Abstract:This paper studied the effect of ethylene on adventitious root initiation ofstem cuttings with the experiment materials of shoot, semi-hardwood and one-year-old hardwood of I-69 Poplar. Auxins treatments could induce the cuttingsto release ethylene, and the amount of ethylene released from cuttings tre-ated with auxins was higher than that from cuttings without auxins treatment(CK) during the whole process of cutting and rooting, meanwhile the ethylenestimulated the initiation of adventitious root. But the amount of ethylene rele-ased from cuttings treated with GA3 ABA, and KT was egual to that from CKtreatment, which did not stimulate, even inhibited or intensely inhibited theadventitious root initiation. The treatment with ethylene gas at a concentrationof 25-1000ug·ml-1 could stimulate the adventitious root initiation and buddingof I-69 Poplar hardwood cuttings. The initiation of adventitious roots could bepromoted in treatment with ethrel at a low concentration(<25ug·ml(-1)), whichcould be reduced and inhibited as the concentration of ethrel increased Theamount of ethylene released from cuttings increased magnificently when cuttingstreated with a high concentration of ethrel. The morphological changes ofcuttings treated with high concentrations of ethrel, ABA, and NAA were si-milar. In all of experimental results, the effect of ethylene on the initiationof adventitious roots of I-69 Poplar cuttings is similar to that of auxins, whichis stimulated at low concentration and inhibited at high concentration. Theseeffects on adventitious root initiation are related to the production of ethylenedirectly as a result of their cooperation.