Potassium uptake in atrazine-treated roots of sensitive and resistan plants

The action of atrazine and its biodegradation products on the membrane transport of potassium in roots was evaluated in both sensitive and resistant plants. Excised roots of maize and oat showed inhibition of potassium uptake efficiency in the presence of 1.4 × 10^?4M atrazine and 1.4 × 10^?4M deethylated atrazine. Other biodegradation products such as 2-chloro-4-amino-6-ethylamino-1,3,5-triazine,2-chloro-4,6-,bisamino-1,3,5-triazine, and 2-chloro-4-amino-1,3,5-triazine showed no inhibitory effect on the K⁺ uptake capacity. Two maize hybrids showing different uptake efficiency were inhibited differently by atrazine. We suggest that atrazine and deethylated atrazine inhibited the K⁺ transport interacting directly with the plant cell membranes without discerning between resistant and sensitive plants.     

The disappearance and movement of three triazine herhicides and several of their degradation products in soil under field conditions

Several degradation products of the iriazine herbicides atrazine [2-chloro-4-ethylamino-6-isapropylainino-1,3,5-triazine], cyprazine [2-chloro-4-cyclopropylamino-6-isopropylamino-1,3,5-triazine] and cyanazine [2-chloro-4-(l-cyanomethylethyl-amimo)-6-ethylamino-1,3,5-triazine] were monitored over a 3-year period in soil Trom fields under maiTC production. The soils were predominately loamy sands and sandy clay loams. HydroKy-triazines were determined semi-quanlilatively m the soil samples by gaschromalography, after methylation. Their levels ranged Trom 0.05 to 0.5 ppm. The hydroxy-triazines were the predominant triazine residues in the field during ihe spring and autumn, N-de-ethylated atrazine [2-chloro-4-amino-6-iso-propylamino-1,3,5-triazine] persisted at relatively high levels (0.015–0.02 ppm) 12 months after the application of atrazine. Greater proportions of N-de-ethylated atrazine and cyanazine II [2-chloro-4-(1-carbamoyl-1-methyleihylamino)-6-ethyl-amino-s-iriazine] than of atrazine or cyanazine were found to move through the soil profile into subsurface drainage water (1.2–1.6 m depth). Abbau und Transport von drei Triazin-Herbiziden und einiger ihrer Abbauproduk te im Boden unter Feldhedingungen Boden von Maisfeldern wurde über eine Periode von drei Jahren auf Abbauprodukte folgender Triazin-Herbizide unter-suchi: Atrazin [2-Chlor-4-äthylamino-6-isopropylatnino-1,3,5-triazin], Cyprazin [2-Chlor-4-cyclopropylamino-6-isopropyla-mino-1,3,5-(triazin) und Cyanazin [2-Chlor-4-(1-cyanoinethy-läthylamino)-6-äthylamino-1,3,5-triazin], Bei den Böden han-delie es sich hauptsächlich um lehmige Sande und sandig-tonige Lehme Hydroxy-Triazine wurden in den Bodenproben gas-chromatogruphish nach Methylierung. semi-quantitativ be-stimmt. Ihre Konzeniration im Boden betrug zwischen 0.05 und 0.5 ppm. Die Hydroxy-Triazine waren im Frähjahr und Herbst die vorherrschenden Rücksiände, N-desäthylieries Airazin [2-Chlor-4-amino-6-isopropyIamino-1,1,5-triazin] war zwölf Monate nach der Atrazin-Applikation mit relative hohen Kon-zenirationen(0.015–0.02 ppm) vorhanden. Von N-desäthylier-tem Airazin und Cyanazin II [2-Chlor-4-(1 carbamoyl-1–methy-läthylamino)-6-äthylamino-s-triazin] wurden grössere Anteile im Boden in das unterirdische Drainagewasser transportiert (1.2–1.6 m Tiefe) als es für Atrazin oder Cyanazin der Fs Swiir Disparition et migration dans le sol, au champ, de trois triazines herhicides et de plusieurs de leurs produits de dégradalion. Plusieurs produits de dégradation des triazines herbicides suivantes: atrazine (2-chloro-4-éthylamino-6-isopropylamino-1,3,5-triazine) cyprazine (2chloro-4-cyclopropylamino-6-isopropylamino-l,3,5-triazine) et cyanazine (2-chloro-4 (l-cyanométhyléthylamino)-6-éthylamino-l,3,5-triazine) ont été contrölés dans le sol. pendant une période de trois années, dans des champs de maïs en production, Les sols étaient pour la plupart sablo-limoneux et limono-argilo-sableux, Les hydroxy-triazines ont été déterminées semi-quantalivcmeni dans les échantillons de sols, par chroma tographie gazeuse aprés méthy lation, Leursconcen [rations s'étendaienlde0.05à 0.5ppm, Les hydroxy-triazines ont été les résidus les plus imporiants dans le champ au printemps et à I'aulomne, L'alrazine N-dé-éthylée [2-chloro-4-amino-6-isopropylamino-l.3.5-triazine] a persistéà des concentralions rclativemeni élevées (0.015 à 0.02 ppm) douzemois aprés l'application de l'atrazine, Il a été conslaté que des proportions d'atrazine N-dé-éthylée et de cyanazine II [2-ehloro-4(l-carbamoyl-1-méthyléthylamino)-6-éthylamino-1,3,5-triazine] plus importantes que celles de l'atrazine ou de la cyanazine, migraient à travers le profil du sol. dans la subsurface de drainage dc l'eau (1,2 à 1.6 m de profondeur).     

