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1.
Florasulam is a triazolopyrimidine sulfonanilide post-emergence broadleaf herbicide for use in wheat (Triticum aestivum L.). The selectivity of florasulam to wheat has been determined to be related primarily to a differential rate of metabolism between wheat with a half-life of 2.4 h and broadleaf weeds with half-lives ranging from 19 to >48 h. To a lesser extent, selectivity, at least for the broadleaf weed cleavers (Galium aparine L.), involves uptake differences. Rate of metabolism data were generated using greenhouse-grown plants injected with radiolabelled florasulam and subsequent extraction and processing by high-performance liquid chromatography (HPLC). Structures of metabolites were determined by isolation for nuclear magnetic resonance and liquid chromatography/mass spectrometry. Wheat plants metabolised florasulam by hydroxylation of the aniline ring para to the nitrogen, followed by conjugation to glucose. Metabolism by broadleaf weeds was so slow that isolation of metabolite was not possible, but comparison of HPLC data suggested hydroxylation as the major pathway.  相似文献   

2.
Metabolism studies are necessary in the understanding of the mode of action of herbicides, their loss of activity and their selectivity. Molecular change of a herbicide may involve photochemical degradation, and non-enzymic or enzymic reactions that normally inactivate, but in some cases activate, a compound. Molecular change resulting in activation is discussed with regard to the (2,4-dichlorophenoxy)-alkanoic acids, the pyridines paraquat and diquat, the anilides benzoylprop-ethyl and flamprop-methyl, and the thiocarbamates. Inactivation due to metabolism is reviewed with regard to herbicides applied to soil and foliage. Of the soil-applied herbicides, the 1,3,5-triazines and the nitrile dichlobenil are exemplified as cases in which selectivity may be due largely to interspecific differences in metabolism. Of the foliage-applied translocated compounds, the metabolism of the phenoxyalkanoic acid herbicides has been extensively investigated and may involve conjugation, side-chain degradation or extension, ring hydroxylation and protein binding. The mode of action of glyphosate, asulam, dalapon and aminotriazole in perennial weeds is discussed with particular reference to their metabolism.  相似文献   

3.
Experiments were conducted to investigate the metabolism of a novel herbicide ZJ0273 in the seedlings of the susceptible crickweed and tolerant oilseed rape. Six metabolites of ZJ0273 were identified in crickweed seedlings, compared to 8 metabolites in oilseed rape. Among these metabolites, the metabolite M7, with the chemical name of 2-(4,6-dimethoxypyrimidin-2-yloxy) benzoic acid, was found to be the most herbicidally effective molecule with significant inhibition to acetolactate synthase. The differences in the amount and rate of ZJ0273 transformation to M7, and its metabolic detoxification, contributed to the primary mechanism of herbicidal selectivity of ZJ0273.  相似文献   

4.
Propanil-resistant barnyardgrass populations, previously verified in Arkansas rice fields and in greenhouse tests, were examined in the laboratory to ascertain if the resistance mechanism in this weed biotype was herbicide metabolism. Propanil-resistant barnyardgrass was controlled >95% in the greenhouse when carbaryl (an aryl acylamidase inhibitor) was applied two days prior to propanil. Laboratory studies with 14C-radiolabelled propanil indicated that the herbicide was hydrolysed in propanil-resistant barnyardgrass and rice to form 3,4-dichloroaniline, but no detectable hydrolysis occurred in susceptible barnyardgrass. Two additional polar metabolites were detected in propanil-resistant barnyardgrass and rice and tentatively identified by thin layer chromatography. Overall, metabolites in the resistant barnyardgrass had Rf values similar to those in rice, indicating similar metabolism for both species. These data, coupled with data from a previous report on the resistant biotype showing no differential absorption/translocation or molecular modification of the herbicide binding site in the resistant biotype, indicate that the resistance mechanism is metabolic degradation of propanil. © of SCI.  相似文献   

