Valentin-Silva Adriano, Coelho Victor Peçanha de Miranda, Ventrella Marília Contin, Vieira Milene Faria
Departamento de Biologia Vegetal, Universidade Federal de Viçosa (UFV), Av. P.H. Rolfs, s/n, Campus Universitário, CEP 36570-900, Viçosa, Minas Gerais, Brasil.
Am J Bot. 2015 Apr;102(4):626-33. doi: 10.3732/ajb.1400419. Epub 2015 Apr 10.
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.
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.
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.
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.
雌雄异熟是被子植物的一个常见特征，胡椒属植物也包括在内。在该属中，小花在形态上相似，且雄蕊发育不同步。然而，关于柱头可接受期的持续时间以及它是否与花粉释放重叠，尚无相关信息。为了更好地理解维氏胡椒的花功能机制，我们详细描述了四个雄蕊的花粉释放时间、柱头可接受期以及可接受区域的暴露模式。
我们基于化学测试、光学显微镜和扫描电子显微镜分析，对巴西东南部米纳斯吉拉斯州维索萨市半落叶季节性森林中的一个自然种群的植株进行了研究。
记录到不完全的雌蕊先熟现象——一种有利于异花授粉的机制。柱头可接受期较长（14天），柱头乳头的相继暴露和衰老逐渐发生且呈向基方向。在两性花阶段，花粉释放在雌蕊期开始后的2 - 6天开始，花粉平均活力为87.7%。花粉释放持续长达6天，且一次只在一个雄蕊中发生。自花授粉试验中观察到的坐果情况表明其具有自交亲和性。
本文描述了维氏胡椒花中柱头乳头的逐渐相继暴露是柱头可接受期长的机制。花药发育和花粉释放也是相继进行的。这些发现是该属尚未报道的繁殖特征，为未来对其他胡椒属物种花生物学的研究提供了新的视角。
