The Role of FveAFB5 in Auxin-Mediated Responses and Growth in Strawberries.

Auxin is a crucial hormone that regulates various aspects of plant growth and development. It exerts its effects through multiple signaling pathways, including the TIR1/AFB-based transcriptional regulation in the nucleus. However, the specific role of auxin receptors in determining developmental features in the strawberry (Fragaria vesca) remains unclear. Our research has identified FveAFB5, a potential auxin receptor, as a key player in the development and auxin responses of woodland strawberry diploid variety Hawaii 4. FveAFB5 positively influences lateral root development, plant height, and fruit development, while negatively regulating shoot branching. Moreover, the mutation of FveAFB5 confers strong resistance to the auxinic herbicide picloram, compared to dicamba and quinclorac. Transcriptome analysis suggests that FveAFB5 may initiate auxin and abscisic acid signaling to inhibit growth in response to picloram. Therefore, FveAFB5 likely acts as an auxin receptor involved in regulating multiple processes related to strawberry growth and development.

Long-term organogenic callus cultivation of Ranunculus illyricus L.: a blueprint for sustainable ex situ conservation of the species in urban greenery.

The growing trend of introducing wild plant species into urban environments necessitates the identification of novel species adapted to prevailing conditions. A promising reservoir of such species may be xerothermic communities where Ranunculus illyricus occurs. This study aimed to establish a micropropagation protocol for R. illyricus using indirect organogenesis. The protocol includes initiation of culture from various explants, callus proliferation, shoot regeneration, multiplication, and concurrent rooting. Callus appeared on most types of vegetative explants tested, but stolons were considered the best due to their good availability, high disinfection (85%), and robust callus production (maximum increase - 363.1%). The growth rate of the callus fresh matter (CFM) obtained from stolons was calculated. Greater CFM was obtained on the medium with the supplemented picloram 8.0 mg L- 1 with kinetin 5.0 mg L- 1 and in second part of experiment on medium with the addition of 2,4-D (2,4-dichlorophenoxyacetic acid) 2.0 mg L- 1 alone or picloram 6.0 mg L- 1 with kinetin 8.0 mg L- 1. Shoot organogenesis was observed on macronutrients B5 (Gamborg medium), micronutrients MS (Murashige and Skoog) medium with the addition of 2.0 mg L- 1 IBA (indole-3-butyric acid) and 4.0 mg L- 1 BAP (6-benzylaminopurine). To document the process of callus differentiation, microscopic preparations were prepared. Subsequently, the regenerated plants underwent acclimatisation and their growth in an ex situ collection was monitored over three growing seasons. In particular, in vitro-origin plants exhibited developmental patterns similar to those of their seed-origin counterparts. The incorporation of R. illyricus into urban landscapes not only increases aesthetic appeal, but also ensures the preservation of valuable genetic resources for this rare species, potentially contributing to effective ex situ conservation in the future. This marks the first scientific report on in vitro cultures of R. illyricus.

Resprouting Response among Savanna Tree Species in Relation to Stem Size, Woody Removal Intensity and Herbicide Application.

Mechanical and chemical methods are widely used to control woody plant encroachment in many African countries. However, very little is known about the effectiveness of these control methods among woody species of different ages. We conducted a field experiment to determine the effects of different tree removal treatments (10%, 20%, 50%, 75% and 100%) and herbicide application (Picloram; 6 mL L-1) on the resprouting ability and vigour of 12 woody plant species. We examined 20 plots (30 m × 30 m) that were each subjected to tree removal, followed by herbicide application on half of the stems for each plot. All the tree species in this study resprouted after cutting. The applied concentration of herbicide significantly reduced the shoot production for Ehretia rigida, Vachellia robusta and Ziziphus mucronata, with a marginal effect for Dichrostachys cinerea. The diameter of stems was an important factor in determining resprouting ability, with shoot production decreasing with increasing stem diameter. However, stem diameter did not affect shoot length and diameter for all species. We found that woody plants are more likely to resprout and survive as juveniles than as adults after cutting and that herbicide only affected four of the twelve species at a concentration of 6 mL L-1. Thus, testing the amount of Picloram needed to kill certain woody species may be of importance for land users in southern African savannas.

