Research Of Generating Callus And Induction Of Polyploid In Ziziphus Jujuba Mill.

The tetraploid plants of 'Lizao' (Ziziphus jujuba cv. Lizao) and 'Dongzao' (Z jujuba cv. Dongzao) were first obtained by treating callus produced on the cut stems in the field with colchicines. The callus was obtained by treating leaves of 'Dongzao' and 'Lajiaozao' in vitro, and the leaf callus was treated with colchicines by dipping the callus into colchicines or co-culture with colchicines. The tetraploid plants and the diploid plants were also compared morphologically and cytologically. And the browning in callus production and mutagenesis was also analyzed.1. Stem diameter, cover methods of the stem, sorts and concentrations of growth regulators, AgNO₃ concentration influenced the callus formation when the stems were cut. Callus began to appear 5 days after the stem were cut and treated with 4.0mg/L TDZ or 2.0 mg/L AgNO₃ and covered with mud and black plastics. The proper stem diameter was 2.2-4.2cm.2. Medium, sorts and concentration of growth regulators influenced the leaf callus formation in vitro. The optimized callus formation conditions of callus formation for Dongzao were: 1/2 MS medium, TDZ 1.0mg/L. While that for Ljiaozao were: WPM medium, TDZ 0.5mg/L. The proper culture condition for both of the two cultivar was 14 days of dark-culture at 25³4℃.3. The mutagenesis results differed with cultivar, colchicines concentration and mutagenizing time in vivo. The callus mutation ratio reached 13.3% with 24h of treatment with 0.05% colchicines in Lizao and it topped 6.7% with 18h of treatment with 0.05% colchicines in Dongzao.4. The mutagenesis results differed with material, mutagenizing methods and time in vitro. The callus mutation ratio reached 13.3% by dipping leaf callus into 0.01% colchicines for 4d and the mutation ratio of the callus formed after 10d of pre-culture topped 6.7% after 15d of co-culture with 0.004% colchicines in Dongzao.5. Growth regulator concentrations in the medium influenced successive transfer efficiency of the leaf callus and the 1/2 MS medium with 0.5mg/L TDZ gave best??successive transfer in Dongzao.6. Comparing with diploid plants in vivo, all the mutated tetraploid plants showed thicker, much round, larger leaves with deeper color, fewer and enlarged serration. Cytological study showed that the mutated tetraploid plants had 48 chromosomes, ie. 2n=4x=48 while original Lizao and Dongzao had 24 chromosomes, ie. 2n=2x=24. The stoma density in leaves obviously decreased while the size increased and the number of chloroplasts in guard cells increased in tetraploid plants. The DNA content analysis showed doubled DNA content in the stem apex and young leaves in mutated plants.7. Harm of colchicines on callus firstly showed browning and then showed fatal in vitro. Antioxidants or quinine could prevent Dongzao leaf callus from browning and 0.5g/L PVP showed best result.