Sensitivity Distribution Research Articles

Ecological risk assessment for BDE-47 in marine environment based on species sensitivity distribution method.

BDE-47 is the most abundant and toxic congener in the marine environment. Assessing the ecological risk of BDE-47 in seawater is of great importance to protect the marine species. However, the ecological risks of BDE-47 on marine species is still limited. In the present study, the hazardous concentrations for 5 % of species (HC5) values of BDE-47 were derived by species sensitivity distributions (SSD), the short-term water quality criteria (SWQC) and long-term water quality criteria (LWQC) were acquired from HC5. Moreover, the marine ecological risk of BDE-47 was assessed by the risk quotient (RQ) method in the coastal area of China. The SWQC and LWQC were 1.06μg/L and 0.61μg/L, respectively. According to published literature, the concentrations of BDE-47 ranged from undetected to 9.06ng/L, BDE-47 has no risk to marine species in most coastal areas, but might show low risk for a long exposure time in the coastal mariculture area of China. This study provides a new approach for the derivation of the WQC and the ecological risk assessment of BDE-47, which is essential for the protection of marine species and provides guidance to manage the concentration of BDE-47 for administrative department.

Risk of imidacloprid to soil invertebrates when applied as basal bark spray for the control of Hemlock Woolly Adelgid

The hemlock woolly adelgid (HWA Adelges tsugae) is an invasive insect on the east coast of North America where it has resulted in the widespread death and decline of hemlock trees. In Canada the most commonly used control strategy is the application of imidacloprid-based insecticides by basal bark spray, which could pose risk to non-target species. We monitored soil concentrations 50-400 cm away from trees for 24 months post application of Xytect 2f at a rate of 0.278 g imidacloprid/cm DBH and conducted a preliminary risk characterization by calculating Risk Quotients (RQ) for soil invertebrates derived from species sensitivity distributions build from No Observed Effect Concentrations (NOEC) and EC50 values. Imidacloprid was detected in 58.3–96.8% of samples at 50 and 100 cm and 8.3–45.8% at 200 and 400 cm from treated trees. The RQ values exceeded 1 at all times 50 cm from the tree for the median exposure, and at all distances and times for the upper 95% CI exposure. The frequency that RQ’s exceeded 1 declined with distance from tree at all time periods and declined over time at 50 and 100 cm from treated trees, but not at 200 and 400 cm. Overall, the highest risk to non-target soil invertebrates from basal bark application of imidacloprid occurs within 200 cm of treated trees.

Assessing chronic effects of chemical pollution on biodiversity using mean species abundance relationships.

Since chemical pollution poses a persistent threat to freshwater ecosystems and biodiversity, innovative methodologies are required to address the ecological risks associated with such pollutants. This study predicts the long-term impacts of chemicals based on an equation that describes the time-dependency of the median lethal and effect concentration (L(E)C50) with the Critical Body Residue concept. This way, the methodology can predict Species Sensitivity Distributions (SSDs) for any given time point. The methodology was extended to predict the Mean Species Abundance Relationships (MSAR) as an indicator of biodiversity. To test and validate the methodology, data from a case study with six freshwater arthropods exposed short- and long-term to imidacloprid was used. The potentially affected fraction of species (PAF) and its opposite (1-PAF) was used to validate the MSAR framework itself. The accuracy of the predicted chronic median lethal concentration (LC50) values was species-dependent. However, except for one species, all predicted chronic LC50 values were within the 95% Confidence Intervals (CIs) of the fits based on only acute data. The mean differences between the predicted and calculated MSARs were between 2% and 6%. The predicted MSARs generally underestimated the impact of imidacloprid. However, all predicted MSARs were either similar or lower than the calculated 1-PAF, and their CIs covered the calculated MSARs. Thus, the study found that the presented methodology is useful for predicting the long-term effects of chemical pollutants.

Copper prevention values in Brazilian subtropical soils.

