Okra (Abelmuschus esculentus (L) Moench.) is one of the most popular crops within the Malvaceae family of plants. It is a common vegetable eminently cultivated in regions experiencing constraints to manage climate change. In South Africa climate change coupled with aluminium-enriched soils are responsible to drawbacks crop performance. Therefore, it is worthwhile to whether okra will thrive as an alternative crop in the country. Many studies have identified potential of okra to improve yields of resource poor farmers in Africa. The physiological responses of okra seed to variations in aluminium ions and temperature were not determined. Therefore, a study with okra, cv. Clemson Spineless, seed coated and uncoated with B. subtilis, was initiated to assess germination on moist filter paper in 90mm diameter Petri plates. Germination medium consisted of various concentrations of aluminium chloride (AlCl3), 0M, 0.001M, 0.01M, 0.05M and 0.1M. Each aluminium treatment was allocated into incubators adjusted to 22°C, 25°C and 37°C temperatures. This resulted into a 5 x 3 x 2 factorial experiment with five replicates and was conducted in three cycles. Daily scores of germinated seeds were assessed from the second to the fifth day after initiation of germination. During termination, five days after the initiation of the experiment 10 seeds with the longest coleoptiles had their coleoptiles measured using a digital caliper. At the fifth day after initiation of the experiment, coleoptile lengths from 10 seeds per treatment were measured using digital caliper. A total of 50 plates (10 from 37°C in Cycle 1; 30 from 22°C, 25°C and 37°C from Cycle 2; 10 from 37°C in Cycle 3), were selected and germinated were ground and stored at - 20°C before 1H NMR analysis. Metabolites were extracted from 50mg ground seed material with 750 μL methanol-D4 and 750 μL buffer (deuterium oxide + potassium dihydrogen phosphate). The mixture was vortexed for three minutes, sonicated for 20 minutes, centrifuged at 18000 rpms for 20 minutes and the supernatant filtered through cotton wool. Then the supernatant was dispensed into NMR tubes for further 1H NMR spectroscopic processing using a 600 MHz NMR xiii Varian spectrometer to generate magnetic spectra of the fifty samples. Results of this study demonstrated that in all the experimental cycles, regardless of aluminium concentration and bacterial seed coating, 37°C inhibited germination percentages and coleoptile lengths in okra seed germination. Germination percentages and coleoptile lengths of bacteria-coated seeds growing in 25°C were most stimulated at all aluminium concentrations, but not at 0.1M. In this temperature germination percentages and coleoptile lengths were highly influenced by the interaction of aluminium concentrations and bacterial coating, respectively. 1H NMR metabolomic association showed no distinct grouping, but clusters across treatments showed to be linked through a subset of metabolites amongst aluminium concentrations, bacterial seed coating and temperatures, respectively. This infers that treatment variations in both seed and bacterial physiological responses were associated through shared metabolic pathways. In conclusion, the study proved that 25°C provide temperature environment within which B. subtilis can be able to stimulate growth and remediate physiological constraints from aluminium ions during okra seed germination. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Okra (Abelmuschus esculentus (L) Moench.) is one of the most popular crops within the Malvaceae family of plants. It is a common vegetable eminently cultivated in regions experiencing constraints to manage climate change. In South Africa climate change coupled with aluminium-enriched soils are responsible to drawbacks crop performance. Therefore, it is worthwhile to whether okra will thrive as an alternative crop in the country. Many studies have identified potential of okra to improve yields of resource poor farmers in Africa. The physiological responses of okra seed to variations in aluminium ions and temperature were not determined. Therefore, a study with okra, cv. Clemson Spineless, seed coated and uncoated with B. subtilis, was initiated to assess germination on moist filter paper in 90mm diameter Petri plates. Germination medium consisted of various concentrations of aluminium chloride (AlCl3), 0M, 0.001M, 0.01M, 0.05M and 0.1M. Each aluminium treatment was allocated into incubators adjusted to 22°C, 25°C and 37°C temperatures. This resulted into a 5 x 3 x 2 factorial experiment with five replicates and was conducted in three cycles. Daily scores of germinated seeds were assessed from the second to the fifth day after initiation of germination. During termination, five days after the initiation of the experiment 10 seeds with the longest coleoptiles had their coleoptiles measured using a digital caliper. At the fifth day after initiation of the experiment, coleoptile lengths from 10 seeds per treatment were measured using digital caliper. A total of 50 plates (10 from 37°C in Cycle 1; 30 from 22°C, 25°C and 37°C from Cycle 2; 10 from 37°C in Cycle 3), were selected and germinated were ground and stored at - 20°C before 1H NMR analysis. Metabolites were extracted from 50mg ground seed material with 750 μL methanol-D4 and 750 μL buffer (deuterium oxide + potassium dihydrogen phosphate). The mixture was vortexed for three minutes, sonicated for 20 minutes, centrifuged at 18000 rpms for 20 minutes and the supernatant filtered through cotton wool. Then the supernatant was dispensed into NMR tubes for further 1H NMR spectroscopic processing using a 600 MHz NMR xiii Varian spectrometer to generate magnetic spectra of the fifty samples. Results of this study demonstrated that in all the experimental cycles, regardless of aluminium concentration and bacterial seed coating, 37°C inhibited germination percentages and coleoptile lengths in okra seed germination. Germination percentages and coleoptile lengths of bacteria-coated seeds growing in 25°C were most stimulated at all aluminium concentrations, but not at 0.1M. In this temperature germination percentages and coleoptile lengths were highly influenced by the interaction of aluminium concentrations and bacterial coating, respectively. 