Relationships between substituted urea herbicides and soil urease activity

Fenuron, monuron, diuron, siduron, linuron and neburon were tested for their inhibition of soil urease activity in order to investigate relationships between fertilizers and herbicides. The inhibition of urea hydrolysis in the selected soils was 10–33% for fenuron, 10–39% for monuron, 10–35% for diuron, 8–38% for siduron, 9–36% for linuron and 12–30% for neburon. In the field greater effects might be expected since the fertilizer/herbicide ratio would be lower than the one considered here. Some agronomic aspects of the relationship between fertilizers and herbicides are discussed.     

THE ADSORPTION OF UREA AND SOME OF ITS DERIVATIVES BY A VARIETY OF SOILS

Summary. The absorption of urea and a number of its derivatives by different soils was investigated using a slurry-type procedure. The materials could be listed in the following order of increasing tendancy to be adsorbed: urea, fenuron, methylurea, phenylurea, monuron, monolinuron, diuron. linuron, neburon and chloroxuron. Both N -aryl and N -alkyl substituents appeared to play a part in adsorption. Increasing chain length in the alkyl substituents and chloro- and chlorophenoxy substitution in the aryl substituent increased adsorption. There was no relationship between adsorption and water solubility.
Organic matter content was the only soil property that could be related to adsorptive capacity. The evidence of Langmuir isothermal equilibrium plots suggests that only a fraction of the total soil surface is available for the adsorption of substituted ureas.
L'adsorption Je l'uré de ses dérivés sur dfférents sols     

The herbicidal activity of 3-substituted 1-phenylureas

A variety of 1-phenylureas, substituted in the 3-position with one acyl, alkoxycarbonyl or cyano group, and optionally with a lower alkyl group, have been synthesised and assessed for pre- and post-emergence herbicidal activity against a range of monocotyledonous and dicotyledonous weed species. Generally, activity was associated only with compounds containing two small substituents in the 3-position. Their possible metabolic fate is discussed in the light of comparisons with the activity of the commercial herbicides, fenuron, monuron and diuron, and their de-methylated derivatives.     

A rapid bioassay for the detection of photosynthesis inhibitors in water

A modified leaf disc buoyancy procedure for the detection of photosynthesis-inhibiting residues in water is described. The modifications proposed, mainly the presence of sodium hydrogen carbonate in the infiltration solution, increased the sensitivity of the method and reduced the time required. The substituted urea and 1,3,5-triazine herbicides diuron, linuron, monuron, atrazine, ametryn and atraton were detected below 0.7 mg litre^?1 using cucumber (Cucumis sativus L., cv. ‘Dalia’) leaf discs. A concentration as low as 0.09 mg diuron litre^?1 could be detected. Although bean (Phaseolus vulgaris L., cv. ‘Bulgarian’) leaf tissue was less sensitive in this bioassay than cucumber, 0.3 mg diuron litre^?1 could still be detected. The test, being very rapid (less than 30 min per determination) and relatively sensitive, could be used for the detection of photosynthesis inhibitors in recycled water used for irrigation.     

THE DECOMPOSITION OF UREA HERBICIDES BY BACILLUS SPHAERICUS, ISOLATED FROM SOIL

Summary. The decomposition of seven urea herbicides by Bacillus sphaericus was studied. Experiments with ¹⁴C-labelled monolinuron demonstrated that monolinuron was degraded by removal of CO₂ from the ureido portion of the molecule and leaving the /Kchloroaniline moiety. Tests with monuron, diuron, monolinuron, linuron, metobromuron, fluometuron and methabenzthiazuron indicated that B. sphaericus was only able to decompose the methoxy compounds monolinuron, linuron and metobromuron in this way. All compounds were identified by infrared spectroscopy. A pathway for degradation of the herbicides by B. sphaericus is proposed.     

