Flowering, pollination, nectar standing crop, and nectaries of Euterpe precatoria (Arecaceae), an Amazonian rain forest palm

Flowering and pollination biology of the monoecious palm Euterpe precatoria was studied in the forest of the ''Reserva Ducke'' near Manaus, Brazil, during two annual flowering periods (middle of October to end of March) between 1991 and 1993. Individuals produced one to four bisexual inflorescences per flowering period. Inflorescences have staminate and pistillate flowers in triads. The anthesis of the whole inflorescence averaged 26 days, with the male phase extending over the first 17 days, followed by six days without any open flowers, and the female phase covering the last three days. The distinct dichogamy of the inflorescence results in obligate outcrossing. The pollen-ovule ratio is high (42000). Both male and female flowers emit an almond oil-like scent and produce nectar in septal nectaries. The concentration and total amount of sugar of the nectar of female flowers (37% and 0.021 mg) were significantly higher than that of male flowers (9% and 0.007 mg). The nectar is hexose-rich and with a moderately high amino acid concentration (68 mu g/ml). Euterpe precatoria seems to be a generally entomophilous palm with a predominance of beetles and bees as potential pollinators. The most constant visitors were beetles of the families Curculionidae, Chrysomelidae, Staphylinidae, and bees of the family Halictidae. The actual composition of the insect spectrum depends on climatic and biotic factors. Additionally, wind pollination may occur. Fruit development lasted four months and ripe fruits are swallowed by toucans who thus disperse the seeds.