Abiotic stresses are one of the major limiting factors of plant growth and thus crop productivity. Exposure to these stresses, including temperature and UV, cause physiological and epigenetic changes in plants. Such changes may be inherited in the progeny of stressed plants, and may change their ability to respond to stress. To understand the ability of plants to inherit an epigenetic stress memory as well as the physiological manifestations of such a memory, we propagated both stressed and control plants and compared the progeny under both normal and stressed conditions. In addition to wild-type plants we used Dicer-like mutants dcl2, dcl3 and dcl4, as Dicers have been linked to RNA-directed DNA methylation, a form of epigenetic memory. These studies revealed that leaf number decreases in the progeny of stressed plants, and bolting occurs earlier in the progeny of temperature stressed plants but later in the progeny of UV-C stressed plants. Transposons were also re-activated in the progeny of stressed plants. While heat shock transcription factor 2A increased expression in the progeny of heat stressed plants, many genes involved in DNA repair and histone modifications decreased. DCL2 and DCL3 appeared to be more important in transgenerational stress memory than DCL4. However, all dcl plants were generally not significantly different than wild-type plants, indicating that a single DCL deficiency may be compensated for by another DCL. / xiv, 246 leaves : ill. ; 29 cm

This study was undertaken to determine the effect of vegetation structure (the ratio of re-seeding to re-sprouting plants) on post-fire catchment water yield. Plant communities are the only components of mountain catchments which can be manipulated to augment water supplies on any practical scale. Burning, which is one of the options available to catchment managers, reduces plant biomass and increases water yield by reducing transpiration and interception losses. Communities dominated by re-seeding species tend to recover more slowly after fires than when sprouters predominate. The rate of vegetation recovery will determine the rate at which streamflow returns to pre-fire levels. Sprouters may use more water than seeders in the early post-fire period by virtue of their greater leaf area, which both increases interception and transpiration losses. Leaf area development could be used as a simple determinant of post-fire water yield if transpiration losses per unit leaf area are similar in seedlings and sprouters. In this study, a comparison was made of the transpiration rates of seedlings and sprouters of Protea nitida after a fire in Swartboskloof (Cape Province) in 1987. Plant water potentials were determined (index of the degree of stress) and leaf stomatal conductances were measured. Results indicate that transpiration rates are similar throughout the year except during the short summer drought period when the seedlings have comparatively low transpiration rates (< 1 mmo1 m-2 s-1 compared to 2-3 mmo1 m-2 s-1 of the sprouter), and i immediately after the first winter rains where the seedlings have comparatively high rates (approxi.mately 4 mmol m-2 s-1 compared to 2 mmol m-2s-1.) The 1ow summer rates are thought to be the result of drought stress induced by limited water supply and the shallow root systems of the seedlings. The higher winter rates suggest that the shallow surface roots of the seedlings respond quickly to increased surface moisture. Differences in root structure (Le. shallow seedling roots and well-developed deep sprouter roots) rather than regeneration mode appear to be responsible for the marginal differences observed in transpiration rates. These differences are expected to disappear as seedling roots develop and occupy the profile. Leaf area could therefore, be used as a determinant of catchment water yield. / Thesis (M.Sc.)-University of Natal, 1990

Bibliography: leaves 187-216 / xxi, 216 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1987

