Authors: Roger S Seymour Gemma Lindshau Kikukatsu Ito
Publish Date: 2010/03/11
Volume: 231, Issue: 6, Pages: 1291-1300
Abstract
The flowers of several families of seed plants warm themselves when they bloom In some species thermogenesis is regulated increasing the rate of respiration at lower ambient temperature T a to maintain a somewhat stable floral temperature T f The precision of this regulation is usually measured by plotting T f over T a However such measurements are influenced by environmental conditions including wind speed humidity radiation etc This study eliminates environmental effects by experimentally ‘clamping’ T f at constant selected levels and then measuring stabilized respiration rate Regulating flowers show decreasing respiration with rising T f Q 10 1 Q 10 therefore becomes a measure of the biochemical ‘precision’ of temperature regulation lower Q 10 values indicate greater sensitivity of respiration to T f and a narrower range of regulated temperatures At the lower end of the regulated range respiration is maximal and further decreases in floral temperature cause heat production to diminish Below a certain tissue temperature ‘switching temperature’ heat loss always exceeds heat production so thermoregulation becomes impossible This study compared three species of thermoregulatory flowers with distinct values of precision and switching temperature Precision was highest in Nelumbo nucifera Q 10 = 016 moderate in Symplocarpus renifolius Q 10 = 048 and low in Dracunculus vulgaris Q 10 = 074 Switching temperatures were approximately 30 15 and 20°C respectively There were no relationships between precision switching temperature or maximum respiration rate High precision reveals a powerful inhibitory mechanism that overwhelms the tendency of temperature to increase respiration Variability in the shape and position of the respiration–temperature curves must be accounted for in any explanation of the control of respiration in thermoregulatory flowersThis project was supported by the Australian Research Council DP 0771854 We appreciate the logistical help of Morio Kato at the Fujine skunk cabbage park Stergios Pirintsos of the University of Crete and staff at the Adelaide Botanic Garden Doug Butler constructed the temperature control circuits Ingolf Lamprecht Casey Mueller and Robin Seymour assisted in the field
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