Chlorinated phenoxyacetic acids and chlorophenols in the modified Allium test

The chlorinated phenoxyacetic acids 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4,5-T butoxyethyl ester and the chlorophenols 2,4-dichlorophenol and 2,4,5-trichlorophenol were tested for genotoxicity in the modified Allium test, which is based on exposure to the test chemicals of growing onions. The mean length of growing roots were measured and chromosome damage was recorded. Of the substances tested, MCPA was the most toxic and the chlorophenoxyacetic acids were more toxic than the chlorophenols. The lower threshold values for growth retardation were below 0.1 ppm for the acids, approx. at 0.1 ppm for the ester and less than 5 ppm for the phenols. Though a monocotyledon, Allium cepa was sensitive enough to respond to even low concentrations of these dicotyledon-selecting pesticides.     

Physiological and cellular responses of the 2,4-D degrading bacterium,Burkholderia cepacia YK-2, to the phenoxyherbicides 2,4-D and 2,4,5-T

Our previous research has demonstrated that novel 43-kDa DnaK and 41-kDa GroEL proteins are synthesized in Burkholderia sp. YK-2 in response to sublethal concentrations of 2,4-D stress [Cho et al. (2000) Curr Microbiol 41:33-38]. In this study, we have extended this work to examine the cellular responses of strain YK-2 to stresses induced in response to the phenoxyherbicides 2,4-D or 2,4,5-T. Strain YK-2 exhibited a more sensitive response to 2,4,5-T stress than to 2,4-D stress, as shown in physiological and morphological changes, suggesting a greater cytotoxic effect of 2,4,5-T. SEM analyses revealed the presence of perforations and irregular rod forms with wrinkled surfaces for cells treated with either herbicide. These irregularities were found more frequently for 2,4,5-T-treated cells than for 2,4-D-treated cells. Analysis of cellular fatty acids showed similar effects in the shifts of total cellular fatty acid composition in response to 2,4-D and 2,4,5-T. Strain YK-2 could degrade 2.25 m M 2,4-D completely during 28 h of incubation with transient production of 2,4-dichlorophenol as a metabolite; however, 2,4,5-T was not catabolized at any of the concentrations tested. BIOLOG and 16S rDNA analyses revealed that strain YK-2 was 98% similar to the Burkholderia cepacia species cluster; therefore, we have designated this strain as B. cepacia YK-2.     

Physiological and Cellular Responses of the 2,4-D Degrading Bacterium, Burkholderia cepacia YK-2, to the Phenoxyherbicides 2,4-D and 2,4,5-T

Our previous research has demonstrated that novel 43-kDa DnaK and 41-kDa GroEL proteins are synthesized in Burkholderia sp. YK-2 in response to sublethal concentrations of 2,4-D stress [Cho et al. (2000) Curr Microbiol 41:33–38]. In this study, we have extended this work to examine the cellular responses of strain YK-2 to stresses induced in response to the phenoxyherbicides 2,4-D or 2,4,5-T. Strain YK-2 exhibited a more sensitive response to 2,4,5-T stress than to 2,4-D stress, as shown in physiological and morphological changes, suggesting a greater cytotoxic effect of 2,4,5-T. SEM analyses revealed the presence of perforations and irregular rod forms with wrinkled surfaces for cells treated with either herbicide. These irregularities were found more frequently for 2,4,5-T-treated cells than for 2,4-D-treated cells. Analysis of cellular fatty acids showed similar effects in the shifts of total cellular fatty acid composition in response to 2,4-D and 2,4,5-T. Strain YK-2 could degrade 2.25 mM 2,4-D completely during 28 h of incubation with transient production of 2,4-dichlorophenol as a metabolite; however, 2,4,5-T was not catabolized at any of the concentrations tested. BIOLOG and 16S rDNA analyses revealed that strain YK-2 was 98% similar to the Burkholderia cepacia species cluster; therefore, we have designated this strain as B. cepacia YK-2. Received: 7 February 2002 / Accepted: 7 March 2002     

Influence of medium composition on callus induction and camptothecin(s) accumulation in Nothapodytes foetida

Camptothecin(s) production was examined in callus cultures derived from cotyledons of Nothapodytes foetida (Weigh) Sleumer. The calluses were grown on various combinations of Murashige and Skoog's basal media supplemented with auxins 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), a-napthalene acetic acid (NAA) and indole-3-acetic acid (IAA) with 6-benzyl aminopurine (BA)/kinetin in different concentrations. The presence of camptothecin (CPT) and 9-methoxycamptothecin (9-OMeCPT) were analyzed by HPLC in relation to the media composition. Hyper production of CPT(1.306% on dry wt. basis) was observed with a combination of 2,4-D with BA and 2,4,5-T and NAA in 1-month-old callus.     

