Dans le contexte de réchauffement climatique, le maintien des rendements est un enjeu majeur pour la filière viticole. L'augmentation des températures impacte négativement certaines phases clés du développement reproducteur en induisant notamment des phénomènes de coulure ou de pertes précoces d'inflorescence. L'altération du bilan carboné pourrait être un facteur majeur des diminutions de rendements en réponse aux températures élevées et l'évaluation de cette hypothèse permettrait d'ajuster les pratiques pour limiter les effets du réchauffement climatique. Si l'implication du bilan de carbone chez les plantes annuelles semble être à la base des baisses de rendement observées ces dernières années, les choses sont beaucoup moins claires chez des pérennes comme la vigne du fait des très nombreux co-facteurs possible ainsi que de la difficulté à expérimenter dans des conditions totalement contrôlées. Afin de s'affranchir de ces contraintes, notre étude a été réalisée en conditions contrôlées sur la Microvigne, un mutant naturel insensible à l'acide gibberelique et un nouveau modèle d'étude pour la génétique et la physiologie de la vigne. Ce mutant présente un phénotype nain et une floraison et fructification continues le long de l'axe proleptique. L'approche utilisée dans cette étude a consisté à (i) développer un cadre d'analyse adapté à la Microvigne; (ii) décrire l'impact de l'élévation de la température, sur les développements végétatif et reproducteur de la vigne, et plus particulièrement l'avortement des stades précoces du développement reproducteur; (iii) caractériser les changements du bilan de carbone de la Microvigne induits par la contrainte thermique, et enfin (iv) évaluer l'implication potentielle du bilan de carbone dans les phénomènes d'avortement précoces en réponse au stress thermique. Ce travail a permis de mettre en évidence des phénomènes d'avortement complet d'inflorescences en réponse à l'élévation des températures. Par ailleurs, nous avons pu montrer un rôle du statut carboné dans ce phénomène, soit via les teneurs totales en carbohydrates, soit via l'état global des réserves à l'échelle de la plante. Ce travail montre les potentialités su modèle Microvigne et ouvre de nouvelles perspectives pour l'analyse des effets des contraintes abiotiques sur le développement végétatif et reproducteur de la vigne. / Global warming is likely to be a major issue for grapevine yield sustainability in the next years. A common hypothesis is that long-term elevated temperatures may cause the failure of key phases of reproductive development, through their negative impact on carbon balance. However, testing the specific role of plant carbon status on yield elaboration under elevated temperatures is difficult on perennial crops, such as grapevine, and when environment fluctuates. To overcome these difficulties, the present work was conducted under fully controlled environment using a natural, giberrelic acid insensitive mutant of grapevine called Microvine, as a new model for grapevine genetics and physiological studies. This mutant present a dwarf stature and lack of juvenile characteristics leading to the continuous flowering and fruiting even during the first year after sowing. The present study was aimed at (i) developing a framework of analysis for Microvine; (ii) describing vegetative and reproductive developments responses to temperature elevation at whole plant level, and more precisely on early reproductive development abortions; (iii) characterizing grapevine carbon balance responses to temperature; and finally (iv) evaluating carbon balance implication in temperature-dependent early reproductive development abortions. This work shows that complete inflorescence abortions observed in response to temperature were related to carbon status, either expressed though total carbohydrate, or through the level of reserves at the whole plant level. This study opens the way to use Microvine as model to address the impact of climate warming on grapevine vegetative and reproductive developments.

