| Douglas-fir[Pseudotsuga menziesii] is one of the most important and valuable timber trees in the world. It is a major component of the forests in America and Canada. Presently, it has been successfully introduced in many reigions in China. Because the seed production is low,and the seeding time is long , the seed supply are far away from the needs of afforestation. Cuttings as a regeneration procedure has demonstrated that reliable rooting of cuttings was limited to the material trees less than 10 years old. All these limit douglas-fir to spread. So the study of Douglas-fir in vitro and regeneration is important in theory and practise. It not only can supply a lot of seedlings which has good wood quality at short time, it also tentative explore the effective way of Douglas-fir for plant breeding providing some theorial bases. This article maked mature embryo and seedlings of Douglas-fir as explant, researched the system of the rapid proliferation in Douglas-fir by the way of tissue culture. The results were as following: (1) When callus development was initiated with the mature embryo of Douglas-fir, the basal medium had some influence. Medium of high salt concentration favoured development of callus. Decreasing the salt concentration of medium would reduce the callus. Hormone in this prosure was a key factor. Only supplement 6-BA was enough on induction adventitous buds. Supplemented with some concentration of NAA can increase callus number, however, when the concentration of NNA was too high, the browning rate of callus would be very high in subculture. The combination medium of modified DCR + 2.0 mg/L 6-BA + 0.01 mg/L NAA was optimal. Meanwhile, sucrose also had some influence on callus formation. 2%-3% of sucrose was the most optimal concentration. (2) During the prosure of adventitious bud formation from mature embryos, basal medium and hormone also made important role. In the six basal mediums, modified DCR was the best, WPM and SH were better than GD, MS and N6 were the worse. Only supplemented with 2.0mg/L 6-BA in adventitious buds formation, the rate of induction was highest. The optimal combination of medium was modified DCR+2.0 mg/L6-BA, on which 74% explants was induced , average inductive rate of propation was 6, and the highest rate of propagation was 11. (3) Different treatment of explants also had important influence. Soaked embryos in high concentration hormone before culture, the rate of germination and induction both were low and contamination rate was high, however, some adventitious buds has been gotwhich induced directly from explants. Cultured directly in inductive medium, adventitious buds only induced from callus. (4) It was showed by the experiment that selecting the sprout carrying cotyledons as explants was more difficult to built the regeneration system. As if in the optimal combination of medium modified DCR+3.0 mg/L6-BA, the inductive rate of both seedling which came from tests and soil were low. In the two kinds of seedlings, the later was worse,which inductive rate was only 22.6%, and the buds proliferation coefficient was 3.6; the other, the two datas were respectively 42.8% and 3.8. (5) Different treatment way of adventitious buds was important in tufted buds growth. Soaked adventitious buds in 18.26 mg/L NAA and 20.32 mg/L IBA (0.1mmol/L) before cultured in medium would promote the elongation of tufted buds. Especially, treated in the mix hormone for 3 hours, the growth of buds reached 1.2 cm in a month. In 1/2SH medium without hormone,average of growth of adventitious buds was 0.7cm in a month. Active charcoal was advantageous to continue development for tufted buds. GA3 was harmful to it. (6) In the experiment of Douglas-fir rooting, we obtained such a conclusion: rooting in out-test was better than in in-test. In out-test, the rooting rate of Douglas-fir was 12.7%, but even in the optimal combination of medium 1/2SH+NAA0.01 mg/L+IBA1.0mg/L, the rooting rate was only 5.2%.
|
PDF Full Text Request