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1.
The rapid effects of the thiocarbamate herbicide S-ethyl dipropyl thiocarbamate (EPTC) and the herbicide protectant N,N-diallyl-2,2-dichloroacetamide (DDCA) on macromolecular syntheses and glutathione (GSH) levels in maize cell cultures were studied to determine whether stimulation of GSH could be the primary mechanism of action of DDCA. EPTC (0.5 and 1 mM) reduced incorporation of radioactive precursors within 1 hr after treatment, and affected incorporation of [3H]acetate into lipids more than incorporation of [3H]adenosine into acid-precipitable nucleic acids, or [14C]protein hydrolysate into protein. [14C]EPTC was rapidly biotransformed within 8 hr by maize cell suspensions. Measureable decreases in GSH levels following treatment with 1 mM EPTC occurred after 15 hr. DDCA stimulated incorporation of [3H]acetate into lipids within 4 hr but did not affect incorporation of [14C]protein hydrolysate into protein or [3H]adenosine incorporation into nucleic acids. Measureable increases in GSH following DDCA treatment began after 12 hr. Treatment with EPTC and DDCA in combination inhibited incorporation of [3H]acetate into lipids less than EPTC given alone. Increases in GSH levels could be observed following pretreatments with glutathione precursors, but no protectant activity could be detected, in contrast to treatments with DDCA. It is suggested that DDCA has an initial rapid effect on lipid metabolism followed by a slower effect involving increases in cellular GSH.  相似文献   

2.
The rapid effects of the herbicide EPTC (S-ethyl dipropylthiocarbamate) and the protectant DDCA (N,N-diallyl-2,2-dichloroacetamide) on [2-14C]acetate incorporation into lipids of maize cell cultures were studied in order to determine whether they act at similar sites of lipid synthesis. DDCA, at 0.05 mM and 0.1 mM, increased the incorporation of [2-14C]acetate into neutral lipids of a total lipid extract within 2 h. It had very little effect on the major polar lipid constituents. DDCA altered neither the distribution of label within the major lipid classes, nor turnover of the major lipids within 2 h. EPTC (0.1 mM) inhibited overall uptake of [2-14C]acetate into both neutral and polar lipids by about 30% after a 2-h incubation. The major polar lipid affected was an unidentified glycolipid. In addition to reducing the quantity of lipids synthesized, EPTC changed the lipid profile, altering the distribution of label, mainly within the neutral lipid fraction. A crude membrane fraction from maize cells contained both polar lipids and some neutral lipids. DDCA stimulated [2-14C]acetate incorporation into different lipid species. EPTC inhibited incorporation of [2-14C]acetate into both neutral and polar membrane lipids but altered significantly only its distribution into neutral lipids. DDCA (0.1 mM) given together with EPTC (0.2 mM) partially counteracted the effect of EPTC within the neutral lipid fraction. It is suggested that DDCA has a rapid effect on lipid synthesis, but it is probably not sufficient to account for the entire mode of action of the protectant.  相似文献   