Les diatomées constituent le principal groupe du phytoplancton dans les océans, contribuant à près de 20% de la production primaire globale. Dans leur environnement très variable, les diatomées sont particulièrement efficaces dans leur capacité à ajuster leur activité photosynthétique en dissipant sous forme de chaleur l’énergie lumineuse absorbée en excès, par un processus appelé le « Non-Photochemical Quenching of chlorophyll fluorescence », (NPQ). Chez la diatomée modèle, Phaeodactylum tricornutum, il a été montré que LHCX1, une protéine proche des antennes photosynthétiques, est impliquée dans le NPQ. Par des approches intrégrées de génétique, biologie moléculaire, biochimie, imagerie des cinétiques de fluorescence et spectroscopie ultrarapide, j’ai étudié le rôle de la famille des LHCX chez P. tricornutum. J’ai tout d’abord pu corréler une expression différentielle des 4 gènes LHCX de P. tricornutum avec différentes dynamiques de NPQ et activités photosynthétiques, dans différentes conditions de lumiére et nutriments. En localisant les LHCX dans les differents complexes photosynthétiques et les différents sites de dissipation d’énergie, j’ai pu proposer un modèle de régulation dynamique du NPQ impliquant à court terme principalement LHCX1 au niveau des centres réactionnels, et une autre isoforme, possiblement LHCX3, au niveau des antennes lors d’un stress lumineux prolongé. Enfin, par le criblage d’une série de mutants potentiellement dérégulés dans leur contenu en LHCXs, j’ai pu identifier des lignées avec un NPQ altéré qui pourront constituer des nouveaux outils de recherche. Dans l’ensemble ce travail de thèse a permis de mettre en évidence la diversification fonctionnelle et l’importance de la famille des LHCX dans la fine modulation des capacités de collecte de lumière et de photoprotection, expliquant sans doute en partie le succès des diatomées dans leur environnement très fluctuant. / Diatoms dominate phytoplanktonic communities in contemporary oceans, contributing to 20% of global primary productivity. In their extremely variable environment, diatoms are especially efficient in adjusting their photosynthetic activity by dissipating as heat the light energy absorbed in excess, through a process called “Non-Photochemical Quenching of chlorophyll fluorescence”, (NPQ). In the model diatom Phaeodactylum tricornutum, it has been shown that LHCX1, a photosynthetic antenna-related gene, is involved in the NPQ process. Through integrated approaches of genetics, molecular biology, biochemistry, study of the kinetics of chlorophyll fluorescence yields and ultrafast spectroscopy, I studied the role of the LHCX family in the photoprotection activity of P. tricornutum. I first correlated a differential regulation of the 4 P. tricornutum LHCX genes with different dynamics of NPQ and photosynthetic activity, in different light and nutrient conditions. By localizing the LHCXs in fractioned photosynthetic complexes and the different sites of energy dissipation, I was able to propose a model of dynamic regulation of NPQ capacity involving mainly the LHCX1 in the reaction centers, during short-term high light responses. During prolonged high light stress, the quenching occurs mainly in the antennas, potentially mediated by the LHCX3 isoform. Finally, using photosynthetic parameters, I screened a series of transgenic lines putatively deregulated in their LHCX amount, and I identified lines with altered NPQ, which could represent novel investigation tools. Altogether, this work highlighted the functional diversification and the importance of the LHCX protein family in the fine-tuning of light harvesting and photoprotection capacity, possibly contributing to explain diatoms success in their highly fluctuating environment.

C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO2 concentration around Rubisco in the bundle sheath (BS). Maize CCM has two CO2 delivery pathways to the Bundle Sheath (BS) (respectively via malate, MAL or aspartate, ASP); rates of PGA reduction, carbohydrate synthesis and PEP regeneration vary between BS and Mesophyll (M) cells. For these anatomical and biochemical complexities, C4 plants are highly sensitive to light conditions. Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO2 retrodiffusing from the BS relative to C4 carboxylation processes. This increase in Φ had been theoretically associated with a decrease in biochemical operating efficiency (expressed as ATP cost of gross assimilation, ATP / GA) under low light and, because a proportion of canopy photosynthesis is carried out by shaded leaves, to potential productivity losses at field scale. In C4 leaves, because of the concentric anatomy, light reaches M cells before the deeper BS (Evans et al., 2007), and could alter the energetic partitioning balance between BS and M and potentially cause efficiency losses. In this experimental programme I investigated strategies deployed by C4 plants to adjust operating efficiency under different illumination conditions. Firstly, maize plants were grown under high and low light regimes (respectively HL, 600 vs LL, 100 μE m-2 s-1). Short term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry using an improved modelling approach which does not suffer from elements of circularity. Long term acclimation to low light intensities brought about physiological changes which could potentially increase the operating efficiency under limiting ATP supplies. Secondly, profiles of light penetration across a leaf were used to derive the potential ATP supply for M and BS cells induced by changing light quality. Empirical measurements of net CO2 uptake, ATP production rate and carbon isotope discrimination were made on plants under a low light intensity. The overall conversion efficiency was not affected by light quality. A comprehensive metabolic model highlighted the importance of both CO2 delivery pathways in maize. Further, metabolic plasticity allowed the balancing of ATP and NADPH requirements between BS and M. Finally, I tested the hypothesis that plants can modify their physiology so as to reach a status of higher operating efficiency when exposed to high light and then to low light, so as to mimic the transition which leaves undergo when shaded by newly emerging leaves in a crop canopy. Plants were grown under high light and low light for three weeks, then, HL plants were transferred to low light for a further three weeks. Re-acclimation was very effective in reducing ATP cost of net assimilation under low light intensities. In addition, the hyperbolic leakiness increase observed under low light intensities was not associated to operating efficiency loss. Overall, in the three experimental Chapters I showed compelling theoretical and empirical evidence proving the hypothesis that C4 plants deal with low light conditions and with different light qualities without losing operating efficiency.

