title: Timing of pollen release and stigma receptivity period of Piper vicosanum: New insights into sexual reproduction of the genus.
abstract: OBJECTIVE
  Dichogamy is a common characteristic among angiosperms, including Piper species. In this genus, the tiny flowers are morphologically similar and have an asynchronous stamen development. However, there is no information on the duration of stigma receptivity and whether it overlaps with pollen release. To better understand mechanisms of floral function in Piper vicosanum, we provide a detailed characterization of the timing of pollen release from the four stamens and the period of stigma receptivity and exposure mode of the receptive areas.
  
  
  METHODS
  We investigated plants of a natural population in a semideciduous seasonal forest (Viçosa, Minas Gerais State, southeastern Brazil), based on chemical tests, light microscopy, and scanning electron microscopy analyses.
  
  
  RESULTS
  Incomplete protogyny-a mechanism that favors outcrossing-was recorded. The period of stigma receptivity was long (14 d), and the sequential exposure and senescence of stigmatic papillae occurred gradually and in a basipetal direction. Pollen release began 2-6 d after the beginning of the pistillate phase, with an average pollen viability of 87.7%, during the bisexual flower phase. Pollen was released for up to 6 d and occurred in one stamen at a time. The fruit set observed in tests of self-pollination indicated self-compatibility.
  
  
  CONCLUSIONS
  The gradual and sequential exposure of stigmatic papillae in P. vicosanum flowers is described here as the mechanism for the long duration of receptivity. Anther development and pollen release were also sequential. These findings are yet unreported reproductive characteristics of the genus and offer new perspectives for future studies on the floral biology of other Piper species.
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa (UFV), Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-900, Viçosa, Minas Gerais, Brasil.
authors: Adriano
authors: A
authors: Valentin-Silva
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa (UFV), Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-900, Viçosa, Minas Gerais, Brasil.
authors: Victor Peçanha de Miranda
authors: VP
authors: Coelho
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa (UFV), Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-900, Viçosa, Minas Gerais, Brasil.
authors: Marília Contin
authors: MC
authors: Ventrella
authors: Departamento de Biologia Vegetal, Universidade Federal de Viçosa (UFV), Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-900, Viçosa, Minas Gerais, Brasil.
authors: Milene Faria
authors: MF
authors: Vieira
mesh_terms: D001938:Brazil; D035264:Flowers / Q000033:anatomy & histology / Q000502:physiology*; D031701:Piper / Q000502:physiology*; D011058:Pollen / Q000502:physiology*; D054817:Pollination; D012098:Reproduction
keywords: asynchronous pollen release; incomplete protogyny; self-compatibility; stigmatic exposure