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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 interactions between the herbicide S-ethyl dipropyl thiocarbamate (EPTC) and the structurally similar herbicide protectant N,N-diallyl 2,2-dichloroacetamide (DDCA) at the level of herbicide uptake were examined in maize cell cultures. When the two compounds were given simultaneously, DDCA inhibited uptake of [14C]EPTC into maize cells measured for 30 min. A Lineweaver-Burk plot indicated this inhibition to be competitive. N,N-Diallyl 2-chloroacetamide (CDAA), a compound similar in structure to DDCA, inhibited uptake to a lesser extent. Other protectants having no similarity in structure to either DDCA or EPTC had no inhibitory effect on the uptake of EPTC. The data suggest that competition between DDCA and EPTC for a site of uptake may be related to their similarity in chemical structure. Experiments with metabolic inhibitors suggested that uptake of EPTC is not via an active transport mechanism. We suggest that competition for uptake between EPTC and DDCA may represent the first step in a complex series of interactions between the herbicide and its protectant that contributes to the protection of maize from herbicide injury.  相似文献   

3.
The effect of five substituted pyridazinones (pyrazon, San 133-410H, San 9774, norflurazon, and San 6706) on lipid metabolism in groundnut (Arachis hypogaea) leaves was investigated under nonphotosynthetic conditions. In experiments with leaf disks, the uptake of [1-14C]acetate, [32P]orthophosphate, and [35S]sulfate was significantly inhibited by these herbicides and the magnitude of inhibition varied, depending on the substituents. When the incorporation of these precursors into lipids was measured and expressed as percentage of total uptake, no effect was observed in the case of [1-14C]acetate but there was significant inhibition in the incorporation of the other two precursors, suggesting that pyridazinones interfere with the metabolism of the phospholipids and the sulfolipid. None of these compounds affected the uptake of [methyl-14C]choline but all inhibited its incorporation into phosphatidylcholine indicating that phosphatidylcholine metabolism is vulnerable to pyridazinones. The fatty acid synthetase of isolated chloroplasts assayed in the absence of light was inhibited 20–50% by the pyridazinones at 0.1–0.5 mM concentrations. San 9774 showed the most potent inhibition. In addition, the pyridazinone herbicides significantly inhibited sn-glycerol-3-phosphate acyltransferase(s) in both chloroplast and microsomal fractions but showed no effect on phosphatidic acid phosphatase. The magnitude of inhibition of fatty acid synthetase and acyltransferase(s) is related to the nature of the substituent groups on the herbicide. Trifluorophenyl substitution at position 2 or amino substitution at position 5 of the pyridazinone molecule caused the maximum inhibitory effect.  相似文献   

4.
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   

5.
l-[U-14C]sucrose accumulation by phloem sieve tube members (PSTM) of wheat (Triticum aestivum L. ‘Holley’) and sorghum (Sorghum bicolor L. ‘G522 DR’) was inhibited by the nonpermeant sulfhydryl inhibitor p-chloromercuribenzenesulfonic acid (PCMBS), and this inhibition was reversed by the permeant sulfhydryl protectants dithiothreitol (DTT) and dithioerythritol (DTE). S-Ethyl dipropylthiocarbamate (EPTC) (≤0.1 mM) did not inhibit [14C]sucrose accumulation by wheat or sorghum PSTM. N-N-Diallyl-2-chloroacetamide (CDAA) (1 mM) inhibited [14C]sucrose accumulation by sorghum but not by wheat PSTM. The inhibition of [14C]sucrose accumulation in sorghum PSTM by the membrane permeant CDAA was reversed by DTT. Sorghum growth was inhibited by <1 μM CDAA. Membrane permeant 2-chloroallyl diethyldithiocarbamate (CDEC) (0.1 mM) inhibited [14C]sucrose accumulation by PSTM of sorghum but not wheat. The inhibition of sucrose accumulation in sorghum PSTM by 0.1 mM CDEC was reversed by DDT.  相似文献   

