Thermogenesis and flowering biology of Colocasia gigantea , Araceae

International audienceThe thermogenesis and flowering biology of Colocasia gigantea (Blume) Hook. f. were studied from December 2005 to February 2006 on Espiritu Santo, Vanuatu (South Pacific). Endogenous thermogenesis was measured in two ways: (1) continuously over 5-day periods, and (2) over 3 h during maximum heating. The study showed that heat was generated by the male part of the spadix and probably the lower zone of the sterile region. The temperatures of the male part peaked twice: (1) between 0625 and 0640 (during the female phase) and (2) 24 h later (during the male phase). The average maximum temperature was 42.25 ± 0.14°C during the female phase (16.63°C above the ambient temperature) and 35.14 ± 0.22°C during the male phase (10.61°C above the ambient temperature). In the lower zone of the sterile region, thermogenesis was documented only during the female phase. The average maximum temperature was 35.44 ± 0.41°C (9.82°C above the ambient temperature). Thermogenic heating appeared to be closely associated with the activities of pollinating insects

Respiration and thermogenesis by cones of the Australian cycad Macrozamia machinii

The definitive version is available at www.blackwell-synergy.com1. While cycads are often considered to be wind-pollinated, it is now clear that insects are pollen vectors in many species. This study addresses the role of thermogenesis in pollination biology of the dioecious cycad Macrozamia machinii P.I. Forster & D.L. Jones . 2. The patterns of thermogenesis in intact male and female cones were assessed with thermometry and respirometry throughout the pollination period in the field. 3. Thermogenic episodes in male cones occurred from about 17.00–00.00 h on successive evenings, in association with dehiscence of sporangia and presence of their pollinating weevils ( Tranes sp.). 4. Temperatures of the 167 g male cones rose ≈ 6 ° C above ambient, and mean rate of oxygen consumption peaked at 7·7 μ mol s − 1 (3·6 W). Regulation of male cone temperature was not evident, and thermogenesis of female cones was insignificant. 5. Male cones probably heat to augment scent production and enhance weevil activity, including mating and egg-laying, but female cones may benefit from reduced visitation and freedom from damage by weevil larvae. Male cones may be sacrificial in providing the reward to the pollinators while the female cones are safeguarded.R. S. Seymour, I. Terry and R. B. Roeme