Metabolism of [14C]dieldrin in bluegill fish

The exposure of bluegill fish to 50 parts per billion [¹⁴C]dieldrin in a static system resulted in the absorption of 73.00% of the radioactivity in 48 hr. Following transfer of the fish to clean water, only 16.20% of the absorbed radiolabel was eliminated in 23 days. Out of the 93.65% of the absorbed radioactivity recovered, 9 radioactive spots were isolated which included unchanged dieldrin (74.39%), pentachloroketone (8.17%), and aldrin-trans-diol (8.04%) as major metabolites.     

Metabolic fate of [14C]endrin in bluegill fish

Bluegill absorbed 85% of 1 ppb of endrin from water within 48 hr under static exposure conditions. The absorbed radiocarbon was eliminated linearly with a half-life of about 4 weeks. Analyses of eliminated radioactivity revealed only conjugated metabolites. 12-anti-Hydroxyendrin and 12-syn-hydroxyendrin were tentatively identified by cochromatography using thin-layer chromatography/autoradiography and gas chromatography. These metabolites were also present as conjugates in the fish organs. Seventy-three percent of the absorbed radioactivity recovered from fish extracts was in the form of unchanged endrin.     

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 [14C]photodieldrin in goldfish

Goldfish (Carassius auratus) exposed to 20 parts per billion [¹⁴C]photodieldrin in a static system absorbed 80% of the radioactivity within 20 hr. The absorbed radioactivity was eliminated slowly with a half-life of 3 weeks. Photodieldrin and a ketone derivative were the major form of the radiocarbon eliminated in water, accounting for, respectively, 59 and 10.4% of the eliminated radioactivity. The ketone derivative was characterized by cochromatography (thin-layer and gas chromatography, gc) and gc-mass spectrometry. Approximately, 15 other polar and nonpolar metabolites were detected in the aqueous medium. The radioactivity in the fish consisted of 13 metabolites along with photodieldrin. Photodieldrin and the ketone derivative were the most abundant residues in the fish, accounting for 77 and 5.4% of the radioactivity, respectively.     

Metabolic and elimination products of [14C]photodieldrin from bluegill fish

Bluegill fish, following exposure to [¹⁴C]photodieldrin eliminated 50% of the absorbed radioactivity in 3 weeks. Analysis of the products revealed that about 27% of the eliminated radioactivity was due to the unaltered photodieldrin while the rest consisted of at least 11 metabolites in free and conjugated forms. Photodieldrin ketone was the major excretory product. Solvent extracts of the whole fish examined showed 4 metabolites in addition to about 90% of the unmetabolized photodieldrin. The ketone derivative was the most predominant of the metabolic products.     

Soil persistence studies with bromoxynil, propanil and [14C]dicamba in herbicidal mixtures

The persistence of bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), [¹⁴C]dicamba (3,6-dichloro-2-methoxybenzoic-7-¹⁴C acid) and propanil [N-(3,4-dichlorophenyl)propionamide] at rates equivalent to 1 kg ha^?1, were studied under laboratory conditions in a clay loam, a heavy clay and a sandy loam at 85% of field capacity and at 20±1°C, both singly and in the presence of herbicides normally applied with these chemicals as tank-mix or split-mix components. The degradation of bromoxynil was rapid with over 90% breakdown occurring within a week in the heavy clay and sandy-loam soils, while in the clay-loam approximately 80% of the bromoxynil had broken down after 7 days. In all three soils degradation was unaffected by the presence of asulam, diclofop-methyl, flamprop-methyl, MCPA, metribuzin or propanil. Propanil underwent rapid degradation in all soil treatments, with over 95% of the applied propanil being dissipated within 7 days. There were no noticeable effects on propanil degradation resulting from applications of asulam, barban, bromoxynil, dicamba, MCPA, MCPB, metribuzin or 2,4-D. The breakdown of [¹⁴C]dicamba in a particular soil was unaffected by being applied alone or in the presence of diclofop-methyl, flampropmethyl, MCPA, metribuzin, propanil or 2,4-D. The times for 50% of the applied dicamba to be degraded were approximately 16 days in both the clay loam and sandy loam, and about 50 days in the heavy clay.     

