Resumen

CHAVEZ-GARCIA, Elizabeth  y  VAZQUEZ-SANTANA, Sonia. Floral morphology and embryology of Begonia gracilis (Begoniaceae): their relevance in the monoecy. Bot. sci [online]. 2012, vol.90, n.4, pp.367-380. ISSN 2007-4476.

In this study the development of the male and female flowers of Begonia gracilis is described, using conventional histological and microscopic techniques. The aims were to clarify whether just one whorl is initiated on the meristem or if the flower begins as bisexual and later abortion occurs on androecium or gynoecium. The results show that the unisexuality is established in the floral meristem, because any floral morph develops atrophied organs. The female flowers develop a style that is trifurcate on the tip, forming three dry, bifid, papillate, and helically twisted stigmas. The ovule is crassinucellate, bitegmic and anatropous. The micropyle is amphistome. The male flowers develop free stamens and the gynoecium reminiscences are absent. The microspores tetrads are tetrahedric and isobilateral. The pollen grain is bicellular and tricolporate, with striate and verrugate-striate exine near to the apertures. Based on results we conclude that unisexuality in B. gracilis is established since the floral meristem, likely by mutations in homeotic genes that regulate the development of sexual whorls.

Palabras llave : Begonia; embryology; floral development; monoecy; unisexuality.