Picloram binds to the h1 and h4 helices of HSA domain IIIA at drug binding site 2.

Picloram (PC) is a systemic herbicide that controls herbaceous weeds and woody plants. HSA, the most abundant protein in human physiology, binds to all exogenic and endogenic ligands. PC is a stable molecule (t1/2∼157-513 days) and a potential threat to human health via the food chain. HSA and PC binding study has been done to decipher the location and thermodynamics of binding. It has been studied with prediction tools like autodocking and MD simulation and then confirmed with fluorescence spectroscopy. HSA fluorescence was quenched by PC at pH 7.4 (N state), pH 3.5 (F state), and pH 7.4 with 4.5 M urea (I state) at temperatures 283 K, 297 K, and 303 K. The location of binding was found to be interdomain between II and III which overlaps with drug binding site 2. The binding was spontaneous, and entropy-driven that show a noticeable increase in binding with the increase in temperature. No secondary structure change at the native state has been observed due to binding. The binding results are important to understand the physiological assimilation of PC. In silico predictions and the results of spectroscopic studies unambiguously indicate the locus and nature of the binding.

Analysis of the effect of each plant hormone on the maturation of woodland strawberry fruit in auxin-induced parthenocarpic fruit.

Evaluation of individual roles of plant hormones in fruit development is difficult because various plant hormones function simultaneously. In this study, to analyze the effect of plant hormones on fruit maturation one by one, plant hormones were applied to auxin-induced parthenocarpic woodland strawberry (Fragaria vesca) fruits. As a result, auxin, gibberellin (GA), and jasmonate, but, not abscisic acid and ethylene increased the proportion of ultimately mature fruits. So far, to produce comparable fruit with pollinated fruit in size, auxin with GA treatment was required in woodland strawberry. Picrolam (Pic), the most potent auxin in inducing parthenocarpic fruit, induced fruit which is comparable in size with pollinated fruit without GA. The endogenous GA level and the result of the RNA interference analysis of the main GA biosynthetic gene suggest that a basal level of endogenous GA is essential for fruit development. The effect of other plant hormones was also discussed.

Somatic embryogenesis and plant regeneration from transverse thin cell layers of adult peach palm (Bactris gasipaes) lateral offshoots.

In this work, we report a successful protocol to obtain in vitro peach palm (Bactris gasipaes Kunth) "Diamantes 10" plants through somatic embryogenesis from transverse thin cell layer (TCL) explants, dissected from three sections (basal, medial, and apical) of lateral offshoots of adult plants cultured on different concentrations of 4-amino-3,5,6-trichloropicolonic acid (picloram). After swelling and development of primary callus in all treatments, without any strong effect of explant origin or picloram concentration, it was possible to observe the formation of embryogenic structures and the exact point from where they developed. Browning was also observed and correlated to the induction treatments, although it was not an impairment for the production of embryogenic structures. Subsequent maturation and conversion of somatic embryos into plantlets allowed their acclimatization 17 months after culture initiation (ACI), which was quicker than previous reports with juvenile tissues (from embryos or seed-germinated plantlets). To the best of our knowledge, this is the first report on peach palm regeneration through somatic embryogenesis from TCL explants from adult plants and could constitute, after fine-tuning the acclimatization stage, a tool for mass clonal propagation of elite genotypes of this open-pollinated crop, as well as for the establishment of conservation strategies of in situ gene bank plant accessions endangered due to aging and other threats.

Determination of genotoxic damages of picloram and dicamba with comet assay in Allium cepa rooted in tissue culture and distilled water.