5.
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   

6.
The herbicide chlortoluron readily underwent oxidative metabolism in suspension cultures of cotton and maize. Major attack in cotton cells was by stepwise N-demethylation followed by relatively slow ring-methyl hydroxylation. The most prominent single metabolites seen after 1 day and 7 days were 3-(3-chloro-p-tolyl)urea and its benzyl alcohol analogue, respectively. In maize cells, ring-methyl hydroxylation was apparently the preferred mode of metabolism. Only low amounts of the demethylated derivatives of chlortoluron were evident, and the major residues present at both 2 days and 7 days were the benzyl alcohol derivative of chlortoluron and 3-(3-chloro-4-hydroxymethylphenyl)-1-methylurea. In both species, a substantial proportion of the free ‘phase 1’ metabolites was initially expelled to the medium, but at later times, these were found largely within the cell as polar conjugates. Two approaches were used to examine the influence of the composition of the medium on metabolism. Firstly, cells of both species were grown in four different nutrient media, which were selected to give variation in the organic nutrient and growth factor fraction; secondly, cells were grown in one medium, varying the level of 2, 4-D. In cotton, the rate of metabolism of chlortoluron correlated with the extent to which the four media supported cell growth, Variations were also seen for maize but no correlation with growth rate could be made. For both species, metabolism was retarded when cells were sub-cultured from a medium lacking coconut water to one containing 10% of this supplement. A fifty-fold range in concentration of 2, 4-D had little effect on metabolism in cotton, although a fall-off in rate occurred at the highest level. However, in maize a marked trend towards accelerated metabolism with increasing content of 2, 4-D up to 20 mg litre?1 was seen, which was independent of effects on growth. The qualitative nature of chlortoluron metabolism in both species was unperturbed by substantial variations in the composition of the medium.  相似文献   

7.
Metabolism and selectivity of rice herbicides in plants   总被引：1，自引：0，他引：1  
Chemical weed control with effective and highly active herbicides has been very useful and convenient means. It has contributed to stable crop production and is labor saving. Recent herbicides have had characteristics such as high effectiveness without causing environmental pollution or harmful effects, and appropriate herbicides having high activity, low toxicity, high selectivity and being non-persistent have been developed. The metabolism of rice herbicides used mainly in Japan, such as sulfonylurea, chloroacetamide, acylamide, urea, thiocarbamate, pyrazole, triazine, diphenyl ether, phthalimide, phenoxy, aryloxyphenoxypropionate, etc., is reviewed, and its involvement in selectivity is also discussed. The metabolism of herbicides is closely related to their activity and selectivity. Differential herbicide metabolism in plants is a contributing factor of selectivity between crops and weeds. Chemicals that are more detoxified in crops and/or more activated or less detoxified in weeds are considered as being effective and selective herbicides. The metabolism of various types of rice herbicides includes: oxidative reaction (ring and chain hydroxylation, O - and N -dealkylation), hydrolysis and subsequent glucose conjugation, and glutathione conjugation in rice. These detoxicative activities are much higher in rice than weeds in paddies, and this leads to the selectivity of herbicides. Enzymes, oxidase, P-450 mono-oxygenase, esterase, acylamidase, glucosyl transferase, glutathione transferase, etc., play important roles in herbicide metabolism and selectivity.  相似文献   

8.
The sulfonylurea herbicides are characterized by broad-spectrum weed control at very low use rates (c. 2–75 g ha?1), good crop selectivity, and very low acute and chronic animal toxicity. This class of herbicides acts through inhibition of acetolactate synthase (EC 4.1.3.18; also known as acetohydroxyacid synthase), thereby blocking the biosynthesis of the branched-chain amino acids valine, leucine and isoleucine. This inhibition leads to the rapid cessation of plant cell division and growth. Crop-selective sulfonylurea herbicides have been commercialized for use in wheat, barley, rice, corn, soybeans and oilseed rape, with additional crop-selective compounds in cotton, potatoes, and sugarbeet having been noted. Crop selectivity results from rapid metabolic inactivation of the herbicide in the tolerant crop. Under growth-room conditions, metabolic half-lives in tolerant crop plants range from 1–5 h, while sensitive plant species metabolize these herbicides much more slowly, with half-lives > 20 h. Pathways by which sulfonylurea herbicides are inactivated among these plants include aryl and aliphatic hydroxylation followed by glucose conjugation, sulfonylurea bridge hydrolysis and sulfonamide bond cleavage, oxidative O-demethylation and direct conjugation with (homo)glutathione. Sulfonylurea herbicides degrade in soil through a combination of bridge hydrolysis and microbial degradation. Hydrolysis is significantly faster under acidic (pH 5) than alkaline (pH 8) conditions, allowing the use of soil pH as a predictor of soil residual activity. Chemical and microbial processes combine to give typical field dissipation half-lives of 1–6 weeks, depending on the soil type, location and compound. Very short residual sulfonylurea herbicides with enhanced susceptibility to hydrolysis (DPX-L5300) and microbial degradation (thifensulfuron-methyl) have been developed.  相似文献   