Inhibitory Effects of Phenolic Ecotoxicants on Photobacteria at Various pH Values

Kinetic characteristics of light emission by intact cells of photobacteria Photobacterium phosphoreum and Vibrio harveyi were studied (at pH 5.5, 7.0, and 8.0), as well as inhibitory effects of 2,4-di- and 2,4,5-triphenoxyacetic acids (2,4-D and 2,4,5-T), pentachlorophenol (PCP), and 2,6-dimethylphenol (2,6-DMP) (at the same pH values). The emission kinetics lacked a steady state, irrespective of pH. At pH 5.5, luminescence decayed exponentially in the 60-s range; at pH 7.0 and 8.0, a 5-min luminescence activation was observed. The respiratory activity of the cells decreased by more than an order of magnitude at pH 5.5 (compared to the levels observed at pH 7.0 and 8.0). The inhibitory effects of 2,4-D, 2,4,5-T, and PCP differed by one to two orders of magnitude, depending on pH. Maximum cell sensitivity to these compounds appeared at pH 5.5; minimum sensitivity, at pH 8.0. The effect of 2,6-DMP was pH-independent. The inhibitory effect was determined by the hydrophobicity of the molecule and pK values of the toxicants. At all pH values, substrate-depleted cells of photobacteria were more sensitive to chlorophenolic compounds than cells supplied with energy.     

Inhibitory effects of phenolic ecotoxicants on photobacteria at various pH values

Kinetic characteristics of light emission by intact cells of the photobacteria Photobacterium phosphoreum and Vibrio harveyi at pH 5.5, 7.0, and 8.0 were studied as well as specific features of inhibitory effects of 2,4-di- and 2,4,5-triphenoxyacetic acids (2,4-D and 2,4,5-T), pentachlorophenol (PCP), and 2,6-dimethylphenol (2,6-DMP) at the same pH values. Nonstationarity of emission kinetics was observed at all the pH values studied. Exponential luminescence decay in a 60-sec range was observed at pH 5.5; a 5-min luminescence activation, at pH 7.0 and 8.0. The cell respiratory activity drops by over one order of magnitude at pH 5.5 compared with the activities at pH 7.0 and 8.0. The inhibitory effects of 2,4-D, 2,4,5-T, and PCP differ by one-two orders of magnitude depending on pH. The maximal cell sensitivity to these compounds appears at pH 5.5; the minimal, at pH 8.0. The effect of 2,6-DMP is independent of pH. As is demonstrated, it is hydrophobicity of the molecule and pK values of the toxicants that determine the inhibitory effect. Characteristic of the substrate-starved photobacterial cells are higher sensitivity to chlorophenolic compounds compared with the cells provided with high energy supply at all the pH values.     

A gold nanoparticle-mediated enzyme bioreactor for inhibitor screening by capillary electrophoresis

A facile protocol to prepare highly effective and durable in-line enzyme bioreactors inside capillary electrophoresis (CE) columns was developed. To demonstrate the methodology, l-glutamic dehydrogenase (GLDH) was selected as the model enzyme. GLDH was first immobilized onto 38-nm-diameter gold nanoparticles (GNPs), and the functionalized GNPs were then assembled on the inner wall at the inlet end of the CE capillary treated with polyethyleneimine (PEI), producing an in-line GLDH bioreactor. Compared with a GLDH bioreactor prepared by immobilizing GLDH directly on PEI-treated capillary, the GNP-mediated bioreactor showed a higher enzymatic activity and a much better stability. The in-capillary enzyme bioreactor was proven to be very useful for screening of GLDH inhibitors deploying the GLDH-catalyzed α-ketoglutaric acid reaction. The screening assay was preliminarily validated by using a known GLDH inhibitor, namely perphenazine. A Z′ factor value of 0.95 (n = 10) was obtained, indicating that the screening results were highly reliable. Screening of GLDH inhibitors present in medicinal plant extracts by the proposed method was demonstrated. The inhibition percentages were found to be 53% for Radix scutellariae, 45% for Radix codonopsis, 37% for Radix paeoniae alba, and 0% for the other 22 extracts tested at a concentration of 0.6 mg extract/ml.     

