Activity analiysis of some antioxidant enzymes in soybean plants (Glycine max L. Merr.) under levels of manganese, in function of arbuscular mycorrhizae. / Análise da atividade de algumas enzimas antioxidantes em plantas de soja (Glycine max L. Merr.) sob níveis de manganês, em função da micorriza arbuscular.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Brazilian soils are predominantly acid, which is considered a common incident in tropical regions. Soil acidity in combination with biotic and non-biotic factors can result manganese toxicity in plants, limiting their development. The use of conventional agricultural practices promotes an increase in Mn toxicity, as it reduces the soil content of organic matter. This problem can be minimized by the use of some tilling practicies like liming and breeding, which are widely used. However, crop management alternatives through the use of mycorrhizae to induce greater Mn tolerance in plants under high levels of Mn seem to be promising. In this work, plant growth, the absorption, distibution of Mn, Fe, P, Ca and activity of catalase, peroxidase, superoxide dismutase and indolacetic acid oxidase were evaluated in leaves and roots of plants inoculated with mycorrhizal fungi and non-inoculated ones, to invetigate a possible resistance induction mechanism and nutrient interactions in control of toxic levels of Mn. A greenhouse experiment was conducted with soybean plant (Glycine max L. Merr. CV. IAC 8-2) in a completely randomized factorial design 4x5: inoculation of two different arbuscular mycorrhizal fungi (AMF): Glomus etunicatum and Glomus macrocarpum, which received 30 mg kg –1 of P, and two non-inoculated controls, one that received 30 mg kg –1 and the other with 50 mg kg –1 of P; 5 levels of Mn (0, 5, 10, 20, 40 mg kg -1 ). There were two harvest periods, 45 and 90 days. The enzymatic activities were evaluated in non-denaturing polyacrilamyde gel eletrophoresis (PAGE). Manganese levels between 10 and 40 mg kg -1 in the substrate can induce Mn toxicity in soybean plants, that results in a growth reduction and in alterations in the nuttrient absorption alterations of the plants. The increase of P and the presence of mycorrhizae result in the alleviation of Mn toxicity in soybean plants. Micorrhizal plants present lower Mn concentration and generally less enzymatic activity of indolacetic acid oxidase and peroxidase than control plants. Although both, peroxidase and superoxide dismutase are antioxidant enzymes, they present differentiated electrophoretic standards. Most of the time peroxidase and indolacetic acid oxidase activities increase due to increasing Mn levels. Superoxide dismutase activity, however, is higher in the shoots of micorrhizal plants when compared to control plants.

ASSUNTO(S)

soybean mycorrhiza manganese soja toxicidade do solo enzymes manganês soil toxicity micorriza enzimas

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