xii, 89 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Lipid membranes are a basic structural element of all cells. They provide a framework for the physical organization of the cell, act as a scaffold for numerous proteins, and serve as the host site for countless chemical reactions integral to cell function. Several key problems in membrane biophysics hinge on reliable methods for measuring membrane material properties. Properties such as rigidity, fluidity, charge density, etc., are important factors that govern membrane structure and function. As such, we need controllable, reliable, and quantitative methods of probing membrane material properties. In pursuit of such methods, we completed two related projects that, while distinct, aimed to create and apply quantitative measures of membrane material properties to current problems in biophysics. The first of these two lines of inquiry centered on the pervasive, pathogenic family of mycobacteria that is known to not only cause several diseases but also to survive prolonged periods of dehydration. We developed an experimental model system that mimics the structure of the mycobacterial envelope consisting of an immobile hydrophobic layer supporting a two-dimensionally fluid, glycolipid-rich outer monolayer. With this system, we show that glycolipid containing monolayers, in great contrast to phospholipid monolayers, survive desiccation with no loss of integrity, as assessed by both fluidity and protein binding, revealing a possible cause of mycobacterial persistence. In the second line of inquiry, we developed another general platform for probing membrane material properties that has produced the first reported observations of viscoelasticity in lipid membranes. We utilized recently developed microrheological techniques on freestanding lipid bilayer systems using high speed video particle tracking. The complex shear modulus of the bilayers was extracted at a variety of temperatures that span the liquid-ordered to disordered phase transition of the membranes. At many temperatures measured, the membranes displayed viscoelastic behavior reminiscent of a Maxwell material, namely elastic at high frequencies and viscous at low frequencies. Moreover, the viscoelastic behavior was suppressed at the critical phase transition temperature where the membranes behave as a purely viscous fluid. Surprisingly, the viscoelastic behavior was found in all of several distinct membrane compositions that were examined. / Committee in charge: Dr. Daniel Steck, Chair; Dr. Raghuveer Parthasarathy, Research Advisor; Dr. Darren Johnson; Dr. Heiner Linke; Dr. John Toner

Orientador: Edson Lazarini / Banca: Marco Eustáquio de Sá / Banca: Lúcia Helena Pereira Nóbrega / Resumo: Os herbicidas glifosato e paraquat vêm sendo utilizados por produtores de soja, visando à dessecação da cultura. O presente trabalho teve por objetivo avaliar a utilização destes herbicidas, aplicados em diferentes estádios reprodutivos, como dessecantes para a cultura da soja. Para tanto, um experimento foi desenvolvido no ano agrícola 2005/06, em delineamento experimental de blocos casualizados, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 2x3x3, ou seja, duas cultivares, a MG/BR 46 (Conquista), de ciclo médio e a MSOY 6101, de ciclo precoce, dois herbicidas dessecantes (paraquat e o glifosato) e uma testemunha (sem aplicação de dessecante) e três épocas de aplicação (estádios R6, R7 e R8). Cada parcela experimental constou de dez linhas de 15 m de comprimento, espaçadas de 0,45 m, perfazendo 67,5 m2. A produção de sementes, massa de 100 sementes, teor de água (antes das aplicações dos dessecantes e aos 2, 4, 6, 8 e 10 dias após) e a qualidade fisiológica das sementes, no ápice e na base da planta, foram avaliadas. Diante dos resultados obtidos pode-se concluir que os dessecantes são eficientes na redução do teor de água das sementes quando comparados à testemunha, sendo o paraquat mais eficiente que o glifosato; não há efeito da aplicação dos dessecantes quanto à produtividade e massa de 100 sementes; a aplicação dos dessecantes influencia, de forma semelhante, o teor de água e a qualidade fisiológica das sementes nas duas partes da planta avaliadas (ápice e base); o glifosato influencia negativamente a qualidade fisiológica de sementes, principalmente, quando avaliada por meio do teste de comprimento de radícula; o paraquat não altera a qualidade fisiológica das sementes; as sementes obtidas com aplicação de dessecantes no estádio R6 são de qualidade fisiológica inferior às obtidas com aplicação nos estádios R7 e R8. / Abstract: The