Impactos ecofisiológicos e metabólicos da alteração nos níveis de giberelina em tomate

• Autor(a) principal: Martins, Auxiliadora Oliveira
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4347
• topic: Tomate - Crescimento; Giberelina; Paclobutrazol; Metabolismo; Tomato - Growth; Gibberellin; Paclobutrazol; Metabolism; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL

This study was carried out to analyze the physiological, metabolic and anatomic impacts promoted by both the endogenous and/or artificial variation of gibberellins (GAs) on tomato plants (Solanum lycopersicum L.). To this end, different experiments were performed using wild-type (WT) and mutant plants in the biosynthesis of gibberellins (gib3, moderately deficient; gib2, mildly deficient and gib1, extremely deficient). In the first experiment I used WT and the mutant plants gib3, gib2 and gib1 and evaluated the effects of endogenous reduction of GA levels. It was observed that the reduced levels of GAs negatively affected the growth and that this slower growth is not associated with lower photosynthetic rates. The higher net photosynthesis (A N ) found in the mutants were associated with both increased stomatal density and higher stomatal (g s ) and mesophyll (g m ) conductances. One clear imbalance between carbon metabolism and growth seems to occur in plants with reduced GAs levels, given that reductions in the levels of the majority of the metabolites occurred concomitantly to higher A N . Moreover, higher A N was accompanied by elevated respiratory rate and increments in protein concentration, suggesting a shift of energy in the form of ATPs to other routes, since more energy production was not associated with higher biomass accumulation. In the second experiment I used plants WT and gib3, the genotype most similar to WT in the first experiment, and subjected those plants to artificial variations in the content of GAs by applying GAs and/or paclobutrazol (PBZ), a GA biosynthesis inhibitor. The results obtained allowed the identification of both metabolic and physiological changes associated with both endogenous GAs variation, as well as the artificial variation caused by varying the GAs regime. In both genotypes growth was strongly reduced in presence of PBZ whereas it was incremented when applying GAs. Lower growth rates were accompanied by higher dark respiration (R d ) and higher A N , the former being influenced by larger stomatal density and stomatal opening, leaf thickness, as well as g s and absorptance. The levels of the majority of metabolites evaluated were positively associated with GAs content. Little or no variation in chlorophyll fluorescence a and antioxidative system parameters indicated no apparent stress. Taken as a whole, the information obtained within this study provide a better understanding of the physiological, molecular and metabolic disorders associated with GA deficiency in plants; however, future metabolic and molecular studies are still required to allow us a better understanding of the effects of reduced GA levels on the metabolism of these plants.