Orientador: Ciro Cesar Zanini Branco / Coorientador: Ciro Cesar Zanini Branco / Banca: Anna Isabel Nassar Bautista / Banca: Orlando Necchi Junior / Banca: Jorge Laço Portinho / Banca: Celia Leite Sant'Anna / Resumo: Herbicidas podem atingir ambientes aquáticos em regiões agrícolas, afetando os produtores primários e, consequentemente, a teia trófica e a ciclagem de nutrientes. Neste contexto, macroalgas lóticas do filo Chlorophyta foram coletadas, cultivadas, e submetidas a três concentrações diferentes (0,28; 3,5; e 6 mg L-1) de glifosato grau técnico e da formulação comercial Roundup®, e uma concentração (0,03 mg L-1) de ácido aminometilfosfônico (AMPA), além do grupo controle (0 mg L-1), para a avalição da resposta fotossintética através da evolução do oxigênio dissolvido, da fluorescência da clorofila a, e da concentração de clorofila a, realizados após um e sete dias de exposição ao herbicida. Os resultados mostram que, no geral, o Roundup® foi o herbicida que mais afetou negativamente as respostas fotossintéticas das macroalgas testadas, gerando danos ao aparato fotossintético, provocando reduções na taxa de fotossíntese líquida, e na concentração de clorofila a. O glifosato grau técnico e o AMPA também causaram efeitos inibitórios significativos para a resposta fotossintética, ainda que em uma escala menor. Em relação às concentrações utilizadas, a concentração de 0,28 mg L-1, que corresponde ao limite permitido pela legislação brasileira para a água destinada a irrigação e consumo animal, gerou reduções efetivas na resposta fotossintética de Nitella microcarpa var. wrightii (Roundup®) Nitella subglomerata (glifosato grau técnico e Roundup®) e Desmidium grevillei (Roundup®). A con... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Herbicides can contaminate aquatic environments in agricultural regions, affecting primary producers and, consequently, the food web and nutrient cycling. In this context, lotic macroalgae of the phylum Chlorophyta were collected and cultivated in three different concentrations (0.28; 3.5; and 6 mg L-1) of technical grade glyphosate and Roundup®, and one concentration (0.03 mg L-1) of aminomethylphosphonic acid (AMPA), in addition to the control group (0 mg L-1). Were evaluated the photosynthetic response through the oxygen evolution, chlorophyll a fluorescence, and the chlorophyll a concentration, performed with one and seven days of exposure to the herbicide. The results show that, in general, Roundup® was the herbicide most negatively affected the photosynthetic responses of macroalgae tested, causing damage to the photosynthetic apparatus, reducing the photosynthetic rates, and chlorophyll a concentration. Technical grade glyphosate and AMPA likewise caused significant inhibitory effects on the photosynthetic response, although on a smaller scale. About the concentrations used, the 0.28 mg L-1, which correspond to the limit for Brazilian law in water for irrigation and animal consumption, led to effective reductions in the photosynthetic response of Nitella microcarpa var. wrightii (Roundup®) Nitella subglomerata (glyphosate technical grade and Roundup®) and Desmidium grevillei (Roundup®). The concentration of 0.03 mg L-1 used in the AMPA treatment also inhibited the phot... (Complete abstract click electronic access below) / Doutor

Quizalofop-p-ethyl is a herbicide introduced in the mid 1980's with apparent low toxicity and is readily degradable.Quizalofop-p-ethyl is a member of the aryloxyphenoxypropionate group of herbicides and is a postemergence herbicide used for pulses (including soybean) and vegetables. The aim of the project discussed in this study is to develop an analytical method for the sensitive and reliable determination of quizalofop-p-ethyl and quizalofop acid in soybean using HPLC. Soybean is chosen as a typical agricultural crop. It has 15 to 20 percent oil content and is a crop which has been successfully used with theis herbicide.Two different methods of extraction, i.e. the solvent-solvent extraction method and solid phase extraction method, and clean up are discussed in some detail. / Doctor of Philosophy (PhD)

