Sympodial construction of Fibonacci-type leaf rosettes in Pinguicula moranensis (Lentibulariaceae).
OBJECTIVE
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.


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 degrees). 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.
Grob
Valentin
V
Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland.
Pfeifer
Evelin
E
Rutishauser
Rolf
R
D019521:Body Patterning; D035264:Flowers / Q000254:growth & development / Q000648:ultrastructure; D019684:Magnoliopsida / Q000254:growth & development / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D018515:Plant Leaves / Q000254:growth & development / Q000648:ultrastructure