LOW-TEMPERATURE EXOTHERM MEASUREMENT USING INFRARED THERMOGRAPHY

Infrared thermography was used successfully to measure the exotherm temperatures during freezing of well-watered and drought stressed branches of jojoba [Simmondsia chinensis (Link) Schneider]. The exotherms were visualized easily as color changes on the monitor, while computer analysis software was used to plot the resulting temperature vs. time curves, suggesting that freezing sensitivity of jojoba is governed by supercooling. Each branch froze as a unit, and distinct initiation sites were absent. A second, previously tested method of differential thermal analysis was used simultaneously and confirmed the accuracy of the infrared technique. The actual freezing temperature for well-watered tissue was higher (-8C) than for tissue subjected to drought (-10C).