Four main series of novel heterocyclic compounds were successfully syniliesised. Two of these series were found to be post-emergence herbicides with the activities of each being based on a different mode of action. The (pyrazole-4-yl)alkanones are inhibitors of protoporphyrinogen oxidase, an enzyme in chlorophyll biosynthesis, whereas alkyl 3-arylsulfonylamino- 3-methyllhio-2-(pyrimidin-2-ylcarbamoyl)acrylates and pyrimidin-2-yl 3-(2- chlorophenyl)sulfonyl-amino-3-methylthio-2-cyanoacrylamides (collectively termed "vinylogous sulfonylureas") are inhibitors of acetohydroxy acid synthase (AHAS). an enzyme in branched-chain amino acid biosynthesis. Both these enzymes are established targets for current commercial herbicides. Studies of the utility of 2-(l-ethoxyalkylidene)-3-oxoaIkanenitriles (acrylonilriles) in heterocycle synthesis were facilitated by the recent development of a convenient route to these starting materials. Acrytonitriles were reacted with different hydrazines to give (pyrazol-4-yl)alkanones and pyrazole-4-carbonitriles in varying proportions depending on the reaction conditions and the substituents on the reactants. Although distinction between alternative 3- and 5-substituted pyrazoles is a perennial problem in pyrazole synthesis, in this case the products of these reactions were successfully characterised and identified using a range of n.m.r. spectroscopy techniques. Once the herbicidal mode of action of the (pyrazol-4-yl)alkanones had been confirmed, synthesis of a series of analogues allowed the structural elements contributing to biological activity to be identified. The reaction of acrylonitriles with bidetate nucleophiles such as thiourea gave novel pyrimidines. but these compounds were not herbicidal. The vinylogous sulfonylureas were synthesised using established procedures to obtain novel compounds structurally related to the commercial herbicide chlorsulfuron. The biological activity of the vinylogous sulfonylureas was found to be sensitive to apparently minor changes in structure, but x-ray crystallographically-generated structures of an active and an inactive member of the series revealed marked differences in conformation. Some of the vinylogous sulfonylureas were used as synthons for pyrazole and pyrazolopyrimidine derivatives. Although these compounds did not exhibit herbicidal activity, this synthesis provided the basis for some interesting chemistry. Unexpected elimination of the arylsulfonylamino group was observed when a vinylogous sulfonyurea was treated with methyl hydrazine. In order to confirm the identity of the 3-methylthiopyrazole product, model compounds were synthesised using alternative routes. The resulting pairs of 3- and 5-substituted pyrazoles were characterised using n.m.r spectroscopy.

The use of herbicides in cropping systems is routine in western Canada as is the practice of rotating crops between cereals, oilseeds and pulse crops. Often, herbicides that are appropriate one year in the crop rotation are not compatible with the following crop. Additionally, certain herbicides are designed to target certain enzyme pathways that can interfere with amino acid synthesis. These pathways also exist in the microbial community, including Rhizobium species. Rhizobia have a unique symbiotic relationship with legumes. In return for a carbon source, rhizobia not only fix atmospheric dinitrogen (N2) for the plant, but also can increase soil N reserves for the following year. With herbicides targeting amino acid synthesis in both plants and microbes, there is a possibility that N2 fixation may be inhibited by the application of certain herbicides.<p> This project was designed to examine possible negative effects of herbicide application on N2 fixation in field pea (Pisum sativum L.) and chickpea (Cicer arietinum L.). The study included field, growth chamber and laboratory experiments in which the effects of pre- and post-emergent herbicides, as well as herbicide residues in soil were examined.<p> In the field experiments, some early season measurements suggested that herbicide application had a negative impact on various growth and N2 fixation parameters. However, as the season progressed, plants recovered from early herbicide damage and N2 fixation ultimately was relatively unaffected. Growth chamber experiments similarly revealed that N2 fixation was largely unaffected by herbicide application when the application rates were relatively low (i.e., at rates intended to simulate partial herbicide breakdown, and thus lower than the recommended field rate). Although, N2 fixation was suppressed where high rates of herbicide (i.e., greater than recommended field rate) were applied, the efficiency of the rhizobia to fix N2, (i.e., the amount of N2 fixed per unit nodule mass), was unaffected. This along with a laboratory experiment which monitored growth of rhizobia in vitro, confirmed that rhizobia were not directly affected by the herbicides used in this study and that overall N2 fixation was not inhibited directly by the application of these herbicides. It was concluded that any negative impact on N2 fixation caused by herbicides used in this study, was related to the impact of the herbicide on crop growth, and was not due to any direct effects of the herbicide on the rhizobia.

