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Universidade Estadual de Campinas (2007)

Alterações no metabolismo de compostos nitrogenados em Calopogonium mucunoides em resposta a diferentes fontes de nitrogênio : efeitos na nodulação e na fixação

Santos de Camargos Liliane

Titre : Alterações no metabolismo de compostos nitrogenados em Calopogonium mucunoides em resposta a diferentes fontes de nitrogênio : efeitos na nodulação e na fixação

Alterations in the metabolism of nitrogenous compounds in Calopogonium mucunoides in response to different nitrogen sources : effects on nodulation and fixation

Auteur : Santos de Camargos Liliane

Université de soutenance : Universidade Estadual de Campinas

Grade : Doutor em Biologia Vegetal 2007

Résumé
Calopogonium mucunoides is a tropical legume found in the ?cerrado ? (savanna) regions, and widely used as green manure and forage. It has a high capacity for fixing nitrogen, being cultivated in soils with low pH and poor fertility ; and good resistance to drought, but does not tolerate low temperatures. Studies on the nitrogen metabolism of this species are quite scarce but it is known that the legume has a high relative abundance of ureides when fixing nitrogen. Our own preliminary studies suggested certain tolerance of fixation to the presence of nitrate. The objective of the present study was to study nitrogen metabolism in Calopogonium mucunoides, identifying the influence of the nitrogen source on nitrogen metabolism using : different nitrogen sources starting before nodulation ; and exposing plants to the same sources only after complete nodulation, at different concentrations and times of exposure. It was found that the nodulation process of this species was not sensitive to the presence of a nitrogen source in the medium and, when fully nodulated plants were exposed to the nitrogen sources, fixation was maintained and the activity of nitrogenase was only affected, albeit partially, when exposed to the highest (30 mM) dose of nitrate. On the other hand, the species appears to respond to the exogenous source of nitrogen by translocating and/or accumulating different forms of ureides (allantoin and allantoic acid), but the metabolism of amino acids did not respond clearly to the nitrogen source. The data indicate that the process of nodulation and nitrogen fixation in this species is tolerant to the presence of a nitrogen source in the medium and should prove useful for future studies on the sensitivity/tolerance of nitrogen fixation to na external nitrogen source in legumes

Mots clés  : Nitrato ; Nitrogenio - Fixação ; Aminoacidos ; Ureideos — Nitrate ; Nitrogen fixation ; Ureides ; Amino acids

Présentation

Page publiée le 29 novembre 2015, mise à jour le 10 juillet 2017