6.
The influence of EPTC (S-ethyl dipropylthiocarbamate) on the hydrogenation of geranylgeranylchlorophyll (GG-Chl) to phytol-Chl was studied during the greening (6-, 12-, 18-, 24-, and 48-hr incandescent light exposure) of etiolated wheat [Triticum aestivum (L.) cv “Stacy”] and sorghum [Sorghum bicolor (L.) Moench cv “G 522DR”] seedlings grown in nutrient solution containing 14C-labeled sodium acetate. Chloroplast pigment synthesis occurred and small quantities of GG-Chl were found in both Chl?a and Chl?b. When wheat seedlings were greened for 48 hr in an EPTC concentration series (1 nM to 100 μM), geranylgeraniol (GG) content increased from 11% (control) to 60% (100 μM EPTC) of the isoprenoid alcohol esterified to chlorophyllide a, but Chl-b contained ≤1% GG-Chl at all concentrations of EPTC. Sorghum seedlings greened for 48 hr in the same EPTC concentration series contained about 3% GG (control) while 100 and 40% GG esterified to chlorophyllide a and chlorophyllide b, respectively, after 48 hr exposure to 100 μM EPTC. Thus, EPTC prevented hydrogenation of GG-Chl to phytol-Chl on the Chl molecule more in sorghum than in wheat.  相似文献   

7.
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   

8.
Enzymatically isolated leaf cells from navy beans (Phaseolus vulgaris L., cv. “Tuscola”) were used to study the effect of buthidazole (3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone) and tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea) on photosynthesis, protein, ribonucleic acid (RNA), and lipid synthesis. The incorporation of NaH14CO3, [14C]leucine, [14C]uracil, and [14C]acetic acid as substrates for the respective metabolic process was measured. Time-course and concentration studies included incubation periods of 30, 60, and 120 min and concentrations of 0.1, 1, 10, and 100 μM of both herbicides. Photosynthesis was very sensitive to both buthidazole and tebuthiuron and was inhibited in 30 min by 0.1 μM concentrations. RNA and lipid syntheses were inhibited 50 and 87%, respectively, by buthidazole and 42 and 64%, respectively, by tebuthiuron after 120 min at 100 μM concentration. Protein synthesis was not affected by any herbicide at any concentration or any exposure time period. The inhibitory effects of buthidazole and tebuthiuron on RNA and lipid syntheses may be involved in the ultimate herbicidal action of these herbicidal chemicals.  相似文献   

9.
[2-14C]Mevalonic acid incorporation into gibberellic acid precursors was measured in cell-free extracts from sorghum [Sorghum bicolor (L.) Moench var. G-522 DR] coleoptiles. 14C incorporation into ent-kaur-16-ene was inhibited ca. 90% by 10?7 to 10?4M metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide]. [14C]Geranylgeraniol (GG) content increased. [14C]Farnesol content was not altered and [14C]geraniol content decreased. Total 14C incorporation was decreased by metolachlor. In the safener [α-(cyanomethoximino)benacetonitrile]-treated sorghum seed coleoptile cell-free system, total 14C incorporation increased, [14C]kaurene and relative kaurence content increased 4× up to 105M metolachlor, and [14C]farnesol, and [14C]GG contents increased while relative farnesol and relative GG contents were not influenced by metolachlor. Thus, the inhibition of kaurene synthesis by metolachlor was reversed by the safener. Since the biosynthetic processes are mevalonic acid → geraniol → farnesol → GG → copalylol → kaurene, these data corroborate a proposed gibberellic acid biosynthesis inhibition between GG and kaurene as well as a partial blockage between mevalonic acid and geraniol. Thus, a portion of metolachlor-induced growth inhibitions of sorghum could be explicable on the basis of gibberellic acid biosynthesis inhibitions.  相似文献   

10.
Growth (14 days) of sorghum (Sorghum bicolor L. cv G522 DR) from seed planted in sand into which alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] was uniformly incorporated (0, 0.07, 0.14, 0.28, 0.56, 1.12, 2.24, or 4.48 kg/ha) was reduced by 0.14 kg/ha and severely inhibited (88%) by 0.56 kg/ha while cellular water cotent was not greatly influenced by 0.56 kg/ha. When added into the nutrient solution bathing the roots of 96-hr sorghum seedlings, alachlor (0, 0.0156, 0.0312, 0.0625, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, or 128 ppmw) was not lethal to 14-day-old sorghum at rates up to 32 ppmw (92% survival); however, shoot and root lengths were reduced 43 and 58%, respectively. Alachlor inhibition of sorghum growth appears to be closely associated with inhibition of cell enlargement; the coleoptile is the most susceptible stage of sorghum growth to alachlor. This situation closely resembles growth where gibberellic acid (GA) synthesis is inhibited. [2-14C]Mevalonic acid ([2-14C]MVA) incorporation into terpenoid GA precursors was evaluated using a cell-free enzyme system from etiolated sorghum coleoptiles. Alachlor did not inhibit total 14C incorporation but incorporation of 14C into kaurenol and sterols was decreased ca 80 and 75%, respectively, by 10?6M alachlor. Analyses for [14C]geranylgeraniol (GG), [14C]farnesol, and [14C]geraniol contents showed accumulation of [14C]farnesol and [14C]GG, and decreased [14C]geraniol. When seeds to which CGA-43089 [α-(cyanomethoximino)-benzacetonitrile] was applied 8 weeks prior to planting were substituted for untreated seeds, incorporation of [2-14C]MVA into [14C]kaurenol was increased by alachlor while [14C]GG and [14C]farnesol accumulated and [14C]geraniol was absent at 10?6M alachlor. Additionally, sterol content increased in “safened” systems but was still decreased by alachlor. These data demonstrate multiple sites of alachlor activity in the GA and terpenoid biosynthetic pathway.  相似文献   

