Acropetal Translocation Research Articles

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.

Structure-Dependent Distribution, Metabolism, and Toxicity Effects of Alkyl Organophosphate Esters in Lettuce (Lactuca sativa L.).

This study provides a comprehensive investigation into the structure-dependent uptake, distribution, biotransformation, and potential toxicity effects of alkyl organophosphate esters (OPEs) in hydroponic lettuce (Lactuca sativa L.). Trimethyl, triethyl, and tripropyl phosphates were readily absorbed and acropetally translocated, while tributyl, tripentyl, and trihexyl phosphates accumulated mainly in lateral roots. The acropetal translocation potential was negatively associated with log Kow values. Trimethyl and triethyl phosphates are less prone to biotransformation, while a total of 14 novel hydrolysis, hydroxylated, and conjugated metabolites were identified for other OPEs using nontarget analysis. The extent of hydroxylation decreases from tripropyl phosphate to trihexyl phosphate, but multiple hydroxylations occurred more frequently on longer chain OPEs. Further comparative toxicity test revealed that hydrolyzed and hydroxylated metabolites have stronger toxic effects on Ca2+-dependent protein kinases (CDPK) than their parent OPEs. Dibutyl 3-hydroxybutyl phosphate particularly induces upregulation of CDPK in lateral roots of lettuce, probably associated with adenine reduction that may play an important role in the self-defense and detoxification processes. This study contributes to understanding the uptake and transformation behaviors of alkyl OPEs as well as their associations with a toxic effect on lettuce. This emphasizes the necessary evaluation of the environmental risk of the use of OPEs, particularly focusing on their hydroxylated metabolites.

Co-exposure with Copper Alters the Uptake, Accumulation, Subcellular Distribution, and Biotransformation of Organophosphate Triesters in Rice (Oryza sativa L.).

This study investigated the uptake pathways, acropetal translocation, subcellular distribution, and biotransformation of OPEs by rice (Oryza sativa L.) after Cu exposure. The symplastic pathway was noted as the major pathway for the uptake of organophosphate triesters (tri-OPEs) and diesters (di-OPEs) by rice roots. Cu exposure enhanced the accumulation of tri-OPEs in rice roots, and such enhancement was positively correlated with Cu concentrations, attributing to the Cu-induced root damage. The hydrophilic Cl-OPEs in the cell-soluble fraction of rice tissues were enhanced after Cu exposure, while the subcellular distributions of alkyl- and aryl-OPEs were not affected by Cu exposure. Significantly higher biotransformation rates of tri-OPEs to di-OPEs occurred in leaves, followed by those in stems and roots. Our study reveals the mechanisms associated with the uptake, translocation, and biotransformation of various OPEs in rice after Cu exposure, which provides new insights regarding the phytoremediation of soils cocontaminated with heavy metal and OPEs.

Insights into the Enantiomeric Uptake, Translocation, and Distribution of Triazole Chiral Pesticide Mefentrifluconazole in Wheat (Triticum aestivum L.).

The uptake, translocation, and accumulation of mefentrifluconazole (MFZ), an innovative chiral triazole fungicide, in plants at the enantiomeric level are still unclear. Herein, we investigated the patterns and mechanisms of enantiomeric uptake, bioaccumulation, and translocation through several experiments. Rac-MFZ shows the strongest uptake and bioaccumulation capacity in wheat compared with its enantiomers, while S-(+)-MFZ has the highest translocation potential. Molecular docking provided evidence of the stronger translocation ability of S-(+)-MFZ than R-(-)-MFZ. Split-root experiments showed that MFZ and its enantiomers could undergo long-distance transport within the wheat. Active transport or facilitated and simple diffusion may be involved in the wheat uptake of MFZ. The limited acropetal translocation capability of MFZ may be attributed to the dominant uptake pathway of apoplastic. The concentrations of Rac-MFZ in different subcellular fractions varied greatly. In summary, this study provides novel insights for further understanding the behaviors of MFZ and its enantiomers in plants.