Studies on a mixed bacterial culture from soil which degrades the herbicide linuron

A stable mixed bacterial culture which degrades the herbicide linuron was isolated from soil by enrichment with linuron in a liquid mineral medium. Radio-respirometry studies showed that the culture mineralised linuron completely. No intermediate degradation products were detected in the medium. The culture was able to utilise linuron as a source of both nitrogen and carbon and was also able to degrade the related herbicides monolinuron and chlorbromuron and the possible intermediate degradation products of linuron: 3,4-dichlorophenyl-l-methylurea, 3,4-dichlorophenylurea and 3,4-dichloroaniline. The culture was unable to degrade the 1,1-dimethyl substituted ureas monuron, diuron or metoxuron. The culture contained Gram-negative aerobic rods, and Gram-positive aerobic non-spore-forming rods and cocco-bacilli. Of 124 isolates from the mixed culture, none degraded linuron in pure culture, indicating that a consortium of organisms is involved. Further investigation suggested that Pseudomonas spp. were important components of the population responsible for degradation.     

Long-term effects of herbicides on the photosynthetic apparatus I. Influence of diuron, triazines and pyridazinones

Long-term effects of herbicides on the photosynthetic membrane system were investigated. For this purpose the unicellular alga Bumilleriopsis filiformis was grown in liquid culture in the presence of sublethal concentrations of diuron, atrazine, metribuzin, and some substituted pyridazinones. This allowed reproducible growth conditions, exact dosing of herbicides, and also the preparation of functionally active cell-free photosynthetic systems. The electron transport system of cells grown in the presence of ureas and triazine derivatives is not impaired at all, wherea scultivation with pyridazinones damages their photosynthetic redox system. In addition, a strong bleaching effect is observed, whereas the first group of herbicides enhance chlorophyll formation.     

Herbicidal phenylalkylureas as possible mutagens: II. Chemical basis of mutagenic activity

The herbicide monuron (N-(4-chlorophenyl)-N′, N′-dimethylurea)—a recognized carcinogen—and some of its congeners have been found also to induce back mutations in Salmonella typhimurium (Ames test), as well as micronuclei in mouse bone marrow cells and an inhibition of testicular DNA synthesis (DSI test) in mice. As both the Ames test and the DSI test correlate well with chemical carcinogenicity, urea herbicides in general might be suspected of carcinogenic activity. In order to investigate the potential carcinogenic mode of action of these substances we looked for possible activation mechanisms. The reaction sequence N-oxidation-esterification-carbonium ion formation seemed the only one able to fit the observed structure-activity relationships. Chemical synthesis of the proposed N-acetoxy compounds provided the means for testing this hypothesis. Only the N-acetoxy-, but neither the N-hydroxy- nor the unchanged parent ureas, exhibited a direct alkylating action as measured by the NBP-assay. The DSI reactivity pattern of several positional isomers could be shown to coincide with the theoretical predictions, as did the stability of the chloroisomers in aqueous solution at pH 7. Furthermore the N-acetoxy derivatives could be demonstrated to behave in the Ames test as directly acting mutagens, while the activity of the parent compounds is dependent on the metabolic activation by an S-9-liver fraction. The enhancing action of Acetyl-CoA on the S-9 mediated mutagenicity of these ureas can then be regarded as the final proof for the proposed reaction sequence.     

ABSORPTION AND TRANSLOCATION OF HERBICIDES BY THOMPSON SEEDLESS (SULTANINA) CRAPE, VITIS VINIFERA L.