1H NMR metabolomic association showed no distinct grouping, but clusters across treatments showed to be linked through a subset of metabolites amongst aluminium concentrations, bacterial seed coating and temperatures, respectively. This infers that treatment variations in both seed and bacterial physiological responses were associated through shared metabolic pathways. In conclusion, the study proved that 25°C provide temperature environment within which B. subtilis can be able to stimulate growth and remediate physiological constraints from aluminium ions during okra seed germination. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The of more than an embryo per seed, known as polyembryony, and the asexual reproduction via seed, known as apomixis, are usually associated. The records and importance of these events have increased in the last decades both for the Angiosperms as a whole and for specific biomes, as the Cerrado, where sexual reproduction is predominant. Despite these records, information on the ecology of polyembryonic seeds is still lacking. In this scenario, we aimed to confirm polyembryony as an indicator of apomixes in woody species of Cerrado and, based on studies of embryo resource allocation, seed germination, emergency and seedling growth, try to define the advantages and disadvantages of polyembryony for the ecology of these species. Out of a 132 species sample, 30.30% presented polyembryony, although only 6.82% did have the percentage of polyembryonic seeds above 5% and were more readily associated with apomixes. Among the Melastomataceae, a characteristic Neotropical family very well represented in the Cerrado, 33.96% of the species presented polyembryony, which predominated in the tribe Miconieae. Both in the Cerrado as a whole and in the Melastomataceae in particular, the polyembryony was associated with apomixes, but in the later, the apomixes was less often associated to higher frequencies of polyembryony. More specific studies with species of Eriotheca (Malvaceae-Bombacoideae) showed mosaics of monoembryonic and polyembryonic populations in E. gracilipes and E. pubescens, with ecological differences between either types of population. Polyembryony did not affected markedly seed germinability and seedling emergence, but resulted in less homogeneous processes than the one found in monoembryonic seeds. Resource allocation studies showed that both embryo and seedling mass decreased with the number of embryos or seedling per seed. These differences reduced the survival ability of seedlings emerging from polyembryonic seeds but, on the other hand, increased the survival chances of at least one of the seedlings from these seeds (seed individual survival). In Handroanthus chrysotrichus (Bignoniaceae), some of the putative advantages of polyembryony, as allee effect and bet hedging could be experimentally evaluated. Polyembryony was clearly correlated with the occurrence of apomixis and the results presented here showed that both processes can be important factors for the persistence and distribution of plant species in the Cerrado Biome. / A ocorrência de mais de um embrião por semente, conhecida como poliembrionia, e a reprodução assexuada via semente, conhecida como apomixia, são processos comumente associados. Os registros e a importância destes eventos vêm aumentando nas últimas décadas, tanto entre as Angiospermas como um todo quanto em biomas como o Cerrado, reconhecido como um bioma onde a reprodução sexuada é predominante. Apesar destes registros, existem ainda poucas informações sobre a ecologia das sementes poliembriônicas. Nesse cenário, objetivou-se confirmar a poliembrionia como indicador de apomixia em espécies arbóreas e arbustivas de Cerrado e, a partir de estudos alocação de recursos entre embriões, de germinação de sementes, emergência e crescimento de plântulas, tentar definir quais são as vantagens e desvantagens da poliembrionia para a ecologia das espécies. De um total de 132 espécies amostradas, 30,30% apresentaram poliembrionia, embora somente 6,82% apresentem porcentagens de sementes poliembriônicas acima de 5% e sejam mais diretamente associadas a presença de apomixia. Entre as melastomatáceas, uma família característica dos Neotrópicos e muito bem representada no Cerrado, 33,96% das espécies apresentam poliembrionia, com predominância em espécies da tribo Miconieae. Nos dois grupos amostrados, a poliembrionia foi associada à espécies apomíticas, poliplóides e com amplo padrão de distribuição, mas entre as Melastomataceae, a apomixia nem sempre estava associada a freqüências altas de poliembrionia. Estudos mais específicos com espécies de Eriotheca (Malvaceae-Bombacoideae) mostraram a ocorrência de mosaicos de populações monoembriônicas e poliembriônicas em E. gracilipes e E. pubescens, com diferenças na ecologia dos diferentes tipos de populações. A poliembrionia afetou pouco a germinabilidade e emergência das sementes, mas produziu um processo menos homogêneo que aquele das sementes monoembriônicas. Os estudos de alocação mostraram que a massa dos embriões diminuiu com o número de embriões por semente, fator que se repetiu com a massa individual de cada plântula. Estas diferenças de alocação reduziram a capacidade de sobrevivência das plântulas de sementes poliembriônicas, mas de uma maneira geral, aumentaram as possibilidades de sobrevivência de alguma das plântulas destas sementes. Em Handroanthus chrysotrichus (Bignoniaceae) algumas das vantagens da poliembrionia como a ocorrência de allee effect e bet hedging puderam ser avaliadas experimentalmente. A poliembrionia foi fortemente correlacionada com a presença de apomixia e os resultados mostram que a presença de poliembrionia e apomixia podem ser fatores importantes para a persistência e distribuição de espécies no Bioma Cerrado. / Doutor em Ecologia e Conservação de Recursos Naturais