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Exposure to moderately high levels of ionizing radiation (<20 Gy) has in some instances shown a hormetic effect in numerous vegetable-type crops. Past experiments performed in outdoor cultivars have shown a somewhat unpredictable increase in growth rate with a higher overall yield in a specified time when the seeds are exposed to ionizing radiation prior to germination. This experiment has attempted to eliminate potentially confounding variables in the growth of a legume utilizing an Environmental Protection Agency controlled green house. The experiment was a completely randomized block design with six blocks and seven treatment groups. Each treatment group of pinto beans (Phaseolus vulgaris L.) were exposed to ������Co radiation, given doses of 5-20 Gy, planted and grown for 40 days. Due to the symbiotic relationship with rhizobium bacteria within a seed, the expected result was a lowered nitrogen fixation capacity as bacteria concentration was reduced due to sterilization by the high energy gamma, yielding a smaller plant mass. The predicted trend in reduction would be described by the linear no-threshold model. A statistically significant increase in overall plant mass occurred in the 5 Gy treatment group, with a subsequent linear trend in mass reduction at treatment levels of 7.5, 10, 12.5 and 15 Gy. The overall quality and plant mass decreased markedly at a treatment level of 20 Gy. Additional possible contributions to plant differences in growth within a green house were light intensity, temperature, CO��� level and soil water retention. The complete randomized block design attempts to remove these as potentially confounding variables. / Graduation date: 1999

Threshold and non-threshold linear models that govern toxicology are challenged by an alternative model, hormesis. It is defined as low-dose stimulation and high-dose inhibition from a stressor. Insecticide-induced hormesis has been studied in a plethora of insect-insecticide models at biochemical, individual and population levels. This research focuses on the effects of sublethal concentrations of insecticides on reproductive responses of green peach aphid, Myzus persicae (Sulzer), at individual and population level besides regulation of stress, dispersal and developmental genes during hormesis. In laboratory studies, irrespective of the duration and route of exposure, sublethal concentrations of imidacloprid induced stimulations in fecundity of M. persicae but the nature of response differed intra- and trans-generationally. Fitness tradeoffs could be rendered due to declined fecundity in successive generations. However, continuous exposure to sublethal concentrations does not compromise overall fitness trans-generationally, considering recovered levels of fecundity as controls in successive generations and the total reproduction after four generations. Greenhouse experiments affirmed uncompromised fitness where reproductive stimulations were noted in aphids exposed to imidacloprid treated potato plants. Up- and down- regulation of stress, dispersal and developmental genes was noted during imidacloprid-induced hormesis in M. persicae that mirrored the reproductive responses in few instances. Global DNA methylation results emphasized the heritability of adapted traits trans-generationally via hypermethylation. Dispersal related genes (OSD, TOL and ANT) that are predominantly expressed in alates (about 2- to 5-fold) were affected in apterous aphids continuously exposed to sublethal concentrations of imidacloprid. No direct relation with the previously noted fecundity was established implying adaptive cellular stress response pathways might be triggered rather than normal regulatory processes due to low-dose imidacloprid exposure. At a biochemical level, a study noted that imidacloprid-induced hormesis concurrently stimulated juvenile hormone III (JH) production and fecundity in M. persicae. Precocene, an anti-JH, at sublethal concentrations induced reproductive stimulations in M. persicae. Gene regulation during precocene-induced hormesis mirrored imidacloprid results for few genes including FPPS, a JH precursor gene, with a higher magnitude of regulation. Considering these stimulatory effects that insecticide-induced hormesis at various biological hierarchies, causes for pest resurgence, hormesis could have ramifications from declines in natural enemy population.

