Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings II. Effect of GA3-pretreatment on IAA-induced elongation

摘要

IAA-induced growth of light-grown cucumber hypocotyl sections is markedly enhanced by GA3-pretreatment of the sections; there is a distinct synergism between IAA and GA3. Water pretreatment also enhances IAA-induced growth. On the other hand, IAA-pretreated sections showed practically no further growth in response to post treatment with GA3. The enhancing effect of GA3is obtained with only 30 min pretreatment, the maximum effect occuring with 2 hr pretreatment. Pretreatment longer than 8 hr is less effective. This enhancing effect of GA3can be observed soon after post treatment with IAA. The response of GA3-pretreated sections to IAA is greater in pretreatment with higher concentrations of GA3, and higher degrees of synergism between IAA and GA3are obtained at IAA concentrations less than 10-4M. This synergistic interaction between GA3and IAA is more marked in aged hypocotyl sections than in young sections. From these results we concluded that gibberellin sensitizes hypocotyl cells to the subsequent effect of auxin on cell elongation.