herbicides glyphosate and paraquat have been used by Brazilian soybean productors to obtain crop desiccation. This study aimed to evaluate the use of the herbicides glyphosate and paraquat as desiccants for the soybean crop. An experiment was conducted in the 2005/06 agricultural season and the experimental design was a randomized block with four repetitions. The treatments were arranged in a factorial scheme 2x3x3, using two varieties, MG/BR 46 (Conquista), a mid-cycle one, and MSOY 6101, an early-cycle one, two desiccant herbicides (paraquat and glyphosate), a control (without the desiccant application) and three seasons of application (stage R6, R7 and R8). Each one of the experimental area consisted of 10 lines 15 m long, spaced by 0.45 m, comprising an area of 67,5 m2. It was evaluated the seed production, mass of 100 seeds, water content (before the desiccant applications and 2, 4, 6, 8 and 10 days after that) from the apex and base of the plant as well as the physiologic quality of seeds. The results obtained made possible to conclude that the desiccants were effective in reducing the water content of seeds when compared to control, paraquat being the more effective one. There was no effect of desiccant applications related to soybean productivity and mass of 100 seeds. Desiccate application influences in a similar form the content of water and the physiologic quality of the seeds in different parts of the plants evaluated (apex and base). Glyphosate influences negatively in the physiological quality of seeds, mainly when evaluated through the test of root length. Paraquat do not modify the physiologic quality of the seeds. Seeds obtained with desiccants application in R6 stage showed lower physiologic quality compared to those obtained with application in the R7 and R8 stage. / Mestre

Made available in DSpace on 2015-03-26T13:36:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1244434 bytes, checksum: 7dab8f29bf5c537dbacff755c9f4ff0f (MD5) Previous issue date: 2012-02-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / On germination, orthodox seeds become intolerant of desiccation. In this condition, these seeds may be a useful model for studies of recalcitrance, in order to elucidate structural and biochemical attributes associated with desiccation sensitivity. Here, we evaluated the loss of desiccation tolerance (DT) in Adenathera pavonina germinating seeds, by following the ability of seeds to germinate after desiccation following various periods of preimbibition. DT was progressively lost during germination, and seeds with radicle length of 1 mm did not withstand drying up to 13% of moisture content. By the rates of electrolyte leakage, it was observed that membrane system was damaged when 60-hour imbibed seeds were dried. It was also observed that dehydration decreased the activity of superoxide dismutase, however catalase, peroxidase and ascorbate peroxidase activities remained unchanged. Three groups of heat shock proteins were detected in fresh seeds, but with the progress of germination the number and intensity of its bands declined. Relative DNA content assessment was done by flow citometry. These analyses showed that the resumption of cell cycle coincided with the complete los of DT. / Ao longo da germinação, sementes ortodoxas tornam-se intolerantes a dessecação e, por isso, têm sido utilizadas em estudos que tentam elucidar as alterações bioquímicas e estruturais associadas com a sensibilidade à dessecação. O presente estudo teve como objetivo avaliar a perda da tolerância à dessecação (TD) durante a germinação de sementes ortodoxas da espécie Adenanthera pavonina, através da sobrevivência das sementes após a secagem realizada em seguida de diferentes períodos de pré-embebição. A TD foi gradativamente perdida ao longo da germinação, de modo que sementes com raiz primária com 1 mm de comprimento não sobreviveram após sua secagem até o grau de umidade inicial (13%). Pelas taxas de extravasamento de eletrólitos verificou-se que o sistema de membranas de sementes em estágio avançado de germinação (60 horas) foi comprometido após a secagem. Também foi observado que as atividades das enzimas catalase, peroxidase e peroxidase do ascorbato não foram tão prejudicadas após a secagem quanto a enzima dismutase do superóxido. Em sementes frescas foram detectadas três classes de proteínas resistentes ao calor e houve redução na intensidade de suas bandas com o avanço da germinação. O conteúdo relativo de DNA nuclear foi analisado por citometria de fluxo, e verificou-se que a retomada do ciclo celular coincidiu com a completa perda da TD.

