Glyphosate-based herbicides are the dominant pesticide on the market and are utilized worldwide in both the agricultural and forestry industries. Their prevalence comes at a time when concern over the potential effects of pesticide application in amphibian spawning grounds is growing. The primary goal of this thesis was to determine if the glyphosate-based herbicide WeatherMax® has the potential to disrupt sexual differentiation and growth in the wood frog (Lithobates sylvaticus) in a pulse exposure at the predicted maximal environmental concentration (PMEC) of 2.88 mg acid equivalent per liter. This was carried out in laboratory, mesocosm and in-situ field exposures, in an attempt to determine how a potential disruption might vary between experimental environments. In this study, tadpoles from three split-wetlands targeted at the PMEC for WeatherMax were found to display no significant change in survival or growth, however gene expression of several genes involved in steroidogenesis during sexual differentiation (cyp19, cyp17, star, foxl2) were found to be affected. The effects on these genes appeared to be dependant on the exposure concentration of WeatherMax in each wetland, which varied even though all three wetlands were meant to target the PMEC. The wetland that was measured as having the highest herbicide concentration (PMEC 13) was found to have a female biased sex ratio. The results found in the field varied from those found in the more artificial exposures. In the laboratory the PMEC of WeatherMax experienced complete mortality, whereas in the mesocosms survival was not significantly affected. Sex ratios were unaffected in the laboratory, however at the PMEC there was a significant male bias in the mesocosms. The discrepancies in the results obtained from the different exposure types highlights the importance of real world exposures. That the same concentration that caused complete mortality in the laboratory caused sublethal effects in the field is of importance as it denotes that these endpoints may not be easily investigated in these synthetic exposures. This project is a part of the Long Term Experimental Wetlands Area (LEWA) and contributes to the body of information amassed therein on the impact of a glyphosate-based herbicide on amphibians in a wetland ecosystem.

Le module de transfert de pesticide PeStics a été intégré au sein du modèle agronomique STICS (Simulateur mulTIdisciplinaire pour les Cultures Standard) afin de simuler le transfert de pesticides dans les sols agricoles. Par la suite une évaluation sur trois sites expérimentaux a été effectuée. Afin d'étudier le devenir des pesticides à l'échelle du bassin versant de l'Orgeval, des simulations concernant 4 herbicides (l'atrazine, la simazine, l'isoproturon, le chlortoluron) et un métabolite (la DEA) ont été réalisées à l'aide du modèle STICS sur une période de 23 ans (1990-2012) . Les objectifs de ces travaux étaient :i) de mettre en évidence les principaux processus impliqués dans la dissipation et le transfert de pesticides à long terme ; ii) d'évaluer l'influence de la dynamique des stocks en pesticide dans les sols, sur le transport en phase dissoute, vers le reste de l'hydrosystème ; iii) de déterminer les paramètres du modèle les plus sensibles aux pertes par lixiviation sur la période de 1990-2012. Les simulations ont été comparées aux observations disponibles sur le bassin versant. Les résultats mettent en avant la nécessité de prendre en considération la dynamique des stocks restants dans les sols pour comprendre le transfert des pesticides sur le long-terme. Une attention particulière doit également être portée sur les paramètres qui influencent la rétention et la disponibilité des pesticides à la lixiviation. En conclusion, les différences obtenues entre les flux lixiviés simulés pour une culture de blé et de maïs montrent l'intérêt des modèles agronomiques dans la modélisation du devenir des pesticides à l'échelle du bassin versant. / A pesticide fate module was implemented in the crop model STICS (SimulateurmulTIdisciplinaire pour les Cultures Standard) in order to simulate pesticidetransfer in agricultural soils. Then the model has been evaluated with three studysites datasets. In order to study the fate of pesticides at the scale of the Orgeval catchment, simulations of four herbicides (atrazine, simazine,isoproturon chlortoluron) and one metabolite (DEA) were carriedout with the crop model STICS over a 23-year period (1990-2012). The objectives of the study were i) to highlight the main processes implied in pesticide fate and transfer at long-term; ii) to assess the influence of the dynamics of the remaining mass of pesticide in soil on transfer; iii) to determine the most sensitive parameters related to pesticide losses by leaching over a 23-year period.Simulations were compared against available observations at the catchment scale. The findings of the study show that the dynamic of the remaining mass ofpesticide in soil is a relevant issue to understand pesticide dissipation at longterm. Attention must be paid on parameters influencing sorption and availabilityof the pesticide for leaching. To conclude, the significant discrepancies in the simulated pesticide leaching for the two types of crops (maize and wheat) highlight the interest of using a crop model to simulate the fate of pesticides at the catchment scale.

