CHILLING-INDUCED HEAT EVOLUTION IN PLANTS

Increases in respiration, particularly via the alternative pathway, ar e observed in response to chilling. These increases result in increase d heat evolution. We have measured increases in heat evolution in resp onse to chilling in a number of plant species using a microcalorimeter . After 8 h of exposure to 8 degrees C, heat evolution in a variety of chilling-sensitive species increased 47 to 98%. No increase in heat e volution was seen with the extremely chilling-sensitive ornamental Epi scia cupreata Hook. Heat evolution increased only 7 to 22% in the chil ling-resistant species. Increases in heat evolution were observed when plants were chilled in constant light or in the dark, but not when pl ants were chilled at high humidity. Increased capacity to produce resp iratory heat after exposure to chilling temperatures may contribute to the cold-acclimation process.