Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK.
Am J Bot. 2007 Oct;94(10):1612-29. doi: 10.3732/ajb.94.10.1612.
We present a detailed comparative ontogenetic analysis of pseudanthia of representatives of all three subtribes of Euphorbieae (Euphorbiinae, Neoguillauminiinae, Anthosteminae) in order to clarify their homologies and interpretation. The cyathium of Euphorbia and its allies (subtribe Euphorbiinae) closely resembles a bisexual flower but is traditionally interpreted as an inflorescence bearing clusters of highly reduced male flowers surrounding a single terminal female flower. Previously unreported characters are (1) male flowers formed one above the other in the male inflorescences of some Euphorbiinae, (2) late-developing perianthlike structures in some male flowers of Neoguillauminia cleopatra, (3) evidence for a bracteate origin of the female perianth in Anthosteminae and Neoguillauminiinae, and (4) spatiotemporally independent formation of abscission zone and perianth. Indistinct boundaries between inflorescence, flower, and floral organs demonstrate that defining the cyathium neither as an inflorescence nor as a flower is entirely satisfactory and indicate a "hybrid" flower/inflorescence nature of the cyathium. Based on our current knowledge and the existing phylogenetic context, it is most parsimonious to suggest that the cyathium evolved from a determinate thyrse with a terminal female flower surrounded by dichasial male partial inflorescences. We speculate that the cyathium was formed because of strong condensation and possible overlap between expression zones of regulatory genes.
我们对 Euphorbieae（Euphorbiinae、Neoguillauminiinae、Anthosteminae）三个亚族的代表植物的假两性花进行了详细的比较个体发生分析，以阐明它们的同源性和解释。大戟属及其近缘植物（Euphorbiinae 亚族）的杯状花序非常类似于两性花，但传统上被解释为带有一簇高度退化的雄花围绕单个顶生雌花的花序。以前未报道的特征是：（1）在一些 Euphorbiinae 的雄性花序中，雄花一个接一个地形成；（2）在 Neoguillauminia cleopatra 的一些雄花中，后期发育的类似花被的结构；（3）在 Anthosteminae 和 Neoguillauminiinae 中，雌性花被具有苞片起源的证据；（4）离层和花被的时空独立形成。花序、花和花器官之间的不明显界限表明，将杯状花序既定义为花序又定义为花都不完全令人满意，并表明杯状花序具有“杂种”花/花序性质。根据我们目前的知识和现有的系统发育背景，最简约的假设是，杯状花序是从具有顶生雌性花的有限聚伞花序演化而来，周围是二歧的雄性部分花序。我们推测，杯状花序的形成是由于调控基因表达区的强烈凝聚和可能重叠。
