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1.
Sugar beet plants were grown in the field, after in-furrow application of [14C]aldicarb (3 kg of aldicarb ha?1) at planting. Some plants (the growing plants) were harvested 99 days after sowing and the rest (the ripe plants) 196 days after sowing. The percentages of the weights of [14C]aldicarb equivalents (the total aldicarb plus aldicarb sulphoxide and sulphone, plus all the other metabolites of [14C]aldicarb which contain 14C, expressed as aldicarb equivalents) incorporated into the beet plants, relative to the weight applied to the soil, were 2.8 and 1.8, respectively for the growing and ripe plants. The concentrations of [14C]aldicarb equivalents (mg kg?1 fresh weight) in the growing and ripe plants, respectively were: blades of the external leaves, 3.16 and 0.93; blades of the internal leaves, 0.63 and 0.68; petioles of the external leaves, 0.51 and 0.26; petioles of the internal leaves, 0.15 and 0.05; crowns, 0.14 and 0.15; roots, 0.16 and 0.13. The proportions of the extractable aldicarb plus aldicarb sulphoxide and aldicarb sulphone determined by gas-liquid chromatography (expressed as aldicarb equivalents) relative to [14C]aldicarb equivalents, in the external and internal leaf blades of the growing beets, were 56 and 60%, respectively; these values declined to 25 and 19%, respectively in the ripe plants. The proportion was 21 % or less in all other parts of the growing and ripe plants.  相似文献   

2.
Sugar beet plants were grown in the field, after in-furrow application of [14C]- aldicarb (3 kg of aldicarb ha?1) at planting. The ripe sugar beet plants were harvested, and the roots were analysed. The roots were fractionated according to a procedure similar to the normal beet-sugar manufacturing process. Expressed as a proportion of the total radioactivity incorporated into the root, the pulp contained 29.7%, the lime cake 9.7%, the crystallised sugar 17.7% (which gave, with the radioactivity found in the sugar in the molasses, a total of 20.7% of the radioactivity in the total sugar), and the molasses, 42.9%. A part of the labelled carbon from the radio- active aldicarb and its metabolites had thus been metabolised and incorporated into sugar molecules. Except for the radioactivity in the sugar and in the lime cake from the processing, the proportion of radioactive non-conjugated organosoluble compounds was very low (2.6%), and perhaps partially corresponded to the very low amount of aldoxycarb (aldicarb sulphone) in the root (less than 0.001 mg of [14C]-aldicarb equivalents kg?1 fresh weight). Hydrolysis of the molasses yielded free radioactive 2-methyl-2-(methylsulphinyl)propan-1-ol (3.1%), 2-mesyl-2-methyl-propan-I-ol (8.9%) and 2-mesyl-2-methylpropionic acid (12.0%) which had been conjugated to plant constituents in the root. The corresponding concentrations (expressed as mg of [14C]aldicarb equivalents kg?1 fresh weight of root) were 0.004, 0.011, and 0.016, respectively. No aldicarb, aldicarb sulphoxide or aldoxycarb (nor the corresponding nitrile, generated from aldicarb during the fractionation procedure) was liberated by the hydrolysis, indicating the absence of conjugates of these compounds in the root.  相似文献   

3.
The residues of aldicarb and of its main metabolites (aldoxycarb, 2-mesyl-2-methylpropionitrile, and 2-mesyl-2-methylpropan-1-ol) were measured, by a gas-liquid chromatographic procedure, in the leaves of ripe sugar beet plants from cultures made by several farmers. The sugar beet plants had been grown in normal fields and treated at sowing with aldicarb at the usual rate of 1 kg ha?1 in the form of ‘Temik’, the commercial formulation of aldicarb which contains 10% by weight of aldicarb. The samples of sugar beet plants were taken from three fields of different soil types. The residue concentrations, ranged in order of soil type, were: sandy loam > silt loam > clay.  相似文献   