The Brazilian National Environmental Council (CONAMA) Resolution 420/2009 establishes soil quality guideline values for copper, as the prevention value (PV). It defines the maximum concentrations of chemical substances permitted in the soil. Thus, the aim of the present research was to evaluate the effectiveness of the copper PV adopted at the national level by conducting exposure assays with enchytraeids (Enchytraeus crypticus, Enchytraeus bigeminus and Enchytraeus dudichi) and springtails (Folsomia candida, Proisotoma minuta and Sinella curviseta) in two Brazilian subtropical soils: a Latosol and an Argisol. Results revealed that copper reduces the reproductive capacity of all organisms as its concentration increases in the evaluated soils. Argisol presented the lowest effective concentration of 20% (EC20) and 50% (EC50) in species reproduction for all organisms evaluated. The most sensitive organism was the enchytraeid E. bigeminus, with EC20 values of 58mgkg⁻1 in Latosol and 30mgkg⁻1 in Argisol, and EC50 values of 155mgkg⁻1 in Latosol and 91mgkg⁻1 in Argisol. Among the springtails, S. curviseta exhibited the highest EC20, with values of 230mgkg⁻1 in Latosol and 136mgkg⁻1 in Argisol. Conversely, the highest values of EC50 were recorded for the species P. minuta (526mgkg⁻1 in Latosol and 415mgkg⁻1 in Argisol). Based on the species sensitivity distribution (SSD) approach, the PVs calculated were 172mgkg⁻1 for Latosol and 106mgkg⁻1 for Argisol, derived from EC50 data. For EC20 data, the PV values calculated were 158mgkg⁻1 in Latosol and 100mgkg⁻1 in Argisol. By comparing the PV with the Brazilian adopted PV for copper (60mgkg-1), it was observed the efficacy of the CONAMA Resolution.

Development of a bioavailability-based acute effects assessment method for nickel.

This study aimed to develop a bioavailability-based effects assessment method for nickel (Ni) to derive acute freshwater environmental thresholds in Europe. The authors established a reliable acute freshwater Ni ecotoxicity database covering 63 different freshwater species, and the existing acute Ni bioavailability models for invertebrates were revised. A single average invertebrate bioavailability model was proposed, in which the protective effects of Ca2+ and Mg2+ on Ni2+ toxicity were integrated as a single-site competition effect at the Ni biotic ligand. The biotic ligand stability constants for Ca2+ and Mg2+ (log KCaBL = 3.80 and log KMgBL = 3.32) were derived by averaging these parameters from three existing cladoceran models. A pH extension was also integrated into the average invertebrate bioavailability model to reflect the increase in free Ni2+ toxicity observed greater than pH 8.0. The proposed invertebrate model has further been validated using an extensive dataset of acute toxicity data covering 15 different invertebrate species. Evaluating the extrapolation of the invertebrate model to plant species revealed significant uncertainty about the applicability of the acute Ni bioavailability models for plants. The newly developed acute invertebrate model was used alongside the existing acute fish and algae bioavailability models to support an acute bioavailability normalization approach for Ni. By combining these bioavailability models with the acute toxicity dataset for Ni, a normalized species sensitivity distribution approach is proposed to derive site-specific acute environmental thresholds, expressed by the HC5L(E)C50 (i.e., dissolved Ni concentration resulting in at least 50% effect for 5% of the species). The applicability ranges of the acute Ni bioavailability normalization approach are estimated to be valid for approximately 70% of European freshwaters. The proposed approach serves as a basis to incorporate bioavailability into the compliance evaluation relative to acute environmental threshold values for Ni in Europe.

Species sensitivity distribution of rare earth elements: A full overview.