Hydrolysis of the triazine herbicide,cyanazine

The hydrolysis of cyanazine

1 Cyanazine is the proposed common name for the herbicide sold under the Shell registered trade name BLADEX.

(2-chloro-4-cyanoisopropylamino-6-ethylamino-1,3,5-triazine) has been studied using ¹⁴C-ring labelled compound over a temperature range of 25° to 75 °C and over a range of pH values from 1.5 to 12. The activation energies and the activation entropy changes during hydrolysis showed there was a different mechanism under acid and alkaline conditions. The only product identified after hydrolysis in acid solutions was 2-hydroxy-4-carboxyisopropylamino-6-ethylamino-1,3,5-triazine. In alkaline solution the same hydroxy-acid was the end-product, but 2-chloro-4-amidoisopropylamino-6-ethylamino-1,3,5-triazine was isolated as an intermediate. The variation of the specific rate constants with temperature for hydrolytic catalysis by H⁺, OH^? was determined, thus enabling the hydrolytic half-life of cyanazine to be calculated at any pH and temperature.     

The rapid determination of atrazine residues in soil using infrared spectrophotometry

A rapid method for the determination of atrazine (2-chloro-6-ethy!amino-4-isopropylamino-l,3,5-triazine) residues in soil is presented. The method, which is particularly suited to laboratory studies of leaching or degradation, has the advantage of rapid throughput as it requires no clean-up steps. Interference by different soil types, however, prevents its use in normal soil residue assays.     

The analysis of crops and soils for the triazine herbicide cyanazine and some of its degradation products. I. Development of method

Radiochemical techniques have been used to develop efficient procedures for the extraction of residues of cyanazine herbicide [‘BLADEX’,

1 BLADEX and FORTROL are Shell registered Trade Marks.

^a ‘FORTROL’,^a 2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine] and its metabolites 2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-ethylamino-1,3,5-triazine ( II ), 2-chloro-4-(1-cyano-1-methylethylamino)-6-amino-1,3,5-triazine ( V ) and 2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-amino-1,3,5-triazine ( VI ) from crops and soils. Partition and column chromatographic techniques have been established for the purification of the extracts. The full analytical procedure is described and the final determination of all four compounds is by g.l.c. with electron capture detection with blank values for field samples generally 0.02 part/million and with good recoveries.     