Catalase activity in human erythrocytes: effect of phenoxyherbicides and their metabolites

The effects of exposure to different concentrations of phenoxyherbicides and their metabolites were studied in human erythrocytes, with particular attention to catalase (CAT-EC. 1.11.1. 6- hydrogen peroxide: hydrogen peroxide oxidoreductase). 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4-dimethylphenol (2, 4-DMP) and 2,4-dichlorophenoxyacetic acid (2,4-D) did not affect CAT activity, but 2,4-dichlorophenol (2,4-DCP) and 2,4,5-trichlorophenol (2,4,5-TCP) decrease its activity, the latter being the more inhibitory.     

The Uptake of Growth Substances: XI. VARIATIONS IN THE ACCUMULATION OF SUBSTITUTED PHENOXYACETIC ACIDS OF DIFFERING PHYSIOLOGICAL ACTIVITY BY SEGMENTS OF AVENA MESOCOTYL

An examination has been made of the phase of continuous accumulationof phenoxyacetic acid (POA) and the 2-, 4-, 2,4-, 2,6-, and2,4,5-chloro-derivatives, containing carbon-14 in the carboxylgroup, by segments of the Avena mesocotyl. On the basis of previousfindings to eliminate the initial transient components of uptake(Type I processes) the segments were pretreated for 13 to 18h in buffer or buffer containing the respective non-radioactivecompound. For five of the compounds the relationship between the rateof uptake and the external concentration takes the form of arectangular hyperbola, but for the sixth, 2,4,5-T, this relationshipdoes not hold. The data, except those for 2,4,5-T, have beenevaluated as linear regressions of rate of uptake against thequotient of rate over concentration. From each regression equationtwo constants have been derived: the point ‘B’ wherethe line intersects the rate axis (the theoretically maximumrate) and the slope of the regression ‘K’, whichcan alternatively be expressed as the concentration at whichthe observed rate equals half the value of ‘B’. The calculated values of B and K for POA are approximately twiceas great as the corresponding values for 2-CPA, and about 25times greater than for 4-CPA. The values for 2,4-D are closeto those for 4-CPA, and 2,6-D is intermediate between 2-CPAand 4-CPA. Although the constants for 2,4,5-T could not be calculatedprecisely, the rates of accumulation are about one-fourth ofthose measured for 2,4-D at equivalent concentrations. The uptake of radioactive 2,4-D is slightly depressed in thepresence of nonradioactive POA. Greater reductions are causedby 2-CPA or 2,6-D, and 2,4-D or 2,4,5-T are even more inhibitory.The pattern of inhibition caused by 2,4,5-T indicates competitionfor common sites of uptake, while POA appears not to be competitive.In corresponding experiments with POA, the presence of the otherregulators only caused small inhibitions and the order was different. Earlier work showed that in Avena accumulation is accompaniedby the conversion to a varying degree of the individual substitutedphenoxyacetic acids to conjugated derivatives. It is suggestedthat the variation between compounds in their rates of accumulationis in part due to differences in the stability of the conjugatedderivatives, and that the facility of conversion is a factorin determining physiological activity.     

Studies on Foliar Penetration: VIII. EFFECTS OF CHLORINATION ON THE MOVEMENT OF PHENOXYACETIC AND BENZOIC ACIDS THROUGH CUTICLES ISOLATED FROM THE FRUITS OF LYCOPERSICON ESCULENTUM L.

