Abstract: Stem primodia of Eucommia ulmoides Oliv. seedlings were treated with different concentrations of colchicine solution at different stages in order to figure out the best inducing method and obtain tetraploids of Eucommia ulmoides. The results showed that, apart from 0.05% colchicine solution for 48 h, the additional treatments (0.1%, 0.2% or 0.4%) were suitable for 12 h, in which the rates of mutants with morphological characteristics varied from 43.3% to 63.3%, the optimum treatment combination was 0.1% colchicine solution for 12 h, and the rates of vatiant plants and tetraploid plants were 63.3% and 36.7%, respectively. The results of chromosome counts indicated that, of the 148 variant plants, 47 plants were tetraploid plants (2n=4x=68), taking up about31.76%. This result was consistent with that analyzed with the 'Flow Cytometry' method. The plants showed the general characteristics of tetraploids, such as, thicker leaf, smaller leaf index , larger guard cells, less stomata per unit area and more chloroplasts in guard cells.

Key words: Eucommia ulmoides Oliv., polyploid induction, chromosome identification, colchicine