Respiration of thermogenic inflorescences of skunk cabbage Symplocarpus renifolius in heliox

4 years ago

Respiration of thermogenic inflorescences of skunk cabbage Symplocarpus renifolius in heliox

Roger S. Seymour, Yui Umekawa, Kikukatsu Ito

The respiration rate of the thermogenic inflorescences of Japanese skunk cabbage Symplocarpus renifolius can reach 300 nmol s-1 g-1, which is sufficient to raise spadix temperature (Ts) up to 15°C above ambient air temperature (Ta). Respiration rate is inversely related to Ta, such that the Ts achieves a degree of independence from Ta, an effect known as temperature regulation. Here, we measure oxygen consumption rate (M. o2) in air (21% O2 in mainly N2) and in heliox (21% O2 in He) to investigate the diffusive conductance of the network of gas-filled spaces and the thermoregulatory response. When Ts was clamped at 15°C, the temperature that produces maximal M. o2 in this species, exposure to high diffusivity heliox increased mean M. o2 significantly from 137 ± 17 to 202 ± 43 nmol s-1 g-1 FW, indicating that respiration in air is normally limited by diffusion in the gas phase and some mitochondria are unsaturated. When Ta was clamped at 15°C and Ts was allowed to vary, exposure to heliox reduced Ts 1°C and increased M. o2 significantly from 116 ± 10 to 137 ± 19 nmol s-1 g-1, indicating that enhanced heat loss by conduction and convection can elicit the thermoregulatory response.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/pce.13097