Root Concentration Factor Research Articles

Machine Learning Models for Predicting Bioavailability of Traditional and Emerging Aromatic Contaminants in Plant Roots.

To predict the behavior of aromatic contaminants (ACs) in complex soil-plant systems, this study developed machine learning (ML) models to estimate the root concentration factor (RCF) of both traditional (e.g., polycyclic aromatic hydrocarbons, polychlorinated biphenyls) and emerging ACs (e.g., phthalate acid esters, aryl organophosphate esters). Four ML algorithms were employed, trained on a unified RCF dataset comprising 878 data points, covering 6 features of soil-plant cultivation systems and 98 molecular descriptors of 55 chemicals, including 29 emerging ACs. The gradient-boosted regression tree (GBRT) model demonstrated strong predictive performance, with a coefficient of determination (R2) of 0.75, a mean absolute error (MAE) of 0.11, and a root mean square error (RMSE) of 0.22, as validated by five-fold cross-validation. Multiple explanatory analyses highlighted the significance of soil organic matter (SOM), plant protein and lipid content, exposure time, and molecular descriptors related to electronegativity distribution pattern (GATS8e) and double-ring structure (fr_bicyclic). An increase in SOM was found to decrease the overall RCF, while other variables showed strong correlations within specific ranges. This GBRT model provides an important tool for assessing the environmental behaviors of ACs in soil-plant systems, thereby supporting further investigations into their ecological and human exposure risks.

Structure-Dependent uptake and metabolism of Tire additives Benzothiazoles in carrot plant

Tire additives, such as benzothiazole and its derivatives (collectively called BTs), are large-volume chemicals that are constantly emitted into agricultural environment via tire-road wearing and other actions. The potential accumulation of BTs in food crops depends largely on their metabolism in plants, which is poorly understood. Herein, we evaluated uptake and metabolism of six BTs in carrot callus and intact carrot plants to understand their structure-specific metabolism. All BTs were readily taken up by carrot roots, with their root concentration factors (RCF) ranging from 1.66 ± 0.01 to 2.95 ± 0.05. Although the tested BTs exhibited poor upward translocation from root to leaves (translocation factors < 1), the translocation factors of 2-methylbenzothiazole (0.79) and 2-aminobenzothiazole (0.65) were significantly higher than that of 2-methylbenzothiazole (0.18) and 2-(methylthio)benzothiazole (0.22). These results indicated the structure-dependent uptake and translocation of BTs in carrot. Correlation analysis between log Kow and log RCF or TF revealed that the hydrophobicity of BTs predominantly affected their root uptake and acropetal translocation in carrots. With the aid of high-resolution mass spectrometry, a total of 18 novel metabolites of BTs were tentatively identified, suggesting that BT compounds can be metabolized by carrot callus. The proposed metabolites of BTs include four hydroxylated products, one demethylated product, five glycosylated products and eight amino acid conjugated products, revealing that glycosylation and amino acid conjugation were the dominant transformation pathways for BT metabolism in carrot. However, the detected species of metabolites for six BTs varied distinctly, indicating structure-specific metabolism of BTs in plants. The findings of this study improve our understanding of structure-dependent fate and transformation of BTs in plants. Since BTs metabolites in food crops could present an unintended exposure route to consumers, the structure-specific differences of BTs uptake, metabolism and accumulation in plants must be considered when addressing human dietary exposure risks.

Insights into the uptake, accumulation, and metabolism of UV-328 in lettuce (Lactuca sativa L.) and radish (Raphanus sativus L.)