BACKGROUND: Many genotoxicity tests allow us to understand the mechanism of damages on genetic material occurring in living organisms against various physical and chemical agents. One of them is the Comet test. The current study aimed to evaluate genotoxic caused by picloram and dicamba to root meristems of Allium cepa utilizing comet assay. METHODS: Two different protocols were used for rooting and auxin/pesticide application. (i) A. cepa bulbs were rooted in MS medium and then treated with Murashige and Skoog (MS) medium (control) and 0.67, 1.34, 2.01, 2.68, 3.35, 4.02, and 8.04 mg/L of picloram and dicamba using aseptic tissue culture techniques. (ii) A. cepa bulbs were then rooted in bidistilled water and treated with 0 (control), 0.67, 1.34, 2.01, 2.68, 3.35, 4.02, and 8.04 mg/L of picloram and dicamba in distilled water. The A. cepa root tip cells in both treatment groups were examined using comet test to find the possible DNA damaging effects of picloram and dicamba. RESULTS: The results obtained at all the concentrations were statistically compared with their control groups. Almost at all the concentrations of Picloram and dicamba increased comet tail intensity (%) and tail moment in roots treated in MS medium. Two highest concentrations revealed toxic effect. On the other hand, DNA damaging effect of both auxins was only noted on the highest (> 4.02 mg/L) in roots treated in distilled water. CONCLUSIONS: This study approve and confirm genotoxic effects of how growth regulators on plants. These findings give an evidence of DNA damage in A. cepa. Therefore, both picloram and dicamba should only be used in appropriate and recommended concentrations in agriculture to conserve ecosystem and to pose minimum threat to life.

Two Auxinic Herbicides Affect Brassica napus Plant Hormone Levels and Induce Molecular Changes in Transcription.

With the introduction of the new auxinic herbicide halauxifen-methyl into the oilseed rape (Brassica napus) market, there is a need to understand how this new molecule interacts with indigenous plant hormones (e.g., IAA) in terms of crop response. The aim of this study was to investigate the molecular background by using different growth conditions under which three different auxinic herbicides were administered. These were halauxifen-methyl (Hal), alone and together with aminopyralid (AP) as well as picloram (Pic). Three different hormone classes were determined, free and conjugated indole-3-acetic acid (IAA), aminocyclopropane carboxylic acid (ACC) as a precursor for ethylene, and abscisic acid (ABA) at two different temperatures and growth stages as well as over time (2-168 h after treatment). At 15 °C growth temperature, the effect was more pronounced than at 9 °C, and generally, the younger leaves independent of the developmental stage showed a larger effect on the alterations of hormones. IAA and ACC showed reproducible alterations after auxinic herbicide treatments over time, while ABA did not. Finally, a transcriptome analysis after treatment with two auxinic herbicides, Hal and Pic, showed different expression patterns. Hal treatment leads to the upregulation of auxin and hormone responses at 48 h and 96 h. Pic treatment induced the hormone/auxin response already after 2 h, and this continued for the other time points. The more detailed analysis of the auxin response in the datasets indicate a role for GH3 genes and genes encoding auxin efflux proteins. The upregulation of the GH3 genes correlates with the increase in conjugated IAA at the same time points and treatments. Also, genes for were found that confirm the upregulation of the ethylene pathway.

Drop coating deposition Raman (DCDR) spectroscopy of contaminants.

Raman spectroscopy is a useful technique to identify small organic molecules, including contaminants. The drop coating deposition Raman (DCDR) is more sensitive than conventional Raman spectroscopy from solution. It is based on Raman measurement from a small drop dried on a hydrophobic surface where studied molecules are preconcentrated. In this paper, DCDR spectra of dried drops of selected contaminants (food contaminant melamine, fungicide thiram, herbicides bentazon and picloram) on the hydrophobic substrate were acquired for the first time, whereas Raman spectra from stock solutions were impossible to obtain under the same experimental conditions. The lowest DCDR detected concentrations were determined as 6.4 µM, 0.31 µM, 20 µM and 2 µM in deposited concentrations for melamine, thiram, bentazon and picloram, respectively. Therefore, DCDR spectroscopy can serve to detect these molecules in concentrations relevant in food/groundwater contaminations.

