Submitted to: International Symposium on Plant Cold Hardiness
Publication Type: Abstract only
Publication Acceptance Date: 8/2/2008
Publication Date: 8/3/2008
Citation: Wisniewski, M.E., Gusta, L.V., Karlson, D. 2008. Ice nucleation, propagation, and deep supercooling: the lost tribes of freezing studies. International Symposium on Plant Cold Hardiness. Saskatoon, Canada. Book of Abstracts, pg.2. Interpretive Summary:
Technical Abstract: Prior to the emphasis on the molecular biology of cold acclimation, a considerable amount of research was conducted on the processes of ice nucleation and deep supercooling. In many species, these two processes are critical to surviving episodes of freezing temperatures. Over the past two decades, however, research on these topics has drastically diminished. The objectives of the current report are to review these topics and identify critical questions that still need to be answered, as well as, indicate how this information may lead to new strategies in improving cold hardiness in some plant species. Ice Nucleation and Propagation – Beginning in the late 1970’s, a considerable amount of research focused on ice nucleating agents and their role in inducing plants to freeze at warm, subzero temperatures. Research focused on the identification of extrinsic, especially ice-nucleation-active (INA) bacteria, and intrinsic nucleation agents and their role in the freezing process. While published research in this area diminished greatly in the last decade of the century, new insights were gained when high resolution infrared thermography was employed to study the freezing process and new information on antifreeze proteins was published. A review of these findings will be presented. Deep supercooling – Of the many aspects of biological ice nucleation and cold hardiness of plants, deep supercooling is perhaps the most enigmatic. The ability of some plants to maintain symplastic water in an unfrozen condition and without movement of water into the apoplast is a remarkable adaptation that has not failed to impress both biophysicists and plant physiologists. Although the ability of woody plant tissues to avoid freezing by deep supercooling was first documented in the 1960’s, the mechanism that allows small domains of water to avoid freezing, despite the presence of extracellular ice, remains little understood. While a great amount of attention has been placed on identifying genes responsible for cold acclimation and understanding their regulation, a similar effort on deep supercooling has been absent. While deep supercooling is considered to be largely a biophysical trait related to the composition of cell walls, evidence suggests this contention needs further evaluation. Even though cell wall composition and tissue structure play a critical role in deep supercooling, there are many aspects that must be genetically regulated either during development or even on an annual basis. Evidence to support this premise will be presented.