Studies On Flowering In Vitro Of Dendrobium Huoshanness

The time for wild Dendrobium huoshanness to flower is about 3years . Flowering is a unique developmental event in the life cycle of a higher plant . Studying D. huoshanness flower bud formation and development and decreasing the juvenile phases is important . In vitro flowering by plantlets produced through tissue culture was studied . And in vitro flowering was induced by many ways in the whole year. It is helpful to further our understanding of flowering regulated.The objective of this research was to study flowering may have been induced by many factors, such as TDZ, BA, sucrose, lower temperature 15/5 C nitrogen, and time of transferring to new medium(MS medium lacking plant growth regulator. Flowering was induced in 4-month-old D. huoshanness plantlets and pseudobulbs in an in vitro system. After having screened the optimal medium which induces flower bud initiation on D. huoshanness plantlets, levels of endogenous IAA,GA3 and ABA were studied by HPLC. Soluble proteins were studied by SDS-PAGE. At the same time morphological differentiation of floral buds were observed, and the time of flower bud initiation was found out.The results of our research show that a larger number of floral buds were produced in the MS(1/6N,5P) medium added 40 g/L sucrose and 0.02g/L TDZ. Plantlets, which were new stem growth from subcultured plantlets, were induced to form floral buds in 2-5 months. The rate of flower induction was about fifty percent. Terminal or axillary flowers were formed on plantlets. TDZ at lower concentration was suitable for inducing terminal flowers but higher concentration induced botryose inflorescence . BA was less effective in the induction of floral buds. MS containing reduced concentrations of nitrogen sources, and lower temperature pretreatment promoted the formation of floral buds. In order to make it flowering normally, Plantlets were transferred to hormone-free MS medium after cultured in medium with TDZ.The optimal medium for inducing floral buds is MS medium added 0.02 mg/L TDZ, 40 g/L sucrose and 8g/L agar. The inefficient medium for inducing floral buds isMS medium added 40 g/L sucrose and 8g/L agar.The pH of all media used in this study was adjusted to 5.6-5.8 with IN NaOH. Physiological characteristic during flower induction were studied by culturing the plantlets in two kinds of medium . Results showed that axillary floral buds were induced after 90 days of culture. And there was a notable increase on the level of endogenous IAA during 90-120 days contrast to CK. The level of endogenous GA3 wasn't related to the formation of floral buds. A special soluble protein was also found during 90-120 days when plantlets cultured in the optimal medium.