STUDIES ON THE RELATIONSHIP OF LOW TEMPERATURE EXOTHERM AND FREEZING INJURY OF MEI FLOWER, ITS INTERSPECIFIC HYBRIDS AND THEIR PARENTAL SPECIES

Differential thermal analysis (DTA) was utilized to investigate the relationship of temperature freezing points or exotherm and cold injury of David's peach(Prunus davidiana), apricot (P.armeniaca), mei flower cultivars(P.mume cv.'Fenhong Mei'and P.mume cv.'Small Green Calyx') and their interspecific hybrids'Small Green Calyx'mei×David's peach, apricot×'Fenhong Mei'and'Fenhong Mei'×apricot, and freezing patterns of their xylem and bark. Two exotherms were observed in the xylem of these parents and their hybrids. Low temperature exotherms coincided with the killing temperature of xylem ray and parenchyma. There were differences between the parents and their hybrids. Only one high temperature exotherm occurred in the bark of the parents and their hybrids. There was no apparent correlation between these high temperature exotherms and freezing injury.