Kocyan A
Institute of Systematic Botany, Ludwig Maximilians University, Menzinger Strasse 67, D-80638 Munich, Germany.
Ann Bot. 2007 Aug;100(2):241-8. doi: 10.1093/aob/mcm091. Epub 2007 Jun 12.
Individual flowers of the monocot Curculigo racemosa (Hypoxidaceae, Asparagales) are regularly polyandrous. To evaluate the significance of this almost unique character among Asparagales for flower evolution of asparagoid monocots, flowers of C. racemosa were studied comparatively.
Anthetic flowers as well as early floral developmental stages were studied by light and scanning electron microscopy.
Despite the polyandry, floral development is similar to that of other Asparagales with a developmental gradient from adaxial to abaxial. Stamens initiate simultaneously and the diameter of staminal primordia is about half of that in species with six anthers. The number of stamens is not fixed (12-26) and varies within the same inflorescence. Surprisingly, the gynoecium can be four- or six-locular, besides the normal trimerous state.
The discovery of a polyandrous Curculigo reveals plasticity of stamen number at the base of Asparagales. Orchidaceae - sister to all other Asparagales - has a reduced stamen number (three, two or one), whereas in Hypoxidaceae - part of the next diverging clade - either the normal monocot stamen number (six), polyandry (this study) or the loss of three anthers (Pauridia) occurs. However, at present it is impossible to decide whether the flexibility in stamen number is autapomorphic for each group or whether it is a synapomorphy. The small size of stamen primordia of Curculigo is conspicuous. It allows more space for additional androecial primordia. Stamens are initiated as independent organs, and filaments are not in bundles, hence C. racemosa is not secondarily polyandrous as may be the case in the distantly related Gethyllis of asparagoid Amaryllidaceae. The increase in carpel number is a rare phenomenon in angiosperms. A possible explanation for the polyandry of C. racemosa is that it is a natural SUPERMAN-deficient mutant, which shows an increase of stamens, or ULTRAPETALA or CARPEL FACTORY mutants, which are polyandrous and changed in carpel number.
单子叶植物仙茅（仙茅科，天门冬目）的单朵花通常是多雄蕊的。为了评估天门冬目中这一几乎独特的特征对天门冬类单子叶植物花进化的意义，对仙茅的花进行了比较研究。
通过光学显微镜和扫描电子显微镜研究开花期的花以及早期花发育阶段。
尽管有多雄蕊现象，但花的发育与其他天门冬目植物相似，存在从近轴到远轴的发育梯度。雄蕊同时起始，雄蕊原基的直径约为有六个花药的物种的一半。雄蕊的数量不固定（12 - 26个），且在同一花序内有所变化。令人惊讶的是，除了正常的三轮状态外，雌蕊可以是四室或六室的。
多雄蕊仙茅的发现揭示了天门冬目基部雄蕊数量的可塑性。兰科是所有其他天门冬目的姐妹群，其雄蕊数量减少（三个、两个或一个），而在仙茅科（下一个分化分支的一部分）中，要么是正常单子叶植物的雄蕊数量（六个），要么是多雄蕊（本研究），要么是三个花药缺失（苞叶仙茅属）。然而，目前无法确定雄蕊数量的灵活性是每个类群的自近裔性状还是共有衍征。仙茅雄蕊原基的小尺寸很明显。这为额外的雄蕊原基留出了更多空间。雄蕊作为独立器官起始，花丝不成束，因此仙茅不像天门冬类石蒜科的远亲盖氏花属那样是次生多雄蕊的。心皮数量增加在被子植物中是一种罕见现象。仙茅多雄蕊的一种可能解释是它是一种天然的缺乏SUPERMAN的突变体，表现为雄蕊增加，或者是ULTRAPETALA或CARPEL FACTORY突变体，它们多雄蕊且心皮数量发生了变化。
