Abstract: In vitro tetraploid induction of ‘Dongzao’ ( Ziziphus jujuba Mill. ) and sour jujube ( Z.acidojujuba C. Y. Cheng et. M. J. Liu) was studied by treating cluster budswith colchicines supp lemented in medium. The results indicated that the highest induction rates of sour jujube and ‘Dongzao ’were 36.67% and 26.67% , respectively, under optimized colchicines treatment combination of 50 mg·L ^{- 1} for 40 d. After separated and subcultured 3 to 4 times, the chimeras were effectively purified and the purified plantlets were proliferated and rooted. The chromosome number of root-tip cells of the purified plantlets was 2n = 4x = 48. The section of paraffin-embeded shoot apices and leaves showed that the tetrap loid leaves were thicker than diploid, the fence tissue and sponge tissue are more up growth, and the cell size of each layer of the tetraploid was larger than that of the dip loid, which p roved that the autotetraploid was obtained. Compared with the diploid, the tetraploid leaves showed bigger, darker and thicker with larger leaf serration and guard cell and
lower density of stomas. In addition, the induced plantlets showed slower growth, smaller leaf index and shorter internode during the course of induction, which was only a temporary phenomena.

Key words: Ziziphus jujuba, Z. acidojujuba ( Z. spinosa Hu), Colchicine, Tetraploid