Thermogenesis in three Philodendron species (Araceae) of French Guiana

Spadix temperature was measured in three species of Philodendron: P. acutat um Schott, P. pedatum (Hooker) Kunth, and P. solimoesense A. C. Smith. Thes e species showed two different patterns of spadix temperature during their flowering cycle. In P. acutatum and P. pedatum (subgenus Philodendron), the spadix warmed up twice during the beginning of each flowering night with a temperature not significantly different from that of the ambient air betwe en the two peaks. In P. solimoesense (subgenus Meconostigma), the spadix te mperature rose to 14 degrees C above that of the ambient air during the fir st night, then it progressively cooled down but remained 3-6 degrees C abov e the ambient air temperature. We propose that the heat production and the spadix temperature patterns observed may reflect different physiological pr ocesses and have a taxonomic significance in the genus Philodendron.