<p> Barley coleoptiles were observed to be remarkably variable in height at 72 hr of germination. The objective or the study presented here was to analyze this variation in growth among coleoptiles and to attempt to determine its cause. The first step in this analysis of the variation was to determine the growth patterns of 900 individual coleoptiles by measuring their heights periodically during their growth period. In determining the cause for the variation, genetic, environmental, hormonal, metabolic and cytoplasmic factors were considered. For example, since gibberellin and kinetin have been implicated in the control of cell division and cell elongation these growth factors were supplied exogenously to germinating seedlings in an attempt to stimulate uniform growth of all coleoptiles. In similar studies, the effect or physical conditions and co2 on coleoptile growth was determined variation in growth is shown by any one of a number of parameters. Proteins, however, because they are closer to gene activity than the others are a better indicator of whether the variation in growth is caused at a fundamental level. Variations similar to those in coleoptile height were found in the amino acid analysis of different types of coleoptiles. Experiments were also done to determine if a genetic component was responsible for the variation in coleoptile growth. There was no correlation between germination pattern of a seedling and that of its progeny; therefore, the variation in growth was attributed to differences in cytoplasmic constituents of individual coleoptiles. </p> / Thesis / Doctor of Philosophy (PhD)

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No. of bitstreams: 1 DissRBA.pdf: 3602024 bytes, checksum: 525d570f80b6ccb445f7c59a1884a872 (MD5) Previous issue date: 2016-08-08 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The Brazillian savanna is one of the largest vegetation with 2,036,448 km2, about 22% of the national territory. This bioma is considered a global hotspot (Mittermeier et al., 2004) and consists of three biomes: tropical fields, grasslands and dry forests (Batalha, 2011; Brasil, 2015). Cerrado flora has a high species richness with herbs, shrubs, tree and vines, totaling 12,356 species occurring spontaneously, as well as a native vascular flora (ferns and phanerogams) totaling 11,627 species (Mendonça et al., 2008) .However, the chemical potential of its plant species is still underutilized. Research plants with allelopathic activity comes against the need to introduce new alternatives in the management of agricultural pests. Studies on the biological effects of these chemical compounds represent an important tool for the development of more specific agrochemicals natural and less harmful to the environment. Piptocarpha rotundifolia (Less.) - Baker belongs to the Asteraceae family, considered the most representative of the brazilian cerrado eudicotyledons, but there are few published works that deal with potential investigations phytotoxic of this species and its secondary metabolites. Thus, the main objective of this study was to analyze the phytotoxic potential of P. rotundifolia extracts, fractions and subfractions on target species of vegetables and weeds and the mode of action of the same. In the first step of this work, an extraction in order of increasing polarity was done and the phytotoxic potential of crude extracts was evaluated on the growth of wheat coleoptile, germination and seedling growth of mono and eudicotyledons invasive and vegetable species: wild poinsettia (Euphorbia heterophylla L.), guinea grass (Megathyrsus maximus J.), onion (Allium cepa L.) and sesame (Sesamum indicum L.), respectively, as well as the evaluation of the root sesame metaxylem cell growth. The acetone extract (D) was selected for the fractionation, due the mass (2370 mg) and and the inhibitory activity on the growth of wheat coleoptile good as on the germination growth indicator target species (onion and sesame) and invasive (wild poinsettia and guinea grass). This fractions and subfractions were also tested on the growth of wheat coleoptile and those who had higher incomes and inhibitory activity (D1 and D1A) were selected for the following bioguided fractioning. After, a liquid-liquid extraction was performed using the extracts 1 (hexane), 2 (ethyl acetate) and 3 (aqueous) and, among these, the extract 2 showed inhibitory activity on the growth of wheat coleoptile and also on the germination and growth of the target species, as well as significantly reduced metaxylem cell root growth of sesame seedlings. Therefore, this extract was refractionated by a