Arsênio em plantas aquáticas: absorção, toxicidade, nutrição e metabolismo da glutationa / Arsenic in aquatic plants: absorption, toxicity, nutrition and glutathione metabolism

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

22/10/2010

RESUMO

Arsenic (As) toxicity and its effects on glutathione metabolism were analyzed in two vegetal specimens: Lemna gibba and Salvinia minima. Plants were cultivated in nutrient solution, pH 6.5, and exposed to arsenic concentrations of 0.0 and 1.0 mg L-1, for three days. Both species accumulated As in their tissues when exposed to this element, being this accumulation eleven times higher in L. gibba than in S. minima. The relative growth rate reduction of L. gibba and S. minima was about 25.24 % and 38.79 %, respectively. Differently from the superoxide anion content that hasnt showed significant variations, the hydroxide peroxide content increased in both aquatic macrophytes. In L. gibba, there werent changes on MDA content, while in S. minima, an increment of it around 85 % has occurred. In both species studied, chloroplastic pigments showed reduction in their content, except for carotenoids content in L. gibba which didnt show any variation. Although As exposure to plants hasnt changed iron and manganese content, a decrement of calcium and magnesium content has occurred. Both L. gibba and S. minima showed a decrement in phosphate absorption as well as on phosphorus content after As exposure. L. gibba showed an increment on sulphate absorption and on plant sulfur content which havent been observed in S. minima. The reduction on glutathione content was observed when both plants were exposed to As. All the glutathione metabolism enzymes that were analyzed (ATP sulphurylase, γ- glutamylcysteine sintetases, glutathione peroxidase, glutathione sulphotranspherase and glutathione reductase) showed an increment on their activities in L. gibba exposed to As while in S. minima there was an increment only in glutathione reductase activity. Based on As content absorbed by the plants, the stress induced by As in L. gibba should be eleven times higher than in S. minima. However, S. minima, besides showing higher content of reactive oxygen species, it showed toxicity symptoms more intensively than in L. gibba after As exposure. So, L. gibba, a possible As hyperaccumulator, seems to have a defense system more efficient to mitigate the stress induced by this metalloid, which involves the participation of substances and enzymes of the antioxidative and glutathione metabolism.

ASSUNTO(S)

lemna gibba fisiologia vegetal salvinia minima fitorremediação estresse oxidativo lemna gibba salvinia minima phytoremediation oxidative stress

ACESSO AO ARTIGO

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