CALORIMETRIC DETERMINATION OF TISSUE RESPONSES TO THERMAL EXTREMES AS A FUNCTION OF TIME AND TEMPERATURE

Calorimetric procedures have been developed for defining the effects of high and low temperature stresses on the metabolic activities of plant tissues and cell cultures. Inactivation of metabolism was shown to be a complex function of both temperature and time of exposure to thermal extremes. Equations developed to fit the activity loss data can be used to (a) predict residual activity after any regime of thermal exposure, (b) select plant cultivars with differences in thermal stabilities, and (c) provide models for the nature of responses associated with thermal inactivation. Equations describing thermal inactivation at both high and low temperature ranges have a form which suggests a second or higher order dependence on temperature. Results on tomato leaflets and cells are used to illustrate the applicability of the method. © 1990.