Establishment And Perfection Of In Vitro Regeneration System Of Fraxinus Mandshurica Rupr.

Embryo hypocotyls of mature seeds of Mandshurican ash (Fraxinus Mandshurica Rupr.) were used as explants. Then in vitro culture of this species was investigated.Adventitious buds were obtained from embryo hypocotyls explants. Maximum regeneration occurred after 2 weeks of culture. TDZ showed its advantages over BA on the initiation of adventitious buds. The results showed that MS medium supplemented with 1?mg/L TDZ could induced maximum adventitious buds. A few of buds elongated in subculture, and then rooted in rooting medium. Thus rooting seedlings of Mandshurican ash were obtained. However, mortality of explants and short buds were two big problems.On the basis of the above studies, factors affecting the mortality of adventitious buds of Mandshurican ash and ways to stimulate the elongation of buds were studied. High-salt medium (MS) was effective to the regeneration of adventitious buds, but resulted in higher mortality; Low-salt medium (WPM), while had no advantages over other media on the induction of adventitious buds, supported the continuous growth of adventitious buds of Mandshurican ash.. The combination of TDZ and BA was more effective than used alone on adventitious bud regeneration. Additionally, this combination could reduce the mortality of the adventitious buds. MS medium supplemented with TDZ 2mg/L and BA 0. Olmg/L resulted in best regeneration (83. 3%). In subculture, WPM medium was used, because it was more friendly than other media for the growth of explants. BA, when combined with IBA, showed its effectiveness on the growth and elongation of the adventitious buds. Best result was obtained on medium supplemented with BA 2mg/L and IBA 0.01mg/L.The results indicated that the "co-effects" of media, cytokinins and auxins , especially the balance of hormones played important role in the regeneration of Mandshurican ash and development of regenerated buds.