N-Dealkylation of atrazine and simazine in Senecio vulgaris biotypes: A major degradation pathway

Separate populations of Senecio vulgaris were found that evolved partial tolerance to s-triazine herbicides and others that were totally resistant (plastid resistance). In plants from the susceptible, tolerant, and resistant populations, about one half of applied [¹⁴C]atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) was rapidly N-dealkylated to the des-ethyl and des-isopropyl products. These products were relatively inactive in inhibiting photosystem II and did not compete with atrazine. After 6 days, less than 25% of the applied [¹⁴C]atrazine was metabolized to water-soluble degradation products but they were not 2-hydroxy derivatives. Less than 2% of the applied atrazine was incorporated into methanol-insoluble residues. The results on metabolism do not explain the tolerance of Senecio to atrazine. However, our results show that N-dealkylation of the s-triazines is more active than previously reported.     

The effect of atrazine,cyanazine and cyprazine on photosynthesis and growth of nine grasses*

A semi-open circuit system for measuring changes in net CO₂ exchange (NCE) in single leaves of intact grasses following herbicide treatment is described and evaluated. There were significant differences in levels of inhibition and subsequent recovery of NCE in maize and eight weedy panicoid grasses following limited root uptake of atrazine (2-chloro-4-ethyl-amino-6-isopropylamino-1,3,5-triazine). cyanazine [2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine] and cyprazine (2-chloro-4-cyclopropylamino-6-isopropyl-amino-1,3.5-triazine). Rate of NCE recovery was positively correlated (P = 0.05) with growth of seedlings in nutrient solution containing the herbicides. Rates of NCE recovery >0.9 mg CO2 per dm2 per h/h reflected rapid rates of herbicide detoxification in the leaves and a significant tolerance to preplant incorporated and postemergence applications of atra-zine, cyanazine and cyprazine. In contrast, some species, e.g. large crabgrass [Digitaria sanguinalis (L.) Scop.] and proso millet (Panicum miliaceum L.) treated with cyanazine demonstrated considerable tolerance to these treatments in spite of low NCE recovery rates indicating that factors other than foliar detoxification may play an important role in the tolerance of some grasses to 2-chloro- 1,3,5-triazine herbicides.     

The analysis of crops and soils for the triazine herbicide cyanazine and some of its degradation products. II. Results

Crops and soils from field trials in 1967–1970 in several countries have been analysed for residues of the triazine herbicide cyanazine (‘BLADEX’

1 Shell Registered Trade Mark.

^a or ‘FORTROL’^a' 2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine) and for its degradation products 2-chloro-4-(1-carbarmoyl-1-methylethylamino)-6-ethylamino-1,3,5-triazine ( II ), 2-chloro-4-(1-cyano-1-methylethylamino)-6-amino-1,3,5-triazine ( V ) and 2-chloro-4-(1-carbonyl-1-methylethylamino)-6-amino-1,3,5-triazine ( VI ). The time for the concentration of cyanazine in soils to fall to half the initial value was in the range 1.3 to 5 weeks with a mean value of 2.4 weeks. The rate of loss was not affected by sparse crop cover and there was some indication that the rate was greater under moist soil conditions. Residues of up to 0.5 part/million of ( II ) and up to 0.08 part/million of ( VI ) were detected in soils at 4 weeks from cyanazine application at 2 kg/ha. The residues of cyanazine and the degradation products declined rapidly and were 0.07 part/million or less at 16 weeks from treatment. Repeated annual applications did not lead to a detectable build up of residues in soil. Neither residues of cyanazine nor those of ( II ), ( V ) or ( VI ) could be detected in a wide range of crops harvested from soil treated in accordance with the likely recommendations and the limits of detectability were 0.01 to 0.04 part/million.     

Extraction and identification of a new degradation product of atrazine in the soil

Gas-chromatographic analyses of extracts of soil samples from plots, treated with a 50% atrazine wettable powder at dose rates of 2 and 4 kg a.i. ha^?1, showed the presence of a new atrazine degradation product. This product was isolated, concentrated and purified by column chromatography and high-performance liquid chromatography. The chromatographic properties of this material were identical with those of a product isolated from a 0.02% methanolic solution of 2-amino-4-chloro-6-isopropyl-amino-1,3,5-triazine that had been stored under laboratory conditions. A combined gas-liquid chromatographic/mass spectrometric assay identified the new product in soil as 2-isopropylamino-4-methoxy-6-methylamino-1,3,5-triazine.     

