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1.
Absorption of methazole by leaves of onion (Allium cepa), Stellaria media, Matricaria matricarioides and Veronica persica was rapid for the first 24 h after treatment and continued at a slower rate for up to 6 days to reach a maximum of between 35 and 60% of the amount applied. Differences in absorption between species were generally small. Absorption by the cotyledon of onion was greater than absorption into true leaves. Methazole on the leaf surface degraded to 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU) and small amounts of this degraded to 3-(3,4-dichlorophenyl) urea (DCPU). Methazole absorbed into leaves was relatively stable in M. matricarioides and DCPMU accumulated slowly. The rate of degradation was more rapid in the cotyledons than in the true leaves. Both in leaves and in cotyledons of onion and S. media, methazole degraded rapidly to DCPMU and this accumulated; in those of V. persica, DCPMU was degraded quickly to DCPU and unidentified products. The amount of DCPMU accumulated in the shoots was broadly correlated with the relative phytotoxicity of methazole to the different species, except for young seedlings of V. persica which contained no DCPMU but were susceptible to methazole.  相似文献   

2.
The comparative uptake and metabolism of 14C-labeled 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (methazole), a herbicide, in prickly sida (Sida spinosa L.) and cotton (Gossypium hirsutum L.) were investigated as physiological bases for herbicidal selectivity, using thin layer chromatography, autoradiography, and liquid scintillation counting. Prickly sida and cotton readily absorbed and translocated 14C from nutrient solution containing [14C]methazole. Only acropetal translocation of 14C was observed. Methazole was rapidly metabolized to 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) and other metabolites by both species. Although metabolism appeared to be qualitatively the same, quantitative differences between species were evident. Methazole was converted to DCPMU (also phytotoxic) more readily by prickly sida than cotton; however, DCPMU was more readily detoxified to 1-(3,4-dichlorophenyl) urea (DCPU) by cotton than prickly sida. More 14C per unit weight was present in the prickly sida shoots than in cotton shoots. Also, a larger portion of the methanol-extractable 14C was herbicidal in the shoots of prickly sida than of cotton. Thus, the differential tolerances of prickly sida and cotton to methazole may be explained, in part, by differential uptake and metabolism of methazole and DCPMU.  相似文献   

3.
[14C]-Labelled methazole, 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU), 1-(3,4-dichlorophenyl)urea (DCPU), and diuron were incubated in soil at 20°C and field capacity soil moisture content. Decomposition followed first-order kinetics; half-lives for degradation of these four compounds were 2.4, 144, 30 and 108 days respectively. The amount of DCPMU and DCPU that could be extracted decreased with time and the decrease was accompanied by the generation of an equivalent amount of 14CO2. This was not so in the studies with diuron and methazole, however, and the decrease in the concentrations of radioactivity extracted from soil treated with these compounds could not be entirely accounted for as carbon dioxide. It is concluded that the unextractable radiochemical that was present was DCPMU. Methazole appeared to be degraded through DCPMU to 3,4-dichloroaniline (DCA) with the production of only traces of DCPU.  相似文献   

4.
The mechanisms for the tolerance of purple nutsedge (Cyperus rotundus L.) and susceptibility of yellow nutsedge (Cyperus esculentus L.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] were studied. Both species absorbed and translocated[14C]methazole and metabolites from nutrient solution; however, greater amounts of 14C per unit weight were detected in yellow than in purple nutsedge. Although intact plants and excised leaves of both species rapidly metabolized methazole to DCPMU [1-(3,4-dichlorophenyl)-3-methylurea], detoxification of DCPMU to DCPU [1-(3,4-dichlorophenyl) urea] occurred more slowly in yellow than in purple nutsedge. Compared to yellow nutsedge, a greater percentage of the radioactivity in purple nutsedge was recovered as polar products. Polar products were converted to the free forms of the parent herbicide and to phytotoxic DCPMU by proteolytic enzyme digestion. Based on the findings of this study, at least three mechanisms (differential absorption, metabolism, and formation of polar products) account for the differential tolerance of these two species to methazole.  相似文献   

