 Freezing tolerance is enhanced as a gradual adaptation to low temperature through a process known as cold acclimation, which initiates the transition to prepare for subzero temperatures through alterations in rate of metabolism, hormone levels and sugars.Freezing tolerance is rapidly enhanced during the first days of the cold acclimation process when temperature drops.Depending on the plant species, maximum freezing tolerance can be reached after only two weeks of exposure to low temperatures.