Summary. Absorption and translocation of ¹⁴C-labelled herbicides applied in culture solutions lo the roots and in concentrated drops to mature leaves of 'Thompson Seedless' (Sultanina) cuttings were studied. Neither 2,4-D nor paraquat, and only traces of 2,4,5-T translocated from the roots to the shoot. Dicamba, amitrole, diuron, monuron, simazine and atrazine readily moved from the roots to the shoots. The substituted ureas and s -triazines were mobile only in the xylem or cell walls (apoplast), while dicamba and amitrole were mobile in the apoplast and symplast (living protoplasm). Both 2,4-D and 2,4,5-T moved almost entirely in the symplast. Paraquat moved only slightly in either apoplast or symplast. Stability of the herbicides in the plants varied, as judged by the detection of label in ethanol-insoluble products. Dicamba was considerably more stable than 2,4,5-T which, in turn, was more stable than 2,4-D. Diuron was more stable than either atrazine or simazine. Amitrole largely was converted into ethanol-insoluble products in 30 days. Paraquat was not extractable with ethanol.
Absorption et migration d'herbicides chez une vigne: Thompson Seedless (Sultanina), Vitis vinifera L.     

The effect of substituted urea herbicides on the growth of excised tomato roots

The action of 23 herbictdal substituted ureas on the growth of excised tomato roots was studied in order to détérmine whether there is a link between the effects of these herbicides on oxidative phosphorylation and on the growth of non-photosynthetic tissues. Fourteen of these herbicides were inhibitory; chlortoluron and TBU were stimulatory but only in the light. Substituted ureas known to affect plant mitochondria inhibited root growth but to a lesser extent than some which had no action on mitochondria. No clear relationship was found between actions on mitochondria and on root growth. It is suggested that targets other than photosynthesis and oxidative phosphorylation exist for some substituted ureas.     

The algaecidal activity of some substituted 1,3-diphenylureas, 1-phenyl-3-(2-pyridyl)ureas and the corresponding thioureas

Twelve ureas and thioureas with 1,3-diphenyl- and 1-phenyl-3-(2-pyridyl) were tested as potential herbicides in a simple screen against two species of algae Chlorella fusca and Anabaena variabilis. Several were shown to inhibit growth at 100 mg litre^?1 but only 1-[2,4-bis(azidosulphonyl)phenyl]-3-(2-pyridyl)urea and 1,3-bis(4-isopropyl- idenehydrazinosulphonylphenyl)thiourea showed any activity at 1 mg litre^?1. This compares with the well-established urea herbicide diuron which, in identical tests, gives similar inhibition of growth at concentrations as low as 0.01 mg litre^?1.     

CHEMICAL WEED CONTROL IN SPRING-SOWN BROAD BEANS

Summary. During the period 1956-61, twelve replicated field experiments were conducted to determine the response of spring-sown broad beans ( Vicia faba L.) and annual weeds to various pre- and post-emergence herbicides. On a sandy loam, the best results were given by pre-emergence applications of simazine 0.75 lb/ac, trietazine 1.5 lb/ac, chlorpropham 1 lb+diuron 0.2 lb/ac or dinoseb-amine 4 lb/ac. Amiben proved insufficiently selective, while chlorpropham+fenuron caused greater crop injury than the corresponding mixture with diuron. Post-emergence application of dinoseb-amine was less satisfactory than the best of the pre-emergence treatments.
Le désherbage chimique des fèves semées au printemps     

HERBICIDES AS FERTILIZER ADDITIVES

Summary. Granulated compound fertilizers were tested as solid carriers for a variety of herbicides known to be active when applied as liquids.
Pasture and cereal experiments with 2,4-D and MCPA as fertilizer additives indicated considerable loss of herbicidal activity in comparison with spray formulations.
Residual herbicides such as TCA, propham and diuron retained their activity when added to fertilizer for application to root crops. The most effective of the herbicides used as fertilizer additives were TCA and propham, both of which gave good control of Avena fatua in sugar beet, and a mixture of chlorpropham and diuron gave promising results as a general weed control treatment in carrots.
It is concluded that the addition of these or similar herbicides to fertilizer granules may have advantages over conventional spray formulations for those crops which require broadcast pre-sowing applications of herbicides and fertilizer. For such crops the use of a granular fertilizer as the carrier instead of inert material could also have advantages over conventional granular herbicides, particularly by reducing transport and application costs.     

