Studies On In Vitro Flowering Of Dendrobium Nobile Lindl And Dendrobium Moniliforme

The effects of plant material, excision of shoot tip, hormonal regulation, C/N ratio and lower temperature on in vitro flowering of D.nobile Lindl and D. moniliforme Lindl were studied in these experiments. The main results were as follows:D.nobile Lindl plantlets germinated from the mature seed were cultured on 1/2MS medium supplemented with individual PP333, ABA or TDZ, the floral buds were induced but the frequency of floral buds induction lower. The normal flowers could be induced by PP333 or ABA but TDZ not.Increase in the content of P, K and C/N ratio might promote the induction of floral buds. The plantlets pre-cultured on J/2MS medium contained 0.5mg/L NAA and 0.3mg/L PP333 for 4 months were transferred onto MS (1/2N,2P,2K ) medium supplemented with 0.8mg/L PP333 and 0.08mg/L TDZ, the frequency of floral bud induction increased to 95.5% after 90 days, however, the frequency of normal flowers was rather lower. The pretreated plantlets cultured by PP333 and TDZ for 25 days were transferred onto hormone-free 1/2MS medium, the frequency of floral bud induction decreased to 55.5% while the frequency of normal flower 51.9%.In order to enhance the frequency of normal flowers , the pretreated plantlets with 2 or 3 new buds were transferred onto MS (1/2N,2P) medium supplemented with 0.5mg/L PP333 and 0.05mg/L TDZ for 25 days, and then exposed to lower temperature 23℃/18℃(day/night) for 45 days by excision of shoot end. The frequency of floral bud induction was about 45.3%, but the frequency of normal flower highly reached 80.9% after 60 days. In addition, the new stems from the flowered plantlets were not suitable to induce normal flower.Additionally, the number of floral buds could be also promoted if the plantlets pre-cultured by "PP333 +ABA". The optimal scheme for inducing floral buds was that the plantlets pre-cultured on MS medium supplemented with 0.8mg/L PP333 and 1.0mg/L ABA for 35 days firstly were transferred onto MS(1/2N,2P,2K) medium supplemented with 1.2mg/L PP333 and 0.12mg/L TDZ. The frequency of floral bud induction reached 97.8% after a periodof 90 days, but the frequency of normal flowers was lower. The optimal scheme for inducing normal flowers was that pre-culruring the plantlets on MS medium supplemented with 1.2mg/L PP333 and 1.0mg/L ABA for 35 days, and then transferred onto MS(1/2N,2P,2K) medium contained 0.8mg/L PP333 and 0.08mg/L TDZ. The frequency of normal flower and floral bud induction reached 72%, 42% respectively after the same period. The plantlets couldn't be induced to become normal flower onto MS(1/6N,2P,2K) medium contained TDZ by excision of shoot end after pre-cultured by "PP333 +ABA". While the plantlets from PLBs had an indistinctive effects on in vitro flowering of D.nobile Lindl.It was easier to screen the optimal medium for inducing floral buds and normal flowers on D. moniliforme Lindl under the similar treatment. The number of floral buds and normal flowers was obviously promoted if the plantlets pre-cultured by "PP333 +ABA" or TDZ individually. The optimal scheme was as follows: pre-treated the plantlets on 1/2MS medium supplemented with 0.4mg/L PP333 and l.Omg/L ABA for 90 days firstly, then transferred onto MS(1/6N,2P,2K) medium contained 1mg/L PP333 and 0.1mg/L TDZ. The frequency of floral bud induction and normal flowers reached 93.3%, 80% respectively after 150 days.