Aspectos bioquímicos em plantas de cafeeiro tratadas com silício / Biochemical features in coffee plants treated with silicon

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Most plants can defend themselves against fungal infections by natural means, which can be induced by a number of biotic and abiotic elicitors. Soluble silicon (Si) has been shown to induce resistance in a number of plant species against several pathogens. The objective of this work was to assess the influence of silicon application of symptoms caused by the biotrophic fungus Hemileia vastatrix in susceptible coffee plants and evaluate the biochemistry process involved in defense mechanism. First of all, were studied two Si sources (Ca/Mg silicate and potassium silicate) in five doses to standardize dose/source for the future experiments. The statistical analysis showed that no difference was observed in relation to plant height, leaf area and number of leaves. However, the number of lesions reduced 60% in the higher silicon dose when compared to the number of lesions in control plants. Infected plants were found to have a linear decrease of lesions with the increase of silicate concentration. The lowest number of lesions per leaf area was observed in plants that received 5 M of Si from potassium silicate. This result indicates the use of silicon as an alternative for an ecological management system for coffee disease protection. The second step of this work was to evaluate the biochemistry process involved in resistance induced by Si in susceptible coffee plants. The activity of the enzymes related to oxidative stress (peroxidases, catalase, and superoxide desmutase) and related to defense (glucanase, chitinase, PAL) was evaluated. The leaves were collected in different time intervals after the fungus inoculation (24, 48, 72 e 96 hours after the fungus inoculation) in order to obtain the protein extract. It was possible to observe that the activity of CAT, SOD and APX was higher in Si-treated coffee plants suggesting that Si could stimulate a faster response to oxidative stress. The same situation occurred to the defense related enzymes. By the results obtained here it is possible to verify that Si can stimulate a faster defense response in susceptible coffee plants when inoculated with coffee leaf rust fungus

ASSUNTO(S)

leaf rust silício coffee plants cafeeiro silicon ferrugem

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