Submitted by Leticia de Aguila Moreno null (leticia-moreno@ig.com.br) on 2017-05-10T17:06:46Z No. of bitstreams: 1 Dissert. Leticia Moreno.pdf: 1497532 bytes, checksum: f856281196b266bffabba1eca36f929c (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-10T19:10:49Z (GMT) No. of bitstreams: 1 moreno_la_me_bot.pdf: 1497532 bytes, checksum: f856281196b266bffabba1eca36f929c (MD5) / Made available in DSpace on 2017-05-10T19:10:49Z (GMT). No. of bitstreams: 1 moreno_la_me_bot.pdf: 1497532 bytes, checksum: f856281196b266bffabba1eca36f929c (MD5) Previous issue date: 2017-01-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O feijão-caupi (Vigna unguiculata) é uma espécie relativamente bem estudada, contudo faltam informações sobre a aquisição da qualidade fisiológica ao longo da maturação. Determinar o período em que cada componente da qualidade fisiológica é adquirido permite um ajuste no momento ideal da colheita e consequentemente uma colheita no período em que a semente se encontra com o máximo de qualidade fisiológica. Este trabalho teve como objetivo, determinar quando sementes de Vigna unguiculata adquirem qualidade fisiológica, incluindo a aquisição de tolerância à dessecação e a longevidade. O estudo foi realizado na Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Faculdade de Ciências Agronômicas - Laboratório de Análise de Sementes - Departamento de Produção e Melhoramento Vegetal (DPMV), Campus de Botucatu-SP. A produção de sementes foi realizada em abril de 2015, seguida de coleta e caracterização morfológica das sementes nos estádios reprodutivos 17, 20, 23, 25, 28, 31, 34, 37 e 40 dias após a antese (DAA). Para cada estádio foi determinado o teor de água, massa fresca, massa seca, germinação e vigor nas sementes frescas. Em seguida sementes foram submetidas a secagem e foi realizado o teste de germinação para se determinar a aquisição de tolerância à dessecação. As sementes secas foram então armazenadas à 35°C e 75% umidade relativa, para caracterizar a aquisição de longevidade. A qualidade fisiológica (germinação, tolerância à dessecação, vigor e longevidade) em feijão-caupi é adquirida ao longo da maturação da semente. O acúmulo de massa seca se iniciou próximo aos 17 DAA e atingiu o máximo aos 31 DAA. A germinação foi iniciada aos 28 DAA e atingiu seu máximo aos 37 DAA. A tolerância à dessecação foi iniciada a partir dos 28 DAA atingindo seu máximo aos 31 DAA. O vigor e a longevidade foram iniciados a partir dos 31 DAA apresentando seus máximos aos 37 DAA. / Cowpea (Vigna unguiculata) is a relatively well-studied specie, but lack information on the acquisition of physiological quality throughout maturation. Determine the period in which each physiologic component is obtained allows an adjustment in the optimal time of harvesting a crop and consequently the period in which seed acquire the maximum physiological quality. This study aimed to determine when Vigna unguiculata seeds acquire physiological quality, including acquisition of desiccation tolerance and longevity. The research was conducted at the Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Faculty of Agricultural Science - Laboratory of Seed Analysis - Department of Plant Breeding and Production, Botucatu-SP. Seed production was performed at the beginning of the year 2015, followed by collection and morphological characterization of the seeds in the reproductive stages 17, 20, 23, 25, 28, 31, 34, 37 and 40 days after anthesis (DAA). For each stage was determined the water content, fresh weight, dry weight, germination and vigor on fresh seeds. Then seeds were submitted to drying and carried out the germination test to determine the acquisition of desiccation tolerance and longevity. The dried seeds were then stored at 35 ° C and 75% relative humidity, to characterize the acquisition of longevity. The physiological quality (germination, desiccation tolerance, vigor and longevity) of Vigna unguiculata is acquired during seed maturation, after the maximum dry matter accumulation. The dry matter accumulation began close to 17 DAA and reached the maximum at 31 DAA. Germination was acquired at 28 DAA and reached its maximum at 37 DAA. The desiccation tolerance was acquired from 28 DAA reaching its maximum at 31 DAA. The vigor and longevity were acquired from 31 DAA showing their maximum to 37 DAA.

Made available in DSpace on 2014-06-11T19:29:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-09-05Bitstream added on 2014-06-13T18:59:29Z : No. of bitstreams: 1 malaspina_ic_me_ilha.pdf: 368557 bytes, checksum: 14dc250dd450b03d6d480aa91dce1c60 (MD5) / Os herbicidas glifosato e paraquat vêm sendo utilizados por produtores de soja, visando à dessecação da cultura. O presente trabalho teve por objetivo avaliar a utilização destes herbicidas, aplicados em diferentes estádios reprodutivos, como dessecantes para a cultura da soja. Para tanto, um experimento foi desenvolvido no ano agrícola 2005/06, em delineamento experimental de blocos casualizados, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 2x3x3, ou seja, duas cultivares, a MG/BR 46 (Conquista), de ciclo médio e a MSOY 6101, de ciclo precoce, dois herbicidas dessecantes (paraquat e o glifosato) e uma testemunha (sem aplicação de dessecante) e três épocas de aplicação (estádios R6, R7 e R8). Cada parcela experimental constou de dez linhas de 15 m de comprimento, espaçadas de 0,45 m, perfazendo 67,5 m2. A produção de sementes, massa de 100 sementes, teor de água (antes das aplicações dos