Imazapyr Research Articles

Microwave-assisted synthesis of copper oxide particles and its application for determination of imazapyr in environmental samples

Imazapyr (IMA) is currently applied as pre- and post-emergence herbicide for control of weeds in crops. Because of its extensive use, IMA residues may reach water sources and soils. Consequently, its accurate measurement is demanded for timely actions with minimal involved steps and analysis time. Herein, copper oxide particles (Cu2O PS) were proposed as chemical sensor for determination of IMA residues. Cu2O PS were prepared by a facile microwave-assisted method using glucose as reducing agent and polyvinylpyrrolidone as stabilizer. The effect of main experimental parameters on the conversion rate of the Cu2O PS were analyzed by the response surface methodology. Obtained particles were thoroughly characterized in order to determine the particle size distribution, morphology, surface charge, optical and surface properties for further application. Determination of IMA was only based on the localized surface plasmon resonance band of Cu2O PS at 473 nm. Under optimal conditions, the method was evaluated in the concentration range between 80.0 and 1,000 μg L−1 showing a limit of detection about 101 μg L−1 (R2 >0.98). The applicability of the proposed methodology to determine IMA in soil and water samples was assessed with satisfactory recoveries (104–121.8%) displaying a good implementation prospect in environmental complex matrices.

Generation of Transfer-DNA-Free Base-Edited Citrus Plants.

To recover transgenic citrus plants in the most efficient manner, the use of selection marker genes is essential. In this work, it was shown that the mutated forms of the acetolactate synthase (ALS) gene in combination with the herbicide selection agent imazapyr (IMZ) added to the selection medium may be used to achieve this goal. This approach enables the development of cisgenic regenerants, namely, plants without the incorporation of those bacterial genes currently employed for transgenic selection, and additionally it allows the generation of edited, non-transgenic plants with altered endogenous ALS genes leading to IMZ resistance. In this work, the citrus mutants, in which ALS has been converted into IMZ-resistant forms using a base editor system, were recovered after cocultivation of the explants with Agrobacterium tumefaciens carrying a cytidine deaminase fused to nSpCas9 in the T-DNA and selecting regenerants in the culture medium supplemented with IMZ. Analysis of transgene-free plants indicated that the transient expression of the T-DNA genes was sufficient to induce ALS mutations and thus generate IMZ-resistant shoots at 11.7% frequency. To our knowledge, this is the first report of T-DNA-free edited citrus plants. Although further optimization is required to increase edition efficiency, this methodology will allow generating new citrus varieties with improved organoleptic/agronomic features without the need to use foreign genes.

Development of selective preconcentration/clean-up method for imidazolinone herbicides determination in natural water and rice samples by HPLC-PAD using an imazethapyr imprinted poly(vinylimidazole-TRIM)

The development of a novel molecularly imprinted solid-phase extraction (MISPE) method for simultaneous preconcentration of imazapyr (IMP), imazapic (IMZ) and imazethapyr (IMT) with determination by HPLC-PAD (High performance liquid chromatography – photodiode-array detector) is proposed. The polymer synthesis was performed using imazethapyr as template molecule and 1-vinylimidazole as functional monomer. The method is based on preconcentration of 100.0 mL of sample through 200.0 mg of molecularly imprinted poly(vinylimidazole-TRIM) (MIP-1VN) at pH 4.0, followed by elution with 2.0 mL of MeOH:CH2Cl2:HAc (34:62:4, v/v). The range of analytical curve (0.29–200.0, 0.21–200.0 and 0.15–200.0 µg L−1), limits of detection (0.09, 0.06 and 0.04 µg L−1) and preconcentration factors (92, 96 and 98) determined for the herbicides, IMP, IMZ and IMT, respectively, were greatly superior when compared with those ones obtained with commercial adsorbents. The analytical method was successfully applied to spiked surface water and rice samples with good results of recovery values (86–107%).

