Effect of Acid treatment of plant cuticles on sorption of selected auxins

Sorption characteristics of 2-(1-naphthyl)acetic acid (NAA), 2-(1-naphthyl)acetamide (NAAm), and 2,4-dichlorophenoxyacetic acid (2,4-D) were determined for cuticles enzymically isolated from mature tomato (Lycopersicon esculentum Mill. cv Sprinter) and pepper (Capsicum annuum L.) fruit. Sorption equilibrium for NAA and 2,4-D by tomato cuticular membranes (CM) and dewaxed cuticular membranes (DCM) was achieved within 24 hours at 25°C. The average K (partition coefficient) values for NAA in tomato CM and DCM were 166 and 204, respectively, whereas the corresponding K values for 2,4-D were 292 and 383, respectively. Sorption equilibrium for 2,4-D and NAA in pepper cuticles was not achieved after 18 and 63 days, respectively. Sorption equilibrium for NAAm in tomato and pepper CM and DCM was attained within 48 hours. Acid pretreatment (2.0 n HCl, 10 minutes) had no effect on NAA, 2,4-D, or NAAm sorption by tomato CM and DCM, or on NAAm sorption by pepper CM and DCM. Acid pretreatment of pepper CM and DCM led to slightly lower K^pH (apparent partition coefficient) values for both NAA and 2,4-D. More significantly, sorption equilibrium for NAA and 2,4-D in pepper CM and DCM was achieved within 24 hours after acid treatment.     

Synergistic Effects of Organic Contaminants and Soil Organic Matter on the Soil-Water Partitioning and Effectiveness of a Nonionic Surfactant (Triton X-100)

Napthalene- and decane-contaminated soils were treated with Triton X-100 (a nonionic surfactant) to characterize the soil-water partitioning behavior of the surfactant in soils with different organic content. Soil samples with different organic content were prepared by mixing sand-mulch mixtures at different proportions. The experimental results indicated that the amount of surfactant sorbed onto soil increased with increasing soil organic content and increasing surfactant concentration. The effective critical micelle concentration (CMC) also increased with increasing organic content in soil. The CMC of Triton X-100 in aqueous systems without soil was about 0.3 mM and the effective CMC values measured for soil-water-surfactant systems (approximately 1:19 soil/water ratio) with 25%, 50%, and 75% mulch content were 0.9, 1.0, and 1.7 mM, respectively. Sub-CMC surfactant sorption was modeled accurately with both the Freundlich and the linear isotherm. The maximum surfactant sorption onto soil varied from 66% to 82% of added surfactant in the absence of contaminant. The effective CMC values for Triton X-100 increased to some extent in the presence of contaminants, as did the maximum surfactant sorption. The maximum surfactant sorbed onto the soil with 75% mulch content increased from 82% for clean soils, to 95% and 96% for soils samples contaminated with naphthalene and decane, respectively.     

Dependence of ovary growth on ovule development in Cucumis sativus

Partition and sorption characteristics of the cytokinin N-(phenylmethyl)-lH-purine-6-amine (N⁶-benzyladenine, BA) in two model systems were studied at 25°C. Apparent partition coefficients (K^pH) for BA in an n -octanol:water (buffer) system were independent of BA concentration but decreased with increasing buffer concentration (ionic strength). A plot of K^pH values versus pH (2 to 12) was a bell-shaped curve. At pH 2 or 12, K^pH values were low (less than 2). As pH approached neutrality, K^pH values increased approximately 20-fold. Estimates of pK₁(3.3) and pK₂ (10.7) values for BA were obtained from these data. The accuracy of this approach to determining pK values was verified with 2-(1-naphthyl)acetic acid (NAA). Correction of K^pH values for dissociation effects on BA yielded partition coefficients (K) whose overall mean was 37. Sorption of BA by cuticles enzymatically isolated from abaxial and adaxial surfaces of mature rubber plant ( Ficus elastica Roxb. cv. decora) leaves was initially rapid, however equilibrium was not reached by 432 h. At pH 2, sorption was low (approximately 5 μmol kg−¹), whereas at pH 6 sorption increased approximately 11-fold. Sorption by abaxial cuticular membranes (CM) and dewaxed CM (DCM) was slightly higher than corresponding adaxial CM and DCM. Using natural logarithm values, K^pH data were linearly-correlated with CM (r = 0.98) and DCM (r = 0.99) sorption data.     

Assessment of Bioavailability of Soil-Sorbed Atrazine

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO₂ production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine.     