5.
The responses of onion (Allium cepa). Veronica persica, Matricaria matricarioides and Stellaria media to post-emergence applications of methazole were measured in field and glasshouse experiments. Stellaria media was the most susceptible species and V. persica the least. Plants of all species became more tolerant the larger they were at the time of treatment, and this was most pronounced in onion. Onion generally retained less spray per unit of dry weight than the other three species and retention was less on old compared with young plants, whereas with the weed species, this did not change appreciably with age. There was a progressive increase in the amount of structured crystalline wax on successive onion leaves which resulted in larger contact angles between droplets and the leaf surfaces and lower spray retention per unit of dry weight. There was less wax development on the leaf surfaces, increased spray retention, and increased susceptibility to methazole in onion treated pre-emergence with ethofumesate thus confirming that these factors are interrelated. While the increased tolerance of onion to methazole with age could be explained in part by decreased retention of herbicide, this was not so for the weed species, and other factors must determine their change in tolerance with age.  相似文献   

6.
The metabolic fate of the 14C-labeled herbicide, 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (bioxone), in cotton (Gossypium hirsutum L. “Acala 4-42-77”) was studied using thin-layer chromatography, autoradiography, and counting. Bioxone-14C was readily metabolized by cotton tissue to 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) and 1-(3,4-dichlorophenyl)urea (DCPU). Leaf discs metabolized bioxone-14C rapidly; 12 hr posttreatment, 65% of the 14C in methanol extracts was in forms other than intact herbicide. Excised leaves treated through the petiole with either heterocyclic ring-labeled or phenyl ring-labeled herbicide contained little bioxone-14C after 1 day; DCPMU was formed early then decreased with time. DCPU accounted for 55–70% of the 14C in excised leaves 3 days posttreatment. In intact plants treated via the roots, the herbicide was rapidly metabolized in the roots to DCPMU and DCPU; little or no intact herbicide was translocated to the leaves. Little radioactivity accumulated in the roots with time; the radioactivity in the leaves accounted for 80–90% of the methanol-soluble 14C 47 days posttreatment. Most of the 14C in the leaves was recovered as DCPU (50–60%) and unidentified polar metabolite(s) which remained at the origin of the thin-layer plates (30–40%). The percentage of radioactivity which remained in cotton residue after methanol extraction increased with time. Digestion of the plant residues with the proteolytic enzyme pronase indicated that some of the nonextractable 14C may be DCPMU and DCPU complexed with proteins. Similar metabolic patterns were noted after treatment with either heterocyclic ring-labeled or phenyl ring-labeled bioxone-14C. Generally, bioxone was metabolized to DCPMU which in turn was demethylated to DCPU. The herbicide and DCPMU were 20 times as toxic as DCPU to oat (Avena sativa L.), a susceptible species.  相似文献   

7.
[14C]-Labelled methazole was incubated in six soils at 25°C and with soil moisture at field capacity. Under these conditions, methazole was unstable, the concentration declined following first-order kinetics with half-life values in the soils ranging from 2.3 to 5.0 days. The main degradation product was 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) which was more stable than the parent compound. After about 160 days, DCPMU accounted for 30 to 45% of the initial methazole concentration. Degradation of methazole and DCPMU was affected by soil temperature and moisture content. With methazole, half-lives in one soil at field capacity moisture content and temperatures of 25, 15 and 5°C were 3.5, 8.7 and 31.1 days respectively. The half-life at 25°C was increased to 5.0 days at 50% of field capacity and 9.6 days at 25% of field capacity. A proportion of the initial radioactivity added to the soil could not be extracted and this proportion increased with time. After 160 days this unextractable radioactivity accounted for up to 70% of the amount applied.  相似文献   

8.
BACKGROUND: Field studies of diuron and its metabolites 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU), 3,4-dichlorophenylurea (DCPU) and 3,4-dichloroaniline (DCA) were conducted in a farm soil and in stream sediments in coastal Queensland, Australia. RESULTS: During a 38 week period after a 1.6 kg ha(-1) diuron application, 70-100% of detected compounds were within 0-15 cm of the farm soil, and 3-10% reached the 30-45 cm depth. First-order t(1/2) degradation averaged 49+/-0.9 days for the 0-15, 0-30 and 0-45 cm soil depths. Farm runoff was collected in the first 13-50 min of episodes lasting 55-90 min. Average concentrations of diuron, DCPU and DCPMU in runoff were 93, 30 and 83-825 microg L(-1) respectively. Their total loading in all runoff was >0.6% of applied diuron. Diuron and DCPMU concentrations in stream sediments were between 3-22 and 4-31 microg kg(-1) soil respectively. The DCPMU/diuron sediment ratio was >1. CONCLUSION: Retention of diuron and its metabolites in farm topsoil indicated their negligible potential for groundwater contamination. Minimal amounts of diuron and DCMPU escaped in farm runoff. This may entail a significant loading into the wider environment at annual amounts of application. The concentrations and ratio of diuron and DCPMU in stream sediments indicated that they had prolonged residence times and potential for accumulation in sediments. The higher ecotoxicity of DCPMU compared with diuron and the combined presence of both compounds in stream sediments suggest that together they would have a greater impact on sensitive aquatic species than as currently apportioned by assessments that are based upon diuron alone.  相似文献   