Biophoton emission-based approach of the effects of systemic insecticides on the survival of Eurydema ventralis Kolenati, 1846 (Hemiptera: Pentatomidae) and on the photosynthetic activity of oilseed rape

The choice of effective crop protection technologies is a key factors in the economical production of oilseed rape. Insecticides belonging to the group of active substances butenolides and diamides are active substances available as seed treatments in oilseed rape and promising control tools in the crop protection technologies. Our laboratory experiment demonstrated that the experimental insecticides flupyradifurone and cyantraniliprole are both effective against Eurydema ventralis (Hemiptera: Pentatomidae) when used as a seed and in-crop treatments, but there is a fundamental difference in their insect mortality inducing effects. Flupyradifurone was found to have a total mortality 96 h after application based on basipetal translocation. In the case of cyantraniliprole, the insecticidal effect of the same treatment was 27% less. The experiment showed that the acropetal translocation of the tested active substances after seed treatment did not induce efficacy comparable to that of the basipetal translocation. The study of the biophoton emission of the plants demonstrated a verifiable correlation between the different application methods of the insecticides and the photon emission intensity per unit plant surface area. In conclusion, the systematic insecticides tested, in addition to having the expected insecticidal effect, interfere with plant life processes by enhancing photosynthetic activity.

Laccase-induced decontamination and humification mechanisms of estrogen in water-crop matrices.

Enzymatic humification plays a crucial biogeochemical role in eliminating steroidal estrogens and expanding organic carbon stocks. Estrogenic contaminants in agroecosystems can be taken up and acropetally translocated by crops, but the roles of laccase-triggered rhizospheric humification (L-TRH) in pollutant dissipation and plant uptake remain poorly understood. In this study, the laccase-induced decontamination and humification mechanisms of 17β-estradiol (E2) in water-crop media were investigated by performing greenhouse pot experiments with maize seedlings (Zea mays L.). The results demonstrated that L-TRH effectively dissipated E2 in the rhizosphere solution and achieved the kinetic constants of E2 dissipation at 10 and 50 μM by 8.05 and 2.75 times as much as the treatments without laccase addition, respectively. The copolymerization of E2 and root exudates (i.e. phenols and amino acids) consolidated by L-TRH produced a larger amount of humified precipitates with the richly functional carbon architectures. The growth parameters and photosynthetic pigment levels of maize seedlings were greatly impeded after a 120-h exposure to 50 μM E2, but L-TRH motivated the detoxication process and thus mitigated the phytotoxicity and bioavailability of E2. The tested E2 contents in the maize tissues initially increased sharply with the cultivation time but decreased steadily. Compared with the treatment without laccase addition, the uptake and accumulation of E2 in the maize tissues were obviously diminished by L-TRH. E2 oligomers such as dimer, trimer, and tetramer recognized in the rhizosphere solution were also detected in the root tissues but not in the shoots, demonstrating that the acropetal translocation of E2 oligomers was interrupted. These results highlight a promising strategy for decontaminating estrogenic pollutants, boosting rhizospheric humification, and realizing low-carbon emissions, which would be beneficial for agroenvironmental bioremediation and sustainability.

Translocation of fungicides and their efficacy in controlling Phellinus noxius, the cause of brown root rot disease.