dessecantes e aos 2, 4, 6, 8 e 10 dias após) e a qualidade fisiológica das sementes, no ápice e na base da planta, foram avaliadas. Diante dos resultados obtidos pode-se concluir que os dessecantes são eficientes na redução do teor de água das sementes quando comparados à testemunha, sendo o paraquat mais eficiente que o glifosato; não há efeito da aplicação dos dessecantes quanto à produtividade e massa de 100 sementes; a aplicação dos dessecantes influencia, de forma semelhante, o teor de água e a qualidade fisiológica das sementes nas duas partes da planta avaliadas (ápice e base); o glifosato influencia negativamente a qualidade fisiológica de sementes, principalmente, quando avaliada por meio do teste de comprimento de radícula; o paraquat não altera a qualidade fisiológica das sementes; as sementes obtidas com aplicação de dessecantes no estádio R6 são de qualidade fisiológica inferior às obtidas com aplicação nos estádios R7 e R8. / The herbicides glyphosate and paraquat have been used by Brazilian soybean productors to obtain crop desiccation. This study aimed to evaluate the use of the herbicides glyphosate and paraquat as desiccants for the soybean crop. An experiment was conducted in the 2005/06 agricultural season and the experimental design was a randomized block with four repetitions. The treatments were arranged in a factorial scheme 2x3x3, using two varieties, MG/BR 46 (Conquista), a mid-cycle one, and MSOY 6101, an early-cycle one, two desiccant herbicides (paraquat and glyphosate), a control (without the desiccant application) and three seasons of application (stage R6, R7 and R8). Each one of the experimental area consisted of 10 lines 15 m long, spaced by 0.45 m, comprising an area of 67,5 m2. It was evaluated the seed production, mass of 100 seeds, water content (before the desiccant applications and 2, 4, 6, 8 and 10 days after that) from the apex and base of the plant as well as the physiologic quality of seeds. The results obtained made possible to conclude that the desiccants were effective in reducing the water content of seeds when compared to control, paraquat being the more effective one. There was no effect of desiccant applications related to soybean productivity and mass of 100 seeds. Desiccate application influences in a similar form the content of water and the physiologic quality of the seeds in different parts of the plants evaluated (apex and base). Glyphosate influences negatively in the physiological quality of seeds, mainly when evaluated through the test of root length. Paraquat do not modify the physiologic quality of the seeds. Seeds obtained with desiccants application in R6 stage showed lower physiologic quality compared to those obtained with application in the R7 and R8 stage.

abstract: This study performs numerical modeling for the climate of semi-arid regions by running a high-resolution atmospheric model constrained by large-scale climatic boundary conditions, a practice commonly called climate downscaling. These investigations focus especially on precipitation and temperature, quantities that are critical to life in semi-arid regions. Using the Weather Research and Forecast (WRF) model, a non-hydrostatic geophysical fluid dynamical model with a full suite of physical parameterization, a series of numerical sensitivity experiments are conducted to test how the intensity and spatial/temporal distribution of precipitation change with grid resolution, time step size, the resolution of lower boundary topography and surface characteristics. Two regions, Arizona in U.S. and Aral Sea region in Central Asia, are chosen as the test-beds for the numerical experiments: The former for its complex terrain and the latter for the dramatic man-made changes in its lower boundary conditions (the shrinkage of Aral Sea). Sensitivity tests show that the parameterization schemes for rainfall are not resolution-independent, thus a refinement of resolution is no guarantee of a better result. But, simulations (at all resolutions) do capture the inter-annual variability of rainfall over Arizona. Nevertheless, temperature is simulated more accurately with refinement in resolution. Results show that both seasonal mean rainfall and frequency of extreme rainfall events increase with resolution. For Aral Sea, sensitivity tests indicate that while the shrinkage of Aral Sea has a dramatic impact on the precipitation over the confine of (former) Aral Sea itself, its effect on the precipitation over greater Central Asia is not necessarily greater than the inter-annual variability induced by the lateral boundary conditions in the model and large scale warming in the region. The numerical simulations in the study are cross validated with observations to address the realism of the regional climate model. The findings of this sensitivity study are useful for water resource management in semi-arid regions. Such high spatio-temporal resolution gridded-data can be used as an input for hydrological models for regions such as Arizona with complex terrain and sparse observations. Results from simulations of Aral Sea region are expected to contribute to ecosystems management for Central Asia. / Dissertation/Thesis / Ph.D. Aerospace Engineering 2012

