(437) Application of Differential Thermal Analysis to Study Freezing Behavior and Supercooling in Plants

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  • 1 The Morton Arboretum, Urban Horticulture Research Lab., Lisle, IL, 60532

Survival of temperate plants is often dependent upon their resistance or ability to tolerate low temperatures. Differential thermal analysis (DTA) has been employed to explore the freezing characteristics of plants and other organisms. However, there appears to be a need for further studies to better understand the physiology of freezing and its significance as related to supercooling. Methods employing thermocouples, differential wiring, and digital data acquisition boards allow detection of very small exothermic responses (about 0.025 °C). This study reports on techniques and apparatus for using DTA as well as results obtained on various plant tissues. When Fagus grandifolia (American beech) was compared to Fagus sylvatica (European beech), it exhibited both a lower high temperature (HT) and low temperature (LT) exotherm that correlated with lower stem tissue water content during September to May. The DTA on Acer pseudosieboldianum (Korean maple) from a higher elevation showed lower LT exotherm in stem tissues when compared to lower elevation samples. Incubation of Cornus amomum, Cornus obliqua, and Larix gmelinii var. olgensis stem tissue with d-H20 for 20 hours resulted in an induction of LT exotherm at a significantly higher temperature than a normal LT exotherm. This phenomenon was attributed to the bark tissue in Larix gmelinii var. olgensis. Sucrose and glycerol exotherm profiles exhibited lower exotherm temperatures. In a companion study, we used thermal analysis (non-differential) to study supercooling in [Homadaula anisocentra(Mimosa webworm)] and a single exotherm event was detected. New technology provides a great deal of flexibility in the method of evaluation of exothermic responses in plants and other organisms.

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