Dynamics and precision of thermoregulatory responses of eastern skunk cabbageSymplocarpus foetidus

Abstract

ABSTRACTInflorescences of the arum lilySymplocarpus foetidusare thermogenic and thermoregulatory. The spadix increases respiratory heat production rate as ambient temperature decreases. This study examined the relationships between spadix temperature (Ts), respiration rate () and ambient temperature (Ta) at equilibrium and during transient responses to step changes inTa. Intact inflorescences inside a miniature constant temperature cabinet in the field showed the most precise temperature regulation yet recorded; over a 37.4 °C range inTa(−10.3 to 27.1 °C),Tschanged only 3.5 °C (22.7 to 26.2 °C). Regulated temperatures were not related to spadix size (1.9–7.3 g) or circadian cycle. Dynamic responses to step changes inTainvolved a phasic change inTs, first in the same direction asTa, then reversing at 38.3 min, and finally approaching equilibrium at 87.6 min, on average. Meanwhilechanged in a monotonic curve toward equilibrium. Models revealed that the dynamics of temperature change were inconsistent with simply a physical lag in the system, but involved some form of biochemical regulation, possibly by changes in activity of a rate‐limiting functional protein.