2-(2H-benzotriazole-2yl)-4,6-di-t-pentylphenol (UV-328), a newly listed persistent organic pollutant (POP) under the Stockholm Convention, has garnered significant attention. It is imperative to understand the uptake, translocation and metabolic pathways of UV-328 in plants to assess its bioaccumulation capacity and potential human health risks. In this study, the absorption, accumulation, and metabolic characteristics of UV-328 in lettuce (Lactuca sativa L.) and radish (Raphanus sativus L.) were assessed by hydroponic experiments. In the hydroponics experiment, UV-328 was significantly absorbed by the roots of the plants, with average root concentration factors (RCFs) ranging from 58.5 to 400 mL/g for lettuce and 84.4 to 154 mL/g for radish. However, UV-328 was poorly translocated from roots to shoots, with a translocation factor (TF) below 0.055. Furthermore, UV-328 underwent transformation and metabolism within the plant. Utilizing a nontarget screening strategy, fourteen phase I metabolites of UV-328 were firstly identified. The metabolic pathways of UV-328 in plants including hydroxylation, demethylation, oxidation, acetylation and deoxygenation were also suggested. It was worth noting that UV-328 has a significant adverse impact on plant growth and quality. The concentration of chlorophyll in plants exposed to UV-328 was significantly reduced, as were the concentrations of water, flavonoids, vitamin C and amino acids.

Deep learning models for predicting plant uptake of emerging contaminants by including the role of plant macromolecular compositions

Deep learning models can predict uptake of emerging contaminants in plants with improved accuracy because they leverage advanced data-driven approaches to capture non-linear relationships that traditional models struggle to address. Traditional models suffer from low accuracy in predicting transpiration stream concentration factor (TSCF) and root concentration factor (RCF). This study applied deep neural networks (DNN), recurrent neural networks (RNN), and long short-term memory (LSTM) to enhance the accuracy of predictive models for TSCF and RCF. The three models used nine chemical properties and two plant root macromolecular compositions for predicting TSCF and RCF. The results indicated that deep learning models predict TSCF and RCF with improved accuracy compared to mechanistic models. The coefficient of determination (R2) for the DNN, RNN, and LSTM models in predicting TSCF was 0.62, 0.67, and 0.56, respectively. The corresponding mean squared error (MSE) on the test set for the models was 0.055, 0.035, and 0.060, respectively. The R2 for the DNN, RNN, and LSTM models in predicting RCF was 0.90, 0.91, and 0.84, respectively. The corresponding MSE for the models was 0.124, 0.071, and 0.126, respectively. The results of feature extraction using extreme gradient boosting underlined the importance of lipophilicity and root lipid fraction.

Kinetics of uptake, translocation, and metabolism of organophosphate esters in japonica rice (Oryza sativa L.): Hydroponic experiment combined with model

Hydroponics combined with fugacity model was employed to investigate the kinetics of uptake, accumulation, and metabolism of organophosphate esters (OPEs) by japonica rice. The time-dependent process for uptake and accumulation of 5 OPEs and their diester-metabolites in both rice root and shoot fitted well with the pseudo-first-order kinetic model. The peak OPE accumulations in rice root and shoot were significantly positively or negatively correlated with their octanol-water partition coefficient (logKow) respectively, but not for their apparent accumulation rates. Root concentration factors (RCFs) and root-to-shoot translocation factors (TFs) of OPEs were found to be positively and negatively correlated with their logKow, respectively. Triphenyl phosphate with benzene ring substituents showed the highest RCF, but the lowest TF, because of its high potential for root adsorption due to the π electron-rich structures. Sterilized root exudates can hinder the root adsorption and absorption of OPEs from solution probably through competitive adsorption of OPEs with root surface. The first-hand transport and metabolism rates were also obtained by generating these rates to fit the dynamic fugacity model with the measurement values. The simulation indicated that the kinetics of OPE accumulation in rice plants may be controlled by multiple processes and physicochemical properties besides Kow.