Studies on octylphenoxy surfactants: X. Effect of oxyethylene chain length on ethylene production by cowpea and mung bean and comparison with linear alcohol hydrophobes

The effects of ethoxy (EO) chain length on surfactant-induced ethylene production for selected octylphenoxy (OP) and linear alcohol (LA) surfactants were established using primary leaves of cowpea (Vigna unguiculata (L.) Walp. subsp. unguiculata Dixielee) seedlings. OP surfactant-induced ethylene production was concentration dependent and decreased log linearly with increasing EO content. C_12–15 LA-induced ethylene production decreased log linearly with increasing EO content at 0.1%; however, at 1.0% the relationship was curvilinear with maximum response at 7 EO. Relationships for the C_9–11 and C₉ LA series were nonlinear with greatest biological activity at intermediate (8–12) EO content. Short EO chain length OP surfactants were only slightly water soluble, and induced low levels of ethylene production and phytotoxicity. Addition of OP+1EO to a long chain, water soluble, non-ethylene inducing surfactant (OP+40EO) solution significantly increased ethylene production by OP+1EO in cowpea. A similar response was found for surfactant-induced phytotoxicity and EO chain length as between ethylene production and EO content. Similar EO chain length and ethylene production relationships were found for germinating mung bean (Vigna radiata (L.) R. Wilcz) seeds as for ethylene production and phytotoxicity in cowpea. Radicle growth was markedly inhibited by OP surfactants with an EO chain length of 10 or less and, in some cases, radicles were irreversibly damaged by ethylene inducing surfactants.     

Assessment of bioavailability of soil-sorbed atrazine

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO(2) production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine.     

Concurrent sorption of Ni2+ and Cu2+ by Chlorella vulgaris from a binary metal solution

Kinetics and capacity of Ni2+ and Cu2+ sorption by Chlorella vulgaris were studied using single and binary metal solutions at various concentrations of these metal ions. The second-order rate law best described the kinetics of metal sorption from both single and binary metal systems. C. vulgaris preferentially sorbed Cu2+ over Ni2+ in the binary system. In comparison to the single metal system, the amounts of Ni2+ and Cu2+ sorbed at equilibrium (qe) were respectively 73% and 25%, and the initial rate of sorption (h) was ca. 50% in the case of the binary metal system. The test metals inhibited sorption of each other, thereby indicating competition between Ni2+ and Cu2+ for sorption onto non-specific binding sites. The present study showed that C. vulgaris has specific as well as non-specific sites for the binding of Ni2+ and Cu2+. Participation of these sites for sorption depended on the ratio of Ni2+ and CU2+ in solution. The maximum metal sorption capacity of C. vulgaris was 6.75 mmol g(-1) from the binary metal solution at the tested biomass concentration (100 mg dry weight l(-1)). Total metal sorption was enhanced with increasing total concentration of both the metals up to 1.6 mM, beyond which a decrease occurred. Two-dimensional contour plots were successfully used for the first time for the evaluation of metal sorption potential.     

Influence of surfactants on the sorption of two chloroacetanilide in an Romanian chernozem soil

Pesticides have been extensively used in modern agriculture. Due to the prevalent use, there have been serious problems generated by pesticides wastes which could eventually endanger water resources and human health. The development of technologies for the decontamination of soils and waters polluted by hydrophobic organic compounds has encouraged research into the use of non-ionic surfactants as potential agents for the enhanced solubilization and removal of contaminants from soils and sediments. Sorption of two chloroacetanilide herbicides, acetochlor and metolachlor was studied on a representative chernozem soil of the Main Agricultural Research Station Ezareni belonging to the "Ion Ionescu de la Brad" University of Agriculture and Veterinary Medicine lasi, Romania, in the presence and absence of surfactants. Three different non-ionic surfactants were selected: Tween-20, Synperonic 91/5 and Silwet L-77, to verify the influence of their presence on herbicide sorption at different concentrations. Our results showed that the sorption of the studied herbicides within the soil-water-non-ionic surfactant system was influenced by the presence of non-ionic surfactants. The n values obtained were lower than 1 for all pesticide-surfactant combinations, which indicates that the amount of acetochor and metolachlor sorbed decreased with an increase in pesticide concentration. The sorption of acetochlor increased in the following order: Acetochlor+Synperonic 91/5 < Acetochlor < Acetochlor+Tween-20 < Acetochlor+Silwet L-77. In the case of metolachlor+Synperonic and metolachlor+Silwet L-77, the Kf values were significantly higher than the Kf value of metolachlor+Tween-20 on soil, where a lower Kf value could be observed with however a higher n value which indicate a higher sorption capacity at higher concentrations.     