Effect of different photosystem II inhibitors on chloroplasts isolated from species either susceptible or resistant toward s-triazine herbicides

In chloroplasts isolated from susceptible and atrazine-resistant Amaranthus retroflexus, the inhibition of photosynthetic electron transport by various classes of herbicides has been investigated. Resistance of mutant Amaranthus is not restricted to s-triazines but also extends to uracils, 1,2,4-triazine-5-ones, and ureas. For 1,2,4-triazin-5-ones and chloroplasts of both biotypes, a correlation between inhibition of photosynthetic electron transport and the partition coefficient could be established. In the case of phenolic herbicides only modestly decreased or even higher sensitivity of chloroplasts from the resistant biotype as compared to the susceptible one could be observed. These results are confirmed by binding of radioactively labeled herbicides to chloroplasts of both plants. Specific binding of atrazine or metribuzin to resistant chloroplasts is completely abolished, and that of diuron or phenisopham diminished as compared to susceptible chloroplasts. In contrast, binding of phenolic herbicides generally is enhanced in resistant chloroplasts. Photoaffinity labeling of thylakoids from both biotypes by 2-azido-4-nitro-6-[2′,3′-³H]isobutylphenol yields almost identical labeling patterns. These results are consistent with a recently proposed model (W. Oettmeier, K. Masson, and U. Johanningmeier, Biochim. Biophys. Acta679, 376 (1982) of two different herbicide binding proteins at the reducing side of photosystem II: a 32- to 34-kdalton protein responsible for binding of triazines, triazinones, ureas, and related herbicides and a photosystem II reaction center protein for binding of phenolic herbicides.     

不同控氮比掺混肥对土壤无机氮与脲酶及冬小麦产量的影响

开展田间小区试验,研究了控释氮肥与尿素掺混施用对土壤无机氮与脲酶及冬小麦产量的影响,旨在寻求控释氮肥与尿素最佳掺混比例,提出缓解氮肥损失、降低面源污染、节约成本、易于推广的施肥方式。结果表明:较常规尿素处理,控释氮肥与尿素掺混对土壤铵态氮含量影响总体差异不显著;在小麦分蘖期,常规尿素处理土壤硝态氮含量和土壤脲酶活性较高,而小麦拔节期至成熟期,则以掺混40%比例以上控释氮肥处理的土壤硝态氮含量和脲酶活性较高;各施氮处理对小麦穗粒数和千粒重影响差异不显著,产量以掺混40%控释氮肥处理最高,较常规尿素处理增产14%,因产值最高,投入成本适中,净收入水平和产投比均为最高,分别为5 875.72元·hm~(-2)和2.24,较常规尿素处理提高了23.24%和9.27%。综上,40%控释氮肥与60%尿素掺混处理在提高土壤无机氮含量,激活小麦生长中、后期脲酶活性,增加冬小麦产量方面效果显著。     

Inhibition of Tribolium gut chitin synthetase

The chitin synthetase (CS) of Tribolium castaneum gut is inhibited 50% by 0.02 μM nikkomycin and 4 μM polyoxin D, two pyrimidine nucleoside fungicides, in in vitro assays with 10-min preincubation of enzyme and inhibitor prior to substrate addition. Tribolium CS is also sensitive to inhibition by the pyrimidine nucleotides uridine and cytidine di- and triphosphates. Captan, a known inhibitor of insect chitin synthesis, and the related fungicides captafol and dichlofluanid are highly potent inhibitors of Tribolium CS. Moderately active CS inhibitors are the acaricide oxythioquinox and the herbicide barban. One phenylcarbamate insect growth reatardant, H-24108, is weakly active in inhibiting Tribolium gut CS, as are three of its analogs but not 26 others. Many triazines are not inhibitory including several herbicides and an azido derivative, CGA 19255, which is active in blocking insect growth and chitin synthesis. Although the benzoylphenyl urea insecticides diflubenzuron and SIR 8514 are potent in vivo inhibitors of the polymerization step in insect chitin synthesis, they do not affect T. castaneum gut CS activity in vitro and greatly stimulate Tribolium brevicornis gut CS activity in vivo. These studies and preliminary findings on an integumental enzyme indicate that CS of these tissues is not sensitive to the direct action of benzoylphenyl ureas. This leads to speculation that the benzoylphenyl ureas act either as CS inhibitors via active metabolites formed in the integument or as blocking agents by direct binding to non-CS sites important in chitin polymerization and fibrillogenesis.     