Nos últimos anos é crescente o número de estudos que preocupam-se em compreender como as mudanças climáticas podem interferir no equilíbrio dos ecossistemas globais. Dentre as linhas de pesquisa destacam-se as avaliações de toxicidade química termo-dependente (TQTD) já que uma das principais previsões é o aumento da temperatura global. Esta variável ambiental por si só, pode influenciar processos biológicos essenciais de organismos aquáticos ectotérmicos modificando a sensibilidade frente ao estresse ambiental. No entanto, não se deve subestimar a capacidade dos organismos a lidar com condições ambientais adversas, por isso, estudos atuais estão considerando aspectos de aclimatação e adaptação a cenários desfavoráveis. A partir deste contexto, o presente trabalho teve como objetivo geral avaliar o efeito da aclimatação na toxicidade química termo-dependente para uma substância de referência (NaCl) e um herbicida (AKB®) que tem como princípio ativo o Glifosato, substância mais utilizada em agroquímicos no país. O organismo-teste utilizado foi o cladócero Ceriodaphnia silvestrii, organismo padronizado para testes ecotoxicológicos e que possui papel chave na cadeia trófica e ciclo de energia do sistema. Os experimentos foram realizados combinando a metodologia de testes padronizados utilizando três temperaturas (20ºC, 25ºC e 30ºC). A aclimatação foi avaliada através da exposição direta e parental a condições diferenciadas de temperatura. O endpoint foi a imobilidade dos organismos, sendo que a toxicidade e os efeitos da aclimatação foram analisados no programa R 3.3.2. Os resultados obtidos demonstraram um efeito significativo da temperatura na toxicidade de NaCl e do herbicida AKB® para Ceriodaphnia silvestrii. A tendência geral observada foi de TQTD positiva, com exceção da temperatura de origem 25ºC nos testes com o herbicida. A aclimatação promoveu diferenças tanto na toxicidade como na distribuição da sensibilidade dos organismos, evidenciando a importância de incorporá-la na avaliação da toxicidade termo-dependente de xenobióticos. / In recent years there has been a growing number of studies that are concerned with understanding how climate change can interfere with the balance of global ecosystems. Among the lines of research are the evaluations of temperature-dependent chemical toxicity (TDCT), since one of the main predictions is the increase in global temperature. This environmental variable alone can influence the essential biological processes of aquatic ectothermic organisms by modifying the sensitivity to environmental stress. However, the ability of organisms to deal with adverse environmental conditions should not be underestimated, so current studies are considering aspects of acclimation and adaptation to unfavorable scenarios. The objective of this study was to evaluate the effect of acclimation on the temperature-dependent chemical toxicity of a reference substance (NaCl) and an herbicide (AKB®) which has as its active ingredient glyphosate, the most used substance in agrochemicals in the country. The organism used was the cladoceran Ceriodaphnia silvestrii, standardized organism for ecotoxicological tests and which has key role in the trophic chain and energy cycle of the system. The experiments were performed by combining the standardized test methodology using three temperatures (20ºC, 25ºC and 30ºC). The acclimation was evaluated through direct and parental exposure to different temperature conditions. The endpoint was the immobility of the organisms, and the toxicity and effects of acclimation were analyzed in software R 3.3.2. The results showed a significant effect of temperature on the toxicity of NaCl and the herbicide AKB® for Ceriodaphnia silvestrii. The overall trend observed was positive TDCT, except for the 25°C source temperature in the tests with the herbicide. The acclimation promoted differences in the toxicity and the distribution of the sensitivity of the organisms, evidencing the importance of incorporating it in the evaluation of the temperature-dependent toxicity of xenobiotics.

