Metabolism of isopropyl carbanilate (propham) in alfalfa grown in nutrient solution

Alfalfa plants, Moapa variety, were grown in nutrient solution containing isopropylring-[¹⁴C] carbanilate (43.8 μCi/liter propham). After 8 days, 41.2% of the radioactivity initially added to the nutrient culture was recovered; 10.9% of this was from shoots, 3.4% from roots and 26.9% from nutrient medium. Nonextracted residues accounted for 23% of the radioactivity in shoots and 62% of that in roots. The parent herbicide constituted 53 and 38% of the radioactivity extracted from shoots and roots, respectively. The balance of extracted ¹⁴C was polar metabolites which were purified and subjected to enzymatic and acid hydrolysis. Four aglycones were isolated, three of which were purified by thin-layer chromatography and characterized by mass spectrometry. The principal aglycones were: isopropyl-2-hydroxycarbanilate, isopropyl-4-hydroxycarbanilate, and 1-hydroxy-2-propylcarbanilate. The fourth aglycone was not identified.     

Animal metabolism of propham (isopropyl carbanilate): The fate of residues in alfalfa when consumed by the rat and sheep

Alfalfa was root-treated with [¹⁴C]propham (isopropyl carbanilate[¹⁴C-phenyl(U)]) for 7 days and then harvested and freeze-dried. Rats and sheep were orally given either ¹⁴C-labeled alfalfa roots ([¹⁴C]root) or ¹⁴C-labeled alfalfa shoots ([¹⁴C]shoot). When the [¹⁴C]root was given, 6.5–11.0% of the ¹⁴C was excreted in the urine and 84.6–89.4% was excreted in the feces within 96 h after treatment. Less than 3% of the ¹⁴C remained in the carcass (total body—gastrointestinal tract and contents) 96 h after treatment. When [¹⁴C]shoot was given, 53.2–55.2% of the ¹⁴C was excreted in the urine, 32.1–43.4% was excreted in the feces, and the carcass contained 0.2–1.1% of the ¹⁴C 96 h after treatment. When the insoluble fraction (not extracted by a mixture of CHCl₃, CH₃OH, and H₂O) of both alfalfa roots and shoots was fed to rats, more than 86% of the ¹⁴C was excreted in the feces and less than 3% remained in the carcass 96 h after treatment. The major radiolabeled metabolites in the urine of the sheep fed ¹⁴C shoot were purified by chromatography and identified as the sulfate ester and the glucuronic acid conjugates of isopropyl 4-hydroxycarbanilate. Metabolites in the urine of the sheep treated with [¹⁴C]root were tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline. The combined urine of rats dosed with [¹⁴C]shoot and [¹⁴C]root contained metabolites tentatively identified as conjugated forms of isopropyl 4-hydroxycarbanilate, isopropyl 2-hydroxycarbanilate, and 4-hydroxyaniline.     

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.     

Soybean shoot metabolism of isopropyl-3-chlorocarbanilate: Ortho and para aryl hydroxylation

This laboratory reported that isopropyl-3-chlorocarbanilate-phenyl-U-¹⁴C (chlorpropham-phenyl-¹⁴C) was absorbed, translocated, and metabolized by soybean plants. Both polar metabolites and insoluble residues were found in roots, whereas only polar metabolites were found in shoot tissues. In both roots and shoots the polar metabolites were shown to be the O-glucoside of isopropyl-2-hydroxy-5-chlorocarbanilate (2-hydroxy-chlorpropham). In shoot tissue there were other polar metabolites that were not identified. The experiments with soybeans have been repeated, but with new isolation and purification procedures. The plants were root treated with both chlorpropham-phenyl-¹⁴C and isopropyl-3-chlorocarbanilate-2-isopropyl-¹⁴C. The roots and shoots were extracted and separated into the polar, nonpolar, and insoluble metabolic components, using the Bligh-Dyer extraction method. The polar metabolites were separated by gel permeation chromatography. Further purification was accomplished on Amberlite XAD-2. The polar metabolites from the shoot and root tissues were hydrolyzed either by β-glucosidase or hesperidinase. The enzyme liberated aglycones were derivatized and separated by gas-liquid chromatography, and the components were characterized by mass spectrometry or NMR. The results of this study showed that the polar metabolites of soybean shoots were 2-hydroxy-chlorpropham and isopropyl-4-hydroxy-3-chlorocarbanilate (4-hydroxy-chlorpropham). These two hydroxy-chlorpropham metabolites were found in soybean shoots at a ratio of approximately 1:1. The only aglycone found in root tissue was 2-hydroxy-chlorpropham. Using the new procedures, no evidence was obtained for the presence of the unidentified polar metabolites that were previously observed in shoot tissues.     