The use of herbicides in cropping systems is routine in western Canada as is the practice of rotating crops between cereals, oilseeds and pulse crops. Often, herbicides that are appropriate one year in the crop rotation are not compatible with the following crop. Additionally, certain herbicides are designed to target certain enzyme pathways that can interfere with amino acid synthesis. These pathways also exist in the microbial community, including Rhizobium species. Rhizobia have a unique symbiotic relationship with legumes. In return for a carbon source, rhizobia not only fix atmospheric dinitrogen (N2) for the plant, but also can increase soil N reserves for the following year. With herbicides targeting amino acid synthesis in both plants and microbes, there is a possibility that N2 fixation may be inhibited by the application of certain herbicides.<p> This project was designed to examine possible negative effects of herbicide application on N2 fixation in field pea (Pisum sativum L.) and chickpea (Cicer arietinum L.). The study included field, growth chamber and laboratory experiments in which the effects of pre- and post-emergent herbicides, as well as herbicide residues in soil were examined.<p> In the field experiments, some early season measurements suggested that herbicide application had a negative impact on various growth and N2 fixation parameters. However, as the season progressed, plants recovered from early herbicide damage and N2 fixation ultimately was relatively unaffected. Growth chamber experiments similarly revealed that N2 fixation was largely unaffected by herbicide application when the application rates were relatively low (i.e., at rates intended to simulate partial herbicide breakdown, and thus lower than the recommended field rate). Although, N2 fixation was suppressed where high rates of herbicide (i.e., greater than recommended field rate) were applied, the efficiency of the rhizobia to fix N2, (i.e., the amount of N2 fixed per unit nodule mass), was unaffected. This along with a laboratory experiment which monitored growth of rhizobia in vitro, confirmed that rhizobia were not directly affected by the herbicides used in this study and that overall N2 fixation was not inhibited directly by the application of these herbicides. It was concluded that any negative impact on N2 fixation caused by herbicides used in this study, was related to the impact of the herbicide on crop growth, and was not due to any direct effects of the herbicide on the rhizobia.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 60-62). Also available on the World Wide Web.

Reproduction de : Thèse de doctorat : Chimie et microbiologie de l'eau : Poitiers : 2008. / Titre provenant de l'écran-titre. Bibliogr. 180 réf.

Herbicides are a common tool in weed control. With the introduction of genetically modified herbicide-tolerant crops, there has been a dramatic increase in the use of particular herbicides. Herbicides contaminate the environment and food and feed and can come into contact with non-target organisms, especially bacteria. Salmonella enteric serovar Typhimurium, which is a human and animal pathogen, was chosen to investigate if the commercial formulations of three herbicides – Kamba, 2,4-D and Roundup are toxic to bacteria and whether sub-lethal concentrations cause a response to antibiotics. In addition, earlier work demonstrating an effect of salicylic acid on antibiotic response was reconfirmed in this study. The herbicides were toxic to S. typhimurium at concentrations above the manufacturers recommended application rates. A key finding of this study was that when S. typhimurium was grown in sub-lethal concentrations of the herbicides, it demonstrated a change in its susceptibility to various antibiotics. Kamba and 2,4-D caused increased tolerance of chloramphenicol, tetracycline, ampicillin and ciprofloxacin and increased sensitivity to kanamycin. Exposure to Roundup caused increased sensitivity to chloramphenicol and tetracycline and increased tolerance towards kanamycin and ciprofloxacin. Roundup had no measureable affect on ampicillin susceptibility. The minimum concentrations of herbicides that induced an antibiotic response were within the recommended application rates. Furthermore, the minimum 2,4-D concentration that induced tetracycline, chloramphenicol and ampicillin tolerance was at or below the maximum residue limits set for food and feed commodities. Simultaneous exposure to an herbicide and an antibiotic was necessary for the induction of antibiotic tolerance. In addition, the effect of the herbicide on the antibiotic response was faster than the lethal effect of the antibiotics. Kamba induced chloramphenicol, tetracycline, ampicillin and ciprofloxacin tolerance was maintained in the absence of Kamba once tolerance was induced by simultaneous exposure to Kamba and antibiotic. The emergence of antibiotic tolerance is an important health issue that may compromise treatment of serious bacterial infections. The widespread use of herbicides in agricultural, urban and domestic settings increases the number of bacteria that are exposed to herbicides. The tolerance induced by the herbicides may increase the frequency of antibiotic tolerant strains, increase the chance of co-exposure to antibiotics, and increase the potential for failure to treat bacterial infections as a result.

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