Thermogenesis in male cones of four cycad species

摘要

Temperature of sporophylls from excised male cones of three species from the Zamiaceae family (Ceratozamia miqueliana, Zamia fairchildiana, and Zamia pumila) and from one species from the Cycadaceae family(Cycas siamensis) was recorded over several days in an environmental chamber. Each species exhibited a different temperature profile. C. miqueliana and Z. fairchildiana were highly thermogenic, whereas C. siamensis and Z. pumila were weakly thermogenic. In C. miqueliana, the temperature of one sporophyll rose to 10 degrees C above ambient while other sporophylls on the same cone only reached temperatures of 0-3 degrees C above ambient. Temperature rates among the different cones varied between approximate to 0.01 and 0.09 degrees C/h. Temperature profiles of sporophylls of Z. fairchildiana and C. siamensis were reported for the first time. Studies of thermogenesis of single sporophylls in a controlled environment provide accurate temperature measurements. Furthermore, sporophylls can be exposed to different environments and thus improve our understanding of the mechanism of thermogenesis in vivo.