Made available in DSpace on 2016-01-26T18:56:17Z (GMT). No. of bitstreams: 1 dissertacao_rodrigo.pdf: 152775 bytes, checksum: f2338214da0780d951520c726ab5576c (MD5) Previous issue date: 2008-11-17 / The sugarcane is one of most important cultures in Brazil, and is very important social and economically. The simultaneous use of nematicides with herbicides in sugarcane are growing every season, due to the positive along with productivities with the aim of these products. That coned responses in be explained due to high infestation of ectoparasitic nematode and weed in monoculture, when the application of these products is not accomplished. Some studies detected an interaction and a negative effect among the nematicides carbamates class, when they are associated to herbicides classified as substituted ureas. The objective this work was to study the biometricals and physiologicals parameters in cultivar RB72-454 in combined application with nematicide (Carbofuran) and herbicide (Tebuthiuron) with Al2(SO4)3 addition. The experiment was canned in pots of 20 L in greenhouse campus II - UNOESTE. In each recipients two stem were planted, with 20 cm of length. The treatments were the following: T1 - test; T2 - nematicide application carbofuran, at 2,975 kg a.i. for hectare; T3 - herbicide application (tebuthiuron), at 1 kg of a.i. for hectare; T4 nematicide application the carbofuran base, of 2,975 kg a.i. for hectare with application herbicide (tebuthiuron), at 1 kg of a.i. for hectare; T5 - nematicide application (carbofuran), at 2,975 kg a.i. for hectare with herbicide application (tebuthiuron), at 1 kg of a.i. for hectare, with more the addition of 27 mg Al for per kg of sail. In treatments of 600 kg was used by hectare of the formulation 8-28-16 as feeder. The work didn t show an interaction between Tebuthiuron and Carbofuran. A phytotoxic Tebuthiuron´s effect of was just detected with high sensibility equipments, and no Carbofuran´s phytotoxic effect was detected. / A cana-de-açúcar é uma das principais culturas do país, e assume um importante papel no cenário econômico e social brasileiro. O uso de nematicidas e herbicidas em cana de açúcar, principalmente em cana planta, tem aumentado significativamente, devido às boas respostas de produtividades quando de suas aplicações, estes aumentos de produtividades podem ser explicados devido a maior incidência de fitonematóides ectoparasitos e plantas invasoras em áreas com monocultura, quando não ocorre a utilização de nematicidas e herbicidas. O objetivo deste trabalho foi estudar os parâmetros biométricos de crescimento e os parâmetros fisiológicos da cultivar RB72-454 em situações de aplicação combinada de nematicida com herbicida e da adição Al2(SO4)3. O experimento foi conduzido em vasos de 20 L em ambiente controlado (casa de vegetação do campus II UNOESTE), sendo que em cada unidade experimental foram plantados com 2 toletes de 20 cm. Os tratamentos foram os seguintes: T1 testemunha; T2 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare; T3 Aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T4 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação do herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T5 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare, mais a adição de 27 mg Al por kg de terra; Em todos os tratamentos utilizou-se a adubação de 600 kg ha-1 da formulação 8-28-16. O trabalho mostrou que não ocorreu interação entre Tebuthiuron e Carbofuran, e que existe um efeito fitotóxico do Tebuthiuron detectado apenas com equipamentos de alta sensibilidade, e não foi detectado nenhum efeito fitotóxico do Carbofuran.

Made available in DSpace on 2016-01-26T18:56:18Z (GMT). No. of bitstreams: 1 DISSERTACAO COMPLETA.pdf: 152778 bytes, checksum: 583e8e29727e70694447a04afa042274 (MD5) Previous issue date: 2008-11-17 / The sugarcane is one of most important cultures in Brazil, and is very important social and economically. The simultaneous use of nematicides with herbicides in sugarcane are growing every season, due to the positive along with productivities with the aim of these products. That coned responses in be explained due to high infestation of ectoparasitic nematode and weed in monoculture, when the application of these products is not accomplished. Some studies detected an interaction and a negative effect among the nematicides carbamates class, when they are associated to herbicides classified as substituted ureas. The objective this work was to study the biometricals and physiologicals parameters in cultivar RB72-454 in combined application with nematicide (Carbofuran) and herbicide (Tebuthiuron) with Al2(SO4)3 addition. The experiment was canned in pots of 20 L in greenhouse campus II - UNOESTE. In each recipients two stem were planted, with 20 cm of length. The treatments were the following: T1 - test; T2 - nematicide application carbofuran, at 2,975 kg a.i. for hectare; T3 - herbicide application (tebuthiuron), at 1 kg of a.i. for hectare; T4 nematicide application the carbofuran base, of 2,975 kg a.i. for hectare with application herbicide (tebuthiuron), at 1 kg of a.i. for hectare; T5 - nematicide application (carbofuran), at 2,975 kg a.i. for hectare with herbicide application (tebuthiuron), at 1 kg of a.i. for hectare, with more the addition of 27 mg Al for per kg of sail. In treatments of 600 kg was used by hectare of the formulation 8-28-16 as feeder. The work didn t show an interaction between Tebuthiuron and Carbofuran. A phytotoxic Tebuthiuron´s effect of was just detected with high sensibility equipments, and no Carbofuran´s phytotoxic effect was detected. / A cana-de-açúcar é uma das principais culturas do país, e assume um importante papel no cenário econômico e social brasileiro. O uso de nematicidas e herbicidas em cana de açúcar, principalmente em cana planta, tem aumentado significativamente, devido às boas respostas de produtividades quando de suas aplicações, estes aumentos de produtividades podem ser explicados devido a maior incidência de fitonematóides ectoparasitos e plantas invasoras em áreas com monocultura, quando não ocorre a utilização de nematicidas e herbicidas. O objetivo deste trabalho foi estudar os parâmetros biométricos de crescimento e os parâmetros fisiológicos da cultivar RB72-454 em situações de aplicação combinada de nematicida com herbicida e da adição Al2(SO4)3. O experimento foi conduzido em vasos de 20 L em ambiente controlado (casa de vegetação do campus II UNOESTE), sendo que em cada unidade experimental foram plantados com 2 toletes de 20 cm. Os tratamentos foram os seguintes: T1 testemunha; T2 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare; T3 Aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T4 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação do herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T5 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare, mais a adição de 27 mg Al por kg de terra; Em todos os tratamentos utilizou-se a adubação de 600 kg ha-1 da formulação 8-28-16. O trabalho mostrou que não ocorreu interação entre Tebuthiuron e Carbofuran, e que existe um efeito fitotóxico do Tebuthiuron detectado apenas com equipamentos de alta sensibilidade, e não foi detectado nenhum efeito fitotóxico do Carbofuran.