Detection of halogenated biphenyls from sunlight photolysis of chlorinated herbicides in aqueous solution

A survey study was conducted to determine the generality of chlorinated biphenyl formation from the photolysis of chlorine-containing herbicides in aqueous solution. Seven herbicides from the phenylurea, anilide and carbamate classes were examined. In this study, the photoreaction under investigation proceeded via the coupling of two herbicide molecules to yield a chlorinated biphenyl with concomitant loss of hydrogen chloride. In preliminary studies using ultraviolet lamps, 4-chlorophenyl methylcarbamate (PPG-124) gave a chlorinated biphenyl with only one carbamate side chain, and chlorpropham gave no chlorinated biphenyl, but rather a hydroxylated biphenyl. Employing ultraviolet lamps or natural sunlight, photolyses of monuron, diuron, linuron, metobromuron and propanil produced halogenated biphenyls according to the photocoupling reaction under investigation. All yields of chlorinated biphenyls from sunlight photolysis were approximately 1% or lower.     

Structure-activity relationship of herbicides inhibiting ACh-induced contractions in a molluscan smooth muscle

Certain herbicides are known to influence the muscle function of molluscs. The penis-retractor muscle complex (PRM complex) of the edible snail, Helix pomatia, is a suitable test object for studying these side effects in smooth muscle, because sequential contractions can be induced in vitro by adding and removing acetylcholine (ACh). In the presence of herbicidal amides, carbamates, and ureas (concentration, 10^?4 mol/liter) the muscle tension was found to be reduced to a variable extent. In contrast, the relaxing effect of herbicidal phenoxycarbonic acids was weak. The inhibitory properties of the herbicides tested were correlated with the electron-withdrawing properties of certain substituents. These substituents are bound to an amino function. Their structure is either aromatic (amides, biscarbamates, carbamates, ureas), aliphatic (thiocarbamates), or cycloaliphatic (cycloat). The structure-activity relationship is comparable with that found for herbicidal activity in plants.     

Sites of action of photosynthetic inhibitor herbicides; Experiments with trypsinated chloroplasts

The effect of four photosynthetic inhibitor herbicides, bromacil, ioxynil, metribuzin and monuron, on chloroplast electron transport was investigated. All four compounds completely inhibited electron flow with tripotassium hexacyanoferrate as oxidant, but the inhibition caused by bromacil, metribuzin and monuron was almost totally reversed by trypsin treatment. With ioxynil, only a partial degree of reversability was shown. With a molybdosilicate as oxidant, electron transport was not completely inhibited by any of the herbicides. Whereas the partial inhibition was reversed by tryptic digestion in the presence of bromacil, metribuzin and monuron, there was virtually no reversal in the presence of ioxynil. The results suggest a common site of action for all four herbicides and an additional site for ioxynil nearer to photosystem II.     

Microbial demethylation and debutynylation of four phenylurea herbicides

Rhizopus japonicus demethylates the herbicides monuron, fluometuron, and monolinuron into the metabolites 3-(p-chlorophenyl)-1-methylurea (V), 3-(m-trifluormethylphenyl)-1-methylurea (VI), and 3-(p-chlorophenyl)-1-methoxyurea (VII), respectively. Buturon loses its N-(1-methyl-2-propynyl) group to give compound V. These metabolites, which were identified by nuclear magnetic resonance and mass spectrometric analysis accumulate after a 1-wk growth.