Long-day photoperiods and applications of gibberellic acid promoted shoot growth by stimulating leaf enlargement as a result of increasing avaliable photosynthates, which was also reflected in the higher leaf, stem and nodule plant dry weights. Short-day plants had more nodules, but they were smaller (by weight) than those of long-day plants. Gibberellic acid at 1.5×10−6 M enhanced nodule growth without preventing nodule formation. Factors other than just gibberellic acid are concluded to be involved in the responses of nodulation and nitrogen fixation to day length.Facultad de Ciencias Agrarias y Forestales