Sementes de tomate do híbrido Gladiador foram expostas a radiações gama do Co-60 nas doses 0; 2,5; 5; 7,5; 10; 12,5; 15 e 20 Gy. Foram analisados vários parâmetros como germinação, altura da plântula até o cotilédone, altura total da plântula, peso fresco e seco da plântula, altura da planta, diâmetro do caule da planta, peso fresco e seco e área da 5º folha, número de frutos verdes com diâmetro maior que 3 cm, número de frutos esverdeados, de vez e maduros, número total de frutos, Brix e pH dos frutos, peso médio dos frutos e produção total de frutos. Diferentes efeitos estimulantes foram observados nos diversos estádios de desenvolvimento das plantas. O maior estímulo, para produção ocorreu para a dose de 10 Gy. As maiores alturas médias da plântula e da planta ocorreram para a dose de 7,5 Gy. O maior número de frutos verdes com 3 cm de diâmetro ocorreu para o tratamento de 12,5 e 15 Gy. A irradiação também estimulou a produção de maior número total de frutos, em todas as doses aplicadas, com vantagem para a dose de 10 Gy que produziu 88% mais frutos que a testemunha e também uma produção em peso 86% maior. O pH dos frutos acidificou significativamente a partir da dose de 12,5 Gy. Houve aumento na produção em todos os tratamentos em relação à testemunha sendo que o maior estímulo para produção ocorreu para as doses de 10, 12,5 e 15 Gy. O uso de baixas doses de radiação gama do Co- 60 aplicado no tratamento pré-semeadura, nas sementes, mostrou-se eficiente em estimular o desenvolvimento das plantas e aumentar a produção do tomate. / Tomato seeds of the Gladiador hybrid were exposed to gamma radiation of Co-60 with the following doses: 0; 2,5; 5; 7,5; 10; 12,5; 15 e 20 Gy. Analysis were performed on germination, seedlings height to cotyledon, seedling total height, seedling fresh and dry weight, plant height, stalk diameter at the root beginning, fresh and dry weight of the 5th leaf, number of green fruits with diameter higher than 3 cm, number of green, half ripen and ripen fruits, total number of fruits, Brix and pH of fruits, average fruit weight and fruit total production. A variety of stimulation effects were observed on the different plant developing stages. The greatest stimulus for production was observed in the 10 Gy dose. The highest seedling average height and plant average height were observed for the 7,5 Gy dose. The biggest number of green fruits with diameter higher than 3 cm occurred for the 12,5 and 15 Gy treatments. Irradiation also stimulated a higher total number of fruits in all doses, having advantage the 10 Gy dose which produced 88% more fruits than control as well as 86% more weight production. The fruits pH acidified significantly in a dose of 12,5 Gy and higher. Production increased in all treatments comparing to control and the highest stimulus for production observed was for the 10, 12,5 and 15 Gy. The use of low gamma radiation doses of Co-60 applied as pre-sowing treatment in the seeds, efficiently stimulated the development of plants and the tomato production.

Sementes de tomate do híbrido Gladiador foram expostas a radiações gama do Co-60 nas doses 0; 2,5; 5; 7,5; 10; 12,5; 15 e 20 Gy. Foram analisados vários parâmetros como germinação, altura da plântula até o cotilédone, altura total da plântula, peso fresco e seco da plântula, altura da planta, diâmetro do caule da planta, peso fresco e seco e área da 5º folha, número de frutos verdes com diâmetro maior que 3 cm, número de frutos esverdeados, de vez e maduros, número total de frutos, Brix e pH dos frutos, peso médio dos frutos e produção total de frutos. Diferentes efeitos estimulantes foram observados nos diversos estádios de desenvolvimento das plantas. O maior estímulo, para produção ocorreu para a dose de 10 Gy. As maiores alturas médias da plântula e da planta ocorreram para a dose de 7,5 Gy. O maior número de frutos verdes com 3 cm de diâmetro ocorreu para o tratamento de 12,5 e 15 Gy. A irradiação também estimulou a produção de maior número total de frutos, em todas as doses