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

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>Inflorescences of the arum lily<jats:italic>Symplocarpus foetidus</jats:italic>are thermogenic and thermoregulatory. The spadix increases respiratory heat production rate as ambient temperature decreases. This study examined the relationships between spadix temperature (<jats:italic>T</jats:italic><jats:sub>s</jats:sub>), respiration rate (<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/PCE_1206_mu1.gif" xlink:title="inline image" />) and ambient temperature (<jats:italic>T</jats:italic><jats:sub>a</jats:sub>) at equilibrium and during transient responses to step changes in<jats:italic>T</jats:italic><jats:sub>a</jats:sub>. 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<jats:italic>T</jats:italic><jats:sub>a</jats:sub>(−10.3 to 27.1 °C),<jats:italic>T</jats:italic><jats:sub>s</jats:sub>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<jats:italic>T</jats:italic><jats:sub>a</jats:sub>involved a phasic change in<jats:italic>T</jats:italic><jats:sub>s</jats:sub>, first in the same direction as<jats:italic>T</jats:italic><jats:sub>a</jats:sub>, then reversing at 38.3 min, and finally approaching equilibrium at 87.6 min, on average. Meanwhile<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/PCE_1206_mu1.gif" xlink:title="inline image" />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.</jats:p>