Brown root rot disease (BRRD), caused by Phellinus noxius, is an important tree disease in tropical/subtropical areas. To improve chemical control of BRRD and deter emergence of fungicide resistance in P. noxius, this study investigated control efficacies and systemic activities of fungicides with different modes of action. Fourteen fungicides with 11 different modes of action were tested for inhibitory effects in vitro on 39 P. noxius isolates from Taiwan, Hong Kong, Malaysia, Australia, and Pacific Islands. Cyproconazole, epoxiconazole, and tebuconazole (FRAC 3, target-site G1) inhibited colony growth of P. noxius by 99.9 to 100% at 10 ppm and 97.7 to 99.8% at 1 ppm. The other effective fungicide was cyprodinil + fludioxonil (FRAC 9 + 12, target-site D1 + E2), which showed growth inhibition of 96.9% at 10 ppm and 88.6% at 1 ppm. Acropetal translocation of six selected fungicides was evaluated in bishop wood (Bischofia javanica) seedlings by immersion of the root tips in 100 ppm of each fungicide, followed by liquid or gas chromatography tandem-mass spectrometry analyses of consecutive segments of root, stem, and leaf tissues at 7- and 21-days post-treatment. Bi-directional translocation of the fungicides was also evaluated by stem injection of fungicide solutions. Cyproconazole and tebuconazole were the most readily absorbed by roots and efficiently transported acropetally. Greenhouse experiments suggested that cyproconazole, tebuconazole, and epoxiconazole have a slightly higher potential for controlling BRRD than mepronil, prochloraz, and cyprodinil + fludioxonil. Because all tested fungicides lacked basipetal translocation, soil drenching should be considered instead of trunk injection for their use in BRRD control.

Impact analysis of different applications of cyantraniliprole on control of horse chestnut leaf miner (Cameraria ohridella) larvae supported by biophoton emission

Cameraria ohridella is one of the most invasive pests of horse chestnut. Cyantraniliprole is one of the most perspectively active insecticides, which can transport within the plant in several ways, and its efficacy against this pest has not yet been tested. All three modes of application were effective against the target pest, but there was a difference in the time of action between them. However, no demonstrable difference in the speed of action was detected between the doses used. A more intense rate of acropetal translocation was confirmed compared to basipetal translocation. A trend-like effect between the applied concentration of cyantraniliprole and the photon emission intensity per unit area of plant tissue was observed in the translaminar and acropetal treatment settings. In both cases, a clear increase in photon emission was observed, indicating metabolic upregulation. Therefore, we can conclude that biophoton emission measurements can be utilized to conduct efficient pesticide translocation investigations.

Target-site and non–target site mechanisms of pronamide resistance in annual bluegrass (Poa annua) populations from Mississippi golf courses

AbstractThe mitotic-inhibiting herbicide pronamide controls susceptible annual bluegrass (Poa annua L.) pre- and postemergence, but in some resistant populations, postemergence activity is compromised, hypothetically due to a target-site mutation, lack of root uptake, or an unknown resistance mechanism. Three suspected pronamide-resistant (LH-R, SC-R, and SL-R) and two pronamide-susceptible (BS-S and HH-S) populations were collected from Mississippi golf courses. Dose–response experiments were conducted to confirm and quantify pronamide resistance, as well as resistance to flazasulfuron and simazine. Target sites known to confer resistance to mitotic-inhibiting herbicides were sequenced, as were target sites for herbicides inhibiting acetolactate synthase (ALS) and photosystem II (PSII). Pronamide absorption and translocation were investigated following foliar and soil applications. Dose–response experiments confirmed pronamide resistance of LH-R, SC-R, and SL-R populations, as well as instances of multiple resistance to ALS- and PSII-inhibiting herbicides. Sequencing of the α-tubulin gene confirmed the presence of a mutation that substituted isoleucine for threonine at position 239 (Thr-239-Ile) in LH-R, SC-R, SL-R, and BS-S populations. Foliar application experiments failed to identify differences in pronamide absorption and translocation between the five populations, regardless of harvest time. All populations had limited basipetal translocation—only 3% to 13% of the absorbed pronamide—across harvest times. Soil application experiments revealed that pronamide translocation was similar between SC-R, SL-R, and both susceptible populations across harvest times. The LH-R population translocated less soil-applied pronamide than susceptible populations at 24, 72, and 168 h after treatment, suggesting that reduced acropetal translocation may contribute to pronamide resistance. This study reports three new pronamide-resistant populations, two of which are resistant to two modes of action (MOAs), and one of which is resistant to three MOAs. Results suggest that both target site– and translocation-based mechanisms may be associated with pronamide resistance. Further research is needed to confirm the link between pronamide resistance and the Thr-239-Ile mutation of the α-tubulin gene.

