Respiration of thermogenic inflorescences of skunk cabbage Symplocarpus renifolius in heliox |
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| Authors: | Roger S Seymour Kikukatsu Ito Yui Umekawa |
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| Affiliation: | 1. School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia;2. Cryobiofrontier Research Center, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan |
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| Abstract: | 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 (?o 2) 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 ?o 2 in this species, exposure to high diffusivity heliox increased mean ?o 2 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 ?o 2 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. |
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| Keywords: | diffusion flower gas conductance heliox inflorescence oxygen consumption respiration thermogenesis |
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