Studies On Several Dormant Characteristics Of Different Pear Rootstocks

The experiments were studied in the College of Horticulture and Plant Protection, Yangzhou University, from October 2012 to March 2015. P.betulaefolia Bunge, P.calleryana Decne, P. pyrifolia Nakai, P. pashia Buch and P. xerophila Yu five kinds of rootstocks were used as experimental materials in this paper. The effects of rootstocks on the chilling requirement of the scion were examined, the differences in different pear rootstocks chilling requirements of seeds and buds of the different species and strains were compared, the influences of root in regulating buds dormancy were discussed.The main results were as follows:1.There was a close relationship between the chilling requirement of the rootstocks and the dormant process of leaf buds in Housui scion. The rootstock of low chilling requirements was helpful to accelerate the dormant process of the scion varieties, high chilling requirements could delay the dormant process of the scion varieties; The average differences of chilling requirements which were calculated by linear regression and accumulation normal distribution function were about 30h.It might be thought that the two kinds of statistic methods could decrease the random error effectively in estimation of chilling requirements; Since the standard error of the linear regression (SY/x) in?7.2? model was the smallest among the three kinds of models, it was thought that the?7.2? model for estimation of chilling requirements seemed superior to the 0-7.2? and the Utah models in the accuracy and reliability.2. There were significant differences in the chilling requirements of five kinds of rootstocks. The chilling requirements of buds in P. pyrifolia were only 422h, but the chilling requirements of buds in P.xerophila attained to 1508h. The differences of chilling requirements between P. pyrifolia and P.xerophila were about 1086h(?7.2? model). The range of chilling requirements of buds in P. pashia, P.calleryana and P.betulaefolia were 422h-1508h.3.The effects of stratification at 10? on breaking dormancy of rootstock seeds were better than that at 5?. It indicated that the?7.2? model and the 0-7.2? model were not suitable for evaluating the chilling requirements of seeds,but the Uath model was suitable for evaluating the chilling requirements of seeds.4. The chilling requirements of buds had a close association with the chilling requirements of seeds which were from the same rootstock. It could be found that the chilling requirements of buds were high, the chilling requirements of seeds were high too.5. The difference of bud chilling requirements was about 300h(?7.2? model) in different strains of the P.calleryana species, which indicated that although the same method calculating the chilling requirement was used in the same ecological conditions, the significant differences of the bud chilling requirements were also found in the different strains of P. calleryana.6.The roots had the regulation for the start and the end of bud dormancy, which may be realized by transporting the physiological active substances that synthesized in roots for promoting or releasing dormancy from roots to buds.7. Raising the rhizosphere soil temperature could significantly reduce the chilling requirements of shoots.25? treatment played a better role in breaking bud dormancy than 15? treatment.