PI)-based advanced oxidation processes have gained increasing interest. This study for the first time elevates the light-activation capacity of PI by using far UVC at 222 nm (UV222/PI) without extra chemical inputs. The effectiveness and the underlying mechanisms of UV222/PI for the remediation of micropollutants were studied by selecting atenolol (ATL) as a representative. PI possessed a high molar absorption coefficient of 9480-6120 M-1 cm-1 at 222 nm in the pH range of 5.0-9.0, and it was rapidly decomposed by UV222 with first-order rate constants of 0.0055 to 0.002 s-1. ATL and the six other organic compounds were effectively degraded by the UV222/PI process under different conditions with the fluence-based rate constants generally two to hundred times higher than by UVA photolysis. Hydroxyl radical and ozone were confirmed as the major contributors to ATL degradation, while direct photolysis also played a role at higher pH or lower PI dosages. Degradation pathways of ATL were proposed including hydroxylation, demethylation, and oxidation. The high energy efficiency of the UV222/PI process was also confirmed. This study provides a cost-effective and convenient approach to enhance PI light-response activity for the treatment of micropollutants.

Photo-assisted natural chalcopyrite activated peracetic acid for efficient micropollutant degradation.

The effective activation of natural chalcopyrite (CuFeS2) on peracetic acid (PAA) to remove organic micropollutants was studied under visible light irradiation. Results showed than an effective sulfamethoxazole (SMX) degradation (95.0 %) was achieved under visible light irradiation for 30 min at pH 7.0. Quenching experiments, electron spin resonance analysis, and LC/MS spectrum demonstrated that HO• and CH3C(O)OO• were the main reactive species for SMX degradation, accounting for 43.3 % and 56.7 % of the contributions, respectively. Combined with X-ray photoelectron spectroscopy analysis, the photoelectrons generated on CuFeS2 activated by visible light enhanced the Fe3+/Fe2+ and Cu2+/Cu+ cycles on the surface, thereby activating PAA to generate HO•/CH3C(O)OO•. The removal rate of SMX decreased with the increase in wavelengths, due to the formation of low energy photons at longer wavelengths. Besides, the optimal pH for degradation of SMX by CuFeS2/PAA/Vis-LED process was neutral, which was attributed to the increasing easily activated anionic form of PAA during the increase in pH and the depletion of Fe species at alkaline conditions. Cl-, HCO3-, and HA slightly inhibited SMX degradation because of reactive species being quenched and/or shielding effect. Furthermore, the degradation efficiency of different pollutants by CuFeS2/PAA/Vis-LED was also measured, and the removal efficiency was different owing to the selectivity of CH3C(O)OO•. Finally, the process exhibited good applicability in real waters. Overall, this study provides new insight into visible light-catalyzed activation of PAA and suggests on further exploration of the intrinsic activation mechanism of PAA.

Research Progress on Plant Responses to Stress Combinations in the Context of Climate Change.

In the context of climate change, the frequency and intensity of extreme weather events are increasing, environmental pollution and global warming are exacerbated by anthropogenic activities, and plants will experience a more complex and variable environment of stress combinations. Research on plant responses to stress combinations is crucial for the development and utilization of climate-adaptive plants. Recently, the concept of stress combinations has been expanded from simple to multifactorial stress combinations (MFSCs). Researchers have realized the complexity and necessity of stress combination research and have extensively employed composite gradient methods, multi-omics techniques, and interdisciplinary approaches to integrate laboratory and field experiments. Researchers have studied the response mechanisms of plant reactive oxygen species (ROS), phytohormones, transcription factors (TFs), and other response mechanisms under stress combinations and reached some generalized conclusions. In this article, we focus on the research progress and methodological dynamics of plant responses to stress combinations and propose key scientific questions that are crucial to address, in the context of plant responses to stress assemblages, conserving biodiversity, and ensuring food security. We can enhance the search for universal pathways, identify targets for stress combinations, explore adaptive genetic responses, and leverage high-technology research. This is in pursuit of cultivating plants with greater tolerance to stress combinations and enabling their adaptation to and mitigation of the impacts of climate change.