Co-exposure to Organophosphate esters (OPEs) and Cadmium alleviated their accumulation in rice (Oryza sativa L.) by inhibiting transports' transcription

Combined contamination of Organophosphate esters (OPEs) and heavy metal has been concerning on their potential threaten to human health through food chain. In order to estimate effects of OPEs and heavy metal's combined contamination on crop, the growth of rice seedlings, pollutant accumulations and their involved in transcript regulation pathway under OPEs and Cd contamination were investigated. In results, only single OPEs pollution improved the biomass of rice, while single Cd pollution inhibited the growth of plants. Although the combined contaminations of OPEs and Cd also showed negative effect for plant growth, OPEs could alleviate the negative effect of Cd on rice. The Octanol-water partition coefficients (log Kow) of OPEs were positively correlated with root concentration factor (RCF) values in the trend line and negatively correlated with shoot concentration factor (SCRF) and translocation factor (TF). OPEs and Cd inferred with each other's accumulations in plants through reducing RCF, SCRF and TF. After addition of Cd, the expressions of OsTIL, OsLTP4, OsLTPL1, and OsMLP423 genes involved in OPEs accumulation were downregulated. Moreover, the presence of Cd also affected the binding sites and binding energy of the four proteins with OPEs. Meanwhile, the expression of OsNramp1, OsNramp5, OsHMA2, OsGS1, and OsPCS1 genes involved in Cd accumulation and toleration were also downregulated after addition of OPEs. These results suggested that OPEs and Cd directly repressed each other gene transcript involved in accumulation and toleration process.

Bioaccumulation of legacy and emerging per- and polyfluoroalkyl substances in hydroponic lettuce and risk assessment for human exposure

Reclaimed water for irrigation or hydroponic cultivation provides exposure pathways for per- and polyfluoroalkyl substances (PFAS) to enter the human food chain. This study employed hydroponic methods to investigate the behavior of legacy PFAS and emerging chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) in lettuce grown under environment-related exposure levels and assessed the human exposure risks from consuming contaminated lettuce. Overall, PFAS in lettuce were concentration-dependent, with long-chain PFAS tending to accumulate in roots and short-chain PFAS accumulating more in shoots. The enrichment of PFAS in lettuce was jointly influenced by their chain length and polar functional groups. Specifically, the root concentration factors (RCFs) of PFAS generally increased with increasing chain length, and RCF values of most perfluoroalkanesulfonic acids (PFSAs) were significantly higher than those of perfluoroalkyl carboxylic acids (PFCAs) with the same chain length (p < 0.01), while the translocation factors (TFs) exhibited opposite trends. RCF values of perfluorooctane sulfonate (PFOS) and its alternatives, Cl-PFESAs, were ranked as follows: 8:2 Cl-PFESA (mean: 139) > 6:2 Cl-PFESA (28.6) > PFOS (25.7), which was attributed to the increased molecular size and hydrophobicity resulting from the insertion of ether bonds and additional CF2 in 8:2 Cl-PFESA. Notably, TF value of 8:2 Cl-PFESA (mean: 0.007) was the smallest among all PFAS, indicating 8:2 Cl-PFESA was difficult to transfer to nutritional compartments. Adults and children would exceed the most conservative health-based reference dose (RfD) by consuming approximately 15.9–148 g and 7.92–74.0 g of contaminated lettuce per day, implying high health risks.

Active ingredient identification and purification of organosilicon spray adjuvant and its uptake and translocation in rice (Oryza sativa L.).

The assessment of residue, absorption, conduction, and degradation of agricultural organosilicon surfactants in the environment is hindered by the lack of information on active ingredients and corresponding quantitative standards for organosilicon spray adjuvants. The spray adjuvant 'Jiexiaoli,' a primary organosilicon spray agent in China, was identified as hydroxy (polyethylene) propyl-heptamethyl trisiloxane (TSS-H) with 3-15 ethoxy (EO) groups. Purification of TSS-H was achieved through semi-preparative separation using high-performance liquid chromatography (HPLC), resulting in TSS-H purity exceeding 96%. An accurate residual detection method for nine oligomers (4-12 EO) of TSS-H in rice roots, stems, leaves, and culture solution samples was developed using HPLC tandem high-resolution mass spectrometry (HPLC-HRMS). Recoveries for nine oligomers of TSS-H in the four matrices ranged from 80.22% to 104.01%. Foliar application experiments demonstrated that TSS-H did not transfer from the upper to the lower parts of the rice plant. The half-lives of each oligomer (4-12 EO) in leaves were less than 3.21 days. Root application experiments revealed a root concentration factor (RCF) ranging from 0.20 to 0.56, a biological enrichment factor (BCF) ranging from 0.36 to 0.68, a transpiration factor (TSCF) ranging from 0.069 to 0.086, and a transport factor (TF) ranging from 0.08 to 0.43. These results indicated that TSS-H could be absorbed by rice roots and conducted to the above-ground parts of rice plants. This study fills the data gap in the environmental risk and food safety assessment of agricultural silicone spray adjuvants. © 2024 Society of Chemical Industry.

