Study On Artificial Seeds Of Nicotiana Tabacum L.

The studies of somatic embryogenesis and artificial seeds were carried out in Nicotiana tabacum L. cvs. K320, Yun85 and Hongda. The main results were as follows:1. The effects of cultivars (genotype), hormone combinations on the induction of calli and adventitious buds from leaves were analyzed. The embryogenic calli (Type 3) suitable for induction of somatic embryogenesis were screened out. The result indicated that the most best hormone combination of bud induction and differentiation was 0.5 mg/L IAA+2.0 mg/LKT.2. The capacity of somatic embryogenesis was investigated through culturing calli derived from the leaves of the above 3 cultivars on MS media supplemented with different hormones. The results obtained showed that the capacities of somatic embryogenesis were different among cultivars; the time of light was also an important factor affecting somatic embryogenesis; and the different combinations of hormones affected the frequency of somatic embryogenesis. The highest frequencies of K326, Hongda and Yun85 were 8.3%, 47.4% and 61.1%, respectively. Correspondingly the combinations of hormones were 2.0 mg/L NAA + 0.5 mg/L BA, 2.0 mg/L NAA + 0.2 mg/L BA and 2.0 mg/L NAA +0.5 mg/L BA, respectively. Growth phases of somatic embryogenesis and the whole plantlets germinated from somatic embryos were observed in the experiment.The frequency of somatic embryogeneis reached 100% on the media with TDZ. The number of the somatic embryos induced differed with theconcentrations of TDZ, and the most amount of somatic embryos occurred with 0.2 mg/L TDZ. The somatic embryos induced by TDZ grew into seedlings without maturation culture on the original medium.Furthermore, something like globular embryos were observed while calli were induced from mesophyll protoplasts, but somatic embryos weren't obtained directly through the culturing mesophyll protoplasts. Calli derived from mesophyll protoplasts produced somatic embryos in the dark, and the suitable medium was MS solid medium adding 2.0 mg/L CPA, 0.5 mg/L KT, 20g/L sucrose and 3 g/L AC.3. Artificial seeds were produced using somatic embryos differentiated from leaf calli (Propagule I), buds growing from somatic embryos derived from leaves (Propagule II) and adventitious buds directly induced from leaves (Propagule III). Artificial seeds produced through two methods including calcium-alginate beads and calcium -alginate hollow beads had high germination rate under sterile condition. Artificial seeds from propagule II and HI germinated at high frequencies of 80% and 82%, respectively, but the artificial seeds from Propagule I did not germinate. The germination rate of artificial seeds obviously reduced after long-term storage at low temperature.4. RAPD technique was used to test whether regenerated plants of artificial seeds held the excellent characteristic of mother plants. Plantlets germinated from artificial seeds produced from three propagules all maintained the characteristics of parents without aberrance.