STUDIES ON THE RELATIONSHIP OF LOW TEMPERATURE EXOTHERM AND FREEZING INJURY OF MEI FLOWER, ITS INTERSPECIFIC HYBRIDS AND THEIR PARENTAL SPECIES Freezing injury of plant and oxidative stress-Superoxide generation in freeze-thaw cycles of Cabbage leaf tissues Freezing Injury Investigation of Apricot and Sweet Cherry Flowers Spatial and temporal patterns of freezing injury during winter in Huang-Huai Winter Wheat Area under climate change THE ICE NUCLEATION ACTIVE BACTERIA ON POPLAR TREES AND THEIR EFFECTS IN THE COURSES OF CAUSING FREEZING INJURY AND INDUCING FUNGOUS CANKER Freezing Injury Investigation of Apricot and Sweet Cherry Flowers