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Free keywords:
Rafflesia; endothermy; CO2; volatile compounds; respiration;
mimicry; pollination; FLUENT (TM)
Cyanide-insensitive respiration; alternative oxidase; soybean
mitochondria; temperature; plants; pollination; attractant;
cytochrome; pathways; araceae
Abstract:
The giant flowers of the parasitic Rafflesia occur in the shade of the forest understorey. They present several characteristics in common with the related species, Rhizanthes lowii, which is a strongly endothermic flower. The possible existence of endothermy in Rafflesia tuan-mudae was investigated here. The internal and surface temperature of the flowers were continuously monitored with fine thermocouples while radiation fluxes and microclimatic variables were recorded. A computational fluid dynamic model was used to predict the concentrations of CO2 inside the diaphragm of the flower. It was found that the internal parts of the flower were maintained a few degrees (1-6 K) above air temperature. It was not possible to account for this temperature rise without postulating a significant internal source of heat. It was concluded that R, tuan-mudae is an endothermic flower that generates a maximum of 50-60 W m(-2) of heat in the centre of the column. The possible role of endothermy, CO2 and volatiles as elements in the mimicry of the flower to attract pollinating blowflies is discussed and compared with the related species Rhizanthes lowii.