3.
The efficacies of nine structural analogues of the herbicide antidote naphthalene-1,8-dicarboxylic acid anhydride (naphthalic anhydride, NA) for the protection of maize (Zea mays L. cv. DeKalb XL72AA and DeKalb XL67) against injury by the herbicide S-ethyl dipropyl(thiocarbamate) (EPTC) were elevated under greenhouse conditions. The chemical analogues of NA tested were: acenaphthenequinone (ACQ); 4-aminonaphthalene-1,8-dicarboxylic acid anhydride (NH2NA); 1,8:4,5-naphthalenetetracarboxylic acid dianhydride (NDiA); naphthalene- 1,8-carboximide (NHNA); 4-chloronaphthalene-1,8-dicarboxylic acid anhydride (C1NA); biphenyl-2,2′-dicarboxylic acid anhydride (diphenic anhydride; DA); 2-phenylglutaric anhydride (PGA); phthalic anhydride (PHA); phenalen-1-one (PA). Pre-plant incorporated applications of EPTC at 2.2, 4.5, 6.7, and 9.0 kg ha?1 were highly toxic to XL67 maize. Appreciable injury to XL72AA maize by EPTC was observed only with the high rates of EPTC (6.7 and 9.0 kg ha?1). Of the analogues tested PGA and PA were very toxic and inhibited germination of both maize hybrids. NA, ACQ, NH2NA, NDiA, NHNA, C1NA, DA, and PHA applied as seed dressings at 5.0 and 10 g per kg of seed offered satisfactory protection to XL72AA maize against EPTC rates higher than 6.7 kg ha?1. The same antidotes significantly antagonised the EPTC activity against XL67 maize but the overall protection obtained was partial and not agronomically important. The presence of the dicarboxylic anhydride group and of at least one aromatic ring attached directly to the anhydride appeared to be essential for the exhibition of protective activity by the structural analogues of NA. NA was slightly toxic to both hybrids of maize and chlorination of NA increased the phytotoxicity of this molecule. A genetic component that is present in the thiocarbamate-tolerant XL72AA hybrid but absent from the thiocarbamate-susceptible XL67 hybrid of maize appeared to be important for the phytotoxic activity of EPTC and may be involved in the protective activity of NA and its structural analogues.  相似文献   

4.
Abstract

Treating maize seed and cowpea seed with activated carbon or naphthalic anhydride permitted highly selective and economic early control of grasses and some broadleaved weeds with respectively EPTC and linuron and EPTC and chloramben. Without protectant every herbicide treatment produced less crop yield than with protectant. Early season control of grasses with herbicides followed by one row-cultivation controlled weeds throughout the crop.  相似文献   

5.
The herbicide safener N-dichloroacetyl-1-oxa-4-aza-spiro-4,5-decane (AD-67) is of similar efficiency as the extensively used N.N-diallyl-2,2-dichloroacetamide (R-25788) and the structurally related 3-(dichloroacetyl)-2,2-dimethyl-1,3-oxa-zolidine (AD-2) in reducing EPTC [S-ethyl-N,N-dipropyl (thiocarhamate)] injury to maize (Zea mays L. cv. KSC 360). EPTC treatment produces growth retardation and deformities and inhibits CO2 fixation. It does not reduce epicuticular lipids appreciably but affects wax arrangement on the leaf surface. When EPTC is applied together with one of these safeners, these injuries are not observed. All three safeners act similarly. Each prevents the herbicide-induced aggregation of epicuticular wax of maize, thereby protecting the plants against the formation of areas where the underlying cuticle layers are exposed and increase in transpiration.  相似文献   

6.
Glutathione (GSH) content and GSH S-transferase activity are consistently increased in corn roots on 24-hr exposure of corn seedlings to part per million levels of N,N-diallyl-2,2-dichloroacetamide (R-25788) and related antidotes for thiocarbamate herbicide injury in susceptible corn varieties. This combined enhancement of enzyme activity and cofactor level leads to rapid detoxification of thiocarbamate sulfoxides, which are proposed to be the active herbicidal compounds formed on metabolic sulfoxidation. S-(N,N-Dipropylcarbamyl)-GSH is formed by this enzyme-catalyzed detoxification of EPTC sulfoxide. This hypothesis on antidote mode of action is supported by studies on 32 dichloroacetamides and related compounds and on the concentration- and time-dependent relationships of R-25788 action. The liver GSH content is normal in mice injected with high doses of R-25788, but the content is reduced when EPTC or EPTC sulfoxide is administered. EPTC sulfoxide also carbamoylates the thiol group of coenzyme A in neutral aqueous medium.  相似文献   