Uptake, accumulation, and translocation of organophosphate esters and brominated flame retardants in water hyacinth (Eichhornia crassipes): A field study

Mechanisms underlying the plant uptake, accumulation, and translocation of organophosphate esters (OPEs) and brominated flame retardants (BFRs) in field environments remain ambiguous. To better understand these processes, we selected a typically polluted river with steady flow and rampant water hyacinth (Eichhornia crassipes) and investigated 25 OPEs and 23 BFRs in 24 sets of matched water–plant samples. Both OPEs and BFRs showed high or ultra-high levels in field water hyacinths, statistically positive water–plant/root concentration correlations, and dominant distributions in the roots. Passive root uptake was the dominant route for OPEs and BFRs to enter the water hyacinth. Both OPEs and BFRs in water hyacinth exhibited acropetal translocation from the root and possible basipetal translocation from the leaf. The accumulation and translocation of OPEs in water hyacinth were significantly affected by their substituents and structures, including the chlorination degree, alkyl chain length, side chain, and methylation degree of aryl-substituted OPEs. The translocation of BFRs in water hyacinth also showed close association with their bromination degree, but their accumulation in roots showed anomaly, indicating possible transformations. Overall, the enrichment and behavior of OPEs and BFRs in water hyacinth seemed to be mainly controlled by physicochemical parameters. OPE/BFR concentrations in total suspended particulate (TSP), TSP-associated organic carbon content, TSP concentration, and plant biomass all showed significant effects on their root accumulation and translocations in water hyacinth. This study provides rare field evidences and novel insights into the basipetal translocation of OPEs and BFRs in plants.

Uptake, translocation and subcellular distribution of organophosphate esters in rice by co-exposure to organophosphate esters and copper oxide nanoparticle

This study investigated the influence of copper oxide nanoparticles (CuONPs) and Cu2+ on the uptake, translocation and subcellular distribution of organophosphate esters (OPEs) in rice seedlings using hydroponic experiments. The OPE concentrations in roots and shoots under the OPEs+CuONPs treatment were significantly lower than those with the OPEs+Cu2+ (low level) or OPEs-only treatments, indicating that CuONPs can hinder the uptake of OPEs by root via competitive adsorption under short-term exposure. The plasma membrane permeability and antioxidant enzyme activity implied that CuONPs had a negligible impact on rice seedlings and could even reduce the toxicity of OPEs to rice root. A significant negative correlation between translocation factor and octanol-water partition coefficient was observed for the three treatments, implying an important role of hydrophobicity on the acropetal translocation of OPEs. Relatively hydrophobic OPEs were mainly adsorbed on cell wall, while hydrophilic OPEs were concentrated in cell sap. The subcellular distributions of OPEs in the OPEs+Cu2+ (high level) or OPEs+CuONPs treatments slightly differed from the OPEs-only treatment, indicating that the coexistence of Cu2+ or CuONPs with OPEs can influence the subcellular distribution of OPEs by affecting their adsorption or partitioning processes. Inhibition experiment suggested that root uptake of OPEs is a non-energy-consuming facilitated diffusion mediated by aquaporin channel, which can be slightly changed by the co-exposure of CuONPs. This study improved the understanding of uptake and translocation of OPEs by rice under the co-exposure to CuONPs.

Mechanistic insights into phenanthrene acropetal translocation via wheat xylem: Separation and identification of transfer proteins.