Rare earth elements (REEs) encompass 15 lanthanides and play a crucial role in modern technology. Despite their essential uses, REEs are emerging environmental contaminants due to their growing presence in industrial, agricultural, and medical applications. For the first time, the species sensitivity distribution (SSD) approach was applied to REEs considering 58 papers including toxicity about Ce, Dy, Er, Gd, La, Lu, Nd, Pr, Sm, and Y. SSD curves were constructed by log-logistic model providing comprehensive comparisons of the sensitivities of different species to the relative REEs deriving the hazardous concentrations (HC) at 5% and 50%. The review reveals that arthropods, especially Daphnia magna, and echinoderms such as Sphaerechinus granularis exhibit high sensitivity especially to Ce, Er, and Lu. Conversely, vertebrates, particularly Oncorhynchus mykiss, showed greater tolerance to REEs exposure. The general hazard perception evidenced the following prioritization list according to HC5 values in increasing order: Dy (0.03μg/l)>Ce (0.15μg/l)>Sm (0.29μg/l)>La (0.64μg/l)>Y (0.81μg/l)>Gd (0.95μg/l)>Pr (1.44μg/l)>Er (1.45μg/l)>Nd (1.67μg/l)>Lu (2.19μg/l). This review highlighted gaps in REEs ecotoxicity, particularly regarding heavy REEs (HREEs), and stressed the need for more data on their long-term one-health impacts. Such knowledge is vital for developing strategies to mitigate REEs contamination, emphasizing the importance of establishing safe exposure thresholds to protect both ecosystems and human health.

Accounting for microorganisms yields stricter water quality criteria and elevated ecological risks of antibiotics: A case study of sulfonamides in the Yangtze River Delta.

The derivation of water quality criteria (WQC) for antibiotics is influenced by the inclusion of various organisms' toxicity data, including microbial data, though no definitive conclusions have been reached. This study focuses on sulfonamide antibiotics, common in the Yangtze River Delta (YRD), to assess the influences of different organisms' toxicity data on determining WQCs and subsequent evaluation of ecological risks. A total of 263 toxicity data points from eight sulfonamides, including sulfamethoxazole (SMX) and sulfamethazine (SM2), were selected to derive WQCs using Species Sensitivity Distribution (SSD) methods. Three WQC types were calculated: based on native species (WQC-n), a combination of native and non-native species (WQC-nn), and a combination of species and microorganisms (WQC-nnm). While WQC-nn showed minimal differences from WQC-n, the inclusion of microbial data resulted in more conservative short-term WQCs (SWQC-nnm), calculated as 256.90 μg/L for SMX and 196.09 μg/L for SM2, approximately half of SWQC-nn values (435.20 μg/L for SMX and 491.11 μg/L for SM2). Monitoring data from the past 15 years in the YRD revealed a 133 % increase in ecological risks when using LWQC-nnm compared to LWQC-n and LWQC-nn, particularly under the worst-case pollution scenarios. However, there was a slight temporal decline in overall ecological risks. The study concludes that incorporating microbial toxicity data results in more protective WQCs and underscores the need for further research to develop WQCs that safeguard sensitive organisms and better reflect real-world exposure scenarios, e.g., the mixture exposure.

Spatial Distribution and Chronic Ecological risk Assessment of Typical Phthalate Esters in the Surface Waters of China.

The chronic ecological risks posed by residual PAEs in China remain unclear. In this study, we analyzed the spatial distribution of five typical PAEs in the surface waters of China, dibutyl phthalate (DBP), diethylhexyl phthalate (DEHP), butylbenzyl phthalate (BBP), diethyl phthalate (DEP), and dimethyl phthalate (DMP). The highest concentration of PAEs were detected in the Liao River, ranging from 5 to 79.8µg/L. DBP was of the PAEs type with the highest concentration in the surface waters in China. By fitting the species sensitivity distribution curves base on the collected data over the past decade, the chronically hazardous concentrations affecting 5% of the aquatic species were calculated to be 0.018, 0.022, 0.062, 0.851, and 9.437mg/L for DBP, DEHP, BBP, DEP, and DMP, respectively. Thus, DBP, DEHP, and BBP pose the greatest threat to aquatic organisms, and PAEs pose high ecological risks in the Liao, Huangpu, and Pearl Rivers.

Investigating the Mass Sensitivity of Quartz Crystal Microbalances with Circularly Symmetric Electrodes in the Third Overtone Mode.