9.
Pathways of chlortoluron metabolism were compared in excised leaves of four tolerant species, namely wheat (Triticum aestivum var Clement), Bromus sterilis, Galium aparine and Veronica persica. The herbicide was principally detoxified by hydroxylation of the ring methyl in wheat and by N-dealkylation in Veronica persica. Both pathways were involved in Bromus sterilis and Galium aparine. Kinetic study of the degradation showed that capacity to form non-toxic conjugates could, at least partially, explain the tolerance of these species to chlortoluron. In plants treated with 1-aminobenzotriazole, a cytochrome P-450 enzyme inactivator, N-dealkylation of chlortoluron was little or not affected, but ring methyl hydroxylation was strongly inhibited. This suggests that at least two distinct enzymatic systems could participate in this metabolism. Moreover, cytochrome P-450 enzymes could be involved in the ring methyl hydroxylating reaction.  相似文献   

10.
Cytochrome P450s (P450s) have been at the center of herbicide metabolism research as a result of their ability to endow selectivity in crops and resistance in weeds. In the last 20 years, ≈30 P450s from diverse plant species have been revealed to possess herbicide‐metabolizing function, some of which were demonstrated to play a key role in plant herbicide sensitivity. Recent research even demonstrated that some P450s from crops and weeds metabolize numerous herbicides from various chemical backbones, which highlights the importance of P450s in the current agricultural systems. However, due to the enormous number of plant P450s and the complexity of their function, expression and regulation, it remains a challenge to fully explore the potential of P450‐mediated herbicide metabolism in crop improvement and herbicide resistance mitigation. Differences in the substrate specificity of each herbicide‐metabolizing P450 are now evident. Comparisons of the substrate specificity and protein structures of P450s will be beneficial for the discovery of selective herbicides and may lead to the development of crops with higher herbicide tolerance by transgenics or genome‐editing technologies. Furthermore, the knowledge will help design sound management strategies for weed resistance including the prediction of cross‐resistance patterns. Overcoming the ambiguity of P450 function in plant xenobiotic pathways will unlock the full potential of this enzyme family in advancing global agriculture and food security. © 2020 Society of Chemical Industry  相似文献   

11.
江汉平原麦田杂草调查   总被引：69，自引：3，他引：66  
运用倒置“Ｗ”９点取样法对江汉平原麦棉套作农田杂草调查,结果表明该地区麦田杂草有１４科２３种,其中禾本科杂草占２７％,阔叶杂草占６９％,莎草科占４％。相对多度达１０以上的麦田杂草依次有猪殃殃、婆婆纳、野燕麦、半夏、通泉草、狗牙根、卷耳等７种,其中猪殃殃、婆婆纳两种双子叶杂草的相对多度达５０和４０,为当地麦田优势种群。  相似文献   

12.
Absorption, translocation and metabolism of 14C-pyridate were compared in tolerant maize. moderately susceptible Polygonum lapathifolium and susceptible Chenopodium album. Foliar absorption was limited in all species, but comparatively higher penetration levels were observed in younger leaves of dicotyledonous species. The absorbed radioactivity was not very mobile and translocation appeared mainly sym-plastic. Herbicide selectivity could not be explained on the basis of absorption and transport. Chenopodium and P. lapathifolium degraded pyridate and formed unstable water-soluble conjugates that easily released a phytotoxic metabolite. By contrast, more stable unidentified water-soluble metabolites were found in maize. That metabolic difference could explain the selectivity of pyridate.  相似文献   