The effects of chlorine substitution on the movement of phenoxyaceticand benzoic acids through enzymatically-isolated cuticles ofLycopersicon fruits were determined by following the transferof each acid containing ¹⁴C from a donor to a receiver solution.This cuticle is characterized by an isotropic cutin matrix,within which patches of birefringent cuticular waxes are foundnear the outer surface. The outer, morphological surface isrelatively smooth while at the junction with the outer wallsof the epidermal cells there is extensive cuticular developmentextending down between the anticlinal walls. The epicuticularwax appears as a soft sheet-like covering of which the surfaceis relatively featureless. Chlorination of phenoxyacetic acid results in an enhanced transferacross the isolated cuticle. The order was 2,4,5- and 2,4,6-trichlorophenoxyacetic> 2,4- and 3,5-dichlorophenoxyacetic > 2-chlorophenoxyacetic> phenoxyacetic acid. Removal of the epicuticular wax resultedin greater permeability for all compounds; transfer of the morepolar acids was favoured. In contrast, chlorination of benzoicacid decreases passage through the cuticle; the rate is highestfor benzoic acid followed in descending order by 2-chlorobenzoic,2,4- and 2,5-dichlorobenzoic and 2,3,6-trichlorobenzoic acid.Chlorination also depresses the passage of both phenoxyaceticand benzoic acid through a dialysis membrane. The effects ofchlorination on the lipid solubility of both series of compoundsare discussed in relation to differences in transfer acrossthe cuticle.     

Morphological transformation and catalase activity of syrian hamster embryo cells treated with hepatic peroxisome proliferators,TPA and nickel sulphate

The abilities of the hepatic peroxisome proliferators (HPPs) clofibrate, di(2-ethylhexyl)phthalate (DEHP), mono(2-ethylhexyl)- phthalate (MEHP), 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and tiadenol to induce morphological transformation and to increase the catalase activity of Syrian hamster embryo (SHE) cells were studied. DEHP, MEHP, clofibrate and tiadenol induced morphological transformation of SHE cells and increased the catalase activity. DEHP was more potent than clofibrate and tiadenol in both inducing catalase and morphological transformation, while MEHP seemed more potent than DEHP in inducing catalase, but not morphological transformation, 2,4,5-T and 2,4-D did not induce morphological transformation, but 2,4,5-T was more potent than clofibrate in increasing the catalase activity. These results show that several HPPs induce morphological transformation of SHE cells and an increase in the catalase activity. There is, however, no direct connection between these two parameters, as seen from the results of 2,4,5-T. The tumor promoter TPA, and the metal salt nickel sulphate, induced morphological transformation of SHE cells without any appreciable increase in the catalase activity. These results further corroborate the dissociation between induction of morphological transformation and the increase in catalase activity.Abbreviations Clofibrate ethyl-2-(p-chlorophenox) isobutyrate - 2,4-D 2,4-dichlorophenoxy acetic acid - DEHP di(2-ethylhexyl)phthalate - HPP hepatic peroxisome proliferator - MEHP mono(2-ethylhexyl)phthalate - SHE Syrian hamster embryo - 2,4,5-T 2,4,5-trichlorophenoxy acetic acid - tiadenol di(hydroxyethylthio)-1,10-decane     

Bioremediation of phenolic compounds having endocrine-disrupting activity using ozone oxidation and activated sludge treatment

The bioremediation of water system contaminated with phenolic compounds having endocrine-disrupting activity,i.e. 2,4-dichlorophenol, 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T), was investigated by using ozone oxidation and activated sludge treatment. Ozone oxidation (ozonation time: 30 min) followed by activated sludge treatment (incubation time: 5 days) was an efficient treatment method for the conversion of phenolic compounds in water into carbon dioxide and decreased the value of total organic carbon (TOC) up to about 10% of initial value. Furthermore, 2,4-D was dissolved in water containing salt,i.e. artificial seawater (ASW), and this water was used as model coastal water contaminated with phenolic compounds. The activated sludge treatment (incubation time: 5 days) could consume significantly organic acids produced from 2,4-D in the model costal water by the ozone oxidation (ozonation time: 30 min) and decrease the value of TOC up to about 35% of initial value.     

Initiation and growth of cell lines of Taxus brevifolia (Pacific yew)

Summary Conditions have been established for the induction and maintenance of callus cultures of Taxus brevifolia (Pacific yew) from bark, stem, and needle tissues. Cultures were established on a modified Gamborg's B5 medium, 1% sucrose, 0.2% casamino acids and 1 mg/L 2,4-D. There was no apparent inhibition of callus induction as a result of taxol concentration in the explant material. Cell lines derived from explants of individual trees were used to investigate growth characteristics. Although none of the cell lines contained taxol, some contained low levels of related taxanes. Variability was observed with each cell line in response to light, and auxin type and concentration. Growth index was most affected by cell line, followed by auxin type and concentration. These culturing methods may be useful for the goal of developing a highproducing cell line applicable for large-scale taxol production.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - IAA indoleacetic acid - CA casamino acids - B5CA B5 with 0.2% casamino acids - IBA indolebutryric acid; Picloram (4-amino-3,5,6-tricnloro-2-pyridinecarboxylic acid) - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid - BA 6-benzylaminopurine     