Made available in DSpace on 2014-06-11T19:26:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-24Bitstream added on 2014-06-13T20:34:45Z : No. of bitstreams: 1 000755829.pdf: 2108564 bytes, checksum: 4f4daa3d9e0c5226baf19fdd8a878477 (MD5) / Dentre aspectos mais importantes para o sucesso da agricultura irrigada destaca-se o manejo da água aplicada. No mercado existe uma diversidade de metodologias e instrumentos para tal fim, entretanto, o monitoramento do nível de água no solo utilizando o tensiômetro tem se mostrado eficaz. Nesse trabalho foram avaliados dois métodos de manejo da irrigação conhecidamente de baixo custo, um baseado na tensão da água no solo e o outro com base da depleção da água disponível, com o objetivo de verificar qual deles promove maior produtividade de grãos para a cultura do feijoeiro (Phaseolus vulgaris L.) em três diferentes texturas de solo. O experimento foi dividido em três ensaios, cada um correspondendo a uma textura de solo (arenosa, média e argilosa). Os tratamentos foram compostos por cinco níveis de tensão (– 30, – 40, – 50, – 60 e – 70 kPa) e cinco níveis de depleção (30, 40, 50, 60 e 70% da AD), com quatro repetições delineados em blocos casualizados. O experimento foi desenvolvido em ambiente protegido no Departamento de Solos e Recursos Ambientais (UNESP/FCA), Botucatu - SP. Avaliou-se os parâmetros: Número de vagens por planta (NVP); Produção de vagens por planta (PVP, g); Comprimento da vagem (COMPV, cm); Número de grãos por vagem (NGV); Peso de grãos por vagem (PGV, g); Peso de 100 grãos (P100G, g) e Produção de grãos (PG, g planta-1). Para o solo de textura arenosa não foram encontradas diferenças significativas entre os métodos de irrigação, entretanto, as maiores produtividades de grãos de feijão deram-se para a tensão de – 30 kPa, resultando em 12,10 g planta-1 e 11,04 g planta-1 para 40% da AD. No solo argiloso os melhores resultados foram obtidos com a utilização do método da depleção, pois a produtividade de grãos atingiu 15,36 g planta-1 em 30% da AD, diferindo do solo de textura média onde o oposto foi verificado utilizando... / One of the most important contributors to the success of irrigated agriculture is an efficient management of the water applied by irrigation. Despite indirectly evaluating the water deficit of a produce, soil water tension control has proven to be effective. This study tested which of the irrigation management criteria, tension or depletion-based, yields a greater productivity from crops of the common bean Phaseolus vulgaris. The experiment was conducted in three different soil textures and for that, three tests were needed, one for each texture (sandy, medium and clay). Treatments comprised of five tensions (– 30, – 40, – 50, – 60 and – 70 kPa) and five levels of depletion (30, 40, 50, 60 and 70% of AD), with four replications designed in randomized blocks. The experiment took place in a protected environment in the Natural Resources / Soil Sciences Department (22º30’ S; 48°15’ W and 830 meters) within the Lageado Experimental Farm, property of Faculdade de Ciências Agronômicas of UNESP – Campus of Botucatu, São Paulo State. The following variables were analyzed: number of pods per plant (NVP); Pod production per plant (PVP, g); Pod length (COMPV, cm); Number of grains per pod (NGV); Grain weight per pod (PGV, g); weight of 100 grains (P100G, g) and grain production (PG, g plant-1). The irrigation management using the tension criterion showed the highest production rate in the sandy soil with a tension of – 30 kPa, resulting in 12.10 g plant-1; the clay soil reached a productivity rate of 13.8 g plant-1 corresponding to a – 30 kPa tension. The medium-textured soil resulted in 12.11 g plant-1 for a tension of – 30 kPa. In regard to water depletion in the soil, the highest bean productivity rate for clay soil was 15.36 g plant-1 to 30% of AD. The highest rate in sandy soil was 11.04 g plant-1 to 40% AD and finally, the medium-textured soil had a 30% depletion that produced ...