This study represents the first comprehensive analysis of gene regulation underlying the distinct categories of resistance afforded to wheat (Triticum aestivum, L.) by different Dn genes. Russian wheat aphid (Diuraphis noxia, Mordv.) feeding on susceptible wheat cultivars causes leaf rolling, chlorosis and the eventual death of the plant. Plants expressing Dn genes are resistant to D. noxia infestation, but different Dn genes afford phenotypically distinct modes of resistance: the Dn1 gene confers an antibiotic effect to lower aphid fecundity; Dn2 confers tolerance to high aphid pressure; and Dn5 confers antixenosis, and aphids do not prefer such plants as hosts. Little is known about the components involved in establishing a successful defence response against D. noxia attack and how these differ between the distinct resistance categories. It is assumed that the Dn genes function as classic R genes in plant defence, being receptors for elicitors in aphid saliva. Upon recognition, defence response signalling is initiated, but the exact mechanics of subsequent cellular events in aphid resistance have only recently come under investigation. Evidence from cDNA microarray and subtractive hybridization experiments indicated the involvement of kinase signalling cascades and photosynthetic proteins in the response against D. noxia. However, expression analysis describing how these processes differ between plants carrying different Dn genes and how these differences account for antibiosis, antixenosis or tolerance had not been conducted. We consequently investigated the downstream components involved in or affected by the generation of these resistance mechanisms by comparing the responses in transcript regulation of Tugela near-isogenic lines with different Dn genes to D. noxia infestation. cDNA-AFLP analysis was selected as an appropriate functional genomics tool, since it is semi-quantitative, does not require prior sequence information and allows for the discovery of novel genes. cDNA-AFLP analysis yielded 121 differentially regulated transcript-derived fragments (TDFs) grouped into eight expression clusters. We cloned and sequenced 49 representative TDFs, which were further classified into five broad functional categories based on inferred similarity to database sequences. Transcripts involved in such diverse processes as stress, signal transduction, photosynthesis, metabolism and gene regulation were found to be differentially regulated during D. noxia feeding. Many TDFs demonstrated homology to proteins with unknown function and several novel transcripts with no similarity to previously published sequences were also discovered. Detailed expression analysis using quantitative RT-PCR and RNA hybridization provided evidence that the time and intensity of induction of specific pathways is critical for the development of a particular mode of resistance. This includes: the generation of kinase signalling cascades and the induction of several ancillary processes such as ubiquitination, leading to a sustained oxidative burst and the hypersensitive response during antibiosis; tolerance as a passive resistance mechanism countering aphid-induced symptoms through the repair or de novo synthesis of photosystem proteins; and the possible involvement of ethylene-mediated wounding pathways in generating volatile organic compounds during antixenosis. This is the first report on the involvement of KCO1, a vacuolar K+ channel, in assisting cytosolic Ca2+-influx and preventing leaf rolling, as well as on the role of iron homeostasis as a gene regulatory mechanism for sustaining the oxidative burst during the antibiotic defence response. This study opens up several areas of investigation heretofore unexplored in cereal-aphid interaction research. Of particular interest is the induction of genes involved in photosynthetic compensation during Dn2 tolerance responses, since these constitute a novel, passive resistance mechanism exclusive to aphid defence as opposed to the active resistance triggered in the presence of the Dn1 gene in the form of a general hypersensitive response. / Dissertation (MSc)--University of Pretoria, 2008. / Genetics / unrestricted

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-27T12:14:16Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese Doutorado Hiram Falcão.pdf: 1589850 bytes, checksum: c86ffb35f5d0263dbd80e96c156b8065 (MD5) / Made available in DSpace on 2017-07-27T12:14:16Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese Doutorado Hiram Falcão.pdf: 1589850 bytes, checksum: c86ffb35f5d0263dbd80e96c156b8065 (MD5) Previous issue date: 2016-02-24 / CAPES / Para o estabelecimento de populações vegetais em ambientes que são heterogêneos no tempo e no espaço, como florestas que passam por processo de regeneração natural, é fundamental a capacidade de apresentar respostas plásticas em atributos funcionais foliares em resposta às variações ambientais. Plantas pioneiras apresentam estratégias ecofisiológicas distintas de plantas de estádios sucessionais tardios, ocupando posições opostas no espectro de economia foliar. No entanto algumas plantas conseguem se estabelecer, ao mesmo tempo, em áreas em diferentes momentos do processo sucessional. Dessa forma, o presente trabalho teve como objetivo avaliar a variação nos atributos funcionais de três espécies de diferentes hábitos, numa