Alterações fisiológicas e avaliação do estresse oxidativo durante o desenvolvimento e a senescência de folhas se soja, Glycine max L.

• Ano de defesa: 2008
• Autor(a) principal: Garcia, Michele Pacheco
• Orientador(a): Silva, Marco Aurélio Pedron e
• Banca de defesa: Cambraia, José , Puschmann, Rolf , Kuki, Kacilda Naomi
• 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: Senescência foliar; Soja; Estresse oxidativo
• Palavras-chave em Inglês: Leaf senescence; Soybean; Oxidative stress
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL
• Link de acesso: http://locus.ufv.br/handle/123456789/4299

Physiological changes and oxidative stress were studied in soybean leaves, Glycine max, variety MG / BR 46 (Conquista) during their development. In a group of plants the reproductive organs were removed, in an attempt to extend their life cycle, retarding their leaf senescence. In the control plants the floweres were not removed and the plants followed their normal cycle until natural senescence. Control plants developed normally, exhibiting progressive degradation of chlorophylls and carotenoids (in low proportion), with the characteristic yellow color of senescent leaves. On the other hand, plants with no flower kept their leaves green until the end of the experiment. The degradation of the pigments led to a sharp decline in carbon assimilation rates (A) in control plants, in which also occurred a decrease in stomatal conductance (gs) and increase in the ratio between the internal and ambient CO2 concentration (Ci/Ca). In contrast, plants without flowers showed a minor drop in A, gs and Ci/Ca. The proportion of electrolyte leakage increased in the control plants throughout their development. Leaves of control plants showed lower levels of hydrogen peroxide (H2O2), in contrast with a great increase observed in plants with no flowers. The low activity of superoxide dismutase (SOD) in control plants in addition to the high activity of peroxidases (POX) and ascorbate peroxidase (APX) are likely responsible for the low levels of H2O2 in those plants. Conversely, the intense activity of SOD and the low performance of POX and APX in plants without flowers might have contributed to the high levels of hydrogen peroxide. Catalase (CAT) activity dropped continuously in the leaves of the two kind of plants, indicating that this enzyme does not play a fundamental role in the removal of reactive oxygen species during this senescence. In both kind of plants, the activity of glutathione reductase had initially increased, followed by a sharp decrease until the end of the experiment. The results of this experiment suggest that oxidative stress is not the determinant factor associated with leaf senescence process in soybean plants.