Unveiling winter dormancy through empirical experiments

Temperate woody perennials enter into a dormant status during winter in order to survive low temperatures. However, dormancy is not just a survival strategy, since cold winter temperatures are required for proper flowering. Global warming is having an impact on the phenology of woody perennials; warmer temperatures during dormancy may lead to an erratic reproductive behaviour due to the lack of chilling accumulated during winter. Although the relevance of dormancy for the adaptation of temperate woody perennials is well known, the biological processes behind dormancy remain unclear. In this work, we review how shoot and seedling experiments have contributed to the current knowledge on dormancy in woody perennials from the early discovery of the role of cold temperatures for adequate flowering to the latest knowledge on dormancy physiology and genetics. The information available has been organised in seven sections: (i) Climate change and winter dormancy in woody perennials; (ii) Discovering the importance of cold and the establishment of dormancy bases; (iii) Experiments to estimate the dormancy period; (iv) Exploring the physiology of dormancy; (v) Looking for biological markers for the dormancy status through histochemical techniques; (vi) Molecular biology of bud dormancy and (vii) Conclusions and perspectives.