Chilling-Hour Requirements of Fruit Crops
What Is a Chilling Requirement and Why Is It Important?
Many temperate, deciduous fruiting plants require a chilling period in order to break dormancy, grow, and fruit normally. This is why choosing species and varieties that are satisfied by the climatic conditions in a particular geographic location is important to achieve the best results. Plants begin to enter a resting period, called dormancy, once temperatures fall below 50°F for an extended period of time. Some species, and varieties within a species, may react to reduced day lengths as well as temperatures.
Aboveground growth ceases, and leaf fall occurs, signaling an entry into dormancy. Hormonal changes in the plant, especially a marked decrease in growth-promoting hormones, prepare it for the oncoming cold. Once into dormancy, chilling accumulation starts and continues until the requirement of the plant is satisfied. After the required amount of chilling accumulation has occurred, growthpromoting hormones begin to increase, preparing the plant for the onset of warmer temperatures.
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