2.Low temperature could improve to break dormancy There are three methods to determinate the end time of fruit trees bud dormancy: 7.2℃ low temperature model, Utah model and dynamic model.
3.Methods: PCD was detected by TdT-mediated dUTP nick end labelling (TUNEL) in different stages of tooth development of SD rat. Results: The TUNEL showed that there was consistent PCD present in the bud stage, cap stage and bell stage.