aplicadas, com vantagem para a dose de 10 Gy que produziu 88% mais frutos que a testemunha e também uma produção em peso 86% maior. O pH dos frutos acidificou significativamente a partir da dose de 12,5 Gy. Houve aumento na produção em todos os tratamentos em relação à testemunha sendo que o maior estímulo para produção ocorreu para as doses de 10, 12,5 e 15 Gy. O uso de baixas doses de radiação gama do Co- 60 aplicado no tratamento pré-semeadura, nas sementes, mostrou-se eficiente em estimular o desenvolvimento das plantas e aumentar a produção do tomate. / Tomato seeds of the Gladiador hybrid were exposed to gamma radiation of Co-60 with the following doses: 0; 2,5; 5; 7,5; 10; 12,5; 15 e 20 Gy. Analysis were performed on germination, seedlings height to cotyledon, seedling total height, seedling fresh and dry weight, plant height, stalk diameter at the root beginning, fresh and dry weight of the 5th leaf, number of green fruits with diameter higher than 3 cm, number of green, half ripen and ripen fruits, total number of fruits, Brix and pH of fruits, average fruit weight and fruit total production. A variety of stimulation effects were observed on the different plant developing stages. The greatest stimulus for production was observed in the 10 Gy dose. The highest seedling average height and plant average height were observed for the 7,5 Gy dose. The biggest number of green fruits with diameter higher than 3 cm occurred for the 12,5 and 15 Gy treatments. Irradiation also stimulated a higher total number of fruits in all doses, having advantage the 10 Gy dose which produced 88% more fruits than control as well as 86% more weight production. The fruits pH acidified significantly in a dose of 12,5 Gy and higher. Production increased in all treatments comparing to control and the highest stimulus for production observed was for the 10, 12,5 and 15 Gy. The use of low gamma radiation doses of Co-60 applied as pre-sowing treatment in the seeds, efficiently stimulated the development of plants and the tomato production.

O sistema canabinóide endógeno tem uma importante função modulatória em muitos processos neurobiológicos, incluindo a neuroproteção, a plasticidade neuronal e a neuroinflamação. Neste estudo nós pré-tratamos os camundongos com um agonista inverso do receptor CB1, para avaliarmos se ocorria a neuroproteção através de respostas adaptativas. Camundongos machos adultos (C57BL/6J) de 3 meses de idade foram pré-tratados durantes 4 dias com injeções diearias de 3 mg/Kg de AM251 (agonista inverso CB1) ou com veículo, intraperitonealmente (i.p.). Vinte e quatro horas depois da última injeção de AM251/Veículo, os animais foram injetados com LPS i.p. (500 µg/kg) ou salina. Foram realizados testes comportamentais e testes bioquímicos com estruturas encefálicas. Nossa hipótese era que o pré-tratamento com o agonista inverso de CB1 iria funcionar como um estressor moderado, levando a uma neuroadaptação. Contudo, o pré-tratamento não ativou vias neuroprotetoras, e sim como atuou como um estresse deletério. / The endogenous cannabinoid system seems to play a modulatory function in many neurobiological processes, including neuroprotection, neuronal plasticity and neuroinflammation. In this study we pretreated the mice with an inverse agonist of the receptor CB1, in order to evaluate this neuroprotection through adaptive responses. Three months-old male mice (C57BL/6J) were pretreated during 4 days with daily injections of 3mg/Kg of AM251 (CB1 inverse agonist) or with vehicle, intraperitoneally (i.p.). Twenty-four hours after the last AM251/Vehicle injection, animals were injected i.p. with LPS (500 µg/kg) or saline. Behavioural and bichoemical assays were performed. Our hypothesis was that the pretreatment with the inverse agonist of CB1 was going to act as a moderate stressor, leading to a neuroadaptation. However CB1 pretreatment potentiated or sensitized the pro-inflammatory signaling pathway. Our pre-treatment worked not as a moderate stressor but as a deleterious stressor.