The Transformation of Per- and Polyfluoroalkyl Substances in the Aquatic Environment of a Fluorochemical Industrial Park

Jiangsu High-Tech Fluorochemical Industrial Park in Changshu City, Jiangsu Province, is the largest fluorochemical industrial park in Asia. The occurrence of per- and polyfluoroalkyl substances (PFASs) in surface water and widespread local plants was investigated in Jiangsu High-Tech Fluorochemical Industrial Park. Thirty-two target PFASs were detected in dissolved-phase, particle-phase and plant samples. The concentrations of total PFASs ranged from 1650 to 8250 ng/L in the dissolved-phase samples, 132 to 6810 ng/g dw in the particle-phase samples and 25.8 to 9460 ng/g dw in different plant tissues. Perfluorohexanoic acid (PFHxA), Perfluorooctanoate acid (PFOA) and 6:2 fluorotelomer carboxylic acid (6:2 FTCA) were predominant PFASs and contributed 80−91% to ΣPFAS in water samples. A total of 67 emerging PFAS were identified in all samples using nontargeted analysis. Typha orientalis showed better accumulation ability, with an average ΣPFAS concentration of 3450 ng/g dw and the highest root concentration factor (RCF) of 171. Typha orientalis, Eichhornia crassipes and Alternanthera sessilis have potential for use in PFAS phytostabilization.

Comparative uptake, translocation and metabolism of phenamacril in crops under hydroponic and soil cultivation conditions

Many studies investigate the plant uptake and metabolism of xenobiotics by hydroponic experiments, however, plants grown in different conditions (hydroponic vs. soil) may result in different behaviors. To explore the potential differences, a comparative study on the uptake, translocation and metabolism of the fungicide phenamacril in crops (wheat/rice) under hydroponic and soil cultivation conditions was conducted. During 7–14 days of exposure, the translocation factors (TFs) of phenamacril were greatly overestimated in hydroponic-wheat (3.6–5.2) than those in soil-wheat systems (1.1–2.0), with up to 3.3 times of difference between the two cultivation systems, implying it should be cautious to extrapolate the results obtained from hydroponic to field conditions. M-144 was formed in soil pore water (19.1–29.9 μg/L) in soil-wheat systems but not in the hydroponic solution in hydroponics; M-232 was only formed in wheat shoots (89.7–103.0 μg/kg) under soil cultivation conditions, however, it was detected in hydroponic solution (20.1–21.2 μg/L), wheat roots (146.8–166.0 μg/kg), and shoots (239.2–348.1 μg/kg) under hydroponic conditions. The root concentration factors (RCFs) and TFs of phenamacril in rice were up to 2.4 and 3.6 times higher than that in wheat for 28 days of the hydroponic exposure, respectively. These results highlighted that cultivation conditions and plant species could influence the fate of pesticides in crops, which should be considered to better assess the potential accumulation and transformation of pesticides in crops.

