When Warm Breaks Cold: Understanding Deacclimations and Reacclimations Cycles as a Key to Winter Crop Resilience.

Plants such as winter crops are able to acclimate to low temperatures through complex physiological and biochemical modifications that enhance their frost tolerance. Cold acclimation involves changes in, e.g., photosynthetic efficiency, carbohydrate metabolism, the accumulation of osmoprotectants, the remodelling of membrane lipid composition, and the activation of the antioxidant system. Now, due to ongoing global climate change, temperature fluctuations have become more frequent, particularly during the autumn-winter period. Episodes of warm breaks (mainly above 9 °C) during winter disrupt the cold acclimation process and induce deacclimation, leading to a decrease in frost tolerance and a partial reversal of cold-induced metabolic adjustments. However, deacclimation is not just the reversal of acclimation, as evidenced by distinct responses in metabolites and hormones. Moreover, plants are able to regain lost freezing tolerance through reacclimation upon re-exposure to low temperatures. The article aimed to summarize the current knowledge on the basics underlying cold acclimation, deacclimation, and reacclimation. An explanation of these processes is crucial for protecting winter crop plants under the increasing frequency of variable temperatures during their growth.