Entre os vegetais existem duas estratégias distintas para superar as condições de estresse hídrico que condicionam a sensibilidade a dessecação (SD) que está associada a mecanismos de evitação e a tolerância a dessecação (TD) que envolve suportar o estresse hídrico diretamente no nível dos tecidos e no nível subcelular. Sabe-se que os custos acoplados aos mecanismos de dessecação e reidratação em espécies TD são elevados, e provavelmente superiores aos de espécies SD. Desta forma, a coexistência de espécies com estas estratégias, como ocorre no ambiente epifítico da Cidade Universitária Armando Sales de Oliveira (CUASO), induzem questões quanto a as vantagens relativas de espécies TD sobre SD. Devido aos altos custos da estratégia TD é possível propor que estas deveriam apresentar um ganho médio de carbono superior a de espécies SD durante o período favorável (com disponibilidade hídrica). Além disso, também é razoável esperar que as distintas formas de uso da água, vinculadas às estratégias, poderiam facilitar o convívio de espécies TD e SD através da segregação de nichos. Com intuito de verificar essas hipóteses, foram realizadas análises relacionadas a estrutura de comunidade de epífitas da CUASO e, a partir destas, a detecção da associação espacial mais freqüente, que resultou composta por Pleopeltis hirsutissima (TD) e Microgramma squamulosa (SD). Estas espécies foram então selecionadas para avaliar parâmetros associados à dinâmica do uso da água, assimilação líquida de carbono, dinâmica da capacidade de uso da luz, estado de hidratação foliar e pigmentos fotossintéticos. Os resultados apontaram que espécies de ambas as estratégias não apresentam sinais de estresse crônico no ambiente estudado. Os dados reforçaram as respostas contrastantes de TD e SD, refletindo as formas distintas de lidar com os recursos e condições do ambiente. Ao contrário do esperado, P. hirsutissima não apresentou uma assimilação de carbono superior a M. squamulosa, indicando que o ganho de carbono não é um dos fatores possíveis na compensação dos custos acoplados a sua estratégia (TD). Porém, os resultados apresentados quanto a dinâmica da capacidade de uso da luz sugerem que a coexistência é facilitada pela segregação de nichos de luz, sendo a espécie TD mais heliófila do que a espécie SD / In land plants the resistance to drought can be accomplished by two main strategies. One involves mainly dehydration avoidance mechanisms and the other is based on the ability to withstand drought at the tissues and down to subcellular levels. The former is found on the desiccation sensitive plants (DS) and the last describes the desiccation tolerant plants (DT). The metabolic costs of the desiccation tolerance mechanisms are probably high, at least when considering the cessation of photosynthesis during anabiosis - a condition that is absent in drought avoidance strategies. The coexistence of drought avoiders and desiccation tolerant plants in the same substrate and condition can rise some questions about the relative advantages of each strategy when submitted to similar water regime. We ask whether desiccation tolerant plants have a compensatory carbon gain under a watering regime that induces frequent anabiosis or cumulative damage in drought avoidance have a detrimental effect comparable to the costs of the desiccation tolerance. An analysis of the epiphytic plant community associated to the trees of the CUASO urban landscape showed a very frequent co-occurring species pair including the desiccation sensitive Microgramma squamulosa and a desiccation tolerant Pleopeltis hirsutissima, both cryptogams of the same plant family. These species were thoroughly examined regarding the patterns of light, water and carbon dynamics together with pigments concentration during cycles of natural drought and wet climate field conditions. These observations were complemented with experimental induction of different water and light regimes. The results showed no sign of chronic stress in both plants living at the same condition but allowed us to identify large distinctions in resource use patterns. A compensatory carbon assimilation was not found in P.hirsutissima. Both species have similar CO2 assimilation values. Experimental induction of drought in different light regimes allowed to verify a relative advantage in desiccation tolerant P.hirsutissima in comparison to the desiccation sensitive M.squamulosa under high irradiance values. Furthermore, light curve analysis suggest that they share the same tree but their niches differ in light intensity regime allowing the high frequency of co-occurrence observed in the field

Diversas espécies de anuros da família Leptodactylidae se reproduzem em corpos dágua sazonais, temporários e mantidos exclusivamente por chuvas. Em períodos de estiagem prolongada a poça pode secar completamente, ocasionando elevadas taxas de mortalidade de ovos e girinos dessas espécies, podendo exercer forte pressão seletiva na evolução de mecanismos de resistência e sobrevivência nas fases iniciais do desenvolvimento. Algumas espécies de girinos conseguem sobreviver cerca de cinco dias fora dágua o que pode proporcionar uma adaptação vantajosa, porque possibilita a sobrevivência dos girinos por um período que pode ser suficiente para a reincidência de novas chuvas e restabelecimento do corpo dágua. Apesar dessa capacidade de sobrevivência, pouco se sabe sobre as possíveis modificações que a desidratação pode causar na locomoção e na morfologia durante o desenvolvimento desses animais. O presente trabalho teve como objetivo avaliar o efeito do estresse hídrico: (1) no nível de sobrevivência e perda de massa corpórea; (2) no desempenho locomotor; (3) na morfologia externa (morfometria linear) e interna, analisando tanto o volume