AOBPreview originally published online on August 24, 2007
Annals of Botany 2007 100(4):857-863; doi:10.1093/aob/mcm184
Sympodial Construction of Fibonacci-type Leaf Rosettes in Pinguicula moranensis (Lentibulariaceae)
Institute of Systematic Botany, Uiversity of Zürich, Zollikerstraße 107, CH-8008 Zürich, Switzerland
* For correspondence. E-mail rutishau{at}systbot.unizh.ch
Received: 8 May 2007 Returned for revision: 7 June 2007 Accepted: 2 July 2007 Published electronically: 24 August 2007
Background and Aims: The leaf rosettes of the carnivorous Pinguicula moranensis follow a spiral phyllotaxis approaching a Fibonacci pattern while the stalked flowers arise from extra-axillary sites between the leaves. The organization of this rosette has been discussed by various authors, with various results. The aim of the present study was to clarify the development of the flowering rosettes of this species.
Methods: The formation of the rosettes is shown with the aid of scanning electron microscopy.
Key Results and Conclusions: The scanning electron micrographs show that each flower terminates an article (sympodial unit). The leaves of consecutive articles of such sympodially constructed rosettes are arranged along a spiral Fibonacci pattern (with divergence angles around 137°). This results from homodromy of leaf initiation in consecutive articles with the first leaf (prophyll) of a new article inserted in an obliquely transverse position next to the floral scape that terminates the former article. Sympodial construction of flowering shoots and leaf rosettes is also known from Aloe, Gunnera and Philodendron. As a by-product of this study, the unidirectional development of the Pinguicula flower is confirmed and discussed.
Key words: Article, Fibonacci, flower development, homodromy, leaf initiation, Lentibulariaceae, phyllotaxis, Pinguicula moranensis, sympodial unit