INFLUENCE OF SILICON PRETREATMENT ON ALUMINUM TOXICITY IN MAIZE ROOTS

The influence of Si pretreatment on Al toxicity in an Al sensitive mai ze variety (Zea mays L. var. BR 201 F) was investigated using root elo ngation rates (RER) and hematoxylin staining as stress indicators. Pla nts pretreated with 1 mM Si (+ Si) and then exposed for 24 h to Al in nutrient solution without concurrent Si supply in the rooting medium e xhibited higher RER than plants that were not pretreated with Si (-Si) . The ameliorative effect of Si was due to lower Al uptake and to the exclusion of Al from the root tips in + Si plants. Lower Al uptake in + Si plants was not a consequence of decreased Al availability in the bulk solution. The possible mechanisms of Si-induced increase of Al re sistance are discussed.