Developing oilseeds accumulate oils and seed storage proteins synthesized by the pathways of primary metabolism. Seed development and metabolism are positively regulated at the transcriptional level through the transcription factors belonging to the LAFL regulatory network. The VAL genes encode repressors of the seed maturation program in germinating seeds, but they are also expressed during early stages of seed maturation. VAL1 was identified through a reverse genetics approach as a regulator of seed metabolism, as val1 mutant seeds accumulated elevated levels of storage proteins compared to the wild type. Two VAL1 splice variants were identified, yielding the canonical protein and a truncated protein lacking the plant-homeodomain-like domain important for epigenetic repression. Transcriptomics analysis also revealed that VAL1 is a global epigenetic and transcriptional repressor in developing embryos, though none of the transcripts encoding the LAFL network regulators, including FUSCA3, were affected in val1 embryos. However, VAL1 action is connected specifically to FUSCA3 as 38% of transcripts belonging to the FUSCA3 regulon, but not to other regulons, were largely de-repressed in the absence of VAL1. Based on our model, FUSCA3 activates expression of VAL1 to repress transcription of seed maturation genes without interfering with expression of the core LAFL regulators. / Ph. D.

The buffalo gourd, Cucurbita foetidissima HBK, is a xerophytic perennial native to the southwestern United States and northern Mexico. A vigorous spreading vine, it produces edible oil and protein in the seeds, and edible starch in its fleshy storage root. This study concerns the inheritance of content of each fatty acid in the seed oil of the buffalo gourd, including heritability studies, physiological relationships between the fatty acids, and environmental influence on the oil composition. The mechanisms of fatty acid biosynthesis and desaturation and environmental effects on them are reviewed, as is the inheritance of fatty acid composition in commercial oilseed crops. In this study, crosses were made between plants selected for low or high linoleate content and the progeny analyzed by gas chromatography, using a non-destructive half-seed method. Analyzed seed of extremely high and low linoleate content were planted, and crosses made among the resulting plants. Their progeny were analyzed and half-seeds planted again, to be selfed or sib crossed. The fatty acid composition of buffalo gourd seed was found to be determined by the embryonic genotype. Linoleate and oleate content were negatively correlated, as has been previously shown in this and other species. Heritability of oleate and linoleate content was determined by regression of progeny values on midparent values and found to be approximately 0.86 in the first year, while palmitate gave no significant regression. In the second year, palmitate exhibited a heritability of 0.39, but oleate and linoleate had heritabilities near 0.4. The notable decrease in their heritability was examined by multiple regression analysis of progeny values with environmental parameters and midparent values. A significant regression was obtained with day length for oleate and linoleate content; however, correlations also were found with high and low temperatures during the seed maturation period. The various environmental parameters tested were too strongly correlated to distinguish the causative factor with certainty.

Graduation date: 1994

Biochemical and ultrastructural changes associated with chilling injury (CI) in soybean seeds imbibed at 5°C and 25°C were investigated. Soybean seed germination appeared to be affected by chilling temperatures and initial seed moisture content. Seeds with higher moisture contents exhibited 85% germination, while low moisture content seeds had a 32% germination. Leakage rates were greater in chilled seeds, indicating that membrane integrity in the tissues was impaired at chilling. The low rates of potassium ion leakage between 6 and 24 hours of imbibition compared to the high peroxide levels observed during this period led to the suggestion that lipid peroxidation was a better marker of CI than leakage. Transient changes in lipid hydroperoxide levels were observed in chilled and non-chilled seeds and axes. However, in axes, the increase in lipid hydroperoxides after 12 hours of imbibition at chilling temperatures was associated with an 18% decline in linoleic acid levels of total lipid fraction. Similarly, a 10% decline was observed in the polar lipid fraction. These results suggest that the capacity of seeds to control lipid peroxidation may be an important component in CI and that a consequence of peroxidation is likely to be a loss of fatty acid unsaturation. Sugar levels were not affected by chilling and non-chilling temperatures and no relationship could be established with CI. Antioxidant defense enzymes (catalase and superoxide dismutase) were expressed at chilling and non-chilling temperatures and increases were observed after 24 hours of imbibition which showed an apparent correlation with increases to lipid hydroperoxide levels. Enzyme levels decreased after 48 hours of imbibition at a time which coincided with the decline observed in the peroxide levels. Overall, no marked differences were observed in chilled and non-chilled cells at the ultrastructural level, except that vacuolar reserve mobilization was markedly impeded. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