Evidence of accelerated and altered pollen development after Imazapyr treatment in resistant sunflower

ABSTRACT Imazapyr (IM) treatment applied at early reproductive developmental stages have been associated with induced male sterility in sunflower (Helianthus annuus L.). The aim of this work was to determine the effects induced by two different doses of IM-treatment (1X and 2X; 80 and 160 g a.i.·ha-1) on pollen grain yield, pollen viability and on the exine surface, in an intermediate resistant (I) and a completely resistant (R) genotype. An anatomical analysis of some stages during the microsporogenesis and microgametogenesis was also achieved by confocal microscopy. Plants of both genotypes survived the herbicide treatments and showed no external injury symptoms. Differential response to different doses of IM was obtained in R and I genotypes. The pollen grains per flower and the viability in seeds were significantly reduced in the I genotype by the 2X treatment; however, the pollen viability of the remaining grains was not altered, and the diameter of the pollen grains was increased by the herbicide treatment. Anatomical and cytological observations of the sporogenous tissue development were made via confocal microscopy. IM treatment induced alterations in sporogenous cells during the initial phases of microsporogenesis in both genotypes, and the 2X dose accelerated the microgametogenesis process, particularly in the I genotype. These findings improved the understanding of the mechanism underlying the gametocide effects of the imidazolinones in sunflower.

Partial Male Sterility in Imisun Sunflower: Imazapyr Treatment in Advanced Vegetative Stages Decreases Pollen Yield and Alters ahas Gene Expression

Imidazolinones are powerful herbicides that inhibit branched‐chain amino acid biosynthesis by targeting the catalytic subunit of acetohydroxyacid synthase (AHAS). Imidazolinone application in the advanced vegetative or early reproductive developmental stages is associated with male sterility in resistant sunflower (Helianthus annuus L.); however, the underlying mechanism of this sterility remains unknown. This study describes the morphological, cytoembryological, and molecular alterations induced by imazapyr (IM) treatment on reproductive tissues at different developmental stages in two sunflower genotypes, resistant and intermediate resistant, respectively. Pollen and seed physiological variables were compared between the treated and control plants. The number of pollen grains per flower and viable seeds were negatively affected by IM treatment in the intermediate‐resistant genotype, and the biometric traits of early developed disc flower were also significantly different in this genotype. Differential interference contrast microscopy revealed that IM treatment slightly accelerates megagamethophyte development. Anther observations at microsporogenesis using confocal microscopy show that the sporogenous tissue was damaged. Furthermore, the expression profiles of the sunflower AHAS paralogs (ahas1, ahas2, and ahas3) were measured by quantitative polymerase chain reaction in the anthers and pistils of two developmental stages in treated and control plants. Imazapyr treatment in early reproductive growth stages clearly induces divergent expression patterns in the ahas gene family. These findings provide new insight into a novel chemical method for inducing male sterility in sunflowers and enhance our understanding of the effects of AHAS‐inhibitor herbicides in reproductive tissues.

Experimental and molecular modeling investigations of inclusion complexes of imazapyr with 2-hydroxypropyl(β/γ) cyclodextrin

The inclusion complexes of imazapyr (IMA) with 2-hydroxypropyl(β/γ) cyclodextrins (HP β/γ-CD), have been studied in aqueous media and in the solid state. In this work, fluorescence spectroscopy, electrospray-ionization mass spectrometry (ESI-MS), and 1HNMR were used to investigate and characterize the inclusion complexes of IMA with the cyclodextrins in solutions. The solid state complexes were obtained by freeze drying and were characterized by Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (PXRD). The most predominant complexes of IMA with both hosts are the 1:1 guest: host complexes. The association constants of IMA-HP β-CD and IMA-HP γ-CD were 115 ± 23 and 215 ± 80 L mol−1, respectively. Molecular dynamic (MD) simulations were used to monitor the mode of inclusion and also to investigate the stability of these complexes in aqueous media at atomistic levels. The results obtained have indicated that these inclusion complexes are highly stable in aqueous media, thereby corroborating the experimental results. Additionally, it has been demonstrated that in addition to hydrophobic effects and van der Waals interactions the presence of hydrogen bonding interactions of the type HO and CHO between the guest and the host have enhanced the stability of these complexes remarkably.