total quanto o volume visceral (estereologia); e (4) no tempo até metamorfose após o estresse. Utilizamos girinos de duas espécies de anuros, Leptodactylus fuscus (Leptodactylinae) e Physalaemus nattereri (Leiuperinae), ambas as espécies se reproduzem em corpos dágua temporários, em áreas com estação seca definida estando, portanto sujeitas as mesmas pressões seletivas. Além disso, as duas espécies apresentam modos reprodutivos diferentes, podendo apresentar diferentes graus de resistência ao estresse hídrico. Os girinos das duas espécies foram divididos em dois grupos, os que ficaram em água (grupo controle) e os que foram submetidos ao estresse hídrico (grupo tratamento), por três períodos de tempo (12, 24 e 72 horas). Houve diferenças significativas para valores de perda de massa entre os grupos controle e tratamento em ambas as espécies, sendo o grupo tratamento que mais perdeu massa corpórea em todos os períodos, além disso, quase metade dos girinos de P. nattereri morreram em 36 horas de estresse. Não houve diferenças significativas para os dados de desempenho locomotor e volume total entre os grupos testado para girinos de L. fuscus, mas houve diferenças morfometricas significantes nos componentes relacionados a cauda e no volume visceral, onde, o intestino do grupo tratamento foi menor que do controle. Já em P. nattereri, houve diferenças significativas entre os grupos testados para desempenho locomotor, volume total, morfometria da cauda e volume visceral, sendo o estomago e anexo do tratamento maior que do controle. Nossos resultados sugerem que a exposição ao estresse hídrico não afeta significativamente a morfologia e o desempenho locomotor dos girinos de L. fuscus. No entanto, girinos de P. nattereri apresentaram uma sensibilidade ao estresse hídrico prolongado, principalmente sobre o seu desempenho locomotor. / Several species of frogs (Leptodactylidae) breed in temporary pools maintained exclusively by rainfall. These pools easily dry out causing high mortality of eggs or tadpoles thereby possibly exerting strong selective pressure on the evolution of resistance mechanisms and survival in the early stages of development. However, the tadpoles of some species can survive up to five days in pools that are drying out, needing only a humid substrate for development which can provide an advantageous adaptation, because it enables the survival of tadpoles for a period that may be enough for the recurrence of new rains and restoration of the water body. Despite this ability to survive out of water, it is not known which possible damages dehydration stress causes in tadpoles during their ontogeny. The aim of this study was to evaluate the effect of hydric stress on: (1) the level of survival and weight loss; (2) locomotor performance; (3) external (linear morphometry) and internal morphology, analyzing the total volume and visceral volume (stereology); and (4) the time of development after stress. We used tadpoles of two species, Leptodactylus fuscus (Leptodactylinae) and Physalaemus nattereri (Leiuperinae), both species breed in temporary ponds in areas with well-defined dry season therefore these species are subject to the same selective pressure. In addition, the two species show different reproductive modes, and may possess different degrees of resistance to water stress. To this end, the tadpoles were divided into two groups, those who stayed in 100 ml of water (control group) and those that were subjected to hydric stress (treatment group) for three time periods (12, 24 and 72 hours). Significant differences for weight loss were found between the groups (control/treatment) in both species, with the treatment group losing more weight in all stress levels. Furthermore almost half of P. nattereri tadpoles died within 36 hours of stress. There was no significant difference for locomotor performance and total volume between control group and treatment group of L. fuscus tadpoles, but morphometric analyses indicated a significant difference in the components related to tail and visceral volume, with the gut of the treatment group was lower than the control. In P. nattereri tadpoles, there were significant differences between the groups tested for locomotor performance, total volume, tail morphometry and visceral volume, with the stomach of the treatment group being greater than in the control group. Our results suggest that hydric stress has a significant effect on locomotion and morphology of P. nattereri tadpoles, but not in L. fuscus.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Morningglory is an annual plant reproduced by seeds. Seed germination occurs in streams during spring and summer making it difficult to control. Its occurrence has increased in soybean crops in southern states by the exclusive use of the herbicide glyphosate in weed control. This species has seed dormancy caused by impermeable to water, whose absorption is prevented by the seminal tegument. The possibility of using effective methods to overcome dormancy of seeds of bindweed would be ideal for studies of management of these species in agroecosystems as this would result in more uniform plant stands. This study aimed to: evaluate methods aimed at breaking dormancy of seeds of three species of morningglory, and investigate whether there are differences in dormancy between species of this weed (Chapter I); select alternative techniques in weed management prior to sowing of soybean by desiccation with glyphosate, alone and in combination