13.
The behaviour of 14C-EL-107 has been evaluated in winter wheat and rape, which are tolerant and susceptible, respectively, under field conditions. After 10- to 13-days’growth under controlled conditions, seedlings were allowed to absorb the herbicide through the roots. Two experiments were conducted to study the absorption and the metabolism of EL-107. Absorption was estimated during a 5-day treatment at the rate of 1–47 μM, and metabolism was studied after a 1-day treatment at 14.7 μM. The results showed that (i) rape plants absorbed more herbicide than wheat, and translocated less radioactivity into their shoots, and (ii) the metabolism of EL-107 proceeded actively only in the shoots, where EL-107 disappeared at similar rates in the two species, giving rise to the same metabolites. In conclusion, the respective degrees of susceptibility of the two species could be partly related to differences in the concentration of the herbicide in the roots, where it can exert its phytotoxic effect.  相似文献   

14.
A major factor responsible for the selectivity of chlorsulfuron [2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]benzenesulfonamide] (formerly DPX-4189), as a postemergence herbicide for small grains is the ability of the crop plants to metabolize the herbicide. Chlorsulfuron is the active ingredient in Du Pont “Glean” weed killer. Tolerant plants such as wheat, oats, and barley rapidly metabolize chlorsulfuron to a polar, inactive product. This metabolite has been characterized as the O-glycoside of chlorsulfuron in which the phenyl ring has undergone hydroxylation followed by conjugation with a carbohydrate moiety. Sensitive broadleaf plants show little or no metabolism of chlorsulfuron.  相似文献   

15.
Metabolism of the herbicide thiazopyr [methyl 2-(difluoromethyl)-5-(4, 5-dihydroO-lhiazo!vt)-4-(2-methylpropy!)-6-(trinuorornethyl)-3-pyridinecarboxy-late] was examined in young seedlings of redroot pigweed, grain sorghum, sunflower, corn and soybean. As previously observed with rat liver microsomes plants predominantly metabolized thiazopyr via oxidation reactions. Sulfur and carbon atoms in the thiazoline ring were the primary sites of plant oxygenases. De-esterification was also identified as an important pathway of transformations in plants. Although similar pathways of thiazopyr metabolism were observed among plants, our data indicated species differences in rates of thiazopyr degradation. Among species examined, pigweed (Amaranthus retroflexus L.) showed the fastest metabolism. Thiazopyr metabolism in pigweed was significantly inhibited by several cytochrome P450 monooxygenase inhibitors, among which tetcyclacis (TET) and piperonyl butoxide (PBO) were the most inhibitory. Thiazopyr metabolism in pigweed was not inhibited by organophosphates, known inhibitors of esterases. The results suggest that thiazopyr metabolism in plants is predominantly mediated via plant mono-oxygenases.  相似文献   

16.
Cinidon-ethyl (BAS 615H) is a new herbicide of isoindoldione structure which selectively controls a wide spectrum of broadleaf weeds in cereals. The uptake, translocation, metabolism and mode of action of cinidon-ethyl were investigated in Galium aparine L, Solanum nigrum L and the tolerant crop species wheat (Triticum aestivum L). When plants at the second-leaf stage were foliarly treated with cinidon-ethyl equivalent to a field rate of 50 g ha−1 for 48 h, the light requirement for phytotoxicity and the symptoms of plant damage in the weed species, including rapid chlorophyll bleaching, desiccation and necrosis of the green tissues, were identical to those of inhibitors of porphyrin synthesis, such as acifluorfen-methyl. The selectivity of cinidon-ethyl between wheat and the weed species has been quantified as approximately 500-fold. Cinidon-ethyl strongly inhibited protoporphyrinogen oxidase (Protox) activity in vitro, with I50 values of approximately 1 nM for the enzyme isolated from the weed species and from wheat. However, subsequent effects of herbicide action, with accumulation of protoporphyrin IX, light-dependent formation of 1-aminocyclopropane-1-carboxylic acid-derived ethylene, ethane evolution and desiccation of the green tissue, were induced by cinidon-ethyl only in the weed species. After foliar application of [14C] cinidon-ethyl, the herbicide, due to its lipophilic nature, was rapidly adsorbed by the epicuticular wax layer of the leaf surface before it penetrated into the leaf tissue more slowly. No significant differences between foliar and root absorption and translocation of the herbicide by S nigrum, G aparine and wheat were found. After foliar or root application of [14C]- cinidon-ethyl, translocation of 14C into untreated plant parts was minimal, as demonstrated by combustion analysis and autoradiography. Metabolism of [14C]cinidon-ethyl via its E-isomer and acid to further metabolites was more rapid in wheat than in S nigrum and G aparine. After 32 h of foliar treatment with 50 g ha−1 of the [14C]-herbicide, approximately 47%, 36%, and 12% of the absorbed radioactivity, respectively, were found as unchanged parent or its biologically low active E-isomer and acid in the leaf tissue of G aparine, S nigrum and wheat. In conclusion, cinidon-ethyl is a Protox-inhibiting, peroxidizing herbicide which is effective through contact action in the green tissue of sensitive weed species. It is suggested that a more rapid metabolism, coupled with moderate leaf absorption, contribute to the tolerance of wheat to cinidon-ethyl. © 1999 Society of Chemical Industry  相似文献   