Orientador: Hélio Grassi Filho / Banca: Antônio de Padua Sousa / Banca: Rodrigo Domingues Barbosa / Resumo: Dentre aspectos mais importantes para o sucesso da agricultura irrigada destaca-se o manejo da água aplicada. No mercado existe uma diversidade de metodologias e instrumentos para tal fim, entretanto, o monitoramento do nível de água no solo utilizando o tensiômetro tem se mostrado eficaz. Nesse trabalho foram avaliados dois métodos de manejo da irrigação conhecidamente de baixo custo, um baseado na tensão da água no solo e o outro com base da depleção da água disponível, com o objetivo de verificar qual deles promove maior produtividade de grãos para a cultura do feijoeiro (Phaseolus vulgaris L.) em três diferentes texturas de solo. O experimento foi dividido em três ensaios, cada um correspondendo a uma textura de solo (arenosa, média e argilosa). Os tratamentos foram compostos por cinco níveis de tensão (- 30, - 40, - 50, - 60 e - 70 kPa) e cinco níveis de depleção (30, 40, 50, 60 e 70% da AD), com quatro repetições delineados em blocos casualizados. O experimento foi desenvolvido em ambiente protegido no Departamento de Solos e Recursos Ambientais (UNESP/FCA), Botucatu - SP. Avaliou-se os parâmetros: Número de vagens por planta (NVP); Produção de vagens por planta (PVP, g); Comprimento da vagem (COMPV, cm); Número de grãos por vagem (NGV); Peso de grãos por vagem (PGV, g); Peso de 100 grãos (P100G, g) e Produção de grãos (PG, g planta-1). Para o solo de textura arenosa não foram encontradas diferenças significativas entre os métodos de irrigação, entretanto, as maiores produtividades de grãos de feijão deram-se para a tensão de - 30 kPa, resultando em 12,10 g planta-1 e 11,04 g planta-1 para 40% da AD. No solo argiloso os melhores resultados foram obtidos com a utilização do método da depleção, pois a produtividade de grãos atingiu 15,36 g planta-1 em 30% da AD, diferindo do solo de textura média onde o oposto foi verificado utilizando... / Abstract: One of the most important contributors to the success of irrigated agriculture is an efficient management of the water applied by irrigation. Despite indirectly evaluating the water deficit of a produce, soil water tension control has proven to be effective. This study tested which of the irrigation management criteria, tension or depletion-based, yields a greater productivity from crops of the common bean Phaseolus vulgaris. The experiment was conducted in three different soil textures and for that, three tests were needed, one for each texture (sandy, medium and clay). Treatments comprised of five tensions (- 30, - 40, - 50, - 60 and - 70 kPa) and five levels of depletion (30, 40, 50, 60 and 70% of AD), with four replications designed in randomized blocks. The experiment took place in a protected environment in the Natural Resources / Soil Sciences Department (22º30' S; 48°15' W and 830 meters) within the Lageado Experimental Farm, property of Faculdade de Ciências Agronômicas of UNESP - Campus of Botucatu, São Paulo State. The following variables were analyzed: number of pods per plant (NVP); Pod production per plant (PVP, g); Pod length (COMPV, cm); Number of grains per pod (NGV); Grain weight per pod (PGV, g); weight of 100 grains (P100G, g) and grain production (PG, g plant-1). The irrigation management using the tension criterion showed the highest production rate in the sandy soil with a tension of - 30 kPa, resulting in 12.10 g plant-1; the clay soil reached a productivity rate of 13.8 g plant-1 corresponding to a - 30 kPa tension. The medium-textured soil resulted in 12.11 g plant-1 for a tension of - 30 kPa. In regard to water depletion in the soil, the highest bean productivity rate for clay soil was 15.36 g plant-1 to 30% of AD. The highest rate in sandy soil was 11.04 g plant-1 to 40% AD and finally, the medium-textured soil had a 30% depletion that produced ... / Mestre