Effect of 4-amino-6-methyl-3-phenylamino-l,2,4-triazin-5(4H)-one on the lignification process catalysed by peroxidase from lupin (lupinus albus)

The molecular action of herbicides with a triazine structure, such as atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) and metribuzin (4-amino-6-tert-butyl-3-methylthio-1,2,4-triazin-5(4H)-one), has been related to their inhibition of the electron carrier system between chloroplastic photosystems II and I. This report provides evidence that 4-amino-6-methyl-3-phenylamino-1,2,4-triazin-5(4H)-one, a recently synthesised triazine, structurally analogous to metribuzin, causes a powerful inhibition of the cell-wall lignification catalysed by peroxidase from lupin. The two reactions involved in this lignification process are: oxidative polymerisation of coniferyl alcohol and the generation of hydrogen peroxide at the expense of NADH oxidation.     

Influence of some 1,3,5-triazine herbicides on peroxidase activity in corn seedlings

The effect of some 1,3,5-triazine herbicides, on the rate of oxidative decarboxylation of tryptophan by peroxidase from corn seedlings, varied with the concentration. Atrazine was stimulatory in vivo at 10-⁶M but not at 10⁸ M or lower, whereas terbutryne was inhibitory at 10-⁶M but not at 10-⁸M or below. Prometryne inhibited enzyme activity at 10-⁶M and stimulated it at 10-¹⁰M and at 10¹²M, while simazine caused stimulation at 10-⁶M and inhibition at 10^?10M and 10^?12M. Atraton reduced enzyme activity at 10^?6M and 10^?8M but had no effect at 10^?10M and 10^?12M. When peroxidase activity was assayed in acetone-dried powders from seeds, harvested from fields that had received typical atrazine applications, the quantities of tryptophan consumed were significantly less than the quantity determined in the control powder. From the results obtained, by incorporating dealkylated and 2-hydroxy metabolites of atrazine at 10^?6M into the culture solutions, it seems possible that the inhibition observed may have been due to the presence of 4-amino-6-ethylamino-1, 3, 5-triazin-2-ol and/or 4, 6-diamino-1, 3, 5-triazin-2-ol residues in seeds from treated plots, even if, in previously reported experiments, analyses had not detected their presence.     

Triazine herbicide residues in central European streams

Triazine herbicide residues were monitored in the rivers Adour, Danube, Garonne, Herault, Loire, Marne, Oise, Rhine, and Rh?ne from spring 1976 to fall 1977 to determine whether the continued use of the compounds resulted in accumulations of undesirable residues in the streams. Samples were generally collected monthly or bimonthly and analyzed for the parent compounds atrazine, simazine, terbumeton, terbuthylazine, and dealkylated metabolites GS 26571 (2-amino-4-etert-butylamino-6-methoxy-1,3,5-triazine) and G 30033 (2-amino-4-chloro-6-ethylamino-1,3,5-triazine). The compounds were extracted into dichloromethane and quantitated by gas chromatography (GC) with nitrogen-specific detection. Selected results were verified by GC with mass fragmentographic detection. Limit of detection was usually 0.4 mg/m3; 80 percent of all results were below 0.4 mg/m3, 14 percent were 0.4-1 mg/m3, 6 percent were 1-10 mg/m3, and 0.3 percent were higher than 10 mg/m3. Detectable residues were mainly atrazine from the downstream sampling sites. Residues usually peaked during June.     

Measurement of simazine residues in chickpeas,Cicer arietinum,by gas–liquid chromatography

A method is described for the measurement of simazine [2-chloro-4,6-bis(ethylamino)-1,3,5-triazine] residues in chickpeas (Cicer arietinum). Ground chickpea samples were extracted with dichloromethane, followed by clean-up on alumina. Gas-liquid chromatography using metribuzin [4-amino- 6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one] as internal standard with thermionic detection was used to quantify simazine residues. The limit of detection was 0.02 mg kg^?1 and the recoveries of simazine from chickpea samples (0.1–4 mg kg-1) averaged 92%.     