Made available in DSpace on 2016-07-18T17:51:03Z (GMT). No. of bitstreams: 1 dissertacao_rodrigo.pdf: 152775 bytes, checksum: f2338214da0780d951520c726ab5576c (MD5) Previous issue date: 2008-11-17 / The sugarcane is one of most important cultures in Brazil, and is very important social and economically. The simultaneous use of nematicides with herbicides in sugarcane are growing every season, due to the positive along with productivities with the aim of these products. That coned responses in be explained due to high infestation of ectoparasitic nematode and weed in monoculture, when the application of these products is not accomplished. Some studies detected an interaction and a negative effect among the nematicides carbamates class, when they are associated to herbicides classified as substituted ureas. The objective this work was to study the biometricals and physiologicals parameters in cultivar RB72-454 in combined application with nematicide (Carbofuran) and herbicide (Tebuthiuron) with Al2(SO4)3 addition. The experiment was canned in pots of 20 L in greenhouse campus II - UNOESTE. In each recipients two stem were planted, with 20 cm of length. The treatments were the following: T1 - test; T2 - nematicide application carbofuran, at 2,975 kg a.i. for hectare; T3 - herbicide application (tebuthiuron), at 1 kg of a.i. for hectare; T4 nematicide application the carbofuran base, of 2,975 kg a.i. for hectare with application herbicide (tebuthiuron), at 1 kg of a.i. for hectare; T5 - nematicide application (carbofuran), at 2,975 kg a.i. for hectare with herbicide application (tebuthiuron), at 1 kg of a.i. for hectare, with more the addition of 27 mg Al for per kg of sail. In treatments of 600 kg was used by hectare of the formulation 8-28-16 as feeder. The work didn t show an interaction between Tebuthiuron and Carbofuran. A phytotoxic Tebuthiuron´s effect of was just detected with high sensibility equipments, and no Carbofuran´s phytotoxic effect was detected. / A cana-de-açúcar é uma das principais culturas do país, e assume um importante papel no cenário econômico e social brasileiro. O uso de nematicidas e herbicidas em cana de açúcar, principalmente em cana planta, tem aumentado significativamente, devido às boas respostas de produtividades quando de suas aplicações, estes aumentos de produtividades podem ser explicados devido a maior incidência de fitonematóides ectoparasitos e plantas invasoras em áreas com monocultura, quando não ocorre a utilização de nematicidas e herbicidas. O objetivo deste trabalho foi estudar os parâmetros biométricos de crescimento e os parâmetros fisiológicos da cultivar RB72-454 em situações de aplicação combinada de nematicida com herbicida e da adição Al2(SO4)3. O experimento foi conduzido em vasos de 20 L em ambiente controlado (casa de vegetação do campus II UNOESTE), sendo que em cada unidade experimental foram plantados com 2 toletes de 20 cm. Os tratamentos foram os seguintes: T1 testemunha; T2 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare; T3 Aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T4 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação do herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T5 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare, mais a adição de 27 mg Al por kg de terra; Em todos os tratamentos utilizou-se a adubação de 600 kg ha-1 da formulação 8-28-16. O trabalho mostrou que não ocorreu interação entre Tebuthiuron e Carbofuran, e que existe um efeito fitotóxico do Tebuthiuron detectado apenas com equipamentos de alta sensibilidade, e não foi detectado nenhum efeito fitotóxico do Carbofuran.