7.
Corn (Zea mays L. single cross hybrid Mv 620) was germinated in a petri dish with addition of carbonyl[14C]EPTC (S-ethyl-N,N-dipropylthiocarbamate). The shoots and roots of 4-day-old seedlings were crushed and extracted in 80% methanol. On the chromatogram of the extract three radioactive peaks were found. The main peak was identified as S-(N,N-dipropylcarbamoyl)-glutathione. For the comparison of carbamoylating ability [14C]EPTC, [14C]EPTC-sulfoxide, and [14C]EPTC-sulfone were incubated with glutathione. Only EPTC-sulfone reacted in the 10-day incubation time. In aquatic solutions EPTC and EPTC-sulfoxide proved to be stable during the 10 days compared to EPTC-sulfone which quickly degraded, S-(N,N-Dipropylcarbamoyl)-glutathione was converted to S-(N,N-dipropylcarbamoyl)-cysteine in corn shoot homogenate. [14C]EPTC, [14C]EPTC-sulfoxide and [14C]EPTC-sulfone were added to corn shoot homogeneates and each of the three mixtures were analyzed by chromatography after 1 day incubation. EPTC was partly oxidized to EPTC-sulfoxide. EPTC-sulfoxide did not change and EPTC-sulfone produced similar metabolites as had been found in the germination experiment.  相似文献   

8.
The history of herbicide antidotes is reviewed, beginning with the exploration of compounds to protect wheat (Triticum aestivum L.) against barban in the early 1960s, and the later introduction of naphthalic anhydride (NA, naphthalene-1, 8-dicarboxy-licanhydride) as a seed dressing for protecting maize (Zea mays L.) against EPTC. This compound was largely replaced by Stauffer's R-25788 (N, N-diallyl-2, 2-dichloroacetamide) which has continued to be widely used in conjunction with EPTC and butylate in maize. This compound is highly specific to maize and can thus be applied in admixture with the herbicide, but has not proved of practical value on other crop species. NA on the other hand is less specific and is of potential value on sorghum [Sorghum bicolor (L.) Moench] and rice (Oryza sativa L.); experimental work continues on these crops. The only other antidote to be marketed so far is cyometrinil as a seed dressing for protecting sorghum against metolachlor and related herbicides. Other compounds are under development. Mode of action and structure-activity relations are discussed, as well as the current and future potential for antidotes in respect of the control of weed species in closely related crops, the increased options for herbicide use in minor crops and the possibility of reduced costs for broad spectrum weed control in major crops.  相似文献   

9.
E. EBERT 《Weed Research》1982,22(6):305-311
The grass weed herbicide metolachlor (2-chloro-N-[2-ethyl-6-methylphenyl]-N-[2-methoxy-1-methylethyl]acetamide) which is especially effective against wild millets, inhibits the formation of epicuticular waxes on sorghum leaves. The metolachlor protectant CGA 43089 [α - (cyanomethoximino) - benzacetonitrile] prevents the depletion of the waxes on the leaves of metolachlor-treated sorghum plants, as demonstrated by scanning electron microscopy. This alteration of the plant surface polymers also changes their permeability to the herbicide. 14C-metolachlor uptake into isolated coleoptiles and first leaves of sorghum which had been pretreated with the herbicide was increased. Incubation with added protectant reduced the uptake of 14C-metolachlor. It is postulated that the modifications caused by metolachlor and its protectant to sorghum surface structures influence the action of the herbicide in two ways:
  • 1 The selectivity observed against sorghum and millet grasses could occur because of an increased uptake of metolachlor through cuticles which are particularly sensitive to the structural changes caused by the herbicide, since the composition of the plant waxes is very species-specific.
  • 2 The loss of cuticular integrity is prevented by the protectant CGA 43089, which greatly reduces penetration of metolachlor.
  相似文献   

