Department of Structural and Functional Botany, Faculty Center of Biodiversity, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.
Ann Bot. 2013 Nov;112(8):1577-95. doi: 10.1093/aob/mct156. Epub 2013 Jul 24.
In the Lamiales, indeterminate thyrses (made up of axillary cymes) represent a significant inflorescence type. However, it has been largely overlooked that there occur two types of cymes: (1) ordinary cymes, and (2) 'pair-flowered cymes' (PFCs), with a flower pair (terminal and front flower) topping each cyme unit. PFCs are unique to the Lamiales and their distribution, origin and phylogeny are not well understood.
The Lamiales are screened as to the occurrence of PFCs, ordinary cymes and single flowers (constituting racemic inflorescences).
PFCs are shown to exhibit a considerable morphological and developmental diversity and are documented to occur in four neighbouring taxa of Lamiales: Calceolariaceae, Sanango, Gesneriaceae and Plantaginaceae. They are omnipresent in the Calceolariaceae and almost so in the Gesneriaceae. In the Plantaginaceae, PFCs are restricted to the small sister tribes Russelieae and Cheloneae (while the large remainder has single flowers in the leaf/bract axils; ordinary cymes do not occur). Regarding the origin of PFCs, the inflorescences of the genus Peltanthera (unplaced as to family; sister to Calceolariaceae, Sanango and Gesneriaceae in most molecular phylogenies) support the idea that PFCs have originated from paniculate systems, with the front-flowers representing remnant flowers.
From the exclusive occurrence of PFCs in the Lamiales and the proximity of the respective taxa in molecular phylogenies it may be expected that PFCs have originated once, representing a synapomorphy for this group of taxa and fading out within the Plantaginaceae. However, molecular evidence is ambiguous. Depending on the position of Peltanthera (depending in turn on the kind and number of genes and taxa analysed) a single, a double (the most probable scenario) or a triple origin appears conceivable.
在唇形目中，不定型聚伞花序（由腋生聚伞花序组成）代表着一种重要的花序类型。然而，人们很大程度上忽略了这样一个事实，即存在两种类型的聚伞花序：（1）普通聚伞花序，和（2）“对花聚伞花序”（PFC），每个聚伞花序单元的顶端都有一对花（顶花和前花）。PFC 是唇形目的特有花序，其分布、起源和系统发育尚不清楚。
筛选唇形目植物中 PFC、普通聚伞花序和单花（构成对生花序）的发生情况。
PFC 表现出相当大的形态和发育多样性，并记录在唇形目四个邻近的科中出现：苦苣苔科、Sanango 科、苦苣苔科和车前科。它们在苦苣苔科中普遍存在，在苦苣苔科中几乎如此。在车前科中，PFC 仅限于小的姐妹族 Russelieae 和 Cheloneae（而大的其余部分在叶/苞片腋部有单花；普通聚伞花序不存在）。关于 PFC 的起源，Peltanthera 属的花序（在家族中没有位置；在大多数分子系统发育中与苦苣苔科、Sanango 科和苦苣苔科为姐妹关系）支持这样一种观点，即 PFC 起源于聚伞花序系统，前花代表残余的花。
从 PFC 仅在唇形目中出现以及分子系统发育中各分类群的接近程度可以预期，PFC 起源于一次，代表了这个分类群的一个并系特征，并在车前科中消失。然而，分子证据是模棱两可的。根据 Peltanthera 的位置（反过来取决于分析的基因和分类群的种类和数量），可能出现一次、两次（最可能的情况）或三次起源。