This study investigates the mass sensitivity of a quartz crystal microbalance (QCM) with a circular symmetric electrode (M-M type) operating in the third overtone mode and finds that its central mass sensitivity is nearly five times greater than that of the fundamental mode, as determined through a deposition experiment, rather than the three times greater central mass sensitivity predicted by classical theory. The reasons for this phenomenon were determined through a combination of theoretical calculation and finite element simulation. The results revealed that (1) compared with the fundamental mode, the third overtone mode exhibits a more pronounced energy trapping effect, leading to a sharper mass sensitivity distribution and a more concentrated sensitivity in the central region and (2) the third overtone resonance frequency is slightly higher than three times the fundamental resonance frequency. This study indicates that operating the QCM in the third overtone mode significantly enhances its mass sensitivity, making it particularly suitable for applications requiring precise detection.

Spatial distribution prediction of landslide susceptibility based on integrated particle swarm optimization

Landslide sensitivity prediction relies on multiple environmental factors, making it difficult to obtain accurate prediction results. In order to improve the prediction accuracy of regional landslide sensitivity, a landslide sensitivity spatial distribution prediction method based on integrated particle swarm optimization was studied in Lianhe Village, Jianfeng Town, Shizhong District, Leshan City, Sichuan Province. Based on the determination coefficient, the sensitivity of landslide influencing factors was analyzed, and the weights of the influencing factors were determined. A landslide sensitivity spatial distribution prediction model was established based on support vector machine. By introducing simulated annealing and mutation operations into the particle swarm algorithm, an integrated particle swarm algorithm was obtained to extract high weight features of landslide sensitivity space and generate landslide sensitivity prediction results. The experimental results show that the cumulative value (ACU) of this method for predicting landslide sensitivity is 0.91, which can accurately predict the spatial distribution of landslide sensitivity in the study area and has practical value.

Hardness-Dependent Freshwater Quality Criteria for the Protection of Aquatic Organisms for Cadmium in China

Cadmium poses a significant threat to freshwater aquatic organisms and ecosystems, making it essential to establish regional freshwater quality criteria (FWQC) in China to safeguard these organisms. The toxicity database for cadmium covered 249 acute toxicity data from 52 species (seven phyla and 27 families) and 62 chronic toxicity data from 21 species (four phyla and 12 families). During short-term exposure, Morone saxatilis displayed the most sensitivity to cadmium, whereas Daphnia magna showed the most sensitivity in long-term exposure scenarios. Significant correlations were identified between water hardness and the toxicity data for cadmium, with the acute toxicity coefficient (KATD) at 1.0227 (n = 52, p < 0.05) and the chronic toxicity coefficient (KCTD) at 0.4983 (n = 21, p < 0.05). With the species sensitivity distribution method, the short-term freshwater quality criteria (S-FWQC) were derived with a normal distribution as the best fit (R2 0.9793), while the long-term freshwater quality criteria (L-FWQC) were calculated using a logistic distribution as the best fit (R2 0.9686). The formulas for the S-FWQC and L-FWQC were represented as 10(1.0227×lg(H)−1.5444) and 10(0.4983×lg(H)−1.7549), respectively, with water hardness serving as an independent variable. This study offers valuable insights for improving the management of cadmium to protect freshwater aquatic organisms in China.

Radiation source detection for the accurate location of lymph node metastases using robotic forceps-type coincidence radiation detector.