Polycyclic aromatic hydrocarbons (PAHs) have the potential to cause cancer, teratogenicity, and mutagenesis in humans. Long-term plant safe production relies on how PAHs are transported and coordinated across organs. However, the acropetal transfer mechanism of PAHs in staple crop stems, particularly in xylem, a critical path, is unknown. Herein, we first confirmed the presence of specific interaction between the proteins and phenanthrene by employing the magnetic phenanthrene-bound bead immunoassay and label free liquid chromatograph mass spectrometer (LC-MS/MS), suggesting that peroxidase (uniprot accession: A0A3B5XXD0) and unidentified proteins (uniprot accession: A0A3B6LUC6) may function as the carriers to load and acropetally translocate phenanthrene (a model PAH) in wheat xylem. This specified binding of protein-phenanthrene may form through hydrophobic interactions in the conservative binding region, as revealed by protein structural investigations and molecular docking. To further investigate the role of these proteins in phenanthrene solubilization, phenanthrene exposure was conducted: a substantial quantity of peroxidase was produced; an unusually high expression of uncharacterized proteins was observed, indicating their positive effects in the acropetal transfer of phenanthrene in wheat xylem. These data confirmed that the two proteins are crucial in the solubilization of phenanthrene in wheat xylem sap. Our findings provide fresh light on the molecular mechanism of PAH loading in plant xylem and techniques for ensuring the security of staple crops and improving the efficacy of phytoremediation in a PAH-contaminated environment.

Identification of Novel Organophosphate Esters in Hydroponic Lettuces (Lactuca sativa L.): Biotransformation and Acropetal Translocation.

The absorption, translocation, and biotransformation behaviors of organophosphate esters (OPEs) and diesters (OPdEs) in a hydroponic system were investigated. The lateral root was found as the main accumulation and biotransformation place of OPEs and OPdEs in lettuce. The nontarget analysis using high-resolution mass spectrometry revealed five hydroxylated metabolites and five conjugating metabolites in the OPE exposure group, among which methylation, acetylation, and palmitoyl conjugating OPEs were reported as metabolites for the first time. Particularly, methylation on phosphate can be a significant process for plant metabolism, and methyl diphenyl phosphate (MDPP) accounted for the majority of metabolites. The translocation factor values of most identified OPE metabolites are negatively associated with their predicted logarithmic octanol-water partitioning coefficient (log Kow) values (0.75-2.45), indicating that hydrophilicity is a dominant factor in the translocation of OPE metabolites in lettuce. In contrast, palmitoyl conjugation may lead to an enhanced acropetal translocation and those with log Kow values < 0 may have limited translocation potential. Additionally, OPE diesters produced from the biotransformation of OPEs in lettuce showed a higher acropetal translocation potential than those exposed directly. These results further emphasize the necessity to consider biotransformation as an utmost important factor in the accumulation and acropetal translocation potential of OPEs in plants.

The Above-Ground Part of Submerged Macrophytes Plays an Important Role in Ammonium Utilization.

As a paradoxical nutrient in water ecosystems, ammonium can promote plants growth under moderate concentration, but excess of it causes phytotoxic effects. Previous research has revealed that glutamate dehydrogenase in the above-ground part of submerged macrophytes plays an important role in ammonium detoxification. However, the strategies of ammonium utilization at the whole plant level of submerged macrophytes are still unclear and the role of the above-ground part in nutrient utilization has not been clearly elucidated in previous studies, hence, directly influencing the application of previous theory to practice. In the present research, we combined the methods of isotopic labeling and enzyme estimation to investigate strategies of ammonium utilization by the submerged macrophytes. The results showed that when [NH4+-N] was 50 mg L–1, 15N taken up through the above-ground parts was 13.24 and 17.52 mg g–1 DW, while that of the below-ground parts was 4.24 and 8.54 mg g–1 DW in Potamogeton lucens and Myriophyllum spicatum, respectively. The ratios of 15N acropetal translocation to uptake were 25.75 and 35.69%, while those of basipetal translocation to uptake were 1.93 and 4.09% in P. lucens and M. spicatum, respectively. Our results indicated that the above-ground part was not only the main part for ammonium uptake, but also the major pool of exogenous ammonium. Besides, the dose–response curve of GDH (increased by 20.9 and 50.2% under 15 and 50 mg L–1 [NH4+-N], respectively) exhibited by the above-ground parts of M. spicatum indicates that it is the main site for ammonium assimilation of the tolerant species. This study identifies the ammonium utilization strategy of submerged macrophytes and reveals the important role of the above-ground part in nutrient utilization providing new insight into the researches of nutrient utilization by plants and theoretical supports for water restoration by phytoremediation.

