Endogenous ethylene does not initiate but may modify geobending–A role for ethylene in autotropism

Abstract. Ethylene production during geostimulation was examined in peduncles of dandelion ( Taraxacum officinale ). Significant amounts of ethylene were evolved from geostimulated peduncles compared with vertical controls only after geostimulation of 2 h or longer and the extra ethylene arose mainly from the lower portion of geostimulated peduncles. Reduction of the ethylene produced from geostimulated peduncles by pretreatment with ethylene-synthesis inhibitors did not affect or enhanced subsequent geobending. It is proposed that ethylene may control the later stages of geobending and influence the straightening process of autotropism.