Toxicidade de ferro e metabolismo antioxidativo em Eugenia uniflora L.

• Ano de defesa: 2011
• Autor(a) principal: Jucoski, Gládis de Oliveira
• Orientador(a): Cambraia, José
• Banca de defesa: Kuki, Kacilda Naomi , Alves, José Donizeti
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Fisiologia Vegetal
• Departamento: Controle da maturação e senescência em órgãos perecíveis; Fisiologia molecular de plantas superiores
• País: BR
• Palavras-chave em Português: Crescimento; Cinética de absorção; Teores de nutrientes; Estresse oxidativo; Toxidez de ferro
• Palavras-chave em Inglês: Growth; Absorption kinetics; Nutrient content; Oxidative stress; Toxicity of iron
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL
• Link de acesso: http://locus.ufv.br/handle/123456789/987

Iron is an essential micronutrient for growth and development of plants. In excess, however, may induce the production and accumulation of reactive oxygen species, causing oxidative stress leading to reduced growth and thus, decreasing crop productivity. The aim of this study was to evaluate the effects of iron toxicity on the absorption and accumulation, on antioxidant metabolism and growth of young plants of Eugenia uniflora L.. Forty-five days-old E. uniflora seedlings were exposed in Hoagland solution, pH 5.0 at half ionic strength, the following treatments: three levels of Fe (0.045, 1.0 and 2.0 mM), applied as FeEDTA and three exposure times (15, 30 and 45 days after Fe treatment). At the end of each treatment time, the parameters were determined: leaves number, plant height, primary root length, dry matter production of leaves, stems, and roots and chloroplastidic pigments, P, Fe, Zn, Cu and Mg contents. Additionally, it was determined the kinetic parameters of iron absorption after application of the treatments above mentioned. In addition, the MDA levels, activity of antioxidant enzymes (SOD, CAT, POX, APX, GPX and GR) and AA, DHA, GSH, GSSG and AA/DHA contents and GSH/GSSG ratio in the leaves and roots were determined. The treatment of plants with toxic levels of Fe resulted in a decrease in the primary root length, the dry matter production of the three parts of the plant and pigment contents and typical visual symptoms of Fe toxicity were observed. Iron in excess also caused a shift in biomass partitioning of the dry matter, with relative increase of the leaves in relation to other parts of the plant and reduced Zn, Cu and Mn contents, while P content remained essentially unchanged at the different parts of the plant. The treatment of plants with toxic levels of Fe changed the activity of the transport system, increasing the kinetic constants of Fe absorption (Vmax and Km), resulting in increased iron absorption by plant, resulting in the toxic effects exhibited on plant growth. In addition, the increased levels of iron in the nutrient solution resulted in higher intensity of lipid peroxidation, mainly leaves. The activities of the antioxidant enzymes SOD and GR increased with the levels of Fe in the solution and with the time of exposure to the treatments. CAT, POX and APX activities enhanced with plant treatment with high Fe concentration, but decreased with the time of exposure to treatments. The GPX activity reduced with increasing Fe concentration and exposure time. Generally, AA and GSH contents and the AA / DHA and GSH / GSSG ratios increased with Fe concentration and time of exposure to treatments. The results show that E. uniflora seedlings under toxic levels of Fe undergo oxidative stress, which is mitigated both by changes in the activities of antioxidative enzymes and by changes in levels of some antioxidant metabolites such as AA and GSH.