Tissue Culture And Rapid Propagation Of Rare And Precious Species Cercidiphyllum Japonicum

Cercidiphyllum japonicum Sieb. et Zucc, a famous relict plant in east Asia, is a rare and precious plant of the national second-grade protection of China. It is currently in imminent endangered condition, because the species is dioecism and natural regeneration is difficult with low fruit set and tiny seeds. Tissue culture has proved to be an effective measure for species preservation and rapid propagation of rare and precious tree species, including the plant Cercidiphyllum japonicum.The purpose of the thesis is to establish the technique system of tissue culture and rapid propagation of C. japonicum. Various materials, e.g. the current-year and 1-year-old stem with auxiliary buds, leaf blade, petiole, bud, immature seeds were examined for their efficiency as explants. The main results are represented below. The current-year stems with auxiliary buds are good explants. Sampling season, explants type, and disinfection time were all key factors affecting auxiliary buds induction rate. June in Ji Yuan was the optimal sampling season. The second to fifth buds from the top are all suitable for explants. The use of 70% ethyl alcohol for 10 seconds and 0.1% HgCl for 6 to 8 minutes is enough for disinfection. One-year-old stems with axillary buds and winter buds had high potential for auxiliary buds induction; however, they are not good explants due to low induction rate (4.4% and 4.7%, respectively) in our experiments.Immature seed is also a good explant. From pollination 60 days afterwards, immature seeds shows no dormancy and can easily germinate on MS medium, with a germination rate of 95%. On the medium supplemented with 6-BA and NAA, the hypocotyl of germinated seeds grows sturdily with some quantity of callus.Both leaf blade and petiole can produce small quantity of callus on the suitable medium, and especially petioles had an induction rate ranging from 66.7-100%. The color and quality of callus varies with the types of medium and hormone level.Besides, the time taking for callus induction and the callus quantity petiole are less in petiole compared to leaf blade.The optimal cultural conditions are 14 h illumination (26℃, 2000-3000 lx): 10 h dark (24℃).MS supplementary with 6-BA (0.5mg/L) and NAA (0.2mg/L) was the optimal medium for the current-year stems with auxiliary buds in the initial induction, with an induction rate of 98.2%. On the medium 1/2 or 1/3MS supplementary with 6-BA (0.5mg/L) and NAA (0.2mg/L), the propagation time is 5.3. Rooting ratio is 90% on the 1/2MS or 1/3MS supplementary with 6-BA (0.05 mg/L or 0.1mg/L) and IBA (1.0mg/L or 1.3mg/L) medium. The germination rate of immature seeds are 95% on the MS supplementary with KT(0.5mg/L) medium. The propagation time was 6.3 on the MS supplementary with 6-BA (1.0mg/L) and NAA (0.1mg/L) medium. Rooting ratio is 95% on the MS supplementary with IBA (1.0mg/L) medium and each plantlet can produce 4 to 9 roots.Training plantlets are conducted when seedlings have a centimeter of 4 to 5, transplanting in the matrix of vermiculite and pearlite (1:1). The seedlings are allowed to grow at 25 to 30℃, relative humidity 80%. The survival rate of plantlets is about 95%.In summary, the technique system of tissue culture and rapid propagation of Cercidiphyllum japonicum is established in the thesis, using the current-year stems with auxiliary buds and immature seeds as explants.