4.
Imazapyr absorption, translocation, root release and metabolism were examined in leafy spurge (Euphorbia esula L.). Leafy spurge plants were propagated from root cuttings and [14C]imazapyr was applied to growth-chambergrown plants in a water + 28% urea ammonium nitrate + nonionic surfactant solution (98.75 + 1 + 0.25 by volume). Plants were harvested two and eight days after herbicide treatment (DAT) and divided into: treated leaf, stem and leaves above treated leaf, stem and leaves below the treated leaf, crown, root, dormant and elongated adventitious shoot buds. Imazapyr absorption increased from 62.5% 2 DAT to 80.0% 8 DAT. Herbicide translocation out of the treated leaf and accumulation in roots and adventitious shoot buds was apparent 2 DAT. By the end of the eight-day translocation period only 14% of applied 14C remained in the treated leaf, while 17% had translocated into the root system. Elongated and dormant adventitious shoot buds accumulated 3.2- and 1.8-fold more 14C, respectively, 8 DAT than did root tissue based on Bq g?1 dry weight. Root release of 14C was evident 2 DAT, and by 8 DAT 19.4% of the 14C reaching the root system was released into the rooting medium. There was no metabolism of imazapyr in crown, root or adventitious shoot buds 2 DAT; however, imazapyr metabolism was evident in the treated leaf 2 and 8 DAT. Imazapyr phytotoxicity to leafy spurge appears to result from high imazapyr absorption, translocation to underground meristematic areas (roots and adventitious shoot buds), and a slow rate of metabolism.  相似文献   

5.
The deamination of metribuzin was studied in vitro in peroxisomes isolated from the leaves of soybean cultivars which were either metribuzin tolerant, intermediate, or sensitive. The deamination rate observed with peroxisomes from tolerant leaves was about twice the rate observed with peroxisomes from sensitive leaves. The intermediate group was also intermediate with respect to the in-vitro deamination rate. Tolerant and sensitive intact soybean plants were pulse-labeled with [14C]metribuzin via the roots for 5 h. The extractable radioactivity in roots, stems and leaves was measured and separated into metabolites after the 5 h pulse and after an additional 24 h growth in water. The level of DA (deaminated metribuzin) was always significantly higher in the stems and leaves of tolerant soybean plants (4.8–10.0% of the extracted radioactivity) than in sensitive stems and leaves (1.8–2.9%). Conjugates were rapidly formed in tolerant as well as in sensitive soybean tissues. More conjugates were found in the tolerant cultivars, especially after the 5 + 24 h incubation time. Labeled [14C]DA fed to soybean plants via the roots was conjugated two to four times faster than [14C]metribuzin. Tolerant soybean tissue conjugated [14C] DA two to three times faster than sensitive tissue. The results are interpreted as showing that, in tolerant soybean plants, metribuzin is metabolized via deamination and subsequent conjugation, in addition to the well-known direct conjugation of metribuzin parent compound.  相似文献   

6.
The distribution and degradation of chlormequat chloride (2-chloro 1,2-14C ethyltrimethylammonium chloride) was determined after uptake by the roots of summer wheat seedlings. This plant regulator was readily translocated from the roots to the above ground parts and converted into choline. Choline was further metabolized to betaine which upon demethylation yielded finally glycine and serine. Both amino acids were incorporated into a protein fraction.The occurrence of radioactively labeled glycine and serine in the amino acid pool and the evolution of 14CO2 from chlormequat treated plants indicated that serine was formed from glycine under the release of 14CO2 during photorespiration.One week after the uptake period 82% of 14C chlormequat taken up by the roots was recovered as the parent compound or as breakdown products in wheat plants. In addition 5% of the amount taken up by the roots was released as 14CO2 by the leaves.Fifty per cent of the total amount of chlormequat originally present in roots and leaves was already metabolized after 7.5 days. No evidence has been obtained for the presence of unchanged chlormequat or an unknown metabolite in the nucleic acid or protein fraction.  相似文献   

7.
The carbamoyloxime pesticides methomyl, oxamyl and aldicarb, together with the oxidation products of aldicarb, are known to break down much more rapidly in certain anaerobic subsoils than in the aerobic topsoils from the same site. Ferrous ions have now been shown to be involved in this reaction. Oxamyl was degraded in aqueous solutions at 30°C containing 250 μg ml?1 Fe2+ with a half-life of about 10 h, independent of pH in the range of 5.65–7.66; the observed products of this reaction were N,N-dimethyl-l-cyanoformamide and methanethiol. These same products, rather than the oximino hydrolysis product observed from degradation in aerobic soils, were rapidly and quantitatively formed from oxamyl in suspensions of anaerobic reduced subsoils (Fe2+ concentration 27–41 μg ml?1 soil water), but oxamyl was rather stable in water-saturated Vredepeel subsoil (Fe2+ concentration 0.65 μg ml?1) in which the redox potential was much higher. Methomyl behaved similarly. The rates of reaction in the suspensions of anaerobic subsoils were greater than expected from the concentrations of Fe2+ in the soil water, but most of the Fe2+ present in soil was bound to the soil particles by cation exchange and this bound Fe2+ may have participated. Breakdown of aldicarb was accelerated both in solutions of Fe2+ and in the suspensions of anaerobic reduced subsoils, though the rate enhancement was less than observed with methomyl and oxamyl; 2-methyl-2-methylthiopropionitrile and 2-methyl-2-methylthiopropionaldehyde were the observed products from aldicarb in anaerobic soil but only the former was produced in Fe2+ solutions; the corresponding nitriles and aldehydes were also yielded by aldicarb sulphoxide and aldicarb sulphone in the anaerobic, reduced subsoils.  相似文献   