High-frequency direct somatic embryogenesis and plantlet regeneration from date palm immature inflorescences using picloram.

BACKGROUND: Date palm (Phoenix dactylifera L.) is a traditional crop in arid and semi-arid areas. Its vegetative propagation can be achieved by offshoots, but possible number of offshoots in mother palm trees is limited. Micropropagation is a highly recommended strategy for obtaining date palm elite cultivars using shoot tip and immature inflorescences. In this study, micropropagation procedure using inflorescence explants of Medjool cv. is described. For culture initiation, explants from different spathe lengths were cultivated on Murashige and Skoog medium (MS) supplemented with picloram at 1.0 and 2.0 mg/l combined with 2iP at 0.5 mg/l alone and with both 2iP and BA at 0.25 mg/l for 24 weeks. The obtained direct globular embryos were transferred to maturation media with 0.1 mg/l picloram alone or combined with both 2iP and ABA separately and together for further development. Additionally, multiplication and rooting media were optimized by different cytokinins and auxins for high frequency of plantlet production. Acclimatization of in vitro plantlets was also investigated. RESULTS: The highest percentage of globular embryo formation was noticed with explants isolated from spathe lengths ranging from 10 to 15 cm. Addition of BA to initiation media with picloram encouraged a significant effect on embryonic culture formation percentage. Incorporation of ABA and 2iP to maturation medium was an effective factor for individual or multiple embryo emergence. Acclimatization of in vitro plantlets having 3-4 roots was successfully accomplished. Irrigation with the full strength solution (MS) encouraged the highest growth vigor degree, leaf number/plant, leaf width, root number, and root thickness degree of ex vitro plants. CONCLUSION: This research provides an advanced regeneration system for large-scale production of date palm from immature inflorescences of Medjool cv. It opens up the prospects of using picloram with different growth regulators for rapid micropropagation of date palm.

Indirect Somatic Embryogenesis and Cryopreservation of Agave tequilana Weber Cultivar 'Chato'.

Agave tequilana Weber cultivar 'Chato' represents an important genetic supply of wild severely in decline populations of 'Chato' for breeding and transformation programs. In this work, the indirect somatic embryogenesis and cryopreservation of Somatic Embryos (SEs) were investigated using the 'Chato' cultivar as a study case. METHODS: Embryogenic calli were induced by the cultivation of 1 cm of young leaves from in vitro plants on MS semisolid medium supplemented with 24.84, 33.13, 41.41, 49.69, and 57.98 µM 4-amino-3,5,6-trichloro-2- pyridinecarboxylic acid (picloram) in combination with 2.21, 3.32, and 4.43 µM 6-benzylaminopurine (BAP). The origin and structure of formed SEs were verified by histological analysis. Cryopreservation studies of SEs were performed following the V-cryoplate technique and using for dehydration two vitrification solutions (PVS2 and PVS3). RESULTS: The highest average (52.43 ± 5.74) of produced SEs and the Embryo Forming Capacity (estimated index 52.43) were obtained using 49.69 µM picloram and 3.32 µM BAP in the culture medium. The highest post-cryopreservation regrowth (83%) and plant conversion rate (around 70%) were achieved with PVS2 at 0 °C for 15 min. CONCLUSION: Our work provides new advances about somatic embryogenesis in Agave and reports the first results on cryopreservation of SEs of this species.

Temperature-enabled reversible "On/Off" switch-like hazardous herbicide picloram voltammetric sensor in agricultural and environmental samples based on thermo-responsive PVCL-tethered MWCNT@Au catalyst.