The binding interaction of imazapyr with cucurbit[n]uril (n = 6–8): Combined experimental and molecular modeling study

The inclusion complexes of imazapyr (IMA) with cucurbit[n]uril, CB[n] (n=6–8), have been investigated. Fluorescence spectroscopy, MALDI-TOF, and 1HNMR were used to investigate and characterize the inclusion complexation of IMA and CB[n] in solutions. Whereas the solid state complexes have been characterized by Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (PXRD). IMA was found to form 1:1 complexes with CB[n] with association constants ranging from 5.80×102–2.65×103. The guest molecule IMA was found to encapsulate into the larger cavities of CB[7] and CB[8], whereas with CB[6] the molecule remains outside the cavity. Molecular dynamic (MD) simulations were used to follow the inclusion process at an atomistic level to study the mechanism and stability of inclusion. The results obtained showed that inclusion complexes of IMA with both CB[7] and CB[8] are highly stable in aqueous media, but the CB[6] smaller cavity size prohibited the formation of an inclusion complex with IMA. The results clearly show that in addition to hydrophobic effects the presence of hydrogen bonding has added greatly to the stability of these complexes.

The influence of humic acids extracted from Chaouia soil on the behavior of transition metal ions and pesticides

Humic acid (HA) and fulvic acid (FA) exist ubiquitously in environments and have a variety of functional groups, which allow them to complex with metal ions and pesticides. Furthermore, these interactions can not only alter the environmental behavior, but also influence the removal and transportation of those pollutants. The study of the interaction between Cu (II), VO (II) and Mn (II) with HAs provides environmental information on the oxidation states of paramagnetic metals and their mechanisms of binding to humic acids. Electron spin resonance (ESR) study demonstrates that VO (II) and Cu (II) ions are bound with oxygen ligands to HAs, while the Mn (II) complex occurs as [Mn(H 2 O) 6 ] 2+ . Additionally, Cu (II) ions are more strongly bound than Mn (II) ions to soil HAs. The effect of the presence of HA on photolysis of Tribenuron-methyl (TRB) and Imazapyr (IMAZ) herbicides in water was studied by irradiation of different mixtures of HA/herbicide (0.5:1 and 1:1 by volume). The obtained results clearly demonstrate that HA substances exhibit a screening effect on the photochemical degradation of the two herbicides. The protective effect of HAs on the TRB and IMAZ degradation could be explained with an inclusion and/or adsorption of the herbicide molecules in the humic matrix.

Imazapyr+imazapic herbicide determines acute toxicity in silver catfish Rhamdia quelen