8.
The correlation between intensity of lipid peroxidation and changes in antioxidant capacity of sugar beet plants (cv. ‘Drena’) infected with Rhizoctonia solani Kühn isolate (AG 2-2 IIIB group) was studied. Successful inoculation was confirmed by the presence of infection cushions in a cross section of leaf petioles. On the 7th day of the experiment, phenylalanine ammonia-lyase (PAL; EC. 4.3.1.5) activity was in negative correlation with intensified lipid peroxidation process in leaves of sugar beet plants (r= –0 .99). Also, in leaves and roots of inoculated sugar beet plants, total flavonoids content (35% and 20%, respectively) and 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity (80% and 55%, respectively) were significantly reduced. Necrotic processes resulting from R. solani infection of sugar beet plants was followed by induction of plant phenolics metabolism; however, antioxidant capacity of these plants was reduced.  相似文献   

9.
The shoots of barley plants root-treated with [2,5-14C]piperazine were analysed 30 days after treatment. Methanol extraction left a solid residue which contained 31.9% of 14C (all percentages refer to the total of 14C incorporated into the shoots); further extraction with acidified methanol and dimethyl sulphoxide dissolved respectively 3.2% and 5.8% of 14C. The initial methanol extract contained radioactive piperazine (16.8%), iminodiacetic acid (8.6%), glycine (15.4%), oxalic acid (7.2%), and un-identified compounds (20.1%). In barley, piperazine is the product of the most advanced metabolism so far identified of the fungicide triforine, 1,4-bis(2,2,2-trichloro-1-formamidoethyl)piperazine; the results obtained here show that piperazine is certainly not the end-product of the metabolism of triforine in barley.  相似文献   

10.
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   

11.
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   

12.
The transformation of aldicarb sulfoxide and aldicarb sulfone was studied in incubations with water-saturated subsoils under simulated field conditions at 10°C. The subsoils were collected at four locations from beneath the water table at a depth of 2.5 to 3.5 m. In three of the subsoils, the half-life of sulfoxide, incubated at concentrations of 0.14-0.17 mg litre?1, ranged from 0.7 to 2.8 years. At higher concentrations (8-13 mg litre?1), its half-life ranged from 3.4 to 6.4 years. At the lower concentration, a large fraction of sulfoxide was transformed into sulfone. The rates of transformation of the sulfone at the lower concentration in the three subsoils corresponded to half-lives of 3.3 to 8.1 years, but in only one subsoil was a significant transformation rate (half-life 6.7 years) measured at the higher concentration during the 2.3-year incubation period. The half-lives at the lower concentrations were more like those in field studies, and perhaps would still underestimate transformation rates under field conditions. After a year, 2.5-15% of the higher sulfoxide and sulfone doses had been trapped as [14C] carbon dioxide. In the fourth subsoil, with more anaerobic conditions, the half-life of sulfoxide at both concentrations was less than 0.02 year and that of sulfone was about 0.04 year. Four or five radio-labelled transformation products could be traced in this subsoil and about half of the dose of both compounds was trapped as [14C] carbon dioxide.  相似文献   

13.
Cotton was grown in loess soil, in rows 1 m apart, and drip-lines were placed in the center of every second space between rows at a distance of 50 cm from the plants. Aldicarb was applied as granules (containing 15% a.i.) to the field on two dates (mid-June and mid-July) and incorporated into the soil(a) 25 cm from the plants,i.e., equidistant from the plants and the drip-lines, on both sides of the drip-lines; and(b) 50 cm from the plants,i.e., in the center of the spaçe between the rows, near the drip-line. Measurements of mortality ofBemisia tabaci larvae, and of the accumulation of aldicarb from the late (mid-July) treatment showed that best control of the pest and the highest aldicarb residues were obtained with the late treatment. The pest control effectiveness was found to depend on both date and location of aldicarb application. Early treatment (mid-June) was more effective if applied close (25 cm distance) to the plant stems, whereas late treatment (mid-July) was more effective if applied at a distance of 50 cm from the plant stems.  相似文献   