Made available in DSpace on 2014-06-11T19:35:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-02Bitstream added on 2014-06-13T19:46:24Z : No. of bitstreams: 1 nogueira_dc_dr_ilha.pdf: 465474 bytes, checksum: 73aaf83a41766ac828cf08b26abed5fe (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O uso de sementes com alto nível de vigor é fundamental para o sucesso de um empreendimento agrícola, pois apresentam melhor desempenho em campo, resultando em maior produção. O objetivo do trabalho foi verificar o nível do vigor em sementes de três híbridos de milho submetidas ao envelhecimento acelerado e seus desempenhos em laboratório e em campo. Para tanto sementes dos híbridos AG-5020, AG-8088 e BG-7049 foram envelhecidas artificialmente à 41oC por 0, 48 e 72 horas e secadas em estufa à 38 °C/48 horas para a formação dos diferentes lotes. Experimento 1 – No laboratório, verificou-se o nível de vigor e o desempenho das sementes dos diferentes lotes por meio de análises de germinação, primeira contagem, deterioração controlada, tetrazólio, comprimento de raiz primária e mesocótilo, número de raízes/plântula, massa de matéria seca de plântula e emergência em solo. Experimento 2 – No campo as sementes foram semeadas manualmente em parcelas de 8 linhas de 5m, espaçamento de 0,5m e densidade de 80.000 plantas ha-1. Verificou-se o nível de vigor e o desempenho das plantas em campo pelas avaliações de características morfológicas das plantas, caracteres da espiga e componentes de produtividade. O delineamento experimental foi o inteiramente casualizado com os tratamentos obtidos da combinação 3 x 3 (híbridos x níveis de vigor) com quatro repetições. Em laboratório as sementes mais vigorosas apresentaram melhores desempenhos e em campo proporcionaram a obtenção de maior produtividade, o que se deve principalmente ao maior estande final obtido. As características das plantas e das espigas estão relacionadas ao genótipo de cada híbrido não se verificando efeito do vigor das sementes / The use of seeds with high level of vigor is fundamental to the success of an agricultural development, since its have better performance in the field, resulting in increased production. The objective of this study was to assess the level of vigor in seeds of three maize hybrids submitted to accelerated aging and their performance in laboratory and field. Seeds of AG-5020, AG-8088 and BG-7049 were artificially aged at 41°C for 0, 48 and 72 hours and dried in an stove at 38 °C /48 hours for the formation of the different lots. Experiment 1 – in the laboratory, we found the level of vigor and the performance of different seed lots by means of analysis of germination, first count, controlled deterioration, tetrazolium, length of primary root and mesocotyl, number of roots/seedling, seedling mass dry matter and seedling emergence in soil. Experiment -2 the seeds were manually sown in plots of 8 rows of 5m, 0,5 m spacing and density of 80000 plants ha-1. The level of vigor and performance of plants in the field evaluations of morphological characteristics of plants, components and characters of the spike in productivity. The experimental design was completely randomized treatments obtained with the combination 3 x 3 (hybrid x vigor levels) with four replications. In the laboratory the most vigorous seeds showed better performances and the field higher productivity, which is mainly due to higher final stand. As characteristics of plants and spike are related to the genotype of each hybrid was not observed effect of vigor seeds

