title: Contrasting models of the female reproductive tract in four o'clocks (Nyctaginaceae).
abstract: •
  
  
  OBJECTIVE
  In angiosperms, several carpel tissues are specialized to facilitate pollen-tube elongation to achieve fertilization. We evaluated the possible evolutionary pathways of the diverse female reproductive tracts in Nyctaginaceae.•
  
  
  METHODS
  We studied the anatomy of a range of species representing different tribes, using light, fluorescence, scanning electron, and transmission electron microscopy.•
  
  
  RESULTS
  Stigmas have multicellular, multiseriate papillae, except for Boerhavia diffusa with unicellular papillae. The styles are solid, with a strand of transmitting tissue linking the stigma with the ventral ovary wall. In Allionia, Boerhavia, and Mirabilis, the transmitting tissue branches into two independent tracts at the base of the ovary and continues across the lateral margins of the funicle to the micropyle; it is composed of cells with thick walls surrounded by abundant extracellular matrix. Bougainvillea, Pisonia, and Pisoniella have a diffuse transmitting tissue and an obturator, a proliferation of cells covered by a layer of secretory papillae that encloses the funicle, placenta, and ventral wall of the gynoecium and contacts with the micropyle.•
  
  
  CONCLUSIONS
  We propose two models of female reproductive tract, (A) one in which an obturator is absent and the transmitting tissue is compact and branched and (B) one in which an obturator is present and the transmitting tissue is diffuse. On the basis of character optimization, we hypothesize that model B represents the ancestral (plesiomorphic) condition in the family and model A originated once during evolution, within the tribe Nyctagineae.
authors.affiliation: Instituto Multidisciplinario de Biología Vegetal, CONICET-Universidad Nacional de Córdoba, Casilla de Correo 495, 5000, Córdoba, Argentina.
authors.forename: María J
authors.initials: MJ
authors.lastname: Nores
authors.affiliation: Instituto Multidisciplinario de Biología Vegetal, CONICET-Universidad Nacional de Córdoba, Casilla de Correo 495, 5000, Córdoba, Argentina.
authors.forename: Hernán A
authors.initials: HA
authors.lastname: López
authors.affiliation: Instituto Multidisciplinario de Biología Vegetal, CONICET-Universidad Nacional de Córdoba, Casilla de Correo 495, 5000, Córdoba, Argentina.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Anton
authors.affiliation: Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, UK.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Rudall
mesh_terms: D005075:Biological Evolution; D016000:Cluster Analysis; D005306:Fertilization; D035264:Flowers / Q000235:genetics / Q000648:ultrastructure*; D008961:Models, Structural; D039281:Nyctaginaceae / Q000235:genetics / Q000648:ultrastructure*; D053205:Pollen Tube / Q000235:genetics / Q000648:ultrastructure; D054817:Pollination; D012098:Reproduction; D013045:Species Specificity
keywords: Nyctaginaceae; female reproductive tract; obturator; pollen-tube pathway; transmitting tissue