Abstract:By using bioassays, some plant growth-regulating activities of cytisine were determined. The results obtained indicated that cytisine inhibited the elongation of wheat coleoptile segments but increased the fresh weight of isolated cucumber cotyledons cultured in the dark (26 ℃). Cytisine obviously promoted both the root formation and the root growth of isolated cucumber cotyledons cultured in the dark (25 ℃). Furthermore the IAA oxidase activity in isolated cucumber cotyledons cultured in the dark was markdely stimulated by cytisine. These phenomena showed that cytisine had distinct plant growth-regulating activities.