Orientador: Marco Eustaquio de Sa / Banca: João Antonio da Costa Andrade / Banca: Kuniko Iwamoto Haga / Banca: Gisele Herbst Vazquez / Banca: Neli Cristina Belmiro dos Santos / Resumo: O uso de sementes com alto nível de vigor é fundamental para o sucesso de um empreendimento agrícola, pois apresentam melhor desempenho em campo, resultando em maior produção. O objetivo do trabalho foi verificar o nível do vigor em sementes de três híbridos de milho submetidas ao envelhecimento acelerado e seus desempenhos em laboratório e em campo. Para tanto sementes dos híbridos AG-5020, AG-8088 e BG-7049 foram envelhecidas artificialmente à 41oC por 0, 48 e 72 horas e secadas em estufa à 38 °C/48 horas para a formação dos diferentes lotes. Experimento 1 - No laboratório, verificou-se o nível de vigor e o desempenho das sementes dos diferentes lotes por meio de análises de germinação, primeira contagem, deterioração controlada, tetrazólio, comprimento de raiz primária e mesocótilo, número de raízes/plântula, massa de matéria seca de plântula e emergência em solo. Experimento 2 - No campo as sementes foram semeadas manualmente em parcelas de 8 linhas de 5m, espaçamento de 0,5m e densidade de 80.000 plantas ha-1. Verificou-se o nível de vigor e o desempenho das plantas em campo pelas avaliações de características morfológicas das plantas, caracteres da espiga e componentes de produtividade. O delineamento experimental foi o inteiramente casualizado com os tratamentos obtidos da combinação 3 x 3 (híbridos x níveis de vigor) com quatro repetições. Em laboratório as sementes mais vigorosas apresentaram melhores desempenhos e em campo proporcionaram a obtenção de maior produtividade, o que se deve principalmente ao maior estande final obtido. As características das plantas e das espigas estão relacionadas ao genótipo de cada híbrido não se verificando efeito do vigor das sementes / Abstract: The use of seeds with high level of vigor is fundamental to the success of an agricultural development, since its have better performance in the field, resulting in increased production. The objective of this study was to assess the level of vigor in seeds of three maize hybrids submitted to accelerated aging and their performance in laboratory and field. Seeds of AG-5020, AG-8088 and BG-7049 were artificially aged at 41°C for 0, 48 and 72 hours and dried in an stove at 38 °C /48 hours for the formation of the different lots. Experiment 1 - in the laboratory, we found the level of vigor and the performance of different seed lots by means of analysis of germination, first count, controlled deterioration, tetrazolium, length of primary root and mesocotyl, number of roots/seedling, seedling mass dry matter and seedling emergence in soil. Experiment -2 the seeds were manually sown in plots of 8 rows of 5m, 0,5 m spacing and density of 80000 plants ha-1. The level of vigor and performance of plants in the field evaluations of morphological characteristics of plants, components and characters of the spike in productivity. The experimental design was completely randomized treatments obtained with the combination 3 x 3 (hybrid x vigor levels) with four replications. In the laboratory the most vigorous seeds showed better performances and the field higher productivity, which is mainly due to higher final stand. As characteristics of plants and spike are related to the genotype of each hybrid was not observed effect of vigor seeds / Doutor

Seed dispersal is a crucial ecological and evolutionary process that allows plants to colonize sites and expand their ranges, while also reducing inbreeding depression and facilitating the spread of adaptive genetic variation. However, our fundamental understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. In recent years, genetic marker methods have furthered our understanding of colonization and range expansion due to seed dispersal. Most investigations focus on regional scales of dispersal, due to low levels of variation in the chloroplast genome (cpDNA), which can serve as an indirect measure of seed dispersal. Here, I employ a whole-genome assay of cpDNA variation in Plagiobothrys nothofulvus to resolve variation due to patterns of seed dispersal within a 400x400 meter section of the Whetstone Savanna Preserve in Central Point, OR, USA. Whetstone is characterized by a mosaic of habitat types, including vernal pools, hummocks of dry prairie, and large Ceanothus cuneatus bushes, as well as a network of vole runways. Plagiobothrys nothofulvus grows in dense patches on hummocks within this prairie. I found evidence of limited seed dispersal in P. nothofulvus, indicated by strong genetic structure over distances of less than 100 meters. There was little evidence that geographic distance predicts genetic distance; environmental features have a stronger influence on dispersal. Habitat preference was the strongest predictor of genetic variation in P. nothofulvus, indicating that it may be a habitat specialist in this prairie. Flower density also accounted for a significant portion of dispersal, which may be a consequence of the annual life history of P. nothofulvus resulting in seasonal turnover and lack of competition with adult plants. Least-cost-path analysis indicated that seeds are secondarily dispersed by small mammals along vole runways. Overall, I found significant evidence that landscape features influence dispersal, even at a very fine spatial scale.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1984 H46 / Master of Science

Call number: LD2668 .T4 1984 I92 / Master of Science