10.
Vernolate (0, 8, 16, 31, 62, 125.0, or 250.0 ppbw) incorporated into sand inhibited the growth of wheat (Triticum aestivum L. cv Holley) at 125.0 ppbw. These growth inhibition and morphological responses were virtually identical to wheat response to EPTC at 125 ppbw. 14C from vernolate (carbonyl labeled) (125.0 ppbw) was absorbed into wheat seedlings at approximately 1.8 μM on the presumption that the 14C present was [14C]vernolate. Since the response of wheat to the thiocarbamate herbicides resembles a gibberellic acid (GA) deficiency and cell enlargement requires the presence of functional plasmalemmas and tonoplasts, the question of membrane disruption by excessive concentrations of thiocarbamate herbicides and potential reversal thereof by GA3 was studied by measuring the efflux of K+, Na+, and Mg2+. GA3 (0.003 μM) stimulated lettuce leaf disc growth in diameter and fresh weight. This GA-stimulated increase in size and weight was reversed by 1 mM EPTC. Betacyanin efflux from beet leaf tonoplasts was increased by 1 mM EPTC and this efflux was not reversed by exogenous GA3 (0.3 μM). This influence by supraoptimal EPTC concentrations was shown to be via membrane disruption, which obviated any possible GA influence by eliminating the functionality of the membranes requisite to the development of a GA response. It is concluded that viable mode-of-action studies must measure physiological responses consistent with the symptomology of herbicide responses normally observed with each herbicide at field concentrations.  相似文献   

11.
R-25788 (2,2-Dichloro-N,N-diallylacetamide) was the most effective of six potential antidotes evaluated to counter corn (Zea mays L.) injury from the acetanilide herbicides alachlor, metolachlor, acetochlor, H-22234 (N-chloroacetyl-N-(2,6-diethylphenyl)glycine ethyl ester), and H-26910 (N-chloroacetyl-N-(2-methyl-6-cthylphenyl)glycine isopropyl ester). The other potential antidotes in order of decreasing effectiveness were: R-29148 (2,2-dimethyl-5-methyl-dichloroacetyloxazolidine), NA (1,8-naphthalic anhydride), CDAA (2-chloro-N,N-diallylacetamide), Carboxin (2,3-dihydro-5-carboxanilido-6-methyl-l,4-oxathiin), and gibberellin (GA3). GA3 only partly relieved the stunting of corn caused by EPTC and metolachlor and did not prevent other herbicide injury symptoms, suggesting that the mode of action of EPTC and metolachlor is not to simply block GA3 synthesis. R-25788 protected corn equally well from acetanilide or EPTC injury. Produits protecteurs du maïs (Zea mays) contre les dommages provoqués par les acétanilides herbicides Le R-25788 (2,2-dichloro-N.N-diallylacétamide) s'est révéléêtre le plus efficace de six produits protecteurs essayés pour préserver le maïs (Zeas mays L.) des dégâts provoqués par des acétanilides herbicides: alachlore, métolachlore, acétochlore, H-22234 (ester éthylique de la N-chloracétyl-N-(2,6-diéthylphényl) glycine) et H-26910 (ester isopropylique de la N-chloroacétyl-N-(2-méthyl-6-éthylphényl) glycine. Les autres produits protecteurs potentiels ont été, dans l'ordre d'efficacité décroissante: le R-29148 (2,2-diméthyl-5-méthyl-dichloroacéthyloxazolidine), l'AN (anhydride 1.8-naphtalique), le CDAA (2-chloro-N-N-diallylacétamide), la carboxyne (2,3-dihydro-5-carboxanilido-6-méthyl-l,4-oxathiine) et la gibbérelline (A3 G). Cette dernière a seulement atténué le rabou-grissement provoqué par l.EPTC et le métolachlore chez le maïs. Elle n'a pas supprimé les symptômes de dommages provoqués par les autres herbicides, ce qui suggère que le mode d'action de I'EPTC et du métolachlore ne consiste pas seulement en un blocage de la synthèse de la gibbérelline. Le R-25788 a protégé le maïs des dommages provoqués par l'acétanilide ainsi que par I'EPTC. Potentielle Antidots zur Vermeidung von Acetanilid-Herbizid-schäden an Mais (Zea mays) Von sechs potentiellen Antidots, die geprüft wurden, um Schäden an Mais (Zea mays L.) durch Acetanilid-Herbizide zu vermeiden, war R-25788 (2,2-Dichlor-N,N-diallylacetamid) am wirksamsten. Die verwendeten Herbizide waren: Alachlor, Metolachlor, Acetochlor, H-22234 [N-Chloracetyl-N-(2,6- diäthylphenyl) glycin Älhylester] und H-26910 [N-Chloracelyl-N-(2-méthyl-6-äthylphenyl)glycin lsopropylester]. Die weiteren möglichen Antidots, in der Reihenfolge abnehmender Wirksamkeit, waren: R-29148 (2,2-Dimethyl-5-methyldichlorace-toxazolidin), NA (1,8-Naphthalsäureanhydrid), CDAA (2-Chlor-N,N-diallylacetamid), Carboxin (2,3-Dihydro-5-car- boxanilido-6-methyl-l,4-oxathiin) und Gibberellin (GA3). durch GA3 wurde die dureh EPTC und Metolachlor verursachte Stauchung des Mais nur teilweise vermieden. Die durch andere Herbizide verusachten Symptome liessen sich durch GA3 nicht vermeiden, was darauf schliessen lässt, dass die Wirkungsweise von EPTC und Metolachlor nicht einfach mit einer Blockierung der GA3 -Synthese zu erklären ist. R-25788 schützte Mais gleichermassen vor Acetanilid-, wie vor EPTC-Schäden.  相似文献   