Made available in DSpace on 2016-07-18T17:51:03Z (GMT). No. of bitstreams: 1 DISSERTACAO COMPLETA.pdf: 152778 bytes, checksum: 583e8e29727e70694447a04afa042274 (MD5) Previous issue date: 2008-11-17 / The sugarcane is one of most important cultures in Brazil, and is very important social and economically. The simultaneous use of nematicides with herbicides in sugarcane are growing every season, due to the positive along with productivities with the aim of these products. That coned responses in be explained due to high infestation of ectoparasitic nematode and weed in monoculture, when the application of these products is not accomplished. Some studies detected an interaction and a negative effect among the nematicides carbamates class, when they are associated to herbicides classified as substituted ureas. The objective this work was to study the biometricals and physiologicals parameters in cultivar RB72-454 in combined application with nematicide (Carbofuran) and herbicide (Tebuthiuron) with Al2(SO4)3 addition. The experiment was canned in pots of 20 L in greenhouse campus II - UNOESTE. In each recipients two stem were planted, with 20 cm of length. The treatments were the following: T1 - test; T2 - nematicide application carbofuran, at 2,975 kg a.i. for hectare; T3 - herbicide application (tebuthiuron), at 1 kg of a.i. for hectare; T4 nematicide application the carbofuran base, of 2,975 kg a.i. for hectare with application herbicide (tebuthiuron), at 1 kg of a.i. for hectare; T5 - nematicide application (carbofuran), at 2,975 kg a.i. for hectare with herbicide application (tebuthiuron), at 1 kg of a.i. for hectare, with more the addition of 27 mg Al for per kg of sail. In treatments of 600 kg was used by hectare of the formulation 8-28-16 as feeder. The work didn t show an interaction between Tebuthiuron and Carbofuran. A phytotoxic Tebuthiuron´s effect of was just detected with high sensibility equipments, and no Carbofuran´s phytotoxic effect was detected. / A cana-de-açúcar é uma das principais culturas do país, e assume um importante papel no cenário econômico e social brasileiro. O uso de nematicidas e herbicidas em cana de açúcar, principalmente em cana planta, tem aumentado significativamente, devido às boas respostas de produtividades quando de suas aplicações, estes aumentos de produtividades podem ser explicados devido a maior incidência de fitonematóides ectoparasitos e plantas invasoras em áreas com monocultura, quando não ocorre a utilização de nematicidas e herbicidas. O objetivo deste trabalho foi estudar os parâmetros biométricos de crescimento e os parâmetros fisiológicos da cultivar RB72-454 em situações de aplicação combinada de nematicida com herbicida e da adição Al2(SO4)3. O experimento foi conduzido em vasos de 20 L em ambiente controlado (casa de vegetação do campus II UNOESTE), sendo que em cada unidade experimental foram plantados com 2 toletes de 20 cm. Os tratamentos foram os seguintes: T1 testemunha; T2 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare; T3 Aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T4 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação do herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare; T5 Aplicação de nematicida a base de carbofuran, na dose de 2,975 kg i.a. por hectare com a aplicação de herbicida a base de tebuthiuron, na dose de 1 kg do i.a. por hectare, mais a adição de 27 mg Al por kg de terra; Em todos os tratamentos utilizou-se a adubação de 600 kg ha-1 da formulação 8-28-16. O trabalho mostrou que não ocorreu interação entre Tebuthiuron e Carbofuran, e que existe um efeito fitotóxico do Tebuthiuron detectado apenas com equipamentos de alta sensibilidade, e não foi detectado nenhum efeito fitotóxico do Carbofuran.

No description available.

<p>Tall waterhemp management in agronomic crops continues to be an increasing problem due to widespread resistance to herbicides, including protoporphyrinogen oxidase (PPO)-inhibitors. With limited effective postemergence herbicides, especially in soybeans, research to further understand the selection of PPO-resistant (PPO-R) tall waterhemp and identification of new herbicide resistance mechanisms is crucial for improving weed management decisions in order to slow selection for herbicide resistance and prolong the effectiveness of PPO-inhibiting herbicides.