9.
Anaerobic microbial degradation of selected 3,4-dihalogenated aromatic compounds was studied in medium inoculated with pond sediment. Sediment samples were collected from a diuron-treated pond. Diuron was dehalogenated at the para position, forming CPDMU as the sole degradation product. DCPU was similarly dehalogenated at the para position, forming MCPU as the only degradation product. Linuron degradation resulted in four products: one, CPMMU, was the result of biological dehalogenation at the para position; another, DCPMU, was the result of chemical degradation; and the other two products were unidentified. Chlorbromuron degradation formed three unidentified products. Stam, an acylanilide, was degraded, forming two products, one of which was possibly 3-chloropropioanilide. CIPC and an unidentified compound were formed from DCIP. No degradation of parent compounds or appearance of degradation products were detected in mixtures of each test compound and sterile sediment except linuron.  相似文献   

10.
W. MERSIE 《Weed Research》1995,35(1):15-18
Witloof chicory (Cichorium intybus L.) is tolerant to propyzamide and common amaranth (Amaranthus retroflexus L.) is sensitive. The absorption, translocation, and metabolism of propyzamide was studied in seedlings of witloof chicory and common amaranth to determine if differences in these processes cause the differential sensitivity. At 24,48, and 72 h after root treatment, there was no difference in the concentration of 14C (g?1 plant dry wt) in com-mon amaranth and witloof chicory. Approximately 50% of the absorbed 14C was translocated out of the roots to shoots of both species at 24 and 48 h after treatment. After 72 h about 55 and 74% of the absorbed 14C was translocated to shoots of witloof chicory and common amaranth, respectively. Distribution of 14C (g?1 plant dry wt) in plant parts of witloof chicory and common amaranth seedlings was similar. Roots of both species accumulated the highest concentration of total 14C, whereas shoots contained the lowest. Thin layer chromatography revealed that the herbicide was metabolized in neither species 48 h after treatment. No differences were found in absorption, translocation, or metabolism between witloof chicory and common amaranth with regard to propyzamide.  相似文献   

11.
The concentrations of haloxyfop in nutrient solution required to reduce the total plant dry weight of soybean (Glycine max L. Merr. ‘Evans’), red fescue (Festuca rubra L. ‘Pennlawn’), and tall fescue (Festuca arundinacea Schreb. ‘Houndog’) by 50% (GR50) were determined. The GR50) values for soybean, red fescue and tall fescue were 76 μM, 3μM and 0.4 μM, respectively. The reduction in growth in roots and shoots of soybean was similar. In contrast, the relative reduction in root tissue weight was greater than that for foliar tissue in both grass species. The amount of 14C-haloxyfop in soybean roots or shoots was higher than in red fescue or tall fescue. Red fescue accumulated less haloxyfop in the foliage than in the roots. On the other hand, similar amounts of 14C-haloxyfop accumulated in both organs in both soybean and tall fescue. 14C-haloxyfop appeared to be actively absorbed by the roots of all species. Soybean absorbed more nutrient solution, but utilized it less on a per gram dry matter produced basis than the grass species. Differences in the uptake and translocation of haloxyfop by roots do not account for differences in tolerance between species. However, a higher level of retention of haloxyfop in the roots of red fescue than in tall fescue may provide the former with an additional selectivity advantage under conditions where there is significant root exposure to the herbicide.  相似文献   

12.
The differential tolerance of resislant creeping red fescue (Fes- tuca rubra L, var, rutra) and susceptibie reed canarygrass (Pha- laris arundinacea L.) seedlings to glyphosate [N-(phosphono- meihyDglycine) was confirmed under growth chamber condilions. The absorption, transiocation and metabolism of 14C-glyphosate was examined in both species to determine if differences in these processes could account for the observed selectivity, Creepmg red fescue actually absorbed more glyphosate than did t-eed canarygrass, and both species rapidly translocated the herbicide throughout their respective tissues. No metabolism of glyphosate was detected in either species. Differential interception and retention of the glyphosate spray can probably be eliminated as possible selectivity mechanisms. The relative tolerance of creeping red fescue to glyphosale appears to be related to its ability lo regenerate roots and shoots from the crown of the plant, but the mechanism of resistance remains obscure.  相似文献   