Picloram (PCR), a vastly utilized chlorinated herbicide, is very stable in water and soil with severe ecological and health impacts. It is necessary to establish a fast and highly sensitive technique for accurately detecting trace level PCR in agricultural and environmental samples. We employed a temperature-responsive poly(N-vinylcaprolactam)-tethered multiwalled carbon nanotubes (MWCNT-PVCL) decorated gold nanoparticles (Au@MWCNT-PVCL) catalyst on the electrochemical sensor for the sensitive "On/Off" switch-like detection of PCR. The effect of temperature-sensitive catalyst surface chemistry on electrocatalytic activity was scrutinized. Results showed that the hydrophilic surface of PVCL at 25 °C (LCST) that immensely upgraded PCR oxidation on the catalyst in the electrochemical reaction, signifying the "On" state. The detection of the Au@MWCNT-PVCL modified electrode ranged from 0.02-183 µM with a low detection limit (LOD) of 1.5 nM at 40 °C toward PCR. The proposed sensor was successfully used to detect PCR in real agricultural and environmental samples.

Functional analysis of auxin receptor OsTIR1/OsAFB family members in rice grain yield, tillering, plant height, root system, germination, and auxinic herbicide resistance.

Auxin regulates almost every aspect of plant growth and development and is perceived by the TIR1/AFB auxin co-receptor proteins differentially acting in concert with specific Aux/IAA transcriptional repressors. Little is known about the diverse functions of TIR1/AFB family members in species other than Arabidopsis. We created targeted OsTIR1 and OsAFB2-5 mutations in rice using CRISPR/Cas9 genome editing, and functionally characterized the roles of these five members in plant growth and development and auxinic herbicide resistance. Our results demonstrated that functions of OsTIR1/AFB family members are partially redundant in grain yield, tillering, plant height, root system and germination. Ostir1, Osafb2 and Osafb4 mutants exhibited more severe phenotypes than Osafb3 and Osafb5. The Ostir1Osafb2 double mutant displays extremely severe defects in plant development. All five OsTIR1/AFB members interacted with OsIAA1 and OsIAA11 proteins in vivo. Root elongation assay showed that each Ostir1/afb2-5 mutant was resistant to 2,4-dichlorophenoxyacetic acid (2,4-D) treatment. Notably, only the Osafb4 mutants were strongly resistant to the herbicide picloram, suggesting that OsAFB4 is a unique auxin receptor in rice. Our findings demonstrate similarities and specificities of auxin receptor TIR1/AFB proteins in rice, and could offer the opportunity to modify effective herbicide-resistant alleles in agronomically important crops.

Modification of the existing maximum residue level for picloram in flowering brassica.

In accordance with Article 6 of Regulation (EC) No 396/2005, the applicant, Dienstleistungszentrum Ländlicher Raum Rheinpfalz, submitted a request to the competent national authority in Germany to modify the existing maximum residue level (MRL) for the active substance picloram in flowering brassica. The data submitted in support of the request were found to be sufficient to derive an MRL proposal for broccoli, cauliflowers and other flowering brassica. Adequate analytical methods for enforcement are available to control the residues of picloram and its conjugates in plant matrices under consideration at the validated limit of quantification (LOQ) of 0.01 mg/kg. Based on the risk assessment results, EFSA concluded that the short-term and long-term intake of residues resulting from the use of picloram according to the reported agricultural practices is unlikely to present a risk to consumer health. The reliable end points, appropriate for use in regulatory risk assessment, are presented..

Different Roles of Auxins in Somatic Embryogenesis Efficiency in Two Picea Species.