We have developed a forceps-type coincidence radiation detector for supporting lymph node dissection in esophageal cancer treatment. For precise detecting, this study aims to measure the 2D point-spread function of the detector at three difference tip angles, to devise a method to determine the position of a point source using the 2D point-spread function. The 2D sensitivity distribution on the surface of the detector was investigated to assess sensitivity variation caused by differences in the relative positions of the detector and radiation source. Based on the results, we identified the peak sensitivity value and proposed a detection method using this value. We evaluated the effectiveness of the proposed method by detecting radiation source location using this simulated distribution. From the radiation sensitivity distribution measurements, we observed a gradual decrease in radiation detection sensitivity from the center toward the edges of the detector surface. Additionally, we verified that the peak sensitivity value was attainable. Through the basic verification of the detection method, we confirmed that the radiation source location could be detected within a maximum error of 1.4mm. We developed a peak value search method aimed at mitigating sensitivity variations by leveraging the sensitivity distribution across the detector surface. The proposed device is thought to be able to quantitatively evaluate the desired target assuming that the field of view could be limited to the area clamped by the detector. As a next research step, more precise search methods should be verified in an environment resembling the one of the target clinical uses.

Response function measurement for a non-destructive gas-sheet beam profile monitor.

A gas-sheet beam profile monitor enabling non-destructive two-dimensional profile measurements of a high-intensity beam by capturing an image of a beam-induced fluorescence was developed. For quantitative profile measurements, the monitor's response function comprising, e.g., the gas sheet density distribution and the detector's sensitivity distributions must be experimentally clarified because the monitor output is a converted profile with the response function. A response function measurement method was devised based on the beam-profile-measurement method formula of the monitor. The response function was obtained by injecting a thin electron beam into the developed monitor and scanning its center position in transverse. The measured response function was evaluated by the J-PARC 3MeV, 60 mA H- beam profile measurement. The 2-D beam profile was successfully reconstructed with the measured response function within the 2.74% residual of the least-squares method and 6.01% experimental statistic deviation. The projected 1-D profiles agreed well with those measured using a wire-scanning-type profile monitor.

Species-specific sensitivity to CuO nanoparticles: Establishing seawater quality criteria for Chinese marine ecosystems

The rapid proliferation of the emerging hazardous pollutant, copper oxide nanoparticles (CuO NPs), has raised significant ecological concerns in marine environments. The study comprehensively investigates the toxicity of CuO NPs on nine Chinese resident marine organisms across five phyla and eight families of marine organisms. Adhering to the “Technical guideline for deriving water quality criteria for marine organisms (on trial)”, we employ species susceptibility distribution (SSD) and species susceptibility ranking (SSR) methods to establish specific seawater quality criteria for CuO NPs. Utilizing acute and chronic toxicity data of each species, short- and long-term seawater quality criteria for CuO NPs in China were established via the National Ecological Environment Criteria Calculation Software-Species Sensitivity Distribution Method (EEC-SSD) software, as 187 μg/L for short-term exposure and 9.65 μg/L for long-term exposure. These WQC provide a foundation for nanometal risk assessment and regulatory frameworks concerning nanoparticle pollution in marine environments. The established water quality criteria for CuO NPs help to protect Chinese marine organisms from potential hazards and set a precedent for incorporating multidisciplinary perspectives into the growing threat of nano-pollution.

Form-Specific Prospective Environmental Risk Assessment of Graphene-Based Materials in European Freshwater.

As graphene-based materials (GBMs) such as pristine graphene, graphene oxide, and reduced graphene oxide show great potential to be integrated in various applications, the need for environmental risk assessments grows, aiming to navigate the environmental fate and potential risk of the different forms of GBM. This study used dynamic probabilistic material flow analysis (DPMFA) to ascertain the prospective production volumes and distribution of GBMs within European freshwaters. The hazard assessment leveraged 113 data sets from peer-reviewed studies, addressing aquatic ecotoxicity across 26 species, by performing probabilistic species sensitivity distributions (SSD). Our findings reveal distinct environmental distribution patterns for GBM forms with predicted environmental concentrations in European freshwaters by 2030 of approximately 0.67 ng/L (SD = 0.24 ng/L) for pristine graphene and 0.33 ng/L (SD = 0.10 ng/L) for both graphene oxide and reduced graphene oxide, suggesting not only similar but notably minimal exposure levels. The risk characterization ratios (RCRs) for all forms of GBM were significantly below 1, indicating a negligible environmental risk within the scenarios assessed. Through detailed analysis considering the forms of the material, this research can inform regulatory decisions, support sustainable material design, and provide a solid foundation for a further investigation considering the environmental fate of GBM.