Biosorption of uranium by magnetically modified Rhodotorula glutinis

Adsorption of uranium from aqueous solution onto the magnetically modified yeast cell, Rhodotorula glutinis, was investigated in a batch system. Factors influencing sorption such as initial solution pH, biomass dosage, contact time, temperature, initial uranium concentration and other common cations were analyzed. Sorption isotherm, kinetic and thermodynamic studies of uranium on magnetically modified R. glutinis were also carried out. The temperature dependent equilibrium data agreed well with the Langmuir model. Kinetic data obtained at different temperatures were simulated using pseudo-first-order and pseudo-second-order kinetic models, the pseudo-second-order kinetic model was found to describe the data better with correlation coefficients near 1.0. The thermodynamic parameters, ΔH°, ΔS° and ΔG° were calculated from the sorption data gained at different temperatures. These thermodynamic parameters showed that the sorption process was endothermic and spontaneous. All results indicated that magnetically modified R. glutinis can be a potential sorbent for uranium wastewater treatment.     

Interaction of bovine serum albumin and long-chain imidazolium ionic liquid measured by fluorescence spectra and surface tension

The binding of long-chain imidazolium ionic liquid (IL), 1-tetradecyl-3-methylimidazolium bromide (C₁₄mimBr) to bovine serum albumin (BSA) was investigated by fluorescence spectra and surface tension. Fluorescence spectra show that tryptophan (Trp) residues, one of the intrinsic fluorophores in BSA, are buried in a hydrophobic microenvironment with the addition of C₁₄mimBr, which induces the denaturation of BSA. Moreover, the fluorescence quenching mechanism was determined to be static quenching. The equilibrium constant (K) and the number of binding sites (n) were calculated based on the results of fluorescence measurement. The critical aggregation concentration (CAC) and critical micelle concentration (CMC) under different BSA concentrations at various temperatures were investigated based on the surface tension plots. Surface tension indicates that C₁₄mimBr binds to BSA through electrostatic attraction at low C₁₄mimBr concentrations (below CMC) and through hydrophobic interaction at high C₁₄mimBr concentrations (above CMC). Additionally, the thermodynamic parameters of micelle formation were determined. This study provides an understanding of the binding of C₁₄mimBr to BSA.     

Mutualistic interaction between dichloromethane‐ and chloromethane‐degrading bacteria in an anaerobic mixed culture

The microbial mixed culture RM grows with dichloromethane (DCM) as the sole energy source generating acetate, methane, chloride and biomass as products. Chloromethane (CM) was not an intermediate during DCM utilization consistent with the observation that CM could not replace DCM as a growth substrate. Interestingly, cultures that received DCM and CM together degraded both compounds concomitantly. Transient hydrogen (H₂) formation reaching a maximum concentration of 205 ± 13 ppmv was observed in cultures growing with DCM, and the addition of exogenous H₂ at concentrations exceeding 3000 ppmv impeded DCM degradation. In contrast, CM degradation in culture RM had a strict requirement for H₂. Following five consecutive transfers on CM and H₂, Acetobacterium 16S rRNA gene sequences dominated the culture and the DCM‐degrader Candidatus Dichloromethanomonas elyunquensis was eliminated, consistent with the observation that the culture lost the ability to degrade DCM. These findings demonstrate that culture RM harbours different populations responsible for anaerobic DCM and CM metabolism, and further imply that the DCM and CM degradation pathways are mechanistically distinct. H₂ generated during DCM degradation is consumed by the hydrogenotrophic CM degrader, or may fuel other hydrogenotrophic processes, including organohalide respiration, methanogenesis and H₂/CO₂ reductive acetogenesis.     

Bio-separation, speciation and determination of chromium in water using partially pyrolyzed olive pomace sorbent

Speciation of Cr(III)/Cr(VI) from water using olive pomace (OP) was improved by partial pyrolysis of OP. The sorbents were characterized by physicochemical techniques. Sorption of Cr(III) on raw and partially pyrolyzed OP sorbents followed Freundlich isotherm and second-order rate kinetics. OP pyrolyzed at 150 °C (sorbent OP-150) exhibited maximum sorption capacity, favorability and the lowest sorption energy. Sorption was exothermic and spontaneous for the raw-OP and OP pyrolyzed at 100 or 150 °C; but endothermic and non-spontaneous for OP pyrolyzed at 200, 250, 300 or 400 °C. A speciation method of chromium was proposed, in which Cr(III) was selectively retained at pH 3 on sorbent OP-150; while total Cr was determined after reduction of Cr(VI). The method was selective with a detection limit for Cr(III) of 1.58 μg L⁻¹. The method was applied on natural and industrial waters (recoveries >97.7%, RSD’s <9%) and on tobacco leaves certified reference material (INCT-PVTL-6).     

