EFFECTS OF CHILLING DURING DORMANCY ON DEVELOPMENT OF THE TERMINAL BUD OF THE CRANBERRY

Exposure of the cranberry Vaccinium macrocarpon Ait. cult McFarlin to an accumulation of chilling temperatures below 7 C was required to break dormancy of the terminal bud. Dormant mixed-terminal buds that were not exposed to chilling temperatures did not initiate new growth even under long photoperiods. The number of days to bud break after termination of the chilling treatments was reduced as the length of the chilling treatments was increased. Rate of growth and final shoot length were also affected, but were more dependent on postchilling conditions than on the length of chilling. Chilling periods of 100 days or more were required for the induction of floral development. Chilling for less than 100 days usually resulted in vegetative growth only. Bud break after 125 days of chilling was more rapid when cyclic chilling conditions included a period of approximately 10 C during the day. The floral primordia of terminal buds in the field recommenced development in late February or early March and were well differentiated by the end of April.