Imazapyr (IMY) and imazapic (IMI) are imidazolinone herbicides which have been associated in a commercial formulation (Kifix®). To date, there are no studies on the toxicity of an IMY+IMI herbicide in fish. This work aimed to assess the acute toxicity (24 and 96h) of IMY+IMI (0, 0.488 and 4.88µg/L) towards Rhamdia quelen through hematological, biochemical, immunological, ionoregulatory and enzymatic indexes. Red blood cell count was lower at 4.88 than at 0.488µg/L (24 and 96h); mean corpuscular volume was lower than control at both concentrations (24h) and at 0.488µg/L (96h); lymphocytes declined at 4.88µg/L comparing to control (96h); and monocytes increased at 4.88µg/L (96h) in comparison with the respective control and with 4.88µg/L at 24h. Aspartate aminotransferase was higher at 0.488µg/L (96h) than the respective control and the respective concentration at 24h; uric acid reduced at 4.88µg/L comparing with 0.488µg/L (96h); and cortisol was lower at 4.88µg/L compared to 0.488µg/L and control (96h). Herbicide exposure lowered plasma bactericidal activity at both concentrations (24h) and at 0.488µg/L (96h); and plasma complement activity declined at 4.88µg/L comparing with 0.488µg/L and control (96h), and was lower at all concentrations at 96h than at 24h. Plasma K+ levels were higher at 4.88µg/L than in the remaining groups (24 and 96h); and Na+ levels decreased at 4.88µg/L compared to control (96h). Na+/K+-ATPase and H+-ATPase activities in gills were lower at 4.88µg/L comparing with control (24h) and with the respective concentration at 96h; and AChE activity in brain was higher at 0.488 and 4.88µg/L than control (24h) and the respective concentrations at 96h, while in muscle it was higher at 0.488 and 4.88µg/L than control (96h) and the respective concentrations at 24h. The present findings demonstrate that, despite IMY+IMI targets the animal-absent AHAS enzyme, such formulation displayed an acute toxic effect upon R. quelen homeostasis by impacting on vital functions such as immune defense, metabolism, ionoregulation and neurotransmission.

Adsorption and transport of imazapyr through intact soil columns taken from two soils under two tillage systems

The objective of this work was to study the sorption and transport of imazapyr (IMZ) in two soils with different physical–chemical properties, subject to long-term conventional tillage (CT) and no-tillage (NT) systems. Sorption was carried out using batch equilibrium method and high performance liquid chromatography analytical routines. Displacement experiments through intact soil cores were done using IMZ as reactive solute and bromide (Br-) as non-reactive solute. Equilibrium (CDEeq) and non-equilibrium (CDEnon-eq) transport models (CXTFIT 2.1) were employed to describe the breakthrough curves (BTCs). IMZ was only sorbed by NT soils with Kd values ranging from 0.22 to 1.1Lkg−1. Clay content, pH and CEC values were the main factors affecting the sorption of IMZ. Miscible displacement studies showed that almost all the soil water was mobile and transport was related to physical equilibrium conditions. Some evidence of sorption non-equilibrium was seen in column experiments with IMZ; retardation factors were close to one, demonstrating the low sorption and the high potential to leach of this compound.

Chemical control of invasive Psidium guajava in Swaziland: A preliminary assessment of costs and efficacy

Psidium guajava (guava) is recognised as the third most important inva­sive alien plant species in the moist savanna biome of South Africa, Lesotho and Swaziland. The cost of initial clearing of alien plants reaches up to R3 000-00 per ha, therefore the application of correct control methods is essential for cost-effective reduction of the spread. The aim of this study was to test the cost effectiveness of applying various herbicides to guava in the Swaziland Sour Bushveld. Four plots were selected for standing plant treatments, five for cut stump treatments and two for controls. Within each of these plots, five sub-plots were randomly located and the number of plant stems, base diameter, maximum height, and crown diameter was recorded before application of the herbicides. Picloram, fluroxypyr, bromacil, tebuthiuron and imazapyr were used either alone or in combinations. Eleven months after herbicide application, the treated plants were measured again. Bromacil/tebuthiuron liquid soil application gave the best results in terms of cost (0.09 c/stem) for standing plant treatments. The picloram/fluroxypyr cut stump treatment (4.5% concentration) cost the least to apply (0.05 c/stem), and no resprouting was observed. Results from this study can be used as baseline figures for managers planning to control guava. Key words: Alien plant control, herbicides, picloram, fluroxypyr, bromacil, tebuthiuron, imzapyr.