Effects of Six Consecutive Years of Irrigation and Phosphorus Fertilization on Alfalfa Yield.

Alfalfa (Medicago satiua L.) is a major forage legume in semi-arid regions such as North China Plain and is the material foundation for the development of herbivorous animal husbandry. How to improve the yield of alfalfa per unit area from a technical perspective and achieve high-yield cultivation of alfalfa is the focus of research by scientific researchers and producers. To evaluate the effects of irrigation and P fertilization as well as the P residual effect on alfalfa yield, we conducted a six-year (2008-2013) field experiment in loamy sand soil. There were four irrigation levels (W0: 0 mm, W1: 25 mm, W2: 50 mm, W3: 75 mm per time, four times a year) and three P fertilization levels (F0: 0 kg P2O5 ha-1, F1: 52.5 kg P2O5 ha-1, F2: 105 kg P2O5 ha-1 per time, twice a year). The highest dry matter yield (DMY) was obtained in the W2F2 treatment, with an annual mean of 13,961.1 kg ha-1. During 2009-2013, the DMY of first and second-cut alfalfa increased significantly with increasing irrigation levels, whereas the opposite pattern was observed in fourth-cut alfalfa. Regression analysis revealed that the optimal amount of water supply (sum of seasonal irrigation and rainfall during the growing season) to obtain maximum DMY was between 725 and 755 mm. Increasing P fertilization contributed to significantly higher DMY in each cut of alfalfa during 2010-2013 but not in the first two growing seasons. The mean annual DMY of W0F2, W1F2, W2F2, and W3F2 treatments was 19.7%, 25.6%, 30.7%, and 24.1% higher than that of W0F0 treatment, respectively. When no P fertilizer was applied in F2 plots in 2013, soil availability and total P concentrations, annual alfalfa DMY, and plant nutrient contents did not differ significantly compared with those in fertilized F2 plots. Results of this study suggest that moderate irrigation with lower annual P fertilization is a more environmentally sound management practice while maintaining alfalfa productivity in the semi-arid study area.

MOFs-based Fe@YAU-101/GCE electrochemical sensor platform for highly selective detecting trace multiplex heavy metal ions.

The construction of sensors with specific recognition functions can easily, sensitively and efficiently detect heavy metal ions, which is a demand in the field of electrochemical sensing and an important topic in the detection of environmental pollutants. An electrochemical sensor based on MOFs composites was developed for sensing of multiplex metal ions. The large surface area, adjustable porosities and channels in MOFs facilitate successful loading of sufficient quantities highly active units. The active units and pore structures of MOFs are regulated and synergetic with each other to enhance the electrochemical activity of MOFs composites. Thus, the selectivity, sensitivity and reproducibility of MOFs composites have been improved. Fortunately, after characterization, Fe@YAU-101/GCE sensor with strong signal was successfully constructed. In the presence of target metal ions in solution, the Fe@YAU-101/GCE can efficiently and synchronously identify Hg2+, Pb2+, and Cd2+. The detection limits (LOD) are 6.67 × 10-10 M(Cd2+), 3.33 × 10-10 M(Pb2+) and 1.33 × 10-8 M (Hg2+), and are superior to the permissible limits set by the National Environmental Protection Agency. The electrochemical sensor is simple without sophisticated instrumentation and testing processes, hence promising for practical applications.

Herders' adaptation strategies and animal husbandry development under climate change: A panel data analysis.

The frequent occurrence of extreme climate events has become an indisputable fact. However, the role of adaptation to extreme climate change in the development of livestock husbandry is still insufficiently understood. This study empirically analyzed the impact of herders' adaptation strategies to extreme drought on livestock husbandry development and aimed to explore the optimal grassland management path under continuous climate change. A panel dataset of surveyed herders from the Xilingol League, a traditional pastoral area in China, was used. The results indicated that the average frequency of extreme drought in the Xilingol League from 1980 to 2020 was 4.94 months/year, and the occurrence of extreme drought showed a slightly upward trend. The average technical efficiency of livestock husbandry was 0.721, which can still be improved. Hay purchases can effectively promote livestock technical efficiency (p<0.01) and is the main adaptation strategy of herders to extreme drought. Further analysis showed that non-farming and pastoral employment has a positive regulatory effect in the impact of purchased hay on livestock technical efficiency. The results of this study deepen the understanding of effective adaptation to extreme weather events in pastoral areas due to climate change and provide useful information to policymakers engaged in grassland management.