Uptake, translocation and distribution of cyantraniliprole in rice planting system

While cyantraniliprole has been frequently used in rice fields, knowledge of the uptake, translocation and distribution of cyantraniliprole in rice planting systems is still largely unexplored. Plant uptake is a crucial factor in determining how cyantraniliprole moves through the food chain. Understanding the uptake, translocation and distribution of cyantraniliprole in rice planting system is essential to predicting its accumulation in rice and potential human exposure. Herein, the uptake process of cyantraniliprole in a hydroponic-rice system was systematically investigated. Results showed that cyantraniliprole was easily absorbed by rice roots via a passive diffusion process through the apoplastic pathway and then translocated upward through the xylem, but its acropetal translocation was limited. Cyantraniliprole in shoots can also be downward translocated through the phloem, although only to a limited extent, showing rice plants' weak phloem movement capacity. Furthermore, cyantraniliprole had a short half-life in sediment-water system and dissipated faster in anaerobic than aerobic conditions. At the equilibrium stage of a sediment-water system, cyantraniliprole is preferentially partitioned to the solid phase. Our study provides a systematic insight into the uptake, translocation and distribution of cyantraniliprole in the rice planting system, which is very helpful for better field cyantraniliprole application and environmental risk assessment.

Mechanistic Insights into Phenanthrene Acropetal Translocation Via Wheat Xylem: Separation and Identification of Transfer Protein

Mechanistic Insights into Phenanthrene Acropetal Translocation Via Wheat Xylem: Separation and Identification of Transfer Protein

Root:shoot balance controls flush phenology and carbohydrate translocation dynamics in citrus (Citrus x sinensis) trunk.

Flush shoot growth presents a fluctuation pattern alternating with root growth. The cyclic pattern determines the balance of root:shoot and can affect the direction and speed of carbohydrate translocation during the vegetative growth period. In this study, we used water deficit to limit corresponding growth in sweet orange (Citrus x sinensis) "OLL 4" grafted on "US-942" rootstock, and then observed the changes of translocation dynamics between two flush statuses. Our first hypothesis was that water deficit would reduce root growth and extend the root growth phase during the growth cycle, delaying the following flush. We then tested the related second hypothesis that shoot flushes would switch the direction and slow the speed of carbohydrate transport due to fluctuation between single and dual sinks. After recovery from a severe deficit, the flush was synchronized and emerged within 2 weeks. Mild and moderate water-deficit plants showed a delayed new flush. Next, we used a 14 C-labeling method to test whether translocation was affected by the presence of new flush. Basipetal translocation was dominant, but the new flush increased the likelihood of acropetal translocation. Translocation speeds were not different in both directions regardless of flushing status, though speed estimates were highly variable, even though 14 C export from the source leaf increased when new flush was present. The results suggest that flush timing across an environmental gradient is governed by source-sink dynamics. The presence of new flush altered the direction of photoassimilate translocation and rate of leaf export, but stem transport speeds were not distinguishably different.

Uptake, translocation and subcellular distribution of chlorantraniliprole and tetrachlorantraniliprole in maize

This study aimed to investigate the uptake, translocation, and subcellular distribution of chlorantraniliprole (Cap) and tetrachlorantraniliprole (Tca) in maize (Zea mays L.) plants using a hydroponic experiment. Tca mainly accumulated in the roots and stems, while Cap showed better acropetal translocation capacity than Tca. The uptake of Cap was positively correlated with Tca uptake, particularly at the effect of plant transpiration force. Transpiration inhibitor treatments significantly reduced the acropetal translocation of Cap and Tca. The absorption of Cap and Tca in the dead and fresh roots showed a good linear relationship and mainly occurred via the apoplastic pathway. Regarding subcellular distribution, the cell wall was the dominant storage compartment for Cap and Tca. In the protoplast, Cap mainly accumulated in cell soluble fractions, while Tca accumulated in the organelles. This study provides information for the accurate application of maize pest management and is of great significance to environmental risk and food safety assessments.