This thesis examines the toxicity of the herbicide glyphosate (two formulations ¡V technical grade and Roundup Biactive RB) and the insecticide chlorpyrifos CPF to a model freshwater food chain of a producer and consumer. The importance of studying the toxicity of low (environmentally realistic) concentrations of pesticides to non-target organisms is highlighted. An extensive literature review on the toxicity of glyphosate and chlorpyrifos to aquatic organisms is provided. The requirements for the maintenance of algal (Chlorella vulgaris, Chlorella pyrenoidosa and Pseudokirchneriella subcapitata) and Daphnia carinata cultures are discussed. The effects of two formulations of the herbicide glyphosate (technical grade and Roundup Biactive„µ) and the insecticide chlorpyrifos on the growth of Chlorella pyrenoidosa and Pseudokirchneriella subcapitata were studied, and the EC50 values determined. Hormesis was observed when P. subcapitata was exposed to concentrations of Roundup equal to 7% and 4% of its EC50 respectively. When exposed to chlorpyrifos concentrations 0.3-5 ƒÝg/L, hormesis was observed for both algal species with a maximum at 0.06% of EC50. The effects of sublethal concentrations of chlorpyrifos on population characteristics of Daphnia carinata were investigated in multiple-generation toxicity testing using individual culture. Exposure to chlorpyrifos affected survival and fecundity of animals in the first generation. In the second generation the most affected endpoint was time to the first brood with an indication of hormesis. LC50 tests were then conducted using animals of the third generation from each of the exposures in individual tests. Results of testing the third generation showed a constant significant decline in LC50 in the order of control daphnids through to ¡¥0.1 LC50¡¦ pre-exposed daphnids. The same experimental protocol was used in testing of glyphosate (technical grade and Roundup Biactive). Glyphosate was tested in two different media: sea salt solution and M4 medium, while Roundup Biactive was tested in M4 medium. Results indicated that glyphosate and Roundup Biactive had low toxicity to Daphnia. Hormesis was evident in sea salt medium exposures in the first and second generations of daphnids with glyphosate. When exposed to glyphosate and Roundup Biactive in M4 medium animals showed no indication of hormesis. It is hypothesized that glyphosate may have compensated for the lack of microelements in the sea salt medium, and possible mechanisms discussed.The modifying effect of glyphosate on the toxicity of cadmium to Daphnia carinata was studied using the same experimental design. Low concentrations of Roundup Biactive reduced the toxicity of cadmium, and the performance of daphnia was enhanced in terms of animal size, survival, fecundity, and the rate of natural increase in both generations in the presence of glyphosate. However when the third generation was tested for their sensitivity to Cd in the 48-h LC50 experiments there was no difference between RB-free and RB-spiked treatments in pair wise comparisons, indicating that no adaptation mechanisms were involved in the enhancement. The implications of these observed effects for environmental freshwater food chains subjected to pesticide exposure are discussed and recommendations on modifying pesticide use are provided.

Submitted by Gabrielle de Castro Macedo (gabriellecmacedo@gmail.com) on 2018-06-08T21:57:13Z No. of bitstreams: 1 Tese Gabrielle M.pdf: 2925084 bytes, checksum: df56d11b8216e24580f2f7ca847eb592 (MD5) / Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2018-06-11T12:07:38Z (GMT) No. of bitstreams: 1 macedo_gc_dr_botfca.pdf: 2799637 bytes, checksum: 38a0ff40cf7c14a31feec651dd99b926 (MD5) / Made available in DSpace on 2018-06-11T12:07:39Z (GMT). No. of bitstreams: 1 macedo_gc_dr_botfca.pdf: 2799637 bytes, checksum: 38a0ff40cf7c14a31feec651dd99b926 (MD5) Previous issue date: 2018-05-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O emprego de substâncias tóxicas as plantas, como o glyphosate, em doses muito menores que as recomendadas comercialmente pode ocasionar alterações em varáveis como crescimento, acúmulo de biomassa, altura, conteúdo de proteína e resistência a doenças. Desta forma, os objetivos deste trabalho