13.
The effect of various herbicides on photosynthesis, respiration and transpiration of intact plants has been studied in a routine assembly. Simultaneous measurements were made under different experimental conditions in four small plant chambers, in which the shoots of various plant species can be accommodated. The herbicide is applied during measurement, so that the effect can be related to the photosynthetic activity of the same plants before treatment. The selectivity of various herbicides was studied by determining the capacity of a plant species to inactivate a herbicide absorbed by the roots. These and other differential effects of various herbicides on photosynthetic activity of different plant species coincide with the selective properties in the field. Such differences are also observed after leaf sprayings. The duration of the experiments is kept short. Bean plants were studied under various experimental conditions of air humidity, light intensity and temperature resulting in different transpiration rates. The decrease in photosynthetic activity owing to the presence of a herbicide in the nutrient solution at a standard concentration was more rapid at the higher transpiration rates. The total transpiration during treatment up to 50% inhibition of photosynthesis was constant under the various experimental conditions. Specific inhibitors of the photosynthetic process had a more pronounced effect on the photosynthetic activity than on transpiration rate. Some other herbicides affect transpiration as well as photosynthesis.  相似文献   

14.
BACKGROUND: Aminocyclopyrachlor is a new herbicide proposed to control broadleaf weeds and shrubs in non‐crop and rangeland systems. To gain a better understanding of observed field efficacy, the uptake and translocation of foliar‐applied aminocyclopyrachlor (DPX‐MAT28) and aminocyclopyrachlor methyl ester (DPX‐KJM44) were evaluated in two annuals, prickly lettuce (Lactuca serriola L.) and yellow starthistle (Centaurea solstitialis L.), and one perennial, rush skeletonweed (Chondrilla juncea L.). RESULTS: Absorption and translocation varied between species. While absorption of DPX‐KJM44 was greater than absorption of DPX‐MAT28, rush skeletonweed absorbed the most, followed by yellow starthistle and prickly lettuce. Overall, the total translocation of either herbicide was highest in yellow starthistle, followed by rush skeletonweed and prickly lettuce. Proportional herbicide movement between species was similar, with the majority translocating to developing shoots. However, in rush skeletonweed, early translocation was directed to root tissue. In rush skeletonweed, no DPX‐MAT28 metabolism occurred, while DPX‐KJM44 was rapidly de‐esterified and translocated as DPX‐MAT28. CONCLUSION: Aminocyclopyrachlor absorption and translocation are dependent on active ingredient structure and species sensitivity. Highly sensitive species such as prickly lettuce absorb and translocate less material than relatively less sensitive species such as rush skeletonweed. De‐esterification of DPX‐KJM44 appears to delay translocation of the resulting acid in yellow starthistle and rush skeletonweed. Copyright © 2011 Society of Chemical Industry  相似文献   

15.
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   

16.
Experiments were conducted to examine the up take, translocation and metabolism by S. vulgaris of two distinctly different herbicides: 2,4-D, a phenoxyalkanoic acid with growth regulator activity to which this species exhibits complete tolerance, and chlorsulfuron, a sul-fonylurea to which S. vulgaris is highly sensitive. Despite their structural dissimilarities 2,4-D and chlorsulfuron was readily absorbed by S. vulgaris with 65 and 69%, respectively, of the applied dosage being absorbed within 72 hours after treatment. Approximately 35% of the 2,4-D and 10% of the chlorsulfuron label was translocated out of the treated leaf after 72 hours. Neither herbicide accumulated in the terminal bud. Seventy-two hours after treatment 63% of the recovered 14C remained as unaltered 2,4-D in S. vulgaris, while in tomato, a 2,4-D sensitive species, 65% of the recovered 14C remained as intact herbicide. In S. vulgaris approximately 86% of the radioactivity remained as intact chlorsulfuron 72 hours after treatment compared to 12% in the tolerant wheat. The tolerance of S. vulgaris to 2,4-D could not be accounted for by limited absorption, translocation nor metabolic degradation of the herbicide. The sensitivity of S. vulgaris to chlorsulfuron would appear to be related to the inability of this species to metabolize the herbicide molecule.  相似文献   

