EFFECTS OF AZOSPIRILLUM SPP ON ENDOGENOUS GIBBERELLIN CONTENT AND GROWTH OF MAIZE (ZEA-MAYS L) TREATED WITH UNICONAZOLE

The growth of Zea mays L. plants was reduced by treatment with unicona zole, supplied 7 d prior to Gibberellin A(3) (GA(3)) application or Az ospirillum spp. inoculation. The effect of uniconazole was more remark able in the aereal part than in the roots. Both A. lipoferum and A. br asilense increased height at similar levels with respect to applicatio n of 0.1 mu g/plant of GA(3). Also, the stimulating effect on growth o f the root system was expressed as an increase in fresh weight. This w as correlated positively with the occurrence of Azospirillum spp, obse rved in roots and stems of maize plants. Gibberellin A(3) was characte rized by capillary gas chromatography-selected ion monitoring in a fre e acid fraction:from roots on the plants inoculated with Azospirillum spp. In the roots of the non-inoculated uniconazole-treated plants, GA (3) was not found. We conclude that production of GA(3) by Azospirillu m spp. was involved in growth promotion of maize.