Uptake, accumulation and metabolism of UV-320 in vegetables and its impact on growth and quality

UV-320 is classified as a Substance of Very High Concern (SVHC) by the European Chemicals Agency and has attracted significant attention due to its presence in the environment. Understanding the uptake, translocation and metabolic patterns of UV-320 in vegetables is essential for assessing their ability to bioaccumulate and potential risks to human health. In this study, we investigated the uptake and translocation of UV-320 in lettuce and radish by hydroponic experiments. The results showed that the root concentration factors (Croot/Csolution, RCF) of lettuce and radish were in the range of 47.9 to 464 mL/g and 194 to 787 mL/g, respectively. The transfer factors (Cshoot/Croot, TF) were observed to be 0.001–0.012 for lettuce and 0.02–0.05 for radish. Additionally, non-targeted screening identified twelve phase I and one phase II metabolites of UV-320 in vegetables, which were confirmed based on their molecular formulas and structures. The metabolic pathways involving oxidation, ketonylation and deamination were proposed in vegetables. Also, we have observed that UV-320 inhibits the growth of vegetables. Meanwhile, we evaluated the health risk of UV-320 in lettuce and radish and found that the consumption of lettuce is relatively safe, while the consumption of radish has a risk of HQ >1 for both adults and children, which should be seriously considered. This study provides valuable insights into the behavior and ecological risks of UV-320 in the environment.

Potential and risks of water reuse in Brandenburg (Germany) – an interdisciplinary case study

Abstract For Brandenburg, a region in Germany with increasing water shortage and drought events, water reuse can counteract competition scenarios between drinking water supply, agricultural irrigation, and industrial use. Centralized and decentralized sources for reclaimed water are found to potentially substitute 245 or 28% of irrigation water, respectively, in agriculture production in Brandenburg. For such a reuse scenario, the fate of organic micro-pollutants is examined for diatrizoate (DZA) and carbamazepine (CBZ). Retention in local sandy soil and transfer into roots and leaves of arugula are analyzed in lysimeter studies and greenhouse pot experiments. Vertical transport was found for DZA and accumulation in or on arugula roots with a root concentration factor of 1,925 ± 34% but a low bioconcentration factor due to intrinsic molecule properties. CBZ was not found to be mobile in the sandy soil but accumulates in arugula roots and leaves by factors of 70 ± 7% and 155 ± 12%, respectively. Further research on potential plant uptake and groundwater enrichment for more substances is highly recommended as well as tertiary wastewater treatment prior to water reuse.

Distribution and transfer rules of polycyclic aromatic hydrocarbons in soil-wheat ecosystems in China.

The translocation and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) in the soil-crop system have important implications for the fate of PAHs and human health. This study summarized the concentrations of 16 priority PAHs in the soils and various parts of mature winter wheat in China, sourced from a screening of previous literature in English and Chinese databases. The study analyzes the distribution characteristics, transfer patterns, and human health risks of PAHs in sites studied in Shaanxi, Henan, and Shandong provinces. The results showed that the concentrations of Σ16 PAHs in the rhizosphere soil of wheat ranged from 10.30 to 893.68 ng/g, in descending order of Shaanxi > Henan > average > Shandong. In sites with mild to moderate contamination (200 < Σ16 PAHs < 600 ng/g; i.e., Henan and Shaanxi), the concentration of Σ16 PAHs in the roots was higher than that in the stems or the grains, while in contamination-free sites (Σ16 PAHs < 200 ng/g; i.e., Shandong), the highest concentration of Σ16 PAHs was found in the stems. Generally, the concentrations of PAHs increased in the order of roots-stems-grains. The predominant PAHs in each part of wheat were 2- or 3-ring compounds, with five- or six-ring PAHs being more prevalent in wheat from Shanghe, Shandong. The bioaccumulation factors of different wheat parts from Shaanxi and Henan were consistently smaller than 1, and low- and medium-ring (2-4 rings) PAHs had bigger bioconcentration factors than high-ring (5-6 rings) PAHs. However, the accumulation of PAHs in the aboveground parts of wheat was larger than that in the underground parts of the Shandong sites. The linear regression relationship between the octanol-water partition coefficient and root concentration factor (RCF) of PAHs reflected that low and medium-ring PAHs were more easily absorbed by wheat roots than high-ring PAHs in Shaanxi and Henan. Our assessment of the health risks of oral wheat intake in adults and children by the incremental lifetime cancer risk (ILCR) model found a potential carcinogenic risk for both age groups in each province, with higher risks in adults than in children.