Patterns and Drivers of Aboveground Insect Diversity along Ecological Transect in Temperate Grazed Steppes of Eastern Eurasian.

Insects are important components of biodiversity and play significant roles in the steppe ecosystem. They are abundant, easy to sample, and sensitive to changing conditions, making them useful indicators of environmental changes. This study aims to describe patterns (α and ß) of insect diversity across two steppe types (a typical steppe and a desert steppe) along the Eastern Eurasian Steppe Transect (EEST), as well as evaluate the effects of environmental variables in determining these patterns and the influence of plant diversity alterations on these effects. To this end, we collected 5244 individual insects and found an n-shaped diversity distribution along the latitudinal gradient and a significant difference in insect communities across the two steppe types. Further, the Mantel test and path analysis indicate that climate and grazing activities combine to influence insect diversity, and these effects are mediated through plant diversity, strongly supporting the role of bottom-up effects in situations of climatic and grazing pattern changes. Moreover, the contribution of plant diversity varied with steppe types and insect functional groups, with greater effects seen in the typical steppe and herbivorous insects. This indicated the importance of protecting species diversity in steppes through managing plant diversity and assessments of local environmental factors such as grazing intensity and temperature.

Response of Grassland Soil Quality to Shallow Plowing and Nutrient Addition.

Due to differences in the soil environment and grassland management measures, the change characteristics of soil microbial entropy and soil comprehensive quality in different types of grassland may vary significantly. In this study, the spatial variation characteristics of grassland soil microbial entropy under shallow plowing and nutrient addition measures were studied using a networking experimental platform established in a temperate meadow steppe, typical steppe, and desert steppe in northern China. The grassland soil quality was comprehensively evaluated to provide a theoretical basis for the scientific and reasonable management of grasslands under global climate change. The results show that in the meadow steppe, shallow plowing and nutrient addition significantly decreased the soil microbial biomass carbon and microbial entropy in the region, resulting in a decrease in the comprehensive score of soil quality. In the typical steppe, due to the influence of shallow tillage measures, the microbial biomass of the grassland soil in the region was higher than that of the control group and its two treatments, and the comprehensive score of soil quality was ranked first among the four treatments. In the desert steppe, the interaction of shallow plowing and nutrient addition significantly increased the soil microbial entropy in the region. Under the nutrient addition measures, the soil microbial entropy of the desert steppe showed a downward trend. In addition, the soil C/N ratio of the desert grassland under nutrient addition measures increased significantly, and the comprehensive score of soil quality ranked first among the four treatments as the microbial entropy decreased significantly.

Information encryption, highly sensitive detection of nitrobenzene, tetracycline based on a stable luminescent Cd-MOF.

A stable luminescent Cd-MOF, formulated as [Cd(L)0.5(4, 4'-bpy)0.5]·H2O (1), (H4L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 4, 4' -bpy = 4, 4'-bipyridine), is acquired under solvothermal conditions. 1 exhibits stability in the pH range from 1.5 to 12.2 and in different organic solvents. 1 can detect tetracycline and nitrobenzene by fluorescence quenching with high sensitivity and selectivity. The detection limits are 0.14 µM and 14 nM, respectively. Interestingly, 1 can encapsulate Tb3+ and sensitize its characteristic peaks. Moreover, the fluorescent ink is prepared by using the luminescent properties of the Tb3+@Cd-MOF. The light of the fluorescent ink disappears in an acid gas HCl atmosphere and then reappears in an alkaline gas ammonia atmosphere. This phenomenon can be repeated and the reason for this phenomenon is also explained in the article. Therefore, Tb3+@Cd-MOF has huge application potential in information encryption.