cronosequência (inicial (22 anos), intermediária (44 anos), e tardia (+ 60 anos)) de floresta tropical sazonalmente seca em três estações chuvosas consecutivas. As espécies selecionadas foram: Poincianella pyramidalis (Tul.) L.P. Queiroz (Fabaceae), arbórea; Hyptis suaveolens (L.) Poit. (Lamiaceae), herbácea; e Sida galheirensis Ulbr. (Malvaceae), subarbustiva. As duas primeiras são encontradas nos três estádios sucessionais, e a última apenas nos estádios inicial e tardio. Todas as coletas foram realizadas no período chuvoso, no mês de abril, entre os anos de 2012 e 2015. Foram mensuradas as trocas gasosas, o potencial hídrico foliar, o conteúdo e a eficiência no uso dos nutrientes, a área foliar específica, o conteúdo de compostos fenólicos, o custo de construção foliar e o tempo de compensação. As respostas ecofisiológicas das plantas foram influenciadas tanto pelo estádio sucessional quanto pela precipitação entre os anos. De um modo geral, as plantas do estádio tardio apresentaram maiores taxas de trocas gasosas, potencial hídrico, eficiência no uso dos nutrientes e investimento em defesa, especialmente em 2014, o ano mais chuvoso. Além disso, um maior custo de construção foliar e um menor tempo de compensação foram observados nas plantas da área tardia, evidenciando que em áreas preservadas as plantas são mais eficientes no uso da energia. No entanto a variação nos atributos foliares foi mais intensa entre os anos de coleta. Dentre os atributos funcionais, o potencial hídrico apresentou a maior capacidade de aclimatação à variação ambiental, seguido da eficiência no uso dos nutrientes e da área foliar específica. O atributo com a menor capacidade de resposta plástica foi o custo de construção foliar. No entanto esse atributo foi mostrou-se como um dos mais importantes na classificação das plantas de acordo com o estádio sucessional. Os resultados mostram que a água é o principal filtro ambiental que coordena as respostas ecofisiológicas na floresta tropical sazonalmente seca brasileira. No entanto as diferentes espécies captam e utilizam a água disponível de forma distinta, evidenciando uma diferenciação de nicho com relação ao uso da água. A variação nos atributos funcionais em função do estádio sucessional sugere que as espécies analisadas têm a capacidade de ajustar o seu espectro de economia foliar, utilizando-se de estratégia de captação ou de conservação de recursos de acordo com as exigências do ambiente. / For establishing plant populations in environments that are heterogeneous in time and space, as forests that pass through natural regeneration process, it is essential the ability to present plastic responses in leaf functional traits in response to environmental variations. Pioneer plants have different ecophysiological strategies in comparison plants of late successional stages, occupying opposite positions in the leaf economics spectrum. However some plants can be established, at the same time, in areas at different stages in succession process. Thus, this study aimed to evaluate the changes in the functional attributes of three species of different habits, in a chronosequence (early (22 years), intermediate (44 years) and late ( + 60 years)) of a seasonally tropical dry forest in three consecutive rainy seasons. The species selected were: Poincianella pyramidalis (Tul.) L.P. Queiroz (Fabaceae), a tree; Hyptis Suaveolens (L.) Poit. (Lamiaceae), a herb; and Sida galheirensis Ulbr. (Malvaceae), a subshrub. The first two are found in the three successional stages, and the last one only in the early and late stages. All samples were collected in the rainy season, in April, between the years 2012 and 2015. The gas exchange, leaf water potential, the content and the nutrient use efficiencies, specific leaf area, the content of phenolics, the leaf construction cost and payback time, were measured. Ecophysiological responses of plants were influenced both by the successional stage as the rainfall between years. In general, plants from late stage had higher rates of gas exchange, leaf water potential, nutrients use efficiency and investment in defense, especially in 2014, the wettest year. Furthermore, a higher leaf construction cost and a shorter payback time were observed in late area, showing that, in preserved areas, plants are more efficient in energy use. However the variation in leaf traits was more intense between the years of collection. Among the functional traits, the water potential presented the highest acclimatization capacity to environmental variation, followed by the nutrient use efficiencies and specific leaf area. The leaf trait with the lowest plastic response was the leaf construction cost. However, this trait was one of the most important in classifying the plants according to successional stage. The results showed that water is the main environmental filter that coordinates the ecophysiological responses in the Brazilian seasonally tropical dry forest. However the different species capture and utilize the available water separately, showing a niche differentiation related to water use. The variation in functional traits as a function of the succession stages, suggests that the species in this study have the ability to adjust its leaf economics spectrum economy, by using a resource capture or a conservative strategy according to the requirements of the environment.

