Aspectos fisiológicos e bioquímicos da resistência do algodoeiro à ramulose mediada pelo silício

• Autor(a) principal: Guerra, Antonia Mirian Nogueira de Moura
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1170
• topic: Enzimologia; Nutrição mineral; Capacidade fotossintética; Enzymology: Mineral nutrition; Photosynthetic capacity; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA::FISIOLOGIA DE PLANTAS CULTIVADAS

One of the most important roles of silicon (Si) is the increased resistance of plants to attack by pathogens. However, despite many studies showing an active role of this element in plant resistance to diseases, nothing is known about the multiple defense mechanisms modulated by this element in the pathosystem cotton-Colletotrichum gossypii var. cephalosporioides. Thus, the objective of this study was to evaluate the effect of Si in reducing symptoms of ramulosis as well as investigate the physiological and biochemical aspects of resistance mediated by this element. In addition, to investigate how Si affects the photosynthetic capacity and antioxidant metabolism in cotton. Cotton plants of BRS Araçá and Fiber Max 993 (FM 993) were grown in pots with nutrient solution containing (+Si) or not (-Si) silicon. The application of Si reduced the rate ramulosis. The increase in the concentration of phenolic compounds and derivatives of lignin-thioglycolic acid in plants of two cultivars supplied with Si, and the increased activity of defense enzymes peroxidase (POX), polyphenol oxidase (PPO), chitinase (CHI), glucanases (GLU) in plants of BRS Araçá and POX enzymes and phenylalanine ammonia-lyase (FAL) in plants of FM 993, potentiated the chemical mechanisms of defense to the pathogen, as reported in the literature. Infection with C. gossypii var. cephalosporioides changed the photosynthetic capacity of cotton plants of two cultivars. The supply of Si on cotton plants increased the total dry matter of cotton plants, due to increases in the rate of net carbon assimilation, stomatal conductance and higher CO2 fixation. The increased activity of the enzyme superoxide dismutase (SOD) in plants of two cultivars supplied with Si increased the activity of catalase (CAT) and ascorbate peroxidase (APX), which reduced the concentrations of hydrogen peroxide (H2O2) and malonic aldehyde (MDA), which reduced the lipid peroxidation. The results support the hypothesis that the supply of Si can interact with many components of the physiological system of cotton plants, increasing the ramulosis resistance.