The inhibitory effects of 200 t-tM aminooxyacetic acid (AOA), cobalt sulfate (CoSO,) and norbornadiene (1000 /11'1-1 ) on the AgN0 3 -induced developmental alterations in Gynura aurantiaca DC plants are evaluated. AOA and CoSO, dramatically repress ethylene production. Norbornadiene does not affect ethylene synthesis. At the same time the development of leaf malformations and the accumulation of the low molecular weight polypeptides (P, and P,) associated with AgN0 3-treatment are also repressed. The impairment of AgNOrinduced alterations by AOA results from inhibition of ACC synthase activity. 1-aminocyclopropane-1-carboxylic acid (ACC) accumulated in the leaves pretreated with CoSO,. This strongly suggests that the developmental distortions caused by AgN0 3 in Gynura aurantiaca DC plants are mediated by ethylene.