with residual herbicides and selective culture, and also in post -emergency soybeans, with or without the application of glyphosate (Chapter II). In the experiment of scarification, sulfuric acid treatment (98%) resulted in increases in germination varies according to the species examined. Ipomoea undivided was less sensitive to treatment, for Ipomoea triloba, soaking the seeds for 10min in H2SO4 showed better germination. Already in Ipomoea purpurea, the response was linear and the best germination of this species occurred in time of 20min. Mechanical scarification enhanced germination of three species, because it promotes a break in the integument allowing more water uptake by seed. Soaking in KNO3 (0.2% v/v) promoted germination below 40% for the three species to morningglory. Seed exposure to radiation Ipomoea triloba ultrasound for 45 and 60 min resulted in germination percentage above 70%, but for Ipomoea purpurea and Ipomoea indivisa germination was below 50%. The results of experiment management of morningglory showed that the treatments applied in the pre-drying in soybean planting this species is not adequately controlled, controlling less than 80%. But the assessment at 14 DAT, treatments T3 (glyphosate + diclosulam) and T2 (glyphosate + clorimuron) controlled respectively 88 and 86%. In general, the highest grain yields were obtained when combining the treatments of drying with application of glyphosate V2 and V5 stages of soybeans, or just in V5, except for T1 (glyphosate - 720) and T4 (glyphosate + imazethapyr - 720 + 90). T3 (glyphosate + diclosulam - 720 + 25.2) stood out positively desiccation on pre-seeding, controlling the flow of seedling emergence in morningglory (81% at 28 DAT) and also in productivity grains (3.116 kg ha-1) when it was applied post-emergence glyphosate in soybeans. The application of the herbicide glyphosate has shown effective results in the management of morningglory. Therefore, it is necessary the use of combined applications of herbicides. The integrated management of weeds must not dismiss the use of herbicides, but control of the morningglory in soybean requires a management that includes addition of chemical control, several cultural practices, and therefore will require more investment by the producer but to have a greater return due to increased profitability. / A germinação das sementes de cordas-de-viola ocorre em fluxos durante a primavera e verão dificultando seu controle. As sementes apresentam dormência causada principalmente pela impermeabilidade do tegumento seminal à água. A possibilidade de se utilizar métodos eficazes na superação da dormência de sementes de cordas-de-viola é importante em estudos de manejo de Ipomoea spp. em agroecossistemas, pois resultaria em populações mais uniformes. Este trabalho teve por objetivos: (i) avaliar métodos capazes de superar a dormência de sementes de três espécies de cordas-de-viola e investigar se há diferenças na dormência entre as espécies desta planta daninha (Capítulo I) e (ii) selecionar alternativas de controle de cordas-de-viola antecedendo a semeadura da soja RR® através da dessecação com o herbicida glifosato, aplicado isolado e em associação com herbicidas residuais seletivos à cultura; e também em pós-emergência da soja RR®, com ou sem a aplicação do glifosato (Capítulo II). No experimento I (superação de dormência de sementes de cordas-de-viola), o tratamento com ácido sulfúrico (H2SO4) à 98 % resultou em incrementos na germinação das sementes variando de acordo com a espécie analisada. Ipomoea indivisa foi a espécie menos sensível ao tratamento; enquanto que em Ipomoea triloba , a imersão das sementes por 10min em H2SO4 apresentou melhor germinação. Já, em Ipomoea purpurea, a resposta foi linear e a maior percentagem de germinação ocorreu no tempo de 20min. A escarificação mecânica do tegumento seminal favoreceu a germinação das três espécies, pois promoveu uma ruptura no tegumento permitindo melhor embebição de água pela semente; enquanto que a imersão das sementes das três espécies de corda-de-viola em nitrato de potássio (KNO3) a 0,2% v/v, proporcionou germinações inferiores a 40 %. A exposição das sementes de Ipomoea triloba à radiação de ultrasom por 45 e 60min resultou em germinações das sementes maiores que 70%; porém para Ipomoea indivisa e Ipomoea purpúrea, a germinação foi inferior a 50%. Os resultados do experimento de manejo de cordas-de-viola em soja RR® (Capítulo II) mostraram que os tratamentos aplicados na dessecação em pré-semeadura da soja RR não controlaram satisfatoriamente esta planta daninha, com controles em geral inferiores 80 %; exceto nos tratamentos com as combinações de glifosato (720 g e.a. ha-1) com diclosulam (25,2 g i.a. ha-1) e glifosato (720 g e.a. ha-1) com clorimuron (20 g i.a. ha-1), onde os controles foram acima de 85%. Em geral, as maiores produtividades de grãos foram obtidas quando se associou os tratamentos de dessecação com a aplicação de glifosato em pós-emergência da soja RR nos estádios V2 e V5 ou apenas em V5; exceto para os tratamentos glifosato (720 g e.a. ha-1) e a combinação de glifosato (720 g e.a. ha-1) com imazetapir (90 g i.a. ha-1). O manejo de plantas daninhas em soja RR® não deve descartar o uso de herbicidas, porém o controle de cordas-de-viola necessita que se integre além do controle químico, outras práticas culturais, e consequentemente serão necessários mais investimentos pelo produtor, mas que terá retorno em função do aumento da rentabilidade por área.