17.
Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] was applied post-emergence at 2-1 kg/ha to crops of onion (Allium cepa L.) grown on a sandy loam and the activity present in the surface 0–5 cm of soil assessed by bioassay. In spring-sown crops, activity at harvest varied from 25 to 78% of the initial acitivity in different years; losses were restricted by low temperature and low rainfall. In autumn-sown crops, little loss occurred during winter and most of the activity remained in the surface 0-5 cm. The results emphasize the need for caution in choice and timing of following crops.  相似文献   

18.
In recent years in Finland, Fusarium infections in onions have increased, both in the field and in storage, and Fusarium species have taken the place of Botrytis as the worst pathogens causing post‐harvest rot of onion. To study Fusarium occurrence, samples were taken from onion sets, harvested onions and also from other plants grown in the onion fields. Isolates of five Fusarium species found in the survey were tested for pathogenicity on onion. Fusarium oxysporum was frequently found in onions and other plants, and, of the isolates tested, 31% caused disease symptoms and 15% caused growth stunting in onion seedlings. Fusarium proliferatum, a species previously not reported in Finland, was also identified. Over 50% of the diseased onion crop samples were infected with F. proliferatum, and all the F. proliferatum isolates tested were pathogenic to onion. Thus, compared to F. oxysporum, F. proliferatum seems to be more aggressive on onion. Also some of the F. redolens isolates were highly virulent, killing onion seedlings. Comparison of the translation elongation factor 1α gene sequences revealed that the majority of the aggressive isolates of F. oxysporum f. sp. cepae group together and are distinct from the other isolates. Incidence and relative proportions of the different Fusarium species differed between the sets and the mature bulbs. More research is required to determine to what extent Fusarium infections spoiling onions originate from infected onion sets rather than the field soil.  相似文献   

19.
为明确新型除草剂喹草酮应用于小麦田的除草效果及对小麦的安全性,在温室内采用共毒系数法对喹草酮与辛酰溴苯腈联合作用进行测定,并验证喹草酮与辛酰溴苯腈两者混用以及与双氟磺草胺三者混用时对小麦田杂草的防效,以及对小麦的安全性。温室试验结果表明,喹草酮对阿拉伯婆婆纳Veronica persica防效优,试验剂量下全部死亡,对播娘蒿Descurainia sophia和麦家公 Lithospermum arvense的GR50分别为12.67 g （a.i.）/hm2和152.99 g （a.i.）/hm2;辛酰溴苯腈对播娘蒿和麦家公防效优,其GR50分别为26.22 g （a.i.）/hm2和13.36 g （a.i.）/hm2,对阿拉伯婆婆纳防效略差,GR50为85.12 g （a.i.）/hm2。喹草酮与辛酰溴苯腈按有效成分用量1：1~1：2.5配比时,阿拉伯婆婆纳全部死亡,对播娘蒿的共毒系数在140.34~202.77之间,呈明显增效作用,对麦家公的共毒系数达700.00以上,也呈明显增效作用。田间试验结果表明,喹草酮对阿拉伯婆婆纳防效高,而对猪殃殃Galium aparine和播娘蒿略差;辛酰溴苯腈作用速度快,但后期部分杂草返青,喹草酮与辛酰溴苯腈复配后优势互补,对小麦田阔叶杂草阿拉伯婆婆纳、猪殃殃和播娘蒿防效均优,鲜重防效在88.54%~ 93.83%之间,且杂草死亡速度快,在2种药剂基础上加入双氟磺草胺后,鲜重防效在96.12%以上。喹草酮单剂或与辛酰溴苯腈、双氟磺草胺的混配处理不影响小麦的正常生长。  相似文献   

20.
Fosamine (ammonium ethyl carbamoylphosphonate) formulated as a 1% w/v solution in 0–25%v/v Tween 20 was absorbed slowly by detached leaves of Rubus procerus P.J. Muell., 35% of the applied herbicide being absorbed after 96 h. Fosamine does not appear to be rainfast, as up to 80% of the applied herbicide and 99.9% of the removable herbicide were removed from the leaves by washing for 5 min in distilled water. Translocalion of fosamine was rapid in small R. procerus plants and followed a pattern similar to that taken by assimilates: 2,4,5–T did not translocate to the root system as readily as fosamine or assimilates.  相似文献   

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