Metabolic studies of 14C-labeled propham and chlorpropham in the female rat

The tissue distribution and excretion of ¹⁴C-labeled propham and chlorpropham were investigated in the adult female rat after a single oral dosage. The average 3-day urinary excretions of radioactivity were 55.9%, 82.6%, 79.5%, and 85.4% of an oral dose of chain [¹⁴C] chlorpropham, ring [¹⁴C] chlorpropham, chain [¹⁴C] propham, and ring [¹⁴C] propham, respectively. With chain [¹⁴C] chlorpropham 35.4 ± 7.5% of the administered radioactivity appeared in the respired air, whereas only 5.0 ± 0.8% was found in CO₂ from chain [¹⁴C] propham. There was no significant difference in the rate of excretion or the route of elimination among rats receiving different oral dosages, ranging from less than 4 mg/kg to 200 mg/kg. The radioactivity was distributed in all tissues with highest concentration found in the kidney. The average biological half-life of ¹⁴C from chlorpropham and propham in most organs was short, ranging between 3 and 8 hr; however, in brain, fat, and muscle, the half-life was about twice the value for other organs.Both compounds were metabolized by hydrolytic and oxidative mechanisms and the resulting metabolites were excreted either as free forms or as conjugates.Subcellular distribution of ¹⁴C in the rat liver and kidney after an oral administration of chlorpropham and propham was investigated. The percentage distribution of ¹⁴C in the particulate and soluble fractions was dependent on the elapsed time after dosing.     

Metabolism of [C]vernolate in soybeans

Penetration and metabolism of [¹⁴C]vernolate in soybean [Glycine max (L.) Merr. var Ransom] pods and seeds were measured 0, 1, 4, 24, 48, or 72 hr after treatment which occurred at 40 days after flowering. Total ¹⁴C recovery decreased ca. 50% within 4 hr and the loss of ¹⁴C was considered to be a measure of volatility. Total nonpolar extractants decreased in a logarithmic pattern which approached 10% of total ¹⁴C recovered within 24–48 hr. Total polar extractants increased in a logarithmic pattern to a maximum of 90% of total ¹⁴C recovered within 24 hr. Seed nonpolar extractants never exceeded 2% of the total ¹⁴C recovered while pod nonpolar extractants consisted of vernolate plus an unidentified component that did not thin-layer chromatograph (TLC) as the sulfone or sulfoxide. Pod polar extractants increased with time to ca. 75% of the total ¹⁴C recovered (24–48 hr) and decreased to ca. 58% at 72 hr after treatment. Seed polar extractants averaged ca. 10% of total ¹⁴C recovered for the first 48 hr after treatment and then increased to 30% of total ¹⁴C recovered. Thus, [¹⁴C]vernolate per se concentration decreased to <1% of applied material within 72 hr through volatilization and degradation of nonpolar extractants to polar products. Polar metabolites showed two major patterns of vernolate detoxification. One detoxification system produced ¹⁴C-metabolites whose R_f's were equivalent to that reported in corn (Zea mays L.) [J. P. Hubbell and J. E. Casida, [J. Agric. Food Chem. 25, 404 (1977)] and accounted for <30% of the pod polar extractants. A second detoxification system was most prevalent in soybean pod and seed tissues and resulted in very rapid modification of vernolate with an unidentified product that was 85% of the extracted ¹⁴C within 4 hr after treatment and which decreased in concentration with time. Therefore, unexplained vernolate detoxification system(s) exist in soybean pod and seed.     

