Toxidade do arsênio e papel do óxido nítrico na atenuação dos danos causados em Spirodela intermedia W. Koch (Lemnaceae)

• Ano de defesa: 2013
• Autor(a) principal: Silva, Cristiane Jovelina da
• Orientador(a): Oliveira, Juraci Alves de
• Banca de defesa: Silva, Luzimar Campos da
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Fisiologia Vegetal
• Departamento: Controle da maturação e senescência em órgãos perecíveis; Fisiologia molecular de plantas superiores
• País: BR
• Palavras-chave em Português: Enzimas antioxidantes; Espécies reativas de oxigênio; Óxido nítrico; Alterações micromorfológicas; Fluorescência em raiz
• Palavras-chave em Inglês: Antioxidant enzymes; Reactive oxygen species; Nitric oxide; Micromorphological changes; Fluorescence in root
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL
• Link de acesso: http://locus.ufv.br/handle/123456789/4339

The toxicity of arsenic (As) and its effects on antioxidant system were analyzed in S. intermedia. Plants treated in nutrient solution, pH 6.5, were exposed to increasing concentrations of As over a period of 24 hours. The objectives of this study were to evaluate the effects of toxic levels of As on production of reactive oxygen species (ROS), the antioxidative system and root external morphology. The increasing concentration of As was accompanied by higher production of reactive oxygen species and lipid peroxidation. There was a linear augmentation in the amount of superoxide anion and an increase in amount of hydrogen peroxide up to a concentration of 1.0 mg L-1 As. Augmentation in the amount of anthocyanins and higher activity of the enzymes superoxide dismutase (SOD), peroxidase ( POX), ascorbato peroxidase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR) was also observed. In contrast, there was a slight decay in catalase activity. Despite the reduction in the concentration of hydrogen peroxide in higher concentrations of As, the activity of antioxidant enzymes was not enough to buffer the damage, since the concentration of superoxide anion and MDA increased linearly with the increase of As. In a second experiment, nitric oxide (NO) was supplied as sodium nitroprusside (SNP). Plants treated in nutrient solution, pH 6.5, ½ ion force, were subjected to four conditions: control (nutrient solution); SNP (15 mg L-1); As (2.0 mg L-1); As + SNP (2.0 and 15 mg L-1, respectively) over a period of 24 hours. It was evaluated the influence of nitric oxide (NO) on membrane damage and activity of antioxidant enzymes and NO production enzyme. In situ fluorescence detection was used to reveal NO presence. There was an increase in MDA content, membrane leakage, activity of antioxidative enzymes and nitrate reductase comparing 2.0 mg L-1 As conditions with As + SNP treatment. Therefore, it is considered that the protective effect of the application of SNP appears reflects direct reaction of NO with ROS. The plants under arsenic stress showed higher NO production, confirmed by the increase in nitrate reductase activity and augmentation in fluorescence levels. When provided exogenously, NO also acted directly in the removal of toxic metabolites generated in response to As. Therefore, it was found that NO, supplied by SNP, buffers As toxicity in S. intermedia.