countertop chromatography column, and the fraction with the highest income was denominated (2L), then refractioned. The resulting subfractions were tested only growing wheat coleoptile. To complete the survey, a chemical profile analysis was conducted using the extracts, fractions and subfractions of P. rotundifolia from both extraction methodologies, performing the ultra efficiency liquid chromatography technique, which has found a compound identified as glaucolide b and two other compounds known to the genre. Thus, the species Piptocarpha rotundifolia shown as promissing in the search of phytotoxic compounds due to their phytotoxic activity presented by their compounds. / O cerrado é uma das mais extensas formações vegetais brasileiras com 2.036.448 km2, representando 22% do território nacional. O cerrado é considerado um hotspot mundial (Mittermeier et al., 2004) formado por três biomas: campos tropicais, savanas e florestas estacionais (Batalha, 2011; Brasil, 2015). A flora do cerrado apresenta uma elevada riqueza de espécies, com plantas herbáceas, arbustivas, arbóreas e cipós, totalizando 12.356 espécies que ocorrem espontaneamente, além de uma flora vascular nativa (pteridófitas e fanerógamas) somando 11.627 espécies (Mendonça et al., 2008). No entanto, o potencial químico de suas espécies vegetais ainda é subutilizado. A investigação de plantas com atividade alelopática vem de encontro com a necessidade de se apresentar novas alternativas no manejo integrado de pragas agrícolas. Estudos realizados sobre os efeitos biológicos destes compostos químicos representam uma importante ferramenta para o desenvolvimento de agroquímicos naturais mais específicos e menos prejudiciais ao ambiente. Piptocarpha rotundifolia (candeia) (Less.) – Baker, planta pertencente à família Asteraceae, embora seja considerada a maior representante das eudicotiledôneas do cerrado brasileiro, existem poucos os trabalhos publicados que tratam de investigações do potencial fitotóxico de seus metabólitos secundários. Sendo assim, o principal objetivo deste trabalho foi analisar o potencial fitotóxico dos extratos, frações e subfrações de P. rotundifolia sobre espécies-alvo de hortaliças e invasoras e o modo de ação dos mesmos. Na primeira etapa deste trabalho, foi realizada uma extração em ordem crescente de polaridade, onde o potencial fitotóxico dos extratos brutos foi avaliado sobre o crescimento de coleóptilos de trigo, germinação e crescimento de plântulas de espécies invasoras e de hortaliças mono e eudicotiledôneas: amendoim-bravo (Euphorbia heterophylla L.), capim-colonião (Megathyrsus maximus J.), cebola (Allium cepa L.) e gergelim (Sesamum indicum L.), respectivamente, bem como a avaliação do crescimento de células do metaxilema radicular de gergelim (Sesamum indicum L.). O extrato acetônico (D) foi selecionado para o fracionamento devido ao bom rendimento (2,370g), e apresenta uma atividade inibitória sobre o crescimento de coleóptilos de trigo (Triticum aestivum L.) bem como sobre a germinação crescimento de espécies-alvo indicadoras (cebola e gergelim) e invasoras amendoim-bravo e capim-colonião. Suas frações e subfrações foram também ensaiadas sobre o crescimento de coleóptilos de trigo e as que apresentaram maiores rendimentos e atividade inibitória (D1 e D1A) foram selecionadas para os fracionamentos bioguiado subsequentes. Dando sequência aos estudos, foi realizada uma extração líquido-líquido, que originou os extratos 1 (hexânico), 2 (acetato etílico) e 3 (aquoso) e, dentre estes, o extrato acetato etílico apresentou maior atividade inibitória sobre o crescimento de coleóptilos de trigo e também sobre a germinação e crescimento das espécies-alvo, bem como reduziu significativamente o crescimento de células do metaxilema de raízes de plântulas de gergelim. Sendo assim, este extrato foi refracionado em coluna cromatográfica de bancada, sendo a fração com maior rendimento denominada (2L), submetida a novos subfracionamentos. As subfrações resultantes foram testadas apenas em crescimento com coleóptilos de trigo. Para a complementação da pesquisa foi realizada uma análise do perfil quimico dos compostos presentes nos extratos, frações e subfrações de P. rotundifolia provenientes de ambas metodologias de extração, utilizando a técnica de cromatografia líquida de ultra eficiência, onde foi encontrado um composto identificado como glaucolide b, e outros dois compostos já conhecidos para o gênero. Sendo assim, a espécie Piptocarpha rotundifolia mostra-se como promissora na busca de compostos fitotóxicos, devido à atividade inibitória apresentada pelos compostos presentes nos extratos ou frações.