Metabolism of [14C]vernolate in soybeans

Penetration and metabolism of [¹⁴C]vernolate in soybean [Glycine max (L.) Merr. var Ransom] pods and seeds were measured 0, 1, 4, 24, 48, or 72 hr after treatment which occurred at 40 days after flowering. Total ¹⁴C recovery decreased ca. 50% within 4 hr and the loss of ¹⁴C was considered to be a measure of volatility. Total nonpolar extractants decreased in a logarithmic pattern which approached 10% of total ¹⁴C recovered within 24–48 hr. Total polar extractants increased in a logarithmic pattern to a maximum of 90% of total ¹⁴C recovered within 24 hr. Seed nonpolar extractants never exceeded 2% of the total ¹⁴C recovered while pod nonpolar extractants consisted of vernolate plus an unidentified component that did not thin-layer chromatograph (TLC) as the sulfone or sulfoxide. Pod polar extractants increased with time to ca. 75% of the total ¹⁴C recovered (24–48 hr) and decreased to ca. 58% at 72 hr after treatment. Seed polar extractants averaged ca. 10% of total ¹⁴C recovered for the first 48 hr after treatment and then increased to 30% of total ¹⁴C recovered. Thus, [¹⁴C]vernolate per se concentration decreased to <1% of applied material within 72 hr through volatilization and degradation of nonpolar extractants to polar products. Polar metabolites showed two major patterns of vernolate detoxification. One detoxification system produced ¹⁴C-metabolites whose R_f's were equivalent to that reported in corn (Zea mays L.) [J. P. Hubbell and J. E. Casida, [J. Agric. Food Chem. 25, 404 (1977)] and accounted for <30% of the pod polar extractants. A second detoxification system was most prevalent in soybean pod and seed tissues and resulted in very rapid modification of vernolate with an unidentified product that was 85% of the extracted ¹⁴C within 4 hr after treatment and which decreased in concentration with time. Therefore, unexplained vernolate detoxification system(s) exist in soybean pod and seed.     

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.     

Zum Metabolismus von Phenylharnstoff-Herbiziden VII. Metabolismusaufklärung und Bilanzierung des Verbleibs von Buturon-14C nach Anwendung bei Winterweizen.

Metabolism of Phenylurea Herbicides. VII. Metabolism Studies and Balance of the Fate of Buturon-¹⁴C after Application to Wheat. Radioactivity counts at harvest showed that 89.1% of the label was recoverable. Of this 50.1% was detected in the soil, 12.6% in the straw, 3.7% in the roots and 1.3% in the grain, while 16.2% was converted to radioactive CO₂. Only about 50% of the radioactivity in the plant material was extractable. This part of the activity consisted mainly of strongly polar metabolites, while the four less polar buturon metabolites accounted for only up to 12% each.     

Biochemical response of inbred and hybrid corn (Zea mays L.) to R-25788 and its distribution with EPTC in corn seedlings

The average endogenous GSH content of eight lines of inbred corn was almost twofold greater than ten varieties of hybrid corn. When inbred and hybrid corn lines were treated with R-25788, the average GSH content increased by 56 and 95%, respectively. R-25788 protected two special inbred corn lines, GT 112 (atrazine susceptible) and GT 112 RfRf (atrazine resistant) from EPTC injury by increasing the GSH content and GSH S-transferase activity in roots. Most of the radiolabel from [¹⁴C]R-25788-treated plants remained in the root tissues whereas the radiolabel in [¹⁴C]EPTC-treated plants was evenly distributed between foliar and root tissues. From radiolabel experiments, hybrid corn seedlings were found to absorb more R-25788 from soil than EPTC. There was no difference between inbred and hybrid corn in the amounts of R-25788 or EPTC taken up or in the enhancement of GSH S-transferase activity caused by R-25788.     