Homologous recombination represents a DNA repair pathway. Its role in a plant cell is not limited to double strand break repair. It also extends to genome evolution via rearranging of DNA sequences, and has an important application in foreign DNA integration in the plant genome. Our study demonstrated that effects exerted by stress on homologous recombination and genome stability are not restricted to the exposed generation. The progeny of plants exposed to stress exhibited elevated spontaneous homologous recombination, changes in DNA methylation and higher tolerance to stress. These heritable changes are mediated by an unknown stress-inducible epigenetic signal. Furthermore, we demonstrated that using factors that enhance homologous recombination can improve the efficiency of genetic transformation by Agrobacterium. We have developed and patented a plant growth medium enhancing homologous recombination and significantly increasing the transformation frequency. The role of several other chemicals for the improvement of transformation was also evaluated. / xxi, 246 leaves : ill. ; 29 cm. --

Orientador: Marcelo Menossi Teixeira, Andrea Akemi Hoshino / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-21T05:45:50Z (GMT). No. of bitstreams: 1 Souza_CesarBuenode_D.pdf: 2755272 bytes, checksum: 945d7a45c10893c9a58603f1e04813ef (MD5) Previous issue date: 2012 / Resumo: O Brasil é o maior produtor mundial de cana-de-açúcar e no cenário atual, em que o aumento na busca por energia renovável é visível, o aumento na produtividade da cana é de extremo interesse para o setor sucroalcooleiro. Estresses abióticos influenciam grandemente a produtividade de espécies como a cana e, sendo assim, estudos relacionados com a tentativa de diminuir esse impacto na produtividade são de grande importância. A seca é o estresse ambiental que mais causa prejuízos ao agronegócio e por esse motivo é muito desejável que se desenvolvam novas variedades de cana-de-açúcar que sejam mais tolerantes a esses estresses e com isso o setor sucroalcooleiro será largamente beneficiado. A transgenia é uma das ferramentas utilizadas na produção de novos cultivares comerciais com características agronômicas interessantes e, para o seu sucesso, a identificação de genes com potencial para melhorar essas características faz-se necessária. Sendo assim, o maior objetivo desse trabalho foi a avaliação do potencial biotecnológico de seis genes de cana-de-açúcar que são modulados por seca. Os genes aqui estudados tiveram seu perfil de resposta a seca anteriormente avaliado por microarranjos de DNA e foram selecionados como candidatos para a produção de um novo cultivar de cana-de-açúcar que seja mais tolerante a estresses abióticos. Esses genes foram analisados em plantas transgênicas de tabaco, cana-de-açúcar e/ou Brachypodium. A superexpressão de dois genes de cana em tabaco conferiu maior tolerância a seca e salinidade das plantas transgênicas quando comparadas às selvagens e a proteção de seus usos na produção de plantas tolerantes a estresses abióticos foi solicitada. Há evidências de que um terceiro gene de cana conferira tolerância ao estresse oxidativo em plantas transgências de cana. Além disso, outros três genes de cana foram inseridos em Brachypodium, mas os eventos gerados ainda não foram avaliados. Com o trabalho desevolvido foi, portanto, possível gerar plantas transgênicas tolerantes a estresses abióticos e com isso é possível concluir que a seleção de genes candidatos para melhorias de características agronômicas de interesse através de microarranjos é algo que deve ser explorado e pode-se concluir, ainda, que alguns dos genes analisados estão envolvidos na resposta a seca e/ou aos estresses ambientais em geral / Abstract: Brasil is the largest producer of sugarcane in the world and the seeking for renewable energy is currently visible what makes the increase of sugarcane productivity highly desirable. Abiotic stresses greatly influence the productivity of species such sugarcane. Therefore, studies related to the reduction of these impacts on productivity are highly important. Drought is the environmental stress that causes more damage to agribusiness and because of it the development of new cultivars with higher tolerance to abiotic stresses is desirable since the sugar and ethanol sector will be largely benefited. Transgenic plants production is one of the tools that have been used in the development of new cultivars with interesting agronomic traits and for its success identifying genes that can improve these characteristics is necessary. Thus, the main objective of this study was evaluating the biotechnological potential of six drought-modulated genes from sugarcane. The genes studied here have their drought response profile previously showed by microarray and were selected as candidates for the production of a new sugarcane cultivar with higher tolerance to abiotic stresses. These genes were analyzed in transgenic tobacco, sugarcane and/or Brachypodium plants. The overexpression of two sugarcane genes in tobacco conferred higher drought and salinity tolerance in tobacco plants compared to wild-type and the protection of their uses in the production of plants with higher tolerance to abiotic stress was requested. There are evidences that a third sugarcane gene confers tolerance to oxidative stress in transgenic sugarcane. Furthermore, three other genes were inserted in Brachypodium but these transgenic events were not yet analyzed. With this work was possible to produce transgenic plants that are tolerant to abiotic stresses what let us to conclude that the selection of candidate genes to improve agronomic traits by microarrays is useful and that some of the analyzed genes are involved into drought and/or abiotic stresses in general responses / Doutorado / Genetica Vegetal e Melhoramento / Mestre em Genética e Biologia Molecular

Vegetation stress as a form of degradation is a widespread problem in many catchments in the Eastern Cape province. The Keiskamma is one of the catchments where considerable parts of the thicket biome are stressed. This necessitates an assessment of the status of the thicket biome by way of detecting vegetation stress in the area. The underpinnings of vegetation stress are investigated in this study. As a basic method to evaluate the thicket condition, remotely sensed data were acquired. High resolution ASTER imagery for the Keiskamma area at two different dates (2001 and 2005) was used to compute SVI and NDVI as indicators of vegetation stress conditions. A Digital Elevation Model (DEM) was used to derive slope angle and aspect. By way of digitizing from ortho-photo maps, various land-use types were mapped using Arc View GIS. The relationship between land use, terrain, soil erosion and vegetation stress was established. Field based techniques comprising stomatal conductance measurements were used and compared to remotely sensed data. The SVI and NDVI resultant images expressed similarities in areas depicting vegetation stress conditions at both epochs. A strong linear regression between NDVI and stomatal conductance measurements (mmol/m²) serve to confirm that the NDVI is a reliable indicator of vegetation stress condition. Slope angle and aspect were found to have a significant influence on vegetation stress conditions. Similarly variations in soil moisture and soil surface condition have strong implications for vegetation stress. Amongst other land-use types, abandoned lands were found to have the lowest NDVI values implying an association with the worst vegetation stress scenarios. It was concluded that an element of persistent stress conditions exists amongst the thicket vegetation of the Keiskamma catchment. This was mainly due to land use activities in the area.

Indiana University-Purdue University Indianapolis (IUPUI) / Dehydrins are type II LEA proteins induced in many plants during drought, low temperature, and high salinity to confer stress tolerance. AtERD14 is an Arabidopsis thaliana dehydrin that functions in part of the cold stress pathway. AtERD14 has chaperone-like capabilities that allow it to bind and protect various proteins from dehydration stresses. In order to determine the necessary components for cold induction of AtERD14, AtERD14prom::GFP/GUS and AtERD14prom::AtERD14 in AtERD14 KO constructs were created and stably transformed into A. thaliana. Analysis of the constructs showed the AtERD14 promoter alone was insufficient to respond to cold, and it was necessary to attach the AtERD14 coding region to the promoter to induce a cold response in ERD14. On the other hand, the RD29aprom::GFP/GUS promoter did respond to cold stress, indicating that RD29a does not require its coding region to support an increased amount of reporter activity after cold stress. The protoplast transformation system, while capable of transient expression of introduced constructs in protoplasts, was difficult for use for cold-inducible expression.