Micro-distribution of arsenic and polycyclic aromatic hydrocarbons and their interaction in Pteris vittata L.

Interactive effects of inorganic arsenic (As) species and polycyclic aromatic hydrocarbons (PAHs) on their uptake, accumulation and translocation in the hyperaccumulator Pteris vittata L. (P. vittata) were studied hydroponically. The presence of PAHs hindered As uptake and acropetal translocation by P. vittata, decreasing As concentrations by 29.8%–54.5% in pinnae, regardless of the initial As speciation. The inhibitive effect of PAHs was 1.6–8.7 times greater for arsenite [As(III)] than for arsenate [As(V)]. Similarly, inorganic As inhibited the uptake of fluorene (FLU) and benzo[a]pyrene (BaP) by P. vittata roots by 0.4%–21.7% and by 33.1%–69.7%, respectively. Interestingly, coexposure to As and PAHs slightly enhanced the translocation of PAHs by P. vittata with their concentrations increased 0.3 to 0.8 times in shoots, except for the As(III)+BaP treatment. The antagonistic interaction between As and PAHs uptake is likely caused by competitive inhibition or oxidative stress injury. By using synchrotron radiation micro X-ray fluorescence imaging, high concentrations of As were found distributed throughout the microstructures far from main vein of the pinnae when coexposed with PAHs, the opposite of what was observed with exposure to As only. PAHs could also significantly inhibit the accumulation and distribution of As in vascular bundles in rachis treated with As(III). The results of two-photon laser scanning confocal microscopy revealed that PAHs were mainly distributed in the vascular cylinder, epidermal cells, vascular bundles, epidermis and vein tissues, and this was independent of As speciation and treatment. This work offers new positive evidence for the interaction between As and PAHs in P. vittata, presents new information on the underlying mechanisms for interactions of As and PAHs affecting their uptake and translocation within P. vittata L., and provides direction for future research on the mechanisms of PAHs uptake by plants.

Uptake and translocation of organophosphate esters by plants: Impacts of chemical structure, plant cultivar and copper

Organophosphate esters (OPEs) are normally used as flame retardants, plasticizers and lubricants, but have become environmental pollutants. Because OPEs are normally present alongside heavy metals in soils, the effects of interactions between OPEs and heavy metals on plant uptake of OPEs need to be determined. In this study, we investigated the effects of OPEs chemical structure, plant cultivar and copper (Cu) on the uptake and translocation of OPEs by plants. The bioaccumulation of OPEs varied among plant cultivars. They were preferentially enriched in carrot, with the lowest concentrations observed in maize. OPEs with electron-ring substituents (ER-OPEs) exhibited a higher potential for root uptake than did OPEs with open-chain substituents (OC-OPEs), which could be attributed to the higher sorption of ER-OPEs onto root charged surfaces. This was explained by the stronger noncovalent interactions with the electron-rich structure of ER-OPEs. The presence of Cu slightly reduced the distinct difference in the ability of roots to take up OC-OPEs and ER-OPEs. This was explained by the interactions of Cu ions with the electron-rich structure of ER-OPEs, which suppressed the sorption of ER-OPEs on the root surface. A negative relationship between the logarithms of the translocation factor and octanol-water partition coefficient (Kow) was observed in treatments with either OPEs only or OPEs + Cu, implying the significant role of hydrophobicity in the OPEs acropetal translocation. The results will improve our understanding of the uptake and translocation of OPEs by plant cultivars as well as how the process is affected by the chemical structure of OPEs and Cu, leading to improvements in the ecological risk assessment of OPEs in the food chain.