Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings III. Gibberellin specificity in its enhancing effect on IAA-induced elongation

Pretreatment effects of different gibberellins, helminthosporicacid, cyclic AMP and Kinetin on subsequent IAA-induced elongationwere tested in cucumber hypocotyl sections. Gibberellin A₇ wasmore active than GA₃, while gibberellin A₃ was almost inactive.Both helminthosporic acid and cyclic AMP mimicked GA₃-action,though the degree of their activity was less. Kinetin pretreatmentresulted in marked inhibition of IAA-induced elongation. Thepretreatment effect of GA₃ was also reflected in a greater responceof the sections to synthetic auxins. (Received October 6, 1973; )