Comparison of trifluralin,oryzalin, pronamide,propham, and colchicine treatments on microtubules

The mode of action of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), oryzalin (3,5-dinitro-N⁴,N⁴-dipropylsulfanilamide), pronamide(N-(1,1-dimethylpropynyl) 3,5-dichlorobenzamide), and propham (isopropyl carbanilate) on purified microtubules from pig brains and on the ultrastructure of wheat (Triticum aestivum L. “Mediterranean,” C. I. 5303) and corn (Zea mays L. “yellow dent, U. S. 13”) roots was compared with that known for colchicine. Colchicine disrupts the in vivo cortical and spindle microtubules of root cells. Like colchicine, the herbicides trifluralin, oryzalin, and pronamide caused the loss of both cortical and spindle microtubules of root cells. The rate of microtubule disappearance depended on the type of herbicide and length of exposure of roots to the herbicide. Unlike colchicine, cortical microtubules were present in propham-treated roots but they were disoriented within the cell.In vitro polymerization studies with pig brain microtubules (Sus scrofa) showed that the herbicides failed to inhibit the assembly of purified microtubular protein into microtubules and that radioactively labeled herbicides did not bind to the microtubular protein. Colchicine inhibited the polymerization of microtubular protein and readily bound to the microtubular subunits. These results indicate that the mode of action of the herbicides is not similar to that of colchicine and that the loss of microtubules from root tip cells treated with trifluralin, oryzalin, and pronamide may be caused by these herbicides interfering with synthesis of microtubular protein or metabolism of endoplasmic reticulum membranes involved in microtubule assembly. The mode of action of propham appears to be on the microtubular organizing centers rather than on microtubules per se.     

Absorption, translocation, and fate of propyzamide in witloof chicory (Cichorium intybus L.) and common amaranth (Amaranthus retroflexus L.)

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.     

The elimination of (N-[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide) by the boll weevil

Boll weevils, Anthonomus grandis Boheman, were either dipped in or injected with a solution of [¹⁴C]diflubenzuron (N-[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide) or fed on cotton squares that had been treated with the chemical to determine its turnover time and metabolic fate. No significant differences were observed between male and female weevils in their ability to eliminate [¹⁴C]diflubenzuron. Only minor differences were observed when immersion and injection treatments were compared. When weevils were treated with 66.3 ng of [¹⁴C]deflubenzuron per weevil by injection, the insects contained 13 to 15% of the radiolabel after 6 days and 4 to 6% after 13 days. The remainder of the radiolabel was in the frass. When weevils fed for 66 hr on cotton squares that had been treated with a wettable [¹⁴C]diflubenzuron preparation (Dimilin W-25), the insects averaged 120 ng of diflubenzuron per weevil. Forty-four hours after removing insects from the treated squares, 50% of the radiolabel had been excreted. In all cases, the radiolabel found in the frass or in the weevil was unchanged diflubenzuron. There were no data to indicate that the boll weevil could metabolize appreciable amounts of diflubenzuron.     

Absorption,translocation and metabolism of 14C-glyphosate in several weed species*

The pattern and extent of ¹⁴C-glyphosate [N-(phosphonomethyl)glycine] translocation from the treated leaf and metabolism of ¹⁴C-glyphosate were studied in field bindweed (Convolvulus arvensis L.), hedge bindweed (Convolvulus sepium L.). Canada thistle [Cirsium arvense (L.) Scop.] tall morning glory [lpomoea purpurea (L.) Roth.] and wild buckwheat (Polygonum convolvulus L.). ¹⁴C was translocated throughout the plants within 3 days with accumulation in the meristematic tips of the roots and shoots evident. Cross and longitudinal sections of stems and roots showed that the ¹⁴C was localized in the phloem. Field bindweed translocated 3–5% of the applied ¹⁴C from the treated leaf, hedge bindweed 21.6%, Canada thistle 7.8%, tall morningglory 6.5%, and wild buckwheat 5%. Field bindweed, Canada thistle, and tall morningglory metabolized the parent glyphosate to aminomethylphosphonic acid to a limited extent. This metabolite made up less than 15% of the total 14C. Of the total ¹⁴C applied to excised leaves, 50% had disappeared within 25 days.     

