Floral Structure ofGarcinia brasiliensisin Relation to Flower Biology and Evolution

Abstract

Garcinia brasiliensis Mart., a species from the Amazon and Atlantic rainforests, is cryptic dioecious because the morphologically perfect flowers are in fact pistillate given the absence of pollen. The flowers present diurnal anthesis, have a sweet and mild scent, and are pollinated by bees in search of the nectar secreted by evident nectaries. The flowers of Clusiaceae bear nectaries of staminodial origin. In Garcinia, the nectaries have been interpreted as being of receptacular origin or as sterile reproductive organs. Our aim in this study was to analyze the nature of the indefinite perianth, the differential development of the androecium in relation to the sexual system, and the origin of the nectaries from the perspective of floral biology and evolution. Floral anatomy and ontogeny were analyzed using both LM and SEM. The species has bracteoles that surround the flower buds. The perianth consists of tepals that are very similar to the bracteoles and that show a centripetal and gradual decrease of mesophyll and cuticle thickness. Developmental irregularities in the anthers lead to a reduction of pollen production in staminate flowers and complete male sterility in pistillate flowers because of peri- and postmeiotic cell degeneration. Both floral forms have nectaries, the origin of which we discuss, leading to hypotheses about their nature.