</p> <p> Previous research has shown that soil-applied applications of PPO-inhibiting herbicides can increase the frequency of the PPO resistance trait (∆G210) in surviving tall waterhemp plants, even when applied in combination at the same ratio with the very long chain fatty acid inhibitor (VLCFA), <i>s-</i>metolachlor. Field experiments were conducted to determine if selection for tall waterhemp resistant individuals to PPO-inhibitors could be reduced when the soil residual activity of <i>s</i>-metolachlor persisted longer than the PPO-inhibitor herbicide. The frequency of ∆G210 in surviving individual plants increased as the fomesafen rate increased, but was independent of the rate of <i>s</i>-metolachlor. Additionally, heterozygosity of ∆G210 in surviving individuals did not change with any rate or combination of fomesafen and <i>s</i>-metolachlor. However, saflufenacil, standard PPO-inhibitor with relatively short soil residual activity, applied alone increased the number of homozygous PPO-R tall waterhemp by 15% compared to the high rate of <i>s</i>-metolachlor and the combination of saflufenacil and <i>s</i>-metolachlor. Furthermore, this research demonstrated that end of season control of tall waterhemp plays a more vital role in delaying a large-scale shift towards herbicide resistance through reduced seed production. This can be achieved through the combination of multiple effective herbicide sites of action, including soil residual PPO-inhibitors. Tall waterhemp control and density were greatest with the high rates of fomesafen plus <i>s</i>-metolachlor, which resulted in the lowest number of PPO-R tall waterhemp that survived herbicide treatment at the end of season.</p> <p> Prior to the research conducted in this thesis, the only known resistance mechanism to PPO-inhibiting herbicides in tall waterhemp has been the ∆G210 target site mutation. A previously developed TaqMan assay used to determine the presence or absence of the ∆G210 mutation has allowed accurate, high throughput screening of this mutation. However, suspected PPO-R tall waterhemp do not always receive positive confirmation indicating the presence of an alternative resistance mechanism. Identification of additional resistance mechanisms can provide valuable insight in regards to resistance to PPO-inhibiting herbicides as well as cross resistance to other herbicide modes of action, which can lead to improved tall waterhemp management decisions. Of 148 tall waterhemp populations collected across the Midwestern U.S., 84% of the populations sampled contained at least one PPO-R biotype with the ∆G210 mutation, although several individual plants across the Midwest U.S. exhibited phenotypic resistance to fomesafen that could not be explained by ∆G210. The percentage of PPO-R tall waterhemp without ∆G210 was 19, 5, 2, 1, and 2% for Iowa, Illinois, Indiana, Minnesota, and Missouri, respectively. Following the initial greenhouse screening, subsequent tall waterhemp populations were selected that exhibited low-, mid-, and high-level resistance to fomesafen that resulted in resistance ratios from 0.6 to 17X in response to fomesafen. This research documents the variability in fomesafen response to multiple tall waterhemp populations in addition to revealing the presence of additional resistance mechanism(s), other than the previously known ∆G210 mutation that has been the benchmark for resistance to PPO-inhibiting herbicides in tall waterhemp.</p> <p> Lastly, greenhouse and lab experiments were conducted to investigate the role of antioxidant enzymes with PPO-R tall waterhemp via ∆G210. The objectives of this research were to determine if the variability in resistance ratios for PPO-R tall waterhemp documented in greenhouse and field scenarios could be due to an enhanced antioxidant enzyme pathway. Basal levels of antioxidant enzymes in PPO-S populations were not different from PPO-R populations when pooled together by respective phenotype. However, enzyme activity of tall waterhemp populations varied at the individual level, but independent of the ∆G210 mutation. This indicates that an inherent enhanced antioxidant enzyme pathway does not cause the variability in fomesafen response in tall waterhemp. With the exception of glutathione reductase, antioxidant enzyme activity following fomesafen application was generally the same for PPO-R and PPO-S populations by increasing, decreasing, or remaining unchanged. Glutathione reductase activity in PPO-S populations decreased compared to PPO-R populations from 9 to 36 HAT. By 36 HAT, all antioxidant enzyme activity for PPO-S populations was lower compared to PPO-R populations most likely a consequence of more lipid peroxidation. This research shows that antioxidant enzyme activity correlated with fomesafen application and documents the variability observed within tall waterhemp populations with and without the ∆G210 mutation. </p>