Studies on the mode of action of asulam,aminotriazole and glyphosate in Equisetum arvense L. (field horsetail). II: The metabolism of [14C]asulam, [14C]aminotriazole and [14C]glyphosate

The metabolism of [¹⁴C]asulam (methyl 4-aminophenylsulphonylcarbamate), [¹⁴C] aminotriazole (1H-1,2,4-triazol-3-ylamine) and [¹⁴C]glyphosate (N-(phosphonomethyl)glycine) were assessed in Equisetum arvense L. (field horsetail). Following application of the test herbicides (4mg?0.3 °Ci herbicide/shoot) to the shoots of 2-year-old pot-grown plants, the total recovery of ¹⁴C-label after 1 week and 8 weeks was high for all three herbicides (>80-0% of applied radioactivity). Asulam was persistent (>69-7% of recovered radioactivity) in both shoots and rhizomes. Sulphanilamide, a hydrolysis product of asulam, accounted for the remainder of the recovered radioactivity. Aminotriazole showed evidence of conjugation in shoots and rhizomes. The principal ¹⁴C-labelled component in shoots was composed of high proportions of aminotriazole (>76-3%) together with the metabolites: X (ninhydrin positive), β-(3-amino-1,2,4-triazolyl-1-)α-alanine, Y (diazotization positive) and various unidentified compounds. Rhizomes generally contained lower proportions of intact aminotriazole (>59.4%) together with the metabolites X,Y and unidentified compounds. The proportion of aminotriazole did not decrease with time in shoots or rhizomes; however, the ratio of metabolite X: Y moved in favour of Y as the interval after treatment increased. Glyphosate was extensively metabolised in shoots and rhizomes to yield aminomethylphosphonic acid (AMPA) and various unidentified compounds. Differential metabolism appears to be one of the factors which may govern the persistence and toxicity of the test herbicides in E. arvense.     

The degradation of (Z)- and (E)-1,3-dichloropropenes and 1,2-dichloropropane in soil

The degradation in soil of the major constituents of a 1,3-dichloropropene-1,2-dich-loropropane nematicide has been studied under laboratory and outdoor conditions. In sealed glass containers, ( Z)- and ( E)-1,3-dichloropene- 2-¹⁴C were converted in soil into the corresponding 3-chloroallyl alcohols and these alcohols were in part strongly bound to the soil. The ( Z)- and ( E)-3-chloroacrylic acids were also found as minor products. More polar products were detected and these released the chloroacrylic acids in 20–30% yield upon hydrolysis. Although the 1,3-dichloropropenes were lost by volatilisation from soil stored in open glass jars outdoors, they also underwent degradation to the same products that were detected in sealed containers. There was evidence of only slight degradation of 1,2-dichloropropane- 2-¹⁴C (4 % or less of the applied radioactivity remained unextracted from a loam soil after 5 months). When soil treated with the 1,2-dichloropropane was stored outdoors in an open glass container, less than 1 % of the original radiolabel remained in the soil after 10 days under these conditions due to volatilisation of the applied material. In a separate experiment potatoes were grown in soil 6 months after treatment with a mixture of both ( Z)- and ( E)-1,3-dichloropropene- 2-¹⁴C and 1,2-dichloropropane- 2-¹⁴C. Although 5 % of the applied radiolabel remained in the soil at potato harvest the potato tubers contained only a very small residue (0.007 mg/kg).     

Metabolism of DDT and related compounds in cell suspension cultures of soybean (Glycine max L.) and wheat (Triticum aestivum L.)