Highly selective detecting Aspartic acid, detecting Ornidazole and information encryption and decryption supported by a heterometallic anionic Cd (II)-K (I)-MOF.

A highly stable heterometallic MOF, {[(Me2NH2)2]·[Cd2K2(L)2(H2O)]}n (H4L = terphenyl-2, 2', 4, 4'-tetracarboxylic acid) (1), was synthesized. 1 featuring one-dimensional channels can efficiently detect Aspartic acid with a low limit of detection (LOD) value (2.5 µM). More interestingly, 1 can encapsulate Eu3+ and sensitize the visible-emitting characteristic fluorescence of Eu3+ in aqueous solution. Then, Eu3+@CdK-MOF is found to be an excellent fluorescence sensor for the detection of Ornidazole (ODZ) and the portable ODZ test paper is also successfully designed. Eu3+@CdK-MOF can also be used as fluorescent ink to write some words. The words can be hidden when treated with acid vapor and then the words can be restored when treated with alkaline vapor. More importantly, the hidden information can be read repeatedly. Therefore, this reversible light-emitting and reusable property have great potential for development in information encryption and decryption and information storage.

Electrochemical behaviour of uranium at a tripolyphosphate modified ITO electrode.

UO22+ binds to the surface of a tripolyphosphate modified mesoporous indium tin-doped oxide electrode (nanoITO|P3). Electrochemical studies reveal that nITO|P3 electrodes catalyze the 2-electron interconversion between UO22+ and U4+ with the P3-ligand assisting in the rate-limiting proton-coupled reduction of U(V) to U(IV), based on the kinetic isotope effect (1.8). Product composition between nITO|P3(U4+) and surface adsorbed UO2 can be controlled by adjusting the proton concentration and/or scan rate in voltammograms. These studies with uranium suggest that nITO|P3 electrodes are good candidates for redox transformations with other actinides including neptunium, plutonium, and americium.

Characterization and Comparative Analysis of Complete Chloroplast Genomes of Three Species From the Genus Astragalus (Leguminosae).

Astragalus is the largest genus in Leguminosae. Several molecular studies have investigated the potential adulterants of the species within this genus; nonetheless, the evolutionary relationships among these species remain unclear. Herein, we sequenced and annotated the complete chloroplast genomes of three Astragalus species-Astragalus adsurgens, Astragalus mongholicus var. dahuricus, and Astragalus melilotoides using next-generation sequencing technology and plastid genome annotator (PGA) tool. All species belonged to the inverted repeat lacking clade (IRLC) and had similar sequences concerning gene contents and characteristics. Abundant simple sequence repeat (SSR) loci were detected, with single-nucleotide repeats accounting for the highest proportion of SSRs, most of which were A/T homopolymers. Using Astragalus membranaceus var. membranaceus as reference, the divergence was evident in most non-coding regions of the complete chloroplast genomes of these species. Seven genes (atpB, psbD, rpoB, rpoC1, trnV, rrn16, and rrn23) showed high nucleotide variability (Pi), and could be used as DNA barcodes for Astragalus sp. cemA and rpl33 were found undergoing positive selection by the section patterns in the coded protein. Phylogenetic analysis showed that Astragalus is a monophyletic group closely related to the genus Oxytropis within the tribe Galegeae. The newly sequenced chloroplast genomes provide insight into the unresolved evolutionary relationships within Astragalus spp. and are expected to contribute to species identification.

Overgrazing-induced legacy effects may permit Leymus chinensis to cope with herbivory.

There is growing evidence that herbivory-induced legacy effects permit plants to cope with herbivory. However, herbivory-induced defense strategies in plants against grazing mammals have received little attention. To further understand the grazing-induced legacy effects on plants, we conducted a greenhouse experiment with Leymus chinensis experiencing different grazing histories. We focused on grazing-induced legacy effects on above-ground spatial avoidance and below-ground biomass allocation. Our results showed that L. chinensis collected from the continuous overgrazing plot (OG) exhibited higher performance under simulated grazing in terms of growth, cloning and colonizing ability than those collected from the 35-year no-grazing plot (NG). The enhanced adaptability of OG was attributed to increased above-ground spatial avoidance, which was mediated by larger leaf angle and shorter height (reduced vertical height and increased leaf angle contributed to the above-ground spatial avoidance at a lower herbivory stubble height, while reduced tiller natural height contributed to above-ground spatial avoidance at a higher herbivory stubble height). Contrary to our prediction, OG pre-allocated less biomass to the rhizome, which does not benefit the herbivory tolerance and avoidance of L. chinensis; however, this also may reflect a tolerance strategy where reduced allocation to rhizomes is associated with increased production of ramets.