The breakdown of the triazine herbicide cyanazine in wheat and potatoes grown under indoor conditions in treated soils

The breakdown of the triazine herbicide cyanazine (“BLADEX”,^a 2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine) has been studied in spring and winter wheat and potatoes grown under indoor conditions in soils treated at planting with up to 1.5 kg/ha of the radiolabelled herbicide. Breakdown products were mainly those formed by hydrolysis of the cyano group to give an amide ( II ) and an acid ( III ) followed by hydrolysis of the chlorine to hydroxyl ( IV ). De-N-alkylation reactions also occurred although these were less evident in soils. In wheat the chloro acid ( VII ) formed by the des-ethylation of ( III ) was more evident than in previous studies with maize. In all of the crops at harvest the residues were mainly of the hydroxy acids ( IV ) and ( VIII ); ( IV ) 2-hydroxy-4-(1-carboxy-1-methylethylamino)-6-ethyl-amino-1,3,5-triazine; ( VIII ) 2-hydroxy-4-(1-carboxy-1-methylethylamino)-6-amino-1,3,5-triazine, respectively. In potatoes and spring wheat they were present in both free and conjugated forms whereas in winter wheat they were almost entirely in conjugated forms. The compounds (IV) and (VIII) are of a low order of toxicity to animals and are not herbicidal. They are unlikely to present a residue hazard if present in field crops.     

DIFFERENTIAL PHYTOTOXICITY OF ATRAZINE AND AMETRYNE TO BANANAS*

Summary. In field screening trials for bananas (Musa acuminata var. Dwarf Cavendish) in Hawaii, ametryne (2-methylthio-4-ethylamino-6-isopropylamino-s-triazine) was less phytotoxic to bananas than atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine). Sand culture experiments showed that both herbicides were equally injurious to banana plants. Differential degradation of the herbicides by the plants did not account for the phytotoxicity observed. Both herbicides were partly metabolized by the plant to their common hydroxyl derivative (hydroxyatrazine) and two other unidentified metabolites after 3 and 7 days of exposure to nutrient solution containing ¹⁴C-labelled ametryne and atrazine. Phytotoxicity was directly related to leachability of the herbicides and negatively related to adsorption capacity of each soil for the herbicides. Organic matter content seemed to be correlated to the response observed. It was postulated that phytotoxicity in the field may have been attributed to differential location of the herbicide in relation to the roots.     

The breakdown of the triazine herbicide cyanazine in soils and maize

Radioisotope techniques have been used to study the breakdown products that are formed from the herbicide cyanazine ( BLADEX )^a, 2-chloro-4-(1-cyano-1-methylethyl-amino)-6-ethylamino-1,3,5-triazine, in soils and in maize grown in the soils under indoor conditions. In soils of different types cyanazine broke down mainly by conversion of the nitrile group to amide ( II ) and then to an acid ( III ) followed by hydrolysis of the ring chlorine to hydroxyl ( IV ). Dealkylation reactions occurred to only a limited extent in soils. In maize plants grown in treated soils the hydrolysis products, the amide ( II ) and the hydroxy acid ( IV ) were detected as well as appreciable quantities of products ( VI ) and ( VIII ) formed from these by loss of the N-ethyl group. In plants the hydroxy acids ( IV ) and ( VIII ) were present in the free form and there was also evidence for conjugates which were not identified but could be converted to these hydroxy acids, ( IV ) and ( VIII ), on treatment with acids. In these indoor studies the major residues appear to be the hydroxy acid ( IV ) in soils and ( IV ) and its dealkylated analogue ( VIII ) in plants grown in treated soils. These compounds are not herbicides and are of a low order of toxicity to mammals.     