Cell suspension cultures of wheat and soybean were incubated with [¹⁴C]-1,1,1-trichloro-2,2-bis-(4-chlorophenyl)ethane (DDT), [¹⁴C]-1,1-dichloro-2,2-bis-(4-chlorophenyl)ethene (DDE), and [¹⁴C]-2,2-bis-(4-chlorophenyl)acetic acid (DDA) under standardized conditions. Polar metabolites were formed in yields of 1–2.5% in the cases of DDT and DDE, and of 56% in the case of DDA. A nonpolar metabolite was only observed in the case of DDT in soybean. This metabolite was identified as DDE on the basis of cochromatography and mass spectroscopy. By the same methods DDA was identified as a major polar DDT metabolite of both soybean and wheat. The further conversion of DDA to hexose esters was demonstrated by chromatographic and mass spectroscopic comparison with synthetic DDA-β-d-glucopyranosyl tetraacetate. These studies suggest the metabolic sequence, DDT → DDA → DDA-hexose ester.     

Uptake and fate of triticonazole applied as seed treatment to spring wheat (Triticum aestivum L.)

Following seed treatment of wheat (Triticum aestivum L.) with ¹⁴C-labelled triticonazole at a dose of 1·8 g kg^-1 seed, the uptake of radioactivity by shoots and roots was investigated from the two- to three-leaf stage up to the beginning of the booting phase, 80 days after sowing. Triticonazole equivalents taken up by wheat plants reached 5·7% and 14·6% of the applied dose in the shoots and the roots, respectively. Between the two- to three-leaf stage and the beginning of the booting phase, the concentration of triticonazole equivalents in the shoots decreased from 2·5 to 0·15 μg g^-1 fresh weight. This was attributed to uptake of triticonazole by roots not keeping pace with shoot growth and increased retention in the roots of triticonazole taken up. The main factor limiting the uptake of triticonazole by the roots may be the rapid growth of the uptake-active apical root parts out of the dressing zone which had formed in the soil. Distribution of triticonazole equivalents taken up by the main shoot showed a decreasing concentration gradient from the oldest to the youngest leaf. An increase in the seed treatment dose was investigated as a way to increase the concentration of triticonazole in the shoots, but its influence remained limited. © 1998 SCI     

Absorption and distribution of flurazole and acetochlor in grain sorghum

The site of uptake, absorption, and distribution of a safener, flurazole [2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylic acid, (phenylmethyl ester)], and a herbicide, acetochlor [2-chloro-N-(ethoxymethyl)-6′-ethyl-O-acetoluidide], in grain sorghum [Sorghum bicolor (L.) Moench “G-522 DR”] were investigated in laboratory and growth chamber studies. Acetochlor was absorbed through shoots while flurazole was taken up primarily by roots. Uptake of [¹⁴C]acetochlor into the plant was rapid, linear, and the ¹⁴C was concentrated in primary roots by 7 days. Absorption of [¹⁴C]flurazole by sorghum was immediate, leveled off at 4 days, and the ¹⁴C was concentrated in primary roots by 7 days. Absorption and distribution of either chemical were not affected by the presence of the other. Flurazole had a slight effect on acetochlor metabolism at 3 days, but by 6 days no differences were noted.     

Retention,absorption, translocation and distribution of sethoxydim in monocotyledonous and dicotyledonous plants*

Quackgrass [Elymus repens (L.) Gould =Agropyron repens (L.) Beauv.] and barnyardgrass [Echinochloa crus-galli (L.) Beauv.] were more than one hundred times more susceptible to sethoxydim than alfalfa (Medicago sativa L. 'Saranac') or navybean (Phaseolus vulgaris L. 'Seafarer'). Uptake of sethoxydim From soil following post-emergence applications caused negligible reduction in E. crus-galli fresh weight. More than 80% of foliar-applied ¹⁴C-sethoxydim was absorbed within 6 h in all species. Translocation occurred in all species with accumulation of ¹⁴C in rapidly growing plant tissues. Translocation to the roots was less than 8% of total in all species. Most of the extracted ¹⁴C initially partitioned into an ethyl acetate-soluble fraction. The proportion of ¹⁴C in the ethyl acetate-soluble fraction decreased with time with a concomitant increase of that in the insoluble fraction. Differences in the quantity of ¹⁴C in the ethyl acetate-soluble fraction did not account for the observed selectivity.