Chemical control of field horsetail (<i>Equisetum arvense</i>)

Field horsetail is a perennial rhizomatous weed with summergrowing fernlike foliage and sporelating stems It likes moist freedraining sandy soils and gravel riverbeds and flood plains Glasshouse experiments on 10month old potted field horsetail plants showed excellent efficacy of imazapyr amitrole metsulfuron picloram and combinations of picloram with metsulfuron or triclopyr all at highest recommended rates However in the field trial single applications of these herbicides did not provide effective longterm control with significant regrowth 2 months after treatment This suggests that most of the herbicide treatments did not damage the extensive root system sufficiently to stop considerable regrowth with herbicides such as triclopyrpicloram glyphosate and metsulfuron failing to give adequate control of this weed in the field Further applications of amitrole or triclopyrmetsulfuron 2 months after the initial treatment gave better results but also killed all other vegetation

Characterizing and Designing Polycation−Clay Nanocomposites As a Basis for Imazapyr Controlled Release Formulations

A novel controlled release formulation (CRF) of the herbicide imazapyr (IMP) was designed to reduce its leaching,which causes soil and water contamination. The anionic herbicide IMP was bound to polydiallyldimethylammonium-chloride (PDADMAC)-montmorillonite composites. PDADMAC adsorption reached a high loading of polymer, which resulted in charge reversal of the clay and promoted IMP binding. The composites were characterized by Fourier transform infrared, zeta potential, and X-ray diffraction measurements, indicating electrostatic interactions of the polycation with the surface, polycation intercalation in the clay and suggesting a configuration as loops and tails on the surface at high loadings. IMP binding to the composites is affected by polycation loading and flocculation. Upon adding high concentrations of IMP to a composite of 0.16 g/g, we obtained high herbicide loadings (66% active ingredient). IMP release from the CRFs applied on a thin layer of soil was substantially slower than its release from the commercial formulation (Arsenal). Accordingly, soil column bioassays indicated reduced herbicide leaching (nearly 2-fold) upon applying the CRFs while maintaining good herbicidal activity. The new PDADMAC-clay formulations are promising from the environmental and weed control management points of view.

Comparative genotoxicity evaluation of imidazolinone herbicides in somatic cells of Drosophila melanogaster

In the present study, five analogous herbicides, namely Imazapyr (IMZR), Imazapic (IMZC), Imazethapyr (IMZT), Imazamox (IMZX) and Imazaquin (IMZQ), were evaluated for genotoxicity (mutagenic and recombinagenic activity) in the wing somatic mutation and recombination test (SMART) of Drosophila melanogaster. They are classified as imidazolinone (IMI) herbicides and their mode of action is to inhibit acetohydroxyacid synthase (AHAS), an enzyme involved in the biosynthesis of the amino acids leucine, isoleucine and valine. Two crosses were used: the standard (ST) cross and the high bioactivation (HB) cross. The latter is characterized by high levels of cytochrome P450 conferring increased sensitivity to promutagens and procarcinogens. Three-day-old larvae were exposed by chronic feeding (48 h) to four different concentrations of these herbicides (2.5, 5.0, 10.0 or 20.0 mM). For the evaluation of genotoxic effects, the frequencies of spots per individual in the treated series were compared to the concurrent negative control series (ultrapure water). Imazapyr, Imazapic and Imazethapyr gave negative results with both crosses of the wing spot test. In the ST cross, Imazamox showed positive results only for large single spots (20.0 mM IMZX) and weak positive results for total spots (10.0 and 20.0 mM IMZX), while Imazaquin showed positive results only for large single spots (5.0 and 20.0 mM IMZQ) and a weak positive result for total spots (20.0 mM IMZQ). These positive results are mainly due to induced recombination and to a minor extent to mutations. In the HB cross, only Imazamox (5.0 mM IMZX) showed a weak positive result for small single spots. The positive control urethane, a promutagen, caused an increase in the number of all types of spots in both crosses. In conclusion, the results of chronic treatments performed at high doses (toxicity was observed at higher doses) shows the existence of a genotoxic risk for IMZX and IMZQ exposure under these experimental conditions, and indicate the need for further research to delineate the exact mechanisms involved.

Adsorption of imidazolinone herbicides on smectite-humic acid and smectite-ferrihydrite associations.

