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Acta Botánica Venezuelica

versión impresa ISSN 0084-5906

Resumen

BARRIOS, Yeni  y  RAMIREZ, Nelson. Outbreeding depression and reproductive biology of Nymphaea ampla (Salisb.) DC. (Nymphaeaceae). Acta Bot. Venez. [online]. 2008, vol.31, n.2, pp.539-556. ISSN 0084-5906.

The reproductive biology of Nymphaea ampla was studied in a herbaceous wetland of the Oriental Coast of Maracaibo Lake, Zulia State, Venezuela. Anthesis is diurnal; flowers remain open from 8:00 until the 15:00 h during 3 to 4 continuous days. The flowers are adicogamous, anther dehiscence occurs in buds and stigmas are receptive during the first day of anthesis. The early dehiscence of anthers and visits by Apis mellifera facilitate self-pollination. The highest activity of bees occurs during the morning, between 9:30 and 11:30 h, with 14,28 visits per flower each 30 min. Pollen load deposited naturally on the stigmas was 5,72 times higher than the number of ovules per flower, and the percentage of germination was 50,23%. Natural fruit set (96,29%),seed set per ovule (98,64%),and the lowest levels of seeds abortion contributed to a high relative fecundity (89%). N. ampla has a mating system with autogamy predominance, which was correlated with a low polen/ovule ratio (195,8), low pre - (0,23) and post-cigotic (0,01) biomass allocation to male function in the flower, and a low pericarp/seed ratio (0,14). The proportion of fruit and seed set via self-fertilization was considerably higher than via outcrossing which suggests that high levels of autogamy may be associated with outbreeding depression, favouring genotypes highly adapted to water bodies where the population remains relatively isolated.

Palabras clave : Autogamy; floral biomass; Nymphaea ampla; outbreeding depression; pollination; reproductive efficiency.

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