|Gusta, Lawrence - U OF SASKATCHEWAN, CANADA|
|Fuller, Michael - U OF PLYMOUTH, U KINGDOM|
Submitted to: HortScience
Publication Type: Review Article
Publication Acceptance Date: February 20, 2008
Publication Date: September 1, 2008
Citation: Wisniewski, M.E., Glenn, D.M., Gusta, L., Fuller, M.P. 2008. Using infrared thermography to study freezing in plants. HortScience. 43(6):1648-1651. Technical Abstract: Factors that determine when and to what extent a plant will freeze are complex. While thermocouples have served as the main method of monitoring the freezing process in plants, infrared thermography offers distinct advantages, and the use of this latter technology has provided new insights on the processes of ice nucleation and propagation. This technology is based on the fact that freezing is an exothermic event. The temperature and spatial resolution of a high-resolution infrared camera have enabled researchers to clearly define initial sites of nucleation, as well as, monitor the ice front as it spreads into surrounding tissues. Ice nucleation is induced by both extrinsic and intrinsic nucleators. Ice-nucleation-active bacteria and moisture are two major extrinsic agents. In herbaceous plants, the influence of extrinsic ice nucleators on ice nucleation can be moderated by thick cuticles or the application of synthetic hydrophobic barriers. The situation in woody plants, however, is different. Woody plants appear to possess native, intrinsic nucleating agents that are as active as many extrinsic agents. The identification of the intrinsic nucleating agents in woody plants is not known. Despite the presence of intrinsic nucleating agents, barriers exist in woody plants that inhibit growth of ice from older stems into primary, lateral appendages. This is important, because many tissues in woody plants that are frost sensitive are flowers and primary, elongating, shoot tissues that arise from buds attached to older stems. Pictures derived from video segments of the freezing process and data on the ability to block nucleation via the use of hydrophobic kaolin are provided.