Gynoecium and fruit development in Oenocarpus mapora Karsten (Arecoideae, Arecaceae)

Abstract

Oenocarpus mapora, commonly known as “bacabinha,” is a culturally and economically important palm in the Amazon region, especially due to its use in the production of “vinho de bacaba,” a traditional beverage made from its fruit pulp. This study describes the ontogenetic development of the gynoecium through to the mature fruit, based on morphological, anatomical, and histochemical analyses. Individuals were monitored in the field over a three-year period, and samples at different floral and fruit developmental stages were examined using light microscopy, scanning electron microscopy, and morphometry. The results confirm that the gynoecium is unilocular, uniovulate, and pseudomonomerous, with no anatomical evidence of carpel fusion—an important insight for the comparative floral morphology of the genus Oenocarpus. Fruits were analyzed in three developmental stages and showed that key structural features, such as mechanical tissues in the pericarp, differentiate early and are maintained throughout maturation, forming a continuous protective matrix around the seed. The fruit is classified as a pyrene-type drupe with a complex (cocosoid-arecoid) endocarp, lignified and composed of fibers adhering to the seed. An elongated embryo with a functional haustorial region was also observed in the mature fruit, evidenced by starch accumulation in the cotyledonary tissues. These early-formed structures reflect adaptive strategies for seed protection and dispersal. The findings offer novel insights into the developmental patterns of the genus and provide valuable information for propagation, cultivation, and conservation strategies involving Amazonian palms.