14.
以黑果枸杞的叶片和茎段为外植体,采用MS为基本培养基,研究激素对经历愈伤组织诱导、丛生芽诱导以及叶片直接诱导小植株再生途径的影响。实验结果表明,诱导茎段、叶片形成愈伤组织的适宜培养基分别为MS+2,4-D0.3 mg·L~(-1)、MS+2,4-D0.4 mg·L~(-1),其诱导率均为100%;诱导茎段、愈伤组织分化形成丛生芽的适宜培养基分别为MS+6-BA0.2 mg·L~(-1)+KT0.1 mg·L~(-1)、MS+6-BA0.5 mg·L~(-1),而愈伤组织分化出的丛生芽均发生玻璃化现象,其增殖系数分别为32.3倍、47.1倍;诱导叶片分化形成植株的适宜培养基为MS+NAA0.01 mg·L~(-1),其再生植株诱导率为33.3%。结论:黑果枸杞再生能力强,以上途径均能形成再生植株,其最佳的离体繁殖途径为茎段诱导丛生芽形成再生植株。  相似文献   

15.
Experiments were conducted in a growth cabinet to investigate the absorption and translocation of 14C-3, 6-dichloropicolinic acid by Cirsium arvense (L.) Scop. (Canada thistle, creeping thistle), a sensitive species. Applications were made, either to the middle four leaves of 12-cm-tall vegetative plants grown under low (40%) and/or high (>95%) relative humidity (r.h.), or to four upper or lower leaves of 30-cm-tall flowering plants grown under low r.h. Following application to vegetative plants, absorption and translocation of 14C-3,6-dichloropicolinic acid was rapid and was approximately doubled by high r.h. High r.h. increased the amount of radioactivity retained by the treated leaves or translocated to the shoots but did not affect greatly the amount retained in the roots. The herbicide was highly mobile, with over half of that absorbed, translocated out of the treated leaves after two days. The apex accumulated most of the radioactivity, while approximately 8% was recovered from the roots. The absorption and translocation patterns were similar to those reported in the literature for picloram in C. arvense. Absorption of 3,6-dichloropicolinic acid was greater in vegetative than in flowering C. arvense plants, and placement of herbicide on lower leaves tended to decrease the amount of radioactivity recovered from shoot apex and increase the amount recovered from the roots. Approximately 15% of the applied radioactivity could not be recovered from treated plants by 2 days after treatment.  相似文献   

16.
A study was made of the accumulation of aldicarb, ethiofencarb and dimethoate in citrus leaves and fruit; the toxicity of these insecticides to the spirea aphid (Aphis citricola Van der Goot) was also studied. The effectiveness of the treatments was affected mainly by the rate of accumulation of the toxicant in the leaves. At 18 g a.i. per tree, the greatest residues found in the leaves were 106, 12.2 and 1.3 μg 8?1 fresh weight for aldicarb, ethiofencarb and dimethoate, respectively. The concentration in mature leaves was very similar to that in young leaves. The residue levels in the mature fruits were much lower than in the leaves. The main components of the residues in the leaves were aldicarb sulphoxide [2-methyl-2-(methylsulphinyl)- propionaldehyde O-methylcarbamoyloxime], dimethoate, omethoate and ethiofencarb sulphoxide [2-(ethylsulphinylmethyl)phenyl methylcarbamate]. A laboratory study with synthetic diets showed similar toxicity for all three insecticides, whereas in detached leaves, or when taken up by citrus trees, ethiofencarb was the least toxic to the aphids.  相似文献   