12.
The metabolism of the wild oat herbicide, flamprop-isopropyl, [Barnon, isopropyl (±) N-benzoyl-N-(3-chloro-4-fluorophenyl)-2-aminopropionate] in barley grown to maturity has been examined under glass-house and outdoor conditions. [14C]Flamprop-isopropyl labeled separately in two positions was used. The major metabolic route of the herbicide was by hydrolysis to the corresponding carboxylic acid, II, which occurred in free and conjugated forms. Flamprop-isopropyl also underwent hydroxylation in the 3 and 4 positions of the benzoyl group, and the 3-hydroxybenzoyl analogue of II was detected. The hydroxylated metabolites were also present in the plants as conjugates. Additional minor metabolites detected only in glass-house samples were N-benzoyl-3-chloro-4-fluoroaniline, 2-[3-chloro-4-fluorophenylamino]-propionic acid, and benzoic acid. The soil in which the plants were grown received part of the spray application of the herbicide. Residues in the 0–10-cm layer at barley harvest comprised the unchanged herbicide, the carboxylic acid II, and unidentified polar material.  相似文献   

13.
S-ethyl dipropylthiocarbamate (EPTC) inhibited gibberellic acid (GA) precursor biosynthesis in a cell-free enzyme preparation from unruptured, etiolated sorghum (Sorghum bicolor L. cv. G522 DR) coleoptiles. EPTC, 1 μM, inhibited incorporation of [14C]mevalonic acid into kaurene 60%, while 10 μM EPTC inhibited 14C incorporation into kaurene 90%. The precursor of kaurene cyclization (GGPP) increased in 14C content at both EPTC concentrations. R-25788 reversed the EPTC inhibition of kaurene synthesis. Kaurene oxidation was modified by both EPTC and R-25788. Hypothesized modes of action for EPTC and R-25788 are (a) inhibition of GA synthesis, (b) increased peroxidase activity resulting in increased lignification, (c) increased detoxification by sulfoxidation and carbamoylation, and (d) inhibition of fatty acid synthesis and/or desaturation. These hypotheses are discussed with three of them being incorporated into one working unit which correlates with EPTC and R-25788 symptom phenology. The fourth hypothesis could also fit into this general pattern.  相似文献   

14.
The breakdown of the herbicide benzoylprop ethyl [SUFFIX, ethyl N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropionate] has been examined in wheat, oat, and barley seedlings after application of 14C-labeled herbicide to the foliage.Within 15 days of the application the route and rate of the breakdown were similar in the plants of all three species. Some of the herbicide was present in the plants in a complexed form which could be extracted from the plant with organic solvents and converted back into the herbicide on treatment with hot acid. Evidence was obtained for hydrolysis of the herbicide in the plant to give its des-ethyl analog which conjugated with plant sugars. There was some evidence for a small degree of degradation of benzoylprop ethyl by debenzoylation to give products which also conjugated or complexed.There was no evidence for the formation of 3,4-dichloroaniline in the plants.  相似文献   

