Dynamics and precision of thermoregulatory responses of eastern skunk cabbage Symplocarpus foetidus

ABSTRACT Inflorescences of the arum lily Symplocarpus foetidus are 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 in Ta. 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 in Ta (−10.3 to 27.1 °C), Ts changed 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 in Ta involved a phasic change in Ts, first in the same direction as Ta, then reversing at 38.3 min, and finally approaching equilibrium at 87.6 min, on average. Meanwhile changed 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.