XVI International Botanical Congess

The protogynous inflorescences of Symplocarpus foetidus regulate spadix temperature (Ts) between 16-26C at ambient temperatures (Ta) of 3-24C in Eastern Canada. Continuous records of oxygen consumption and carbon dioxide production showed that respiration was inversely related to both Ts and Ta. When Ta dropped below 3C, however, many spadices abruptly stopped heating, and Ts switched to near freezing. They quickly switched to the warm state again, if Ta warmed above 3C. Switching temperature was related to the balance between heat production and heat loss that tended to produce stable equilibria at either high or low Ts, accounting for an observed bimodal distribution of Ts in the field.