Network-based investigation of petroleum hydrocarbons-induced ecotoxicological effects and their risk assessment

Petroleum hydrocarbons (PHs) are compounds composed mostly of carbon and hydrogen, originating from crude oil and its derivatives. PHs are primarily released into the environment through the diffusion of oils, resulting from anthropogenic activities like transportation and offshore drilling, and accidental incidents such as oil spills. Once released, these PHs can persist in different ecosystems and cause long-term detrimental ecological impacts. While the hazards associated with such PH contaminations are often assessed by the concentrations of total petroleum hydrocarbons in the environment, studies focusing on the risks associated with individual PHs are limited. In this study, different network-based frameworks were utilized to explore and understand the adverse ecological effects associated with PH exposure. First, a list of 320 PHs was systematically curated from published reports. Next, biological endpoint data from toxicological databases was systematically integrated, and a stressor-centric adverse outcome pathway (AOP) network, linking 75 PHs with 177 ecotoxicologically-relevant high confidence AOPs within AOP-Wiki, was constructed. Further, stressor-species networks, based on reported toxicity concentrations and bioconcentration factors data within ECOTOX, were constructed for 80 PHs and 28 PHs, respectively. It was found that crustaceans are documented to be affected by many of these PHs. Finally, the aquatic toxicity data within ECOTOX was used to construct species sensitivity distributions for PHs, and their corresponding hazard concentrations (HC05), that are harmful to 5% of species in the aquatic ecosystem, were derived. Further, the predicted no-effect concentrations (PNECs) and risk quotients for the US EPA priority polycyclic aromatic hydrocarbons (PAHs) were computed by using their environmental concentration data for Indian coastal and river waters. Overall, this study highlights the importance of using network-based approaches and risk assessment methods to understand the PH-induced toxicities effectively.

Desertification sensitivity and its impacts on land use change in the Tarim Basin, Northwest China

Desertification poses a major challenge in the northwestern arid areas of China. Land use activities are increasingly endangered by desertification, including direct impact (e.g., farmland abandonment) and indirect impact (e.g., farmland area control). However, previous studies have primarily focused on the impact of land use on desertification processes, while there has been limited research on the direct and indirect impacts of desertification on land use. Based on the Mediterranean Desertification and Land Use (MEDALUS) and Future Land Use Simulation (FLUS) models, we identify the spatiotemporal distribution of desertification sensitivity and analyze the direct and indirect impacts of desertification on land use in the Tarim Basin from 2000 to 2020. The results showed that the desertification sensitivity areas were primarily concentrated in the critical areas (proportion > 50 %), followed by the fragile and potential areas. In terms of the direct impact, the areas of abandoned farmland due to desertification were 68.25 km2 and 1444.25 km2 during the periods of 2000–2010 and 2010–2020, respectively. Additionally, 3893.25 km2 of farmland was at risk of abandonment. After being abandoned, the farmland was primarily converted into grassland. In terms of the indirect impact, the differences between predicted (simulations without farmland area control) and observed farmland area, serving as an indicator of farmland area control to reduce desertification risks, were 1065.75 km2 in 2010 and 4614.00 km2 in 2020. Our paper provides new insights into the direct and indirect impacts of desertification on land use, providing references for formulating desertification control policies and regional land use planning.

