Crescimento e respostas antioxidantes de macrófitas aquáticas submetidas ao arsênio / Growth and antioxidative responses of aquatic macrophytes to arsenic

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The influence of different concentrations of As over some aspects of growth and antioxidant system were studied in three water species: Azolla caroliniana, Lemna gibba and Salvinia minima, in nutrient solution. After the three species being exposed to five concentrations of As (0.0, 0.25, 0.5, 1.0 and 1.5 mg.L-1) in nutrient solution, the As content into the plants, relative growth rate (TCR), superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutatione reductase (GR) enzymatic activity, total thiol, non protein thiol and protein thiol content and anthocyanin content were determined. L. gibba showed the highest tolerance to As, requiring 967,6 μg g-1MD to reduce growth in 50%. A. caroliniana required 429,2 μg g-1MD to show this level of growth reduction and S. minima required 255,08 μg g-1MD for the same response. Antioxidant mechanisms to the increase in As concentration in the medium characterized each species. A. caroliniana went through increases in CAT and GR activities, keeping unaltered SOD and POX activities, and showing reduction in APX activity, although it presented the highest activity of this enzyme. S. minima exhibited increase in SOD, CAT, APX and GR activities, keeping POX activity unaltered, with the increase of As concentration in the growth medium. L. gibba higher tolerance to As effects seem to be related to the enzymatic antioxidant mechanisms and also to the non-enzymatic ones. This species, besides presenting higher SOD, CAT, POX and GR activities, also showed higher thiol and anthocyanin content than the other two species studied. Although A. caroliniana and S. minima also presented increase in the activity of several enzymes, L. gibbas higher tolerance seems to be due not only to the increase in these antioxidant processes, but also to superior basal activity of these enzymes, and to higher thiol and anthocyanin basal content. Besides the increase in enzymatic activities, L. gibba exhibited total-thiol and non-protein thiol content increase, diminishing protein thiol content. A. caroliniana and S. minima practically did not suffer alterations in thiol content. As L. gibba, A. caroliniana and S. minima revealed an increment in anthocyanin content after exposure to increasing concentrations of As in the solution. In this context, L. gibba showed the highest potential to be employed in phytoremediation.

ASSUNTO(S)

azolla salvinia azolla fitorremediação fisiologia vegetal phytoremediation salvinia lemna lemna

ACESSO AO ARTIGO

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