Soil persistence studies with [14C]MCPA in combination with other herbicides and pesticides

The persistence of [¹⁴C]MCPA at a rate equivalent to 1 kg ha^?1 was studied under laboratory conditions in a clay loam, heavy clay and sandy loam at 85% of field capacity moisture and 20±1°C both alone and in the presence of tri-allate, trifluralin, tri-allate and trifluralin, malathion, Vitaflow DB, malathion and Vitaflow DB, bromoxynil, bromoxynil and asulam, bromoxynil and difenzoquat, dicamba, dicamba and mecoprop, linuron, MCPB, metribuzin, propanil, TCA, benzoylprop-ethyl, diclofop-methyl, and flamprop-methyl. Except in the soils treated with asulam, the half-lives of [¹⁴C]MCPA in all three soil types were similar, being approximately 13±1 days, thus indicating that none of the other chemicals studied adversely affected the soil degradation of MCPA. In the asulam treated soils, the half-lives of the MCPA were about 3 days longer than in non-asulam treated soils; the effect was most marked in the clay loam.     

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

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.     

Behavior of 14C oryzalin in soil and plants

Radiochemical studies of field soil treated with ¹⁴C oryzalin (3,5-dinitro-N⁴,N⁴-dipropylsulfanilamide) indicated that the compound was readily degradable. One year after soil treatment with oryzalin, 45% of the original radioactivity had dissipated, 25% was extractable, and 30% was “soil bound”. The extractable fraction contained oryzalin and several degradation products, some of which were isolated and identified. No single degradation product accounted for more than 3% of the applied oryzalin. The “soil-bound” radioactivity was extractable with hot alkali. No significant radioactive residues were detectable in either seed or forage of soybean and wheat plants. No specific metabolites of oryzalin were identified in soybean plants. Trace amounts of radioactivity found in plant tissue appeared to be associated with the various plant constituents.     

Absorption and translocation of 14C-3,6-dichloropicolinic acid in Cirsium arvense (L.) Scop.

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.     

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.     

Studies on the mode of action of asulam in bracken (Pteridium aquilinum L. Kuhn) I. Absorption and translocation of [14C]asulam

Studies of the absorption and translocation of foliage-applied ring-labelled [¹⁴C]asulam [methyl (4-aminobenzenesulphonyl) carbamate] were carried out using glasshouse and field-grown bracken plants. Translocation of ¹⁴C from the treated frond was primarily according to a 'source to sink’pattern with intense accumulation of radioactivity in the metabolically active sinks viz. rhizome apices, frond buds, root tips and young frond tissue. In the case of field bracken, translocation and distribution of ¹⁴C was extensive in the rhizome system, accumulation occurring in the active as well as dormant buds situated on the non-frond-bearing and storage rhizome branches. Treatment of fully expanded fronds with 100μl of [¹⁴C]asulam (1 mg, 1.0–1.5 μCi) as 2 μl droplets resulted in a rapid initial uptake during the first week, followed by progressive entry and distribution with time. Basipetal translocation to the rhizome system was positively correlated with total uptake. High humidity (95%) and high temperature (30°C) stimulated uptake and subsequent basipetal translocation to a considerable degree. Uptake was greater through the stomatal-bearing abaxial than through the adaxial cuticle. Incorporation of a surfactant (Tergitol-7, 0.1%) increased penetration by up to 30%. Uptake declined markedly as the frond aged, while translocation was predominantly acropetal in young treated fronds, becoming exclusively basipetal when the fronds matured. Optimum uptake and maximum distribution of [¹⁴C]asulam in the rhizome and its associated buds was achieved when treatments were applied to almost fully expanded fronds. The translocated ¹⁴C (asulam and possibly some of its metabolites) showed a considerable degree of persistence in the rhizome system, 8% of the applied activity still remaining in the rhizome 40 weeks after treatment.     

Conversion of [14C]buturon in soil and leaching water under outdoor conditions

[¹⁴C]Buturon, a urea herbicide, was sprayed on soil and winter wheat as an aqueous formulation (2.98 kg/ha) under outdoor conditions. Three months after application, a total of 49.2% of the applied radiocarbon was recovered: 46.9% in the soil, 0.3% in the leaching water (depth > 50 cm), and 2.0% in the plants. Radioactive residues in the soil were distributed to a depth of 50 cm and decreased with increasing depth of the soil. An average of 47% of the radioactivity present in the soil could be extracted with cold chloroform; by this extraction method, the formation of artefacts was avoided. Between one and two thirds of the extracted radioactivity was unchanged buturon. In the soil extracts, the following eight conversion products were isolated and identified by combined gas chromatography/mass spectrometry: N-(p-chlorophenyl)-N-methyl-O-methyl carbamate; N-(p-chlorophenyl)-O-methyl carbamate; N-(p-chlorophenyl)-N′-methyl-N′-isobutenyl-urea; N-(p-chlorophenyl)-N′-methyl-urea, N-(p-chlorophenyl)-N′-methyl-N′-isobutenylol-urea; p-chloroaniline in “biologically bound” form; N-(p-chlorophenyl)-N′-methyl-N′-methoxyisobutenyl-urea; and N-(p-chlorophenyl)-N′-methyl-N′-ethoxyisobutenyl-urea. In the leaching water, which contained only 0.005–0.006 mg/liter of radioactive substances, the following three conversion products were isolated and identified by gas chromatography/mass spectrometry: p-chloroformanilide; N-(p-chlorophenyl)-N-methyl-O-methyl carbamate; and an N-hydroxyphenyl-N′-methyl-N′-isobutinyl-urea. The results are discussed in relation to the factors responsible for the formation of these products.     

