Biologia floral e polinização em duas espécies de Boerhavia L. (Nyctaginaceae) em Patos, Paraíba.

Abstract

Boerhavia erecta L. and B. diffusa L. are ruderal herbs, self-compatible with small flowers of funil shape that allow a free access of their nectar many insect visitors. Boerhavia erecta is annual and B. diffusa is perennial, so the reproductive system of them can have differences. In order to check this, observations on their floral morphology and biology, as well as their reproductive system, were made in Patos, PB, Brazil. Both species present a high spontaneous autopollination rate, of near 100%. It was already described the delayed autopollination mechanism in B. diffusa, but it is possible that it happens also at the beginning of anthesis. In 50% of a total of 50 flowers examined at the beginning of anthesis of both species, at least one anther was located very near the stigma, what must contribute for the high autopollination rate. In flowers at the end of anthesis it was observed that in B. diffusa 64% had at least one anther near de stigma, while in B. erecta 48 % of flowers. This result is opposite to the observation of a higher number of pollen grains deposited on the stigma of flowers of B. erecta at the end of anthesis. The observation that the anthers of B. diffusa do not open before anthesis and that its stigma is dry must favor the occurrence of cross fertilization by means of flower visitors.