<p>Akvatični ekosistemi su izloženi simultanom delovanju velikog broja potencijalno<br />toksičnih supstanci u vremenski i prostorno promenljivim uslovima u životnoj sredini.<br />U ovoj disertaciji je poređen&nbsp; efekat pojedinačnih herbicida&nbsp; &ndash;&nbsp; atrazina, izoproturona i<br />trifluralina&nbsp; &ndash;&nbsp; sa efektima njihovih sme&scaron;a u testu sa&nbsp;<em> Lemna minor</em>. Odabrane su sme&scaron;e sa sličnim (dvo-komponentna sme&scaron;a atrazina/izoproturona) i različitim (dvo-komponentna sme&scaron;a atrazina/trifluralina i izoproturona/trifluralina, kao i tro-komponenta sme&scaron;a)&nbsp; mehanizmom toksičnog dejstva. Kako se sve če&scaron;će ističe<br />neophodnost sagledavanja ne samo&nbsp; potencijalnih&nbsp; razlika&nbsp; u&nbsp; toksikolo&scaron;koj&nbsp; osetljivosti jedinki/populacija, već i&nbsp; razlika&nbsp; u&nbsp; efikasnosti&nbsp; njihovog oporavka, u ovoj disertaciji, je određen&nbsp; potencijal oporavka&nbsp; vrste&nbsp;<em> L. minor&nbsp;</em> nakon izloženosti navedenim pojedinačnim herbicidima/sme&scaron;ama. Ispitano je da li prirodna&nbsp; organska&nbsp; materija (POM),&nbsp; koja&nbsp; je&nbsp; u testovima na akvatičnim makrofitama&nbsp; simulirana&nbsp; preko huminskih materija (HM) u realnim koncentracijama u povr&scaron;inskim vodama, modulira toksičnost atrazina i 2,4 D, i njihove dvo-komponentne sme&scaron;e,&nbsp; u&nbsp; testu sa&nbsp;<em> L. minor</em>, odnosno izoproturona, dikambe i njihove dvo-komponentne sme&scaron;e, u testu sa&nbsp; <em>Myriophyllum aquaticum</em>.&nbsp; Utvrđen je stepen&nbsp; odstupanja između empirijske&nbsp; toksičnosti svih navedenih sme&scaron;a herbicida, sa teorijski očekivanim vrednostima na osnovu modela adicije koncentracija (CA), u testovima na obe vrste akvatičnih makrofita.&nbsp; Ispitano je da li se postojeći CA model može koristiti i za procenu toksičnog dejstva sme&scaron;a uzimajući u obzir integralno i podatke o oporavku eksponiranih&nbsp; vrsta akvatičnih makrofita.&nbsp; Rezultati u ovoj disertaciju su pokazali da&nbsp; modifikacijom laboratorijskog protokola gde se oporavak akvatičnih makrofita pratio tokom dodatnih pet/sedam dana testa nakon sedmodnevne ekspozicije se mogu dobiti ekolo&scaron;ki relevantni podaci o odloženom toksičnom dejstvu pojedinačnih supstanci/sme&scaron;a.&nbsp; U testu sa atrazinom i izoproturonom, kao pojedinačnim supstancama, je uočen efikasan oporavak vrste&nbsp;<em> L.minor</em>. Sa druge strane, u slučaju trifluralina i 2,4 D u periodu oporavka je zabeleženo odloženo toksično dejstvo. Na primeru trifluralina i 2,4 D se pokazalo da standardnitestovi toksičnosti, zanemarujući podatke o potencijalu oporavka, mogu potceniti realan rizik od pesticida. U slučaju drugog sintetičkog auksina, dikambe, pri izabranoj seriji koncentracija nije zabeleženo toksično dejstvo na vrstu&nbsp;<em> L. minor</em>.&nbsp; Odgovor vrste<em> L. minor</em>&nbsp; na dejstvo dvo-komponentne sme&scaron;e atrazina i izoproturona je sličan onom zabeleženom u testu sa navedenim herbicidima, kao pojedinačnim supstancama. Zabeležen je efikasan oporavak biljne kulture, nezavisno od primenjene koncentracije herbicida u sme&scaron;i. Sa druge strane, oporavak vrste&nbsp; <em>L. minor</em>&nbsp; nakon izloženosti dvo-&nbsp; i tro-komponentnim sme&scaron;ma sa trifluralinom zavisi od primenjene koncentracije herbicida u sme&scaron;i i zabeležen je jedino u&nbsp; tipu sme&scaron;a gde su koncentracije pojedinačnih herbicida bliske relativno bliske mogućim koncentracijama herbicida u životnoj sredini.&nbsp; Povećanje toksičnosti pojedinačnih supstanci/sme&scaron;a uslovljeno prisustvom HM je primećena u slučaju atrazina, 2,4 D i njihove dvo-komponentne sme&scaron;e, u testu na vrsti&nbsp;<em> L. minor,</em> odnosno&nbsp; dikambe u testu sa<em> M. aquaticum</em>. Suprotan efekat HM je primećen u testu sa&nbsp; <em>M. aquaticum</em>&nbsp; u slučaju&nbsp; izoproturona i dvo-komponentne sme&scaron;e izoproturona i dikambe, jer je zabeležena&nbsp; niža&nbsp; toksičnost u prisustvu HM.&nbsp; Iako određene razlike u toksičnosti između ispitivanih test tretmana u prisustvu i odsustvu HM postoje, one nisu bile statistički značajne.&nbsp; Oporavak akvatičnih makrofita od efekta dvo-komponentnih sme&scaron;a, u prisustvu/odsustvu HM, zavisi od primenjene koncentracije herbicida u sme&scaron;i. Izuzetak čini dvo-komponentna sme&scaron;a atrazina i 2,4&nbsp; D, u testu sa <em>L. minor,</em> gde nije do&scaron;lo do oporavka biljne kulture ni u jednom od tipova sme&scaron;a u prisustvu HM. Generalno, uočena je dobra saglasnost između empirijske i predviđene toksičnosti,&nbsp; na osnovu&nbsp; CA modela, nezavisno od mehanizma toksičnog dejstva supstanci prisutnih u sme&scaron;i ili&nbsp; prisustva odnosno odsustva HM.&nbsp; Odstupanje od adivnosti je zabeleženo jedino u testu sa&nbsp;<em> L. minor&nbsp;</em> u slučaju dvo-komponentnih sme&scaron;a sa trifluralinom&nbsp; (atrazin+trifluralin i izoproturon+trifluralin), gde se ispostavilo da&nbsp; CA model u određenoj meri potcenjuje dejstvo navedenih sme&scaron;a, &scaron;to&nbsp; upućuje na pojavu sinergističkih interakcija između supstanci.&nbsp; Pokazano je i&nbsp; da se CA model može alternativno koristiti za procenu toksičnosti odabranih sme&scaron;a, na osnovu integralnih saznanja o osetljivosti i potencijalu oporavka eksponiranih&nbsp; jedinki/populacija, pod uslovom da su dostupni takvi podaci za pojedinačne susptance koje ulaze u sastav sme&scaron;e.</p> / <p>Aquatic ecosystems are exposed to a simultaneous effect of a large number of potentially toxic substances in a temporally and spatially variable conditions in the environment. In this doctoral thesis, the effect of the individual herbicides&nbsp; atrazine,isoproturon, and trifluralin was compared with the effect of their mixtures, in the test with&nbsp;<em> Lemna minor.