Anhydrobiotic organisms have the remarkable ability to lose extensive amounts of body water and survive in an ametabolic, suspended animation state. Distributed to various taxa of life, these organisms have evolved strategies to efficiently protect their cell membranes and proteins against extreme water loss. At the molecular level, a variety of mutually non-exclusive mechanisms have been proposed to account particularly for preserving the integrity of the cell membranes in the desiccated state. Recently, it has been shown that the dauer larva of the nematode Caenorhabditis elegans is anhydrobiotic and accumulates high amounts of trehalose during preparation for harsh desiccation (preconditioning), thereby allowing for a reversible desiccation / rehydration cycle. Here, we have used this genetic model to study the biophysical manifestations of anhydrobiosis and show that, in addition to trehalose accumulation, the dauer larvae exhibit a systemic chemical response upon preconditioning by dramatically reducing their phosphatidylcholine (PC) content. The C. elegans strain daf-2 was chosen for these studies, because it forms a constitutive dauer state under appropriate growth conditions. Using complementary approaches such as chemical analysis, time-resolved FTIR-spectroscopy, Langmuir-Blodgett monolayers, and fluorescence spectroscopy, it is shown that this chemical adaptation of the phospholipid (PL) composition has key consequences for their interaction with trehalose. Infrared-spectroscopic experiments were designed and automated to particularly address structural changes during fast hydration transients. Importantly, the coupling of headgroup hydration to acyl chain order at low humidity was found to be altered on the environmentally relevant time scale of seconds. PLs from preconditioned larvae with reduced PC content exhibit a higher trehalose affinity, a stronger hydration-induced gain in acyl chain free volume, and a wider spread of structural relaxation rates during lyotropic transitions and sub- headgroup H-bond interactions as compared to PLs from non-preconditioned larvae. The effects are related to the intrinsically different hydration properties of PC and phosphatidylethanolamine (PE) headgroups, and lead to a larger hydration-dependent rearrangement of trehalose-mediated H-bond network in PLs from preconditioned larvae. This results in a lipid compressibility modulus of ∼0.5 mN/m and 1.2 mN/m for PLs derived from preconditioned and non-preconditioned larvae, respectively. The ensemble of these changes evidences a genetically controlled chemical tuning of the native lipid composition of a true anhydrobiote to functionally interact with a ubiquitous protective disaccharide. The biological relevance of this adaptation is the preservation of plasma membrane integrity by relieving mechanical strain from desiccated trehalose- containing cells during fast rehydration. Finally, the thermo-tropic lipid phase behavior was studied by temperature-dependent ATR-FTIR and fluorescence spectroscopy of LAURDAN-labeled PLs. The results show that the adaptation to drought, which is accomplished to a significant part by the reduction of the PC content, relies on reducing thermo-tropic and enhancing lyotropic phase transitions. The data are interpreted on a molecular level emphasizing the influence of trehalose on the lipid phase transition under biologically relevant conditions by a detailed analysis of the lipid C=O H-bond environment. The salient feature of the deduced model is a dynamic interaction of trehalose at the PL headgroup region. It is proposed here that the location of trehalose is changed from a more peripheral to a more sub-headgroup-associated position. This appears to be particularly pronounced in PLs from preconditioned worms. The sugar slides deeper into the inter-headgroup space during hydration and thereby supports a quick lateral expansion such that membranes can more readily adapt to the volume changes in the swelling biological material at reduced humidity. The data show that the nature of the headgroup is crucial for its interaction with trehalose and there is no general mechanism by which the sugar affects lipidic phase transitions. The intercalation into a phosphatidylethanolamine-rich membrane appears to be unique. In this case, neither the phase transition temperature nor its width is affected by the protective sugar, whereas strong effects on these parameters were observed with other model lipids. With respect to membrane preservation, desiccation tolerance may be largely dependent on reducing phosphatidylcholine and increasing the phsophatidylethanolamine content in order to optimize trehalose headgroup interactions. As a consequence, fast mechanical adaptation of cell membranes to hydration-induced strain can be realized.