Cin?tica de absor??o de nitrato e am?nio e produ??o de gr?os e ?leo de girassol em diferentes n?veis de nitrog?nio e boro

• Autor(a) principal: Alves, Luiziene Soares
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/3053
• topic: Helianthus annuus L.; Oleaginosa; Valores de Km e Vm?x; Oilseed; Km and Vm?x values; Agronomia

The sunflower (Helianthus annuus L.) is an economically important oilseed due to the high-quality oil produced both for food industry and biofuels. In face of increasing demands for renewable energy, knowledge about improvement of sunflower oil production is increasingly necessary to make it sustainable. Among the factors for oil production, nitrogen fertilization could be a limiting factor on the growth, metabolism, and production rate of sunflower. Also the application of boron that is a micronutrient with relevant roles for development and grain output. This work aims to evaluate how nitrogen and boron supplies influence oil and grain output, and to analyze the nitrate and ammonium uptake in sunflower. For this study, two experiments were developed. The first one was done with Neon genotype on nutrient solution, to analyze uptake kinetic parameters in high and low nitrate and ammonium supply. The second one was in greenhouse conditions for oil and grain output analysis with different doses of nitrogen and boron, to investigate the effect of this variation on Neon and BRS321 genotypes. Samples from the first experiment, which were cultivated on N-NH4+ solution, presented high Vm?x and low root volume in comparison with N-NO3- supplied ones. This is due to N-NH4+ being assimilated immediately in the cytosol of roots cells, and the presence of more moving sites for this ion on its roots. Despite this result it presents low Vm?x values, the plants supplied with 2.0 mM of N-NO3- showed higher biomass than N-NH4+, and that might indicate an greater potential use of N. When cultivated with 0.2 mM of N-NO3- or N-NH4+, the plants showed no preference for N source. Through the analysis of N-NO3- concentration, the petiole was pointed as the main plant part for N-NO3- accumulation. The second experiment showed that both genotypes were responsive for the boron fertilization. The combination of higher boron and nitrogen fertilization was beneficial to oil and grain output for the BRS321 genotype. For the Neon genotype, the treatment with boron + 10 kg de N.ha-1 showed a production of filled grain equivalent to the treatment without boron + 50 kg de N.ha-1. This result demonstrates a positive effect of the boron application for grain output and in saving nitrogen fertilizer for this genotype. Furthermore, the analysis of N levels, in both genotypes indicated that the limbo can be a sensitive parameter for evaluating plant N status.