Plant Response to Freezing Stress

Our system for determining freezing tolerance of plant tissues. This system consists of aluminum chambers (top right) in which plant samples are imbedded between two layers of moist sand (the moist sand prevents supercooling of the plant tissues and thus allows the determination of freezing tolerance). Medium gage Type-T thermocouples are also imbedded in the moist sand to measure the temperature of the plant tissue during the freezing experiment. The thermocouples are attached to a Campbell Scientific CR-21X datalogger. The aluminum chambers are covered with closed-celled insulation and set on a heating table prior to being placed in a freezer. The freezer is set at a constant temperature of -40°C, while the heated table is maintained at 0°C until the sand freezes. A programmable temperature controller subsequently lowers the heat to the heating table so that the aluminum chambers cool at a rate of about 3°C per hour. The aluminum boxes are removed at various temperatures (e.g., -5, -10, -15°C, etc.) and allowed to slowly thaw. Plant tissues are then removed, and incubated on moist filter paper in a petri dish in diffuse light for up to five days prior to examination for freezing-induced injury. Measurements of chlorophyll fluorescence, electrical conductivity, and tissue death are used to determine the level of freezing tolerance in the samples tissue.

With:
John D. Marshall, Associate Professor, Department of Forest Resources
Wesley S. Hunt, Research Assistant, Department of Range Resources

Funded by McIntire-Stennis Research Grants Program, USDA.