Fig. 3.

Schematic illustration of the impact of climate change on cold acclimation. Cold acclimation is caused by a complex interaction between a decreasing photoperiod and decreases in temperature. Climate change can delay the time of cold acclimation, and cold acclimation will be affected by erratic temperature events. Global warming can directly reduce the effectiveness of cold acclimation by disrupting the combined effects of photoperiod and temperature. Elevated CO₂ concentration affects plant cold acclimation and freezing tolerance by nucleating ice in cells, increasing leaf temperatures, delaying the timing of cold acclimation, and changing xylem sap pH. The increase in leaf temperatures may affect membrane fluidity and the activity of calcium channels, and, thus, subsequent cellular signaling. Changes in xylem sap pH may affect the chemical characters of several COR-gene products and ABA signaling. Elevated CO₂ concentration can affect both the timing and rate of cold acclimation in combination with warmer temperatures, shorter photoperiod, and lower irradiance. CBF C-repeat binding factor, CCA1 circadian clock-associated 1, CO₂ carbon dioxide, LHY late elongated hypocoty l, PhyB phytochrome B, PIF3/4/7 phytochrome-interacting factor 3, 4 and 7, R/FR red to far-red ratio