Will the climate of plant origins influence the chemical profiles of cuticular waxes on leaves of Leymus chinensis in a common garden experiment?

Cuticular wax covering the leaf surface plays important roles in protecting plants from biotic and abiotic stresses. Understanding the way in which plant leaf cuticles reflect their growing environment could give an insight into plant resilience to future climate change. Here, we analyzed the variations of cuticular waxes among 59 populations of Leymus chinensis in a common garden experiment, aiming to verify how environmental conditions influence the chemical profiles of cuticular waxes. In total, eight cuticular wax classes were identified, including fatty acids, aldehydes, primary alcohols, alkanes, secondary alcohols, ketones, ß-diketones, and alkylresorcinols, with ß-diketones the predominant compounds in all populations (averaged 67.36% across all populations). Great intraspecific trait variations (ITV) were observed for total wax coverage, wax compositions, and the relative abundance of homologues within each wax class. Cluster analysis based on wax characteristics could separate 59 populations into different clades. However, the populations could not be separated according to their original longitudes, latitudes, annual temperature, or annual precipitation. Redundancy analysis showed that latitude, arid index, and the precipitation from June to August were the most important parameters contributing to the variations of the amount of total wax coverage and wax composition and the relative abundance of wax classes. Pearson's correlation analysis further indicated that the relative abundance of wax classes, homologues in each wax class, and even isomers of certain compound differed in their responses to environmental factors. These results suggested that wax deposition patterns of L. chinensis populations formed during adaptations to their long-term growing environments could inherit in their progenies and exhibit such inheritance even these progenies were exported to new environments.

Differences in the photosynthetic and physiological responses of Leymus chinensis to different levels of grazing intensity.

BACKGROUND: Grazing is an important land use in northern China. In general, different grazing intensities had a different impact on the morphological and physiological traits of plants, and especially their photosynthetic capacity. We investigated the responses of Leymus chinensis to light, medium, and heavy grazing intensities in comparison with a grazing exclusion control. RESULTS: With light grazing, L. chinensis showed decreased photosynthetic capacity. The low chlorophyll and carotenoid contents constrained light energy transformation and dissipation, and Rubisco activity was also low, restricting the carboxylation efficiency. In addition, the damaged photosynthetic apparatus accumulated reactive oxygen species (ROS). With medium grazing, more energy was used for thermal dissipation, with high carotene content and high non-photochemical quenching, whereas photosynthetic electron transport was lowest. Significantly decreased photosynthesis decreased leaf C contents. Plants decreased the risk caused by ROS through increased energy dissipation. With high grazing intensity, plants changed their strategy to improve survival through photosynthetic compensation. More energy was allocated to photosynthetic electron transport. Though heavy grazing damaged the chloroplast ultrastructure, adjustment of internal mechanisms increased compensatory photosynthesis, and an increased tiller number facilitated regrowth after grazing. CONCLUSIONS: Overall, the plants adopted different strategies by adjusting their metabolism and growth in response to their changing environment.

Stoichiometric ratios support plant adaption to grazing moderated by soil nutrients and root enzymes.