Balance of conversion of [14C]lindane in lettuce in hydroponic culture

After application of [¹⁴C]lindane to the nutrient medium (1.45 ppm), 14.1% of the radioactivity was taken up by 12 lettuce plants during 4 weeks; in the nutrient medium, 7.8% was recovered after the same time interval. The radioactivity in the nutrient extract comprised: unchanged lindane (about 82%); free 2,3,4,6-tetrachlorophenol, free pentachlorophenol, conjugates of pentachlorophenol, and an unidentified polar compound (a total of 15%); 1,2,3-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, 2,3,4,5,6-pentachlorocyclohex-1-ene, and probably 1,2,3,4,5,6-hexachlorocyclohexene (a total of 3%). The radioactivity extracted from plants consisted of unchanged lindane (about 77%); free 2,3,4,6-tetrachlorophenol, conjugates of a tetrachlorophenol and pentachlorophenol, and a strongly hydrophilic compound that was not identified (a total of 20%); 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, pentachlorobenzene, 2,3,4,5,6-pentachlorocyclohex-1-ene, and probably 1,2,3,4,5,6-hexachlorocyclohexene (a total of 3%). Identification was carried out by means of comparisons of chromatographic properties and of the mass spectra with those of authentic reference compounds. The significance of hexachlorobenzene as a metabolite of lindane is discussed.     

Effect of benzoylprop-ethyl on uptake, transport and metabolism of 32P in Avena fatua L. and Triticum aestivum L.

The effect of benzoylprop-ethyl on plant weight, root uptake, transport and metabolism of ³²P in wild oat and wheat plants was examined 4 h, 1,3 and 9 days after treatment. The fresh weight of wild oat plants was significantly reduced, due to herbicide action only, by day 9 after treatment. By day 3, shoot weight was decreased while root weight was significantly increased by 47%. No significant changes in plant weight were caused by benzoylprop-ethyl in wheat plants. Uptake of ³²P by treated wild oat plants decreased by 39% compared with the control, by day 9, after an initial increase; uptake of ³²P was not significantly influenced in wheat plants. By day 1 transport of ³²P to the shoots was significantly reduced in wild oat plants by 34%, whereas in wheat plants it was significantly increased by 35%. Metabolism of ³²P was already hampered in wild oat plants 4 h after treatment. The content of ³²P was reduced on the first two sampling dates in both the roots and shoots of treated plants in all fractions except in DNA in the shoots. On day 3, this decrease was apparent especially in organic, lipidic and nucleic acid fractions in the shoots; incorporation of ³²P into lipidic and RNA fractions was significantly inhibited on day 9 in both the roots and shoots of treated wild oat plants. Wheat plants responded most strongly to benzyoylprop-ethyl on day 1 after treatment, when ³²P incorporation into all fractions except DNA was hampered. Differences between treated and control wheat plants gradually levelled off on days 3 and 9 after treatment.     

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.     

Disposition and metabolism of [14C]chlorpyrifos in the black imported fire ant, Solenopsis richteri Forel

The short-term disposition and metabolism of topically administered [¹⁴C]chlorpyrifos was assessed in the black imported fire ant (Solenopsis richteri Forel) in the presence and absence of the mixed-function oxidase inhibitor piperonyl butoxide. Chlorpyrifos is readily absorbed into an internal organosoluble fraction which was quickly converted into a water-soluble fraction. The radioactivity was slowly excreted over a 24-hr period. Piperonyl butoxide slowed the conversion of the internal organosoluble radioactivity to the water-soluble fraction. Thin-layer chromatography indicated that piperonyl butoxide slowed the conversion of chlorpyrifos to material remaining at the origin, presumably water-soluble metabolites. The results of acid hydrolysis studies indicated that the water-soluble radioactivity was comprised mainly of conjugates. Although very little chlorpyrifos oxon was recovered in the metabolism experiments, in vitro studies on fire and head homogenates showed the compound to be an extremely potent anticholinesterase, with an I₅₀ of 4.6 × 10^?10M, while a major metabolite, 3,5,6-trichloropyridinol, was an ineffective acetylcholinesterase inhibitor.     

