Respiração e atividade de enzimas do metabolismo antioxidativo em raízes de plântulas de milho (Zea mays L.) submetidas ao estresse por alumínio

• Autor(a) principal: Rocha, Marcio
• Data de Publicação: 2006
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4288
• topic: Alumínio; Estresse oxidativo; Proteína desacopladora; Aluminum; Oxidant stress; Uncoupling mitochondrial protein; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL

The effects of aluminum on growth, respiratory activities and on some enzymes related to reactive oxygen species (ROS) elimination were examined in roots of two corn seedlings cultivated in nutrient solution, by comparing a susceptible (BR 106) and a tolerant cultivar (BR 206). Growth of the main root decreased in both cultivars, mainly in the susceptible one, at aluminum concentration of 50 and 100 µM. Only in the tolerant cultivar aluminum induced a decrease in the leak of electrolytes. On the contrary, the susceptible cultivar showed significant increase in lipid peroxidation. Aluminum promoted higher activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX), only in the tolerant cultivar. No difference was observed in the activities of catalase (CAT), peroxidases (POX) and glutathione reductase (GR) in both cultivars. Ascorbate content was not altered, but the ascorbate redox state (ratio ascorbate/dehydroascorbate) increased in the tolerant cultivar. In absence of aluminum, respiratory oxygen consumption was higher in the tolerant cultivar, both in states 3 and 4. These respiratory activities were decreased by aluminum in the susceptible cultivar, but were increased in the tolerant one. ADP/O ratios were decreased by aluminum, in both cultivars at a similar extent. The cytochrome c pathway was not altered by aluminum in the tolerant cultivar, but decreased in the susceptible one. Without aluminum, the susceptible cultivar showed a higher alternative oxidase (AOX) activity than the tolerant one. Aluminum promoted a decrease in AOX activity in the susceptible cultivar, the opposite response being observed in the tolerant one. In both cultivars aluminum induced an increase above 120% in the residual oxygen consumption. Activity of the plant uncoupling mitochondrial protein (PUMP) was decreased by aluminum in the susceptible cultivar and enhanced in the tolerant one. These results suggest that the tolerant cultivar possesses a more efficient enzymatic system for ROS removal than the sensitive one. Furthermore, the partial mitochondrial uncoupling, resulting from higher AOX and PUMP activities should have contributed to the higher aluminum stress tolerance showed by cultivar BR 206.