Uptake, accumulation and toxicity of short chain chlorinated paraffins to wheat (Triticum aestivum L.)

Short chain chlorinated paraffins (SCCPs) are ubiquitous persistent organic pollutants. They have been widely detected in plant-based foods and might cause adverse impacts on humans. Nevertheless, uptake and accumulation mechanisms of SCCPs in plants remain unclear. In this study, the soil culture data indicated that SCCPs were strongly absorbed by roots (root concentration factor, RCF>1) yet limited translocated to shoots (translocation factor<1). The uptake mechanism was explored by hydroponic exposure, showing that hydrophobicity and molecular size influenced the root uptake and translocation of SCCPs. RCFs were significantly correlated with logKow values and molecular weights in a parabolic curve relationship. Besides, it was extremely difficult for SCCPs to translocate from shoots back to roots via phloem. An active energy-dependent process was proposed to be involved in the root uptake of SCCPs, which was supported by the uptake inhibition by the low temperature and metabolic inhibitor. Though SCCPs at environmentally relevant concentrations had no negative impacts on root morphology and chlorophyll contents, it caused obvious changes in cellular ultrastructure of root tip cells and induced a significant increase in superoxide dismutase activity. This information may be beneficial to moderate crop contamination by SCCPs, and to remedy soils polluted by SCCPs with plants.

Contribution of molecular structures and quantum chemistry technique to root concentration factor: An innovative application of interpretable machine learning

Root concentration factor (RCF) is a significant parameter to characterize uptake and accumulation of hazardous organic contaminants (HOCs) by plant roots. However, complex interactions among chemicals, plant roots and soil make it challenging to identify underlying mechanisms of uptake and accumulation of HOCs. Here, nine machine learning techniques were applied to investigate major factors controlling RCF based on variable combinations of molecular descriptors (MD), MACCS fingerprints, quantum chemistry descriptors (QCD) and three physicochemical properties related to chemical-soil-plant system. Compared to models with variables including MACCS fingerprints or solitary physicochemical properties, the XGBoost-6 model developed by the variable combination of MD, QCD and three physicochemical properties achieved the most remarkable performance, with R2 of 0.977. Model interpretation achieved by permutation variable importance and partial dependence plots revealed the vital importance of HOCs lipophilicity, lipid content of plant roots, soil organic matter content, the overall deformability and the molecular dispersive ability of HOCs for regulating RCF. The integration of MD and QCD with physicochemical properties could improve our knowledge of underlying mechanisms regarding HOCs accumulation in plant roots from innovative structural perspectives. Multiple variables combination-oriented performance improvement of model can be extended to other parameters prediction in environmental risk assessment field.

Uptake and Biotransformation of Spirotetramat and Pymetrozine in Lettuce (Lactuca sativa L. var. ramosa Hort.).

Here, we investigated the uptake, transport, and subcellular distribution of the pesticides pymetrozine and spirotetramat, and spirotetramat metabolites B-enol, B-glu, B-mono, and B-keto, under hydroponic conditions. Spirotetramat and pymetrozine exhibited high bioconcentrations in lettuce roots, with both having root concentration factor (RCF) values >1 after exposure for 24 h. The translocation of pymetrozine from roots to shoots was higher than that of spirotetramat. Pymetrozine is absorbed in roots mainly via the symplastic pathway and is primarily stored in the soluble fraction of lettuce root and shoot cells. The cell wall and soluble fractions were the major enrichment sites of spirotetramat and its metabolites in root cells. Spirotetramat and B-enol were mainly enriched in the soluble fractions of lettuce shoot cells, whereas B-keto and B-glu accumulated in cell walls and organelles, respectively. Both symplastic and apoplastic pathways were involved in spirotetramat absorption. Pymetrozine and spirotetramat uptake by lettuce roots was passive, with no aquaporin-mediated dissimilation or diffusion. The findings of this study enhance our understanding of the transfer of pymetrozine, spirotetramat, and spirotetramat metabolites from the environment to lettuce, and their subsequent bioaccumulation. This study describes a novel approach for the efficient management of lettuce pest control using spirotetramat and pymetrozine. At the same time, it is of great significance to evaluate the food safety and environmental risks of spirotetramat and its metabolites.

