Efeito do óxido nítrico na atenuação do estresse desencadeado por arsênio em Pistia stratiotes L. (Araceae).

• Autor(a) principal: Farnese, Fernanda dos Santos
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4330
• topic: Fitorremediação; Estresse oxidativo; Capacidade antioxidante; Ascorbato; Enzimas antioxidantes; Phytoremediation; Oxidative stress; Antioxidant capacity; Ascorbate; Antioxidant enzyme; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL

Nitric oxide effect on attenuating the stress triggered by arsenic (As) was evaluated in Pistia stratiotes, being the nitric oxide supplied in the form of sodium nitroprusiate (SNP). The plants were cultivated in nutrient solution, pH 6.5, ½ ion force and exposed to four treatments: control (nutrient solution) SNP (0.1 mg L-1); As (1.5 mg L-1); As + SNP (1.5 and 0.1 mg L-1, respectively). The plants remained in this condition for seven days to the analysis of growth and, As and mineral nutrients uptake and for 24 hours, to the analysis of metabolic changes. The As uptake kinetic was analyzed using six concentrations of this pollutant, in which the plants remained for two hours: 0.0, 0.25, 0.5, 0.75, 1.0 and 1.5 mg L-1. The parameters of As uptake kinetic in P. stratiotes indicate that this metalloid uptake occurs by the high affinity transporters. The absorbed As was accumulated in the vegetal tissues, mainly in the roots, which gave to P. stratiotes a low translocation factor and a status of probably hyperaccumulator, a characteristic that was not affected by SNP presence. The As accumulation triggered many damages, as the increment of reactive oxygen species (superoxide anion and hydrogen peroxide) and lipid peroxidation. These damages were reversed by SNP, which apparently acted directly as antioxidant and as a signalizing molecule, stimulating enzymatic (catalase, peroxidase and ascorbate peroxidase) and non-enzymatic (stimulating the ascorbato-glutathione cycle) antioxidant responses, which reflected in an increase in total antioxidant capacity. As a consequence, As tolerance index increased in the presence of SNP. The photosynthetic parameters were also affected, with the reduction in the chloroplastic pigments concentration in presence of As, except carotenoids that showed an increase in their concentration. The SNP presence restored pigments concentrantion to the normal levels. The maximum photochemical efficiency of PSII and the quantum yield of electron transport were also negatively affected by As, while the non-photechemical quenching (NPQ) presented significant increment. Carbon assimilation (A) decreased significantly in As presence whereas gs did not alter and the Ci/Ca rate increased, indicating biochemical limitations. The ΦFSII/ ΦCO2 rate was higher in plants exposed to As. For the mineral nutrients concentration, As exposition decreased iron, magnesium, manganese and phosphorus concentration, but did not alter calcium concentration. Of these nutrients, only phosphorus concentration did not show similar values than control when As was supplied in combination to SNP. Therefore, nitric oxide, supplied in the form of SNP, was efficient on attenuating damages triggered by As, acting as a direct antioxidant and as a signalizing molecule.