Degradation of 2,4,5-Trichlorophenoxyacetic acid by a Nocardioides simplex culture

A Nocardioides simplex strain 3E was isolated which totally dechlorinated 2,4,5-trichlorophenoxyacetic acid and was capable of its utilization as the sole source of carbon. The mechanism of 2,4,5-trichlorophenoxyacetic acid degradation by this strain was investigated. Chloroaromatic metabolites that occur in the lag, exponential and stationary growth phases of the strain Nocardioides simplex 3E were isolated and identified bases on a combination of TLC, GC-MS and HPLC data. Decomposition of 2,4,5-trichlorophenoxyacetic acid at the initial stage was shown to proceed by two pathways: via the splitting of the two-carbon fragment to yield 2,4,5-trichlorophenol and the reductive dechlorination to produce 2,4-dichlorophenoxyacetic acid. Hydrolytic dechlorination of 2,4,5-trichlorophenoxyacetic acid was found to yield dichlorohydroxyphenoxyacetic acid, thus pointing to the possible existence of a third branch at the initial stage of degradation of the xenobiotic. 2,4,5-Trichlorophenol and 2,4-dichlorophenoxyacetic acid produced during the metabolism of 2,4,5-trichlorophenoxyacetic acid and in experiments with resting cells are utilized by the strain Nocardioides simplex 3E as growth substrates.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid - 2,4,5-TCP 2,4,5-trichlorophenol     

Hepatic and extra-hepatic glutathione-S-transferase activity in wild pigeons (Columba livia)

Glutathione-S-transferase (EC 2.5.1.18) activity was assayed in hepatic and extra-hepatic tissues of pigeons using l-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates. Gluthathione-S-transferase activity towards 1-chloro-2,4-dinitrobenzene in pigeon was in the order: kidney > liver > testes > brain > lung> heart. The enzyme activity with 1-chloro-2,4-dinitrobenzene as substrate was 40–44 times higher in pigeon liver and kidney than that observed with 1,2-dichloro-4-dinitrobenzene as substrate.K _m values of hepatic and renal glutathione transferase with l-chloro-2,4-dinitrobenzene as substrate were 2.5 and 3 mM respectively. Double reciprocal plots with varying reduced gluthathione concentrations resulted in biphasic curves with twoK _m values (liver 0.31 mM and 4mM; kidney 0.36 mM and 1.3 mM). The enzyme activity was inhibited by oxidized gluthathione in a dose-dependent pattern. 3-Methylcholanthrene elicited about 50% induction of hepatic glutathione transferase activity whereas phénobarbital was ineffective.     

Biodegradation of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid by dichlorophenol-adapted microorganisms from freshwater,anaerobic sediments

Reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was investigated in anaerobic sediments by non-adapted microorganisms and by microorganisms adapted to either 2,4- or 3,4-dichlorophenol (DCP). The rate of dechlorination of 2,4-D was increased by adaptation of sediment microorganisms to 2,4-DCP while dechlorination by sediment microorganisms adapted to 3,4-DCP displayed a lag phase similar to non-adapted sediment slurries. Both 2,4- and 3,4-DCP-adapted microorganisms produced 4-chlorophenoxyacetic acid by ortho-chlorine removal. Lag phases prior to dechlorination of the initial addition of 2,4,5-T by DCP-adapted sediment microorganisms were comparable to those from non-adapted sediment slurries. However, the rates of dechlorination increased upon subsequent additions of 2,4,5-T. Biodegradation of 2,4,5-T by sediment microorganisms adapted to 2,4- and/ or 3,4-DCP produced 2,5-D as the initial intermediate followed by 3-chlorophenol and phenol indicating a para > ortho > meta order of dechlorination. Dechlorination of 2,4,5-T, by either adapted or non-adapted sediment microorganisms, progressed without detection of 2,4,5-trichlorophenol as an intermediate.     

