FREEZING SURVIVAL OF ILLINI HARDY BLACKBERRY FLORAL TISSUES BEFORE AND AFTER BUDBREAK

Dormant floral buds and inflorescences of 'Illini Hardy' blackberry (R ubus sp.) plants were subjected to controlled freezing tests. The susc eptibility of dormant floral buds to low temperatures was determined b y differential thermal analyses (DTA) and the hardiness of individual flowers at various stages of development was determined by viability t esting. The mean temperature at which all low temperature exotherms (L TEs) were detected in primary buds was -15.0, -18.4, and -13.8-degrees -C in November, january, and March, respectively. The mean LTE tempera ture for secondary buds was -24.8-degrees-C in january and -18.9-degre es-C in March, indicating that secondary buds could provide a replacem ent crop when the primary bud was injured. After budbreak, inflorescen ces deacclimated as bloom progressed. When the flowers were in tight b ud, the temperature range in which all flowers in the inflorescence we re injured was 1.6-degrees-C. However, when the terminal flower was at full bloom or at a later stage of development, the critical temperatu re range was less-than-or-equal-to 0.3-degrees-C.