Development, Evaluation, and Application of Machine Learning Models for Accurate Prediction of Root Uptake of Per- and Polyfluoroalkyl Substances.

Machine learning (ML) models were developed for understanding the root uptake of per- and polyfluoroalkyl substances (PFASs) under complex PFAS-crop-soil interactions. Three hundred root concentration factor (RCF) data points and 26 features associated with PFAS structures, crop properties, soil properties, and cultivation conditions were used for the model development. The optimal ML model, obtained by stratified sampling, Bayesian optimization, and 5-fold cross-validation, was explained by permutation feature importance, individual conditional expectation plot, and 3D interaction plot. The results showed that soil organic carbon contents, pH, chemical logP, soil PFAS concentration, root protein contents, and exposure time greatly affected the root uptake of PFASs with 0.43, 0.25, 0.10, 0.05, 0.05, and 0.05 of relative importance, respectively. Furthermore, these factors presented the key threshold ranges in favor of the PFAS uptake. Carbon-chain length was identified as the critical molecular structure affecting root uptake of PFASs with 0.12 of relative importance, based on the extended connectivity fingerprints. A user-friendly model was established with symbolic regression for accurately predicting RCF values of the PFASs (including branched PFAS isomerides). The present study provides a novel approach for profound insight into the uptake of PFASs by crops under complex PFAS-crop-soil interactions, aiming to ensure food safety and human health.

The physiological effect of organophosphate flame retardants (OPFRs) on wheat (Triticum aestivum L.) seed germination and seedling growth under the presence of copper.

This study investigated the physiological and biochemical impacts of organophosphate flame retardants (OPFRs) on wheat (Triticum aestivum L.) germination and growth performance in the presence and absence of copper. The study evaluated seed germination, growth, OPFRs concentrations, chlorophyll fluorescence index (Fv/Fm and Fv/F0), and antioxidant enzyme activity. It also calculated the root accumulation of OPFRs and their root-stem translocation. At the germination stage, at a concentration of 20 μg·L-1 OPFR exposure, wheat germination vigor, root, and shoot lengths were significantly decreased compared to the control. However, the addition of a high concentration of copper (60 mg·L-1) decreased by 80%, 82%, and 87% in the seed germination vitality index and root and shoot elongation, respectively, compared to 20 μg·L-1 of OPFR treatment. At the seedling stage, a concentration of 50 μg·L-1 of OPFRs significantly decreased by 42% and 5.4% in wheat growth weight and the photochemical efficiency of photosystem II (Fv/Fm) compared to the control. However, the addition of a low concentration of copper (15 mg·L-1) slightly enhanced the growth weight compared to the other two co-exposure treatments, but the results were not significant (p > 0.05). After 7 days of exposure, the activity of superoxide dismutase (SOD) and malondialdehyde (MDA) (indicates lipid peroxidation) content in wheat roots significantly increased compared to the control and was higher than in leaves. MDA contents in wheat roots and shoots were decreased by 18% and 6.5% when OPFRs were combined with low Cu treatment compared with single OPFRs treatment, but SOD activity was slightly improved. These results suggest that the co-exposure of copper and OPFRs enhances reactive oxygen species (ROS) production and oxidative stress tolerance. Seven OPFRs were detected in wheat roots and stems, with root concentration factors (RCFs) and translocation factors (TFs) ranging from 67 to 337 and 0.05 to 0.33, respectively, for the seven OPFRs in a single OPFR treatment. The addition of copper significantly increased OPFR accumulation in the root and aerial parts. In general, the addition of a low concentration of copper promoted wheat seedling elongation and biomass and did not significantly inhibit the germination process. OPFRs could mitigate the toxicity of low-concentration copper on wheat but had a weak detoxification effect on high-concentration copper. These results indicated that the combined toxicity of OPFRs and Cu had antagonistic effects on the early development and growth of wheat.

