Resumen

VALERIO, Rosanna  y  RAMIREZ, Nelson. Exogamic depression and reproductive biology of Talinum paniculatum (Jacq.) Gaertner (Portulacaceae). Acta Bot. Venez. [online]. 2003, vol.26, n.2, pp.111-124. ISSN 0084-5906.

The reproductive biology of Talinum paniculatum (Portulacaceae), a hermaphrodite herb in a remnant of semideciduous forest in Caracas, Venezuela, was studied. Pollination biology, breeding system, and fruit and seed set were determined. The flowers were actinomorphic, yellowish, small, and live for only four hours. These floral traits were correlated with the pollinator types and sizes, which were represented by bees from different families (Apidae and Halictidae). Pollen load deposited naturally on the stigmas was 2.94 times larger than the number of ovule per flower, and the percentage of germination was 24.9%. The natural production of fruit per flower and seed per ovule was 60.4% and 86.5%, respectively. The lowest level of ovule abortion and the absence of seed abortion contributed to the relatively high level of seed produced per ovule per inflorescence (52.3%). T. paniculatum has a mating system biased toward autogamy, which is correlated with a low polen/ovule ratio (136.1), low pre-(0.39) and post-cigotic (0.03) biomass allocation to male function in flower, and a low pericarp/seed ratio (0.57). The proportion of fruit and seed produced by self-pollination was significantly higher than the proportion produced by cross-pollination which suggest that high levels of autogamy may be associated with outbreeding depression, favouring genotypes highly adapted to small forest fragments located in urban areas.

Palabras clave : Autogamy; outbreeding depression; pollination; bee pollination; fruit set, seed set,; pollen load; melittophily; mirmecochory.