Made available in DSpace on 2016-01-26T18:56:23Z (GMT). No. of bitstreams: 1 Dissertacao.pdf: 561254 bytes, checksum: 6fe1c6021f8ba849b15380f02e4a3762 (MD5) Previous issue date: 2012-02-06 / Water deficit is one of the main factors limiting agricultural production worldwide, affecting many physiological processes in plants. Based on this context, the study aimed to evaluate the interference of potassium fertilization on physiological responses of two soybean cultivars developed under water deficit, and assess the level of tolerance to water stress among cultivars. For this we tested the following hypotheses: 1) K supplementation in soybean plants grown under water deficiency can contribute to minimize the effects of water shortage on the physiology of the plant, 2) the difference in the level of tolerance to water stress between the cultivars depend directly from the application of K. The experiment was conducted in a greenhouse in 2x2x3 factorial design, ie, two soybean cultivars, water stress at 100% and 40% of the daily replacement of water compared to field capacity (CC), and three levels of supplementation with K which was held at planting. To test the assumptions above, we assessed the following parameters: leaf water potential index, chlorophyll content, membrane leakage, photosynthetic potential and biomass yield. Based on the results, we conclude that: Under conditions of water stress, the K fertilization did not interfere significantly in biomass and physiological parameters evaluated at work. Potassium supplementation promoted a better efficiency of physiological parameters in controlling water status in both cultivars, where the main variables were influenced by the nutrient to the stomatal conductance (gs), maximum rate of carboxylation of Rubisco (Vcmax) and maximum CO2 assimilation (Amax ). K supplementation improved the recovery of photosynthetic plants after rehydration, especially the cultivar Embrapa 48. With respect to the parameters of biomass in water status of control, the BR-16, potassium fertilization increased the production of total dry mass per plant and yield, as the cultivar Embrapa 48, only the latter parameter was influenced by biomass potassium. / A deficiência hídrica é um dos principais fatores limitantes da produção agrícola mundial, afetando diversos processos fisiológicos nas plantas. Com base neste contexto o trabalho o objetivo de avaliar a interferência da adubação potássica nas respostas fisiológicas de duas cultivares de soja desenvolvidas sob dois regimes hídricos. Foi testada a hipótese, de que a suplementação com K em plantas de soja cultivadas sob restrição hídrica poderia contribuir para minimizar os efeitos da falta de água sobre a fisiologia da planta. Para isso foram testadas as seguintes hipóteses: 1) a suplementação de K em plantas de soja cultivadas sob deficiência hídrica pode contribuir para minimizar os efeitos da falta de água sobre a fisiologia da planta; 2) a diferença no nível de tolerância à deficiência hídrica entre as cultivares avaliadas dependerá diretamente da aplicação de K. O experimento foi conduzido em casa de vegetação, em esquema fatorial 2x2x3, ou seja, duas cultivares de soja, deficiência hídrica com 100% e 40% da reposição diária de água em relação à capacidade de campo (CC), e três níveis de suplementação com K que foi realizada no plantio. Para testar as hipóteses consideradas anteriormente, foram avaliados os seguintes parâmetros: potencial de água foliar, índice de conteúdo de clorofila, extravasamento de membrana, potencial fotossintético e rendimento de biomassa. Com base nos resultados, é possível concluir que: Em condições de estresse hídrico, a adubação potássica não interferiu expressivamente nos parâmetros fisiológicos e de biomassa avaliados no trabalho. A suplementação com potássio promoveu uma melhor eficiência dos parâmetros fisiológicos em condição hídrica controle nas duas cultivares, onde as principais variáveis influenciadas pelo nutriente foram à condutância estomática (gs), taxa máxima de carboxilação da Rubisco (Vcmax) e assimilação máxima de CO2 (Amax). A suplementação com K melhorou a recuperação fotossintética das plantas após a reidratação, especialmente na cultivar Embrapa 48. Com relação aos parâmetros de biomassa, em condição hídrica controle, na cultivar BR-16, a adubação potássica aumentou a produção de massa seca total por planta e produção de grãos, já na cultivar Embrapa 48, só a massa se grãos foi influenciado pelo potássio.

