Geonoma brevispatha Barb. Rodr. is a shrub palm with clonal growth and restricted to marshy lands along banks of rivers and streams. The object of this work is to describe its reproductive biology in an area of floodable riparian forest, in Uberlândia, MG. The study was carried out from April 2004 to December 2005. The species flowered from April to August of 2004. The greater production of fruit occurred between October and December. The flowers present a violaceous coloring; they are diclinous, protanderous in the same flower head, emit a strong scent and open about 8:00 in the morning. They are arranged in the rachilla in triads (two lateral staminate flowers and a central pistillate). Only the pistillate flower had nectar. It is smaller than the staminate and its life span is between two and four days and that of the staminate is one day. The rate for pollen viability for flowers in pre-anthesis was 84.3% and 95.9% for recently opened flowers. The stigmatic receptivity occurs as from the bud stage. The average number of flowers per flower head was 2,192.8 ± 1,184.1 staminate and 1,129.5 ± 571.4 pistillate. There was no overlapping between the opening of the staminate and pistillate flowers in the same flower head and neither in the same individual, and so occurring functional dioecy. Apomixis did not occur and therefore the sexual reproduction of the species depends on cross pollination. The main effective pollinators were flies of the Muscidae e Sarcophagidae families. Bees and beetles were considered as occasional pollinators.
floral biology; Geonoma brevispatha; myophily; pollination; reproductive system
