Influence of Prolonged Exposure to Chilling Temperatures on Bud Break and Heat Requirement for Bloom of Several Fruit Species

Abstract

Shoots of apple ( Malus domestica Borkh.), cherry ( Prunus avium L.), peach [ Prunus persica (L.) Batsch] and pear [ Pyrus communis × Pyrus pyrifolia (Burm.) Nakai] were collected and used in these studies. In all instances, chilling beyond that required for 50% bud break within a 2-week period (prolonged chilling) resulted in a decrease in the growing degree hours required for bud break. In many cases, over 90% of the variation in each study could be attributed to the added chilling.