The effects of auxins 2,4-D (2,4-dichlorophenoxyacetic acid), NAA (1-naphthaleneacetic acid) or picloram (4-amino-3,5,6-trichloropicolinic acid; 9 µM) and cytokinin BA (benzyloadenine; 4.5 µM) applied in the early stages of somatic embryogenesis (SE) on specific stages of SE in Picea abies and P. omorika were investigated. The highest SE initiation frequency was obtained after 2,4-D application in P. omorika (22.00%) and picloram application in P. abies (10.48%). NAA treatment significantly promoted embryogenic tissue (ET) proliferation in P. abies, while 2,4-D treatment reduced it. This reduction was related to the oxidative stress level, which was lower with the presence of NAA in the proliferation medium and higher with the presence of 2,4-D. The reduced oxidative stress level after NAA treatment suggests that hydrogen peroxide (H2O2) acts as a signalling molecule and promotes ET proliferation. NAA and picloram in the proliferation medium decreased the further production and maturation of P. omorika somatic embryos compared with that under 2,4-D. The quality of the germinated P. abies embryos and their development into plantlets depended on the auxin type and were the highest in NAA-originated embryos. These results show that different auxin types can generate different physiological responses in plant materials during SE in both spruce species.

Herbicide biomonitoring in agricultural workers in Valle del Mayo, Sonora Mexico.

Valle del Mayo is an important agricultural area at the northwest of Mexico where up to 20,000 L of a mix composed of glyphosate and tordon is used in drains and canals. This study was carried out in order to evaluate the cellular damage caused by glyphosate, aminomethylphosphonic acid (AMPA), and picloram in agricultural workers. Biomonitoring was performed through the quantification of herbicides in urine using HPLC (high-performance liquid chromatography) to then evaluate the cellular damage in exposed people by means of an evaluation of micronuclei and cellular proliferation in lymphocyte cultures. The urine samples (n = 30) have shown a concentration of up to 10.25 µg/L of picloram and 2.23 µg/L of AMPA; no positive samples for glyphosate were reported. The calculation of the external dose reveals that agricultural workers ingest up to 146 mg/kg/day; however, this concentration does not surpass the limits that are allowed internationally. As for the results for the micronuclei test, 53% of the workers showed cellular damage, and the nuclear division index test reported that there was a significant difference (P < 0.05) between the exposed and the control population, which indicated that the exposure time to pesticides in the people of Valle del Mayo can induce alterations which can cause chronic damage.

Arabidopsis PIC30 encodes a major facilitator superfamily transporter responsible for the uptake of picolinate herbicides.

Picloram is an auxinic herbicide that is widely used for controlling broad leaf weeds. However, its mechanism of transport into plants is poorly understood. In a genetic screen for picloram resistance, we identified three Arabidopsis mutant alleles of PIC30 (PICLORAM RESISTANT30) that are specifically resistant to picolinates, but not to other auxins. PIC30 is a previously uncharacterized gene that encodes a major facilitator superfamily (MFS) transporter. Similar to most members of MFS, PIC30 contains 12 putative transmembrane domains, and PIC30-GFP fusion protein selectively localizes to the plasma membrane. In planta transport assays demonstrate that PIC30 specifically transports picloram, but not indole-3-acetic acid (IAA). Functional analysis of Xenopus laevis oocytes injected with PIC30 cRNA demonstrated PIC30 mediated transport of picloram and several anions, including nitrate and chloride. Consistent with these roles of PIC30, three allelic pic30 mutants are selectively insensitive to picolinate herbicides, while pic30-3 is also defective in chlorate (analogue of nitrate) transport and also shows reduced uptake of 15NO3- . Overexpression of PIC30 fully complements both picloram and chlorate insensitive phenotypes of pic30-3. Despite the continued use of picloram as an herbicide, a transporter for picloram was not known until now. This work provides insight into the mechanisms of plant resistance to picolinate herbicides and also shed light on the possible endogenous function of PIC30 protein.

Toxicological evaluation of the herbicide Palace® in Drosophila melanogaster.