foram realizar estudos para uma melhor compreensão das alterações bioquímicas, fisiológicas e fenológicas do arroz causadas por subdoses de glyphosate. O experimento 1 foi realizado à campo, na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas, FCA/UNESP, Botucatu/SP, nos anos agrícolas de 2015/2016 e 2016/2017. O delineamento experimental utilizado foi o de blocos casualizados, arranjado em esquema fatorial 2x7, sendo o primeiro fator época de aplicação do glyphosate (V3 ou R1) e, o segundo, as doses do herbicida (0; 7,5; 15; 30; 60; 120 e 240 g e.a. ha-1), com quatro repetições. Foram avaliados a produtividade, o comprimento de panículas, número de perfilhos por m², peso de 1000 grãos, número de grãos por panícula, a fertilidade de espiguetas e o número de dias entre a aplicação e o início de cada fase fenológica. Os experimentos 2 e 3 foram realizados em casa de vegetação, no Núcleo de Pesquisas Avançadas em Matologia (NUPAM), pertecentente à Faculdade de Ciências Agronômicas, FCA/UNESP, Botucatu/SP. O experimento 2 seguiu delineamento inteiramente casualizado em esquema fatorial (7x3) com cinco repetições. Os tratamentos foram constituídos por sete doses do herbicida glyphosate (0; 7,5; 15; 30; 60; 120 e 240 g e.a. ha-1) aplicados no estádio V3, e 3 períodos de chuva após a aplicação (12, 24 horas e ausência). Foram avaliados o perfilhamento e o acúmulo de massa das plantas. O experimento 3 foi arranjado em delineamento inteiramente casualizado em esquema fatorial (7x3) com quatro repetições. Os tratamentos foram constituídos por dez doses do herbicida glyphosate (0; 1,5; 3; 6; 12; 24; 36; 72; 180 e 360 g e.a. ha-1), aplicadas quando as plantas se encontravam em estádio V4, e três regimes de fornecimento de água (fornecimento contínuo, RH1 e RH2). Foram avaliados o consumo de água diário, o perfilhamento e o acúmulo de massa das plantas. A aplicação de subdoses de glyphosate em condições de campo não influenciou a produtividade e os componentes de produtividade das plantas de arroz até a dose de 60 g e.a. ha-1 de glyphosate quando a aplicação ocorreu em V3, e até 30 g e.a. ha-1 de glyphosate quando a aplicação ocorreu em R1. A partir destas doses, houve severo efeito de intoxicação da cultura. Observou-se que os diferentes períodos de chuva após a aplicação de subdoses de glyphosate não interferiram na resposta das plantas de arroz aos tratamentos. Não foi observado efeito hormético para acúmulo de biomassa e consumo de água em casa de vegetação. A aplicação de doses entre 30 e 240 g e.a. ha-1 de glyphosate proporcionou incremento do perfilhamento das plantas de arroz em todos os estudos realizados, sendo a dose que causou incremento dependente das condições de condução do estudo. / The use of toxic substances in plants, such as glyphosate, in doses much smaller than those recommended commercially can cause changes in variables such as growth, biomass accumulation, height, protein content and resistance to diseases. In this way, the objectives of this work were to carry out studies for a better understanding of the biochemical, physiological and phenological alterations of the paddy rice caused by glyphosate subdoses. Experiment 1 was carried out at the Experimental Farm Lageado, belonging to the College of Agronomic Sciences, FCA / UNESP, in Botucatu, Sao Paulo, in the agricultural years of 2015/2016 and 2016/2017. The experimental design was a randomized block arranged in a 2x7 factorial scheme, with the first factor being the glyphosate application time (V3 or R1) and the second herbicide dose (0, 7.5, 15, 30, 60, 120 and 240 g a.e. ha-1), with four replications. The productivity, panicle length, number of tillers per m², weight of 1000 grains, number of grains per panicle, spikelet fertility and the number of days between the application and the beginning of each phenological phase were evaluated. Experiments 2 and 3 were carried out in a greenhouse at the Weed Science Advanced Research Center (NUPAM), belonging to the Faculty of Agronomic Sciences, FCA / UNESP, in Botucatu, Sao Paulo. Experiment 2 was in a completely randomized design in a factorial scheme (7x3) with five replications. The factor one was doses of the herbicide glyphosate (0, 7.5, 15, 30, 60, 120 and 240 g a.e. ha-1) applied in the V3 