17.
The metabolism of the pyrethroid insecticide fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] ( I ), and of its most insecticidal (αS,2S) isomer ( II ), has been examined in cabbage plants grown and treated under laboratory conditions with [14C]chlorophenyl- and [ring-14C]benzyllabelled preparations of the two compounds. Both insecticides disappeared from the treated leaves with similar half-lives of approximately 12–14 days; they underwent ester cleavage to a significant extent, together with some hydroxylation at the 2- or 4-position of the phenoxy ring, and hydrolysis of the nitrile group to amide and carboxyl groups. Most of the carboxylic acids and phenols thus produced occurred as glycoside conjugates. In separate experiments, the uptake and metabolism of 2-(4-chlorophenyl)-3-methylbutyric acid ( X ), the acidic half of the molecule, were examined in the laboratory, using abscised leaves of kidney bean, cabbage, cotton, cucumber and tomato plants. The acid X was found to be readily converted, mainly into glucose and 6-O-malonylglucose esters in kidney bean, cabbage and cucumber plants, into glucosylxylose, sophorose and gentiobiose esters in cotton, and into two types of triglucose esters with differing isomerism in tomato. One of the acetyl derivatives of the trisaccharide conjugates was identical with the synthetic deca-acetyl derivative of the [1 → 6]-triglucose ester.  相似文献   

18.
The uptake and translocation of [14C]asulam (methyl 4-aminophenyl-sulphonylcarbamate), [14C]aminotriazole (1-H-1,2,4-triazol-3-ylamine) and [14C]glyphosate (N-(phosphonomethyl)glycine) were assessed in Equisetum arvense L. (field horsetail), a weed of mainly horticultural situations. Under controlled-environment conditions, 21°C day/18°C night and 70% r. h., the test herbicides were applied to 2-month-old and 2-year-old plants. Seven days following the application of 0.07-0.09 °Ci (1.14mg) of the test herbicides to young E. arvense, the accumulation of 14C-label (as percentage of applied radioactivity) in the treated shoots, untreated apical and basal shoots was as follows: [14C]asulam, 13.2, 0.18 and 1.02%; [14C] aminotriazole, 67.2, 3.65 and 1-91%; [14C]glyphosate, 35.9, 0.06 and 0.11%. The equivalent mean values for the accumulation of 14C-label in 2-year-old E. arvense were [14C]asulam, 12.0, 1-15 and 1.74%; [14C]aminotriazole, 58.6, 9.44 and 4.12%; [14C]glyphosate, 33.1, 0.79 and 2.32%. In the latter experiment, test plants received 0.25-0.30 °Ci (4mg) of herbicide, they were assessed after a 14-day period and the experiment was carried out at 3-week intervals between 2 June and 25 August on outdoor-grown plants. Irrespective of test herbicide or time of application, very low levels of 14C-label accumulated in the rhizome system. Only 0.2% of the applied radioactivity was recovered in 2-year-old plants and 0.4% in 2-month-old plants. In the young plants [14C]asulam accumulated greater amounts and concentrations of 14C-label in the rhizome apices and nodes than [14C]aminotriazole or [14C]glyphosate treatments. Inadequate control of E. arvense under field conditions may be due to limited basipetal translocation and accumulation of the test herbicides in the rhizome apices and nodes.  相似文献   

19.
Uptake, movement, and metabolism of unformulated ioxynil and bromoxynil salts were investigated in Matricaria inodora and Viola arvensis. The morphology of these two species did not give rise to different spray retention and contact angles. After 7 days, uptake of [14C]ioxynil-Na reached 8.26% of applied 14C activity in M. inodora and 16.77% of that in V. arvensis compared with 1.54 and 3.83%, respectively, for [14C]bromoxynil-K. Over 98% of the 14C activity detected in the plant after 7 days remained in the treated leaves of V. arvensis following [14C]ioxynil-Na treatment. However, 8.7% of the 14C activity detected in [14C]ioxynil-Na-treated M. inodora was recovered from the apex and developing leaves reflecting a greater translocation. [14C]Bromoxynil-K was more mobile in both species and after 7 days 87.5 and 91.39% were detected in the treated leaves of M. inodora and V. arvensis, respectively. In both species the majority of translocated 14C activity was recovered from the apex and developing leaves. Up to 20% of the applied [14C]ioxynil-Na and [14C]bromoxynil-K was not detected within the treated plant. Extraction of treated plants revealed no detectable metabolic breakdown of ioxynil-Na to halogenated derivatives in either species. However, metabolic breakdown of bromoxynil-K was apparent in V. arvensis. No significant root exudation was detected when [14C]ioxynil-Na and [14C]bromoxynil-K were applied to hydroponically grown S. media and V. arvensis. Losses of 14C activity were due to herbicide volatility or degradation to volatile products on the leaf surface.  相似文献   

20.
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   

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