17.
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   

18.
Since varietal differences in allelopathy of crops against weeds were discovered in the 1970s, much research has documented the potential that allelopathic crops offer for integrated weed management with substantially reduced herbicide rates. Research groups worldwide have identified several crop species possessing potent allelopathic interference mediated by root exudation of allelochemicals. Rice, wheat, barley and sorghum have attracted most attention. Past research focused on germplasm screening for elite allelopathic cultivars and the identification of the allelochemicals involved. Based on this, traditional breeding efforts were initiated in rice and wheat to breed agronomically acceptable, weed-suppressive cultivars with improved allelopathic interference. Promising suppressive crosses are under investigation. Molecular approaches have elucidated the genetics of allelopathy by QTL mapping which associated the trait in rice and wheat with several chromosomes and suggested the involvement of several allelochemicals. Potentially important compounds that are constitutively secreted from roots have been identified in all crop species under investigation. Biosynthesis and exudation of these metabolites follow a distinct temporal pattern and can be induced by biotic and abiotic factors. The current state of knowledge suggests that allelopathy involves fluctuating mixtures of allelochemicals and their metabolites as regulated by genotype and developmental stage of the producing plant, environment, cultivation and signalling effects, as well as the chemical or microbial turnover of compounds in the rhizosphere. Functional genomics is being applied to identify genes involved in biosynthesis of several identified allelochemicals, providing the potential to improve allelopathy by molecular breeding. The dynamics of crop allelopathy, inducible processes and plant signalling is gaining growing attention; however, future research should also consider allelochemical release mechanisms, persistence, selectivity and modes of action, as well as consequences of improved crop allelopathy on plant physiology, the environment and management strategies. Creation of weed-suppressive cultivars with improved allelopathic interference is still a challenge, but traditional breeding or biotechnology should pave the way.  相似文献   

19.
Molinate, a selective herbicide, is used for the control of annual and perennial weeds in rice paddy fields. This study was designed to assess the basis of the selective action of molinate between a susceptible broadleaf crop, tobacco, and a resistant graminaceous plant, rice. Experiments were conducted comparing plant growth under different concentrations of molinate, determining the absorption and translocation of the herbicide in the plant and identifying the metabolites in suspension cells. Rice showed greater tolerance to molinate than tobacco. Leaves of tobacco showed retarded and distorted growth at 10 mg liter-1 of molinate 14 days after treatment, but rice leaves were unaffected at this concentration. Higher concentrations of molinate accumulating in the root of tobacco seedlings may inhibit root development and represent a significant factor in the herbicide's selective action. Seven and eight metabolites were found in tobacco and rice cells, respectively, with molinate sulfoxide and molinate sulfone present in both species. © 1998 SCI  相似文献   

20.
Cytochrome P450 proteins play important roles in plant herbicide selectivity. Here, we demonstrate metabolism of the herbicide pelargonic acid by CYP72A18, a novel cytochrome P450 isolated from the rice Oryza sativa L. cv. Nipponbare. The CYP72A18 cDNA was cloned from rice and heterologously expressed in Saccharomyces cerevisiae AH22 cells from the alcohol dehydrogenase (ADH1) promoter. Microsomes isolated from recombinant yeast cells contained the CYP72A18, which was found to catalyze the (ω-1)-hydroxylation of the herbicide pelargonic acid. We also show that (ω-1)-hydroxypelargonic acid has reduced herbicide activity against rice seedlings. Based on these results, we suggest that CYP72A18 participates in the detoxification of the herbicide pelargonic acid in rice plants.  相似文献   

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