and factor two was rainy periods after application (12, 24 hours and without rain). The tillering and mass accumulation of plants were evaluated. Experiment 3 was arranged in a completely randomized design in a factorial scheme (7x3) with four replications. The factor one consisted of ten doses of the herbicide glyphosate (0, 1.5, 3, 6, 12, 24, 36, 72, 180 and 360 g a.e. ha-1) applied when plants were in the V4 stage, and factor two was 3 water supply schemes (no stress, RH1 and RH2). Daily water consumption, tillering and plant mass accumulation were evaluated. The application of glyphosate subdoses under field conditions did not influence yield, productivity components or phenology of paddy rice plants up to the 60 g a.e. ha-1 of glyphosate when the application occurred in V3 and up to 30 g a.e. ha-1 of glyphosate when application occurred at R1. From these doses, there was a severe effect of intoxication of the culture. It was observed that different rainy periods after application of glyphosate subdoses did not interfere in the response of paddy rice plants to the treatments. At greenhouse conditions, no hormesis effect was observed for biomass accumulation and water consumption. The application of doses from 30 to 240 g a.e. ha-1 of glyphosate increased the tillering of paddy rice plants in all the studies carried out, being the dose that caused increment dependent of the conditions of conduction of each study.

Submitted by CAROLINA PUCCI DE MORAES null (carolpuccim@gmail.com) on 2016-08-30T19:59:57Z No. of bitstreams: 1 Dissertacao_Carol Pucci de Moraes.pdf: 1638908 bytes, checksum: 3ee166e7d6818cac639935061f63d082 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-08-31T17:39:40Z (GMT) No. of bitstreams: 1 moraes_cp_me_bot.pdf: 1638908 bytes, checksum: 3ee166e7d6818cac639935061f63d082 (MD5) / Made available in DSpace on 2016-08-31T17:39:40Z (GMT). No. of bitstreams: 1 moraes_cp_me_bot.pdf: 1638908 bytes, checksum: 3ee166e7d6818cac639935061f63d082 (MD5) Previous issue date: 2016-07-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O efeito de estímulo de uma característica biológica por baixas doses de um composto considerado tóxico, mas que em altas doses tem efeito inibitório é denominado efeito hormesis. Estímulos de crescimento em plantas têm sido verificados após a aplicação de subdoses de alguns herbicidas, incluindo o glyphosate. Nesse contexto, o presente trabalho teve por objetivo avaliar as respostas de crescimento de plantas de Brachiaria decumbens submetidas a diferentes doses de glyphosate. Foram realizados dois estudos em casa de vegetação, ambos em delineamento inteiramente casualizado (DIC). No primeiro estudo foram realizados três experimentos com seis repetições, sendo no experimento 1 testada uma curva de dose-resposta com nove doses do herbicida glyphosate (0; 22,5; 45; 90; 180; 360; 720; 1440 e 2880 g e.a. ha-1). Nos experimentos dois e três foram aplicadas onze doses do herbicida glyphosate (0; 2,8125; 5,625; 11,25; 22,5; 45; 90; 180; 360; 720 e 1440 g e.a. ha-1). No estudo 2 para a avaliação de subdoses com efeito hormesis realizou-se quatro experimentos, em DIC com oito repetições e dois tratamentos (testemunha e dose de 11,25 g e.a. ha-1). Para ambos os estudos foram coletadas oito plantas de vasos sem aplicação para a determinação da biomassa inicial dos experimentos. Nos experimentos do estudo 1 foram realizadas avaliações de fitointoxicação aos 0, 7, 14 e 21 dias após a aplicação (DAA), além da coleta de oito plantas por vaso de cada tratamento para determinação de massa fresca e massa seca. Além disso, realizou-se a quantificação de massa fresca e seca total dos vasos aos 21 DAA, sendo essa metodologia também adotada para os experimentos do estudo 2. Os resultados do estudo 1 indicaram que: em doses acima de 45 g e.a. ha-1 foi possível obter 80% de controle das plantas de B. decumbens; a aplicação de baixas doses de glyphosate estimulou o aumento da biomassa das plantas de B. decumbens, com valores máximos alcançados na subdose de 11,25 g e.a. ha-1 de glyphosate. O segundo estudo indicou que a aplicação de subdose de 11,25 g e.a. ha-1 de glyphosate promoveu tanto estímulo quanto inibição de crescimento, demonstrando haver variabilidade de resposta das plantas à essa subdose.