BACKGROUND: Vegetation succession is one of the major driving processes of grassland degradation. Stoichiometry significantly contributes to vegetation dynamics. However, a knowledge gap exists in how soil nutrients and root enzymes influence the stoichiometric ratio to affect vegetation dynamics. METHODS: To address these questions, we selected a dominant species (Leymus chinensis (Trin.) Tzvel.) and a degraded-dominant species (Artemisia frigida Willd.) under different management regimes (enclosure and grazing) on the Inner Mongolia steppe. We measured (i) plant nutrient concentrations, (ii) root enzymes and (iii) soil nutrients to investigate how the selected plant species responded to grazing. RESULTS: The results show that: (i) N and P concentrations and the C:N:P ratio in different organs are significantly affected by grazing, and there is variation in the plant species' response. Grazing significantly increased N and P in the leaves and stems of L. chinensis and the stems and roots of A. frigida. (ii) Grazing significantly increased the activities of glutamine synthase but decreased the activities of acid phosphatase in L. chinensis. The nitrate reductase and acid phosphatase activities significantly increased in A. frigida under grazing conditions. (iii) Grazing decreased the total nitrogen, total phosphorus, and available nitrogen, but increased the available phosphorus in the soil. CONCLUSION: We conclude that A. frigida is better adapted to grazing than L. chinensis, possibly because of its relatively increased stem and root growth, which enhance population expansion following grazing. Conversely, L. chinensis showed increased leaf and stem growth, but suffered nutrient and biomass loss as a result of excessive foraging by livestock, which severely affected its ability to colonize. Root enzymes coupled with soil nutrients can regulate plant nutrients and stoichiometric ratios as an adaptive response to grazing. Thus, we demonstrated that stoichiometric ratios allow species to better withstand grazing disturbances. This study provides a new understanding of the mechanisms involved in grazing-resistance within a plant-soil system.

A novel multi-purpose Zn-MOF fluorescent sensor for 2,4-dinitrophenylhydrazine, picric acid, La3+ and Ca2+: Synthesis, structure, selectivity, sensitivity and recyclability.

A new three-dimensional luminescence Zn-MOF sensor with the molecular formula [Zn4(µ3-OH)2(ptptc)1.5(DMA)(H2O)2]·2DMA (complex 1) for the selective sensing of 2,4-dinitrophenylhydrazine (2,4-DNPH), picric acid (PA), La3+ and Ca2+ has been synthesized from terphenyl-3,3',5,5'-tetracarboxylic acid (H4ptptc) and zinc nitrate under solvothermal conditions. XRD analysis reveals that complex 1 crystallizes in monoclinic system P21/n space group and consists of a three-dimensional network with one-dimensional channels, which are expected to facilitate the diffusion, concentration and detection processes. Real-time fluorescence quenching responses and good reversibility were observed in the fluorescence titration experiments with nano-molar scale detection limits for 2,4-dinitrophenylhydrazine (2,4-DNPH, 100 nM) and picric acid (PA, 500 nM). Noticeable emission band shift from 365 nm to 420 nm was observed when treated complex 1 with La3+ and a new emission band centered at 475 nm appeared when treated complex 1 with Ca2+ in the metal ions sensing experiments. In virtue of its high selectively, good sensitively and recyclability complex 1 could be a promising fluorescent sensor for explosives and metal ions.

Growth-defense trade-off regulated by hormones in grass plants growing under different grazing intensities.

Herbivory creates conflicts between a plant's need to allocate resources for growth and defense. It is not yet clear how plants rebalance resource utilization between growth and defense in response to increasing grazing intensity. We measured characteristics of the primary and secondary metabolism of Leymus chinensis at five levels of grazing intensity (control, light, moderate, heavy and extremely heavy). Furthermore, we evaluated hormone signaling by quantifying the impact of key hormones on plant growth and defense. Under light grazing intensity, indole-3-acetic acid and jasmonates appeared to promote the growth of L. chinensis through a high photosynthetic rate, high water-use efficiency and high soluble protein contents, whereas abscisic acid decreased these properties. Under moderate grazing intensity, L. chinensis had a low photosynthetic capacity but greater production of secondary metabolites (tannins, total flavonoids and total phenols), possibly induced by salicylic acid. When the grazing pressure further intensified, L. chinensis translocated more carbohydrates to its roots in order to survive and regrow. Leymus chinensis therefore exhibited a trade-off between growth and defense in order to survive and reproduce under herbivory. Plants developed different mechanisms to enhance their grazing tolerance by means of hormonal regulation.