11.
The effects of the herbicides hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] and chlorsulfuron (2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]benzenesulfonamide) on the metabolism of enzymatically isolated leaf cells from soybean [Glycine max (L.) Merr., cv. ‘Essex’] were examined. Photosynthesis, protein, ribonucleic acid (RNA), and lipid syntheses were assayed by the incorporation of specific radioactive substrates into the isolated soybean leaf cells. These specific substrates were NaH14CO3, [14C]leucine, [14C]uracil, and [14C]acetate, respectively. Time-course and concentration studies included incubation periods of 30, 60, and 120 min and concentrations of 0.1, 1, 10, and 100 μM of both herbicides. Photosynthesis was the most sensitive and first metabolic process inhibited by hexazinone. RNA and lipid syntheses were also inhibited significantly by hexazinone whereas the effect of this herbicide on protein synthesis was less. The most sensitive and first metabolic process inhibited by chlorsulfuron was lipid synthesis. Photosynthesis, RNA, and protein syntheses were affected significantly only by the highest concentration of this herbicide and longest exposure. Although these two herbicides may exert their herbicidal action by affecting other plant metabolic processes not examined in this study, hexazinone appears to be a strong photosynthetic inhibitor, while the herbicidal action of chlorsulfuron appeared to be related to its effects on lipid synthesis.  相似文献   

12.
Growth of Penicillium digitatum was inhibited after a 40-min incubation in a culture medium containing 0.5 mM sec-butylamine, and the dry weight of the hyphae was 50% of the control value after 180 min. Respiration of the hyphae was reduced 13% after a 20-min contact with 0.5 mM sec-butylamine but this treatment did not influence the uptake of amino acids, glucose, or phosphate nor intensify the efflux of 33P- or 14C-labeled metabolites from the cells. The syntheses of cell walls and total lipids were inhibited 20–30% after a 90-min incubation with sec-butylamine, and nucleic acid synthesis was reduced to about 50% of the control value at this time. sec-Butylamine inhibited the incorporation of labeled carbon from [14C]glucose into the protein fraction of the hyphae to a greater degree than 14C derived from labeled proline, lysine, or leucine. These observations suggested that sec-butylamine interfered primarily with the intermediary metabolism of glucose rather than inhibiting a later stage of macromolecule synthesis. Hyphae incubated with [14C]glucose and sec-butylamine accumulated pyruvic acid to a level seven times greater than in control hyphae. Furthermore, sec-butylamine strongly inhibited 14CO2 evolution from hyphae metabolizing [14C]pyruvate whereas CO2 derived from acetate or glucose after a 45-min incubation was only slightly reduced by sec-butylamine. These observations implicate pyruvate oxidation as the primary site of sec-butylamine action in young hyphae of P. digitatum.  相似文献   

13.
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   

14.
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   

15.
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   

16.
Due to the presence of an asymmetrically substituted C atom, dimethenamid [2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide], a recently introduced N-thienyl chloroacetamide herbicide, exists as two stereoisomers (S and R) having differing herbicidal activities as demonstrated with a selection of weeds and Lemna minor. The activity of the two isomers was investigated in greater detail with the green alga Scenedesmus acutus and compared to that of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide]. As with alachlor, the S isomer (5 μM ) strongly inhibited algal growth and fatty acid desaturation while the R isomer had no effect. In short-term experiments (up to 5·5 h), the S isomer and alachlor (100 μM ) inhibited [14C]acetate uptake and its incorporation into fatty acids in the same manner, while the R isomer did not. Incorporation of [14C]acetate into a non-lipid fraction of the algae was strongly inhibited by alachlor and the S isomer (100 μM ) and only slightly by the R isomer. A 50% inhibition of incorporation of [14C]oleic acid into the same non-lipid fraction was attained with less than 10-7 M of the S isomer while 10-5 M of the R form of dimethenamid achieved only a 40% inhibition. The same stereospecificity of the compound on growth, fatty acid desaturation, acetate uptake and oleic acid incorporation provides strong evidence that dimethenamid may act upon a primary, specific target in lipid metabolism. Furthermore, the comparable biological activities of dimethenamid and alachlor indicate that this target is common to both N-phenyl and N-thienyl chloroacetamide herbicides. © 1997 SCI.  相似文献   

