FREEZING-INJURY TO PERSIMMONS (DIOSPYROS-KAKI THUNB.) AND 4 OTHER DIOSPYROS SPECIES DURING DEACCLIMATION IN THE SPRING AS RELATED TO BUD DEVELOPMENT

The cold hardiness of the buds in five cultivars of persimmon trees (D iospyros kaki) and four other Diospyros species during deacclimation i n spring was examined by computer-assisted thermal analysis (TA) and b y the freezing test under a constant freezing temperature (-10 degrees C). TA revealed that the cold hardiness of the bud decreased, that is , exotherm temperature of the bud rose rapidly after budburst in all c ultivars and species examined. The cold hardiness determined by the fr eezing test under a constant temperature was closely correlated with t he developmental stage of the bud. It decreased rapidly as the bud swe lled, and was the lowest around the time of budburst in all cultivars and species examined. After budburst, it gradually increased with shoo t growth, somewhat differently with cultivars and species. In other wo rds, all cultivars and species were the most susceptible to freezing i njury at the budburst stage, but the cultivar- or species-specificity in cold hardiness was expressed by the hardiness of young shoots devel oped after budburst. Frost injury to persimmon trees caused by the unt imely frost in mid-April at the experimental orchard of Kyoto Universi ty was discussed in terms of the time of budburst in each cultivar. (C ) 1998 Elsevier Science B.V. All rights reserved.