Degradation of 8:2 fluorotelomer carboxylic acid (8:2 FTCA) by plants and their co-existing microorganisms

8:2 fluorotelomer carboxylic acid (8:2 FTCA), an important precursor of perfluorocarboxylic acids (PFCAs), is widely detected in environment and biotas. Hydroponic exposures were conducted to investigate the accumulation and metabolism of 8:2 FTCA in wheat (Triticum aestivum L.) and pumpkin (Cucurbita maxima L.). Endophytic and rhizospheric microorganisms co-existing with the plants were isolated to investigate their contributions to degrade 8:2 FTCA. Wheat and pumpkin roots could take up 8:2 FTCA efficiently with the root concentration factor (RCF) as 5.78 and 8.93, respectively. 8:2 FTCA could be biotransformed to 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA), 7:3 fluorotelomer carboxylic acid (7:3 FTCA), and seven PFCAs with 2–8 carbon chain length in plant roots and shoots. Cytochromes P450 (CYP450) and glutathione-S-transferase (GST) activities in plants were significantly increased, while flavin-dependent monooxygenases (FMOs) activities were not changed, suggesting that CYP 450 and GST were involved in the transformation of 8:2 FTCA in plant tissues. Twelve 8:2 FTCA-degrading endophytic (8 strains) and rhizospheric (4 strains) bacterial strains were isolated from root interior, shoot interior and rhizosphere of plants, respectively. These bacteria were identified as Klebsiella sp. based on the morphology and 16S rDNA sequence, and they could biodegrade 8:2 FTCA to intermediates and stable PFCAs.

Quantifying the Root-to-Shoot Transfer of 4,4'-Methylenedianiline Using Pressure Chamber and Intact Plant Methods.

The high-production-volume chemical 4,4'-methylenedianiline (4,4'-MDA) is an aromatic amine used to manufacture 4,4'-methylenedianiline diisocyanate for polyurethane production. Based on 4,4'-MDA's octanol/water partition coefficient (KOW ) and correlations with the transpiration stream concentration factor (TSCF), significant plant uptake and root-to-shoot transfer are predicted. However, most correlations between KOW and TSCF were developed for neutral organics and may not be applicable for ionizable bases such as 4,4'-MDA. To investigate, TSCF values for 4,4'-MDA were measured using pressure chamber and intact plant approaches for tomato, soybean, and wheat (intact plants only). 14 C-labeled 4,4'-MDA was used to increase analytical sensitivity and facilitate measurement of distribution within plant tissues. The TSCF of 14 C-MDA determined using the pressure chamber method was 0.04 ± 0.00 for tomato and 0.17 ± 0.10 for soybean. These values were lower than predicted from log KOW and within the range of values for 14 C-pyrene also measured in our study (0.14 ± 0.00 for tomato and 0.16 ± 0.09 for soybean). The TSCF values calculated from measurements made from intact plants grown to maturity were statistically equivalent to those obtained from the pressure chamber method for soybean and tomato. The distributions of 14 C within the three plants species were similar, with the roots > leaves ≈ stems > fruit. The log root concentration factors for 4,4'-MDA ranged from 3.68 to 4.33 for the three plant species. This finding indicates that the aromatic amine sorption to root materials is much greater than would be predicted based on its log KOW and may be the reason for the limited root-to-shoot transfer observed in the pressure chamber and intact plant studies. Environ Toxicol Chem 2023;42:655-662. © 2023 SETAC.