Atenuação, pela associação micorrizica arbuscular, do estresse causado por cadmio em plantas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Cd accumulation by plants and the increasing presence of this metal in the soil system is nowadays of great environmental concern. Cd contamination can bring human health problems and harmful effects to the soil ecossystem. Arbuscular mycorrhiza (AM) is considered a universal symbiosis between higher plants and fungi from the order Glomales. This symbiosis is a direct link between soil and plant roots, with a direct influence in nutrient and potentially toxic elements uptake. In this context, the present research studied the influence of the arbuscular mycorrhizal association in potencial remediator plants of contaminated soil, jackbean, maize and sunflower, on Cd uptake and accumulation patterns and evaluated the possible alleviation of the stress caused by excess Cd confered to the host plants. With this intention, plant growth parameters and Cd distribution in shoots, roots and in the extraradical mycelia of the arbuscular mycorrhizal fungi (AMF) inoculated were evaluated. Guaiacol peroxidase activity in plant roots, as one of the key enzymes of the antioxidant system in plants, nutrient uptake and phosphatase activity in leaves were used to evaluatethe stress caused by Cd and the possible phytotoxicity alleviation in plants due to mycorrhiza. In a general way, plants benefited from the AM association, both in the ausence and in the presence of Cd. However, plant response in terms of Cd accumulation differed. Jackbean plants associated to G. etunicatum and sunflower plants colonized by G. intraradices absorved higher amounts of Cd than non-mycorrhizal (NM) plants. Sunflower plants colonized by G. intraradices showed a shoot Cd concentration higher than 200 mg kg-1 and can be considered a Cd hyperaccumulator plant. In addition, sunflower plants absorved and translocated still higher Cd amounts when in association with G. intraradices. Maize mycorrhization promoted plant growth, ameliorated mineral nutrition and attenuated plant stress in excess Cd conditions. Guaiacol peroxidase activity showed to be a sensitive biomarker of the oxidative stress caused by Cd in plant roots. The enzime was induced in the presence of the metal and influenced by plant mycorrhal status

ASSUNTO(S)

fungos micorrizicos cadmio metais pesados

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