Narbona Eduardo, Ortiz Pedro Luis, Arista Montserrat
Departamento de Biología Molecular e Ingeniería Bioquímica, Universidad Pablo de Olavide, Ctra. Utrera Km 1, 41013 Sevilla, Spain.
Ann Bot. 2008 Apr;101(5):717-26. doi: 10.1093/aob/mcn011. Epub 2008 Feb 4.
In andromonoecious taxa with separate floral types along the inflorescence, architectural or plastic effects can simulate floral sexual dimorphism. Both the primary and secondary sexual characteristics of the cyathia of the protogynous andromonoecious species Euphorbia nicaeensis were analysed according to their sex and arrangement on the inflorescence.
The production of male and hermaphrodite cyathia at each inflorescence level was surveyed in two natural populations. The longevity, size, pollen production and viability, and nectar secretion of both types of cyathia were checked between inflorescence levels and between sexes at the only level at which they occur together. This sampling method makes it possible to know whether differences between cyathia types are based on sex or are attributable to inflorescence development.
Male cyathia were produced predominantly at the first and second inflorescence levels, whereas at levels 3-5, the cyathia were almost exclusively hermaphrodite. Viable pollen production by male cyathia at the second inflorescence level was higher than that of hermaphrodite cyathia at the third level but, when males and hermaphrodites at the same level were compared, their pollen production was similar. Male and hermaphrodite cyathia were similar in size, irrespective of the inflorescence level, although the exclusively hermaphrodite cyathia of the last level were smaller. Both cyathium types produced similar amounts of sugar. However, male cyathia produced nectar during their whole lifespans, whereas hermaphrodites produced it exclusively during their male phase. Moreover, the nectary activity of male cyathia started earlier in the day than that of hermaphrodites.
An apparent floral dimorphism exists in the primary sexual characteristics of Euphorbia nicaeensis because differences in pollen production between cyathium types are due to theirs positions. Similarly, differences affecting most secondary sexual characteristics are only apparent between the two cyathium types. However, E. nicaeensis shows a true but slight floral dimorphism in some of the secondary sex characters related to nectar secretion. The lack of nectar production by the female phase of the hermaphrodite cyathia of E. nicaeensis indicates that this is a deceit-pollinated species.
在具有沿花序分化的不同花型的雄花两性花同株类群中，结构或可塑性效应可模拟花的性二态性。根据其性别及在花序上的排列方式，对雌花先熟的雄花两性花同株物种滨海大戟的杯状聚伞花序的主要和次要性特征进行了分析。
在两个自然种群中调查了每个花序水平上雄花和两性花杯状聚伞花序的产生情况。在花序水平之间以及两种类型的杯状聚伞花序共同出现的唯一水平上，检查了两性杯状聚伞花序的寿命、大小、花粉产量和活力以及花蜜分泌情况。这种采样方法能够了解杯状聚伞花序类型之间的差异是基于性别还是归因于花序发育。
雄花杯状聚伞花序主要在第一和第二个花序水平产生，而在第3 - 5个水平，杯状聚伞花序几乎全是两性的。第二个花序水平的雄花杯状聚伞花序产生的可育花粉量高于第三个水平的两性花杯状聚伞花序，但当比较同一水平的雄花和两性花时，它们的花粉产量相似。无论花序水平如何，雄花和两性花杯状聚伞花序大小相似，尽管最后一个水平的纯两性花杯状聚伞花序较小。两种类型的杯状聚伞花序产生的糖分含量相似。然而，雄花杯状聚伞花序在其整个寿命期内都分泌花蜜，而两性花仅在其雄花阶段分泌花蜜。此外，雄花杯状聚伞花序的蜜腺活动在一天中开始得比两性花早。
滨海大戟在主要性特征方面存在明显的花二态性，因为杯状聚伞花序类型之间的花粉产量差异是由于它们的位置不同。同样，影响大多数次要性特征的差异仅在两种杯状聚伞花序类型之间明显。然而，滨海大戟在一些与花蜜分泌相关的次要性特征方面表现出真正但轻微的花二态性。滨海大戟两性花杯状聚伞花序的雌花阶段不分泌花蜜，这表明它是一种欺骗性传粉的物种。