THE DEGRADATION OF TRIAZINE AND URACIL HERBICIDES IN SOIL*

Summary. The rates of degradation of three triazine and two uracil herbicides were followed at 13·2 and 31·2°C in one soil. Soil was treated with 8 ppm of 2-chloro-4-ethyl-amino-6-isopropylamino-1,3,5-triazine (atrazine), 2-chloro-4,6-bisethylamino-1,3,5-triazine (simazine), 2-mcthylthio-4-ethylamino-6-isopropylamino-1,3,5-triazine (ametryne), 3-sec-butyl-5-bromo-6-methyluracil (bromacil) and 3-tert-butyl-5-chloro-6-methyluracil (terbacil) and monthly samples analysed chemically to determine the amounts remaining. Evaluation of the rate constant at two temperatures permitted calculation of the energy of activation from the Arrhenius equation. It was determined to a first approximation that soil degradation followed a first order rate law with no lag period and that the rate could be related to molecular structure. The energies of activation in kcals/mole were: atrazine 10-8, simazine 9-2, ametryne 6-1, bromacil 3-0, and terbacil 6-1. These values suggest breakage of the common carbon-chlorine bond in atrazine and simazine but breakage of a different bond in ametryne. Examination of bond energies and known mechanisms of breakdown for triazines supported the hypothesis of breakage of the bond at the two position. The data on decomposition of the uracils indicate that the carbon-halogen bond was broken in each molecule. Dégradation des triazines et des uraciles herbicides dans le sol Résumé. Les taux de dégradation de trois triazines et de deux uraciles herbicides ont été observés α 13,2 et 31,2° C dans un sol. Ce sol a été traitéà la concentration de 8 ppm avec la 2-chloro-4-éthyIainino-6-isopropylamino-1,3,5-triazine (atrazine), la 2-chloro-4,6-biséthylamino-l,3,5-triazine (simazine), la 2 méthylthio-4-éthylamino-6-isopropylamino-1,3,5-triazine (amétryne), le 3-sec-butyl-5-bromo-6-méthyluracile (bromacil) et le 3-tert-butyl-5-chloro-6-méthyluracile (terbacil). Des échunlillons ont été analysés chimiquement tous les mois pour déterminer les résidus. L'évaluation du taux constant à deux températures a permis le calcul de l'energie d'activation d'aprés l'équation d'Arrhenius. Selon une premiére approximation, la dégradation a suivi une loi de taux de premier ordre sans période de retard et le taux peut être reliéà la structure moléculaire. Les énergies d'activation en kcals/mole furent: atrazine 10,8, simazine 9,2, amétryne 6,1, bromacil 3,0 et terbacil 6,1. Ces valeurs suggérent une rupture d'une liaison carbone-chlore dans I'atrazine et la simazine mais la rupture d'une liaison différente dans l'amétryne. L'examen des énergies de liaison et des mécanismes connus de dégradation pour les triazines amène à formuler l'hypothése de la rupture d'une liaison en position deux. Les résultats relatifs aux uraciles indiquent tjue la liaison carbone-halogéne a été rompue dans chaque molécule. Der Abbau von Triazin- und Uracilherbiziden im Boden Zusammenfassung. Die Abbaurate von 3 Triazin- und 2 Uracilherbiziden im Boden wurde bei 13,2 und 3l,2°C untersucht. Aus dem mit 8 ppm 2-Chlor-4-athylamino-6-isopropylamino-1,3,5-triazin (Atrazin),2-Chlor-4,6-bisathylamino-[3,5-lriazin (Simazin), 2-Methyllhio-4-athylamino-6-isopropylamino-1,3,5-triazin (Ametryn), 3-scc-Butyl-5-brom-6-methyluracil (Bromacil) und 3-tert-Butyl-5-chlor-6-methyluracil (Terbacil) behandelten Bodenrückständen wurden monatlich Proben entnommen und chemisch die Rückstände erniittelt. Die Bestimmung der Geschwindigkeitskonslantcn bei zwei Temperaturen eriaubte die Borechnung der Aktivicrungscnergic nach der Arrhenischen Gleichung. In erster Annäierung verlief der Abbau als Prozcss erster Ordnung ohne Latenzphase und die Abbaurate stand in Beziehung zur Struktur des Molekuls. Die Aktivierungsenergie betrug fur Atrazin 10,8, Simazin 9,2, Ametryn 6,1, Bromacit 3,0 und Terbacil 6,1 kcal/Mol. Diese Werte lassen für Simazin und Atrazin einen Bruchder der bcide Herbizide gemeinsamen Kohlensloff-Chlorbindung vermuten, wahrend im Falle des Ametryn eine andere Bindung hiervon betroffen war. Die Prufung der Bindungsenergien und der bekannten Abbau me chanismen bei Triazinen unterstCitzcn die Hypothcse, dass der Bruch in der 2-Position erfolgte. Die Ergebnisse fur die Uracile deuten darauf hin, dass bei beiden Moleküien der Abbau an der Kohlenstoff-Halogenbindung ansetzte.     