Made available in DSpace on 2016-01-26T18:56:34Z (GMT). No. of bitstreams: 1 MARIAAMELIA_AGRONOMIA_OUT2008.pdf: 260166 bytes, checksum: 97be3da67d75f35841f21cc4d8ed3283 (MD5) Previous issue date: 2006-08-25 / Snap bean (Phaseolus vulgaris L.) as a tropical plant from highlands is responsive to environmental stresses, as thermal stresses and water deficiency. This variability can be originated from natural selection or plant breeding processes. The objective of this experiment was to evaluate some parameters in common bean plants submitted to the water stress under application of different salicylic acid doses. Two populations grew in 20L pots until the third leave was developed. They were treated with salicylic acid (zero, 0.025, 0.05 and 0.1mM) three times spaced three days. Plants were kept without water during nine days until they reach water deficit. Quantic efficiency, effective and potential and electron transport rate were measured during and after rehydration. Proline content, SOD activity, soluble protein content and dry matter was measured after 24h of water restoration. The salicylic acid induced alterations, in the population Guarumbé. 'Aporé' showed to be not responsive to salicylic acid for photosynthetic parameters / O feijão (Phaseolus vulgaris L.) é responsivo a estresses térmicos e a deficiência hídrica. Esta variabilidade pode ser oriunda de processos de seleção natural ou de melhoramento de plantas. O objetivo desse experimento foi avaliar alguns parâmetros em plantas de feijão submetidas a estresse hídrico, sob aplicação de diferentes doses de ácido salicílico. Duas populações foram cultivadas em vasos de 20L até o desenvolvimento da terceira folha e tratadas com ácido salicílico (zero, 0,025, 0,05 e 0,1mM) três vezes espaçadas de três dias, ficando sem irrigação por nove dias até atingirem ponto de murcha. As eficiências quânticas efetiva e potencial, e a taxa de transporte de elétrons foram medidas durante e após o estresse. O teor de prolina, atividade de SOD, conteúdo de proteínas totais e massa seca foram medidos 24h após reidratação. O ácido salicílico induziu alterações, na população Guraumbé. O cultivar 'Aporé' demonstrou-se não responsivo ao ácido salicílico para os caracteres fotossintéticos.

Made available in DSpace on 2016-07-18T17:51:07Z (GMT). No. of bitstreams: 1 Dissertacao.pdf: 561254 bytes, checksum: 6fe1c6021f8ba849b15380f02e4a3762 (MD5) Previous issue date: 2012-02-06 / Water deficit is one of the main factors limiting agricultural production worldwide, affecting many physiological processes in plants. Based on this context, the study aimed to evaluate the interference of potassium fertilization on physiological responses of two soybean cultivars developed under water deficit, and assess the level of tolerance to water stress among cultivars. For this we tested the following hypotheses: 1) K supplementation in soybean plants grown under water deficiency can contribute to minimize the effects of water shortage on the physiology of the plant, 2) the difference in the level of tolerance to water stress between the cultivars depend directly from the application of K. The experiment was conducted in a greenhouse in 2x2x3 factorial design, ie, two soybean cultivars, water stress at 100% and 40% of the daily replacement of water compared to field capacity (CC), and three levels of supplementation with K which was held at planting. To test the assumptions above, we assessed the following parameters: leaf water potential index, chlorophyll content, membrane leakage, photosynthetic potential and biomass yield. Based on the results, we conclude that: Under conditions of water stress, the K fertilization did not interfere significantly in biomass and physiological parameters evaluated at work. Potassium supplementation promoted a better efficiency of physiological parameters in controlling water status in both cultivars, where the main variables were influenced by the nutrient to the stomatal conductance (gs), maximum rate of carboxylation of Rubisco (Vcmax) and maximum CO2 assimilation (Amax ). K supplementation improved the recovery of photosynthetic plants after rehydration, especially the cultivar Embrapa 48. With respect to the parameters of biomass in water status of control, the BR-16, potassium fertilization increased the production of total dry mass per plant and yield, as the cultivar Embrapa 48, only the latter parameter was influenced by biomass potassium. / A deficiência hídrica é um dos principais