</em> Mixtures with a similar (binary mixture of&nbsp; atrazine/isoproturon) and dissimilar (binary mixtures with atrazine/trifluralin, soproturon/trifluralin, and ternary mixture) mode of action were selected. There is a clear need to take into account not only the differences in toxicological sensitivity of the exposed individuals/populations, but also the differences in their recovery efficiency.Therefore, in this&nbsp; thesis,&nbsp; L<em>. minor&nbsp;</em> recovery potential was assessed after &nbsp; the exposure to the individual herbicides/mixtures. It was tested whether a natural organic matter (NOM), which was, in these tests, simulated through the humic matter (HM) used in real concentrations&nbsp; in surface waters, modulated the toxicity of atrazine, 2.4 D, and their binary mixture, in tests with&nbsp; L.<em> minor,</em> and disoproturon, dicamba and their binary mixture, in tests with Myriophyllum aquaticum. The deviation between the empirical toxicity of the herbicidal mixtures and the predicted toxicity based on the concentration addition (CA) model was determined. It was also examined whether the current CA model can be used to predict mixture&nbsp; oxic effects by taking into account the information about the plant recovery potential as well. The results showed that by modifying laboratory protocols, where the recovery of aquatic macrophytes was followed for additional five/seven days after the seven day exposure, environmentally relevant data on delayed toxic effects of the individual substances/mixtures can be obtained. In the tests with atrazine and isoproturon as individual substances, the efficient recovery of&nbsp; L.<em> minor</em>&nbsp; was observed. On the other hand, in the case of trifluralin and 2,4 D, delayed toxic effects&nbsp; were recorded during the recovery period.In the test with trifluralin and 2.4 D, it was shown that standard toxicity tests may underestimate the real risk of pesticides by not considering data on recovery. In the case of another synthetic auxin, dicamba, toxic effect on&nbsp; L.<em> minor</em>&nbsp; was&nbsp; not reported in the selected concentration series. The response of&nbsp; L. <em>minor</em>&nbsp; after the exposure tobinary mixtures of atrazine and isoproturon was similar to the one recorded in the tests with these herbicides as the individual&nbsp; substances. Efficient plant recovery was recorded, regardless of the applied herbicide concentration in the mixture. On the other hand, the recovery of&nbsp; L.<em> minor</em>&nbsp; after exposure to binary and ternary mixtures with trifluralin depended on the applied herbicide concentration in the mixture, and was recorded only in the type of mixtures where the concentrations of&nbsp; the individual herbicides were close to the possible concentration of these herbicides in the environment. The toxicity increase of the individual substances/mixtures, influenced by the presence of HM was observed in the case of atrazine, 2,4 D, and their binary mixture, in the test with L. <em>minor</em>, that is,&nbsp; dicamba, in the test with&nbsp; M.<em> aquaticum</em>. In the test with&nbsp; M.<em> aquaticum</em>, the opposite effect was observed in the case ofisoproturon and binary mixture of isoproturon and &nbsp; dicamba, due to&nbsp; lower&nbsp; toxicity being recorded in the presence of HM. Even though some differences in toxicity between the test treatments in the presence and absence of HM&nbsp; were recorded, the differences were not statistically significant. The recovery of macrophytes after the exposure to the binary mixtures, in the presence/absence of HM, depended on the applied herbicide concentration in the mixture. The exception was noticed in the test with&nbsp; L<em>. minor</em>&nbsp; in the binary mixture with atrazine and 2,4 D, where no recovery was recorded in any type of the mixture in the presence of HM. Generally, there was a good agreement between the empirical toxicity and the predicted one based on the CA model, regardless of the mode of action of the toxic substances present in the mixture, or presence/absence of HM. The deviation from additivity was recorded only in the test with L.<em> minor</em> in the case of the binary mixture&nbsp; with trifluralin (atrazine/trifluralin and isoproturon/trifluralin), which meant that the CA model underestimated the mixture effect to a certain extent, suggesting that synergistic interaction between the substances might have appeared. It was also shown that the CA model may alternatively be&nbsp; used for the assessment of toxicity of&nbsp; the selected mixture, based on the integrated knowledge of both sensitivity and recovery potential of the exposed species/populations, providing that such information about individual substances in&nbsp; the mixture exists.</p>