15.
A bacterial strain has been isolated from an enhanced thiocarbamate degradation soil and identified as Corynebacterium sp. The strain was capable of rapidly metabolizing EPTC in a liquid culture where the herbicide was the sole source of carbon. Evolution of high quantities of [14C]carbon dioxide was coupled with a rapid decline of [14C]EPTC in the medium; after 12 h incubation these accounted for, respectively, 60% and 0% of the recoverable radioactivity. Radioactivity in the polar extract increased gradually up to 20% after 6 h of incubation and then declined slowly. TLC analysis and identification based on comparison to reference compounds showed that the polar extract consisted of EPTC sulfoxide and two conjugates, EPTC-GSH and EPTC-cysteine (1·8%, 3·4%, and 16%, respectively). Piperonyl butoxide and tetcyclasis, but not tridiphane, were found to be effective inhibitors of EPTC metabolism in the bacterial culture, suggesting that the breakdown of EPTC might be carried out by a cytochrome P-450 monooxygenase-type activity. The thiocarbamate extender, dietholate, also strongly inhibited the metabolism of EPTC in bacterial culture. Based on these results it was postulated that the bacteria metabolize EPTC mainly by hydroxylation of the α-propyl carbon finally to release [14C]carbon dioxide, while EPTC sulfoxidation appears to be a minor route.  相似文献   

16.
The microsome-NADPH system of mouse liver oxidizes each of benthiocarb, butylate, cycloate, EPTC, molinate, pebulate, and vernolate herbicide chemicals to the corresponding thiocarbamate sulfoxide which is then cleaved by the liver soluble-glutathione system. These sulfoxides are also detected as transient metabolites in the liver of mice injected with EPTC, molinate, pebulate, and vernolate but not with the other three thiocarbamates. Thiocarbamate sulfones are not detected as metabolites of the thiocarbamates. Studies in vivo and in vitro with [14C]EPTC and -pebulate or their corresponding sulfoxides and/or sulfones further indicate that sulfoxidation is the initial metabolic step in cleavage of the thiocarbamate ester group. Sulfoxidation appears to be a detoxification mechanism for thiocarbamate herbicides in mammals.  相似文献   

17.
The purpose of this study was to examine the differential activities of proso millet (Panicum miliaceum L.) and corn (Zea mays L.) with respect to atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine] and EPTC (S-ethyldipropyl thiocarbamate) metabolism. GSH-S-transferase was isolated from proso millet shoots and roots. When assayed spectrophotometrically using CDNB (1-chloro 2,4-dinitrobenzene) as a substrate, the shoot enzyme had only 10% of the activity of corn shoot enzyme while the root enzyme had 33% the activity of corn root enzyme. However, when proso millet shoot GSH-S-transferase was assayed in vitro using 14C-ring-labeled atrazine, it degraded the atrazine to water-soluble products at the same rate as the corn shoot enzyme. Incubation of excised proso millet and corn roots with [14C]EPTC indicated that uptake of EPTC was similar in both plants. However, proso millet metabolized the EPTC to water-soluble products at only half the rate of corn. Glutathione levels of proso millet roots were 35.9 μg GSH/g fresh wt, compared with 65.4 μg GSH/g fresh wt for corn. However, a 2.5-day pretreatment with R-25788 (N,N-diallyl-2-2-dichloroacetamide) elevated proso millet GSH levels to 62.7 μg GSH/g fresh wt. R-25788 did not elevate the activity of proso millet GSH-S-transferase, in contrast to its effects on corn. We conclude that differences in response to atrazine and EPTC in proso millet and corn are a result of their differential metabolism.  相似文献   