Submitted by VITOR MULLER ANUNCIATO (vitor.muller@gmail.com) on 2018-04-20T22:14:14Z No. of bitstreams: 1 DissertaçãoANUNCIATOparaImpressão.pdf: 3297037 bytes, checksum: 5946e7250c31b4a24ba3c90890cb6318 (MD5) / Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2018-04-23T11:13:16Z (GMT) No. of bitstreams: 1 anunciato_vm_me_botfca.pdf: 3297037 bytes, checksum: 5946e7250c31b4a24ba3c90890cb6318 (MD5) / Made available in DSpace on 2018-04-23T11:13:16Z (GMT). No. of bitstreams: 1 anunciato_vm_me_botfca.pdf: 3297037 bytes, checksum: 5946e7250c31b4a24ba3c90890cb6318 (MD5) Previous issue date: 2018-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Muito já foi e ainda vem sendo estudado sobre os efeitos clássicos de dose-resposta dos herbicidas e uma outra vertente que vem surgindo são as respostas bifásicas, que incluem hormesis, caracterizada por doses baixas de um herbicida que causa estímulo e inibição em dose elevada. Assim como o estímulo pode ser benéfico na agricultura em algumas aplicações, porem quando ocorre em plantas não alvo, o efeito de hormesis pode-se tornar um problema. Nesse trabalho foram realizados quatro experimentos. Um experimento de curva dose-resposta para biótipo resistente e suscetível de Digitaria insularis, resistente ao herbicida glyphosate, avaliando-se altura das plantas, massa fresca e seca e fitotoxicidade (%) aos 7, 14 e 21 dias após a aplicação. Houve também a repetição do mesmo, um experimento com subdosagem de glyphosate para averiguar o efeito das subdosagens no florescimento, avaliando-se o número de panículas emitidos após a aplicação dos tratamentos e o quarto experimento que foi a verificação da germinação, índice de velocidade de germinação e peso de sementes provindas do terceiro experimento. O efeito de estímulo das subdoses foram constatados em todos os experimentos sendo que diferentes faixas de doses causaram o efeito de hormesis nos biótipos de D.insularis, resistente e suscetível havendo aumento de altura, massa, peso de sementes e velocidade de germinação e diminuição do tempo necessário para emissão das inflorescências. Esses efeitos podem conceder uma grande vantagem para a disseminação dessa espécie, auxiliando a alteração da flora de plantas infestantes. / Currently much has been studied about the classic dose-response effects of herbicides and another aspect that is emerging are the biphasic responses, which include hormesis, a biphasic dose-response phenomenon characterized by low dose stimulation and high dose inhibition. Just as the stimulus may be beneficial in agriculture in several applications, when this stimulus occurs in non-target plants, the effect of hormesis can become a problem. In this work, a dose-response curve experiment was performed for resistant and susceptible biotypes of Digitaria insularis, resistant to the glyphosate herbicide and evaluating plant height, fresh and dry mass and phytotoxicity (%) at 7, 14 and 21 days after application. The second experiment was the repetition of the firs. An experiment with subdoses of glyphosate are performed to investigate the effect of the subdoses on flowering, evaluating the number of panicles emitted after the application of the treatments and the fourth experiment that was the verification of the germination, germination speed index and seed weight from the third experiment. The effect of subdoses stimulation was observed in all the experiments, with different dose ranges causing the stimulus in the D.insularis biotypes, resistant and susceptible, increasing height, mass, seed weight and germination speed and reduced the time required for inflorescence emission. These effects can give a great advantage to the spread of this species, helping to change the flora of weeds.