A systematic workflow of data mining confirms widespread ecological risks of SDHIs fungicides contamination in aquatic environment

Succinate dehydrogenase inhibitors (SDHIs) are widely utilized fungicides that have been detected in various environments, raising significant concerns regarding their toxicity to aquatic organisms. A comprehensive analysis of SDHIs contamination and associated ecological risks has been challenging due to scattered data and varying scale. This study consolidated residue data from 194 aquatic environments across six regions, up to June 2024, providing an overview of SDHIs distribution and conducting a global-scale aquatic ecological risk assessment. We analyzed 20 SDHIs, with boscalid, fluopyram, flutolanil, fluxapyroxad, mepronil, and thifluzamide being the most frequently detected across Asia, Europe, North America, South America, Africa, and Australia. The concentrations and types of SDHIs varied significantly among continents, with data sourced from water, sediment and aquatic organisms. Utilizing a web-based Interspecies Correlation Estimation-Species Sensitivity Distribution (ICE-SSD) model, we identified substantial sensitivity differences among species, with benzovindiflupyr showing the lowest LC50 of 3.5 μg/L, indicating a high risk when concentrations exceed 0.035 μg/L (Maximum Acceptable Concentration, MAC). Risk quotient (RQ) values revealed that flutolanil posed high risks to eight aquatic ecosystems and medium risks to five, while boscalid presented medium risk to one ecosystem. Our findings also demonstrated a significant correlation between the aquatic ecotoxicity of SDHIs and their characteristics (log Kow, solubility, and pKa). Collectively, we advocate for the restricted use of SDHIs and emphasize the necessity for further evaluation of their environmental behavior and integrated risks within the “One Health” framework.

Advancing woody plant regeneration: Insights from salix species tissue culture studies

Abstract. In this study, we established a sterile propagation and regeneration system for Mongolian willow in order to study its salt tolerance and adaptation in depth and to provide methods for future genetic improvement. Mongolian willow, belonging to the genus Willow in the family Populus, is valued for its high salt tolerance and ability to ameliorate high pH soils. However, its distribution in specific saline soil areas and sensitivity to drought and rainless environments make its reproduction limited. In this study, by stem segment induction method, we aseptically cultured apical and lateral shoots of Mongolian willow, respectively, and found that the apical shoots performed best in MS medium supplemented with 0.1 mg/L IBA, while the lateral shoots grew well in MS medium supplemented with 6-BA, IBA and TDZ. In addition, this study investigated the effects of different combinations of phytohormones on healing tissue induction and found that the combination of NAA and 6-BA had the highest success and value-added rate. Further addition of TDZ significantly increased the induction rate. The study also dealt with the application of DNA methylation inhibitors in inducing adventitious shoots, and the results showed that the addition of this inhibitor in specific culture medium could significantly increase the induction rate of adventitious shoots. In this study, the regeneration system of Mongolian willow was successfully established, which provides a basis for its future genetic research and wide application.

Fluorination Affects the Force Sensitivity and Nonequilibrium Dynamics of the Mechanochemical Unzipping of Ladderanes.

When multiple reaction steps occur before thermal equilibration, kinetic energy from one reaction step can influence overall product distributions in ways that are not well predicted by transition state theory. An understanding of how the structural features of mechanophores, such as substitutions, affect reactivity, product distribution, and the extent of dynamic effects in the mechanochemical manifolds is necessary for designing chemical reactions and responsive materials. We synthesized two tetrafluorinated [4]-ladderanes with fluorination on different rungs and found that the fluorination pattern influenced the force sensitivity and stereochemical distribution of products in the mechanochemistry of these fluorinated ladderanes. The threshold forces for mechanochemical unzipping of ladderane were decreased by α-fluorination and increased by γ-fluorination; these changes correlated to the different stabilizing or destabilizing effects of fluorination patterns on the first transition state. Using ab initio steered molecular dynamics (AISMD), we compared the product distributions of synthesized and hypothetical ladderanes with different substitution patterns. These calculations suggest that fluorination on the first two bonds of ladderane gives rise to a larger fraction of dynamic trajectories and a larger fraction of E-alkene product through a mechanism resulting from larger momentum because of the greater atomic mass of fluorine. Fluorination on the third and fourth rungs instead gives a larger fraction of E-alkene product primarily due to electronic effects. These combined experimental and computational studies of the mechanochemical unzipping of fluorinated ladderanes provide an example of how relatively simple substituents can affect the extent of nonstatistical dynamics and, thus, mechanochemical outcomes.