18.
Wheat (Triticum aestivum L. cv Holley) was grown for 15 days in sand into which S-ethyl dipropylthiocarbamate (EPTC) (0, 15.6, 31.25, 62.5, or 125.0 μg/kg) had been incorporated. Growth was decreased more by EPTC under high light intensity (270 μein/m2/sec) than under low light (20 μein/m2/sec) intensity. Wheat grown in the dark did not respond to EPTC at these concentrations. In high light intensity, plastoquinone-9, plastohydroquinone-9, α-tocopheroquinone, and α-tocopherol contents (nanomoles per gram fresh weight) increased as EPTC concentration increased. Similar but less marked results occurred at the low light intensity. Plastohydroquinone-9/plastoquinone and α-tocopherol/α-tocopheroquinone ratios increased at both light intensities as EPTC concentration increased. This indicated an EPTC-induced inhibition of plastohydroquinone and α-tocopherol epoxidation. Chlorophyll a and b and total carotenoid contents increased as EPTC concentration increased in plants grown at high light intensities. Changes in the membrane electron carriers contents per unit of chlorophyll or carotenoid (micrograms per milligram of pigment) occurred. As a tentative hypothesis, it is suggested that transmembrane electron transport systems were inhibited, but growth in size (fresh weight per pot) was inhibited more than was synthesis of the various pigments and quinones. Thus, a separation of growth and metabolic response to EPTC was demonstrated.  相似文献   

19.
The action of atrazine and its biodegradation products on the membrane transport of potassium in roots was evaluated in both sensitive and resistant plants. Excised roots of maize and oat showed inhibition of potassium uptake efficiency in the presence of 1.4 × 10?4M atrazine and 1.4 × 10?4M deethylated atrazine. Other biodegradation products such as 2-chloro-4-amino-6-ethylamino-1,3,5-triazine,2-chloro-4,6-,bisamino-1,3,5-triazine, and 2-chloro-4-amino-1,3,5-triazine showed no inhibitory effect on the K+ uptake capacity. Two maize hybrids showing different uptake efficiency were inhibited differently by atrazine. We suggest that atrazine and deethylated atrazine inhibited the K+ transport interacting directly with the plant cell membranes without discerning between resistant and sensitive plants.  相似文献   

20.
In hydroponic experiments, seed-dressing with the herbicide safener 1,8-naphthalic anhydride (NA), significantly enhanced the tolerance of maize, (Zea mays L., cv. Monarque) to the imidazolinone herbicide, AC 263222, (2-[4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-5-methylnicotinic acid). Uptake, distribution and metabolism studies where [14C]AC 263222 was applied through the roots of hydroponically grown maize plants showed that NA treatment reduced the translocation of radiolabel from root to shoot tissue and accelerated the degradation of this herbicide to a hydroxylated metabolite. Reductions in the lipophilicity and, therefore, mobility of this compound following hydroxylation may account for NA-induced retention of radiolabel in the root system. Hydroxylation of AC 263222 suggested that NA may stimulate the activity of enzymes involved in oxidative herbicide metabolism, such as the cytochrome P450 mono-oxygenases. In agreement with this theory, the cytochrome P450 inhibitor, 1-aminobenzotriazole (ABT), synergized AC 263222 activity and inhibited its hyroxylation in vivo. NA seed-dressing enhanced the total cytochrome P450 and b5 content of microsomes prepared from etiolated maize shoots. Isolated microsomes catalyzed AC 263222 hydroxylation in vitro. This activity possessed the characteristics of a cytochrome P450 mono-oxygenase, being NADPH-dependent and susceptible to inhibition by ABT. Activity was stimulated four-fold following NA seed treatment. Differential NA enhancement of AC 263222 hydroxylase and the cytochrome P450-dependent cinnamic acid-4-hydroxylase (CA4H) activity, suggested that separate P450 isozymes were responsible for each activity. These results indicate that the protective effects of NA result from enhancement of AC 263222 hydroxylation and concomitant reduction in herbicide translocation. This may be attributed to the stimulation of a microsomal cytochrome P450 system. © 1998 SCI.  相似文献   

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