Adsorption of imazapyr (IMZ), imazethapyr (IMZT), and imazaquin (IMZQ) was studied on two smectite-humic acid and two smectite-ferrihydrite binary systems prepared by treating a Wyoming smectite with a humic acid extracted from soil (4 and 8% w/w of the smectite) and with just-precipitated synthetic ferrihydrite (8 and 16% w/w of the smectite). Adsorption of the three herbicides on the smectite was not measurable at pH >4.5, presumably because of negative charges on the surface of the smectite. Adsorption on the smectite-humic acid systems was also not measurable, presumably because of negative charges on the surface, despite the high affinity of the three herbicides for humic acid, the adsorption order of which was IMZ < IMZT << IMZQ. Adsorption decreased in the order IMZ < IMZT < IMZQ on the smectite-ferrihydrite systems and IMZQ < IMZT < IMZ on ferrihydrite, although here the differences were small. These results show that even though pure smectite cannot adsorb herbicides, it modifies the adsorption capacity of ferrihydrite. The mutual interaction of active phases such as humic acid, ferrihydrite, and smectite alters the characteristics of the resulting surface and hence the adsorption process. Investigations of herbicide adsorption have been seen to produce more reliable results if conducted on polyphasic systems rather than on single soil components.

Photostability and photostabilizing effect of humic acids

The photolysis of Humic Acids (HA) extracted from Moroccan soil in water under simulated sunlight method has been studied. The photochemical degradation of HA in concentration (30 mg/L) has been followed by TOC (Total Organic Carbon) and E4/E6 ratio (The E4/E6 value widely used to characterize humic acids is the ratio of absorption intensities at 465 and 665 nm). HA were found photostable after 24 h of irradiation exposure and produce a screen effect on photochemical degradation of TRB (Tribenuron‐methyl) and IMAZ (Imazapyr) herbicides.

Summary of Toxicity Studies on Imazapyr

イマザピルはアメリンカン・サイアナミッド社が開発した多年生及び一年生雑草を対象とする非農耕地用の非選択性除草剤である. またそのユニークな作用特性により1%液剤は多年生雑草を対象とした抑草剤として開発に成功した. イマザピルは各種毒性試験の結果, きわめて安全性の高い薬剤であることが示された. 急性毒性は非常に弱く普通物に相当した. 変異原性, 催奇形性は認められず, 顕著な薬理作用も認められなかった. 眼に対する刺激性, 皮膚に対する弱い刺激性はみられたが, 皮膚感作性は陰性であった. ラットを用いた亜急性毒性試験では, 高用量群 (10,000ppm) の雄ラットで一時的に体重増加抑制, 食餌効率の低下がみられたのみで非常に毒性が低かった. 以上より, イマザピルは, その使用方法, 使用上の注意事項を厳守すればきわめて安全性の高い薬剤であると考えられる.

Relationships among the herbicide and functional sites of acetohydroxy acid synthase from Chlorella emersonii

The properties of acetohydroxy acid synthase (AHAS, EC 4.1.3.18) from wild-type Chlorella emersonii (var. Emersonii, CCAP-211/11n) and two spontaneous sulfometuron methyl (SMM)-resistant mutants were examined. The AHAS from both mutants was resistant to SMM and cross-resistant to imazapyr (IM) and the triazolopyrimidine sulfonanilide herbicide XRD-498 (TP). The more-SMM-resistant mutant had AHAS with altered catalytic parameters (Km, specificity), but unchanged sensitivity to the feedback inhibitors valine and leucine. The second mutant enzyme was less sensitive to the feedback inhibitors, but had otherwise unchanged kinetic parameters. Inhibition-competition experiments indicated that the three herbicides (SMM, IM, TP) bind in a mutually exclusive manner, but that valine can bind simultaneously with SMM or TP. The three herbicide classes apparently bind to closely overlapping sites. We suggest that the results with C. emersonii and other organisms can all be explained if there are separate binding sites for herbicides, feedback inhibitors and substrates.