17.
The herbicide diclofop-methyl caused an early and pronounced inhibition of the incorporation of [14C]acetate into leaf lipids of the sensitive plant species maize (Zea may L.), wild oat (Avena fatua L.), and barnyardgrass (Echinochloa crus-galli L.). With an EC50 value of approximately 10?7M inhibition was already apparent 0.5–4 hr after herbicide application. The fatty acid biosynthesis of tolerant bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), and soybean (Glycine max L.) was not affected, with one exception [wheat (Triticum aestivum L.) belongs to the more tolerant species]; the inhibition of fatty acid biosynthesis, however, was in the same order of magnitude as in sensitive plants. More detailed studies showed that in wheat a recovery from inhibition of fatty acid biosynthesis occurred. Four days after herbicide application (0.18 kg diclofop-methyl/ha) in wheat normal fatty acid biosynthesis was restored, whereas in sensitive maize a 60% inhibition was maintained over the whole experimental period (8 days). The results support the view that tolerance of wheat to diclofop-methyl is based on its inactivation in leaves, whereas the tolerance of dicotyledonous species may probably lie at the level of the site of action of diclofop-methyl. In experiments with intact leaves, the inhibition of fatty acid biosynthesis resulted in an enhanced flow of [14C]acetate into organic acids and amino acids. This effect, however, was not always reproducible in experiments with leaf pieces or isolated root tips.  相似文献   

18.
Accelerated degradation of vernolate, EPTC and butylate but not of cycloate was detected in soils from three locations in Israel which were treated annually with vernolate. Repeated application of EPTC to soils with and without a history of vernolate application, under laboratory conditions, resulted in a progressive increase in its rate of dissipation with each application. Accelerated degradation of EPTC was also rapidly induced by mixing small amounts (5%) of soil with a history of vernolate treatment with soil that had never received vernolate. Liberation of 14CO2 from [14C]EPTC was more rapid in vernolate-treated soils than in untreated soils, indicating a development of microbial populations in soil capable of rapidly degrading the EPTC. Degradation of [14C]EPTC was faster in soil previously cropped with maize than in non-cropped soil, but slower in soils cropped with cotton or peanuts.  相似文献   

19.
A Pseudomonas sp. which grew on 4-chloroaniline as a sole source of carbon and nitrogen was able to degrade 15% of 0.05 mM [14C]3,4-dichloroaniline to 14CO2 within 10 days in presence of 1.5 mM 4-chloroaniline. The catabolic enzymes which degraded 3,4-dichloroaniline to CO2 were inducible by 4-chloroaniline and by 3,4-dichloroaniline. However, their activity was much lower on 3,4-dichloroaniline than on 4-chloroaniline. The strain showed no significant growth on 3,4-dichloroaniline as a sole source of carbon and nitrogen. Soils supplemented with [ring-14C]propanil and the Pseudomonas sp. evolved 25–50% 14CO2 within 5 days. The 14CO2 evolution remained below 1% in absence of the Pseudomonas sp.  相似文献   

20.
The radiolabelling of isolaled Hedera helix L, (ivy) leaf cutieles was investigated after incorporation of [14C]acetate in foliar discs Cuticle radioactivity greatly decreased as leaf age inereased. The percentage of radioactivity incorporated in the upper cuticles decreased from 0.5% to 0.08% of the total radioactivity of foliar dises from young to old leaves. Cuticle radioactivity was recovered in waxes, cutin and polar components. It was considerably greater for waxes when expressed in terms of cuticle mass. The methodology was validated using S-ethyl-dipropylthiocarbamate (EPTC). The radioactivity incorporation in cuticles was significanly reduced when 1 m m EPTC was deposited as a 20-μL droplet on lo foliar dises 6 h before the incorporation of radiolabelled acetate. EPTC inhibited radioiabelling of wax and cutin fractions in the upper and lower cuticles. Some acetylenic fatty acid analogues inactivating lauric and oleic acid ω-hydroxylases, used as acid and sulphonate forms in the same experimental conditions as EPTC, induced no reduction in cuticle radiolabelling. An inhibitory effect was observed only for the acetylenic and the saturated C12 fatty acid analogues, used as tetrabu-tylammonium sulphonates, when applied directly in the liquid medium supporting foliar dises. Several assumptions are considered to explain the results of the present investigation.  相似文献   

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