By Maicy Vossen
This article was originally published on the WinterTurf project blog.
Technology is allowing researchers to gain new insights into the freezing of plants. Growers care about the temperature at which plants freeze so they can determine the environmental conditions that will be harmful to the perennial plants we grow in northern latitudes. Researchers use this information and knowledge about how ice spreads through the plant so we can figure out the mechanisms behind ice damage in plants. This is studied through differential thermal analysis. The reason we can use this technology to study ice formation in plants is because when liquid water freezes, there is a small amount of heat released as the phase change from liquid to solid happens. By using different types of thermometers, the heat released can be measured and the air temperature at which the plant froze can be recorded. One study used this technology to study the freezing of different floral organs of sweet cherry (Kose & Kaya, 2022). Floral organs were placed onto trays which were able to capture the release of heat when ice formed within the floral organ. From this study, researchers determined that different floral organs are more susceptible to freeze damage than others.
Another technological advance came through the use of infrared imaging and video thermography to study ice formation and spread through the plant. These studies have been completed in both outdoor field conditions and controlled growing environments in growth chambers. Infrared video and high-speed imaging can capture this spike in temperature and visually in the infrared images by color change and researchers use this to determine when ice formed (Wisniewski et al., 1997). External thermometers are used to determine the air temperature at which ice was formed in the plant.
Video footage shows how freezing differs between plants and within plants. To view these videos, download the MOV files from the open access article from Livingston et al., 2018. If you zoom in closer using high-definition infrared thermography, you can actually see ice spreading through a single vessel in the plant and even closer visualizations on a single leaf you can see individual cells freezing in the plant (SV4; Livingston et al., 2018). From these videos researchers are able to determine the site of ice formation in the plant, the speed at which ice spread throughout the plant, which sites in the plant freeze before others and if they even freeze at all. This information can inform other genetic and metabolomic studies for effective data collection and eventual plant breeding efforts.
References
Kose, C., & Kaya, O. (2022). Differential thermal analysis reveals the sensitivity of sweet cherry flower organs to low temperatures. International Journal of Biometeorology, 66(5), 987–994.
Livingston, D. P., Tuong, T. D., Murphy, J. P., Gusta, L. V., Willick, I., & Wisniewski, M. E. (2018). High-definition infrared thermography of ice nucleation and propagation in wheat under natural frost conditions and controlled freezing. Planta, 247(4), 791–806.
Wisniewski, M., Lindow, S. E., & Ashworth, E. N. (1997). Observations of Ice Nucleation and Propagation in Plants Using Infrared Video Thermography. Plant Physiology, 113(2), 327–334.
This project is supported by the U.S. Department of Agriculture, National Institute of Food and Agriculture, Specialty Crop Research Initiative under award number 2021-51181-35861. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.