Atrazine metabolism in resistant and susceptible biotypes of Chenopodium album L., Chenopodium strictum Roth., and Amaranthus powellii S. Wats.

The metabolism of atrazine was studied in resistant and susceptible biotypes of Chenopodium album L., Chenopodium strictum Roth., and Amaranthus powellii S. Wats. Both biotypes metabolized atrazine by N-dealkylation, hydroxy lation at the 2-position and conjugation. In addition, binding of mono-N-dealkylated atrazine with plant constituents to form nonextractable (bound) residues was also observed. Although parent atrazine levels were similar in the shoots and roots of both biotypes of the three weed species, the resistant biotype in each case contained a higher level of polar conjugates and bound residues in the plant tissues. In contrast, presence of a phytotoxic metabolite, namely 2-chloro-4-amino-6-isopropylamino-s-triazine, was only observed in the susceptible biotype of the three weed species.     

Cyanazine metabolism in corn,fall panicum,and green foxtail*

The metabolism of cyanazine (2-chloro-4-(1-cyano-1-methyl-ethylamino)-6-ethylamino- 1,3,5-triazine) by corn (Zea mays, L.), fall panicum (Panicum dichotomiflorum Michx.), and green foxtail (Setaria viridis L.) was compared. Cyanazine metabolism by plants at the four-leaf stage was examined by thin-layer chromatography following foliar or root treatments with ¹⁴C-cyanazine. Five days following foliar ¹⁴C-cyanazine applicalion, fall panicum and green foxtail contained a larger number of water- and chloroform-soluble metabolites than corn, whereas, following root treatment, the opposite was true. Corn rapidly hydrolysed the nitrile group and hydroxylated the two-position on the triazine ring. Accumulation of the dealkylated cyanazine was evident in green foxtail, the most susceptible of the species studied. Metabolism of cyanazine supplied to the roots appeared to differ from foliar treatments in the weed species as more unchanged cyanazine was recovered. Rapid metabolism of cyanazine by corn roots provided evidence for an active cyanazine detoxication mechanism in the roots.     

Triazine absorption by excised corn root tissue and isolated corn root protoplasts

Absorption of four triazine herbicide analogs [ametryn (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine), atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine), atratone (2-methoxy-4-(ethylamino)-6-(isopropylamino)-s-triazine), and hydroxyatrazine (2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine)] was compared using excised corn (Zea mays L.) root segments and isolated corn root protoplasts. The tissue absorbed ametryn, atrazine, and atratone for only 20 min. Ametryn and atrazine permeated tissue to passive equilibrium with the ambient solution in 10 min. Atratone permeated to 65 and 82% of passive equilibrium in 10 and 30 min, respectively. In contrast, hydroxyatrazine concentration in tissue was only 15 and 70% of the ambient concentration at 30 min and 24 hr, respectively. However, hydroxyatrazine permeated frozen/thawed tissue to 90% of passive equilibrium in 10 min. Protoplast absorption of ametryn and atratone was complete in 10 sec; hydroxyatrazine absorption by protoplasts did not reach a plateau until 5 min. Protoplasts absorbed the triazines to greater than passive equilibrium. Three kinetically homogeneous pools were detected for ametryn, atrazine, and atratone, whereas elution of hydroxyatrazine produced four pools. The three pools for atrazine were confounded by metabolism of atrazine to hydroxyatrazine. Pools for the triazines could not be identified as the free space, cytoplasm, and vacuole as proposed previously for mineral ions. Although the plasma membrane impeded diffusion of hydroxyatrazine, all analogs penetrated into the symplast.