Drosophila melanogaster is a suitable model for toxicological studies of environmental pollutants including pesticides, which are known to produce adverse effects on the ecosystem. The aim of the present study was to investigate the adverse influence of the pesticide Palace®, a mixture of 2,4-dichlorophenoxyacetic acid (2,4-D) and picloram, using D. melanogaster as a model organism. D. melanogaster larvae were exposed to 0.011%, 0.022%, 0.112%, 0.224%, and 1.12% of Palace® and development examined. Adult flies were treated with 0.224%, 1.12%, 2.24%, 11.2%, and 22.4% of Palace® and the following analyzed survival, locomotor behavior, acetylcholinesterase (AchE) activity, reactive oxygen species (ROS) production, total and non-protein thiol levels, and mitochondrial function. Data demonstrated that exposure of flies during larval stage to Palace® significantly affected development of larvae to the adult stage. In adults, treatment with Palace® resulted in dose-dependent progressive adverse effects on survival and behavior with males more sensitive than females. In both males and females, ROS production and AchE activity were not markedly affected by Palace®. However, total thiol levels increased in female heads treated with highest dilution of Palace®, while decreased levels of non-protein thiols were detected in heads of male flies following Palace® exposure. In females and males flies exposed to Palace® reduced mitochondrial oxygen consumption related to oxidative phosphorylation (OXPHOS) state, mitochondrial capacity of excess (E-P) and respiratory control ratio (RCR) was noted, indicating that the pesticide mixture altered mitochondrial complexes functionality with consequences on bioenergetics. In summary, Palace® exposure produced adverse effects on D. melanogaster affecting survival, development, behavior and mitochondrial function, which may exert ecotoxicological consequences which poses risks to different organisms in the ecosystem.

The pesticide picloram affects biomembrane models made with Langmuir monolayers.

Cell membrane models are useful to obtain molecular-level information on the interaction of biologically-relevant molecules such as pesticides whose activity is believed to depend on its effects on the membrane. In this study, we investigated the interaction between the widely used pesticide picloram with Langmuir monolayers of binary and ternary mixtures comprising 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), sphingomyelin (SM) and cholesterol (Chol), which could be taken as representative of ocular membranes in humans. Picloram expanded the molecular area of DOPC/SM and DOPC/SM/Chol monolayers as the pesticide penetrated the hydrophobic region of the mixtures. A clear correlation was also found between the compressibility modulus (Cs-1) and the presence of cholesterol in the ternary monolayer. Data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) confirmed that picloram interacts with both the acyl chains and headgroups. Spectral shifts and band broadening were induced by picloram, particularly for the phosphate and choline groups, probably owing to its H-bonding ability. The effects reported here on the lipid monolayers may be evidence of the possible activity of picloram on mammalian cell membranes, which highlights the importance of strict control of the level of exposure of humans dealing with pesticides.

Kinetics of the metabolic effects, distribution spaces and lipid-bilayer affinities of the organo-chlorinated herbicides 2,4-D and picloram in the liver.

Tordon® is the commercial name of a mixture of two organo-chlorinated herbicides, 2,4-D and picloram. Both compounds affect energy transduction in isolated mitochondria and the present study aimed at characterizing the actions of these two compounds on liver metabolism and their cellular distribution in the isolated perfused rat liver. 2,4-D, but not picloram, increased glycolysis in the range from 10 to 400 µM. The redox potential of the cytosolic NAD+-NADH couple was also increased by 2,4-D. Both compounds inhibited lactate gluconeogenesis. Inhibitions by 2,4-D and picloram were incomplete, reaching maximally 46% and 23%, respectively. Both compounds diminished the cellular ATP levels. No synergism between the actions of 2,4-D and picloram was detected. Biotransformations of 2,4-D and picloram were slow, but their distributions occurred at high rates and were concentrative. Molecular dynamics simulations revealed that 2,4-D presented low affinity for the hydrophobic lipid bilayers, the opposite occurring with picloram. Inhibition of energy metabolism is possibly a relevant component of the toxicity of 2,4-D and of the commercial product Tordon®. Furthermore, the interactions of 2,4-D with the membrane lipid bilayer can be highly destructive and might equally be related to its cellular toxicity at high concentrations.