Comparative study on cerebrovascular injuries by three chlorophenoxyacetic acids (2,4-D, 2,4,5-T and MCPA)

At toxic doses in rats, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) caused injuries in blood vessels in the brain. 2. 2,4-D caused extravasations of the circulating Evans blue-albumin complex also in the spinal cord. 3. By contrast, potency in damaging cerebral vessels was almost non-existent with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). 4. None of the three chlorophenoxyacetic acids caused such cerebrovascular injuries in mice, guinea pigs, Syrian hamsters, rabbits and chickens.     

Natural selection for 2,4,5-trichlorophenoxyacetic acid mineralizing bacteria in agent orange contaminated soil

Agent Orange contaminated soils were utilized in direct enrichment culture studies to isolate 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4-dichlorophenoxyacetic acid (2,4-D) mineralizing bacteria. Two bacterial cultures able to grow at the expense of 2,4,5-T and/or 2,4-D were isolated. The 2,4,5-T degrading culture was a mixed culture containing two bacteria, Burkholderia species strain JR7B2 and Burkholderia species strain JR7B3. JR7B3 was able to metabolize 2,4,5-T as the sole source of carbon and energy, and demonstrated the ability to affect metabolism of 2,4-D to a lesser degree. Strain JR7B3 was able to mineralize 2,4,5-T in pure culture and utilized 2,4,5-T in the presence of 0.01 yeast extract. Subsequent characterization of the 2,4-D degrading culture showed that one bacterium, Burkholderiaspecies strain JRB1, was able to utilize 2,4-D as a sole carbon and energy source in pure culture. Polymerase chain reaction (PCR) experiments utilizing known genetic sequences from other 2,4-D and 2,4,5-T degrading bacteria demonstrated that these organisms contain gene sequences similar to tfdA, B, C, E, and R (Strain JRB1) and the tftA, C, and E genes (Strain JR7B3). Expression analysis confirmed that tftA, C, and E and tfdA, B, and C were transcribed during 2,4,5-T and 2,4-D dependent growth, respectively. The results indicate a strong selective pressure for 2,4,5-T utilizing strains under field condition.     

Auxin Antagonistic Effects of Auxin Precursors of the Substituted Amide Type

Cucumber seeds were germinated in Petri-dishes for 6 days withdifferent doses of a number of N-monosubstituted amide derivativesof some chlorophenoxy-alkane-carboxylic acids. Doses of theamides studied were roughly equivalent to 0.1, 1, 10, 100, and1,000 p.p.m. in water. The gross morphological effects of theamide treatments were studied, both with and without the additionof 1 and 10 p.p.m., respectively, of the corresponding carboxylicacid. The amides studied were the N-methyl-, N-ethyl-, N-propyl-,N-iso-propyl-, N-butyl-, and N-benzyl-amides of 2,4-dichlorophenoxyaceticacid (2,4-D), -(2,4-dichlorophenoxy)-propionic acid (2,4-DP),2,4,5-trichlorophenoxyacetic acid (2,4,5-T), and -(2,4,5-trichlorophenoxy)-propionicacid (2,4,s-TP). Thirteen of the twenty-one amide derivatives studied antagonizedthe auxintype plant-growth-regulating effects of their parentcarboxylic acid. The antagonisms observed involved not onlya decrease in the stimulatory effects of the externally appliedauxin acids (counteractions of the abnormal swellings of differentplant parts), but also reduced significantly their inhibitoryeffects, i.e. the inhibitions of growth in length of the hypocotyland of the roots. Since some auxin-type stimulatory effectswere observed with all of the amides studied, it is suggestedthat the thirteen amide derivatives play a double role as plantgrowth regulators in cucumber tissues: (1) to a certain extentthey are transformed by plant enzymes to the corresponding carboxylicacid, i.e. to auxin; and (2) the amides themselves exert anti-auxineffects.     

Plant regeneration from shoot apex explants of foxtail millet

Green and etiolated shoot apices of foxtail millet (Setaria italica L.) cv. Nese 2A were cultured on Murashige and Skoog medium with four concentrations of 2,4-dichlorophenoxyacetic acid or 2,4,5-trichlorophenoxyacetic acid. In all treatments, embryogenic calli capable of plant regeneration were induced after ten weeks in culture. Calli induced on 2 mg l^-1 of 2,4-d from green apices gave a higher rate of plant regeneration in comparison with etiolated apices on the other treatments. Plant regeneration was obtained from one year-old cultures. Regenerated plants were successfully established in soil, reached maturity and produced seeds.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid - EC embryogenic calli - NE nonembryogenic calli - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid