The metabolism of cypermethrin in plants: The conjugation of the cyclopropyl moiety

The metabolism of the pyrethroid insecticide cypermethrin ([S,R,]-α-cyano-3-phenoxybenzyl-(1R,1S,cis,trans)-2,2-dimethyl-3-(2′,2′-dichlorovinyl)cyclopropane carboxylate), I, has been examined in lettuce plants grown and treated twice under outdoor conditions with ¹⁴C-cyclopropyllabeled material. The application rate at each treatment was equivalent to 0.3 kg/ha. At harvest, 21 days after the last application, the plants contained mainly unchanged cypermethrin (33% of the total radiolabel present) and polar materials (54%) which were shown to be conjugates of trans-2(2′,2′-dichlorovinyl)-3,3-dimethylcyclopropane carboxylic acid (II). One of these was identified as the β,d-glucopyranose ester. In separate experiments the uptake and metabolism of the acid (II) in cotton leaves were examined in the laboratory and the acid was shown to be readily converted into a mixture of the β,d-glucopyranose ester, an acidic derivative of this, and disaccharide derivatives including the glucosylarabinose ester and the glycosylxylose ester. Subsequently, cotton leaves were exposed to solutions of these individual conjugates, and interconversions between these metabolites were observed.     

New conjugated metabolites of 3-phenoxybenzoic acid in plants

The metabolism of 3-phenoxybenzoic acid, a common plant metabolite of deltamethrin, cypermethrin and fenvalerate, has been studied in abscised leaves of cabbage, cotton, cucumber, kidney bean and tomato plants. The [¹⁴C]-acid was readily converted into more polar conjugates by esterification with glucose, 6-O-malonylglucose, gentiobiose, cellobiose, glucosylxylose and two types of triglucose with different isomerism. Other metabolites identified were the glucosyl ether of 3-(4-hydroxyphenoxy)benzoic acid, and a 3-(2-hydroxyphenoxy)benzoic acid derivative with a total of two molar equivalents of glucose linked to the carboxyl and phenolic -OH groups. The conjugation pathways were somewhat plant-specific. The glucosylxylose ester was found only in cotton, and the cellobiose and triglucose esters were found only in tomato. All of the conjugates except the glucose and glucosylxylose esters were plant metabolites that had not been identified previously. Furthermore, this is the first report to show the presence of cellobiose and triglucose conjugates in plants. However, neither of the acetyl derivatives of the [¹⁴C]-triglucoside was identical with the synthetic deca-acetyl derivative of [1→6]-triglucoside.     

The metabolism of fenvalerate in plants: The conjugation of the acid moiety

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.     

The metabolism of 3-phenoxybenzyl alcohol,a pyrethroid metabolite,in plants

The metabolism and conjugation of 3-phenoxybenzyl alcohol, a plant metabolite of permethrin and cypermethrin, have been examined in abscised cotton leaves. Mature cotton leaves were treated by petiole uptake of an aqueous solution of [α-¹⁴C]-3-phenoxybenzyl alcohol. Initially there was rapid formation of a compound identified as the glucosyl 3-phenoxybenzyl ether. Subsequently more polar compounds were formed and these were shown to be disaccharide conjugates of the alcohol with glucose and pentose sugars. The alcohol and its mono- and disaccharide conjugates were shown to undergo interconversion in cotton leaves, and evidence was obtained from experiments with [¹⁴C]glucose for the ready exchange of the glucose units on the conjugates with free glucose in the leaves. No larger carbohydrate conjugates of 3-phenoxybenzyl alcohol were detected under the conditions used.     

Metabolic fate of methazole in purple and yellow nutsedge

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.     

Uptake,distribution and metabolic fate of 3H-triforine in plants .I. Short-term experiments

Most of the label, present in the roots of bean, tomato and barley seedlings after short-term root-treatment with ³H-triforine, appeared only weakly adsorbed on to the root tissue and was desorbed after transplanting in fungicide-free soil. Label taken up accumulated almost exclusively in the leaves present at the time of treatment; all leaves expanding after termination of the treatment remained virtually devoid of radioactivity. In “adult” plants label was usually present in a concentration gradient from roots to youngest leaves; in tomato plants, however, distribution of label was rather irregular. Time-course studies with bean and barley plants revealed that the aerial parts were gradually supplied with label, from old to youngest leaves, the maximum relative accumulation of radioactivity slowly moving acropetally. Under the experimental conditions chosen, triforine was converted nearly quantitatively to one metabolite, which almost certainly is different from any known non-enzymic breakdown product of the fungicide.     

ZUM METABOLISMUS VON FLURENOL-n-BUTYLESTER IN HÖHEREN PFLANZEN*

Summary. Following application of ¹⁴C-labelled flurenol-n-butyl ester (9-hydroxyfluorenc-9-carboxylic acid, n-butyl ester) to the leaves of Phaseolus vulgaris, the metabolism of this systemic growth-regulator was examined. The structure of two isomeric β-glucosides was elucidated, and four other polar metabolites were isolated and characterized. Métabolisme duflurénol-n-butyl ester dans les plantes supérieures     

Metabolism of cisanilide (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide) by excised leaves and cell suspension cultures of carrot and cotton

Major methanol-soluble metabolites of cisanilide (cis-2,5-dimethyl-1-pyrrolidinecarboxanilide) were isolated from excised, pulse-treated carrot and cotton leaves. They were identified as O-glucoside conjugates of primary aryl and alkyl oxidation products, 2,5-dimethyl-1-pyrrolidine-4-hydroxycarboxanilide and 2,5-dimethyl-3-hydroxy-1-pyrrolidinecarboxanilide. Comparative studies with carrot and cotton cell cultures showed similar initial pathways of cisanilide metabolism. Time-course studies with [¹⁴C-pyrrolidine]- and [¹⁴C-phenyl]cisanilide showed little, if any, cleavage of the herbicide molecule in either excised leaves or cell cultures. Quantitative differences in the metabolism of cisanilide by cell cultures and excised leaves included; a reduced capacity of cell cultures to form secondary glycoside conjugates and an increased ability of cell cultures to form methanol-insoluble residues.     

Metabolic fate of bioxone in cotton

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.     

Metribuzin metabolism in tomato: Isolation and identification of N-glucoside conjugates

Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-1,2,4-triazin-5(4H)-one] metabolism was studied in tomato (Lycopersicon esculentum Mill. “Sheyenne”). Pulse-treatment studies with seedlings and excised leaves showed that [5-¹⁴C]metribuzin was rapidly absorbed, translocated (acropetal), and metabolized to more polar products. Foliar tissues of 19-day-old seedlings metabolized 96% of the root-absorbed [¹⁴C]metribuzin in 120 hr. Excised mature leaves metabolized 85–90% of the petiole-absorbed [¹⁴C]metrubuzin in 48 hr. Polar metabolites were isolated by solvent partitioning, and purified by adsorption, thin-layer, and high-performance liquid chromatography. A minor intermediate metabolite (I) was identified as the polar β-d-(N-glucoside) conjugate of metribuzin. The biosynthesis of (I) was demonstrated with a partially purified UDP-glucose: metribuzin N-glucosyltransferase from tomato leaves. A possible correlation between foliar UDP-glucose: metribuzin N-glucosyltransferase activity levels and differences in the tolerance of selected tomato seedling cultivars to metribuzin was suggested. The major polar metabolite (II) was identified as the malonyl β-d-(N-glucoside) conjugate of metribuzin.     

Control ofRhizoctonia solani andSclerotium rolfsii in the greenhouse using endophyticBacillus spp.

Isolates of different endophytic bacteria were recovered from surface-disinfected seeds obtained from commercial companies, plants in the field and tissue culture. The bacteria were isolated from seeds after stringent surfacedisinfection.Pseudomonas fluorescens (isolate no. 14) from bean inhibited growth of all fungi tested and was fluorescent on King B medium.Bacillus cereus fromSinapis (isolate no. 65) inhibited growth ofRhizoctonia solani, Pythium ultimum andSclerotium rolfsii and also exhibited chitinase activity.Bacillus subtilis from onion tissue culture (isolate no. 72) inhibitedR. solani andP. ultimum growth.B. cereus from cauliflower (isolate no. 78) inhibited growth ofR. solani. B. pumilus from sunflower (isolate no. 85) inhibited growth ofR. solani andS. rolfsii. B. cereus (isolate no. 65) was introduced into cotton, and by using radioactive labelling we found that it was present for 16 days in the root-stem junction. It is most likely that these bacteria were still found 72 days after their introduction in the root and stem, at levels of 2.8·10⁵ and 5·10⁴ cfu g^–1 fresh weight, respectively, when selective medium was used. There was no difference between control and treated plants in their height or in the fresh weight of roots, stems and leaves.When cotton seedlings were inoculated withB. cereus (isolate no. 65),B. subtilis (isolate no. 72) orB. pumilus (isolate no. 85), disease incidence caused byRhizoctonia solani was reduced in the greenhouse by 51%, 46% and 56%, respectively. In bean seedlings inoculated withB. subtilis (isolate no. 72),B. cereus (isolate no. 78) orB. pumilus (isolate no. 65), disease incidence caused bySclerotium rolfsii was reduced by 72%, 79% and 26%, respectively, as compared to control. In both cotton and bean seedlings, these endophytes reduced the disease index more than 50%. These results indicate that endophytic bacteria can survive inside cotton plants and are efficient agents for biological control against plant pathogens under greenhouse conditions.     

棉花叶片茸毛性状与绿盲蝽抗性的关系

为明确棉花叶片茸毛性状与其对绿盲蝽抗性的关系,于2008-2009年连续两年系统研究了不同供试棉花品种(系)对绿盲蝽的抗性水平,并在室内测定了棉花中脉和叶片上茸毛的类型、密度和长度.结果表明,不同棉花品种(系)对绿盲蝽的抗性水平存在差异;且不同棉花品种(系)叶片各类型茸毛密度和茸毛长度分别表现显著差异(P<0.05);叶片茸毛密度与棉花对绿盲蝽的抗性呈显著负相关(y=3.5482-0.0007x1-0.0089x2,R2=0.5741,P=0.0007),叶片茸毛类型和茸毛长度与棉花对绿盲蝽的抗性没有显著相关性.选育叶片无毛或少毛的棉花品种(系)可用于棉花绿盲蝽的治理.     

入侵害虫草地贪夜蛾取食七种食物的种群生命表

为阐明入侵害虫草地贪夜蛾Spodoptera frugiperda对我国不同农作物的适应性,利用年龄-阶段两性种群生命表技术研究取食玉米粒以及玉米、花生、棉花、大豆、高粱和谷子叶片等7种不同食物对草地贪夜蛾生长发育与繁殖的影响。结果表明,不同食物显著影响草地贪夜蛾种群。整个成虫前期从长到短依次为取食棉花叶>取食大豆叶>取食高粱叶>取食花生叶>取食谷子叶>取食玉米叶>取食玉米粒,取食玉米粒要比取食棉花叶的时间缩短27.95 d。雌雄成虫寿命均以取食玉米粒和高粱叶的最长,以取食玉米叶的较短,且取食棉花叶的雄成虫寿命仅有3.00 d。产卵量以取食玉米粒的最多,为619.27粒,是取食其他食物的6.00倍～61.25倍。取食玉米叶的草地贪夜蛾初孵幼虫个体完成幼虫、蛹和成虫阶段的概率均较高,分别为95.38%、78.46%和78.46%,而取食棉花叶的最低,分别为37.29%、20.34%和20.34%。草地贪夜蛾取食玉米粒的净增值率、内禀增长率、周限增长率均最高,分别为105.59、0.12 d-1、1.13 d-1,平均世代周期最短,为36.91 d,而取...     

Effect of inoculum composition on infection of French bean leaves by conidia of Botrytis cinerea

Inoculation of leaves of French bean (Phaseolus vulgaris) with sprays or small drops of a suspension of conidia ofBotrytis cinerea gave rise to spreading lesions, lesions remaining restricted in size or to no visible necrosis. The type of reaction depended on the composition of the inoculum. In studies with drop inoculations with buffered inocula some of the factors involved were analyzed. The formation of spreading lesions depended on pH, type and molarity of the buffer, presence of glucose, and concentration of conidia in the inoculum. If the phosphate buffer used in most of the inocula was replaced by monobasic phosphate, similar results were obtained. The reactions were not influenced by the proportion of K⁺ or Na⁺ ions in the phosphate buffer. Inoculations with conidia suspended in a solution of 0.067 M phosphate buffer (pH 5.0) or monobasic phosphate and 0.11 M glucose always evoked a susceptible reaction, i. e. the formation of spreading lesions.     

Factors affecting benfuresate activity against purple nutsedge (Cyperus rotundas L.)

Benfuresate (2-3-dihydro-3,3-dimethylbenzofu-ran-5-yl ethanesulfonate) is a selective herbicide for the control of purple nutsedge in cotton. Under outdoor conditions, purple nutsedge was sensitive to benfuresate incorporated in soil up to eight days after initiation of shoot sprouting from the tuber. Older seedlings recovered from the damage. During the period of susceptibility to benfuresate, young shoots more sensitive than the roots. Under controlled environmental conditions, benfuresate applied directly to apical buds developing from the tuber caused severe damage to the treated bud and induced abrupt development of axillary buds. Negligible amounts of the applied herbicide were translocated from the treated part to the other buds and roots. Application of the herbicide to fully developed leaves had no effect, probably because of its rapid metabolism and low basipetal mobility. Its relatively high volatility may also contribute to its low foliar post-emergence activity. Tubers also absorbed herbicide vapours. Root uptake of ¹⁴C-benfuresate resulted in a rapid accumulation of ¹⁴C in the shoot, which had no effect on the purple nutsedge plant, regardless of concentration. The herbicide is rapidly converted, mainly to a non-phytotoxic polar product. These results may explain the high sensitivity of the weed to benfuresate at early growth stages, and the lack of sensitivity in mature plants.     

Metabolism of isopropyl carbanilate by soybean plants

Root-treated soybean plants absorb, translocate, and metabolize isopropyl carbanilatephenyl-¹⁴C (propham-¹⁴C). After a 3-day treatment period and removal of the exogenous ¹⁴C treating solution, only small concentrations of ¹⁴C-labeled materials were found in newly emerging tissues. A measurable concentration of radiocarbon was found in the seed pods, but the fruit tissues were shown to be free of any dectable ¹⁴C-labeling. Three days after removal of the exogenous propham-¹⁴C, the parent herbicide was completely metabolized by all tissues. Polar products and nonextractable residues were found in roots, stems, and leaves after a 3-day treatment period. The polar metabolites were not translocated once they were formed in either the roots or shoots.Conjugated polar metabolites were isolated, partially purified, and the prophamphenyl-¹⁴C moiety characterized. The aglycone moiety of the polar metabolites was liberated either by methanol-HCl solvolysis or by enzyme hydrolysis with β-glucosidase or hesperidinase. The aglycone from all three procedures was derivatized, purified and characterized by NMR, ir, and mass spectral analysis. The only aglycone was the derivative of isopropyl-2-hydroxycarbanilate which was at least in part conjugated as a glycoside.     

The distribution and degradation of chlormequat in wheat plants

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.     

Comparative uptake and metabolism of methazole in prickly sida and cotton

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.     

Greenhouse and field‐based studies on the distribution of dimethoate in cotton and its effect on Tetranychus urticae by drip irrigation

BACKGROUND

The two‐spotted spider mite, Tetranychus urticae Koch is an important pest of cotton. We investigated the efficacy of dimethoate in controlling T. urticae by drip irrigation. Greenhouse and field experiments were carried out to determine the efficacy of dimethoate to T. urticae and the absorption and distribution of dimethoate in cotton.

RESULTS

Greenhouse results showed that cotton leaves received higher amounts of dimethoate compared with cotton roots and stems, with higher amounts in young leaves compared with old leaves and cotyledon having the lowest amounts among leaves. Field results showed the efficacy of dimethoate to T. urticae by drip irrigation varied by volume of dripping water, soil pH and dimethoate dosage. Dimethoate applied at 3.00 kg ha^–1 with 200 m³ ha^–1 water at weak acidic soil pH (5.70–6.70) through drip irrigation can obtain satisfactory control efficacy (81.49%, 7 days) to T. urticae, without negatively impacting on its natural enemy Neoseiulus cucumeris. The residue of dimethoate in all cotton seed samples were not detectable.

CONCLUSIONS

These results demonstrate the effectiveness of applying dimethoate by drip irrigation for control of T. urticae on cotton. This knowledge could aid in the applicability of dimethoate by drip irrigation for field management of T. urticae populations. © 2017 Society of Chemical Industry     

不同供氮水平对芸豆碳氮代谢平衡的影响

采用盆栽土壤基施0、15、30 kg·hm-2三个氮素水平试验,研究了芸豆荚果形成后不同氮素水平下叶片和荚果的碳、氮代谢主要酶活性以及抗氧化酶系活性的变化。结果表明,芸豆荚果形成后,随着土壤供氮水平的增加,荚果的磷酸烯醇式丙酮酸羧化酶活性、多酚氧化酶活性、超氧化物歧化酶和过氧化氢酶活性逐渐增强;叶片的蔗糖合成酶活性、蔗糖磷酸合成酶活性、硝酸还原酶和磷酸烯醇式丙酮酸羧化酶活性大于同一供氮水平荚果的活性;且荚果的总可溶性糖和可溶性蛋白含量高于叶片;叶片的磷酸烯醇式丙酮酸羧化酶的活性与荚果的蔗糖磷酸合成酶和硝酸还原酶活性呈显著相关性。由此可以得出,源器官是芸豆植株的代谢活跃中心,而库器官成为植株的生长中心,且后者的碳、氮代谢过程主要受前者的调控。