Abstract: One year old grafted seedlings of Ziziphus jujuba Mill. cv. Dongzao, Linyilizao and Lajiaozao were treated with colchicine at the shoot-tip. The results indicated that the highest induction rate of Linyilizao was 50 % with optimum treatment combination of 0.15 %/ 18h ; the highest induction rates of Dongzao and Lajiaozao were both 43.3 % , and the optimum treatment combinations were 0.1 %/ 30 h and 0.15 %/ 18 h respectively. The chromosome number of the shoot-tip of the mutated plants (2 n = 4 x = 44)
and the DNA content were both twice that of the cont rol. In addition , the chromosome number of some mutated Lajiaozao was 2 n = 2 x + 2 = 26 , and some octoploid cells were found in mutated Lajiaozao. The leaf length , width and area were larger and the leaf index , internode length were smaller than those of the diploid plants. The induced polyploid materials also showed larger stomatas , more chloroplasts , and larger but more deformed pollens. The decrease of pollen fertility and some tet racolporated pollens were also observed.

Key words: Ziziphus jujuba Mill., Colchicine, Polyploid, Induction