fatores limitantes da produção agrícola mundial, afetando diversos processos fisiológicos nas plantas. Com base neste contexto o trabalho o objetivo de avaliar a interferência da adubação potássica nas respostas fisiológicas de duas cultivares de soja desenvolvidas sob dois regimes hídricos. Foi testada a hipótese, de que a suplementação com K em plantas de soja cultivadas sob restrição hídrica poderia contribuir para minimizar os efeitos da falta de água sobre a fisiologia da planta. Para isso foram testadas as seguintes hipóteses: 1) a suplementação de K em plantas de soja cultivadas sob deficiência hídrica pode contribuir para minimizar os efeitos da falta de água sobre a fisiologia da planta; 2) a diferença no nível de tolerância à deficiência hídrica entre as cultivares avaliadas dependerá diretamente da aplicação de K. O experimento foi conduzido em casa de vegetação, em esquema fatorial 2x2x3, ou seja, duas cultivares de soja, deficiência hídrica com 100% e 40% da reposição diária de água em relação à capacidade de campo (CC), e três níveis de suplementação com K que foi realizada no plantio. Para testar as hipóteses consideradas anteriormente, foram avaliados os seguintes parâmetros: potencial de água foliar, índice de conteúdo de clorofila, extravasamento de membrana, potencial fotossintético e rendimento de biomassa. Com base nos resultados, é possível concluir que: Em condições de estresse hídrico, a adubação potássica não interferiu expressivamente nos parâmetros fisiológicos e de biomassa avaliados no trabalho. A suplementação com potássio promoveu uma melhor eficiência dos parâmetros fisiológicos em condição hídrica controle nas duas cultivares, onde as principais variáveis influenciadas pelo nutriente foram à condutância estomática (gs), taxa máxima de carboxilação da Rubisco (Vcmax) e assimilação máxima de CO2 (Amax). A suplementação com K melhorou a recuperação fotossintética das plantas após a reidratação, especialmente na cultivar Embrapa 48. Com relação aos parâmetros de biomassa, em condição hídrica controle, na cultivar BR-16, a adubação potássica aumentou a produção de massa seca total por planta e produção de grãos, já na cultivar Embrapa 48, só a massa se grãos foi influenciado pelo potássio.

Made available in DSpace on 2016-07-18T17:51:15Z (GMT). No. of bitstreams: 1 MARIAAMELIA_AGRONOMIA_OUT2008.pdf: 260166 bytes, checksum: 97be3da67d75f35841f21cc4d8ed3283 (MD5) Previous issue date: 2006-08-25 / Snap bean (Phaseolus vulgaris L.) as a tropical plant from highlands is responsive to environmental stresses, as thermal stresses and water deficiency. This variability can be originated from natural selection or plant breeding processes. The objective of this experiment was to evaluate some parameters in common bean plants submitted to the water stress under application of different salicylic acid doses. Two populations grew in 20L pots until the third leave was developed. They were treated with salicylic acid (zero, 0.025, 0.05 and 0.1mM) three times spaced three days. Plants were kept without water during nine days until they reach water deficit. Quantic efficiency, effective and potential and electron transport rate were measured during and after rehydration. Proline content, SOD activity, soluble protein content and dry matter was measured after 24h of water restoration. The salicylic acid induced alterations, in the population Guarumbé. 'Aporé' showed to be not responsive to salicylic acid for photosynthetic parameters / O feijão (Phaseolus vulgaris L.) é responsivo a estresses térmicos e a deficiência hídrica. Esta variabilidade pode ser oriunda de processos de seleção natural ou de melhoramento de plantas. O objetivo desse experimento foi avaliar alguns parâmetros em plantas de feijão submetidas a estresse hídrico, sob aplicação de diferentes doses de ácido salicílico. Duas populações foram cultivadas em vasos de 20L até o desenvolvimento da terceira folha e tratadas com ácido salicílico (zero, 0,025, 0,05 e 0,1mM) três vezes espaçadas de três dias, ficando sem irrigação por nove dias até atingirem ponto de murcha. As eficiências quânticas efetiva e potencial, e a taxa de transporte de elétrons foram medidas durante e após o estresse. O teor de prolina, atividade de SOD, conteúdo de proteínas totais e massa seca foram medidos 24h após reidratação. O ácido salicílico induziu alterações, na população Guraumbé. O cultivar 'Aporé' demonstrou-se não responsivo ao ácido salicílico para os caracteres fotossintéticos.