Sorption and Release of Organics by Primary,Anaerobic, and Aerobic Activated Sludge Mixed with Raw Municipal Wastewater

New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1^st order kinetics. Sorption of particulates also followed 1^st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC) per g volatile suspend solids (VSS) for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215–230 nm were also rapidly removed.     

Liposomes as a model for the study of the mechanism of fish toxicity of sodium dodecyl sulfate in sea water.

The mechanism underlying the shark repellency of SDS was studied by comparing it with the shark nonrepelling detergent, Triton X-100. The findings can be summarized as follows: (1) The effective concentration of SDS for termination of shark tonic immobility (an immediate and fast response) was close to its critical micellar concentration in sea water (70 microM). The fish lethal concentrations (LD50) were far below the CMC value for SDS, and at CMC level for Triton X-100. (2) In sea water SDS possesses a strong affinity for lipid membranes, expressed in a lipid sea water partition coefficient (Kp) of about 3000. (3) In liposomal systems examined by assays of turbidity, fluorescence resonance energy transfer and kinetics of carboxyfluorescein (CF) release, the pattern of SDS induced changes in the phospholipid bilayer suggests: (a) absence of vesicle-vesicle fusion; (b) occurrence of vesicle size increase, and (c) nonlytic gradual release of CF above and below its CMC values. In contrast, Triton X-100 above its CMC induces membrane solubilization. (4) Assays coupling CF release from liposomes to potassium diffusion potential induced by valinomycin indicate that SDS related CF release can also be attributed to a specific mechanism such as cation pore formation and not only to membrane solubilization. The hypothesis of pore formation by SDS is discussed.     

Removal of chromium (VI) using poly(methylacrylate) functionalized guar gum

Using persulfate/ascorbic acid redox pair, poly(methylacrylate) was grafted on to guar gum and the conditions for the grafting were optimized. The copolymer sample having maximum %G was evaluated for the removal of Cr(VI) and the sorption conditions were optimized. The sorption was found pH dependent, pH 1.0 being the optimum value. Sorption data at pH 1.0 were modeled using both the Langmuir and Freundlich isotherms where the data fitted better to Freundlich isotherm. The equilibrium sorption capacity of 29.67 mg/g was determined from the Langmuir isotherm. The sorption followed a pseudo-second-order kinetics with a rate constant 2.5 × 10^?4 g mg^?1 min^?1. The grafted product was also evaluated for Cr(VI) removal from local electroplating industrial waste water. The regeneration experiments revealed that the guar-graft-poly(methylacrylate) could be successfully reused for five cycles. In the present study conductivity measurements were used instead of conventional photometric method for determining Cr(VI) concentration in the equilibrium solutions and the results obtained have been compared with photometric method. Optimum Cr(VI) binding under highly acidic conditions indicated significant contribution of non electrostatic forces in the adsorption process.     

Bacterial decolorization of acid orange 7 in the presence of ionic and non-ionic surfactants

The effects of the non-ionic surfactant Triton X-100, the cationic surfactant cetyltri-methylammonium bromide (CTAB) and the anionic surfactant sodium N-lauroyl sarcosinate (SLS) on the decolorization of the reaction medium containing the monoazo dye Acid Orange 7 (AO7) by Alcaligenes faecalis and Rhodococcus erythropolis were studied. It was found that the surfactants influenced in different ways the rate of decolorization. At all concentrations tested the non-ionic surfactant Triton X-100 decreased the decolorization rate of R. erythropolis. At concentrations above the critical micelle concentration (CMC) Triton X-100 upset the usually observed exponential decay of the dye with A. faecalis due probably to the existence of an outer membrane in this organism. In concentrations above the CMC the anionic surfactant SLS inhibited the decolorization and, at prolonged incubation, caused partial release of the bound dye. The cationic surfactant CTAB in concentrations above and below the CMC accelerated drastically the binding of AO7 to the cells causing a rapid staining of the biomass and complete decolorization of the reaction medium. An attempt was made for explanation of the observed differences by the negative electrostatic charge of the living bacterial cell.     