Metabolism and balance studies of [14C]monolinuron after use in spinach followed by cress and potato cultures

[¹⁴C]Monolinuron was added to soil which was then successively cropped with spinach, cress, and potatoes. Incubation was carried out in a closed system which allowed recoveries even of volatile degradation products and gave an overall recovery of 96% of the applied radioactivity at the end of the experiment. The spinach was found to contain 4.1% of the applied activity; the cress, 5.6%; old potatoes + leaves, 9.5%; new tubers, 1%; and the soil, 68.6%. The total amount of [¹⁴C]carbon dioxide liberated was 5.3%. The quantitative separation and characterization of the extractable radioactivity in spinach yielded 10.6% as unaltered monolinuron, 12% as 4-chlorophenylurea plus 4-chlorophenyl-hydroxymethylurea, 3.7% as 4-chlorophenylmethylurea, 1.4% as 4-chlorophenyl-hydroxymethyl-methoxyurea, 1.1% as 4-chlorophenyl-methoxyurea, and 71.2% as polar metabolites. Of these polar metabolites, 67.1% were cleaved with β-glucosidase, resulting in 2.9% unknown aglucone, 48.1% 4-chlorophenyl-hydroxymethyl-methoxyurea, and 16.1% 4-chlorophenyl-hydroxymethylurea. Similar results have been obtained in cress and potatoes. The soil contained 58% of monolinuron residues and 4.7?6.5% of the same types of metabolites as were found in plants. Twenty-one percent were found as polar metabolites.     

Fate of [14C]diflubenzuron on cotton and in soil

Aqueous suspensions and oil emulsions of a commercial [¹⁴C]diflubenzuron (N-[[(4-chlorophenyl)amino]carbonyl]-2,6-difluorobenzamide) formulation (Dimilin W-25) remained on the leaf surface of greenhouse-treated plant tissues. Absorption, translocation, and metabolism of the [¹⁴C]diflubenzuron were not significant. Less than 0.05% of the applied ¹⁴C was found in newly developed plant tissues 28 days after spray treatment. [¹⁴C]Diflubenzuron was degraded in soil. After 91 days, biometer flask studies showed that 28% of the ¹⁴C incorporated into the soil as [¹⁴C]diflubenzuron was recovered as ¹⁴CO₂. Major dichloromethane-soluble soil residues were identified as unreacted [¹⁴C]diflubenzuron and [¹⁴C]4-chlorophenylurea. A minor unknown degradation product cochromatographed with 2,6-difluorobenzoic acid. Insoluble ¹⁴C-residues increased with time and represented 67.8% of the residual ¹⁴C in the soil 89 days after treatment. Cotton plants grown for 89 days in [¹⁴C]diflubenzuron-treated soil contained only 3% of the ¹⁴C applied to the soil. Small quantities of acetonitrile-soluble [¹⁴C]4-chlorophenylurea were isolated from the foliar tissues. Root tissues contained small amounts of [¹⁴C]diflubenzuron and trace quantities of a minor ¹⁴C-product that chromotographed similarly to 2,6-difluorobenzoic acid. Most of the ¹⁴C in the plant tissues (84–93%) was associated with an insoluble residue fraction 89 days after treatment.     

Differential tolerance of peas to prometryne and terbutryn

The phytotoxicity of 2,4-bis(isopropyl)-6-(methylthio)-s-triazine (prometryne) and 2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine (terbutryn) to peas (Pisum sativum L. var. Perfection 3040) was studied. No differences were found when the herbicides were applied to the roots of intact plants in nutrient solution or directly to leaf discs. However, prometryne was much more toxic when uptake was from soil. Absorption and translocation of ¹⁴C-labeled prometryne and terbutryn showed that the majority of terbutryn accumulated in the roots, whereas prometryne was uniformly distributed between the roots and the shoot. Thin layer chromatography of extracts from prometryne-treated peas showed that only 20% of the absorbed compound was metabolized to produce one breakdown product. Extracts of terbutryn-treated plants contained three different metabolites. After 120 hr of exposure to terbutryn, about half of the absorbed herbicide was metabolized. The results show that the main factors responsible for the differential toxicity of the herbicides to peas were availability from the soil, translocation pattern and initial detoxication.