A produção de forragem em pastagens é resultado de um processo complexo e dinâmico onde características estruturais como o arranjo e a distribuição de partes da planta e o padrão de distribuição de luz condicionam respostas fisiológicas e produtivas. A altura de dossel mantida constante pode ser relacionada com respostas produtivas, estruturais e fisiológicas do dossel, possibilitando recomendações de manejo do pastejo. O objetivo do trabalho foi quantificar o efeito da altura de dossel mantida constante em 15, 30 e 45 cm sobre características produtivas e morfo-fisiológicas do capim Xaraés [Brachiaria brizantha (A. Rich) Stapf. cv. Xaraés] submetido à lotação contínua. O estudo foi realizado na Escola Superior de Agricultura Luiz de Queiroz, campus da USP, localizado em Piracicaba SP. Foram avaliados a produção e taxas de acúmulo de forragem, proporção de folhas, colmos e material morto, índice de área foliar (IAF), interceptação luminosa (IL), ângulo foliar e taxas de fotossíntese foliar e de dossel. O delineamento experimental foi o inteiramente casualizado com três tratamentos e três repetições. As unidades experimentais (piquetes) tiveram 120 m2 cada e as alturas de dossel foram mantidas constante utilizando a técnica de mob grazing. O total de forragem produzida e a taxa de acúmulo não variaram com as alturas de dossel estudadas. A massa de forragem total mantida nos pastos esteve diretamente relacionada com a altura de dossel. A maior proporção de folhas nos dosséis mantidos a 15 cm foi acompanhada de menor proporção de colmos, com exceção do final da primavera, em relação àqueles mantidos a 45 cm. No final da primavera maiores proporções de material morto foram encontradas nos dosséis mantidos a 45 cm, não variando com as alturas de dossel do verão ao início do outono. O IAF esteve diretamente relacionado com a altura de dossel apresentando valores médios variando de 1,6 a 3,4 para os dosséis mantidos a 15 e 45 cm, respectivamente. O IAF dos dosséis com valores de 2,5 já apresentavam máximos valores de IL (99%), condição encontrada nos pastos mantidos a 30 cm. O ângulo foliar não sofreu efeito de altura de dossel, com média de 39º em relação à horizontal. A taxa fotossintética média da folha mais jovem completamente expandida foi diminuída 17% quando a altura média de dossel foi aumentada de 15 para 45 cm. As taxas de fotossíntese de dossel simuladas pelo modelo foram aumentadas com incrementos na altura de dossel, alcançando valores máximos nos dosséis mantidos a 30 e 45 cm. O aumento nas taxas fotossintéticas de dossel seguiu o mesmo padrão de resposta do IAF e da IL. A altura de dossel em pastos de capim Xaraés pode ser mantida entre 15 e 45 cm, porém perdas significativas podem ocorrer na assimilação de carbono quando os dosséis são mantidos a 15 cm. / Forage production from pastures is the result of a complex and dynamic process where structural features such as the arrangement and distribution of plant parts and patterns of light distribution condition physiological and productive responses. Canopy height, when kept constant can be related to the productive, physiological and structural responses by the canopy, allowing for the development of grazing management recommendations. The objective of this study was to quantify the effect of canopy height, maintained at 15, 30 and 45 cm on productive, morphological and physiological responses of Xaraes palisadegrass [Brachiaria brizantha (A. Rich) Stapf. cv. Xaraés] under continuous stocking. The study was carried out at Escola Superior de Agricultura \"Luiz de Queiroz\", USP campus, located in Piracicaba - SP. Responses measured included forage production and accumulation rates, the proportion of leaves, stems and dead material, leaf area index (LAI), light interception (LI), leaf angle, and photosynthetic rates of leaf and canopy. The experimental design was completely randomized with three treatments and three replications. Experimental units (paddocks) had 120 m2 each and canopy heights were kept constant using the mob grazing technique. The total herbage yield and accumulation rate did not vary among canopy heights. Forage mass was directly related to the height of the canopy and the largest proportion of leaves in the canopy kept at 15 cm was accompanied by a lower proportion of stems, except in late spring, compared to those kept at 45 cm. In late spring higher proportions of dead material were found in swards kept at 45 cm, but this response did not vary with canopy height from summer to early autumn. Leaf area index was directly related to canopy height, averaging 1.6 to 3.4 for the canopies kept at 15 and 45 cm, respectively. Canopy LAI of 2.5 already showed maximum LI (99%), a condition found in pastures maintained at 30 cm. Leaf angle was not affected by canopy height, with an average of 39 degrees from the horizontal reference. The average photosynthetic rate of the youngest fully expanded leaf decreased by 17% when the average canopy height was increased from 15 to 45 cm. Simulated rates of canopy photosynthesis were increased with increasing canopy height, reaching maximum values in swards kept at 30 cm. The increase in canopy photosynthetic rates followed the same pattern of response of LAI and LI. Canopy height in grazed grass Xaraes palisadegrass can be maintained between 15 and 45 cm, but significant losses can occur in carbon assimilation when the canopies are kept at 15 cm.