Sorption of Heavy Metals to the Filamentous Bacterium Thiothrix Strain A1

A study was undertaken to determine the ability of the filamentous bacterium Thiothrix strain A1 to sorb heavy metals from solution. Cells of Thiothrix strain A1 were harvested, washed, and suspended in solutions of metals. After an equilibration period, biomass was separated from solution and the metal content in acid-digested cells and/or filtrates was determined by atomic absorption spectrophotometry. Sorption of nickel and zinc was very rapid; most of the sorbed metal was bound in less than 10 min. The sorption data for copper fit the Freundlich isotherm, and nickel and zinc data fit biphasic Freundlich isotherms. Sorption of both nickel and zinc was dependent on cell age. Cells harvested 24 h after inoculation sorbed approximately one-half of the amount of metal per gram cell protein than did cells harvested after 48, 72, or 96 h. Calcium and magnesium effectively competed with zinc for binding sites, whereas potassium had only a slight effect on the capacity of cells to sorb zinc. The primary mechanism of metal sorption apparently was ion exchange, because 66 to 75% of nickel or zinc could be desorbed by placing metal-laden cells in a solution of 5 mM CaCl₂. A competition experiment with nickel and zinc indicated that both metals occupied the same sorption sites. The strong chelating agents EDTA and NTA effectively prevented metal uptake, but lactate enhanced the uptake of nickel. Thiothrix strain A1 grown in nickel-containing medium had a relatively low uptake of nickel compared with uptake by resting cells suspended in a simple buffer solution.     

Determination of surfactant critical micelle concentration by a novel fluorescence depolarization technique

A novel method using fluorescence depolarization to determine the critical micelle concentrations (CMC) of surfactants was developed. Fluorescence anisotropies of Triton X-100, sodium dodecyl sulfate, and sodium cholate were measured using 1,6-diphenyl-1,3,5-hexatriene as a fluorescence probe. Fluorescence anisotropy decreased with increasing surfactant concentrations below the CMC and leveled off above the CMC. The depolarization method does not depend on the concentration of DPH and is largely immune to light-scattering problems encountered in turbid aqueous systems.     

On the effect of lysophosphatidylcholine, platelet activating factor and other surfactants on calcium permeability in sarcoplasmic reticulum vesicles.

The effect of low concentrations of lysophosphatidylcholine (LPC), platelet-activating factor (PAF) and other surfactants (Triton X-100, C12E8, sodium dodecyl sulfate, sodium cholate and sodium deoxycholate) on membrane permeability of native sarcoplasmic reticulum vesicles and sarcoplasmic reticulum lipid vesicles, has been studied. Triton X-100, C12E8, sodium dodecyl sulfate, sodium cholate and sodium deoxycholate were all able to permeabilize membranes at concentrations of surfactants below their critical micellar concentration (CMC) in both lipid and native vesicles, being the K0.5 of calcium release from native vesicles lower than that from lipid vesicles. The values of these K0.5 were well correlated with the corresponding CMC values for each type of membrane. However, both LPC and PAF behaved in a different way since, although they induced permeabilization of the native vesicles at values of K0.5 close to their CMC, their K0.5 values for permeabilizing vesicles, prepared by using lipids extracted from sarcoplasmic reticulum, were much higher than their corresponding CMC.     

Lavandula angustifolia essential oil as a novel and promising natural candidate for tick (Rhipicephalus (Boophilus) annulatus) control

Lavandula angustifolia is a well known herbal medicine with a variety of useful properties, including its acaricidal effect. This experiment was carried out to study the bioacaricidal activity of L. angustifolia essential oil (EO) against engorged Rhipicephalus (Boophilus) annulatus (Acari; Ixodidae) females. For this purpose six serial concentrations (0.5, 1.0, 2.0, 4.0, 6.0 and 8.0% w/v) of L. angustifolia EO were used. There was considerable mortality in concentrations more than 4.0% although there were no differences between 6.0 and 8.0% in all measured criteria. The mortality rate 24 h after inoculation was 73.26 and 100% in groups treated with 4.0 and 8.0% EO, respectively. Lavender EO also reduced tick egg weight in a concentration-dependent manner. The amount of eggs produced varied from 0.12 g (at 0.5% EO) to 0.00 g (at 8.0% EO) but did not differ statistically from the control. L. angustifolia EO caused 100% failure in egg laying at 6.0 and 8.0% whereas this value in the control group was zero. A positive correlation between L. angustifolia EO concentration and tick control, assessed by relative mortality rate and egg-laying weight, was observed by the EO LC/EC₅₀, which, when calculated using the Probit test, was 2.76-fold higher than the control. Lavender is a promising acaricidal against R. (B.) annulatusin vitro.