Effects Of Chilling And GA₃ Treatments On The Dormancy Releasing And The Growth And Development Of Paeonia X Suffruticosa 'Ming Xing'

Forcing culture, an important way in the production of both cut-flowers and pot-plants of tree peonies, constitutes a great part of the industrialization for peony industry. Dormancy releasing of tree peony bud is the key factor for the techniques of forcing culture and all-year production, but its characteristics is varied with cultivars, so should be the research of domancy releasing.'Ming Xing', one of Paeonia suffruticosa varieties, has relatively short plant height,red colour,double flowers,and blooms from the end of April to early May, is very prospective for forcing culture as pot plant.The chilling requirement of'Ming Xing'dormancy releasing was measured both in field and controlled chilling conditions, with Utah model as the evaluation model; then according to the chilling requirement known above, controlled chilling in shorter duration, as well as controlled chilling combined with gibberellin were used to force'Ming Xing'successfully by Spring Festival with different chilling amout in autumn last year. The main results are as follows:1. Dormancy was not released by 504 CU under controlled chilling at 4℃whereas it was partly released under field chilling by 254 CU, which indicates that field changeable chilling was more efficient than controlled chilling.2. Dormancy was released with the maximum sprouting regularity and a flowering rate of 94.4% when the chilling unit (CU) accumulated to 1176 in controlled 4℃chilling for 7 week; while in field chilling treatment, the maximum sprouting regularity occurred at 576 CU with a flowering rate below 80%, and a broad and uncontrolled fluctuation of temperature accounts for the possible explanation. Further research on feasible temperature variation and chilling duration for dormancy releasing in the forcing culture of tree peonies is needed .3 Treatment combined with GA3 improved sprouting regularity and flowering rate , also reduced the accumulative temperature for flowering when chilling requirement was not fulfilled. The experiment proved there was high sprouting regularity and flowering rate above 80% under the treatment of controlled chilling at continuous 4℃for 5 weeks with GA3 300 mg.L-1,500 mg.L-1,6 weeks with 100 mg.L-1,300 mg.L-1,500 mg.L-1, and showed no significant difference in plant height and width, flower diameter, leaf area and stem length.